WorldWideScience

Sample records for net nitrification rates

  1. In situ net N mineralisation and nitrification under organic and conventionally managed olive oil orchards

    DEFF Research Database (Denmark)

    Gomez Muñoz, Beatriz; Hinojosa, M. B.; García-Ruiz, R.

    2015-01-01

    Olive oil orchard occupies a great percentage of the cropland in southern Spain. Thus, changes in nitrogen (N) fertilization might have a great effect on N dynamics at least at regional scale, which should be investigated for a sustainable N fertilization program. In situ net N mineralization (NM......) and nitrification (NN) were investigated during a year in comparable organic (OR) and conventional (CV) olive oil orchards of two locations differing their N input. Soil samples were collected in two soil positions (under and between trees canopy) and both buried-bags and soil core techniques were used to quantify...... soil TN. Soil TN and PMN explained together a 50 % of the variability in soil N availability, which suggests that these two variables are good predictors of the potential of a soil to provide available N. The highest rates of soil N availability were found in spring, when olive tree demand for N...

  2. Decreased Soil Nitrification Rate with Addition of Biochar to Acid Soils

    Institute of Scientific and Technical Information of China (English)

    Shiyu LI; Xiangshu DONG; Dandan LIU; Li LIU; Feifei HE

    2017-01-01

    This study was conducted to investigate the effects of mixed biochar on the nitrification rate in acidic soils. A 15N tracer experiment with (15NH4)2SO4 was conducted to determine the nitrification rates of 4 acidic agricultural soils with pH 4.03-6.02in Yunnan Province, Southern China. The accumulation of 15N-NO3 - and nitrification rates decreased with the addition of biochar at the end of incubation, suggesting that biochar could be a nitrification inhibitor in acidic fertilized soil. Nitrification rates in soil with pH 4.03 were evidently lower than those in soil with pH 4.81 -6.02 with or without biochar. Decreased nitrification rates were detected in the acidic soils with biochar. Soil pH controlled nitrification more than biochar in certain strongly acidic soils.

  3. Soil properties associated with net nitrification following watershed conversion with Appalachian hardwoods to Norway spruce

    Science.gov (United States)

    Charlene N. Kelly; Stephen H. Schoenholtz; Mary Beth Adams

    2011-01-01

    Nitrate (NO3-N) in soil solution and streamwater can be an important vector of nitrogen (N) loss from forested watersheds, and nitrification is associated with negative consequences of soil acidification and eutrophication of aquatic ecosystems. The purpose of this study was to identify vegetation-mediated soil properties that may control...

  4. A cross-site comparison of factors influencing soil nitrification rates in northeastern USA forested watersheds

    Science.gov (United States)

    Ross, D.S.; Wemple, B.C.; Jamison, A.E.; Fredriksen, G.; Shanley, J.B.; Lawrence, G.B.; Bailey, S.W.; Campbell, J.L.

    2009-01-01

    Elevated N deposition is continuing on many forested landscapes around the world and our understanding of ecosystem response is incomplete. Soil processes, especially nitrification, are critical. Many studies of soil N transformations have focused on identifying relationships within a single watershed but these results are often not transferable. We studied 10 small forested research watersheds in the northeastern USA to determine if there were common factors related to soil ammonification and nitrification. Vegetation varied between mixed northern hardwoods and mixed conifers. Watershed surface soils (Oa or A horizons) were sampled at grid or transect points and analyzed for a suite of chemical characteristics. At each sampling point, vegetation and topographic metrics (field and GIS-based) were also obtained. Results were examined by watershed averages (n = 10), seasonal/watershed averages (n = 28), and individual sampling points (n = 608). Using both linear and tree regression techniques, the proportion of conifer species was the single best predictor of nitrification rates, with lower rates at higher conifer dominance. Similar to other studies, the soil C/N ratio was also a good predictor and was well correlated with conifer dominance. Unlike other studies, the presence of Acer saccharum was not by itself a strong predictor, but was when combined with the presence of Betula alleghaniensis. Topographic metrics (slope, aspect, relative elevation, and the topographic index) were not related to N transformation rates across the watersheds. Although found to be significant in other studies, neither soil pH, Ca nor Al was related to nitrification. Results showed a strong relationship between dominant vegetation, soil C, and soil C/N. ?? 2008 Springer Science+Business Media, LLC.

  5. Impact of water boundary layer diffusion on the nitrification rate of submerged biofilter elements from a recirculating aquaculture system

    DEFF Research Database (Denmark)

    Prehn, Jonas; Waul, Christopher Kevin; Pedersen, Lars-Flemming

    2012-01-01

    Total ammonia nitrogen (TAN) removal by microbial nitrification is an essential process in recirculating aquaculture systems (RAS). In order to protect the aquatic environment and fish health, it is important to be able to predict the nitrification rates in RAS’s. The aim of this study was to det...... biofilters. The results may thus have practical implications in relation to the design, operational strategy of RAS biofilters and how to optimize TAN removal in fixed film biofilter systems......Total ammonia nitrogen (TAN) removal by microbial nitrification is an essential process in recirculating aquaculture systems (RAS). In order to protect the aquatic environment and fish health, it is important to be able to predict the nitrification rates in RAS’s. The aim of this study...

  6. Using paired in situ high frequency nitrate measurements to better understand controls on nitrate concentrations and estimate nitrification rates in a wastewater-impacted river

    Science.gov (United States)

    Kraus, Tamara; O'Donnell, Katy; Downing, Bryan D.; Burau, Jon R.; Bergamaschi, Brian

    2017-01-01

    We used paired continuous nitrate ( ) measurements along a tidally affected river receiving wastewater discharge rich in ammonium ( ) to quantify rates of change in  concentration ( ) and estimate nitrification rates.  sensors were deployed 30 km apart in the Sacramento River, California (USA), with the upstream station located immediately above the regional wastewater treatment plant (WWTP). We used a travel time model to track water transit between the stations and estimated  every 15 min (October 2013 to September 2014). Changes in concentration were strongly related to water temperature. In the presence of wastewater, was generally positive, ranging from about 7 µM d−1 in the summer to near zero in the winter. Numerous periods when the WWTP halted discharge allowed the  to be estimated under no-effluent conditions and revealed that in the absence of effluent, net gains in  were substantially lower but still positive in the summer and negative (net sink) in the winter. Nitrification rates of effluent-derived NH4 ( ) were estimated from the difference between  measured in the presence versus absence of effluent and ranged from 1.5 to 3.4 µM d−1, which is within literature values but tenfold greater than recently reported for this region.  was generally lower in winter (∼2 µM d−1) than summer (∼3 µM d−1). This in situ, high frequency approach provides advantages over traditional discrete sampling, incubation, and tracer methods and allows measurements to be made over broad areas for extended periods of time. Incorporating this approach into environmental monitoring programs can facilitate our ability to protect and manage aquatic systems.

  7. Organic carbon and iron modulate nitrification rates in mangrove swamps of Goa, south west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnan, K.P.; LokaBharathi, P.A.

    . The nitrification rates at the control and experimental sites are comparable and ranged from 3.2 plus or minus 1.2 to 18.4 plus or minus 1.9 ng at-N g(sediment) sup(-1) h sup(-1) and 2.7 plus or minus 1.5 to 18.2 plus or minus 0.6 ng at-N g(sediment) sup(-1) h sup...

  8. On-line monitoring and modelling based process control of high rate nitrification - lab scale experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Pirsing, A. [Technische Univ. Berlin (Germany). Inst. fuer Verfahrenstechnik; Wiesmann, U. [Technische Univ. Berlin (Germany). Inst. fuer Verfahrenstechnik; Kelterbach, G. [Technische Univ. Berlin (Germany). Inst. fuer Mess- und Regelungstechnik; Schaffranietz, U. [Technische Univ. Berlin (Germany). Inst. fuer Mess- und Regelungstechnik; Roeck, H. [Technische Univ. Berlin (Germany). Inst. fuer Mess- und Regelungstechnik; Eichner, B. [Technische Univ. Berlin (Germany). Inst. fuer Anorganische und Analytische Chemie; Szukal, S. [Technische Univ. Berlin (Germany). Inst. fuer Anorganische und Analytische Chemie; Schulze, G. [Technische Univ. Berlin (Germany). Inst. fuer Anorganische und Analytische Chemie

    1996-09-01

    This paper presents a new concept for the control of nitrification in highly polluted waste waters. The approach is based on mathematical modelling. To determine the substrate degradation rates of the microorganisms involved, a mathematical model using gas measurement is used. A fuzzy-controller maximises the capacity utilisation efficiencies. The experiments carried out in a lab-scale reactor demonstrate that even with highly varying ammonia concentrations in the influent, the nitrogen concentrations in the effluent can be kept within legal limits. (orig.). With 11 figs.

  9. Effects of dissolved oxygen and pH on nitrous oxide production rates in autotrophic partial nitrification granules.

    Science.gov (United States)

    Rathnayake, Rathnayake M L D; Oshiki, Mamoru; Ishii, Satoshi; Segawa, Takahiro; Satoh, Hisashi; Okabe, Satoshi

    2015-12-01

    The effects of dissolved oxygen (DO) and pH on nitrous oxide (N2O) production rates and pathways in autotrophic partial nitrification (PN) granules were investigated at the granular level. N2O was primarily produced by betaproteobacterial ammonia-oxidizing bacteria, mainly Nitrosomonas europaea, in the oxic surface layer (production increased with increasing bulk DO concentration owing to activation of the ammonia (i.e., hydroxylamine) oxidation in this layer. The highest N2O emissions were observed at pH 7.5, although the ammonia oxidation rate was unchanged between pH 6.5 and 8.5. Overall, the results of this study suggest that in situ analyses of PN granules are essential to gaining insight into N2O emission mechanisms in a granule. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available The annual variation in the net long shore sediment transport rates at three South African and at one North African site is investigated. The net rates at these sites, given in the first table, showed large variations. It was found that measurements...

  11. Net savings and the Japanese long-term interest rate

    NARCIS (Netherlands)

    Jansen, P.W.

    2011-01-01

    This article discusses why the interest rate on Japanese government bonds is so low in comparison with other industrialized countries with a better credit rating, after correcting for inflation differences. We find that the net savings surplus has kept the long-term interest rate low. Japanese

  12. Spatial patterns of soil nitrification and nitrate export from forested headwaters in the northeastern United States

    Science.gov (United States)

    Ross, D.S.; Shanley, J.B.; Campbell, J.L.; Lawrence, G.B.; Bailey, S.W.; Likens, G.E.; Wemple, B.C.; Fredriksen, G.; Jamison, A.E.

    2012-01-01

    Nitrogen export from small forested watersheds is known to be affected by N deposition but with high regional variability. We studied 10 headwater catchments in the northeastern United States across a gradient of N deposition (5.4 - 9.4 kg ha -1 yr -1) to determine if soil nitrification rates could explain differences in stream water NO 3 - export. Average annual export of two years (October 2002 through September 2004) varied from 0.1 kg NO 3 --N ha -1 yr -1 at Cone Pond watershed in New Hampshire to 5.1 kg ha -1 yr -1 at Buck Creek South in the western Adirondack Mountains of New York. Potential net nitrification rates and relative nitrification (fraction of inorganic N as NO 3 -) were measured in Oa or A soil horizons at 21-130 sampling points throughout each watershed. Stream NO 3 - export was positively related to nitrification rates (r 2 = 0.34, p = 0.04) and the relative nitrification (r 2 = 0.37, p = 0.04). These relationships were much improved by restricting consideration to the 6 watersheds with a higher number of rate measurements (59-130) taken in transects parallel to the streams (r 2 of 0.84 and 0.70 for the nitrification rate and relative nitrification, respectively). Potential nitrification rates were also a better predictor of NO 3 - export when data were limited to either the 6 sampling points closest to the watershed outlet (r 2 = 0.75) or sampling points <250 m from the watershed outlet (r 2 = 0.68). The basal area of conifer species at the sampling plots was negatively related to NO 3 - export. These spatial relationships found here suggest a strong influence of near-stream and near-watershed-outlet soils on measured stream NO 3 - export. Copyright 2012 by the American Geophysical Union.

  13. Rates of convergence of Brezier net over triangles

    International Nuclear Information System (INIS)

    Feng Yuyu.

    1986-12-01

    It is well known (Farin, 1979) that the sequence of Bezier nets f-circumflex n (x) associated with Bernstein-Bezier surface over a triangle converges to the surface uniformly as n goes to infinity. In this paper the precise rates of convergence are given. The pointwise convergence result and saturation theorem are presented. (author). 7 refs

  14. Long-term dynamic and pseudo-state modeling of complete partial nitrification process at high nitrogen loading rates in a sequential batch reactor (SBR).

    Science.gov (United States)

    Soliman, Moomen; Eldyasti, Ahmed

    2017-06-01

    Recently, partial nitrification has been adopted widely either for the nitrite shunt process or intermediate nitrite generation step for the Anammox process. However, partial nitrification has been hindered by the complexity of maintaining stable nitrite accumulation at high nitrogen loading rates (NLR) which affect the feasibility of the process for high nitrogen content wastewater. Thus, the operational data of a lab scale SBR performing complete partial nitrification as a first step of nitrite shunt process at NLRs of 0.3-1.2kg/(m 3 d) have been used to calibrate and validate a process model developed using BioWin® in order to describe the long-term dynamic behavior of the SBR. Moreover, an identifiability analysis step has been introduced to the calibration protocol to eliminate the needs of the respirometric analysis for SBR models. The calibrated model was able to predict accurately the daily effluent ammonia, nitrate, nitrite, alkalinity concentrations and pH during all different operational conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Archaeal Nitrification in Hot Springs

    Science.gov (United States)

    Richter, A.; Daims, H.; Reigstad, L.; Wanek, W.; Wagner, M.; Schleper, C.

    2006-12-01

    Biological nitrification, i.e. the aerobic conversion of ammonia to nitrate via nitrite, is a major component of the global nitrogen cycle. Until recently, it was thought that the ability to aerobically oxidize ammonia was confined to bacteria of the phylum Proteobacteria. However, it has recently been shown that Archaea of the phylum Crenarchaeota are also capable of ammonia oxidation. As many Crenarchaeota are thermophilic or hyperthermophilic, and at least some of them are capable of ammonia oxidation we speculated on the existence of (hyper)thermophilic ammonia-oxidizing archaea (AOA). Using PCR primers specifically targeting the archaeal ammonia monooxygenase (amoA) gene, we were indeed able to confirm the presence of such organisms in several hot springs in Reykjadalur, Iceland. These hot springs exhibited temperatures well above 80 °C and pH values ranging from 2.0 to 4.5. To proof that nitrification actually took place under these extreme conditions, we measured gross nitrification rates by the isotope pool dilution method; we added 15N-labelled nitrate to the mud and followed the dilution of the label by nitrate production from ammonium either in situ (incubation in the hot spring) or under controlled conditions in the laboratory (at 80 °C). The nitrification rates in the hot springs ranged from 0.79 to 2.22 mg nitrate-N per L of mud and day. Controls, in which microorganisms were killed before the incubations, demonstrated that the nitrification was of biological origin. Addition of ammonium increased the gross nitrification rate approximately 3-fold, indicating that the nitrification was ammonium limited under the conditions used. Collectively, our study provides evidence that (1) AOA are present in hot springs and (2) that they are actively nitrifying. These findings have major implications for our understanding of nitrogen cycling of hot environments.

  16. The Economics of Zero-Rating and Net Neutrality

    OpenAIRE

    Somogyi, Robert

    2016-01-01

    This paper studies zero-rating, an emerging business practice consisting in a mobile internet service provider (ISP) excluding the data generated by certain content providers (CPs) from its consumers' monthly data cap. Being at odds with the principle of net neutrality, these arrangements have recently attracted regulatory scrutiny all over the word. I analyze zero-rating incentives of a monopolistic ISP facing a capacity constraint in a two-sided market where consumption provides utility for...

  17. Use of aliphatic n-alkynes to discriminate soil nitrification activities of ammonia-oxidizing thaumarchaea and bacteria.

    Science.gov (United States)

    Taylor, Anne E; Vajrala, Neeraja; Giguere, Andrew T; Gitelman, Alix I; Arp, Daniel J; Myrold, David D; Sayavedra-Soto, Luis; Bottomley, Peter J

    2013-11-01

    Ammonia (NH3)-oxidizing bacteria (AOB) and thaumarchaea (AOA) co-occupy most soils, yet no short-term growth-independent method exists to determine their relative contributions to nitrification in situ. Microbial monooxygenases differ in their vulnerability to inactivation by aliphatic n-alkynes, and we found that NH3 oxidation by the marine thaumarchaeon Nitrosopumilus maritimus was unaffected during a 24-h exposure to ≤ 20 μM concentrations of 1-alkynes C8 and C9. In contrast, NH3 oxidation by two AOB (Nitrosomonas europaea and Nitrosospira multiformis) was quickly and irreversibly inactivated by 1 μM C8 (octyne). Evidence that nitrification carried out by soilborne AOA was also insensitive to octyne was obtained. In incubations (21 or 28 days) of two different whole soils, both acetylene and octyne effectively prevented NH4(+)-stimulated increases in AOB population densities, but octyne did not prevent increases in AOA population densities that were prevented by acetylene. Furthermore, octyne-resistant, NH4(+)-stimulated net nitrification rates of 2 and 7 μg N/g soil/day persisted throughout the incubation of the two soils. Other evidence that octyne-resistant nitrification was due to AOA included (i) a positive correlation of octyne-resistant nitrification in soil slurries of cropped and noncropped soils with allylthiourea-resistant activity (100 μM) and (ii) the finding that the fraction of octyne-resistant nitrification in soil slurries correlated with the fraction of nitrification that recovered from irreversible acetylene inactivation in the presence of bacterial protein synthesis inhibitors and with the octyne-resistant fraction of NH4(+)-saturated net nitrification measured in whole soils. Octyne can be useful in short-term assays to discriminate AOA and AOB contributions to soil nitrification.

  18. Net reclassification index at event rate: properties and relationships.

    Science.gov (United States)

    Pencina, Michael J; Steyerberg, Ewout W; D'Agostino, Ralph B

    2017-12-10

    The net reclassification improvement (NRI) is an attractively simple summary measure quantifying improvement in performance because of addition of new risk marker(s) to a prediction model. Originally proposed for settings with well-established classification thresholds, it quickly extended into applications with no thresholds in common use. Here we aim to explore properties of the NRI at event rate. We express this NRI as a difference in performance measures for the new versus old model and show that the quantity underlying this difference is related to several global as well as decision analytic measures of model performance. It maximizes the relative utility (standardized net benefit) across all classification thresholds and can be viewed as the Kolmogorov-Smirnov distance between the distributions of risk among events and non-events. It can be expressed as a special case of the continuous NRI, measuring reclassification from the 'null' model with no predictors. It is also a criterion based on the value of information and quantifies the reduction in expected regret for a given regret function, casting the NRI at event rate as a measure of incremental reduction in expected regret. More generally, we find it informative to present plots of standardized net benefit/relative utility for the new versus old model across the domain of classification thresholds. Then, these plots can be summarized with their maximum values, and the increment in model performance can be described by the NRI at event rate. We provide theoretical examples and a clinical application on the evaluation of prognostic biomarkers for atrial fibrillation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  19. The effect of net foreign assets on saving rate

    Directory of Open Access Journals (Sweden)

    Ben David Nissim

    2014-01-01

    Full Text Available Observing empirical data we find that many countries try to delay the decision of increasing saving rate in order to avoid a decrease of the living standards. However the delay leads a deterioration of countries financial stability. We present a simple theoretical model that connects between countries' saving rate and their net foreign assets. Using cross section data set of 135 countries in 2010 we estimated the econometric relation between saving rate in 2010 as dependent variable and two explanatory variables: the current account in 2010 and the aggregated current account during 1980-2010. Our findings show that industrial countries in a bad financial state tend to decrease their saving rate as external debt is larger causing to deterioration in external debt while countries with good financial state tend to increase their saving rate and the tendency increase as financial state becomes better. Only in countries with a very large external debt saving rate tends to grow. The results point that gross foreign debt will keep increasing and will worsen world financial state causing increased risk of getting into a world crisis.

  20. The rate of aucubin, a secondary metabolite in Plantago lanceolata and potential nitrification inhibitor, needed to reduce ruminant urine patch nitrous oxide emissions

    Science.gov (United States)

    Gardiner, C. A.; Clough, T.; Cameron, K.; Di, H.; Edwards, G. R.

    2017-12-01

    Nitrous oxide (N2O) losses derived from grazing ruminant livestock urine patches account for 40% of global N2O emissions. It has been shown that Plantago lanceolata, an herb species used in grazed pastures, contains an active secondary metabolite (aucubin) that has the potential to be excreted by grazing ruminants and inhibit nitrification in the urine patch, a key step in soil N2O production. However, the urinary excretion rate of aucubin needed to significantly reduce urine patch N2O emissions remains unknown. Aucubin was dissolved in bovine urine at three rates (47, 243, and 486 kg ha-1), based on rates used in Dietz et al. (2013) and the calculated highest potential aucubin application rate, from Gardiner et al. (2017). A control, along with a urine treatment and the three aucubin treatments (all urine applied at 700 kg N ha-1), was applied to 20 g soil and incubated in the laboratory for 35 d. Soils were monitored for surface pH, inorganic N concentration (NH4+/NO3-), and gas (N2O and CO2) fluxes. This experiment is currently underway and the results will be presented at the conference. Dietz M, Machill S, Hoffmann H, Schmidtke K 2013. Inhibitory effects of Plantago lanceolata L. on soil N mineralization. Plant and Soil 368: 445-458. Gardiner CA, Clough TJ, Cameron KC, Di HJ, Edwards GR, de Klein CAM 2017. The potential inhibitory effects of Plantago lanceolata and its active secondary metabolite aucubin on soil nitrification and nitrous oxide emissions under ruminant urine patch conditions. Manuscript submitted for publication.

  1. Nitrification in inland waters

    NARCIS (Netherlands)

    Laanbroek, H.J.; Bollmann, A.; B. Ward, B.; J. Arp, D.; G. Klotz, M.

    2011-01-01

    Over the past 15 years, the use of modern molecular biological approaches has radically advanced our understanding of nitrification processes. With chapters contributed by leading experts in the field, Nitrification fully reviews all the latest research findings on microbes involved in conventional

  2. Effects of Applying Lime and CalciumMontmorillonite on Nitrification Dynamics in Acidic Soil

    Directory of Open Access Journals (Sweden)

    WANG Mei

    2017-01-01

    Full Text Available Soil acidification is known as a natural and slow process along with clay mineral weathering. In recent years however, with inten sive soil utilization in agriculture, soil acidification has increased dramatically and nitrification of ammonium nitrogen fertilizer is one of the main contributors to soil acidification. Lime application is the traditional practice to improve acidic soils but it often makes the soil acidic a gain leading to soil compaction in most cases. Montmorillonite is the main clay mineral component of alkaline or neutral soils, more so it is known to undergo further weathering processes during soil acidification. The laboratory-based incubations were used in this study, and nitri fication was measured while kinetic curves were fitted to check the effects of decreasing soil acidity by lime(Ca-OHand montmorillonite (Ca-Mon nitrification of the acidic soil. The results showed that significant nitrification was observed both in Ca-OH and Ca-M treatments, and the nitrification process was fitted in the first-order kinetic model, NNO3=N0+Np(1-exp(-k1t(P-1·d-1was significantly higher than that of Ca-M treatment(2.381 mg·kg-1·d-1. The potential nitrifi cation rate(Vpwere 6.42, 8.58 mg N·kg-1·d-1 at pH 5.7 and 6.2 respectively, and the average nitrification rate(Vaof Ca-OH treatment were 2.71, 3.88 mg N·kg-1·d-1 respectively, which were significantly greater than those of Ca-M treatment(Vp were 3.40, 4.56 mg N·kg-1·d-1 and Va were 2.36, 3.04 mg N·kg-1·d-1 at pH 5.7 and 6.2 respectively. Therefore the net nitrification rate, potential nitrification rate(Vp and average nitrification rate(Vaof Ca-OH treatment were significantly higher than that of Ca-M treatment, suggesting that the possibili ty and degree of soil reacidification by using lime to improve acidic soil is greater than using calcium montmorillonite. This study will provide a new reference for the improvement of acid soils.

  3. Stand-replacing wildfires increase nitrification for decades in southwestern ponderosa pine forests.

    Science.gov (United States)

    Kurth, Valerie J; Hart, Stephen C; Ross, Christopher S; Kaye, Jason P; Fulé, Peter Z

    2014-05-01

    Stand-replacing wildfires are a novel disturbance within ponderosa pine (Pinus ponderosa) forests of the southwestern United States, and they can convert forests to grasslands or shrublands for decades. While most research shows that soil inorganic N pools and fluxes return to pre-fire levels within a few years, we wondered if vegetation conversion (ponderosa pine to bunchgrass) following stand-replacing fires might be accompanied by a long-term shift in N cycling processes. Using a 34-year stand-replacing wildfire chronosequence with paired, adjacent unburned patches, we examined the long-term dynamics of net and gross nitrogen (N) transformations. We hypothesized that N availability in burned patches would become more similar to those in unburned patches over time after fire as these areas become re-vegetated. Burned patches had higher net and gross nitrification rates than unburned patches (P < 0.01 for both), and nitrification accounted for a greater proportion of N mineralization in burned patches for both net (P < 0.01) and gross (P < 0.04) N transformation measurements. However, trends with time-after-fire were not observed for any other variables. Our findings contrast with previous work, which suggested that high nitrification rates are a short-term response to disturbance. Furthermore, high nitrification rates at our site were not simply correlated with the presence of herbaceous vegetation. Instead, we suggest that stand-replacing wildfire triggers a shift in N cycling that is maintained for at least three decades by various factors, including a shift from a woody to an herbaceous ecosystem and the presence of fire-deposited charcoal.

  4. amoA Gene abundances and nitrification potential rates suggest that benthic ammonia-oxidizing bacteria and not Archaea dominate N cycling in the Colne Estuary, United Kingdom.

    Science.gov (United States)

    Li, Jialin; Nedwell, David B; Beddow, Jessica; Dumbrell, Alex J; McKew, Boyd A; Thorpe, Emma L; Whitby, Corinne

    2015-01-01

    Nitrification, mediated by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), is important in global nitrogen cycling. In estuaries where gradients of salinity and ammonia concentrations occur, there may be differential selections for ammonia-oxidizer populations. The aim of this study was to examine the activity, abundance, and diversity of AOA and AOB in surface oxic sediments of a highly nutrified estuary that exhibits gradients of salinity and ammonium. AOB and AOA communities were investigated by measuring ammonia monooxygenase (amoA) gene abundance and nitrification potentials both spatially and temporally. Nitrification potentials differed along the estuary and over time, with the greatest nitrification potentials occurring mid-estuary (8.2 μmol N grams dry weight [gdw](-1) day(-1) in June, increasing to 37.4 μmol N gdw(-1) day(-1) in January). At the estuary head, the nitrification potential was 4.3 μmol N gdw(-1) day(-1) in June, increasing to 11.7 μmol N gdw(-1) day(-1) in January. At the estuary head and mouth, nitrification potentials fluctuated throughout the year. AOB amoA gene abundances were significantly greater (by 100-fold) than those of AOA both spatially and temporally. Nitrosomonas spp. were detected along the estuary by denaturing gradient gel electrophoresis (DGGE) band sequence analysis. In conclusion, AOB dominated over AOA in the estuarine sediments, with the ratio of AOB/AOA amoA gene abundance increasing from the upper (freshwater) to lower (marine) regions of the Colne estuary. These findings suggest that in this nutrified estuary, AOB (possibly Nitrosomonas spp.) were of major significance in nitrification. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  5. Inhibitory effect of cyanide on wastewater nitrification ...

    Science.gov (United States)

    The effect of CN- (CN-) on nitrification was examined with samples from nitrifying wastewater enrichments using two different approaches: by measuring substrate (ammonia) specific oxygen uptake rates (SOUR), and by using RT-qPCR to quantify the transcripts of functional genes involved in nitrification. The nitrifying bioreactor was operated as a continuous reactor with a 24 h hydraulic retention time. The samples were exposed in batch vessels to cyanide for a period of 12 h. The concentrations of CN- used in the batch assays were 0.03, 0.06, 0.1 and 1.0 mg/L. There was considerable decrease in SOUR with increasing dosages of CN-. A decrease of more than 50% in nitrification activity was observed at 0.1 mg/L CN-. Based on the RT-qPCR data, there was notable reduction in the transcript levels of amoA and hao for increasing CN- dosage, which corresponded well with the ammonia oxidation activity measured via SOUR. The inhibitory effect of cyanide may be attributed to the affinity of cyanide to bind ferric heme proteins, which disrupt protein structure and function. The correspondence between the relative expression of functional genes and SOUR shown in this study demonstrates the efficacy of RNA based function-specific assays for better understanding of the effect of toxic compounds on nitrification activity in wastewater. Nitrification is the first step of nitrogen removal is wastewater, and it is susceptible to inhibition by many industrial chemical. We looked at

  6. Suppression of soil nitrification by plants.

    Science.gov (United States)

    Subbarao, Guntur Venkata; Yoshihashi, Tadashi; Worthington, Margaret; Nakahara, Kazuhiko; Ando, Yasuo; Sahrawat, Kanwar Lal; Rao, Idupulapati Madhusudhana; Lata, Jean-Christophe; Kishii, Masahiro; Braun, Hans-Joachim

    2015-04-01

    Nitrification, the biological oxidation of ammonium to nitrate, weakens the soil's ability to retain N and facilitates N-losses from production agriculture through nitrate-leaching and denitrification. This process has a profound influence on what form of mineral-N is absorbed, used by plants, and retained in the soil, or lost to the environment, which in turn affects N-cycling, N-use efficiency (NUE) and ecosystem health and services. As reactive-N is often the most limiting in natural ecosystems, plants have acquired a range of mechanisms that suppress soil-nitrifier activity to limit N-losses via N-leaching and denitrification. Plants' ability to produce and release nitrification inhibitors from roots and suppress soil-nitrifier activity is termed 'biological nitrification inhibition' (BNI). With recent developments in methodology for in-situ measurement of nitrification inhibition, it is now possible to characterize BNI function in plants. This review assesses the current status of our understanding of the production and release of biological nitrification inhibitors (BNIs) and their potential in improving NUE in agriculture. A suite of genetic, soil and environmental factors regulate BNI activity in plants. BNI-function can be genetically exploited to improve the BNI-capacity of major food- and feed-crops to develop next-generation production systems with reduced nitrification and N2O emission rates to benefit both agriculture and the environment. The feasibility of such an approach is discussed based on the progresses made. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  7. Complete nitrification by Nitrospira bacteria

    DEFF Research Database (Denmark)

    Daims, Holger; Lebedeva, Elena V.; Pjevac, Petra

    2015-01-01

    Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered to be a two-step process catalysed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetic...

  8. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Directory of Open Access Journals (Sweden)

    Jason M Smith

    Full Text Available Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA, are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1 to those in well-lit layers (<1 nmol L-1 d-1. During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  9. In-situ real time measurements of net erosion rates of copper during hydrogen plasma exposure

    Science.gov (United States)

    Kesler, Leigh; Wright, Graham; Peterson, Ethan; Whyte, Dennis

    2013-10-01

    In order to properly understand the dynamics of net erosion/deposition in fusion reactors, such as tokamaks, a diagnostic measuring the real time rates of net erosion/deposition during plasma exposure is necessary. The DIONISOS experiment produces real time measurements of net erosion/deposition by using Rutherford backscattering spectroscopy (RBS) ion beam analysis simultaneously with plasma exposure from a helicon plasma source. This in-situ method improves on ex-situ weight loss measurements by allowing measurement of possible synergistic effects of high ion implantation rates and net erosion rate and by giving a real time response to changes in plasma parameters. Previous work has validated this new technique for measuring copper (Cu) erosion from helium (He) plasma ion bombardment. This technique is now extended to measure copper erosion due to deuterium and hydrogen plasma ion exposure. Targets used were a 1.5 μm Cu layer on an aluminum substrate. Cu layer thickness is tracked in real time using 1.2 MeV proton RBS. Measured erosion rates will be compared to results from literature and He erosion rates. Supported by US DoE award DE-SC00-02060.

  10. Spatial variation in tuber depletion by swans explained by differences in net intake rates

    NARCIS (Netherlands)

    Nolet, BA; Langevoord, O; Bevan, RM; Engelaar, KR; Klaassen, M; Mulder, RJW

    We tested whether the spatial variation in resource depletion by Tundra Swans (Cygnus columbianus) foraging on belowground tubers of sage pondweed (Potnmogeton pectinatus) was caused by differences in net energy intake rates. The variation in giving up densities within the confines of one lake was

  11. Net capital flows to and the real exchange rate of Western Balkan countries

    Directory of Open Access Journals (Sweden)

    Gabrisch Hubert

    2015-01-01

    Full Text Available This paper uses Granger causality tests to assess the linkages between changes in the real exchange rate and net capital inflows using the example of Western Balkan countries, which have suffered from low competitiveness and external imbalances for many years. The real exchange rate is a measure of a country’s price competitiveness, and the paper uses two concepts: relative unit labour cost and relative inflation differential. The sample consists of six Western Balkan countries for the period 1996-2012, relative to the European Union (EU. The main finding is that changes in the net capital flows precede changes in relative unit labour costs and not vice versa. Also, there is evidence that net capital flows affect the inflation differential of countries, although to a less discernible extent. This suggests that the increasing divergence in the unit labour cost between the EU and Western Balkan countries up to the global financial crisis was at least partly the result of net capital inflows. The paper adds to the ongoing debate on improving cost competitiveness through wage restrictions as the main vehicle to avert the accumulation of current account imbalances. It shows the importance of changes in the exchange rate regime, reform of the interaction between the financial and the real sector, and financial supervision and structural change.

  12. Nitrification in Saline Industrial Wastewater

    NARCIS (Netherlands)

    Moussa, M.S.

    2004-01-01

    Biological nitrogen removal is widely and successfully applied for municipal wastewater. However, these experiences are not directly applicable to industrial wastewater, due to its specific composition. High salt levels in many industrial wastewaters affect nitrification negatively and improved

  13. Some plant extracts retarde nitrification in soil

    Directory of Open Access Journals (Sweden)

    Abdul–Mehdi S. AL-ANSARI

    2015-12-01

    Full Text Available An incubation experiment was conducted to evaluate the effect of aqueous extracts of 17 plant materials on nitrification inhibition of urea- N in soil as compared with chemical inhibitor Dicyandiamide (DCD. Plant materials used in study were collected from different areas of Basrah province, south of Iraq. Aqueous extracts were prepared at ratio of 1:10 (plant material: water and added at conc. of 0.05, 0.10 and 0.20 ml g– 1 soil to loamy sand soil. DCD was added to soil at rate of 50 µg g-1 soil . Soil received urea at rate of 1000 µg N g-1 soil. Treated soils were incubated at 30 OC for 40 days. Results showed that application of all plant extracts, except those of casuarina, date palm and eucalyptus to soil retarded nitrification in soil. Caper, Sowthistle ,bladygrass and pomegranate extracts showed highest inhibition percentage (51, 42, 40 and 40 %, respectively and were found to be more effective than DCD (33 %. Highest inhibition was achieved by using those extracts at conc. of 0.1 ml g-1 soil after 10 days of incubation . Data also revealed that treated soil with these plant extracts significantly increased amount of NH4+–N and decreased amount of NO3-–N accumulation in soil compared with DCD and control treatments. Results of the study suggested a possibility of using aqueous extracts of some studied plants as potent nitrification inhibitor in soil.

  14. The Influence of Herbivory on the net rate of Increase of Gypsy Moth Abundance: A Modeling Analysis

    Science.gov (United States)

     Harry T.  Valentine

    1983-01-01

    A differential equation model of gypsy moth abundance, average larval dry weight, and food abundance was used to analyze the effects of changes in foliar chemistry on the net per capita rate of increase in a gypsy moth population. If relative consumption rate per larva is unaffected by herbivory, a reduction in the nutritional value of foliage reduces the net rate of...

  15. Ammonium uptake by phytoplankton regulates nitrification in the sunlit ocean.

    Science.gov (United States)

    Smith, Jason M; Chavez, Francisco P; Francis, Christopher A

    2014-01-01

    Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean's surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L-1 d-1) to those in well-lit layers (ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean.

  16. Single interval longwave radiation scheme based on the net exchanged rate decomposition with bracketing

    Czech Academy of Sciences Publication Activity Database

    Geleyn, J.- F.; Mašek, Jan; Brožková, Radmila; Kuma, P.; Degrauwe, D.; Hello, G.; Pristov, N.

    2017-01-01

    Roč. 143, č. 704 (2017), s. 1313-1335 ISSN 0035-9009 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:86652079 Keywords : numerical weather prediction * climate models * clouds * parameterization * atmospheres * formulation * absorption * scattering * accurate * database * longwave radiative transfer * broadband approach * idealized optical paths * net exchanged rate decomposition * bracketing * selective intermittency Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 3.444, year: 2016

  17. Optimizing nitrification in biological rapid sand filters for drinking water production

    DEFF Research Database (Denmark)

    Albrechtsen, Hans-Jørgen; Smets, Barth F.; Lee, Carson Odell

    Addition of phosphate or trace metals or better management e.g. in terms of anmonium load can improve the nitrification rate and efficiency in biological rapid sand filters.......Addition of phosphate or trace metals or better management e.g. in terms of anmonium load can improve the nitrification rate and efficiency in biological rapid sand filters....

  18. Generation time, net reproductive rate, and growth in stage-age-structured populations

    DEFF Research Database (Denmark)

    Steiner, Uli; Tuljapurkar, Shripad; Coulson, Tim

    2014-01-01

    examples to show how reproductive timing Tc and level R0 are shaped by stage dynamics (individual trait changes), selection on the trait, and parent-offspring phenotypic correlation. We also show how population structure can affect dispersion in reproduction among ages and stages. These macroscopic...... to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple...

  19. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Science.gov (United States)

    Vargas-Ángel, Bernardo; Richards, Cristi L; Vroom, Peter S; Price, Nichole N; Schils, Tom; Young, Charles W; Smith, Jennifer; Johnson, Maggie D; Brainard, Russell E

    2015-01-01

    This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2) yr(-1)) of early successional recruitment communities on Calcification Accretion Unit (CAU) plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years) of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA) percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons makes CCA

  20. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Directory of Open Access Journals (Sweden)

    Bernardo Vargas-Ángel

    Full Text Available This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2 yr(-1 of early successional recruitment communities on Calcification Accretion Unit (CAU plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons

  1. Full-scale trials of external nitrification on plastic media nitrifying ...

    African Journals Online (AJOL)

    The apparent ammonia nitrification rate (ApANR, gN/m2 media surface∙d) of the NTF was sensitive to ... est in integrating them with NDBEPRAS systems in an external nitrification flow scheme ... The NTF tower was tested over a period of 2 years (Sept 05 to Sept 07) to ...... leak badly, in particular at high HLRs. References.

  2. Capture efficiency and injury rates of band-tailed pigeons using whoosh nets

    Science.gov (United States)

    Coxen, Christopher L.; Collins, Daniel P.; Carleton, Scott A.

    2018-01-01

    Catching ground feeding birds has typically been accomplished through small, walk-in funnel-style traps. This approach is limited because it requires a bird to find its way into the trap, is biased toward less wary birds, and does not allow targeted trapping of individual birds. As part of a large study on Band-tailed Pigeons (Patagioenas fasciata) in New Mexico, we needed a trapping method that would allow more control over the number of birds we could trap at one time, when a trap was deployed, and target trapping of specific individuals. We adopted a relatively novel trapping technique used primarily for shorebirds, whoosh nets, to trap Band-tailed Pigeons at 3 different sites where birds were being fed by local landowners. During 2013–2015, whoosh nets were used to trap 702 Band-tailed Pigeons at 3 different locations in New Mexico. We captured 12.54 ± 8.19 pigeons per shot over 56 capture events across 3 locations (range: 2–39). Some superficial injuries occurred using this technique and typically involved damage to the primary and secondary wing coverts. In 2013, 24% of captured birds had an injury of this nature, but after modifying the net speed, injury rates in 2014 and 2015 dropped to 8% and 7%, respectively. Recaptured previously injured birds showed new feather growth within 2 weeks and showed no signs of injury after 4 weeks. Whoosh nets proved to be a highly effective solution for trapping large numbers of pigeons at baited sites. These systems are easily transported, quickly deployed, and easily adapted to a variety of site conditions. 

  3. Annual and Seasonal Mean Net Evaporation Rates of the Red Sea Water during Jan 1958 - Dec 2007

    OpenAIRE

    Nassir, Sahbaldeen Abdulaziz

    2012-01-01

    Data set including sea level, temperature, salinity, and current from Simple Ocean Data Assimilation (SODA) is used in this study to estimate the mean net annually and seasonally evaporation rates. Then wind data is used to examine its impact on the evaporation. This work calculated the seasonal and annual evaporation rates based on assumption of that there is no net mass transport (balanced). Hence, the difference in the transport supposed to be equal to the water that has eva...

  4. A New Approach for Mobile Advertising Click-Through Rate Estimation Based on Deep Belief Nets.

    Science.gov (United States)

    Chen, Jie-Hao; Zhao, Zi-Qian; Shi, Ji-Yun; Zhao, Chong

    2017-01-01

    In recent years, with the rapid development of mobile Internet and its business applications, mobile advertising Click-Through Rate (CTR) estimation has become a hot research direction in the field of computational advertising, which is used to achieve accurate advertisement delivery for the best benefits in the three-side game between media, advertisers, and audiences. Current research on the estimation of CTR mainly uses the methods and models of machine learning, such as linear model or recommendation algorithms. However, most of these methods are insufficient to extract the data features and cannot reflect the nonlinear relationship between different features. In order to solve these problems, we propose a new model based on Deep Belief Nets to predict the CTR of mobile advertising, which combines together the powerful data representation and feature extraction capability of Deep Belief Nets, with the advantage of simplicity of traditional Logistic Regression models. Based on the training dataset with the information of over 40 million mobile advertisements during a period of 10 days, our experiments show that our new model has better estimation accuracy than the classic Logistic Regression (LR) model by 5.57% and Support Vector Regression (SVR) model by 5.80%.

  5. A New Approach for Mobile Advertising Click-Through Rate Estimation Based on Deep Belief Nets

    Directory of Open Access Journals (Sweden)

    Jie-Hao Chen

    2017-01-01

    Full Text Available In recent years, with the rapid development of mobile Internet and its business applications, mobile advertising Click-Through Rate (CTR estimation has become a hot research direction in the field of computational advertising, which is used to achieve accurate advertisement delivery for the best benefits in the three-side game between media, advertisers, and audiences. Current research on the estimation of CTR mainly uses the methods and models of machine learning, such as linear model or recommendation algorithms. However, most of these methods are insufficient to extract the data features and cannot reflect the nonlinear relationship between different features. In order to solve these problems, we propose a new model based on Deep Belief Nets to predict the CTR of mobile advertising, which combines together the powerful data representation and feature extraction capability of Deep Belief Nets, with the advantage of simplicity of traditional Logistic Regression models. Based on the training dataset with the information of over 40 million mobile advertisements during a period of 10 days, our experiments show that our new model has better estimation accuracy than the classic Logistic Regression (LR model by 5.57% and Support Vector Regression (SVR model by 5.80%.

  6. A New Approach for Mobile Advertising Click-Through Rate Estimation Based on Deep Belief Nets

    Science.gov (United States)

    Zhao, Zi-Qian; Shi, Ji-Yun; Zhao, Chong

    2017-01-01

    In recent years, with the rapid development of mobile Internet and its business applications, mobile advertising Click-Through Rate (CTR) estimation has become a hot research direction in the field of computational advertising, which is used to achieve accurate advertisement delivery for the best benefits in the three-side game between media, advertisers, and audiences. Current research on the estimation of CTR mainly uses the methods and models of machine learning, such as linear model or recommendation algorithms. However, most of these methods are insufficient to extract the data features and cannot reflect the nonlinear relationship between different features. In order to solve these problems, we propose a new model based on Deep Belief Nets to predict the CTR of mobile advertising, which combines together the powerful data representation and feature extraction capability of Deep Belief Nets, with the advantage of simplicity of traditional Logistic Regression models. Based on the training dataset with the information of over 40 million mobile advertisements during a period of 10 days, our experiments show that our new model has better estimation accuracy than the classic Logistic Regression (LR) model by 5.57% and Support Vector Regression (SVR) model by 5.80%. PMID:29209363

  7. Copper deficiency can limit nitrification in biological rapid sand filters for drinking water production

    DEFF Research Database (Denmark)

    Wagner, Florian Benedikt; Nielsen, Peter Borch; Boe-Hansen, Rasmus

    2016-01-01

    Incomplete nitrification in biological filters during drinking water treatment is problematic, as it compromises drinking water quality. Nitrification problems can be caused by a lack of nutrients for the nitrifying microorganisms. Since copper is an important element in one of the essential...... enzymes in nitrification, we investigated the effect of copper dosing on nitrification in different biological rapid sand filters treating groundwater. A lab-scale column assay with filter material from a water works demonstrated that addition of a trace metal mixture, including copper, increased ammonium...... to the bulk phase. Overall, copper dosing to poorly performing biological rapid sand filters increased ammonium removal rates significantly, achieving effluent concentrations of below 0.01 mg NH4-N L-1, and had a long-term effect on nitrification performance....

  8. Reforestation in southern China: revisiting soil N mineralization and nitrification after 8 years restoration

    Science.gov (United States)

    Mo, Qifeng; Li, Zhi'An; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming

    2016-01-01

    Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China.

  9. Effect on phloridzin on net rate of liquid absorption from the pleural space of rabbits.

    Science.gov (United States)

    Zocchi, L; Agostoni, E; Raffaini, A

    1996-11-01

    Previous indirect findings have suggested the occurrence of solute-coupled liquid absorption from the pleural space, consistent with Na(+)-K(+)-ATPase on the interstitial side plus a Na(+)-H+ and CI(-)-HCO3- double exchange on the luminal side of the pleural mesothelium. To assess whether Na(+)-glucose cotransport also operates on the luminal side, the relationship between net rate of liquid absorption from the right pleural space (Jnet) and volume of liquid injected into this space (0.5, 1 or 2 ml) was determined in anaesthetized rabbits during hydrothoraces with phloridzin (10(-3)M) or with phloridzin plus 4-acetamido-4'-isothiocyanatostilbene-2, 2'-disulphonic acid (SITS; 1.5 x 10(-4)M). The relationship obtained during hydrothoraces with phloridzin was displaced downwards by 0.09 ml h-1 relative to that in control hydrothoraces (P pleural mesothelium, operating simultaneously with the double exchange also under physiological conditions.

  10. Nitrification in reef corals

    Digital Repository Service at National Institute of Oceanography (India)

    Wafar, M.V.M.; Wafar, S.; David, J.J.

    . An estimate of the density of nitrifying bacteria on living corals can be made by comparing the nitrifying rates of bacterial cells and the rate of production of NO,-. Kaplan (1983) summarized the growth con- stants of marine nitrifying bacteria... Reef Con=. 3: 395-399. -, C. R. WILKINSON, V. p. VICENTE, J. M. MORELL, AND E. OTERO. 1988. Nitrate release by Carib- bean reef sponges. Limnol. Oceanogr. 33: 114- 120. CROSSLAND, C. J., AND D. J. BARNES. 1983. Dissolved nutrients and organic...

  11. The impact of rate design and net metering on the bill savings from distributed PV for residential customers in California

    International Nuclear Information System (INIS)

    Darghouth, Naim R.; Barbose, Galen; Wiser, Ryan

    2011-01-01

    Net metering has become a widespread mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), but has faced challenges as PV installations grow to a larger share of generation in a number of states. This paper examines the value of the bill savings that customers receive under net metering, and the associated role of retail rate design, based on a sample of approximately two hundred residential customers of California's two largest electric utilities. We find that the bill savings per kWh of PV electricity generated varies by more than a factor of four across the customers in the sample, which is largely attributable to the inclining block structure of the utilities' residential retail rates. We also compare the bill savings under net metering to that received under three potential alternative compensation mechanisms, based on California's Market Price Referent (MPR). We find that net metering provides significantly greater bill savings than a full MPR-based feed-in tariff, but only modestly greater savings than alternative mechanisms under which hourly or monthly net excess generation is compensated at the MPR rate. - Highlights: → We examine the value of bill savings under net metering to PV owners in California. → Bill savings per kWh of PV generation varies by a factor of four with net metering. The variation is attributable to rate design, the unique inclining block structure. → The median value of bill savings is reduced by 40-67% with MPR feed-in tariff. → The median value of bill savings is reduced by 6-12% with hourly netting.

  12. Size and growth rate differences of larval Baltic sprat Sprattus sprattus collected with bongo and MIK nets.

    Science.gov (United States)

    Fey, D P

    2015-01-01

    The effect of sampling with bongo (0·6 m diameter frame with 500 µm mesh) and Methot Isaac Kidd (MIK) (2 m diameter frame with 2 mm mesh finished with 500 µm codend) nets on standard length (LS ) range and growth rate differences was tested for larval Sprattus sprattus (n = 906, LS range: 7·0-34·5 mm) collected during four cruises in the summer months of 2006, 2007, 2009 and 2010 in the southern Baltic Sea. Although the minimum size of larvae collected with the bongo and MIK nets was similar in each cruise (from c. 7 to 9 mm), the MIK nets permitted collecting larger specimens (up to c. 34 mm) than the bongo nets did (up to c. 27 mm). The growth rates of larvae collected with the bongo and MIK nets (specimens of the same size range were compared for three cruises) were not statistically different (mean = 0·55 mm day(-1) , n = 788, LS range: 7·0-27·4 mm), which means the material collected with these two nets can be combined and growth rate results between them were compared. © 2014 The Fisheries Society of the British Isles.

  13. Influence of Subjectivity in Geological Mapping on the Net Penetration Rate Prediction for a Hard Rock TBM

    Science.gov (United States)

    Seo, Yongbeom; Macias, Francisco Javier; Jakobsen, Pål Drevland; Bruland, Amund

    2018-05-01

    The net penetration rate of hard rock tunnel boring machines (TBM) is influenced by rock mass degree of fracturing. This influence is taken into account in the NTNU prediction model by the rock mass fracturing factor ( k s). k s is evaluated by geological mapping, the measurement of the orientation of fractures and the spacing of fractures and fracture type. Geological mapping is a subjective procedure. Mapping results can therefore contain considerable uncertainty. The mapping data of a tunnel mapped by three researchers were compared, and the influence of the variation in geological mapping was estimated to assess the influence of subjectivity in geological mapping. This study compares predicted net penetration rates and actual net penetration rates for TBM tunneling (from field data) and suggests mapping methods that can reduce the error related to subjectivity. The main findings of this paper are as follows: (1) variation of mapping data between individuals; (2) effect of observed variation on uncertainty in predicted net penetration rates; (3) influence of mapping methods on the difference between predicted and actual net penetration rate.

  14. Net herbage accumulation rate and crude protein content of Urochloa brizantha cultivars under shade intensities

    Directory of Open Access Journals (Sweden)

    Paulo Roberto de Lima Meirelles

    2013-12-01

    Full Text Available The use of silvopastoral systems is a sustainable alternative for animal production in various regions of the Brazil. However to obtain satisfactory results in these systems, the selection of forage species that grows well in the shade should be done. The tolerance of plants to light restriction and the correctly choice of species, considering good nutritional values for these conditions has great importance. The study of artificial shading for forage production helps the clarification of issues related to the behavior of plants under reduced light prior to use in integrations with forests. The aim of the study was to evaluate the net herbage accumulation rate of forage (HAR and crude protein (CP of Urochloa brizantha cultivars (Marandu and Piatã under natural light and shading of 30 and 60%. The experiment was conducted at FMVZ - UNESP, Botucatu. The experimental design was a randomized block in factorial arrangement 3 x 2 (three shading levels: 0, 30 and 60%, two cultivars: Marandu and Piatã with three replications and repeated measures (3 cuts. Sample collection occurred when the cultivars reached 35 cm in height. The treatments with shading showed lower cutting intervals as compared to those subjected to full sunlight, because they have reached in a shorter time to time as determined cut-off criterion (mean of 37, 45 and 61 days for reduction of 60%, reduction of 30% and full sun. Significant effects (P<0.05 interaction cultivar x shade x cut on the net herbage accumulation rate (HAR. Most HAR (P<0.05 was observed for cv. Marandu 60% reduction in lightness (127 kg/ha/day due to increased production of stem during the first growing cycle. The lower HAR also occurred to Marandu, but under natural light in the third cut (34 kg/ha/day due to adverse weather conditions during the growth interval. The shadow effect and the cutting (P<0.05 affected CP. The percentage of CP on cultivars showed the highest values (average value of 9.27% in 60

  15. How inhibiting nitrification affects nitrogen cycle and reduces ...

    Science.gov (United States)

    We conducted a meta-analysis of 103 nitrification inhibitor (NI) studies, and evaluated how NI application affects crop productivity and other ecosystem services in agricultural systems. Our results showed that, compared to conventional fertilizer practice, applications of NI along with nitrogen (N) fertilizer increased crop nitrogen use efficiency, crop yield, and altered the pathways and the amount of N loss to environment. NI application increased ammonia emission, but reduced nitrate leaching and nitrous oxide emission, which led to a reduction of 12.9% of the total N loss. The cost and benefit analysis showed that the economic benefit of reducing N’s environmental impacts offset the cost of NI. NI application could bring additional revenue of $163.72 ha-1 for a maize farm. Taken together, our findings show that NI application may create a win-win scenario that increases agricultural output, while reducing the negative impact on the environment. Policies that encourage NI application would reduce N’s environmental impacts. A group from Chinese Academy of Sciences, US EPA-ORD and North Carolina examined the net environmental and economic effects of nitrification inhibitors to reduce nitrate leaching associated with farm fertilizers. They conducted a meta-analysis of studies examining nitrification inhibitors, and found that NI application increased ammonia emission, but reduced nitrate leaching and nitrous oxide emission, which led to a reduction of 12.9

  16. [Effects of reduced solar radiation on winter wheat flag leaf net photosynthetic rate].

    Science.gov (United States)

    Zheng, You-Fei; Ni, Yan-Li; Mai, Bo-Ru; Wu, Rong-Jun; Feng, Yan; Sun, Jian; Li, Jian; Xu, Jing-Xin

    2011-06-01

    Taking winter wheat Triticum aestivum L. (cv. Yangmai 13) as test material, a field experiment was conducted in Nanjing City to study the effects of simulated reduced solar radiation on the diurnal variation of winter wheat flag leaf photosynthetic rate and the main affecting factors. Five treatments were installed, i. e., 15% (T15), 20% (T20) , 40% (T40), 60% (T60), and 100% (CK) of total incident solar radiation. Reduced solar irradiance increased the chlorophyll and lutein contents significantly, but decreased the net photosynthetic rate (Pn). Under different solar irradiance, the diurnal variation of Pn had greater difference, and the daily maximum Pn was in the order of CK > T60 > T40 > T 20 > T15. In CK, the Pn exhibited a double peak diurnal curve; while in the other four treatments, the Pn showed a single peak curve, and the peak was lagged behind that of CK. Correlation analysis showed that reduced solar irradiance was the main factor affecting the diurnal variation of Pn, but the physiological parameters also played important roles in determining the diurnal variation of Pn. In treatments T60 and T40, the photosynthesis active radiation (PAR), leaf temperature (T1) , stomatal conductance (Gs) , and transpiration rate (Tr) were significantly positively correlated with Pn, suggesting their positive effects on Pn. The intercellular CO2 concentration (Ci) and stomatal limitation (Ls) had significant negative correlations with Pn in treatments T60 and T40 but significant positive correlations with Pn in treatments T20 and T15, implying that the Ci and Ls had negative (or positive) effects on Pn when the solar irradiance was higher (or lower) than 40% of incident solar irradiance.

  17. Data filtering and expected muon and neutrino event rates in the KM3NeT neutrino telescope

    Energy Technology Data Exchange (ETDEWEB)

    Shanidze, Rezo [ECAP, University of Erlangen-Nuremberg, Erwin-Rommel-Str.1, 91058 Erlangen (Germany); Collaboration: ANTARES-KM3NeT-Erlangen-Collaboration

    2011-07-01

    KM3NeT is a future Mediterranean deep sea neutrino telescope with an instrumented volume of several cubic kilometres. The neutrino and muon events in KM3NeT will be reconstructed from the signals collected from the telescope's photo detectors. However, in the deep sea the dominant source of photon signals are the decays of K40 nuclei and bioluminescence. The selection of neutrino and muon events requires the implementation of fast and efficient data filtering algorithms for the reduction of accidental background event rates. Possible data filtering and triggering schemes for the KM3NeT neutrino telescope and expected muon and neutrino event rates are discussed.

  18. Recovery of soil nitrification after long-term zinc exposure and its co-tolerance to Cu in different soils.

    Science.gov (United States)

    Liu, Aiju; Fang, Dianmei; Wang, Chao; Li, Menghong; Young, Robert B

    2015-01-01

    Soils sampled from different locations of China were used to manipulate soil microbial diversity and to assess the effect of the diversity of the soil nitrifying community on the recovery of the soil nitrification to metal stress (zinc). Ten treatments were either or not amended with ZnCl2. Subsequently, a spike-on-spike assay was set up to test for the tolerance of soil nitrification to zinc (Zn) and copper (Cu). Initially, Zn amendment completely inhibited nitrification. After a year of Zn exposure, recovery of the potential nitrification rate in Zn-amended soils ranged from 28 to 126% of the potential nitrification rate in the corresponding Zn-nonamended soils. This recovery was strongly related to the potential nitrification rate before Zn amendment and soil pH. Increased Zn tolerance of the soil nitrification was consistently observed in response to corresponding soil contamination. Co-tolerance to Cu was obtained in all 1,000-mg kg(-1) Zn-amended soils. This tolerance was also strongly related to the potential nitrification rate before Zn amendment and soil pH. Our data indicate that inherently microbial activity can be a significant factor for the recovery of soil functioning derived from metal contamination.

  19. Nitrification and the ammonia-oxidizing communities in the central Baltic Sea water column

    Science.gov (United States)

    Jäntti, Helena; Ward, Bess B.; Dippner, Joachim W.; Hietanen, Susanna

    2018-03-01

    The redoxclines that form between the oxic and anoxic water layers in the central Baltic Sea are sites of intensive nitrogen cycling. To gain better understanding of nitrification, we measured the biogeochemical properties along with potential nitrification rates and analyzed the assemblages of ammonia-oxidizing bacteria and archaea using functional gene microarrays. To estimate nitrification in the entire water column, we constructed a regression model for the nitrification rates and applied it to the conditions prevailing in the area in 2008-2012. The highest ammonia oxidation rates were found in a thin layer at the top of the redoxcline and the rates quickly decreased below detection limit when oxygen was exhausted. This is probably because extensive suboxic layers, which are known to harbor pelagic nitrification, are formed only for short periods after inflows in the Baltic Sea. The nitrification rates were some of the highest measured in the water columns, but the thickness of the layer where conditions were favorable for nitrification, was very small and it remained fairly stable between years. However, the depth of the nitrification layer varied substantially between years, particularly in the eastern Gotland Basin (EGB) due to turbulence in the water column. The ammonia oxidizer communities clustered differently between the eastern and western Gotland Basin (WGB) and the composition of ammonia-oxidizing assemblages correlated with the environmental variables. The ammonia oxidizer community composition was more even in the EGB, which may be related to physical instability of the redoxcline that does not allow predominance of a single archetype, whereas in the WGB, where the position of the redoxcline is more constant, the ammonia-oxidizing community was less even. Overall the ammonia-oxidizing communities in the Baltic Sea redoxclines were very evenly distributed compared to other marine environments where microarrays have been applied previously.

  20. Net sputtering rate due to hot ions in a Ne-Xe discharge gas bombarding an MgO layer

    International Nuclear Information System (INIS)

    Ho, S.; Tamakoshi, T.; Ikeda, M.; Mikami, Y.; Suzuki, K.

    2011-01-01

    An analytical method is developed for determining net sputtering rate for an MgO layer under hot ions with low energy ( h i , above a threshold energy of sputtering, E th,i , multiplied by a yield coefficient. The threshold energy of sputtering is determined from dissociation energy required to remove an atom from MgO surface multiplied by an energy-transfer coefficient. The re-deposition rate of the sputtered atoms is calculated by a diffusion simulation using a hybridized probabilistic and analytical method. These calculation methods are combined to analyze the net sputtering rate. Maximum net sputtering rate due to the hot neon ions increases above the partial pressure of 4% xenon as E h Ne becomes higher and decreases near the partial pressure of 20% xenon as ion flux of neon decreases. The dependence due to the hot neon ions on partial pressure and applied voltage agrees well with experimental results, but the dependence due to the hot xenon ions deviates considerably. This result shows that the net sputtering rate is dominated by the hot neon ions. Maximum E h Ne (E h Ne,max = 5.3 - 10.3 eV) is lower than E th,Ne (19.5 eV) for the MgO layer; therefore, weak sputtering due to the hot neon ions takes place. One hot neon ion sputters each magnesium and each oxygen atom on the surface and distorts around a vacancy. The ratio of the maximum net sputtering rate is approximately determined by number of the ions at E h i,max multiplied by an exponential factor of -E th,i /E h i,max .

  1. Molecular biological methods (DGGE) as a tool to investigate nitrification inhibition in wastewater treatment.

    Science.gov (United States)

    Kreuzinger, N; Farnleitner, A; Wandl, G; Hornek, R; Mach, R

    2003-01-01

    Incomplete nitrification at an activated sludge plant for biological pre-treatment of rendering plant effluents led to a detailed investigation on the origin and solution of this problem. Preliminary studies revealed that an inhibition of ammonia oxidising microorganisms (AOM) by process waters of the rendering plant was responsible for the situation. We were able to show a correlation between the existence of specific AOM and nitrification capacity expressed as oxygen uptake rate for maximal nitrification (OURNmax). Only Nitrosospira sp. was found in the activated sludge of the rendering plant and another industrial wastewater treatment plant with problems in nitrification, while reference plants without nitrification problems showed Nitrosomonas spp. as the predominant ammonia oxidising bacteria. By accompanying engineering investigations and experiments (cross-feeding experiments, operation of a two-stage laboratory plant) with molecular biological methods (DGGE--Denaturing Gradient Gel Electrophoresis) we were able to elaborate an applicable solution for the rendering plant. Laboratory experiments with a two-stage process layout finally provided complete nitrification overcoming the inhibiting nature of process waters from the rendering plant. DGGE analysis of the second stage activated sludge from the laboratory plant showed a shift in population structure from Nitrosospira sp. towards Nitrosomonas spp. simultaneous to the increase of nitrification capacity. Nitrification capacities comparable to full-scale municipal wastewater treatment plants could be maintained for more than two months. As the design of wastewater treatment plants for nitrification is linked to the growth characteristics of Nitrosomonas spp., established criteria can be applied for the redesign of the full-scale plant.

  2. Low inflation, a high net savings surplus and institutional restrictions keep the Japanese long-term interest rate low

    NARCIS (Netherlands)

    Jansen, Pieter W.

    2006-01-01

    This paper explains that the interest rate on long-term Japanese government bonds is low in comparison with other industrialised countries for four main reasons: lower inflation, net savings surplus, institutional restrictions and home bias. Monetary policy and institutionalised purchases of

  3. Net Metering and Market Feedback Loops: Exploring the Impact of Retail Rate Design on Distributed PV Deployment

    Energy Technology Data Exchange (ETDEWEB)

    Darghouth, Naïm R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wiser, Ryan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Barbose, Galen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Mills, Andrew [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-01-13

    The substantial increase in deployment of customer-sited solar photovoltaics (PV) in the United States has been driven by a combination of steeply declining costs, financing innovations, and supportive policies. Among those supportive policies is net metering, which in most states effectively allows customers to receive compensation for distributed PV generation at the full retail electricity price. The current design of retail electricity rates and the presence of net metering have elicited concerns that the possible under-recovery of fixed utility costs from PV system owners may lead to a feedback loop of increasing retail prices that accelerate PV adoption and further rate increases. However, a separate and opposing feedback loop could offset this effect: increased PV deployment may lead to a shift in the timing of peak-period electricity prices that could reduce the bill savings received under net metering where time-varying retail electricity rates are used, thereby dampening further PV adoption. In this paper, we examine the impacts of these two competing feedback dynamics on U.S. distributed PV deployment through 2050 for both residential and commercial customers, across states. Our results indicate that, at the aggregate national level, the two feedback effects nearly offset one another and therefore produce a modest net effect, although their magnitude and direction vary by customer segment and by state. We also model aggregate PV deployment trends under various rate designs and net-metering rules, accounting for feedback dynamics. Our results demonstrate that future adoption of distributed PV is highly sensitive to retail rate structures. Whereas flat, time-invariant rates with net metering lead to higher aggregate national deployment levels than the current mix of rate structures (+5% in 2050), rate structures with higher monthly fixed customer charges or PV compensation at levels lower than the full retail rate can dramatically erode aggregate customer

  4. Comparison of partial and full nitrification processes applied for treating high-strength nitrogen wastewaters: microbial ecology through nitrous oxide production.

    Science.gov (United States)

    Ahn, Joon Ho; Kwan, Tiffany; Chandran, Kartik

    2011-04-01

    The goal of this study was to compare the microbial ecology, gene expression, biokinetics, and N2O emissions from a lab-scale bioreactor operated sequentially in full-nitrification and partial-nitrification modes. Based on sequencing of 16S rRNA and ammonia monooxygenase subunit A (amoA) genes, ammonia oxidizing bacteria (AOB) populations during full- and partial-nitrification modes were distinct from one another. The concentrations of AOB (XAOB) and their respiration rates during full- and partial-nitrification modes were statistically similar, whereas the concentrations of nitrite oxidizing bacteria (XNOB) and their respiration rates declined significantly after the switch from full- to partial-nitrification. The transition from full-nitrification to partial nitrification resulted in a protracted transient spike of nitrous oxide (N2O) and nitric oxide (NO) emissions, which later stabilized. The trends in N2O and NO emissions correlated well with trends in the expression of nirK and norB genes that code for the production of these gases in AOB. Both the transient and stabilized N2O and NO emissions during partial nitrification were statistically higher than those during steady-state full-nitrification. Based on these results, partial nitrification strategies for biological nitrogen removal, although attractive for their reduced operating costs and energy demand, may need to be optimized against the higher carbon foot-print attributed to their N2O emissions.

  5. Gill net selectivity and catch rates of pelagic fish in tropical coastal ...

    African Journals Online (AJOL)

    The fish species and size selectivity of gillnets design with monofilament nylon polyethylene netting materials were investigated in Lagos Lagoon, Nigeria between September and December 2005. The gillnets floats and sinkers were improvised from rubber slippers and lead metallic objects which were attached at intervals ...

  6. Dicyandiamide as nitrification inhibitor of pig slurry ammonium nitrogen in soil

    Directory of Open Access Journals (Sweden)

    Rogério Gonzatto

    2016-05-01

    Full Text Available ABSTRACT: Inhibition of nitrification of ammoniacal nitrogen pig slurry after its application to the soil can mitigate nitrogen (N losses by nitrate (NO3 - denitrification and leaching, with economical and environmental benefits. However, the use of this strategy is incipient in Brazil and, therefore, requires further assessment. The aim of this study was to evaluate the efficiency of dicyandiamide (DCD nitrification inhibitor in slowing the nitrification of ammoniacal N applied to the soil with pig slurry (PS. For this, incubation was performed in laboratory, where nitrification was assessed by NO3 - accumulation in the soil. Rates of 2.8, 5.7 and 11.3kg DCD ha-1 were compared, being applied to the soil during PS addition. Nitrification was inhibited by DCD, and inhibition magnitude and duration depended on DCD applied rate. At a dose of 11.3kg ha-1 DCD, nitrification was completely inhibited in the first 12 days. During the first month after PS application, each 2.8kg of DCD increase applied per hectare promoted NO3 --N reduction in the soil of 13.3kg ha-1, allowing longer ammoniacal N maintenance in the soil.

  7. Environmental factors affecting rates of nitrogen cycling

    International Nuclear Information System (INIS)

    Lipschultz, F.

    1984-01-01

    The nitrogen cycle in the eutrophic Delaware river was studied in late summer, 1983 using 15 N tracer additions of NHG 4 + , NO 2 - , and NO 3 - . Rates for nine different transformations were calculated simultaneously with a least-squares minimization analysis. Light was found to stimulate ammonium uptake and to inhibit ammonium oxidation. Rates for nitrification, ammonium uptake by phytoplankton, and photosynthesis were integrated over 24 hours and river depth. High turbidity lifted the effect of light inhibition on nitrification and restricted phytoplankton uptake. Uptake of ammonium contributed over 95% of the inorganic nitrogen ration for phytoplankton, with dark uptake accounting for more than 50%. A mass-conservation, box model of river was used to calculate rate constants required to reproduce observed nutrient concentration changes. The calculated constants correlated well with the measured 15 N and oxygen integrated rates. Water-column nitrification was the major loss term for NH 4 + , while water column regeneration was the primary source. Loss of oxidized nitrogen was insignificant. Oxygen consumption and air-water exchange far exceeded net photosynthetic oxygen production. Nitrification contributed less than 1% to the oxygen demand near Philadelphia but up to 25% further downstream. Production of NO and N 2 O was measured under varying oxygen concentrations in batch cultures of the nitrifying bacteria Nitrosomonas europaea and Nitrosococcus oceanus. Production of both gases increased relative to nitrite production as oxygen levels decreased

  8. Fundamentals and control of nitrification in chloraminated drinking water distribution systems

    National Research Council Canada - National Science Library

    American Water Works Association

    2006-01-01

    ... Introduction, 25 Nitrification in Drinking Water Distribution System, 25 Nitrification in Pipelines and Effects of Biofilms, 31 Nitrification in Water Storage Facilities, 34 Conclusions, 39 Refere...

  9. Trends in readmission rates for safety net hospitals and non-safety net hospitals in the era of the US Hospital Readmission Reduction Program: a retrospective time series analysis using Medicare administrative claims data from 2008 to 2015.

    Science.gov (United States)

    Salerno, Amy M; Horwitz, Leora I; Kwon, Ji Young; Herrin, Jeph; Grady, Jacqueline N; Lin, Zhenqiu; Ross, Joseph S; Bernheim, Susannah M

    2017-07-13

    To compare trends in readmission rates among safety net and non-safety net hospitals under the US Hospital Readmission Reduction Program (HRRP). A retrospective time series analysis using Medicare administrative claims data from January 2008 to June 2015. We examined 3254 US hospitals eligible for penalties under the HRRP, categorised as safety net or non-safety net hospitals based on the hospital's proportion of patients with low socioeconomic status. Admissions for Medicare fee-for-service patients, age ≥65 years, discharged alive, who had a valid five-digit zip code and did not have a principal discharge diagnosis of cancer or psychiatric illness were included, for a total of 52 516 213 index admissions. Mean hospital-level, all-condition, 30-day risk-adjusted standardised unplanned readmission rate, measured quarterly, along with quarterly rate of change, and an interrupted time series examining: April-June 2010, after HRRP was passed, and October-December 2012, after HRRP penalties were implemented. 58.0% (SD 15.3) of safety net hospitals and 17.1% (SD 10.4) of non-safety net hospitals' patients were in the lowest quartile of socioeconomic status. The mean safety net hospital standardised readmission rate declined from 17.0% (SD 3.7) to 13.6% (SD 3.6), whereas the mean non-safety net hospital declined from 15.4% (SD 3.0) to 12.7% (SD 2.5). The absolute difference in rates between safety net and non-safety net hospitals declined from 1.6% (95% CI 1.3 to 1.9) to 0.9% (0.7 to 1.2). The quarterly decline in standardised readmission rates was 0.03 percentage points (95% CI 0.03 to 0.02, preadmission rates for safety net hospitals have decreased more rapidly than those for non-safety net hospitals. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  10. Effect of acid orange 7 on nitrification process

    Energy Technology Data Exchange (ETDEWEB)

    He, Yongjie (ManTech Environmental Tech., Inc., Dayton, OH (United States)); Bishop, P.L. (Univ. of Cincinnati, OH (United States). Dept. of Civil and Environmental Engineering)

    The effect of Acid Orange 7 (AO7), an azo dye commonly used in textile, pharmaceutical, food, and cosmetic industries, on the nitrification process is studied using completely stirred tank reactors (CSTR) and batch treatment systems. Azo dyes are of concern because many of the dyes or their metabolic intermediates are carcinogenic. AO7 biodegradation is found to be essentially complete when solids retention times (SRT) are maintained above 7.5 days, but systems with lower SRTs are unstable. It is shown that AO7 inhibits all stages of the nitrification process. Nitrite oxidizers are found to be more sensitive to AO7 than ammonium oxidizers. The results of kinetic studies indicate that the inhibition of ammonium oxidation is typified by noncompetitive inhibition; the presence of AO7 decreases the maximum substrate utilization rate and very slightly increases K[sub s], the half-saturation constant. AO7 is found to be less toxic to nitrification than some metal and phenolic compounds, but more toxic than some common organic compounds such as formalin, methanol, or acetone.

  11. Empirical evidence reveals seasonally dependent reduction in nitrification in coastal sediments subjected to near future ocean acidification

    NARCIS (Netherlands)

    Braeckman, U.; Van Colen, C.; Guilini, K.; Van Gansbeke, D.; Soetaert, K.; Vincx, M.; Vanaverbeke, J.

    2014-01-01

    Research so far has provided little evidence that benthic biogeochemical cycling is affected by ocean acidification under realistic climate change scenarios. We measured nutrient exchange and sediment community oxygen consumption (SCOC) rates to estimate nitrification in natural coastal permeable

  12. A Configurable Event-Driven Convolutional Node with Rate Saturation Mechanism for Modular ConvNet Systems Implementation

    Science.gov (United States)

    Camuñas-Mesa, Luis A.; Domínguez-Cordero, Yaisel L.; Linares-Barranco, Alejandro; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabé

    2018-01-01

    Convolutional Neural Networks (ConvNets) are a particular type of neural network often used for many applications like image recognition, video analysis or natural language processing. They are inspired by the human brain, following a specific organization of the connectivity pattern between layers of neurons known as receptive field. These networks have been traditionally implemented in software, but they are becoming more computationally expensive as they scale up, having limitations for real-time processing of high-speed stimuli. On the other hand, hardware implementations show difficulties to be used for different applications, due to their reduced flexibility. In this paper, we propose a fully configurable event-driven convolutional node with rate saturation mechanism that can be used to implement arbitrary ConvNets on FPGAs. This node includes a convolutional processing unit and a routing element which allows to build large 2D arrays where any multilayer structure can be implemented. The rate saturation mechanism emulates the refractory behavior in biological neurons, guaranteeing a minimum separation in time between consecutive events. A 4-layer ConvNet with 22 convolutional nodes trained for poker card symbol recognition has been implemented in a Spartan6 FPGA. This network has been tested with a stimulus where 40 poker cards were observed by a Dynamic Vision Sensor (DVS) in 1 s time. Different slow-down factors were applied to characterize the behavior of the system for high speed processing. For slow stimulus play-back, a 96% recognition rate is obtained with a power consumption of 0.85 mW. At maximum play-back speed, a traffic control mechanism downsamples the input stimulus, obtaining a recognition rate above 63% when less than 20% of the input events are processed, demonstrating the robustness of the network. PMID:29515349

  13. A Configurable Event-Driven Convolutional Node with Rate Saturation Mechanism for Modular ConvNet Systems Implementation

    Directory of Open Access Journals (Sweden)

    Luis A. Camuñas-Mesa

    2018-02-01

    Full Text Available Convolutional Neural Networks (ConvNets are a particular type of neural network often used for many applications like image recognition, video analysis or natural language processing. They are inspired by the human brain, following a specific organization of the connectivity pattern between layers of neurons known as receptive field. These networks have been traditionally implemented in software, but they are becoming more computationally expensive as they scale up, having limitations for real-time processing of high-speed stimuli. On the other hand, hardware implementations show difficulties to be used for different applications, due to their reduced flexibility. In this paper, we propose a fully configurable event-driven convolutional node with rate saturation mechanism that can be used to implement arbitrary ConvNets on FPGAs. This node includes a convolutional processing unit and a routing element which allows to build large 2D arrays where any multilayer structure can be implemented. The rate saturation mechanism emulates the refractory behavior in biological neurons, guaranteeing a minimum separation in time between consecutive events. A 4-layer ConvNet with 22 convolutional nodes trained for poker card symbol recognition has been implemented in a Spartan6 FPGA. This network has been tested with a stimulus where 40 poker cards were observed by a Dynamic Vision Sensor (DVS in 1 s time. Different slow-down factors were applied to characterize the behavior of the system for high speed processing. For slow stimulus play-back, a 96% recognition rate is obtained with a power consumption of 0.85 mW. At maximum play-back speed, a traffic control mechanism downsamples the input stimulus, obtaining a recognition rate above 63% when less than 20% of the input events are processed, demonstrating the robustness of the network.

  14. A Configurable Event-Driven Convolutional Node with Rate Saturation Mechanism for Modular ConvNet Systems Implementation.

    Science.gov (United States)

    Camuñas-Mesa, Luis A; Domínguez-Cordero, Yaisel L; Linares-Barranco, Alejandro; Serrano-Gotarredona, Teresa; Linares-Barranco, Bernabé

    2018-01-01

    Convolutional Neural Networks (ConvNets) are a particular type of neural network often used for many applications like image recognition, video analysis or natural language processing. They are inspired by the human brain, following a specific organization of the connectivity pattern between layers of neurons known as receptive field. These networks have been traditionally implemented in software, but they are becoming more computationally expensive as they scale up, having limitations for real-time processing of high-speed stimuli. On the other hand, hardware implementations show difficulties to be used for different applications, due to their reduced flexibility. In this paper, we propose a fully configurable event-driven convolutional node with rate saturation mechanism that can be used to implement arbitrary ConvNets on FPGAs. This node includes a convolutional processing unit and a routing element which allows to build large 2D arrays where any multilayer structure can be implemented. The rate saturation mechanism emulates the refractory behavior in biological neurons, guaranteeing a minimum separation in time between consecutive events. A 4-layer ConvNet with 22 convolutional nodes trained for poker card symbol recognition has been implemented in a Spartan6 FPGA. This network has been tested with a stimulus where 40 poker cards were observed by a Dynamic Vision Sensor (DVS) in 1 s time. Different slow-down factors were applied to characterize the behavior of the system for high speed processing. For slow stimulus play-back, a 96% recognition rate is obtained with a power consumption of 0.85 mW. At maximum play-back speed, a traffic control mechanism downsamples the input stimulus, obtaining a recognition rate above 63% when less than 20% of the input events are processed, demonstrating the robustness of the network.

  15. Nitrification in Chloraminated Drinking Water Distribution Systems: Factors Affecting Occurrence

    Science.gov (United States)

    Drinking water distribution systems with ammonia present from either naturally occurring ammonia or ammonia addition during chloramination are at risk for nitrification. Nitrification in drinking water distribution systems is undesirable and may result in water quality degradatio...

  16. Nitrification in Chloraminated Drinking Water Distribution Systems - Occurrence

    Science.gov (United States)

    This chapter discusses available information on nitrification occurrence in drinking water chloraminated distribution systems. Chapter 4 provides an introduction to causes and controls for nitrification in chloraminated drinking water systems. Both chapters are intended to serve ...

  17. Magnetic sheath effect on the gross and net erosion rates due to impurities

    Science.gov (United States)

    Mellet, N.; Pégourié, B.; Martin, C.; Gunn, J. P.; Bufferand, H.; Roubin, P.

    2016-02-01

    Simulations of impurity trajectories in deuterium plasmas in the vicinity of the surface are performed by taking into account the magnetic sheath in conditions relevant for ITER and WEST. We show that the magnetic sheath has a strong effect on the average impact angle of impurities in divertor conditions and that it can lead to an increase of ≈ 60% at the gross erosion maximum for neon (Ne+4) compared to the case when only the cyclotron motion is considered. The evaluation of the net erosion has been undertaken by retaining local redeposition of tungsten (W). We investigate how it is affected by the sheath magnetic potential profile. The largest effect is however observed when an energy distribution is considered. In this case the number of particles that manage to exit the sheath is larger as it is dominated by the more energetic particles. The comparison with other work is also discussed. The application to a scenario of the WEST project is finally performed, which exhibits a moderate, however non negligible, erosion of the plasma facing components.

  18. Methods for measuring specific rates of mercury methylation and degradation and their use in determining factors controlling net rates of mercury methylation

    International Nuclear Information System (INIS)

    Ramlal, P.S.; Rudd, J.W.M.; Hecky, R.E.

    1986-01-01

    A method was developed to estimate specific rates of demethylation of methyl mercury in aquatic samples by measuring the volatile 14 C end products of 14 CH 3 HgI demethylation. This method was used in conjuction with a 203 Hg 2+ radiochemical method which determines specific rates of mercury methylation. Together, these methods enabled us to examine some factors controlling the net rate of mercury methylation. The methodologies were field tested, using lake sediment samples from a recently flooded reservoir in the Southern Indian Lake system which had developed a mercury contamination problem in fish. Ratios of the specific rates of methylation/demethylation were calculated. The highest ratios of methylation/demethylation were calculated. The highest ratios of methylation/demethylation occurred in the flooded shorelines of Southern Indian Lake. These results provide an explanation for the observed increases in the methyl mercury concentrations in fish after flooding

  19. Development of a simultaneous partial nitrification and anaerobic ammonia oxidation process in a single reactor.

    Science.gov (United States)

    Cho, Sunja; Fujii, Naoki; Lee, Taeho; Okabe, Satoshi

    2011-01-01

    Up-flow oxygen-controlled biofilm reactors equipped with a non-woven fabric support were used as a single reactor system for autotrophic nitrogen removal based on a combined partial nitrification and anaerobic ammonium oxidation (anammox) reaction. The up-flow biofilm reactors were initiated as either a partial nitrifying reactor or an anammox reactor, respectively, and simultaneous partial nitrification and anammox was established by careful control of the aeration rate. The combined partial nitrification and anammox reaction was successfully developed in both biofilm reactors without additional biomass inoculation. The reactor initiated as the anammox reactor gave a slightly higher and more stable mean nitrogen removal rate of 0.35 (±0.19) kg-N m(-3) d(-1) than the reactor initiated as the partial nitrifying reactor (0.23 (±0.16) kg-N m(-3) d(-1)). FISH analysis revealed that the biofilm in the reactor started as the anammox reactor were composed of anammox bacteria located in inner anoxic layers that were surrounded by surface aerobic AOB layers, whereas AOB and anammox bacteria were mixed without a distinguishable niche in the biofilm in the reactor started as the partial nitrifying reactor. However, it was difficult to efficiently maintain the stable partial nitrification owing to inefficient aeration in the reactor, which is a key to development of the combined partial nitrification and anammox reaction in a single biofilm reactor. Copyright © 2010 Elsevier Ltd. All rights reserved.

  20. Comparison of net photosynthetic rate and 14C distribution between different cultural conditions on double cropping rice

    International Nuclear Information System (INIS)

    Huang Jianliang; Li Hesong; Zou Yingbin; Tu Naimei; Li Jianhui

    2002-01-01

    By applying the cultural method 'Vigorous Root-Strong Stem-Heavy Panicle Cultural Method' (VSHM), the yield of double cropping rice reached 18000 kg/hm 2 in large area at Liling county, Hunan province. The net photosynthetic rate and 14 C distribution of rice leaves between VSHM and traditional cultural methods (CK) were compared. The photosynthetic rate of the flag leaves at ripening stages under VSHM was higher than that of controls with both earlier rice or later rice. Regarding the net amount of 14 C-assimilate by a single flag leaf and the second top leaf, there were differences at the significant level of 0.01 and 0.05, respectively between VSHM and controls, and VSHM were 7.72%-35.05% higher. The percentage of distribution at panicles of 14 C-assimilate were 51.93%-61.40% when flag leaf was labelled, and 45.34%-54.25% when the second top leaf was labelled, that of earlier rice was higher than later rice respectively, but the differences were not significant between VSHM and CK. The actual yield of double cropping rice under the cultural condition of VSHM was 17710 kg/hm 2 , and increased by 18.33% when compared with controls

  1. Complete nitrification by a single microorganism

    DEFF Research Database (Denmark)

    van Kessel, Maartje A. H. J.; Speth, Daan R.; Albertsen, Mads

    2015-01-01

    Nitrification is a two-step process where ammonia is first oxidized to nitrite by ammonia-oxidizing bacteria and/or archaea, and subsequently to nitrate by nitrite-oxidizing bacteria. Already described by Winogradsky in 18901, this division of labour between the two functional groups is a general...

  2. Development of a Biochar-Plant-Extract-Based Nitrification Inhibitor and Its Application in Field Conditions

    Directory of Open Access Journals (Sweden)

    Jhónatan Reyes-Escobar

    2015-10-01

    Full Text Available The global use of nitrogen (N fertilizer has increased 10-fold in the last fifty years, resulting in increased N losses via nitrate leaching to groundwater bodies or from gaseous emissions to the atmosphere. One of the biggest problems farmers face in agricultural production systems is the loss of N. In this context, novel biological nitrification inhibitors (BNI using biochar (BC as a renewable matrix to increase N use efficiency, by reducing nitrification rates, have been evaluated. The chemical and morphological characteristics of BC were analyzed and BC-BNI complexes were formulated using plant extracts from pine (Pinus radiata, eucalyptus (Eucalyptus globulus and peumo (Cryptocarya alba. In field experiments, fertilizer and treatments, based on crude plant extracts and BC-BNI complexes, were applied and the effect on nitrification was periodically monitored, and at the laboratory level, a phytotoxicity assay was performed. The biochar-peumo (BCPe complex showed the highest nitrification inhibition (66% on day 60 after application compared with the crude plant extract, suggesting that BCPe complex protects the BNI against biotic or abiotic factors, and therefore BC-BNI complexes could increase the persistence of biological nitrification inhibitors. None of the biochar complexes had toxic effect on radish plants.

  3. Effects of silver nanoparticles on nitrification and associated nitrous oxide production in aquatic environments.

    Science.gov (United States)

    Zheng, Yanling; Hou, Lijun; Liu, Min; Newell, Silvia E; Yin, Guoyu; Yu, Chendi; Zhang, Hongli; Li, Xiaofei; Gao, Dengzhou; Gao, Juan; Wang, Rong; Liu, Cheng

    2017-08-01

    Silver nanoparticles (AgNPs) are the most common materials in nanotechnology-based consumer products globally. Because of the wide application of AgNPs, their potential environmental impact is currently a highly topical focus of concern. Nitrification is one of the processes in the nitrogen cycle most susceptible to AgNPs but the specific effects of AgNPs on nitrification in aquatic environments are not well understood. We report the influence of AgNPs on nitrification and associated nitrous oxide (N 2 O) production in estuarine sediments. AgNPs inhibited nitrification rates, which decreased exponentially with increasing AgNP concentrations. The response of nitrifier N 2 O production to AgNPs exhibited low-dose stimulation (production could be enhanced by >100% at low doses of AgNPs. This result was confirmed by metatranscriptome studies showing up-regulation of nitric oxide reductase (norQ) gene expression in the low-dose treatment. Isotopomer analysis revealed that hydroxylamine oxidation was the main N 2 O production pathway, and its contribution to N 2 O emission was enhanced when exposed to low-dose AgNPs. This study highlights the molecular underpinnings of the effects of AgNPs on nitrification activity and demonstrates that the release of AgNPs into the environment should be controlled because they interfere with nitrifying communities and stimulate N 2 O emission.

  4. Use of 15N in nitrification inhibitor studies with special reference to indigenous materials

    International Nuclear Information System (INIS)

    Sahrawat, K.L.

    1988-01-01

    Non-edible oil seed cakes and their constituents have been advantageously used for increasing the efficiency of fertilizer nitrogen (N) for crop production. The beneficial effects of these materials have been attributed to retardation of nitrification, which lessen the loss of N associated with nitrification by leaching and denitrification in situations where these losses are high. However, it is possible that some of the effects of these materials could be due to immobilization-remineralization of N particularly when the carbonaceous materials are added with fertilizers at high rates. A methodology involving the use of 15 N-labelled fertilizers is advanced to sort out whether the beneficial effects of non-edible oil seed cakes and other materials are due to retardation of nitrification and or immobilization-remineralization of fertilizer N. Using the proposed technique it would be possible to make realistic evaluation of the wealth of indigenous products as nitrification inhibitors. Following the proposed approach it would also be possible to widen the scope and depth of research in this area for ultimately better exploitation of indigenous materials as nitrification inhibitors. (author). 18 refs

  5. A New Approach for Mobile Advertising Click-Through Rate Estimation Based on Deep Belief Nets

    OpenAIRE

    Chen, Jie-Hao; Zhao, Zi-Qian; Shi, Ji-Yun; Zhao, Chong

    2017-01-01

    In recent years, with the rapid development of mobile Internet and its business applications, mobile advertising Click-Through Rate (CTR) estimation has become a hot research direction in the field of computational advertising, which is used to achieve accurate advertisement delivery for the best benefits in the three-side game between media, advertisers, and audiences. Current research on the estimation of CTR mainly uses the methods and models of machine learning, such as linear model or re...

  6. Nitrification and ammonium dynamics in Taihu Lake, China: seasonal competition for ammonium between nitrifiers and cyanobacteria

    Science.gov (United States)

    Hampel, Justyna J.; McCarthy, Mark J.; Gardner, Wayne S.; Zhang, Lu; Xu, Hai; Zhu, Guangwei; Newell, Silvia E.

    2018-02-01

    Taihu Lake is hypereutrophic and experiences seasonal, cyanobacterial harmful algal blooms. These Microcystis blooms produce microcystin, a potent liver toxin, and are linked to anthropogenic nitrogen (N) and phosphorus (P) loads to lakes. Microcystis spp. cannot fix atmospheric N and must compete with ammonia-oxidizing and other organisms for ammonium (NH4+). We measured NH4+ regeneration and potential uptake rates and total nitrification using stable-isotope techniques. Nitrification studies included abundance of the functional gene for NH4+ oxidation, amoA, for ammonia-oxidizing archaea (AOA) and bacteria (AOB). Potential NH4+ uptake rates ranged from 0.02 to 6.80 µmol L-1 h-1 in the light and from 0.05 to 3.33 µmol L-1 h-1 in the dark, and NH4+ regeneration rates ranged from 0.03 to 2.37 µmol L-1 h-1. Nitrification rates exceeded previously reported rates in most freshwater systems. Total nitrification often exceeded 200 nmol L-1 d-1 and was > 1000 nmol L-1 d-1 at one station near a river discharge. AOA amoA gene copies were more abundant than AOB gene copies (p Internal NH4+ regeneration exceeded external N loading to the lake by a factor of 2 but was ultimately fueled by external N loads. Our results thus support the growing literature calling for watershed N loading reductions in concert with existing management of P loads.

  7. Increased Ratio of Electron Transport to Net Assimilation Rate Supports Elevated Isoprenoid Emission Rate in Eucalypts under Drought1[W][OPEN

    Science.gov (United States)

    Dani, Kaidala Ganesha Srikanta; Jamie, Ian McLeod; Prentice, Iain Colin; Atwell, Brian James

    2014-01-01

    Plants undergoing heat and low-CO2 stresses emit large amounts of volatile isoprenoids compared with those in stress-free conditions. One hypothesis posits that the balance between reducing power availability and its use in carbon assimilation determines constitutive isoprenoid emission rates in plants and potentially even their maximum emission capacity under brief periods of stress. To test this, we used abiotic stresses to manipulate the availability of reducing power. Specifically, we examined the effects of mild to severe drought on photosynthetic electron transport rate (ETR) and net carbon assimilation rate (NAR) and the relationship between estimated energy pools and constitutive volatile isoprenoid emission rates in two species of eucalypts: Eucalyptus occidentalis (drought tolerant) and Eucalyptus camaldulensis (drought sensitive). Isoprenoid emission rates were insensitive to mild drought, and the rates increased when the decline in NAR reached a certain species-specific threshold. ETR was sustained under drought and the ETR-NAR ratio increased, driving constitutive isoprenoid emission until severe drought caused carbon limitation of the methylerythritol phosphate pathway. The estimated residual reducing power unused for carbon assimilation, based on the energetic status model, significantly correlated with constitutive isoprenoid emission rates across gradients of drought (r2 > 0.8) and photorespiratory stress (r2 > 0.9). Carbon availability could critically limit emission rates under severe drought and photorespiratory stresses. Under most instances of moderate abiotic stress levels, increased isoprenoid emission rates compete with photorespiration for the residual reducing power not invested in carbon assimilation. A similar mechanism also explains the individual positive effects of low-CO2, heat, and drought stresses on isoprenoid emission. PMID:25139160

  8. Simplified modeling of simultaneous reaction kinetics of carbon oxidation and nitrification in biofilm processes

    Energy Technology Data Exchange (ETDEWEB)

    Tsuneda, S.; Auresenia, J.; Hibiya, K.; Hirata, A. [Waseda University, Department of Chemical Engineering, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555 (Japan)

    2004-06-01

    Batch experiments with varying initial substrate concentrations and biomass volumes were performed in a three-phase fluidized bed biofilm reactor treating simulated domestic wastewater to study the simultaneous carbon oxidation and nitrification in the biofilm process. A simplified mass balance equation for the biofilm was proposed and five different kinetic rate equations were used to match the actual data. The kinetic parameters were obtained by nonlinear regression analysis on a set of two differential equations representing the simultaneous carbon oxidation and nitrification. The competitive inhibition model incorporating the effects of total organic carbon (TOC) concentrations on nitrification rates was the best-suited model based on the average r{sup 2}. In this model, oxygen concentration and its affinity constants were not included. Instead, it was assumed that the rate of carbon oxidation is independent of the NH{sub 4}{sup +}-N, while nitrification is affected by TOC. The number of parameters was successfully minimized without reducing its ability to accurately predict the bulk concentration time course, which would reduce computational complexity and possibly enhance the availability for an actual wastewater treatment process. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  9. Uncertainties in the Value of Bill Savings from Behind-the-Meter, Residential Photovoltaic Systems: The Roles of Electricity Market Conditions, Retail Rate Design, and Net Metering

    Science.gov (United States)

    Darghouth, Naim Richard

    Net metering has become a widespread policy mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), allowing customers with PV systems to reduce their electric bills by offsetting their consumption with PV generation, independent of the timing of the generation relative to consumption. Although net metering is one of the principal drivers for the residential PV market in the U.S., the academic literature on this policy has been sparse and this dissertation contributes to this emerging body of literature. This dissertation explores the linkages between the availability of net metering, wholesale electricity market conditions, retail rates, and the residential bill savings from behind-the-meter PV systems. First, I examine the value of the bill savings that customers receive under net metering and alternatives to net metering, and the associated role of retail rate design, based on current rates and a sample of approximately two hundred residential customers of California's two largest electric utilities. I find that the bill savings per kWh of PV electricity generated varies greatly, largely attributable to the increasing block structure of the California utilities' residential retail rates. I also find that net metering provides significantly greater bill savings than alternative compensation mechanisms based on avoided costs. However, retail electricity rates may shift as wholesale electricity market conditions change. I then investigate a potential change in market conditions -- increased solar PV penetrations -- on wholesale prices in the short-term based on the merit-order effect. This demonstrates the potential price effects of changes in market conditions, but also points to a number of methodological shortcomings of this method, motivating my usage of a long-term capacity investment and economic dispatch model to examine wholesale price effects of various wholesale market scenarios in the subsequent analysis. By developing

  10. THE APPLICATION OF BŰHLMANN-STRAUB MODEL TO THE ESTIMATION OF NET PREMIUM RATES DEPENDING ON THE AGE OF THE INSURED IN THE MOTOR THIRD LIABILITY INSURANCE

    OpenAIRE

    Szymańska, Anna

    2017-01-01

    One of the basic variables used in the process of tariff calculation of premiums in motor liability insurance is the age of the insured. In this type of insurance offered by insurers operating on the Polish market, this variable is taken into account in the ratemaking by discounts and increases in assigned premium, known as the net premiums rates. The aim of this work is to propose a method of rate estimation of net premiums in the groups of the motor third liability insurance portfolio of in...

  11. Effect of adrenaline and alpha-agonists on net rate of liquid absorption from the pleural space of rabbits.

    Science.gov (United States)

    Zocchi, L; Raffaini, A; Agostoni, E

    1997-05-01

    Indirect evidence supporting a solute-coupled liquid absorption from the pleural space of rabbits has recently been provided; moreover, the beta 2-adrenoceptor agonist terbutaline has been found to increase this absorption. In this study the effect of adrenaline and alpha-adrenoceptor agonists on net rate of liquid absorption (Jnet) from albumin Ringer hydrothoraces of various sizes has been determined in anaesthetized rabbits. In hydrothoraces with adrenaline (5 x 10(-6) M) the relationship between Jnet and volume of liquid injected was displaced upwards by 0.09 ml h-1 relative to that in control hydrothoraces (P liquid absorption, since beta-agonists inhibit lymphatic activity while, at relatively high concentrations, they may increase active transport. Conversely, the strong stimulation of lymphatic alpha-receptors that should occur with adrenaline after beta-blockade may fail to increase lymphatic drainage, because it has been shown that the increase in contraction frequency of lymphatics may be balanced by the decrease in their stroke volume. Arterial blood pressure during the hydrothoraces with adrenaline was unchanged. In hydrothoraces with the alpha 2-agonist clonidine (5 x 10(-6) M; a less potent agent than adrenaline) the slope of the relationship between Jnet and volume injected increased by 26% (P liquid load. In hydrothoraces with the alpha 1-agonist phenylephrine (5 x 10(-6) or 10(-7) M) Jnet was simlar to control values.

  12. Modeled dosage-response relationship on the net photosynthetic rate for the sensitivity to acid rain of 21 plant species.

    Science.gov (United States)

    Deng, Shihuai; Gou, Shuzhen; Sun, Baiye; Lv, Wenlin; Li, Yuanwei; Peng, Hong; Xiao, Hong; Yang, Gang; Wang, Yingjun

    2012-08-01

    This study investigated the sensitivity of plant species to acid rain based on the modeled dosage-response relationship on the net photosynthetic rate (P (N)) of 21 types of plant species, subjected to the exposure of simulated acid rain (SAR) for 5 times during a period of 50 days. Variable responses of P (N) to SAR occurred depending on the type of plant. A majority (13 species) of the dosage-response relationship could be described by an S-shaped curve and be fitted with the Boltzmann model. Model fitting allowed quantitative evaluation of the dosage-response relationship and an accurate estimation of the EC(10), termed as the pH of the acid rain resulting in a P (N) 10 % lower than the reference value. The top 9 species (Camellia sasanqua, Cinnamomum camphora, etc. EC(10) ≤ 3.0) are highly endurable to very acid rain. The rare, relict plant Metasequoia glyptostroboides was the most sensitive species (EC(10) = 5.1) recommended for protection.

  13. [Temporal-spatial distribution of agricultural diffuse nitrogen pollution and relationship with soil respiration and nitrification].

    Science.gov (United States)

    Wei, Ouyang; Cai, Guan-Qing; Huang, Hao-Bo; Geng, Xiao-Jun

    2014-06-01

    The soil respiration, nitrification and denitrification processes play an important role on soil nitrogen transformation and diffuse nitrogen loading. These processes are also the chains for soil circle. In this study, the Zhegao watershed located north of Chaohu Lake was selected to explore the interactions of these processes with diffuse nitrogen pollution. The BaPS (Barometric Process Separation) was applied to analyze the soil respiration, nitrification and denitrification processes in farmland and forest. The SWAT (Soil and Water Assessment Tool) simulated the temporal and spatial pattern of diffuse nitrogen loading. As the expanding of farmland and higher level of fertilization, the yearly mean loading of diffuse nitrogen increased sustainably from 1980-1995 to 1996-2012. The monthly loading in 1996-2012 was also higher than that in the period of 1980-1995, which closely related to the precipitation. The statistical analysis indicated that there was a significant difference between two periods. The yearly averaged loading of the whole watershed in 1996-2012 was 10.40 kg x hm(-2), which was 8.10 kg x hm(-2) in 1980-1995. The variance analysis demonstrated that there was also a big difference between the spatial distributions of two periods. The forest soil had much higher soil respiration than the farmland soil. But the farmland had higher nitrification and denitrification rates. The more intensive nitrogen transformation in the farmland contributed to the less diffuse nitrogen loading. As the nitrification rate of farmland was higher than denitrification rate, agricultural diffuse nitrate nitrogen loading would increase and organic nitrogen loading would reduce. The analysis of soil respiration, nitrification and denitrification is helpful for the study of soil nitrogen circle form the aspect of soil biology, which also benefits the control of agricultural diffuse nitrogen pollution.

  14. Net CO2 exchange rates in three different successional stages of the 'Dark Taiga' of central Siberia

    International Nuclear Information System (INIS)

    Roeser, C.; Schulze, E.D.; Montagnani, L.

    2002-01-01

    The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taiga was measured in central Siberia (61 deg N, 90 deg E) during the growing season of the year 2000 using the eddy covariance technique. Measurements started before snow melt and canopy activity in spring on day of year (DOY) 99 and lasted until a permanent snow cover had developed and respiration had ceased in autumn DOY 299. Three stands growing in close vicinity were investigated: 50 yr-old Betula pubescens ('Betula stand', an early successional stage after fire), 250 yr-old mixed boreal forest, representing the transition from Betula-dominated to Abies-dominated canopies, and 200-yr-old Abies sibirica ('Abies stand', representing a late successional stage following the mixed boreal forest). The mixed boreal forest had a multi-layered canopy with dense under story and trees of variable height and age below the main canopy, which was dominated by Abies sibirica, Picea obovata and few old Betula pubescens and Populus tremula trees. The Abies stand had a uniform canopy dominated by Abies sibirica. This stand appears to have established not after fire but after wind break or insect damage in a later successional stage. The stands differed with respect to the number of days with net CO 2 uptake (Betula stand 89 days, mixed boreal forest 109 days, and Abies stand 135 days), maximum measured LAI (Betula 2.6 m 2 /m 2 , mixed boreal forest 3.5 m 2 /m 2 and Abies stand 4.1 m 2 /m 2 ) and basal area (Betula stand 30.2 m 2 /ha, mixed boreal forest 35.7 m 2 /ha, and Abies stand 46.5 m 2 /ha). In the mixed boreal forest, many days with net daytime CO 2 release were observed in summer. Both other sites were almost permanent sinks in summer. Mean daytime CO 2 exchange rates in July were 8.45 mol/m 2 /s in the Betula stand, 4.65 mol/m 2 /s in the mixed boreal forest and 6.31 mol/m 2 /s in the Abies stand. Measured uptake for the growing season was 247.2 g C/m 2 in the Betula stand, 99.7 g C/m 2

  15. Conditions and mechanisms affecting simultaneous nitrification and denitrification in a Pasveer oxidation ditch

    NARCIS (Netherlands)

    Hao, X.; Doddema, H.J.; Groenestijn, J.W. van

    1997-01-01

    Simultaneous nitrification and denitrification in a Pasveer oxidation ditch was studied. The purpose was to evaluate the performances of both nitrification and dentrification in oxidation ditches, and to pursue some possible approaches to enhance nitrogen removal. Almost complete nitrification was

  16. Nitrogen Removal Characteristics of Pseudomonas putida Y-9 Capable of Heterotrophic Nitrification and Aerobic Denitrification at Low Temperature

    Directory of Open Access Journals (Sweden)

    Yi Xu

    2017-01-01

    Full Text Available The cold-adapted bacterium Pseudomonas putida Y-9 was investigated and exhibited excellent capability for nitrogen removal at 15°C. The strain capable of heterotrophic nitrification and aerobic denitrification could efficiently remove ammonium, nitrate, and nitrite at an average removal rate of 2.85 mg, 1.60 mg, and 1.83 mg NL−1 h−1, respectively. Strain Y-9 performed nitrification in preference to denitrification when ammonium and nitrate or ammonium and nitrite coexisted in the solution. Meantime, the presence of nitrate had no effect on the ammonium removal rate of strain Y-9, and yet the presence of high concentration of nitrite would inhibit the cell growth and decrease the nitrification rate. The experimental results indicate that P. putida Y-9 has potential application for the treatment of wastewater containing high concentrations of ammonium along with its oxidation products at low temperature.

  17. [Effect of prescribed burning on grassland nitrogen gross mineralization and nitrification].

    Science.gov (United States)

    Li, Yuzhong; Zhu, Tingcheng; Li, Jiandong; Zhou, Daowei

    2003-02-01

    The seasonal dynamics of nitrogen gross mineralization, nitrification, and mineral nitrogen consumption rates in burned and unburned Leymus chinensis grasslands were studied with 15N pool dilution technique. The results indicated that the gross mineralization and nitrification rates in burned area were higher than those in unburned area in April and May, and lower than those in unburned area in September. NH4(+)-N consumption rates were higher than unburned area in April and May, and lower in September. NO3(-)-N consumption rates were higher than control in April and May, and lower than control in July and September. The NH4(+)-N concentrations were higher in burned area in April, May and July, and no difference in September. NO3(-)-N concentrations were no difference between burned and unburned areas in April and May, and higher in burned areas in July and September.

  18. Long-term influence of tillage and fertilization on net carbon dioxide exchange rate on two soils with different textures.

    Science.gov (United States)

    Feiziene, Dalia; Feiza, Virginijus; Slepetiene, Alvyra; Liaudanskiene, Inga; Kadziene, Grazina; Deveikyte, Irena; Vaideliene, Asta

    2011-01-01

    The importance of agricultural practices to greenhouse gas mitigation is examined worldwide. However, there is no consensus on soil organic carbon (SOC) content and CO emissions as affected by soil management practices and their relationships with soil texture. No-till (NT) agriculture often results in soil C gain, though, not always. Soil net CO exchange rate (NCER) and environmental factors (SOC, soil temperature [T], and water content [W]), as affected by soil type (loam and sandy loam), tillage (conventional, reduced, and NT), and fertilization, were quantified in long-term field experiments in Lithuania. Soil tillage and fertilization affected total CO flux (heterotrophic and autotrophic) through effect on soil SOC sequestration, water, and temperature regime. After 11 yr of different tillage and fertilization management, SOC content was 23% more in loam than in sandy loam. Long-term NT contributed to 7 to 27% more SOC sequestration on loam and to 29 to 33% more on sandy loam compared with reduced tillage (RT) or conventional tillage (CT). Soil water content in loam was 7% more than in sandy loam. Soil gravimetric water content, averaged across measurement dates and fertilization treatments, was significantly less in NT than CT and RT in both soils. Soil organic carbon content and water storage capacity of the loam and sandy loam soils exerted different influences on NCER. The NCER from the sandy loam soil was 13% greater than that from the loam. In addition, NCER was 4 to 9% less with NT than with CT and RT systems on both loam and sandy loam soils. Application of mineral NPK fertilizers promoted significantly greater NCER from loam but suppressed NCER by 15% from sandy loam. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  19. The inhibition of marine nitrification by ocean disposal of carbon dioxide

    International Nuclear Information System (INIS)

    Huesmann, M.H.; Skillman, A.D.; Crecelius, E.A.

    2002-01-01

    In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO 2 from the flue gases of fossil fuel-fired power plants. The release of large amounts of CO 2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8. In an effort to determine whether these CO 2 -induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO 2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique. For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH. Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca. 50% at pH 7 and more than 90% at pH 6.5. Nitrification was essentially completely inhibited at pH 6. These findings suggest that the disposal of CO 2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate. It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected. However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur. Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena. Clearly, more research on the

  20. Effect of arsenic on nitrification of simulated mining water.

    Science.gov (United States)

    Papirio, S; Zou, G; Ylinen, A; Di Capua, F; Pirozzi, F; Puhakka, J A

    2014-07-01

    Mining and mineral processing of gold-bearing ores often release arsenic to the environment. Ammonium is released when N-based explosives or cyanide are used. Nitrification of simulated As-rich mining waters was investigated in batch bioassays using nitrifying cultures enriched in a fluidized-bed reactor (FBR). Nitrification was maintained at 100mg AsTOT/L. In batch assays, ammonium was totally oxidized by the FBR enrichment in 48 h. As(III) oxidation to As(V) occurred during the first 3h attenuating arsenic toxicity to nitrification. At 150 and 200mg AsTOT/L, nitrification was inhibited by 25%. Candidatus Nitrospira defluvii and other nitrifying species mainly colonized the FBR. In conclusion, the FBR enriched cultures of municipal activated sludge origins tolerated high As concentrations making nitrification a potent process for mining water treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Remediation of incomplete nitrification and capacity increase of biofilters at different drinking water treatment plants through copper dosing

    DEFF Research Database (Denmark)

    Wagner, Florian Benedikt; Borch Nielsen, Peter; Boe-Hansen, Rasmus

    2018-01-01

    Drinking water treatment plants based on groundwater may suffer from incomplete ammonium removal, which deteriorates drinking water quality and constrains water utilities in the operation of their plants. Ammonium is normally removed through nitrification in biological granular media filters...... groundwater treatment plants, all of which had displayed several years of incomplete nitrification. Plants exceeded the Danish national water quality standard of 0.05 mg NH4+/L by a factor of 2–12. Within only 2-3 weeks of dosing, ammonium removal rates increased significantly (up to 150%). Nitrification...... was fully established, with ammonium effluent concentrations of water chemistry, ammonium loading rates, filter design and operation, or treatment plant configuration. However, for filters without primary filtration, it took longer time...

  2. Oxygen Isotope Composition of Nitrate Produced by Freshwater Nitrification

    Science.gov (United States)

    Boshers, D.; Granger, J.; Bohlke, J. K.

    2016-12-01

    Measurements of the naturally occurring nitrogen and oxygen stable isotope ratios of nitrate (NO3-), δ15N and δ18O, can be used to determine the source, dispersal, and fate of natural and contaminant NO3- in aquatic environments. To this end, it is necessary to know the extent to which NO3- isotopologues are modified by biological reactions, as heavy and light isotopes have different reaction rates. The purpose of this study was to determine the influence of the δ18O of ambient water on the isotope composition of NO3- produced during nitrification, the biological oxidation of ammonium (NH4+) to nitrite (NO2-) and then NO3-, which is poorly constrained in freshwater systems. To determine the δ18O of NO3- produced by nitrification in freshwater, we collected water from a stream in New England, which we amended with NH4+ and with increments of 18O-enriched water, to monitor the isotope composition of NO3- produced by a natural consortium of nitrifiers. Added NH4+ was completely oxidized to NO3- over 26 days. The final δ18O of nitrified NO3- revealed sensitivity to the δ18O of water mediated by (a) isotopic equilibration between water and NO2- and (b) kinetic isotope fractionation during O-atom incorporation from water into NO2- and NO3-. Our results concur with nitrifying culture experiments that have demonstrated analogous sensitivity of the δ18O of nitrified NO3- to equilibrium and kinetic O isotope effects (Buchwald et al. 2012), as well as show that these dynamics need to be considered to interpret NO3- isotope distribution in freshwater environments.

  3. [Effects of plastic film mulching and nitrogen application rate on net global warming potential in semiarid rain-fed maize cropland].

    Science.gov (United States)

    Liu, Jian Can; Wang, Ze Lin; Yue, Shan Chao; Li, Shi Qing

    2018-04-01

    A one-year field experiment was conducted to evaluate the effects of plastic film mulching (FM) and nitrogen application rates applied to rain-fed maize fields on net global warming potential (Net GWP) and greenhouse gas intensity (GHGI) at the Changwu Agricultural and Ecological Experimental Station. Both GWP and GHGI were affected by the plastic film mulching and nitrogen application rate. Under the FM treatment, maize yield ranged from 1643 to 16699 kg·hm -2 , the net GWP (CO 2 -eq) ranged from 595 to 4376 kg·hm -2 ·a -1 , and the GHGI (CO 2 -eq) ranged from 213 to 358 kg·t -1 . The grain yield of maize, net GWP and GHGI for the UM (no mulching) treatment were 956 to 8821 kg·hm -2 , 342 to 4004 kg·hm -2 ·a -1 and 204 to 520 kg·t -1 , respectively. The results suggested that plastic film mulching could simultaneously improve grain yield and decrease GHGI in rain-fed cropland along with nitrogen fertilizer of 250 kg·hm -2 .

  4. Bioassays for the determination of nitrification inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Grunditz, Camilla

    1999-07-01

    Requirements for nitrogen reduction in wastewater treatment plants were introduced in Sweden in the early 1990's. This was a governmental move to reduce the nitrogen discharges to the Baltic and Kattegat in order to prevent eutrophication. The nitrification process in wastewater treatment plants is performed by nitrifying bacteria. These are susceptible to inhibition and it is of great importance that the influent water does not contain toxic compounds. Therefore, there is a need for assays for the determination of nitrification inhibition. This thesis describes the development and applications of such bioassays. Pure cultures of Nitrosomonas sp. and Nitrobacter sp. were isolated from activated sludge of a wastewater treatment plant. These cultures were used as test organisms in the development of bioassays for nitrification inhibition measurements. The assays are based on two different principles; cell suspensions of the bacteria, performed in test tubes, and mediated amperometric biosensors with the bacteria immobilised. Ammonia oxidation and nitrite oxidation are studied separately without interference from other organisms, which makes it easier to interpret the results. The cell suspension assays were applied to samples of industrial and municipal wastewater. The Nitrosomonas and Nitrobacter assays showed to have different inhibition patterns. A large percentage of the Swedish municipal wastewater treatment plants were found to receive inhibitory influent water, but the inhibition level was generally low. Compared to an assay based on activated sludge, the screening method, the pure culture assays found more samples of influent water strongly inhibitory or stimulating. The highest correlation was found between the screening method and the Nitrosomonas assay. The Nitrobacter assay was found to be the most sensitive method. Assessment of toxicity of a number of chemical substances was studied using the biosensors, together with the cell suspension assays

  5. Revisiting nitrification in the Eastern Tropical South Pacific: A focus on controls

    Science.gov (United States)

    Peng, Xuefeng; Fuchsman, Clara A.; Jayakumar, Amal; Warner, Mark J.; Devol, Allan H.; Ward, Bess B.

    2016-03-01

    Nitrification, the oxidation of ammonium (NH4+) to nitrite (NO2-) and to nitrate (NO3-), is a component of the nitrogen (N) cycle internal to the fixed N pool. In oxygen minimum zones (OMZs), which are hotspots for oceanic fixed N loss, nitrification plays a key role because it directly supplies substrates for denitrification and anaerobic ammonia oxidation (anammox), and may compete for substrates with these same processes. However, the control of oxygen and substrate concentrations on nitrification are not well understood. We performed onboard incubations with 15N-labeled substrates to measure rates of NH4+ and NO2- oxidation in the eastern tropical South Pacific (ETSP). The spatial and depth distributions of NH4+ and NO2- oxidation rates were primarily controlled by NH4+ and NO2- availability, oxygen concentration, and light. In the euphotic zone, nitrification was partially photoinhibited. In the anoxic layer, NH4+ oxidation was negligible or below detection, but high rates of NO2- oxidation were observed. NH4+ oxidation displayed extremely high affinity for both NH4+ and oxygen. The positive linear correlations between NH4+ oxidation rates and in situ NH4+ concentrations and ammonia monooxygenase subunit A (amoA) gene abundances in the upper oxycline indicate that the natural assemblage of ammonia oxidizers responds to in situNH4+ concentrations or supply by adjusting their population size, which determines the NH4+ oxidation potential. The depth distribution of archaeal and bacterial amoA gene abundances and N2O concentration, along with independently reported simultaneous direct N2O production rate measurements, suggests that AOA were predominantly responsible for NH4+ oxidation, which was a major source of N2O production at oxygen concentrations > 5 µM.

  6. Nitrification of highly contaminated waste water with retention of biomass

    International Nuclear Information System (INIS)

    Weichgrebe, D.

    1992-09-01

    The AIF Research Project No 7698 was concerned with the nitrification of highly contaminated waste water with retention of biomass. A compact system for the nitrification was developed and optimized in the investigations. This is an over-dammed fixed bed reactor with structured packing elements and membrane gasification. The fixed bed reactor was successfully installed in a multi-stage compact plant on the laboratory scale for the biological treatment of dump trickled water. With the conclusion of the investigations, design data are available for the technical scale realisation of nitrification in fixed bed reactors. (orig.) [de

  7. Nitrification and in-situ uranium solution mining

    International Nuclear Information System (INIS)

    Johnson, D.; Humenick, M.J.

    1980-01-01

    The objective of this research was to determine the potential for conversion of ammonia to nitrate as a result of uranium solution mining operations. The work included literature evaluation and laboratory experimentation in both batch and continuous systems. Results indicate that a potential for nitrification could exist for some portions of the solution mining operating cycle. However, inhibition of nitrification was observed due to high ammonia and peroxide concentrations. Nitrification of ammonia also was observed to occur due to chemical oxidation by peroxide. 28 refs

  8. From Partial nitrification to canon in an aerobic granular SBR

    International Nuclear Information System (INIS)

    Vazquez-Padin, J.; Figueroa, M.; Campos, J. L.; Mosquera-Corral, A.; Mendez, R.

    2009-01-01

    Nitrogen removal via nitrification-denitrification processes is commonly used in biology wastewater treatment plants to remove nitrogen compounds. In recent years new technologies emerged bringing solutions to remove nitrogen from wastewaters with not enough COD content to complete the denitrification process. An alternative strategy to the conventional nitrification-denitrification processes has been developed in the nine tries consisting of a combination of the oxidation of half of the ammonium from the wastewater to nitrite via partial nitrification and the removal of both, ammonium and formed nitrite by the Anammox process. (Author)

  9. Effect of temperate climate tree species on gross ammonification, gross nitrification and N2O formation

    Science.gov (United States)

    Brüggemann, N.; Rosenkranz, P.; Papen, H.; Butterbach-Bahl, K.

    2003-04-01

    Microbial nitrogen turnover processes in the soil, like ammonification, nitrification and denitrification, play an important role in the formation of nitrous oxide (N2O): (i) ammonification, because it releases nitrogen from organic material in the form of ammonium (NH4+), which in turn can serve as substrate for nitrification; (ii) nitrification itself (i.e. the turnover of NH4+ to nitrate, NO3-), during which nitric oxide (NO) and N2O can be released as by-products at varying ratios; (iii) denitrification, in which NO3- serves as electron acceptor and is converted to molecular nitrogen (N2) via NO and N2O as intermediates, that can also be partially lost to the atmosphere. Temperate forest soils are a substantial source of atmospheric N2O contributing up to 10% to the total atmospheric N2O budget. However, this figure is afflicted with a huge uncertainty due to a number of factors governing the soil N2O formation, consumption, release and uptake, which are not fully understood at present. To one of these factors belongs the influence of the tree species on nitrogen turnover processes in the soil and the formation of N trace gases related with them. The aim of the present work was to analyse this tree species effect for the temperate climate region. For this purpose the effect of five different temperate tree species, having the same age and growing on the same soil in direct vicinity to each other, on gross ammonification and gross nitrification as well as on N2O formation was investigated. The trees (common beech, Fagus sylvatica; pedunculate oak, Quercus robur; Norway spruce, Picea abies; Japanese larch, Larix leptolepis; mountain pine, Pinus mugo) were part of a species trial in Western Jutland, Denmark, established in 1965 on a former sandy heathland. Samples from the soil under these five tree species were taken in spring and in summer 2002, respectively, differentiating between organic layer and mineral soil. The gross rates of ammonification as well of

  10. Are HPV vaccination services accessible to high-risk communities? A spatial analysis of HPV-associated cancer and Chlamydia rates and safety-net clinics.

    Science.gov (United States)

    Tsui, Jennifer; Rodriguez, Hector P; Gee, Gilbert C; Escobedo, Loraine A; Kominski, Gerald F; Bastani, Roshan

    2013-12-01

    While HPV vaccines can greatly benefit adolescents and young women from high-risk areas, little is known about whether safety-net immunization services are geographically accessible to communities at greatest risk for HPV-associated diseases. We explore the spatial relationship between areas with high HPV risk and proximity to safety-net clinics from an ecologic perspective. We used cancer registry data and Chlamydia surveillance data to identify neighborhoods within Los Angeles County with high risk for HPV-associated cancers. We examined proximity to safety-net clinics among neighborhoods with the highest risk. Proximity was measured as the shortest distance between each neighborhood center and the nearest clinic and having a clinic within 3 miles of each neighborhood center. The average 5-year non-age-adjusted rates were 1,940 cases per 100,000 for Chlamydia and 60 per 100,000 for HPV-associated cancers. A large majority, 349 of 386 neighborhoods with high HPV-associated cancer rates and 532 of 537 neighborhoods with high Chlamydia rates, had a clinic within 3 miles of the neighborhood center. Clinics were more likely to be located within close proximity to high-risk neighborhoods in the inner city. High-risk neighborhoods outside of this urban core area were less likely to be near accessible clinics. The majority of high-risk neighborhoods were geographically near safety-net clinics with HPV vaccination services. Due to low rates of vaccination, these findings suggest that while services are geographically accessible, additional efforts are needed to improve uptake. Programs aimed to increase awareness about the vaccine and to link underserved groups to vaccination services are warranted.

  11. Nitrous oxide production by nitrification and denitrification in the Eastern Tropical South Pacific oxygen minimum zone

    Science.gov (United States)

    Ji, Qixing; Babbin, Andrew R.; Jayakumar, Amal; Oleynik, Sergey; Ward, Bess B.

    2015-12-01

    The Eastern Tropical South Pacific oxygen minimum zone (ETSP-OMZ) is a site of intense nitrous oxide (N2O) flux to the atmosphere. This flux results from production of N2O by nitrification and denitrification, but the contribution of the two processes is unknown. The rates of these pathways and their distributions were measured directly using 15N tracers. The highest N2O production rates occurred at the depth of peak N2O concentrations at the oxic-anoxic interface above the oxygen deficient zone (ODZ) because slightly oxygenated waters allowed (1) N2O production from both nitrification and denitrification and (2) higher nitrous oxide production yields from nitrification. Within the ODZ proper (i.e., anoxia), the only source of N2O was denitrification (i.e., nitrite and nitrate reduction), the rates of which were reflected in the abundance of nirS genes (encoding nitrite reductase). Overall, denitrification was the dominant pathway contributing the N2O production in the ETSP-OMZ.

  12. Petri Nets

    Indian Academy of Sciences (India)

    In a computer system, for example, typical discrete events ... This project brought out a series of influential reports on Petri net theory in the mid and late ... Technology became a leading centre for Petri net research and from then on, Petri nets ...

  13. WATER QUALITY AND ITS EFFECT ON GROWTH AND SURVIVAL RATE OF LOBSTER REARED IN FLOATING NET CAGE IN EKAS BAY, WEST NUSA TENGGARA PROVINCE

    Directory of Open Access Journals (Sweden)

    Muhammad Junaidi

    2015-02-01

    Full Text Available ABSTRACT The development of lobster farming in floating net cage in Ekas Bay caused an environmental degradation such as decrease water quality due to some aquaculture wastes. The purposes of this study were to determine the status of water quality and their effect on growth and survival rate of lobster reared in floating net cages (FNC in the Ekas Bay, West Nusa Tenggara Province. Water sample collection and handling referred to the APHA (1992. Analyses of water quality data were conducted using Principal Component Analysis. Determination of the water quality status of Ekas Bay was performed with STORET system. Multivariate analyses were used to determine the relationship between water quality, growth, and survival rate of lobster reared in FNC. Results showed that Ekas Bay water quality status was categorized in class C (medium contaminated, which exceeded some quality standard parameters such as ammonia (0.3 mg/l, nitrate (0.008 mg/l, and phosphate (0.015 mg/l. During lobster farming activities feeding with trash fish for 270 days, we obtained daily growth rate of  0.74% (lower than normal growth rate of 0.86%, survival rate of 66% (lower than normal survival rate of 86.7%, and feed conversion ratio of 11.15. Ammonia was found as a dominant factor reducing growth  and survival rate of lobster reared in FNC. Keywords: water quality, lobsters, growth, survival, Ekas Bay

  14. Nitrous oxide production during nitrification from organic solid waste under temperature and oxygen conditions.

    Science.gov (United States)

    Nag, Mitali; Shimaoka, Takayuki; Komiya, Teppei

    2016-11-01

    Landfill aeration can accelerate the biological degradation of organic waste and reduce methane production; however, it induces nitrous oxide (N2O), a potent greenhouse gas. Nitrification is one of the pathways of N2O generation as a by-product during aerobic condition. This study was initiated to demonstrate the features of N2O production rate from organic solid waste during nitrification under three different temperatures (20°C, 30°C, and 40°C) and three oxygen concentrations (5%, 10%, and 20%) with high moisture content and high substrates' concentration. The experiment was carried out by batch experiment using Erlenmeyer flasks incubated in a shaking water bath for 72 h. A duplicate experiment was carried out in parallel, with addition of 100 Pa of acetylene as a nitrification inhibitor, to investigate nitrifiers' contribution to N2O production. The production rate of N2O ranged between 0.40 × 10(-3) and 1.14 × 10(-3) mg N/g-DM/h under the experimental conditions of this study. The rate of N2O production at 40°C was higher than at 20°C and 30°C. Nitrification was found to be the dominant pathway of N2O production. It was evaluated that optimization of O2 content is one of the crucial parameters in N2O production that may help to minimize greenhouse gas emissions and N turnover during aeration.

  15. Influence of dissolved oxygen on the nitrification kinetics in a circulating bed biofilm reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, R.; Melo, L.F. [University of Minho, Braga (Portugal). Dept. Bioengineering; Lazarova, V.; Manem, J. [Centre of International Research for Water and Environment (CIRSEE), Lyonnaise des Eaux, Le Pecq (France)

    1998-12-01

    The influence of dissolved oxygen concentration on the nitrification kinetics was studied in the circulating bed reactor (CBR). The study was partly performed at laboratory scale with synthetic water, and partly at pilot scale with secondary effluent as feed water. The nitrification kinetics of the laboratory CBR as a function of the oxygen concentration can be described according to the half order and zero order rate equations of the diffusion-reaction model applied to porous catalysts. When oxygen was the rate limiting substrate, the nitrification rate was close to a half order function of the oxygen concentration. The average oxygen diffusion coefficient estimated by fitting the diffusion-reaction model to the experimental results was around 66% of the respective value in water. The experimental results showed that either the ammonia or the oxygen concentration could be limiting for the nitrification kinetics. The latter occurred for an oxygen to ammonia concentration ratio below 1.5-2 gO{sub 2}/gN-NH{sub 4}{sup +} for both laboratory and pilot scale reactors. The volumetric oxygen mass transfer coefficient (k{sub L}a) determined in the laboratory scale reactor was 0.017 s{sup -1} for a superficial air velocity of 0.02 m s{sup -1}, and the one determined in the pilot scale reactor was 0.040 s{sup -1} for a superficial air velocity of 0.031 m s{sup -1}. The k{sub L}a for the pilot scale reactor did not change significantly after biofilm development, compared to the value measured without biofilm. (orig.) With 7 figs., 5 tabs., 24 refs.

  16. Inhibitory effect of cyanide on wastewater nitrification determined using SOUR and RNA-based gene-specific assays

    Science.gov (United States)

    The effect of CN- (CN-) on nitrification was examined with samples from nitrifying wastewater enrichments using two different approaches: by measuring substrate (ammonia) specific oxygen uptake rates (SOUR), and by using RT-qPCR to quantify the transcripts of functional genes inv...

  17. Effect of heavy metals on nitrification activity as measured by RNA- and DNA-based function-specific assays

    Science.gov (United States)

    Heavy metals can inhibit nitrification, a key process for nitrogen removal in wastewater treatment. The transcriptional responses of functional genes (amoA, hao, nirK and norB) were measured in conjunction with specific oxygen uptake rate (sOUR) for nitrifying enrichment cultures...

  18. EFFECTS OF NITRIFICATION INHIBITORS ON MINERAL NITROGEN DYNAMICS IN AGRICULTURE SOILS

    Directory of Open Access Journals (Sweden)

    Ferisman Tindaon

    2011-10-01

    Full Text Available Experiments were conducted under laboratory conditions to elucidate the effect of three nitrification inhibitors viz, 3.4dimethylpyrazo-lephosphate (DMPP, 4-Chlormethylpyrazole (ClMP and dicyandiamide (DCD on mineral nitrogen dynamics of (NH42SO4 in soil incubated at 25oC in soils. The quantitative determination of ammonium, nitrite and nitrate were carried out spectrophotometrically, while potential denitrify-cation capacity (PDC was measured gas chromatographically. DMPP, ClMP and DCD were used on recommended rates of 90kg N ha-1 corresponding to 0.36µg DMPP; 0.25µg ClMP and 10µg DCD g-1 dry soil. In all treatments, the influence of 1, 10, 50, 100, 250 and 500 times of the recommended-concentrations were examined. Results suggested that DMPP, ClMP and DCD applied at rates generally recommended for agricultural use may not be effective to inhibit nitrification. Thus even at the highest tested NIs-concentrations, nitrate and nitrite formation still occurred. Application of high concentrations of these chemicals up to 180µg DMPP, 125µg ClMP and 2500µg DCD were needed for inhibiting nitrification completely. The three NIs began to inhibit PDC at 10 to 50 times recommended concentration and were more effective in sandy than in loamy or clay soils. ClMP influenced PDC at much lower concentration as DMPP or DCD.

  19. How partial nitrification could improve reclaimed wastewater transport in long pipes.

    Science.gov (United States)

    Delgado, S; Alvarez, M; Rodríguez-Gómez, L E; Elmaleh, S; Aguiar, E

    2001-01-01

    Reclaimed wastewater transport is studied in a concrete-lined cast iron pipe, where a nitrification-denitrification process occurs. The pipe is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain), 0.6 m in diameter and 61 km long. In order to improve wastewater quality, at 10 km from the inlet there is injection of fresh water saturated in dissolved oxygen (DO), after which a fast nitrification process usually appears (less than two hours of space time). The amount of oxidized nitrogen compounds produced varies between 0.8 and 4.4 mg/l NOx(-)-N. When DO has disappeared, a denitrification process begins. The removal of nitrite is complete at the end of the pipe, whereas the nitrate does not disappear completely, leaving a concentration of about 0.4-0.5 mg/l. For a COD/NOx(-)-N ratio higher than 5, a first order nitrification rate in NOx(-)-N has resulted, with the constant k20 = 0.079 h-1, for a NOx(-)-N concentration range of 0.8-4.4 mg/l. Finally the following temperature dependency for the first order denitrification rate constant has been found: k = k20 x 1 x 15T-20. Although nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for reclaimed wastewater disinfection.

  20. Simultaneous heterotrophic nitrification and aerobic denitrification by the marine origin bacterium Pseudomonas sp. ADN-42.

    Science.gov (United States)

    Jin, Ruofei; Liu, Tianqi; Liu, Guangfei; Zhou, Jiti; Huang, Jianyu; Wang, Aijie

    2015-02-01

    Recent research has highlighted the existence of some bacteria that are capable of performing heterotrophic nitrification and have a phenomenal ability to denitrify their nitrification products under aerobic conditions. A high-salinity-tolerant strain ADN-42 was isolated from Hymeniacidon perleve and found to display high heterotrophic ammonium removal capability. This strain was identified as Pseudomonas sp. via 16S rRNA gene sequence analysis. Gene cloning and sequencing analysis indicated that the bacterial genome contains N2O reductase function (nosZ) gene. NH3-N removal rate of ADN-42 was very high. And the highest removal rate was 6.52 mg/L · h in the presence of 40 g/L NaCl. Under the condition of pure oxygen (DO >8 mg/L), NH3-N removal efficiency was 56.9 %. Moreover, 38.4 % of oxygen remained in the upper gas space during 72 h without greenhouse gas N2O production. Keeping continuous and low level of dissolved oxygen (DO <3 mg/L) was helpful for better denitrification performance. All these results indicated that the strain has heterotrophic nitrification and aerobic denitrification abilities, which guarantee future application in wastewater treatment.

  1. Biotransformation of pharmaceuticals under nitrification, nitratation and heterotrophic conditions

    International Nuclear Information System (INIS)

    Fernandez-Fontaina, E.; Gomes, I.B.; Aga, D.S.; Omil, F.; Lema, J.M.; Carballa, M.

    2016-01-01

    The effect of nitrification, nitratation and heterotrophic conditions on the biotransformation of several pharmaceuticals in a highly enriched nitrifying activated sludge was evaluated in this study by selective activation of ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and heterotrophic bacteria. Nitrifiers displayed a noticeable capacity to process ibuprofen due to hydroxylation by ammonia monooxygenase (AMO) to produce 2-hydroxy-ibuprofen. Naproxen was also biotransformed under nitrifying conditions. On the other hand, heterotrophic bacteria present in the nitrifying activated sludge (NAS) biotransformed sulfamethoxazole. In contrast, both nitrifying and heterotrophic activities were ineffective against diclofenac, diazepam, carbamazepine and trimethoprim. Similar biotransformation rates of erythromycin, roxithromycin and fluoxetine were observed under all conditions tested. Overall, results from this study give more evidence on the role of the different microbial communities present in activated sludge reactors on the biological removal of pharmaceuticals. - Highlights: • The removal of pharmaceuticals in nitrifying activated sludge (NAS) was studied. • Nitrifying activity increases biotransformation rate of ibuprofen and naproxen. • Hydroxylation of ibuprofen by ammonia monooxygenase of ammonia oxidizing bacteria • Heterotrophic activity enhances biotransformation of sulfamethoxazole in NAS. • Recalcitrance of trimethoprim, diclofenac, carbamazepine and diazepam in NAS

  2. Biotransformation of pharmaceuticals under nitrification, nitratation and heterotrophic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Fontaina, E., E-mail: eduardo.fernandez.fontaina@usc.es [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Gomes, I.B. [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Aga, D.S. [Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260 (United States); Omil, F.; Lema, J.M.; Carballa, M. [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2016-01-15

    The effect of nitrification, nitratation and heterotrophic conditions on the biotransformation of several pharmaceuticals in a highly enriched nitrifying activated sludge was evaluated in this study by selective activation of ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB) and heterotrophic bacteria. Nitrifiers displayed a noticeable capacity to process ibuprofen due to hydroxylation by ammonia monooxygenase (AMO) to produce 2-hydroxy-ibuprofen. Naproxen was also biotransformed under nitrifying conditions. On the other hand, heterotrophic bacteria present in the nitrifying activated sludge (NAS) biotransformed sulfamethoxazole. In contrast, both nitrifying and heterotrophic activities were ineffective against diclofenac, diazepam, carbamazepine and trimethoprim. Similar biotransformation rates of erythromycin, roxithromycin and fluoxetine were observed under all conditions tested. Overall, results from this study give more evidence on the role of the different microbial communities present in activated sludge reactors on the biological removal of pharmaceuticals. - Highlights: • The removal of pharmaceuticals in nitrifying activated sludge (NAS) was studied. • Nitrifying activity increases biotransformation rate of ibuprofen and naproxen. • Hydroxylation of ibuprofen by ammonia monooxygenase of ammonia oxidizing bacteria • Heterotrophic activity enhances biotransformation of sulfamethoxazole in NAS. • Recalcitrance of trimethoprim, diclofenac, carbamazepine and diazepam in NAS.

  3. Influence of rice straw amendment on mercury methylation and nitrification in paddy soils

    International Nuclear Information System (INIS)

    Liu, Yu-Rong; Dong, Ji-Xin; Han, Li-Li; Zheng, Yuan-Ming; He, Ji-Zheng

    2016-01-01

    Currently, rice straw return in place of burning is becoming more intensive in China than observed previously. However, little is known on the effect of returned rice straw on mercury (Hg) methylation and microbial activity in contaminated paddy fields. Here, we conduct a microcosm experiment to evaluate the effect of rice straw amendment on the Hg methylation and potential nitrification in two paddy soils with distinct Hg levels. Our results show that amended rice straw enhanced Hg methylation for relatively high Hg content soil, but not for low Hg soil, spiking the same additional fresh Hg. methylmercury (MeHg) concentration was significantly correlated to the dissolved organic carbon (DOC) content and relative abundance of dominant microbes associated with Hg methylation. Similarly, amended rice straw was found to only enhance the potential nitrification rate in soil with relatively high Hg content. These findings provide evidence that amended rice straw differentially modulates Hg methylation and nitrification in Hg contaminated soils possibly resulting from different characteristics in the soil microbial community. This highlights that caution should be taken when returning rice straw to contaminated paddy fields, as this practice may increase the risk of more MeHg production. Main finding: Rice straw amendment enhanced both Hg methylation and nitrification potential in the relatively high, but not low, Hg soil. - Highlights: • Rice straw enhanced Hg methylation in relatively high Hg content paddy soils. • Microbial community directly correlated to the Hg methylation. • Mercury methylation in soils depend on Hg bioavailability and microbial activities. • Hg input affects microbial community associated with decomposition of rice straw.

  4. Impact of temperature on nitrification in biological activated carbon (BAC) filters used for drinking water treatment.

    Science.gov (United States)

    Andersson, A; Laurent, P; Kihn, A; Prévost, M; Servais, P

    2001-08-01

    The impact of temperature on nitrification in biological granular activated carbon (GAC) filters was evaluated in order to improve the understanding of the nitrification process in drinking water treatment. The study was conducted in a northern climate where very cold water temperatures (below 2 degrees C) prevail for extended periods and rapid shifts of temperature are frequent in the spring and fall. Ammonia removals were monitored and the fixed nitrifying biomass was measured using a method of potential nitrifying activity. The impact of temperature was evaluated on two different filter media: an opened superstructure wood-based activated carbon and a closed superstructure activated carbon-based on bituminous coal. The study was conducted at two levels: pilot scale (first-stage filters) and full-scale (second-stage filters) and the results indicate a strong temperature impact on nitrification activity. Ammonia removal capacities ranged from 40 to 90% in pilot filters, at temperatures above 10 degrees C, while more than 90% ammonia was removed in the full-scale filters for the same temperature range. At moderate temperatures (4-10 degrees C), the first stage pilot filters removed 10-40% of incoming ammonia for both media (opened and closed superstructure). In the full-scale filters, a difference between the two media in nitrification performances was observed at moderate temperatures: the ammonia removal rate in the opened superstructure support (more than 90%) was higher than in the closed superstructure support (45%). At low temperatures (below 4 degrees C) both media performed poorly. Ammonia removal capacities were below 30% in both pilot- and full-scale filters.

  5. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  6. Dependence of wheat and rice respiration on tissue nitrogen and the corresponding net carbon fixation efficiency under different rates of nitrogen application

    Science.gov (United States)

    Sun, Wenjuan; Huang, Yao; Chen, Shutao; Zou, Jianwen; Zheng, Xunhua

    2007-02-01

    To quantitatively address the role of tissue N in crop respiration under various agricultural practices, and to consequently evaluate the impact of synthetic fertilizer N application on biomass production and respiration, and hence net carbon fixation efficiency ( E ncf), pot and field experiments were carried out for an annual rotation of a rice-wheat cropping system from 2001 to 2003. The treatments of the pot experiments included fertilizer N application, sowing date and planting density. Different rates of N application were tested in the field experiments. Static opaque chambers were used for sampling the gas. The respiration as CO2 emission was detected by a gas chromatograph. A successive biomass clipping method was employed to determine the crop autotrophic respiration coefficient ( R a). Results from the pot experiments revealed a linear relationship between R a and tissue N content as R a = 4.74N-1.45 ( R 2 = 0.85, P < 0.001). Measurements and calculations from the field experiments indicated that fertilizer N application promoted not only biomass production but also increased the respiration of crops. A further investigation showed that the increase of carbon loss in terms of respiration owing to fertilizer N application exceeded that of net carbon gain in terms of aboveground biomass when fertilizer N was applied over a certain rate. Consequently, the E ncf declined as the N application rate increased.

  7. Sediment nitrogen cycling rates and microbial abundance along a submerged vegetation gradient in a eutrophic lake.

    Science.gov (United States)

    Yao, Lu; Chen, Chengrong; Liu, Guihua; Liu, Wenzhi

    2018-03-01

    Decline of submerged vegetation is one of the most serious ecological problems in eutrophic lakes worldwide. Although restoration of submerged vegetation is widely assumed to enhance ecological functions (e.g., nitrogen removal) and aquatic biodiversity, the evidence for this assumption is very limited. Here, we investigated the spatio-temporal patterns of sediment potential nitrification, unamended denitrification and N 2 O production rates along a vegetation gradient in the Lake Honghu, where submerged vegetation was largely restored by prohibiting net-pen aquaculture. We also used five functional genes as markers to quantify the abundance of sediment nitrifying and denitrifying microorganisms. Results showed that unvegetated sediments supported greater nitrification rates than rhizosphere sediments of perennial or seasonal vegetation. However, the absence of submerged vegetation had no significant effect on denitrification and N 2 O production rates. Additionally, the abundance of functional microorganisms in sediments was not significantly different among vegetation types. Season had a strong effect on both nitrogen cycling processes and microbial abundances. The highest nitrification rates were observed in September, while the highest denitrification rates occurred in December. The temporal variation of sediment nitrification, denitrification and N 2 O production rates could be due to changes in water quality and sediment properties rather than submerged vegetation and microbial abundances. Our findings highlight that vegetation restoration in eutrophic lakes improves water quality but does not enhance sediment nitrogen removal rates and microbial abundances. Therefore, for reducing the N level in eutrophic lakes, major efforts should be made to control nutrients export from terrestrial ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Nitrification in agricultural soils: impact, actors and mitigation.

    Science.gov (United States)

    Beeckman, Fabian; Motte, Hans; Beeckman, Tom

    2018-04-01

    Nitrogen is one of the most important nutrients for plant growth and hence heavily applied in agricultural systems via fertilization. Nitrification, that is, the conversion of ammonium via nitrite to nitrate by soil microorganisms, however, leads to nitrate leaching and gaseous nitrous oxide production and as such to an up to 50% loss of nitrogen availability for the plant. Nitrate leaching also results in eutrophication of groundwater, drinking water and recreational waters, toxic algal blooms and biodiversity loss, while nitrous oxide is a greenhouse gas with a global warming potential 300× greater than carbon dioxide. Logically, inhibition of nitrification is an important strategy used in agriculture to reduce nitrogen losses, and contributes to a more environmental-friendly practice. However, recently identified and crucial players in nitrification, that is, ammonia-oxidizing archaea and comammox bacteria, seem to be under-investigated in this respect. In this review, we give an update on the different pathways in ammonia oxidation, the relevance for agriculture and the interaction with nitrification inhibitors. As such, we hope to pinpoint possible strategies to optimize the efficiency of nitrification inhibition. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Effect of pesticides on nitrification in aquatic sediment

    Directory of Open Access Journals (Sweden)

    A. Enrich-Prast

    Full Text Available The aim of this work was to study the effect of the herbicides glyphosate, nonanoic acid, and dichlorprop-P and the insecticides potassium oil, malation and Pyretrin and their combinations on nitrification. Nitrification was measured in slurries from the eutrophic and shallow Brabrand Lake (Aarhus, Denmark, by inhibiting oxidation of nitrite to nitrate with chloride. All herbicides and insecticides influenced nitrification. The No Observed Effect Concentration (NOEC was assessed to be 30 µg.L-1 for glyphosate and nonanoic acid and 1 µg.L-1 for dichlorprop-P. The NOEC for malation and Pyretrin on nitrification was assessed to be 3 µg.L-1. No accumulation effect on nitrification of the insecticides malation and Pyretrin, or of the studied herbicides, was observed, indicating that their environmental impact is low at reduced concentrations, even in combination. The procedure used in this study can provide a useful tool for obtaining concentration limits for pesticides or other chemicals in a short period of time.

  10. Heterogeneous Nitrification in a Full Scale Rapid Sand Filter Treating Groundwater

    DEFF Research Database (Denmark)

    Lopato, Laure; Röttgers, Nina; Binning, Philip John

    2013-01-01

    Experiments were conducted to determine ammonium removal kinetics in an operating biologically active sand filter at a waterworks treating anaerobic groundwater. The ammonium load varied between 0.7 and 3 g N/h/m2 (concentration ranged from 0.23 to 0.78 mg N/l) and the inlet water flux varied...... nitrification rate constant was closely related to the water pore velocity which implies that the rate is strongly determined by the resistance to mass transport in the diffusion boundary layer around the sand grains. Read More: http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EE.1943-7870.0000653...

  11. Characterization of novel Bacillus strain N31 from mariculture water capable of halophilic heterotrophic nitrification-aerobic denitrification.

    Science.gov (United States)

    Huang, Fei; Pan, Luqing; Lv, Na; Tang, Xianming

    2017-11-01

    The development of an intensive aquaculture industry has been accompanied by increasing environmental impacts, especially nitrogen pollution. In this study, a novel halophilic bacterium capable of heterotrophic nitrification and aerobic denitrification was isolated from mariculture water and identified as Bacillus litoralis N31. The efficiency of ammonium, nitrite and nitrate removal by N31 were 86.3%, 89.3% and 89.4%, respectively, after a 48-h cultivation in sole N-source medium with initial nitrogen approximately 20 mg/L. However, ammonium was removed preferentially, and no obvious nitrite accumulated during the simultaneous nitrification and denitrification process in mixed N-source media. The existence of hao, napA and nirS genes further proved the heterotrophic nitrification-aerobic denitrification capability of N31. The optimal conditions for ammonium removal were 30°C, initial pH 7.5-8.5, C/N ratio 5-20 and salinity 30-40‰, and the nitrification rate of N31 increased with increasing initial [Formula: see text] from 10 to 250 mg/L. Biosecurity assessment with shrimp indicated that strain N31 could be applied in the marine aquaculture industry safely for culture water remediation and effluent treatment. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  12. Inhibitory effect of cyanide on nitrification process and its eliminating method in a suspended activated sludge process.

    Science.gov (United States)

    Han, Yuanyuan; Jin, Xibiao; Wang, Yuan; Liu, Yongdi; Chen, Xiurong

    2014-02-01

    Inhibition of nitrification by four typical pollutants (acrylonitrile, acrylic acid, acetonitrile and cyanide) in acrylonitrile wastewater was investigated. The inhibitory effect of cyanide on nitrification was strongest, with a 50% inhibitory concentration of 0.218 mg·gVSS-1 being observed in a municipal activated sludge system. However, the performance of nitrification was recovered when cyanide was completely degraded. The nitrification, which had been inhibited by 4.17 mg·gVSS-1 of free cyanide for 24 h, was recovered to greater than 95% of that without cyanide after 10 days of recovery. To overcome cyanide inhibition, cyanide-degrading bacteria were cultivated in a batch reactor by increasing the influent cyanide concentration in a stepwise manner, which resulted in an increase in the average cyanide degradation rate from 0.14 to 1.01 mg CN-·gVSS-1·h-1 over 20 days. The cultured cyanide-degrading bacteria were shaped like short rods, and the dominant cyanide-degrading bacteria strain was identified as Pseudomonas fluorescens NCIMB by PCR.

  13. The HLA-net GENE[RATE] pipeline for effective HLA data analysis and its application to 145 population samples from Europe and neighbouring areas.

    Science.gov (United States)

    Nunes, J M; Buhler, S; Roessli, D; Sanchez-Mazas, A

    2014-05-01

    In this review, we present for the first time an integrated version of the Gene[rate] computer tools which have been developed during the last 5 years to analyse human leukocyte antigen (HLA) data in human populations, as well as the results of their application to a large dataset of 145 HLA-typed population samples from Europe and its two neighbouring areas, North Africa and West Asia, now forming part of the Gene[va] database. All these computer tools and genetic data are, from now, publicly available through a newly designed bioinformatics platform, HLA-net, here presented as a main achievement of the HLA-NET scientific programme. The Gene[rate] pipeline offers user-friendly computer tools to estimate allele and haplotype frequencies, to test Hardy-Weinberg equilibrium (HWE), selective neutrality and linkage disequilibrium, to recode HLA data, to convert file formats, to display population frequencies of chosen alleles and haplotypes in selected geographic regions, and to perform genetic comparisons among chosen sets of population samples, including new data provided by the user. Both numerical and graphical outputs are generated, the latter being highly explicit and of publication quality. All these analyses can be performed on the pipeline after scrupulous validation of the population sample's characterisation and HLA typing reporting according to HLA-NET recommendations. The Gene[va] database offers direct access to the HLA-A, -B, -C, -DQA1, -DQB1, -DRB1 and -DPB1 frequencies and summary statistics of 145 population samples having successfully passed these HLA-NET 'filters', and representing three European subregions (South-East, North-East and Central-West Europe) and two neighbouring areas (North Africa, as far as Sudan, and West Asia, as far as South India). The analysis of these data, summarized in this review, shows a substantial genetic variation at the regional level in this continental area. These results have main implications for population genetics

  14. Petri Nets

    Indian Academy of Sciences (India)

    GENERAL I ARTICLE ... In Part 1 of this two-part article, we have seen im- ..... mable logic controller and VLSI arrays, office automation systems, workflow management systems, ... complex discrete event and real-time systems; and Petri nets.

  15. Assessing nitrification and denitrification in a paddy soil with different water dynamics and applied liquid cattle waste using the {sup 15}N isotopic technique

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Sheng, E-mail: jszs@cc.tuat.ac.jp [Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Eco-environmental Protection Institute, Shanghai Academy of Agricultural Sciences, 1000 Jinqi Road, Shanghai 201403 (China); Sakiyama, Yukina; Riya, Shohei [Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Song, Xiangfu [Eco-environmental Protection Institute, Shanghai Academy of Agricultural Sciences, 1000 Jinqi Road, Shanghai 201403 (China); Terada, Akihiko; Hosomi, Masaaki [Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2012-07-15

    Using livestock wastewater for rice production in paddy fields can remove nitrogen and supplement the use of chemical fertilizers. However, paddy fields have complicated water dynamics owing to varying characteristics and would influence nitrogen removal through nitrification followed by denitrification. Quantification of nitrification and denitrification is of great importance in assessing the influence of water dynamics on nitrogen removal in paddy fields. In this study, nitrification and nitrate reduction rates with different water dynamics after liquid cattle waste application were evaluated, and the in situ denitrification rate was determined directly using the {sup 15}N isotopic technique in a laboratory experiment. A significant linear regression correlation between nitrification and the nitrate reduction rate was observed and showed different regression coefficients under different water dynamics. The regression coefficient in the continuously flooded paddy soil was higher than in the drained-reflooded paddy soil, suggesting that nitrate would be consumed faster in the flooded paddy soil. However, nitrification was limited and the maximum rate was only 13.3 {mu}g N g{sup -1} day{sup -1} in the flooded paddy soil with rice plants, which limited the supply of nitrate. In contrast, the drained-reflooded paddy soil had an enhanced nitrification rate up to 56.8 {mu}g N g{sup -1} day{sup -1}, which was four times higher than the flooded paddy soil and further stimulated nitrate reduction rates. Correspondingly, the in situ denitrification rates determined directly in the drained-reflooded paddy soil ranged from 5 to 1035 mg N m{sup -2} day{sup -1}, which was higher than the continuously flooded paddy soil (from 5 to 318 mg N m{sup -2} day{sup -1}) during the vegetation period. The nitrogen removal through denitrification accounted for 38.9% and 9.9% of applied nitrogen in the drained-reflooded paddy soil and continuously flooded paddy soil, respectively

  16. Applying Molecular Tools for Monitoring Inhibition of Nitrification by Heavy Metals

    Science.gov (United States)

    The biological removal of ammonia in conventional wastewater treatment plants (WWTPs) is performed by promoting nitrification and denitrification as sequential steps. The first step in nitrification, the oxidation of ammonia to nitrite by ammonia oxidizing bacteria (AOB), is sens...

  17. Developing Fluorescence Sensor Systems for Early Detection of Nitrification Events in Chloraminated Drinking Water Distribution Systems

    Science.gov (United States)

    Detection of nitrification events in chloraminated drinking water distribution systems remains an ongoing challenge for many drinking water utilities, including Dallas Water Utilities (DWU) and the City of Houston (CoH). Each year, these utilities experience nitrification events ...

  18. Fluorescence Sensors for Early Detection of Nitrification in Drinking Water Distribution Systems – Interference Corrections (Poster)

    Science.gov (United States)

    Nitrification event detection in chloraminated drinking water distribution systems (DWDSs) remains an ongoing challenge for many drinking water utilities, including Dallas Water Utilities (DWU) and the City of Houston (CoH). Each year, these utilities experience nitrification eve...

  19. Fluorescence Sensors for Early Detection of Nitrification in Drinking Water Distribution Systems – Interference Corrections (Abstract)

    Science.gov (United States)

    Nitrification event detection in chloraminated drinking water distribution systems (DWDSs) remains an ongoing challenge for many drinking water utilities, including Dallas Water Utilities (DWU) and the City of Houston (CoH). Each year, these utilities experience nitrification eve...

  20. Overview of Causes and Control of Nitrification in Chloraminated Drinking Water Distribution Systems

    Science.gov (United States)

    This chapter provides an integrated overview of nitrification causes and control in chloraminated drinking water distribution systems, leading to an in-depth discussion of nitrification microbiology, monitoring, prevention, response, and engineering improvements in subsequent man...

  1. Effects of Nitrification Inhibitors and Sulphur Coated Urea(SCU on Different Nitrogen Sources and Wheat Yield

    Directory of Open Access Journals (Sweden)

    LI Yong-qiang

    2016-05-01

    (CK, only urea, SCU and the combination use of DCD, TFR, THU three concentration gradients(0.5%, 1%, 2% of urea dosage with urea respectively. The results showed:the inhibition of nitrification was gradually enhanced with the increase of its concentration, high dose nitrification inhibitor decreased the content of soil NO3--N significantly, the soil NO3--N concentration with DCD, THU, TFR at the 2% dosage were lower than that with only urea by 29%, 22% and 14% respectively, and the inhibition effect of soil apparent nitrification rate was also 2%DCD> 2%THU> 2%TFR. The SCU treatment effect was close to the 2% DCD function strength, and it reflected the inhibition effect in the early stage of application, the soil apparent nitrification rate in the seventy-fourth days after fertilization was significantly lower than that of using the nitrification inhibition(P<0.05. Both of nitrification inhibitor and SCU could make the soil NH4+-N concentration at a higher level, and the more inhibitor dosage, the higher the content of NH4+-N in soil. Compared with the single application of urea, urea + DCD model could all increase wheat yield at 0.5%, 1%, 2% concentration and reached a significant level(P<0.05. When THU was added at 1% and 2% coucentration, wheat yield was significantly higher than that of the single application of urea, but the increase yield effect was lower than that of DCD treatment. On the whole, the effect of SCU on the control and release nitrogen was more lasting than that of nitrification inhibitor, among three nitrification inhibitors, TFR and DCD were better than THU in controlling soil ammonia nitrogen transformation, soil nitrification inhibition and urease inhibition. The study can provide scientific basis for the screening of nitrification inhibitors and coated fertilizers, but the long-term use of exogenous additives may cause potential harm to soil environment, so it need to be further studied about the morphological transformation and long-term role of

  2. Quantitative estimation of net rates of production of bacterial and protozoal nitrogen and their interconversion in the rumen

    International Nuclear Information System (INIS)

    El-Fouly, H.A.

    1983-01-01

    A technique is described using 35 S-labelled bacteria or protozoa by which the rates of production of microbial and protozoal protein N may be calculated. The results indicate an average microbial protein yield of about 13.7gN.d -1 in sheep maintained on a diet consisting largely of cottonseed cake and wheat and rice bran. Evidence is presented that protozoa made little contribution to the microbial protein-N leaving the rumen. Also, the average rate of N flow from the protozoal to the bacterial pool was about 3.5g.d -1 , whereas about 1.4g.d -1 of bacterial N was consumed by protozoa. (author)

  3. Integrating livestock manure with a corn-soybean bioenergy cropping system improves short-term carbon sequestration rates and net global warming potential

    Energy Technology Data Exchange (ETDEWEB)

    Thelen, K.D.; Fronning, B.E.; Kravchenko, A.; Min, D.H.; Robertson, G.P. [Michigan State University, East Lansing, MI 48824 (United States)

    2010-07-15

    Carbon cycling and the global warming potential (GWP) of bioenergy cropping systems with complete biomass removal are of agronomic and environmental concern. Corn growers who plan to remove corn stover as a feedstock for the emerging cellulosic ethanol industry will benefit from carbon amendments such as manure and compost, to replace carbon removed with the corn stover. The objective of this research was to determine the effect of beef cattle feedlot manure and composted dairy manure on short-term carbon sequestration rates and net global warming potential (GWP) in a corn-soybean rotation with complete corn-stover removal. Field experiments consisting of a corn-soybean rotation with whole-plant corn harvest, were conducted near East Lansing, MI over a three-year period beginning in 2002. Compost and manure amendments raised soil carbon (C) at a level sufficient to overcome the C debt associated with manure production, manure collection and storage, land application, and post-application field emissions. The net GWP in carbon dioxide equivalents for the manure and compost amended cropping systems was -934 and -784 g m{sup -2} y{sup -1}, respectively, compared to 52 g m{sup -2} y{sup -1} for the non-manure amended synthetic fertilizer check. This work further substantiates the environmental benefits associated with renewable fuels and demonstrates that with proper management, the integration of livestock manures in biofuel cropping systems can enhance greenhouse gas (GHG) remediation. (author)

  4. Integrating livestock manure with a corn-soybean bioenergy cropping system improves short-term carbon sequestration rates and net global warming potential

    International Nuclear Information System (INIS)

    Thelen, K.D.; Fronning, B.E.; Kravchenko, A.; Min, D.H.; Robertson, G.P.

    2010-01-01

    Carbon cycling and the global warming potential (GWP) of bioenergy cropping systems with complete biomass removal are of agronomic and environmental concern. Corn growers who plan to remove corn stover as a feedstock for the emerging cellulosic ethanol industry will benefit from carbon amendments such as manure and compost, to replace carbon removed with the corn stover. The objective of this research was to determine the effect of beef cattle feedlot manure and composted dairy manure on short-term carbon sequestration rates and net global warming potential (GWP) in a corn-soybean rotation with complete corn-stover removal. Field experiments consisting of a corn-soybean rotation with whole-plant corn harvest, were conducted near East Lansing, MI over a three-year period beginning in 2002. Compost and manure amendments raised soil carbon (C) at a level sufficient to overcome the C debt associated with manure production, manure collection and storage, land application, and post-application field emissions. The net GWP in carbon dioxide equivalents for the manure and compost amended cropping systems was -934 and -784 g m -2 y -1 , respectively, compared to 52 g m -2 y -1 for the non-manure amended synthetic fertilizer check. This work further substantiates the environmental benefits associated with renewable fuels and demonstrates that with proper management, the integration of livestock manures in biofuel cropping systems can enhance greenhouse gas (GHG) remediation.

  5. Aeration to degas CO{sub 2}, increase pH, and increase iron oxidation rates for efficient treatment of net alkaline mine drainage

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, C.S.; Dennis, A.; Kahler, A. [Bucknell University, Lewisburg, PA (United States). Dept. of Geology

    2009-07-15

    Passive treatment systems for mine drainage use no energy other than gravity, but they require greater area than active treatment systems. Researchers are considering 'hybrid' systems that have passive and active components for increased efficiency, especially where space limitations render passive-only technology ineffective. Flow-through reactor field experiments were conducted at two large net-alkaline anthracite mine discharges in central Pennsylvania. Assuming an Fe removal rate of 20 g m{sup -2} day{sup -1} and Fe loading from field data, 3.6 x 10{sup 3} and 3.0 x 10{sup 4} m{sup 2} oxidation ponds would be required for the passive treatment of Site 21 and Packer 5 discharges, respectively. However, only a small area is available at each site. This paper demonstrates aeration to drive off CO{sub 2}, increase pH, and increase Fe(II) oxidation rates, enabling treatment within a small area compared to passive treatment methods, and introduces a geochemical model to accurately predict these rates as well as semi-passive treatment system sizing parameters. Iron(II) oxidation modeling of actively aerated systems predicted that a 1-m deep pond with 10 times less area than estimated for passive treatment would lower Fe(II) concentrations to less than 1 mg L-1 at summer and winter temperatures for both sites. The use of active aeration for treatment Of CO{sub 2}-rich, net-alkaline discharges (including partially treated effluent from anoxic limestone drains) can result in considerably reduced treatment area for oxidation and may lower treatment costs, but settling of Fe hydroxides was not considered in this study. The reduced capital cost for earthmoving will need to be compared to energy and maintenance costs for aeration.

  6. Enhancing nitrification at low temperature with zeolite in a mining operations retention pond

    Directory of Open Access Journals (Sweden)

    Misha eMiazga-Rodriguez

    2012-07-01

    Full Text Available Ammonium nitrate explosives are used in mining operations at Diavik Diamond Mines Inc. in the Northwest Territories, Canada. Residual nitrogen is washed into the mine pit and piped to a nearby retention pond where its removal is accomplished by microbial activity prior to a final water treatment step and release into the sub-Arctic lake, Lac de Gras. Microbial removal of ammonium in the retention pond is rapid during the brief ice-free summer, but often slows under ice cover that persists up to nine months of the year. The aluminosilicate mineral zeolite was tested as an additive to retention pond water to increase rates of ammonium removal at 4 °C. Water samples were collected across the length of the retention pond monthly over a year. The structure of the microbial community (bacteria, archaea, and eukarya, as determined by denaturing gradient gel electrophoresis of PCR-amplified small subunit ribosomal RNA genes, was more stable during cold months than during July-September, when there was a marked phytoplankton bloom. Of the ammonia-oxidizing community, only bacterial amoA genes were consistently detected. Zeolite (10 g was added to retention pond water (100 mL amended with 5 mM ammonium and incubated at 12 °C to encourage development of a nitrifying biofilm. The biofilm community was composed of different amoA phylotypes from those identified in gene clone libraries of native water samples. Zeolite biofilm was added to fresh water samples collected at different times of the year, resulting in a significant increase in laboratory measurements of potential nitrification activity at 4 °C. A significant positive correlation between the amount of zeolite biofilm and potential nitrification activity was observed; rates were unaffected in incubations containing 1-20 mM ammonium. Addition of zeolite to retention ponds in cold environments could effectively increase nitrification rates year round by concentrating active nitrifying biomass.

  7. Contributions of ammonia-oxidizing archaea and bacteria to nitrification in Oregon forest soils

    Science.gov (United States)

    Xinda Lu; Peter J. Bottomley; David D. Myrold

    2015-01-01

    Ammonia oxidation, the first step of nitrification, is mediated by both ammonia-oxidizing archaea (AOA) and bacteria (AOB); however, the relative contributions of AOA and AOB to soil nitrification are not well understood. In this study we used 1-octyne to discriminate between AOA-and AOB-supported nitrifi-cation determined both in soil-water slurries and in unsaturated...

  8. Direct contribution of clams (Ruditapes philippinarum) to benthic fluxes, nitrification, denitrification and nitrous oxide emission in a farmed sediment

    Science.gov (United States)

    Welsh, David T.; Nizzoli, Daniele; Fano, Elisa A.; Viaroli, Pierluigi

    2015-03-01

    The influence of the manila clam (Ruditapes philippinarum) on N-cycle processes, and oxygen and nutrient fluxes in a farmed sediment was investigated using a multiple core incubation approach and parallel incubations of individual clams. Clam population/biomass density varied ∼8-fold between cores and all sediment-water column solute (O2. N2, N2O, NH4+, NOX and DIN) fluxes and benthic process (N-regeneration, nitrification and denitrification) rates were strongly and significantly correlated with clam density/biomass. Isolated clams exhibited high rates of respiration, N-excretion, nitrification and denitrification of 2050 ± 70, 395 ± 49, 201 ± 42 and 235 ± 40 nmol individual-1 h-1, respectively. The direct contribution of the clams and their associated microbiota to benthic processes was estimated by multiplying the per individual rates by the number of clams in each incubated core. The clams on average directly accounted for 64-133% of total rates of sediment oxygen demand, N-regeneration, nitrification and denitrification, indicating that they regulated processes primarily through their own metabolic activity and that of bacteria that colonise them. Clams and the farmed sediments were significant sources of the greenhouse gas N2O, but this was primarily due to their high nitrification and denitrification rates, rather than high specific N2O yields, as N2O emissions represented farmed sediments had a high denitrification efficiency of 67 ± 10%, but this ecosystem service came at the environmental cost of increased N-regeneration and N2O emission rates. The measured N2O emissions indicate that bivalve aquaculture may be a significant source of N2O. It is therefore recommended that N2O emissions should be included in the impact assessments of current and future bivalve-farming projects.

  9. Mosquito abundance, bed net coverage and other factors associated with variations in sporozoite infectivity rates in four villages of rural Tanzania

    DEFF Research Database (Denmark)

    Kweka, Eliningaya J; Nkya, Watoky M M; Mahande, Aneth M

    2008-01-01

    . Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. METHODOLOGY: A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch...... methods. In each village, ten paired houses were selected for mosquitoes sampling. Sampling was done in fortnight case and study was undertaken for six months in both Kilimanjaro (Northern Tanzania) and Dodoma (Central Tanzania) regions. RESULTS: A total of 6,883 mosquitoes were collected including: 5......,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1...

  10. RESTful NET

    CERN Document Server

    Flanders, Jon

    2008-01-01

    RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa

  11. Improved netting

    International Nuclear Information System (INIS)

    Bramley, A.; Clabburn, R.J.T.

    1976-01-01

    A method is described for producing netting composed of longitudinal and transverse threads of irradiation cross linked thermoplastic material, the threads being joined together at their crossings by moulded masses of cross linked thermoplastic material. The thread may be formed of polyethylene filaments, subjected to a radiation dose of 15 to 25 MR. The moulding can be conducted at 245 0 to 260 0 C or higher. The product is claimed to be an improved quality of netting, with bonds of increased strength between crossing threads. (U.K.)

  12. Nitrification at different salinities: Biofilm community composition and physiological plasticity.

    Science.gov (United States)

    Gonzalez-Silva, Blanca M; Jonassen, Kjell Rune; Bakke, Ingrid; Østgaard, Kjetill; Vadstein, Olav

    2016-05-15

    This paper describes an experimental study of microbial communities of three moving bed biofilm reactors (MBBR) inoculated with nitrifying cultures originated from environments with different salinity; freshwater, brackish (20‰) and seawater. All reactors were run until they operated at a conversion efficiency of >96%. The microbial communities were profiled using 454-pyrosequencing of 16S rRNA gene amplicons. Statistical analysis was used to investigate the differences in microbial community structure and distribution of the nitrifying populations with different salinity environments. Nonmetric multidimensional scaling analysis (NMDS) and the PERMANOVA test based on Bray-Curtis similarities revealed significantly different community structure in the three reactors. The brackish reactor showed lower diversity index than fresh and seawater reactors. Venn diagram showed that 60 and 78% of the total operational taxonomic units (OTUs) in the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) guild, respectively, were unique OTUs for a given reactor. Similarity Percentages (SIMPER) analysis showed that two-thirds of the total difference in community structure between the reactors was explained by 10 OTUs, indicating that only a small number of OTUs play a numerically dominant role in the nitrification process. Acute toxicity of salt stress on ammonium and nitrite oxidizing activities showed distinctly different patterns, reaching 97% inhibition of the freshwater reactor for ammonium oxidation rate. In the brackish culture, inhibition was only observed at maximal level of salinity, 32‰. In the fully adapted seawater culture, higher activities were observed at 32‰ than at any of the lower salinities. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Estimation of nitrification capacity of rock media trickling filters in ...

    African Journals Online (AJOL)

    To address this deficiency, a full-scale ENBNRAS prototype was implemented at the Daspoort Wastewater Treatment Works (DWWTW) in Tshwane, South Africa. In this investigation an average apparent nitrification capacity of approximately 1.25 to 1.29 gN per m2 of media surface area per day [gN/(ms2Ed)] ammonia ...

  14. Modelling and simulation of a nitrification biofilter for drinking water ...

    African Journals Online (AJOL)

    For the purification of pure and microbiologically safe drinking water, different treatment steps are necessary. One of those steps is the removal of ammonium, which can, e.g. be accomplished through nitrification in a biofilter. In this study, a model for such a nitrifying biofilter was developed and the model was ...

  15. Aeration to degas CO2, increase pH, and increase iron oxidation rates for efficient treatment of net alkaline mine drainage

    International Nuclear Information System (INIS)

    Kirby, C.S.; Dennis, A.; Kahler, A.

    2009-01-01

    Passive treatment systems for mine drainage use no energy other than gravity, but they require greater area than active treatment systems. Researchers are considering 'hybrid' systems that have passive and active components for increased efficiency, especially where space limitations render passive-only technology ineffective. Flow-through reactor field experiments were conducted at two large net-alkaline anthracite mine discharges in central Pennsylvania. Assuming an Fe removal rate of 20 g m -2 day -1 and Fe loading from field data, 3.6 x 10 3 and 3.0 x 10 4 m 2 oxidation ponds would be required for the passive treatment of Site 21 and Packer 5 discharges, respectively. However, only a small area is available at each site. This paper demonstrates aeration to drive off CO 2 , increase pH, and increase Fe(II) oxidation rates, enabling treatment within a small area compared to passive treatment methods, and introduces a geochemical model to accurately predict these rates as well as semi-passive treatment system sizing parameters. Both net-alkaline discharges were suboxic with a pH of ∼5.7, Fe(II) concentration of ∼16 mg L -1 , and low Mn and Al concentrations. Flow rates were ∼4000 L min -1 at Site 21 and 15,000 L min -1 at Packer 5. Three-h aeration experiments with flow rates scaled to a 14-L reactor resulted in pH increases from 5.7 to greater than 7, temperature increases from 12 to 22 deg. C, dissolved O 2 increases to saturation with respect to the atmosphere, and Fe(II) concentration decreases from 16 to -1 . A 17,000-L pilot-scale reactor at Site 21 produced similar results although aeration was not as complete as in the smaller reactor. Two non-aerated experiments at Site 21 with 13 and 25-h run times resulted in pH changes of ≤0.2 and Fe(II) concentration decreases of less than 3 mg L -1 . An Fe(II) oxidation model written in a differential equation solver matched the field experiments very well using field-measured pH, temperature, dissolved O 2

  16. NetSig

    DEFF Research Database (Denmark)

    Horn, Heiko; Lawrence, Michael S; Chouinard, Candace R

    2018-01-01

    Methods that integrate molecular network information and tumor genome data could complement gene-based statistical tests to identify likely new cancer genes; but such approaches are challenging to validate at scale, and their predictive value remains unclear. We developed a robust statistic (Net......Sig) that integrates protein interaction networks with data from 4,742 tumor exomes. NetSig can accurately classify known driver genes in 60% of tested tumor types and predicts 62 new driver candidates. Using a quantitative experimental framework to determine in vivo tumorigenic potential in mice, we found that Net......Sig candidates induce tumors at rates that are comparable to those of known oncogenes and are ten-fold higher than those of random genes. By reanalyzing nine tumor-inducing NetSig candidates in 242 patients with oncogene-negative lung adenocarcinomas, we find that two (AKT2 and TFDP2) are significantly amplified...

  17. Petri Nets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52 ... Author Affiliations. Y Narahari1. Department of Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.

  18. Net Gain

    International Development Research Centre (IDRC) Digital Library (Canada)

    Describing the effect of tax incentives for import, production, and sale of nets and insecticides; and ..... So far, China is the only country where a system for the routine treatment of ...... 1993), and the trials in Ecuador and Peru (Kroeger et al.

  19. Use of bioreactor landfill for nitrogen removal to enhance methane production through ex situ simultaneous nitrification-denitrification and in situ denitrification.

    Science.gov (United States)

    Sun, Xiaojie; Zhang, Hongxia; Cheng, Zhaowen

    2017-08-01

    High concentrations of nitrate-nitrogen (NO 3 - -N) derived from ex situ nitrification phase can inhibit methane production during ex situ nitrification and in situ denitrification bioreactor landfill. A combined process comprised of ex situ simultaneous nitrification-denitrification (SND) in an aged refuse bioreactor (ARB) and in situ denitrification in a fresh refuse bioreactor (FRB) was conducted to reduce the negative effect of high concentrationsof NO 3 - -N. Ex situ SND can be achieved because NO 3 - -N concentration can be reduced and the removal rate of ammonium-nitrogen (NH 4 + -N) remains largely unchanged when the ventilation rate of ARB-A2 is controlled. The average NO 3 - -N concentrations of effluent were 470mg/L in ex situ nitrification ARB-A1 and 186mg/L in ex situ SND ARB-A2. The average NH 4 + -N removal rates of ARB-A1 and ARB-A2 were 98% and 94%, respectively. Based on the experimental data from week 4 to week 30, it is predicted that NH 4 + -N concentration in FRB-F1 of the ex situ nitrification and in situ denitrification process would reach 25mg/L after 63weeks, and about 40weeks for the FRB-F2 of ex situ SND and in situ denitrification process . Ex situ SND and in situ denitrification process can improve themethane production of FRB-F2. The lag phase time of methane production for the FRB-F2 was 11weeks. This phase was significantly shorter than the 15-week phases of FRB-F1 in ex situ nitrification and in situ denitrification process. A seven-week stabilizationphase was required to increase methane content from 5% to 50% for FRB-F2. Methane content in FRB-F1 did not reach 50% but reached the 45% peak after 20weeks. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Effects of nitrogen application rates on net annual global warming potential and greenhouse gas intensity in double-rice cropping systems of the Southern China.

    Science.gov (United States)

    Chen, Zhongdu; Chen, Fu; Zhang, Hailin; Liu, Shengli

    2016-12-01

    The net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI) of double-rice cropping systems are not well documented. We measured the NGWP and NGHGI including soil organic carbon (SOC) change and indirect emissions (IE) from double-crop rice fields with fertilizing systems in Southern China. These experiments with three different nitrogen (N) application rates since 2012 are as follows: 165 kgN ha -1 for early rice and 225 kgN ha -1 for late rice (N1), which was the local N application rates as the control; 135 kgN ha -1 for early rice and 180 kgN ha -1 for late rice (N2, 20 % reduction); and 105 kgN ha -1 for early rice and 135 kgN ha -1 for late rice (N3, 40 % reduction). Results showed that yields increased with the increase of N application rate, but without significant difference between N1 and N2 plots. Annual SOC sequestration rate under N1 was estimated to be 1.15 MgC ha -1  year -1 , which was higher than those under other fertilizing systems. Higher N application tended to increase CH 4 emissions during the flooded rice season and significantly increased N 2 O emissions from drained soils during the nonrice season, ranking as N1 > N2 > N3 with significant difference (P < 0.05). Two-year average IE has a huge contribution to GHG emissions mainly coming from the higher N inputs in the double-rice cropping system. Reducing N fertilizer usage can effectively decrease the NGWP and NGHGI in the double-rice cropping system, with the lowest NGHGI obtained in the N2 plot (0.99 kg CO 2 -eq kg -1 yield year -1 ). The results suggested that agricultural economic viability and GHG mitigation can be simultaneously achieved by properly reducing N fertilizer application in double-rice cropping systems.

  1. Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    Huiqiang Li; Hongjun Han; Maoan Du; Wei Wang

    2011-01-01

    Moving bed biofilm reactor (MBBR) was used to treat real coal gasification wastewater.Nitrification of the MBBR was inhibited almost completely during start-up period.Sudden increase of influent total NH3 concentration was the main factor inducing nitrification inhibition.Increasing DO concentration in the bulk liquid (from 2 to 3 mg/L) had little effect on nitrification recovery.Nitrification of the MBBR recovered partially by the addition of nitrifying sludge into the reactor and almost ceased within 5 days.Nitrification ratio of the MBBR achieved 65% within 12 days by increasing dilute ratio of the influent wastewater with tap water.The ratio of nitrification decreased to 25% when infiuent COD concentration increased from 650 to 1000 mg/L after nitrification recovery and recovered 70%for another 4 days.

  2. Gross nitrous oxide production drives net nitrous oxide fluxes across a salt marsh landscape.

    Science.gov (United States)

    Yang, Wendy H; Silver, Whendee L

    2016-06-01

    Sea level rise will change inundation regimes in salt marshes, altering redox dynamics that control nitrification - a potential source of the potent greenhouse gas, nitrous oxide (N2 O) - and denitrification, a major nitrogen (N) loss pathway in coastal ecosystems and both a source and sink of N2 O. Measurements of net N2 O fluxes alone yield little insight into the different effects of redox conditions on N2 O production and consumption. We used in situ measurements of gross N2 O fluxes across a salt marsh elevation gradient to determine how soil N2 O emissions in coastal ecosystems may respond to future sea level rise. Soil redox declined as marsh elevation decreased, with lower soil nitrate and higher ferrous iron in the low marsh compared to the mid and high marshes (P production was highest in the low marsh and lowest in the mid-marsh (P = 0.02), whereas gross N2 O consumption did not differ among marsh zones. Thus, variability in gross N2 O production rates drove the differences in net N2 O flux among marsh zones. Our results suggest that future studies should focus on elucidating controls on the processes producing, rather than consuming, N2 O in salt marshes to improve our predictions of changes in net N2 O fluxes caused by future sea level rise. © 2015 John Wiley & Sons Ltd.

  3. Complete nutrient recovery from source-separated urine by nitrification and distillation.

    Science.gov (United States)

    Udert, K M; Wächter, M

    2012-02-01

    In this study we present a method to recover all nutrients from source-separated urine in a dry solid by combining biological nitrification with distillation. In a first process step, a membrane-aerated biofilm reactor was operated stably for more than 12 months, producing a nutrient solution with a pH between 6.2 and 7.0 (depending on the pH set-point), and an ammonium to nitrate ratio between 0.87 and 1.15 gN gN(-1). The maximum nitrification rate was 1.8 ± 0.3 gN m(-2) d(-1). Process stability was achieved by controlling the pH via the influent. In the second process step, real nitrified urine and synthetic solutions were concentrated in lab-scale distillation reactors. All nutrients were recovered in a dry powder except for some ammonia (less than 3% of total nitrogen). We estimate that the primary energy demand for a simple nitrification/distillation process is four to five times higher than removing nitrogen and phosphorus in a conventional wastewater treatment plant and producing the equivalent amount of phosphorus and nitrogen fertilizers. However, the primary energy demand can be reduced to values very close to conventional treatment, if 80% of the water is removed with reverse osmosis and distillation is operated with vapor compression. The ammonium nitrate content of the solid residue is below the limit at which stringent EU safety regulations for fertilizers come into effect; nevertheless, we propose some additional process steps that will increase the thermal stability of the solid product. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Potential for biological nitrification inhibition to reduce nitrification and N2O emissions in pasture crop-livestock systems.

    Science.gov (United States)

    Subbarao, G V; Rao, I M; Nakahara, K; Sahrawat, K L; Ando, Y; Kawashima, T

    2013-06-01

    Agriculture and livestock production systems are two major emitters of greenhouse gases. Methane with a GWP (global warming potential) of 21, and nitrous oxide (N2O) with a GWP of 300, are largely emitted from animal production agriculture, where livestock production is based on pasture and feed grains. The principal biological processes involved in N2O emissions are nitrification and denitrification. Biological nitrification inhibition (BNI) is the natural ability of certain plant species to release nitrification inhibitors from their roots that suppress nitrifier activity, thus reducing soil nitrification and N2O emission. Recent methodological developments (e.g. bioluminescence assay to detect BNIs in plant root systems) have led to significant advances in our ability to quantify and characterize the BNI function. Synthesis and release of BNIs from plants is a highly regulated process triggered by the presence of NH4 + in the rhizosphere, which results in the inhibitor being released precisely where the majority of the soil-nitrifier population resides. Among the tropical pasture grasses, the BNI function is strongest (i.e. BNI capacity) in Brachiaria sp. Some feed-grain crops such as sorghum also have significant BNI capacity present in their root systems. The chemical identity of some of these BNIs has now been established, and their mode of inhibitory action on Nitrosomonas has been characterized. The ability of the BNI function in Brachiaria pastures to suppress N2O emissions and soil nitrification potential has been demonstrated; however, its potential role in controlling N2O emissions in agro-pastoral systems is under investigation. Here we present the current status of our understanding on how the BNI functions in Brachiaria pastures and feed-grain crops such as sorghum can be exploited both genetically and, from a production system's perspective, to develop low-nitrifying and low N2O-emitting production systems that would be economically profitable and

  5. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps......, to location-based social networks and games, such as Foursquare and facebook. Warns of the threats these technologies, such as data surveillance, present to our sense of privacy, while also outlining the opportunities for pro-social developments. Provides a theory of the web in the context of the history...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  6. The effect of modifying rooting depths and nitrification inhibitors on nutrient uptake from organic biogas residues in maize

    Science.gov (United States)

    Dietrich, Charlotte C.; Koller, Robert; Nagel, Kerstin A.; Schickling, Anke; Schrey, Silvia D.; Jablonowski, Nicolai D.

    2017-04-01

    Optimizing the application of and nutrient uptake from organic nutrient sources, such as the nutrient-rich residues ("digestates") from the biogas industry, is becoming a viable option in remediating fertility on previously unsuitable soils for agricultural utilization. Proposedly, concurrent changes in root system architecture and functioning could also serve as the basis of future phytomining approaches. Herein, we evaluate the effect of spatial nutrient availability and nitrification on maize root architecture and nutrient uptake. We test these effects by applying maize-based digestate at a rate of 170 kg/ha in layers of varying depths (10, 25 and 40 cm) and through either the presence or absence of nitrification inhibitors. In order to regularly monitor above- and below-ground plant biomass production, we used the noninvasive phenotyping platform, GROWSCREEN-Rhizo at the Forschungszentrum Jülich, using rhizotrons (Nagel et al., 2012). Measured parameters included projected plant height and leaf area, as well as root length and spatial distribution. Additionally, root diameters were quantified after the destructive harvest, 21 days after sowing (DAS). Spatial nutrient availability significantly affected root system architecture, as for example root system size -the area occupied by roots- increased alongside nutrient layer depths. Fertilization also positively affected root length density (RLD). Within fertilized layers, the presence of nitrification inhibitors increased RLD by up to 30% and was most pronounced in the fine root biomass fraction (0.1 to 0.5mm). Generally, nitrification inhibitors promoted early plant growth by up to 45% across treatments. However, their effect varied in dependence of layer depths, leading to a time-delayed response in deeper layers, accounting for plants having to grow significantly longer roots in order to reach fertilized substrate. Nitrification inhibitors also initiated the comparatively early on-set of growth differences in

  7. Effects of dynamic operating conditions on nitrification in biological rapid sand filters for drinking water treatment

    DEFF Research Database (Denmark)

    Lee, Carson Odell; Boe-Hansen, Rasmus; Musovic, Sanin

    2014-01-01

    Biological rapid sand filters are often used to remove ammonium from groundwater for drinking water supply. They often operate under dynamic substrate and hydraulic loading conditions, which can lead to increased levels of ammonium and nitrite in the effluent. To determine the maximum nitrification...... operating conditions. The ammonium removal rate of the filter was determined by the ammonium loading rate, but was independent of both the flow and influent ammonium concentration individually. Ammonia-oxidizing bacteria and archaea were almost equally abundant in the filter. Both ammonium removal...... rates and safe operating windows of rapid sand filters, a pilot scale rapid sand filter was used to test short-term increased ammonium loads, set by varying either influent ammonium concentrations or hydraulic loading rates. Ammonium and iron (flock) removal were consistent between the pilot...

  8. Nitrification in trickling filters applied to the post-treatment of effluents from UASB reactor: correlation between ammonia removal and the relative abundance of nitrifying bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Missagia, B. S.; Almeida, P. G. S. de; Silva, S. Q.; Chernicharo, C. A. L.

    2009-07-01

    The number and physiological activity of nitrifying bacteria in wastewater treatment reactors are considered the ratelimiting parameters for the bioconversion of nitrogen in sewage. Since the presence of ammonia and nitrite oxidizers can be correlated with their activity. In situ probe counts can be correlated with the nitrification rates in order to compare the efficiency of different media types. (Author)

  9. Nitrification in trickling filters applied to the post-treatment of effluents from UASB reactor: correlation between ammonia removal and the relative abundance of nitrifying bacteria

    International Nuclear Information System (INIS)

    Missagia, B. S.; Almeida, P. G. S. de; Silva, S. Q.; Chernicharo, C. A. L.

    2009-01-01

    The number and physiological activity of nitrifying bacteria in wastewater treatment reactors are considered the ratelimiting parameters for the bioconversion of nitrogen in sewage. Since the presence of ammonia and nitrite oxidizers can be correlated with their activity. In situ probe counts can be correlated with the nitrification rates in order to compare the efficiency of different media types. (Author)

  10. Growth modelling of Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25391: A new online indicator of the partial nitrification.

    Science.gov (United States)

    Cruvellier, Nelly; Poughon, Laurent; Creuly, Catherine; Dussap, C-Gilles; Lasseur, Christophe

    2016-11-01

    The aim of the present work was to study the growth of two nitrifying bacteria. For modelling the nitrifying subsystem of the MELiSSA loop, Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25931 were grown separately and in cocultures. The kinetic parameters of a stoichiometric mass balanced Pirt model were identified: μmax=0.054h(-1), decay rate b=0.003h(-1) and maintenance rate m=0.135gN-NH4(+)·gX(-1)·h(-1) for Nitrosomonas europaea; μmax=0.024h(-1), b=0.001h(-1) and m=0.467gN-NO2(-)·gX(-1)·h(-1) for Nitrobacter winogradskyi. A predictive structured model of nitrification in co-culture was developed. The online evolution of the addition of KOH is correlated to the nitritation; the dissolved oxygen concentration is correlated to both nitritation and nitratation. The model suitably represents these two variables so that transient partial nitrification is assessed. This is a clue for avoiding partial nitrification by predictive functional control. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Global sensitivity analysis for identifying important parameters of nitrogen nitrification and denitrification under model uncertainty and scenario uncertainty

    Science.gov (United States)

    Chen, Zhuowei; Shi, Liangsheng; Ye, Ming; Zhu, Yan; Yang, Jinzhong

    2018-06-01

    Nitrogen reactive transport modeling is subject to uncertainty in model parameters, structures, and scenarios. By using a new variance-based global sensitivity analysis method, this paper identifies important parameters for nitrogen reactive transport with simultaneous consideration of these three uncertainties. A combination of three scenarios of soil temperature and two scenarios of soil moisture creates a total of six scenarios. Four alternative models describing the effect of soil temperature and moisture content are used to evaluate the reduction functions used for calculating actual reaction rates. The results show that for nitrogen reactive transport problem, parameter importance varies substantially among different models and scenarios. Denitrification and nitrification process is sensitive to soil moisture content status rather than to the moisture function parameter. Nitrification process becomes more important at low moisture content and low temperature. However, the changing importance of nitrification activity with respect to temperature change highly relies on the selected model. Model-averaging is suggested to assess the nitrification (or denitrification) contribution by reducing the possible model error. Despite the introduction of biochemical heterogeneity or not, fairly consistent parameter importance rank is obtained in this study: optimal denitrification rate (Kden) is the most important parameter; reference temperature (Tr) is more important than temperature coefficient (Q10); empirical constant in moisture response function (m) is the least important one. Vertical distribution of soil moisture but not temperature plays predominant role controlling nitrogen reaction. This study provides insight into the nitrogen reactive transport modeling and demonstrates an effective strategy of selecting the important parameters when future temperature and soil moisture carry uncertainties or when modelers face with multiple ways of establishing nitrogen

  12. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam John; Glud, R.N.; Cardenas, M.B.

    2013-01-01

    - and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....

  13. Toxicity of Nitrification Inhibitors on Dehydrogenase Activity in Soils

    OpenAIRE

    Ferisman Tindaon; Gero Benckiser; Johannes C. G. Ottow

    2011-01-01

    The objective of this research was to determine the effects of nitrification inhibitors (NIs) such as 3,4-dimethylpyrazolephosphate=DMPP, 4-Chlor-methylpyrazole phosphate=ClMPP and dicyandiamide,DCD) which might be expected to inhibit microbial activity, on dehydrogenase activity (DRA),in three different soils in laboratory conditions. Dehydrogenase activity were assessed via reduction of 2-p-Iodophenyl-3-p-nitrophenyl-5-phenyltetrazoliumchloride (INT). The toxicity and dose response curve of...

  14. Diurnal changes of net photosynthetic rate (NPR) in leaves of Lonicera japonica Thunb. and the responding mathematical model of NPR to photosynthetic valid radiation

    International Nuclear Information System (INIS)

    Wu Dafu; Zhang Shengli; Li Dongfang

    2009-01-01

    [Objective] The study provided theoretical basis for production practice . [Method] With Lonicera japonica Thunb .as material, diurnal changes of net photosynthetic rate (NPR) in leaves of the plant and the responding mathematical model of NPR to photosynthetic valid radiation were studied using portable photosynthetic determinator system. [Result] Like most of C3 plants, the diurnal changes curve of NPR of Lonicera japonica Thunb .showed double peaks, but there were time difference in reaching the peak value between the study and previous ones . The responding mathematical model of NPR to photosynthetic valid radiation could be described by three mathematic functions, such as logarithm, linearity and binomial, but binomial function was more precise than the others. Light saturation point of Lonicera japonica Thunb. was figured out by binomial equation deduced in the study , and light saturation point was 1 086 .3 μmol/ (m2•s) . [Conclusion] The diurnal changes curve of NPR of Lonicera japonica Thunb .showed double peaks, and the responding mathematical model of NPR to photosynthetic valid radiation could be described by binomial functions

  15. Heterotrophic nitrification and aerobic denitrification bacterium ...

    African Journals Online (AJOL)

    Jane

    2011-07-18

    Jul 18, 2011 ... nutrient agar plates 3 times from the enrichment liquid medium. The isolates ..... growing in the logarithmic phase, the decomposition rate was higher than .... denitrification in bench-scale sequencing batch reactors. Water Res.

  16. Simultaneous nitrification-denitrification achieved by an innovative internal-loop airlift MBR: comparative study.

    Science.gov (United States)

    Li, Y Z; He, Y L; Ohandja, D G; Ji, J; Li, J F; Zhou, T

    2008-09-01

    This study assessed the performance of different single-stage continuous aerated submerged membrane bioreactors (MBR) for nitrogen removal. Almost complete nitrification was achieved in each MBR irrespective of operating mode and biomass system. Denitrification was found to be the rate-limiting step for total nitrogen (T-N) removal. The MBR with internal-loop airlift reactor (ALR) configuration performed better as regards T-N removal compared with continuous stirred-tank reactor (CSTR). It was demonstrated that simultaneous nitrification and denitrification (SND) is the mechanism leading to nitrogen removal and the contribution of microenvironment on SND is more remarkable for the MBRs with hybrid biomass. Macroenvironment analyses showed that gradient distribution of dissolved oxygen (DO) level in airlift MBRs imposed a significant effect on SND. Higher mixed liquor suspended solid (MLSS) concentration led to the improvement in T-N removal by enhancing anoxic microenvironment. Apparent nitrite accumulation coupled with higher nitrogen reduction was accomplished at MLSS concentration exceeded 12.6 g/L.

  17. Parametric Net Influx Rate Images of 68Ga-DOTATOC and 68Ga-DOTATATE: Quantitative Accuracy and Improved Image Contrast.

    Science.gov (United States)

    Ilan, Ezgi; Sandström, Mattias; Velikyan, Irina; Sundin, Anders; Eriksson, Barbro; Lubberink, Mark

    2017-05-01

    68 Ga-DOTATOC and 68 Ga-DOTATATE are radiolabeled somatostatin analogs used for the diagnosis of somatostatin receptor-expressing neuroendocrine tumors (NETs), and SUV measurements are suggested for treatment monitoring. However, changes in net influx rate ( K i ) may better reflect treatment effects than those of the SUV, and accordingly there is a need to compute parametric images showing K i at the voxel level. The aim of this study was to evaluate parametric methods for computation of parametric K i images by comparison to volume of interest (VOI)-based methods and to assess image contrast in terms of tumor-to-liver ratio. Methods: Ten patients with metastatic NETs underwent a 45-min dynamic PET examination followed by whole-body PET/CT at 1 h after injection of 68 Ga-DOTATOC and 68 Ga-DOTATATE on consecutive days. Parametric K i images were computed using a basis function method (BFM) implementation of the 2-tissue-irreversible-compartment model and the Patlak method using a descending aorta image-derived input function, and mean tumor K i values were determined for 50% isocontour VOIs and compared with K i values based on nonlinear regression (NLR) of the whole-VOI time-activity curve. A subsample of healthy liver was delineated in the whole-body and K i images, and tumor-to-liver ratios were calculated to evaluate image contrast. Correlation ( R 2 ) and agreement between VOI-based and parametric K i values were assessed using regression and Bland-Altman analysis. Results: The R 2 between NLR-based and parametric image-based (BFM) tumor K i values was 0.98 (slope, 0.81) and 0.97 (slope, 0.88) for 68 Ga-DOTATOC and 68 Ga-DOTATATE, respectively. For Patlak analysis, the R 2 between NLR-based and parametric-based (Patlak) tumor K i was 0.95 (slope, 0.71) and 0.92 (slope, 0.74) for 68 Ga-DOTATOC and 68 Ga-DOTATATE, respectively. There was no bias between NLR and parametric-based K i values. Tumor-to-liver contrast was 1.6 and 2.0 times higher in the parametric

  18. Stratification of nitrification activity in rapid sand filters for drinking water treatment

    DEFF Research Database (Denmark)

    Tatari, Karolina; Smets, Barth F.; Musovic, Sanin

    2013-01-01

    Rapid sand filters used in groundwater treatment remove ammonium, iron and manganese from the water. Ammonium is removed biologically by nitrifying microorganisms attached on the sand surface. Nitrification kinetics and activity is strongly affected by filter design and operation, which are the key...... and maximum nitrification capacity are derived and used to quantify nitrification activity. Nitrification activity was concentrated at the top 10 cm of filter depth, and maximum nitrification capacity was 7 g NH4+-N/ m3 sand/h compared with 0.8-0.4 g NH4+-N/ m3 sand/h in the middle and bottom layers. A water...... of this study is to investigate nitrification activity in a rapid sand filter, with focus on its homogeneity and how it relates to filter performance. Two groundwater treatment plants in Denmark were selected for the experimental investigations. Plant 1 operates a single line of pre and after filters and has...

  19. Assessment of nitrogen and oxygen isotopic fractionation during nitrification and its expression in the marine environment.

    Science.gov (United States)

    Casciotti, Karen L; Buchwald, Carolyn; Santoro, Alyson E; Frame, Caitlin

    2011-01-01

    Nitrification is a microbially-catalyzed process whereby ammonia (NH(3)) is oxidized to nitrite (NO(2)(-)) and subsequently to nitrate (NO(3)(-)). It is also responsible for production of nitrous oxide (N(2)O), a climatically important greenhouse gas. Because the microbes responsible for nitrification are primarily autotrophic, nitrification provides a unique link between the carbon and nitrogen cycles. Nitrogen and oxygen stable isotope ratios have provided insights into where nitrification contributes to the availability of NO(2)(-) and NO(3)(-), and where it constitutes a significant source of N(2)O. This chapter describes methods for determining kinetic isotope effects involved with ammonia oxidation and nitrite oxidation, the two independent steps in the nitrification process, and their expression in the marine environment. It also outlines some remaining questions and issues related to isotopic fractionation during nitrification. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Uncertainties in the Value of Bill Savings from Behind-the-Meter, Residential Photovoltaic Systems: The Roles of Electricity Market Conditions, Retail Rate Design, and Net Metering

    OpenAIRE

    Darghouth, Naim Richard

    2013-01-01

    Net metering has become a widespread policy mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), allowing customers with PV systems to reduce their electric bills by offsetting their consumption with PV generation, independent of the timing of the generation relative to consumption. Although net metering is one of the principal drivers for the residential PV market in the U.S., the academic literature on this policy has been sparse and this dissertation co...

  1. Remediation of incomplete nitrification and capacity increase of biofilters at different drinking water treatment plants through copper dosing.

    Science.gov (United States)

    Wagner, Florian B; Nielsen, Peter Borch; Boe-Hansen, Rasmus; Albrechtsen, Hans-Jørgen

    2018-04-01

    Drinking water treatment plants based on groundwater may suffer from incomplete ammonium removal, which deteriorates drinking water quality and constrains water utilities in the operation of their plants. Ammonium is normally removed through nitrification in biological granular media filters, and recent studies have demonstrated that dosing of copper can stimulate the removal of ammonium. Here, we investigated if copper dosing could generically improve ammonium removal of biofilters, at treatment plants with different characteristics. Copper was dosed at ≤1.5 μg Cu/L to biofilters at 10 groundwater treatment plants, all of which had displayed several years of incomplete nitrification. Plants exceeded the Danish national water quality standard of 0.05 mg NH 4 + /L by a factor of 2-12. Within only 2-3 weeks of dosing, ammonium removal rates increased significantly (up to 150%). Nitrification was fully established, with ammonium effluent concentrations of plants, regardless of the differences in raw water chemistry, ammonium loading rates, filter design and operation, or treatment plant configuration. However, for filters without primary filtration, it took longer time to reach complete ammonium removal than for filters receiving prefiltered water, likely due to sorption of copper to iron oxides, at plants without prefiltration. With complete ammonium removal, we subjected two plants to short-term loading rate upshifts, to examine the filters' ability to cope with loading rate variations. After 2 months of dosing and an average loading rate of 1.0 g NH 4 + -N/m 3 filter material/h, the loading rate was upshifted by 50%. Yet, a filter managed to completely remove all the influent ammonium, showing that with copper dosing the filter had extra capacity to remove ammonium even beyond its normal loading rates. Depth sampling revealed that the ammonium removal rate of the filter's upper 10 cm increased more than 7-fold from 0.67 to 4.90 g NH 4 + -N/m 3 /h, and

  2. Trait-based representation of biological nitrification: Model development, testing, and predicted community composition

    Directory of Open Access Journals (Sweden)

    Nick eBouskill

    2012-10-01

    Full Text Available Trait-based microbial models show clear promise as tools to represent the diversity and activity of microorganisms across ecosystem gradients. These models parameterize specific traits that determine the relative fitness of an ‘organism’ in a given environment, and represent the complexity of biological systems across temporal and spatial scales. In this study we introduce a microbial community trait-based modeling framework (MicroTrait focused on nitrification (MicroTrait-N that represents the ammonia-oxidizing bacteria (AOB and ammonia-oxidizing archaea (AOA and nitrite oxidizing bacteria (NOB using traits related to enzyme kinetics and physiological properties. We used this model to predict nitrifier diversity, ammonia (NH3 oxidation rates and nitrous oxide (N2O production across pH, temperature and substrate gradients. Predicted nitrifier diversity was predominantly determined by temperature and substrate availability, the latter was strongly influenced by pH. The model predicted that transient N2O production rates are maximized by a decoupling of the AOB and NOB communities, resulting in an accumulation and detoxification of nitrite to N2O by AOB. However, cumulative N2O production (over six month simulations is maximized in a system where the relationship between AOB and NOB is maintained. When the reactions uncouple, the AOB become unstable and biomass declines rapidly, resulting in decreased NH3 oxidation and N2O production. We evaluated this model against site level chemical datasets from the interior of Alaska and accurately simulated NH3 oxidation rates and the relative ratio of AOA:AOB biomass. The predicted community structure and activity indicate (a parameterization of a small number of traits may be sufficient to broadly characterize nitrifying community structure and (b changing decadal trends in climate and edaphic conditions could impact nitrification rates in ways that are not captured by extant biogeochemical models.

  3. Enhancing nitrification at low temperature with zeolite in a mining operations retention pond.

    Science.gov (United States)

    Miazga-Rodriguez, Misha; Han, Sukkyun; Yakiwchuk, Brian; Wei, Kai; English, Colleen; Bourn, Steven; Bohnert, Seth; Stein, Lisa Y

    2012-01-01

    Ammonium nitrate explosives are used in mining operations at Diavik Diamond Mines Inc. in the Northwest Territories, Canada. Residual nitrogen is washed into the mine pit and piped to a nearby retention pond where its removal is accomplished by microbial activity prior to a final water treatment step and release into the sub-Arctic lake, Lac de Gras. Microbial removal of ammonium in the retention pond is rapid during the brief ice-free summer, but often slows under ice cover that persists up to 9 months of the year. The aluminosilicate mineral zeolite was tested as an additive to retention pond water to increase rates of ammonium removal at 4°C. Water samples were collected across the length of the retention pond monthly over a year. The structure of the microbial community (bacteria, archaea, and eukarya), as determined by denaturing gradient gel electrophoresis of PCR-amplified small subunit ribosomal RNA genes, was more stable during cold months than during July-September, when there was a marked phytoplankton bloom. Of the ammonia-oxidizing community, only bacterial amoA genes were consistently detected. Zeolite (10 g) was added to retention pond water (100 mL) amended with 5 mM ammonium and incubated at 12°C to encourage development of a nitrifying biofilm. The biofilm community was composed of different amoA phylotypes from those identified in gene clone libraries of native water samples. Zeolite biofilm was added to fresh water samples collected at different times of the year, resulting in a significant increase in laboratory measurements of potential nitrification activity at 4°C. A significant positive correlation between the amount of zeolite biofilm and potential nitrification activity was observed; rates were unaffected in incubations containing 1-20 mM ammonium. Addition of zeolite to retention ponds in cold environments could effectively increase nitrification rates year-round by concentrating active nitrifying biomass.

  4. Analysis of Microbial Communities in Biofilms from CSTR-Type Hollow Fiber Membrane Biofilm Reactors for Autotrophic Nitrification and Hydrogenotrophic Denitrification.

    Science.gov (United States)

    Shin, Jung-Hun; Kim, Byung-Chun; Choi, Okkyoung; Kim, Hyunook; Sang, Byoung-In

    2015-10-01

    Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH4(+)-N/m(3)/d and 0.10-0.21 kg NO3(-)-N/m(3)/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH4(+) or NO3(-) loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

  5. The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

    Directory of Open Access Journals (Sweden)

    M. Alkhatib

    2012-05-01

    Full Text Available The nitrogen (N stable isotopic composition of pore water nitrate and total dissolved N (TDN was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. N isotope effects on the water column associated with the benthic exchange of nitrate (εapp and TDN (εsed during benthic nitrification-denitrification coupling were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+. We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net fixed N loss was barely expressed at the scale of sediment-water exchange, with ϵapp values <3‰. The strongest under-expression (i.e. lowest εapp of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate εapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of εsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly elevate εsed above εapp. Calculated εsed values were within the range of 4.6 ± 2

  6. Impact of solid retention time and nitrification capacity on the ability of activated sludge to remove pharmaceuticals

    DEFF Research Database (Denmark)

    Falås, Per; Andersen, Henrik Rasmus; Ledin, Anna

    2012-01-01

    Removal of five acidic pharmaceuticals (ibuprofen, ketoprofen, naproxen, diclofenac and clofibric acid) by activated sludge from five municipal activated sludge treatment processes, with various sludge ages and nitrification capacities, was assessed through batch experiments. The increase...... in aerobic sludge age from 1-3 to 7 days seemed to be critical for the removal of naproxen and ketoprofen, with markedly higher rates of removal at sludge ages of 7 days or more. No removal was shown for diclofenac and clofibric acid, while high rates were observed for ibuprofen in all investigated sludges...

  7. Nitrogen management and nitrification inhibitor effects on nitrogen-15 urea: 2. Nitrogen leaching and balance

    International Nuclear Information System (INIS)

    Walters, D.T.; Malzer, G.L.

    1990-01-01

    Nitrification inhibitors (NI) may reduce N leaching losses, and should have the greatest effect on sandy soils where leaching potential is high. This study used 27 lysimeters to evaluate the effect of a NI, nitrapyrin [2-chloro-6(trichloromethyl) pyridine], on soil water percolation (SWP) and N leaching losses from an irrigated sandy loam soil (Typic Hapludoll) planted with corn (Zea mays L.), and monitor the fate of a single application of 15 N-enriched urea over a multiyear period. Urea was applied at 90 and 180 kg N ha -1 yr -1 for a 3-yr period, with and without NI, and with and without incorporation. Urea + NI reduced SWP between planting and silking in 2 out of 3 yr when growing degree days (GDD) were high. After silking, SWP was reduced when urea + NI was incorporated and leaching load was high. A twofold increase in N rate resulted in an average of 3.4 times more N leached over 3 yr. The NI influenced time of N loss but not total N loss. Leaching losses of fertilizer-derived N (FDN) were delayed 25 to 50d when urea + NI were incorporated. The leaching load required to reach the maximum rate of FDN loss was higher with urea + NI. Leaching losses of fertilizer N were three times greater when determined by the difference method than by isotope-ratio analysis. Differing results with these two calculations are attributed to isotope dilution with indigenous soil N as a result of microbial activity. Nitrification inhibitors may reduce the potential for nonpoint-source pollution by delaying NO 3 leaching, but will be most effective if coupled with proper N rates and conservative irrigation water management

  8. Profitability of Nitrification Inhibitors for Abatement of Nitrate Leaching on a Representative Dairy Farm in the Waikato Region of New Zealand

    Directory of Open Access Journals (Sweden)

    Upa H. Paragahawewa

    2011-11-01

    Full Text Available Direct policies for the management of nonpoint source pollution are difficult to apply given asymmetric information, spatial and temporal variability, and uncertainty. There is increasing awareness that these limitations may be overcome where profitable mitigation practices are broadly adopted by polluters. Nitrification inhibitors (chemicals applied to paddocks that retard the nitrification process in soils are a rare example of a mitigation practice that reduces pollutant loads and potentially increases farm profit through promoting pasture production. This study investigates their capacity to achieve both goals to inform policy makers and producers of their potential for simultaneously improving farm profit and water quality. With an assumed 10 percent increase in pasture production in response to nitrification inhibitor application, nitrification inhibitors are a profitable innovation because greater pasture production supports higher stocking rates. Nonetheless, their overall impact on farm profit is low, even when the cost of inhibitors or their impact on subsequent pasture production is substantially altered. However, inhibitors are found to be a critical mitigation practice for farmers posed with decreasing leaching loads to satisfy regulatory requirements. These findings suggest that, despite their shortcomings for nonpoint pollution regulation, direct policies appear to be the only way to motivate producers to account for their impact on environmental values given the current lack of profitable mitigations.

  9. Osmotic stress on nitrification in an airlift bioreactor

    International Nuclear Information System (INIS)

    Jin Rencun; Zheng Ping; Mahmood, Qaisar; Hu Baolan

    2007-01-01

    The effect of osmotic pressure on nitrification was studied in a lab-scale internal-loop airlift-nitrifying reactor. The reactor slowly adapted to the escalating osmotic pressure during 270 days operation. The conditions were reversed to the initial stage upon full inhibition of the process. Keeping influent ammonium concentration constant at 420 mg N L -1 and hydraulic retention time at 20.7 h, with gradual increase in osmotic pressure from 4.3 to 18.8 x 10 5 Pa by adding sodium sulphate, the ammonium removal efficiencies of the nitrifying bioreactor were maintained at 93-100%. Further increase in osmotic pressure up to 19.2 x 10 5 Pa resulted in drop of the ammonium conversion to 69.2%. The osmotic pressure caused abrupt inhibition of nitrification without any alarm and the critical osmotic pressure value causing inhibition remained between 18.8 and 19.2 x 10 5 Pa. Nitrite oxidizers were found more sensitive to osmotic stress as compared with ammonia oxidizers, leading to nitrite accumulation up to 61.7% in the reactor. The performance of bioreactor recovered gradually upon lowering the osmotic pressure. Scanning and transmission electron microscopy indicated that osmotic stress resulted in simplification of the nitrifying bacterial populations in the activated sludge as the cellular size reduced; the inner membrane became thinner and some unknown inclusions appeared within the cells. The microbial morphology and cellular structure restored upon relieving the osmotic pressure. Addition of potassium relieved the effect of osmotic pressure upon nitrification. Results demonstrate that the nitrifying reactor possesses the potential to treat ammonium-rich brines after acclimatization

  10. Analisis Determinan Net Ekspor Indonesia

    OpenAIRE

    Daulay, Rahmawaty

    2010-01-01

    This study is to analyzing empirically among Indonesia GDP, trade partnership GDP (Malaysia, Singapore, US and Thailand) and real exchange rate toward Indonesia Net Export. To find out which one from those three variables is significant in order to fluctuating (increasing or decreasing) Indonesia Net Export either in the short run or in the long run. Data collection is obtained using secondary data, namely Indonesia GDP, Malaysia GDP, Singapura GDP, US GDP, Thailand GDP and real exchange rate...

  11. Nitrification inhibition as measured by RNA- and DNA-based function-specific assays and microbial community structure analyses

    Science.gov (United States)

    Abstract: The biological removal of ammonia in conventional wastewater treatment plants (WWTPs) is performed by promoting nitrification, which transforms ammonia into nitrate, which in turn is converted into nitrogen gas by denitrifying bacteria. The first step in nitrification, ...

  12. Effect of heavy metals on nitrification performance in different activated sludge processes

    International Nuclear Information System (INIS)

    You, Sheng-Jie; Tsai, Yung-Pin; Huang, Ru-Yi

    2009-01-01

    To understand the toxic effect of heavy metals on the nitrification mechanisms of activated sludge, this study identified the specific ammonia utilization rate (SAUR) inhibited by Pb, Ni and/or Cd shock loadings. Seven different heavy metal combinations (Pb, Ni, Cd, Pb + Ni, Ni + Cd, Pb + Cd, and Pb + Ni + Cd) with seven different heavy metal concentrations (0, 2, 5, 10, 15, 25, and 40 ppm, respectively) were examined by batch experiments, where the activated sludge was taken from either sequencing batch reactor (SBR) or anaerobic-anoxic-oxic (A 2 O) processes. The experimental results showed the SAUR inhibition rate was Ni > Cd > Pb. No significant inhibition in the nitrification reaction of the activated sludge was observed even when as much as 40 ppm Pb was added. In addition, no synergistic effect was found when different heavy metals were simultaneously added in different concentrations, and the overall inhibition effect depended on the heavy metal with the highest toxicity. Further, first order kinetic reaction could model the behavior of SAUR inhibition on activated sludge when adding heavy metals, and the SAUR inhibition formula was derived as SAUR=(SAUR max -SAUR min )xe -r i c +SAUR min . On the other hand, the heavy metal adsorption ability in both the activated sludge system was Pb = Cd > Ni. The specific adsorption capacity of activated sludge on heavy metal increased as the heavy metal concentration increased or the mixed liquid volatile suspended solid (MLVSS) decreased. The batch experiments also showed the heavy metal adsorption capacity of the SBR sludge was larger than the A 2 O sludge. Finally, the most predominant bacteria in the phylogenetic trees of SBR and A 2 O activated sludges were proteobacteria, which contributed to 42.1% and 42.8% of the total clones.

  13. Relationship between respiratory quotient, nitrification, and nitrous oxide emissions in a forced aerated composting process

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsui, Hirofumi, E-mail: jm-tsutsuih@kochi-u.ac.jp [Research and Education Faculty, Natural Sciences Cluster, Agriculture Unit, Kochi University, B200 Monobe, Nankoku, Kochi (Japan); Japan Science and Technology Agency, CREST (Japan); Fujiwara, Taku [Research and Education Faculty, Natural Sciences Cluster, Agriculture Unit, Kochi University, B200 Monobe, Nankoku, Kochi (Japan); Japan Science and Technology Agency, CREST (Japan); Inoue, Daisuke [Department of Health Science, School of Allied Health Sciences, Kitasato University, 1-15-1 Kitasato, Sagamihara-Minami, Kanagawa (Japan); Japan Science and Technology Agency, CREST (Japan); Ito, Ryusei [Department of Environmental Engineering, Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido (Japan); Japan Science and Technology Agency, CREST (Japan); Matsukawa, Kazutsugu [Research and Education Faculty, Multidisciplinary Science Cluster, Life and Environmental Medicine Science Unit, Kochi University, B200 Monobe, Nankoku, Kochi (Japan); Japan Science and Technology Agency, CREST (Japan); Funamizu, Naoyuki [Department of Environmental Engineering, Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido (Japan); Japan Science and Technology Agency, CREST (Japan)

    2015-08-15

    Highlights: • RQ can be an indicator of N{sub 2}O emission in forced aerated composting process. • Emission of N{sub 2}O with nitrification was observed with RQ decrease. • Mass balances demonstrated the RQ decrease was caused by nitrification. • Conversion ratio of oxidized ammonia and total N to N{sub 2}O were ∼2.7%. - Abstract: We assessed the relationship between respiratory quotient (RQ) and nitrification and nitrous oxide (N{sub 2}O) emission in forced aerated composting using lab-scale reactors. Relatively high RQ values from degradation of readily degradable organics initially occurred. RQ then stabilized at slightly lower values, then decreased. Continuous emission of N{sub 2}O was observed during the RQ decrease. Correlation between nitrification and N{sub 2}O emission shows that the latter was triggered by nitrification. Mass balances demonstrated that the O{sub 2} consumption of nitrification (∼24.8 mmol) was slightly higher than that of CO{sub 2} emission (∼20.0 mmol), indicating that the RQ decrease was caused by the occurrence of nitrification. Results indicate that RQ is a useful index, which not only reflects the bioavailability of organics but also predicts the occurrence of nitrification and N{sub 2}O emission in forced aerated composting.

  14. Optimizing nitrification in biological rapid sand filters: Diagnosing and supplementing micronutrients needed for proper filter performance

    DEFF Research Database (Denmark)

    Lee, Carson Odell; Wagner, Florian Benedikt; Boe-Hansen, Rasmus

    Nitrification is an important biological process commonly used in biological drinking water filters to remove ammonium from drinking water. Recent research has shown that a lack of micronutrients could be limiting the performance of these filters. Because nitrification is a biological process, ca...... to be an important diagnostic tool that could decrease regulatory hurdles, and save time and money....

  15. Adaptation and monitoring of microorganisms in petroleum industry wastewater nitrification processes

    Directory of Open Access Journals (Sweden)

    A. Madero

    1998-07-01

    Full Text Available Biological removal of ammonia nitrogen is carried out in two successive stages, nitrification and denitrification. This work studied the nitrification process on microorganisms isolated from different aquifer sources: a eutrophicate pond and residual waters from two treatment plants (petrochemical and domestic

  16. An Operations Manual for Achieving Nitrification in an Activated Sludge Plant.

    Science.gov (United States)

    Ontario Ministry of the Environment, Toronto.

    In Ontario, the attainment of nitrification (oxidation of ammonia) in activated sludge plants is receiving increased attention. Nitrification of waste water is a necessary requirement because it reduces plant discharge of nitrogenous oxygen demand and/or toxic ammonia. However, this new requirement will result in added responsibility for…

  17. Nitrogen cycling process rates across urban ecosystems.

    Science.gov (United States)

    Reisinger, Alexander J; Groffman, Peter M; Rosi-Marshall, Emma J

    2016-09-21

    Nitrogen (N) pollution of freshwater, estuarine, and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems which can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on watershed-scale mass balances. Comparisons of specific N transformations across ecosystems are required to contextualize rates from individual studies. Here we reviewed urban N cycling in terrestrial, aquatic, and engineered ecosystems, and compared N processing in these urban ecosystem types to native reference ecosystems. We found that net N mineralization and net nitrification rates were enhanced in urban forests and riparian zones relative to reference ecosystems. Denitrification was highly variable across urban ecosystem types, but no significant differences were found between urban and reference denitrification rates. When focusing on urban streams, ammonium uptake was more rapid than nitrate uptake in urban streams. Additionally, reduction of stormwater runoff coupled with potential decreases in N concentration suggests that green infrastructure may reduce downstream N export. Despite multiple environmental stressors in urban environments, ecosystems within urban watersheds can process and transform N at rates similar to or higher than reference ecosystems. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. Importance of copper for nitrification in biological rapid sand filters for drinking water production

    DEFF Research Database (Denmark)

    Wagner, Florian Benedikt

    When anoxic groundwater is treated to produce drinking water, ammonium is commonly removed through nitrification in rapid sand filters. Nitrification is a biological process, and is mediated by chemoautotrophic microorganisms. Ammonia oxidizing bacteria (AOB) and archaea (AOA) oxidize ammonium...... to remove ammonium to below the national drinking water quality standard of 0.05 mg NH4+/L. A better process understanding of nitrifying biofilters is needed to optimize treatment performance, remediate existing filters, and to prevent future nitrification problems. The frequent incidents of insufficient...... in the oxidation of ammonia to hydroxylamine. Thus, slow and incomplete nitrification could be caused by a lack of sufficient amounts of copper. The overall aim of this PhD project was therefore to determine whether copper supplementation could enhance nitrification in rapid sand filters with incomplete...

  19. Brassicaceae tissues as inhibitors of nitrification in soil.

    Science.gov (United States)

    Brown, Paul D; Morra, Matthew J

    2009-09-09

    Brassicaceae crops often produce an unexplained increase in plant-available soil N possibly related to bioactive compounds produced from glucosinolates present in the tissues. Our objective was to determine if glucosinolate-containing tissues inhibit nitrification, thereby potentially explaining this observation. Ammonium, NO(2)(-), and NO(3)(-) N were measured in soils amended with Brassicaceae ( Isatis tinctoria L., Brassica napus L., Brassica juncea L., and Sinapis alba L.) tissues containing different glucosinolate types and concentrations or Kentucky bluegrass ( Poa pratensis L.) residues with equivalent C/N ratios as the Brassicaceae samples. There was greater accumulation of NH(4)(+) N in soils amended with tissues containing high glucosinolate concentrations as compared to soils amended with tissues containing no or low glucosinolate concentrations. Nitrite N was detected only in soils amended with Brassicaceae tissues having the highest glucosinolate concentrations. The positive correlation of both NH(4)(+) and NO(2)(-) N accumulation with the glucosinolate concentration indicates the participation of glucosinolate hydrolysis products in nitrification inhibition.

  20. Comparison of Simultaneous Nitrification and Denitrification for Three Different Reactors

    Directory of Open Access Journals (Sweden)

    W. Khanitchaidecha

    2015-01-01

    Full Text Available Discharge of high NH4-N containing wastewater into water bodies has become a critical and serious issue due to its negative impact on water and environmental quality. In this research, the performance of three different reactors was assessed and compared with regard to the removal of NH4-N from wastewater. The highest nitrogen removal efficiency of 98.3% was found when the entrapped sludge reactor (ESR, in which the sludge was entrapped in polyethylene glycol polymer, was used. Under intermittent aeration, nitrification and denitrification occurred simultaneously in the aerobic and anaerobic periods. Moreover, internal carbon was consumed efficiently for denitrification. On the other hand, internal carbon consumption was not found to occur in the suspended sludge reactor (SSR and the mixed sludge reactor (MSR and this resulted in nitrogen removal efficiencies of SSR and MSR being 64.7 and 45.1%, respectively. Nitrification and denitrification were the main nitrogen removal processes in the aerobic and anaerobic periods, respectively. However, due to the absence of sufficient organic carbon, denitrification was uncompleted resulting in high NO3-N contents in the effluent.

  1. Composition of ammonia-oxidizing archaea and their contribution to nitrification in a high-temperature hot spring

    Science.gov (United States)

    Chen, S.; Peng, X.-T.; Xu, H.-C.; Ta, K.-W.

    2015-10-01

    The oxidation of ammonia by microbes and associated organisms has been shown to occur in diverse natural environments. However, the contribution of ammonia-oxidizing archaea to nitrification in high-temperature environments remains unclear. Here, we studied in situ ammonia oxidation rates and the abundance of ammonia-oxidizing archaea (AOA) in surface and bottom sediments at 77 °C in the Gongxiaoshe hot spring, Tengchong, Yunnan, China. The in situ ammonia oxidation rates measured by the 15N-NO3- pool dilution technique in the surface sinter and bottom sediments were 4.8 and 5.3 nmol N g-1 h-1, respectively. Relative abundances of Crenarchaea in both samples were determined by fluorescence in situ hybridization (FISH). Phylogenetic analysis of 16S rRNA genes showed high sequence similarity to thermophilic "Candidatus Nitrosocaldus yellowstonii", which represented the most abundant operation taxonomic units (OTU) in both sediments. Furthermore, bacterial amoA was not detected in this study. Quantitative PCR (qPCR) indicated that AOA and 16S rRNA genes were present in the range of 2.75 to 9.80 × 105 and 0.128 to 1.96 × 108 gene copies g-1 sediment. The cell-specific nitrification rates were estimated to be in the range of 0.41 to 0.79 fmol N archaeal cell-1 h-1, which is consistent with earlier estimates in estuary environments. This study demonstrated that AOA were widely involved in nitrification in this hot spring. It further indicated the importance of archaea rather than bacteria in driving the nitrogen cycle in terrestrial geothermal environments.

  2. Fibrous Support Stabilizes Nitrification Performance of a Membrane-Aerated Biofilm: The Effect of Liquid Flow Perturbation

    DEFF Research Database (Denmark)

    Terada, Akihiko; Ito, J; Matsumoto, S

    2009-01-01

    no boundary layer between the fibrous material and bulk liquid, was 5.85 m/d at an air pressure of 27 kPa, which was comparable to that value of the MABR (5.54 m/d). The amount of biomass on the fibrous support with a silicone tube was 2.48 times larger than on the bare silicone. The biomass loss after a high...... a high liquid flow rate condition to eliminate excessive biomass, indicating that regular maintenance is essential to eliminate excessive biofilm from a MABR for nitrification, which potentially acts as a NH4+ diffusion barrier....

  3. The side effects of nitrification inhibitors on leaching water and soil salinization in a field experiment

    Energy Technology Data Exchange (ETDEWEB)

    Diez, J. A.; Arauzo, M.; Hernaiz, P.; Sanz, A.

    2010-07-01

    In experiments carried out in greenhouses, some authors have shown that ammonium sulphate induces greater soil acidity and salinity than other sources of N. Moreover, nitrification inhibitors (NI) tend to cause ammonium to accumulate in soil by retarding its oxidation to nitrate. This accumulated ammonium would also have an effect on soil salinity. Consequently, the aim of this paper was to evaluate the soil and leaching water salinization effects associated with adding NI, dicyandiamide (DCD) and dimethylpyrazole-phosphate (DMPP) to ammonium sulphate nitrate (ASN) fertilizer. This experiment was carried out in the field with an irrigated maize crop. Drainage and Na concentration were measured during both seasons (2006 and 2007) and leached Na was determined. The treatments with NI (DCD and DMPP) were associated with greater Na concentrations in soil solutions and consequently higher rates of Na leaching (in 2007, ASN-DCD 1,292 kg Na ha{sup -}1, ASN-DMPP 1,019 kg Na ha{sup -}1). A treatment involving only ASN also increased the Na concentration in soil and the amount of Na leached in relation to the Control (in 2007, ASN 928 kg Na ha{sup -}1 and Control 587 kg Na ha{sup -}1). The increase in the ammonium concentration in the soil due to the NI treatments could have been the result of the displacement of Na ions from the soil exchange complex through a process which finally led to an increase in soil salinity. Treatments including ammonium fertilizer formulated with NI produced a greater degree of soil salinization due to the presence of ammonium from the fertilizer and accumulated ammonium from the nitrification inhibition. (Author) 31 refs.

  4. Achieving partial nitrification in a novel six basins alternately operating activated sludge process treating domestic wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Mohammed, Rusul Naseer; Arab, Saad; Xiwu, Lu [Southeast University, Nanjing (China)

    2013-11-15

    A novel technology was developed to achieve partial nitrification at moderately low DO and short HRT, which would save the aeration cost and have the capacity to treat a wide range of low-strength real wastewater. The process enables a relatively stable whereas nitrite accumulation rate (NO{sub 2}-AR) was stabilized over 94% in the last aerobic basin on average of each phase through a combination of short HRT and low DO level. Low DO did not produce sludge with poorer settleability. The morphology and internal structure of the granular sludge was observed by using a scanning electron microscope (SEM) analysis during a long-term operation. The images indicated that thick clusters of spherical cells and small rod-shaped cells (NOB and AOB are rod-shaped to spherical cells) were the dominant population structure, rather than filamentous and other bacteria under a combination of low DO and short HRT, which gives a good indication of nitrite accumulation achievement. MPN method was used to correlate AOB numbers with nutrient removal. It showed that an ammonia-oxidizing bacterium (AOB) was the dominant nitrifying bacteria, whereas high NO{sub 2}-AR was achieved at AOB number of 5.33x10{sup 8} cell/g MLSS. Higher pollutant removal efficiency of 86.2%, 98% and 96.1%, for TN, NH{sub 4}{sup +}-N, and TP, respectively, was achieved by a novel six basin activated sludge process (SBASP) at low DO level and low C/N ratio which were approximately equal to the complete nitrification-denitrification with the addition of sodium acetate (NaAc) at normal DO level of (1.5-2.5 mg/L)

  5. The potential for adaptation in a natural Daphnia magna population: broad and narrow-sense heritability of net reproductive rate under Cd stress at two temperatures.

    Science.gov (United States)

    Messiaen, M; Janssen, C R; Thas, O; De Schamphelaere, K A C

    2012-10-01

    The existence of genetic variability is a key element of the adaptive potential of a natural population to stress. In this study we estimated the additive and non-additive components of the genetic variability of net reproductive rate (R(0)) in a natural Daphnia magna population exposed to Cd stress at two different temperatures. To this end, life-table experiments were conducted with 20 parental and 39 offspring clonal lineages following a 2 × 2 design with Cd concentration (control vs. 3.7 μg Cd/L) and temperature (20 vs. 24 °C) as factors. Offspring lineages were obtained through inter-clonal crossing of the different parental lineages. The population mean, additive and non-additive genetic components of variation in each treatment were estimated by fitting an Animal Model to the observed R(0) values using restricted maximum likelihood estimation. From those estimates broad-sense heritabilities (H(2)), narrow-sense heritabilities (h(2)), total (CV(G)) and additive genetic coefficients of variation (CV(A)) of R(0) were calculated. The exposure to Cd imposed a considerable level of stress to the population, as shown by the fact that the population mean of R(0) exposed to Cd was significantly lower than in the control at the corresponding temperature, i.e. by 23 % at 20 °C and by 88 % at 24 °C. The latter difference indicates that increasing temperature increased the stress level imposed by Cd. The H² and CV(G) were significantly greater than 0 in all treatments, suggesting that there is a considerable degree of genetic determination of R(0) in this population and that clonal selection could rapidly lead to increasing population mean fitness under all investigated conditions. More specifically, the H² was 0.392 at 20 °C+Cd and 0.563 at 24 °C+Cd; the CV(G) was 30.0 % at 20 °C+Cd and was significantly higher (147.6 %) in the 24 °C+Cd treatment. Significant values of h(2) (= 0.23) and CV(A) (= 89.7 %) were only found in the 24 °C+Cd treatment, suggesting

  6. Partial nitrification of non-ammonium-rich wastewater within biofilm filters under ambient temperature.

    Science.gov (United States)

    Wang, Hongyu; He, Jiajie; Yang, Kai

    2010-01-01

    This study evaluated the partial nitrification performances of two biofilm filters over a synthetic non-ammonium-rich wastewater at a 20°C room temperature under both limited DO (∼2.0 mg/L) and unlimited DO (∼4.0 mg/L) conditions. The two filters were each of 80 cm long and used different biofilm carriers: activated carbon and ceramic granule. Results showed that partial nitrification was accomplished for both filters under the limited DO condition. However, the effluent NO(2)-N was higher in the ceramic granule filter than in the activated carbon filter, and was less susceptible to the influent COD/N changes. Further investigation into the water phase COD and NH(4)-N depth profiles and bacteria population within the two filters showed that by putting upper filter layer (upstream) to confront relatively higher influent COD/N ratios, the filtration process naturally put lower filter layers (downstream) relatively more favorable for nitrifying bacteria (ammonia oxidizing bacteria in this study) to prosper, making the filter depth left for nitrification a crucial factor for the effectiveness of nitrification with a filter. The potentially different porous flow velocities of the two filters might be the reason to cause their different partial nitrification performances, with a lower porous flow velocity (the ceramic granule filter) favoring partial nitrification more. In summation, DO, filter depth, and filtration speed should be played together to successfully operate a biofilm filter for partial nitrification.

  7. Is polymeric substrate in influent an indirect impetus for the nitrification process in an activated sludge system?

    Science.gov (United States)

    Wang, Bin-Bin; Gu, Ya-Wei; Chen, Jian-Meng; Yao, Qian; Li, Hui-Juan; Peng, Dang-Cong; He, Feng

    2017-06-01

    Different from monomeric substrate, polymeric substrate (PS) needs to undergo slow hydrolysis process before becoming available for consumption by bacteria. Hydrolysis products will be available for the heterotrophs in low concentration, which will reduce competitive advantages of heterotrophs to nitrifiers in mixed culture. Therefore, some links between PS and nitrification process can be expected. In this study, three lab-scale sequencing batch reactors with different PS/total substrate (TS) ratio (0, 0.5 or 1) in influent were performed in parallel to investigate the influence of PS on nitrification process in activated sludge system. The results showed that with the increase of PS/TS ratio, apparent sludge yields decreased, while NO 3 - -N concentration in effluent increased. The change of PS/TS ratio in influent also altered the cycle behaviors of activated sludge. With the increase of PS/TS ratio from 0 to 0.5 and 1, the ammonium and nitrite utilization rate increased ∼2 and 3 times, respectively. The q-PCR results showed that the abundance of nitrifiers in activated sludge for PS/TS ratio of 0.5 and 1 were 0.7-0.8 and 1.4-1.5 orders of magnitude higher than that for PS/TS ratio of 0. However, the abundance of total bacteria decreased about 0.5 orders of magnitude from the former two to the latter. The FISH observation confirmed that the nitrifiers' microcolony became bigger and more robust with the increase of PS/TS ratio. This paper paves a path to understand the role of PS/TS in affecting the nitrification process in biological wastewater treatment systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Empowering a mesophilic inoculum for thermophilic nitrification: Growth mode and temperature pattern as critical proliferation factors for archaeal ammonia oxidizers.

    Science.gov (United States)

    Courtens, Emilie N P; Vandekerckhove, Tom; Prat, Delphine; Vilchez-Vargas, Ramiro; Vital, Marius; Pieper, Dietmar H; Meerbergen, Ken; Lievens, Bart; Boon, Nico; Vlaeminck, Siegfried E

    2016-04-01

    Cost-efficient biological treatment of warm nitrogenous wastewaters requires the development of thermophilic nitrogen removal processes. Only one thermophilic nitrifying bioreactor was described so far, achieving 200 mg N L(-1) d(-1) after more than 300 days of enrichment from compost samples. From the practical point of view in which existing plants would be upgraded, however, a more time-efficient development strategy based on mesophilic nitrifying sludge is preferred. This study evaluated the adaptive capacities of mesophilic nitrifying sludge for two linear temperature increase patterns (non-oscillating vs. oscillating), two different slopes (0.25 vs. 0.08 °C d(-1)) and two different reactor types (floc vs. biofilm growth). The oscillating temperature pattern (0.25 °C d(-1)) and the moving bed biofilm reactor (0.08 °C d(-1)) could not reach nitrification at temperatures higher than 46 °C. However, nitrification rates up to 800 mg N L(-1) d(-1) and 150 mg N g(-1) volatile suspended solids d(-1) were achieved at a temperature as high as 49 °C by imposing the slowest linear temperature increase to floccular sludge. Microbial community analysis revealed that this successful transition was related with a shift in ammonium oxidizing archaea dominating ammonia oxidizing bacteria, while for nitrite oxidation Nitrospira spp. was constantly more abundant than Nitrobacter spp.. This observation was accompanied with an increase in observed sludge yield and a shift in maximal optimum temperature, determined with ex-situ temperature sensitivity measurements, predicting an upcoming reactor failure at higher temperature. Overall, this study achieved nitrification at 49 °C within 150 days by gradual adaptation of mesophilic sludge, and showed that ex-situ temperature sensitivity screening can be used to monitor and steer the transition process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1987-01-01

    The author describes a Petri net model, called coloured Petri nets (CP-nets), by means of which it is possible to describe large systems without having to cope with unnecessary details. The author introduces CP-nets and provide a first impression of their modeling power and the suitability...

  10. Learning Visual Basic NET

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Learning Visual Basic .NET is a complete introduction to VB.NET and object-oriented programming. By using hundreds of examples, this book demonstrates how to develop various kinds of applications--including those that work with databases--and web services. Learning Visual Basic .NET will help you build a solid foundation in .NET.

  11. Isolation of high-salinity-tolerant bacterial strains, Enterobacter sp., Serratia sp., Yersinia sp., for nitrification and aerobic denitrification under cyanogenic conditions.

    Science.gov (United States)

    Mpongwana, N; Ntwampe, S K O; Mekuto, L; Akinpelu, E A; Dyantyi, S; Mpentshu, Y

    2016-01-01

    Cyanides (CN(-)) and soluble salts could potentially inhibit biological processes in wastewater treatment plants (WWTPs), such as nitrification and denitrification. Cyanide in wastewater can alter metabolic functions of microbial populations in WWTPs, thus significantly inhibiting nitrifier and denitrifier metabolic processes, rendering the water treatment processes ineffective. In this study, bacterial isolates that are tolerant to high salinity conditions, which are capable of nitrification and aerobic denitrification under cyanogenic conditions, were isolated from a poultry slaughterhouse effluent. Three of the bacterial isolates were found to be able to oxidise NH(4)-N in the presence of 65.91 mg/L of free cyanide (CN(-)) under saline conditions, i.e. 4.5% (w/v) NaCl. The isolates I, H and G, were identified as Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Results showed that 81% (I), 71% (G) and 75% (H) of 400 mg/L NH(4)-N was biodegraded (nitrification) within 72 h, with the rates of biodegradation being suitably described by first order reactions, with rate constants being: 4.19 h(-1) (I), 4.21 h(-1) (H) and 3.79 h(-1) (G), respectively, with correlation coefficients ranging between 0.82 and 0.89. Chemical oxygen demand (COD) removal rates were 38% (I), 42% (H) and 48% (G), over a period of 168 h with COD reduction being highest at near neutral pH.

  12. Nitrogen management and nitrification inhibitor effects on nitrogen-15 urea: 1. Yield and fertilizer use efficiency

    International Nuclear Information System (INIS)

    Walters, D.T.; Malzer, G.L.

    1990-01-01

    Nitrification inhibitors (NI) are sometimes recommended for use with ammoniacal fertilizers in corn (Zea mays L.) production to improve fertilizer N use efficiency (FUE). The objectives of this experiment were to evaluate the effects of the NI nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] application on yield and FUE of irrigated corn, and to monitor the fate of a single application of 15 N-enriched urea during a multiyear period in both soil and plant. Treatments included a factorial combination of two N rates (90 or 180 kg urea-N ha -1 yr -1 ) applied during a 3-yr period, with or without a NI and with or without incorporation, plus a zero-N control. Twenty-seven nonweighing lysimeters were used to quantify leaching load. Treatment effects on yield and FUE differed each year due to interactions of climate and N-management variables. Nonincorporated urea + NI reduced grain yield when leaching load was low and increased yield at the 90 kg ha -1 N rate when leaching load was low. The NI increased FUE only at the 90 kg ha -1 N rate when leaching load was high. Incorporation of urea + NI reduced plant recovery of fertilizer-derived N (FDN) in the year of application, but resulted in increased uptake of residual FDN in subsequent years. Incorporation of NI with moderate N rates coupled with conservative irrigation management should reduce the risk of yield loss and minimize NO 3 movement to groundwater

  13. Monitoring the nitrification and identifying the endpoint of ammonium oxidation by using a novel system of titrimetry.

    Science.gov (United States)

    Zhang, Xin; Zhang, Daijun; Lu, Peili; Bai, Cui; Xiao, Pengying

    2011-01-01

    Based on the structure of the hybrid respirometer previously developed in our group, a novel implementation for titrimetry was developed, in which two pH electrodes were installed at the inlet and outlet of the measuring cell. The software capable of digital filtering and titration time delay correction was developed in LabVIEW. The hardware and software of the titrimeter and the respirometer were integrated to construct a novel system of respirometry-titrimetry. The system was applied to monitor a batch nitrification process. The obtained profiles of oxygen uptake rate (OUR) and hydrogen ion production rate (HPR) are consistent with each other and agree with the principle of the biological nitrification reaction. According to the OUR and HPR measurements, the oxidized ammonium concentrations were estimated accurately. Furthermore, the endpoint of ammonium oxidation was identified with much higher sensitivity by the HPR measurement. The system could be potentially used for on-line monitoring of biochemical reactions occurring in any kind of bioreactors because its measuring cell is completely independent of the bioreactor.

  14. Marine N2O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

    Science.gov (United States)

    Battaglia, G.; Joos, F.

    2018-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent; yet global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2-dependent by-product from nitrification in the Bern3D ocean model. A large model ensemble is used to probabilistically constrain modern and to project marine N2O production for a low (Representative Concentration Pathway (RCP)2.6) and high GHG (RCP8.5) scenario extended to A.D. 10,000. Water column N2O and surface ocean partial pressure N2O data serve as constraints in this Bayesian framework. The constrained median for modern N2O production is 4.5 (±1σ range: 3.0 to 6.1) Tg N yr-1, where 4.5% stems from denitrification. Modeled denitrification is 65.1 (40.9 to 91.6) Tg N yr-1, well within current estimates. For high GHG forcing, N2O production decreases by 7.7% over this century due to decreasing organic matter export and remineralization. Thereafter, production increases slowly by 21% due to widespread deoxygenation and high remineralization. Deoxygenation peaks in two millennia, and the global O2 inventory is reduced by a factor of 2 compared to today. Net denitrification is responsible for 7.8% of the long-term increase in N2O production. On millennial timescales, marine N2O emissions constitute a small, positive feedback to climate change. Our simulations reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.

  15. Subsurface aeration of anaerobic groundwater : iron colloid formation and the nitrification process

    NARCIS (Netherlands)

    Wolthoorn, A.

    2003-01-01

    Keywords: Iron, anaerobic groundwater, groundwater purification, heterogeneous oxidation, iron colloid formation, electron microscopy, nitrification In anaerobic groundwater iron and ammonium can be found in relatively high concentrations. These substances need to be removed when groundwater is used

  16. Biofilm Community Dynamics in Bench-Scale Annular Reactors Simulating Arrestment of Chloraminated Drinking Water Nitrification

    Science.gov (United States)

    Annular reactors (ARs) were used to study biofilm community succession and provide an ecological insight during nitrification arrestment through simultaneously increasing monochloramine (NH2Cl) and chlorine to nitrogen mass ratios, resulting in four operational periods (I to IV)....

  17. Drinking Water Microbiome as a Screening Tool for Nitrification in Chloraminated Drinking Water Distribution Systems

    Science.gov (United States)

    Many water utilities in the US using chloramine as disinfectant treatment in their distribution systems have experienced nitrification episodes, which detrimentally impact the water quality. A chloraminated drinking water distribution system (DWDS) simulator was operated throug...

  18. How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input

    Science.gov (United States)

    We conducted a meta-analysis of 103 nitrification inhibitor (NI) studies, and evaluated how NI application affects crop productivity and other ecosystem services in agricultural systems. Our results showed that, compared to conventional fertilizer practice, applications of NI alo...

  19. Engineering hyporheic zones to target nitrification versus denitrification: performance data from constructed stream flumes

    Science.gov (United States)

    Herzog, S.; Portmann, A. C.; Halpin, B. N.; Higgins, C.; McCray, J. E.

    2017-12-01

    Nonpoint source nitrogen pollution from agricultural and urban runoff is one of the leading causes of impairment to US rivers and streams. The hyporheic zone (HZ) offers a natural biogeochemical hotspot for the attenuation of nitrogen within streams, thereby complementing efforts to prevent aquatic nitrogen pollution in the first place. However, HZ in urban and agricultural streams are often degraded by scouring and colmation, which limit their potential to improve stream water quality at the reach scale. A recent effort to mitigate nitrogen pollution in the Chesapeake Bay region provides denitrification credits for hyporheic restoration projects. Unfortunately, many of the featured hyporheic zone best management practices (BMP) (e.g., weirs, cross-vanes) tend to create only localized, aerobic hyporheic flows that are not optimal for the anaerobic denitrification reaction. In short, practitioners lack an adaptable BMP that can both 1) increase hyporheic exchange, and 2) tailor HZ residence times to match reactions of interest. Here we present new performance data for an HZ engineering technique called Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low-permeability sediments to drive efficient hyporheic exchange and control residence times, along with reactive geomedia to increase reaction rates within HZ sediments. This research utilized two artificial stream flumes: One flume served as an all-sand control condition, the other featured BEST modules at 1m spacing with a mixture of 70/30 sand/woodchips (v/v). Two different BEST media were tested: a coarse sand module with K 0.5 cm/s, and a fine sand module with K 0.15 cm/s. The flume with coarse sand BEST modules created aerobic HZ conditions and demonstrated rapid nitrification of ammonia at rates significantly higher than the control. However, denitrification was much slower and not significantly different between the two streams. In contrast, the fine sand

  20. Nitrogen Removal from Milking Center Wastewater via Simultaneous Nitrification and Denitrification Using a Biofilm Filtration Reactor

    Directory of Open Access Journals (Sweden)

    Seung-Gun Won

    2015-06-01

    Full Text Available Milking center wastewater (MCW has a relatively low ratio of carbon to nitrogen (C/N ratio, which should be separately managed from livestock manure due to the negative impacts of manure nutrients and harmful effects on down-stream in the livestock manure process with respect to the microbial growth. Simultaneous nitrification and denitrification (SND is linked to inhibition of the second nitrification and reduces around 40% of the carbonaceous energy available for denitrification. Thus, this study was conducted to find the optimal operational conditions for the treatment of MCW using an attached-growth biofilm reactor; i.e., nitrogen loading rate (NLR of 0.14, 0.28, 0.43, and 0.58 kg m−3 d−1 and aeration rate of 0.06, 0.12, and 0.24 m3 h−1 were evaluated and the comparison of air-diffuser position between one-third and bottom of the reactor was conducted. Four sand packed-bed reactors with the effective volume of 2.5 L were prepared and initially an air-diffuser was placed at one third from the bottom of the reactor. After the adaptation period of 2 weeks, SND was observed at all four reactors and the optimal NLR of 0.45 kg m−3 d−1 was found as a threshold value to obtain higher nitrogen removal efficiency. Dissolved oxygen (DO as one of key operational conditions was measured during the experiment and the reactor with an aeration rate of 0.12 m3 h−1 showed the best performance of NH4-N removal and the higher total nitrogen removal efficiency through SND with appropriate DO level of ~0.5 mg DO L−1. The air-diffuser position at one third from the bottom of the reactor resulted in better nitrogen removal than at the bottom position. Consequently, nitrogen in MCW with a low C/N ratio of 2.15 was successfully removed without the addition of external carbon sources.

  1. Nitrification and nitrogen mineralization in agricultural soils contaminated by copper mining activities in Central Chile

    OpenAIRE

    Moya, Héctor; Verdejo, José; Yáñez, Carolina; Álvaro, Juan E.; Sauvé, Sébastien; Neaman, Alexander

    2017-01-01

    Microbiological bioassays of nitrification and nitrogen mineralization have been used for evaluation of soil quality on metal-contaminated soils. We evaluated the effectiveness of nitrification and nitrogen mineralization bioassays as quality indicators of soil degradation caused by metal contamination. We performed standard tests based on protocols of ISO 14238 (2012) and ISO 15685 (2012) on 90 soil samples collected from agricultural areas in central Chile that were historically contaminate...

  2. Nitrification inhibitors mitigated reactive gaseous nitrogen intensity in intensive vegetable soils from China.

    Science.gov (United States)

    Fan, Changhua; Li, Bo; Xiong, Zhengqin

    2018-01-15

    Nitrification inhibitors, a promising tool for reducing nitrous oxide (N 2 O) losses and promoting nitrogen use efficiency by slowing nitrification, have gained extensive attention worldwide. However, there have been few attempts to explore the broad responses of multiple reactive gaseous nitrogen emissions of N 2 O, nitric oxide (NO) and ammonia (NH 3 ) and vegetable yield to nitrification inhibitor applications across intensive vegetable soils in China. A greenhouse pot experiment with five consecutive vegetable crops was performed to assess the efficacies of two nitrification inhibitors, namely, nitrapyrin and dicyandiamide on reactive gaseous nitrogen emissions, vegetable yield and reactive gaseous nitrogen intensity in four typical vegetable soils representing the intensive vegetable cropping systems across mainland China: an Acrisol from Hunan Province, an Anthrosol from Shanxi Province, a Cambisol from Shandong Province and a Phaeozem from Heilongjiang Province. The results showed soil type had significant influences on reactive gaseous nitrogen intensity, with reactive gaseous nitrogen emissions and yield mainly driven by soil factors: pH, nitrate, C:N ratio, cation exchange capacity and microbial biomass carbon. The highest reactive gaseous nitrogen emissions and reactive gaseous nitrogen intensity were in Acrisol while the highest vegetable yield occurred in Phaeozem. Nitrification inhibitor applications decreased N 2 O and NO emissions by 1.8-61.0% and 0.8-79.5%, respectively, but promoted NH 3 volatilization by 3.2-44.6% across all soils. Furthermore, significant positive correlations were observed between inhibited N 2 O+NO and stimulated NH 3 emissions with nitrification inhibitor additions across all soils, indicating that reduced nitrification posed the threat of NH 3 losses. Additionally, reactive gaseous nitrogen intensity was significantly reduced in the Anthrosol and Cambisol due to the reduced reactive gaseous nitrogen emissions and increased

  3. The effect of temperature on the efficiency of industrial wastewater nitrification and its (genotoxicity

    Directory of Open Access Journals (Sweden)

    Gnida Anna

    2016-03-01

    Full Text Available The paper deals with the problem of the determination of the effects of temperature on the efficiency of the nitrification process of industrial wastewater, as well as its toxicity to the test organisms. The study on nitrification efficiency was performed using wastewater from one of Polish chemical factories. The chemical factory produces nitrogen fertilizers and various chemicals. The investigated wastewater was taken from the influent to the industrial mechanical-biological wastewater treatment plant (WWTP. The WWTP guaranteed high removal efficiency of organic compounds defined as chemical oxygen demand (COD but periodical failure of nitrification performance was noted in last years of the WWTP operation. The research aim was to establish the cause of recurring failures of nitrification process in the above mentioned WWTP. The tested wastewater was not acutely toxic to activated sludge microorganisms. However, the wastewater was genotoxic to activated sludge microorganisms and the genotoxicity was greater in winter than in spring time. Analysis of almost 3 years’ period of the WWTP operation data and laboratory batch tests showed that activated sludge from the WWTP under study is very sensitive to temperature changes and the nitrification efficiency collapses rapidly under 16°C. Additionally, it was calculated that in order to provide the stable nitrification, in winter period the sludge age (SRT in the WWTP should be higher than 35 days.

  4. The herbicide Glyphosate affects nitrification in the Elbe estuary, Germany

    Science.gov (United States)

    Sanders, Tina; Lassen, Stephan

    2015-04-01

    The Elbe River is one of the biggest European rivers discharging into the North Sea. It also transports high amounts of nutrients and pollutants like pesticides. Important source regions of both nutrients and pollutants are located within the river catchment, which is dominated by agricultural land-use. From these agricultural soils, pesticides can be carried via the river and estuary into the North Sea. Glyphosate (N-(phosphonomethyl) glycine) is the most commonly used herbicide worldwide and mainly used to regulate unwanted plant growth and for the expedition of crop ripening. In Germany, ~ 6000 tons of glyphosate are applied yearly in agriculture and private use. Glyphosate is degradable by microorganisms and has a half-life in water of 35 to 60 days. This herbicide specifically inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), an enzyme that catalyzes the biosynthesis of essential aromatic amino acids in plants, fungi, and bacteria. Nitrifying bacteria, which play an important role in the internal nitrogen cycling in the Elbe estuary, also possess this enzyme. The aim of our study was to quantify the concentration of glyphosate in water and sediment samples of the Elbe to get an overview about relevant environmental levels and to assess the impact of glyphosate on inhibition of nitrifying activities. To quantify the effect of glyphosate on nitrification activity, natural samples as well as pure cultures of Nitrosomonas europea (strain Nm50) were incubated with different concentrations of glyphosate over a period of some weeks. The nitrifying activity was determined according to changes of the nitrite and nitrate concentration as well as the cell number. Glyphosate was detectable in water and sediment samples in the Elbe estuary with up to 5 ppb mainly in the Port of Hamburg region. In both incubation experiments an inhibiting effect of glyphosate on nitrification could be shown. The incubated natural water sample was affected by a glyphosate

  5. Fact and Fiction of Nitrous Oxide Production By Nitrification

    Science.gov (United States)

    Stein, L. Y.; Kozlowski, J.; Stieglmeier, M.; Klotz, M. G.; Schleper, C.

    2014-12-01

    An accepted dogma in nitrification research is that ammonia-oxidizing bacteria (AOB) produce a modicum of nitrous oxide (N2O) during nitritation via incomplete oxidation of hydroxylamine, and substantially more at low oxygen concentrations via nitrifier denitrification.The nitrifier denitrification pathway involves the reduction of nitrite to N2O via nitric oxide and was thought to require activities of a copper-containing nitrite reductase (NirK) and nitric oxide reductase (NorB); inventory encoded in most, but not all AOB genome sequences. The discovery of nirK genes in ammonia-oxidizing Thaumarchaeota (AOA) resulted in a slew of publications stating that AOA must also perform nitrifier denitrification and, due to their high abundance, must control the majority of nitrification-linked N2O emissions. Prior to a publication by Stieglmeier et al. (2014), which definitively showed a lack of nitrifier denitrification by two axenic AOA cultures, other researchers relied on enrichment cultures, negative data, and heavy inferencing without direct demonstration of either a functional pathway or involvement of specific genes or enzymes. AOA genomes lack recognizable nitric oxide reductases and thermophilic AOA also lack nirK genes. Physiological and microrespirometry experiments with axenic AOB and AOA cultures allowed us to demonstrate that: 1) AOB produce N2O via nitrifier denitrification even though some lack annotated nirK and/or norB genes; 2) nitrifier denitrification by AOB is reliant on nitric oxide but ammonia oxidation is not; 3) ammonia oxidation by AOA is reliant on production of nitric oxide; 4) AOA are incapable of generating N2O via nitrifier denitrification; 5) N2O production by AOA is from chemical interactions between NO and media components, most likely not by enzyme activity. Our results reveal operation of different N oxide transformation pathways in AOB and AOA governed by different environmental controls and involving different mechanisms of N2O

  6. Net Gain: A New Method for Preventing Malaria Deaths | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    A finely spun net could prevent as many as one-third of all child deaths in Africa, reports IDRC's new publication, Net Gain. Studies conducted in Gambia, Ghana, and Kenya show that the insecticide-treated mosquito net reduced the mortality rate of children under 5 years of age by up to 63 percent. Net Gain reviews and ...

  7. Nitrogen removal from landfill leachate via ex situ nitrification and sequential in situ denitrification

    International Nuclear Information System (INIS)

    Zhong Qi; Li Daping; Tao Yong; Wang Xiaomei; He Xiaohong; Zhang Jie; Zhang Jinlian; Guo Weiqiang; Wang Lan

    2009-01-01

    Ex situ nitrification and sequential in situ denitrification represents a novel approach to nitrogen management at landfills. Simultaneous ammonia and organics removal was achieved in a continuous stirred tank reactor (CSTR). The results showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65 g N l -1 d -1 and 3.84 g COD l -1 d -1 , respectively. The ammonia and chemical oxygen demand (COD) removal was over 99% and 57%, respectively. In the run of the CSTR, free ammonia (FA) inhibition and low dissolved oxygen (DO) were found to be key factors affecting nitrite accumulation. In situ denitrification was studied in a municipal solid waste (MSW) column by recalculating nitrified leachate from CSTR. The decomposition of MSW was accelerated by the recirculation of nitrified leachate. Complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON loading of 28.6 g N t -1 TS d -1 and denitrification was the main reaction responsible. Additionally, methanogenesis inhibition was observed while TON loading was over 11.4 g N t -1 TS d -1 and the inhibition was enhanced with the increase of TON loading

  8. Start-up and bacterial community compositions of partial nitrification in moving bed biofilm reactor.

    Science.gov (United States)

    Liu, Tao; Mao, Yan-Jun; Shi, Yan-Ping; Quan, Xie

    2017-03-01

    Partial nitrification (PN) has been considered as one of the promising processes for pretreatment of ammonium-rich wastewater. In this study, a kind of novel carriers with enhanced hydrophilicity and electrophilicity was implemented in a moving bed biofilm reactor (MBBR) to start up PN process. Results indicated that biofilm formation rate was higher on modified carriers. In comparison with the reactor filled with traditional carriers (start-up period of 21 days), it took only 14 days to start up PN successfully with ammonia removal efficiency and nitrite accumulation rate of 90 and 91%, respectively, in the reactor filled with modified carriers. Evident changes of spatial distributions and community structures had been detected during the start-up. Free-floating cells existed in planktonic sludge, while these microorganisms trended to form flocs in the biofilm. High-throughput pyrosequencing results indicated that Nitrosomonas was the predominant ammonia-oxidizing bacterium (AOB) in the PN system, while Comamonas might also play a vital role for nitrogen oxidation. Additionally, some other bacteria such as Ferruginibacter, Ottowia, Saprospiraceae, and Rhizobacter were selected to establish stable footholds. This study would be potentially significant for better understanding the microbial features and developing efficient strategies accordingly for MBBR-based PN operation.

  9. Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR)

    International Nuclear Information System (INIS)

    Rahimi, Yousef; Torabian, Ali; Mehrdadi, Naser; Shahmoradi, Behzad

    2011-01-01

    Research highlights: → Sludge production in FSBR reactor is 20-30% less than SBR reactor. → FSBR reactor showed more nutrient removal rate than SBR reactor. → FSBR reactor showed less VSS/TSS ratio than SBR reactor. - Abstract: Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y obs ) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).

  10. Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR)

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Yousef, E-mail: you.rahimi@gmail.com [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Torabian, Ali, E-mail: atorabi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Mehrdadi, Naser, E-mail: mehrdadi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Shahmoradi, Behzad, E-mail: bshahmorady@gmail.com [Department of Environmental Science, University of Mysore, MGM-06 Mysore (India)

    2011-01-30

    Research highlights: {yields} Sludge production in FSBR reactor is 20-30% less than SBR reactor. {yields} FSBR reactor showed more nutrient removal rate than SBR reactor. {yields} FSBR reactor showed less VSS/TSS ratio than SBR reactor. - Abstract: Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y{sub obs}) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).

  11. Planning of nets

    International Nuclear Information System (INIS)

    Carberry, M

    1996-01-01

    The paper is about the planning of nets in areas of low density like it is the case of the rural areas. The author includes economic and technological aspects, planning of nets, demands and management among others

  12. Annotating Coloured Petri Nets

    DEFF Research Database (Denmark)

    Lindstrøm, Bo; Wells, Lisa Marie

    2002-01-01

    Coloured Petri nets (CP-nets) can be used for several fundamentally different purposes like functional analysis, performance analysis, and visualisation. To be able to use the corresponding tool extensions and libraries it is sometimes necessary to include extra auxiliary information in the CP......-net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... of the same basic CP-net. One solution to this problem is that the auxiliary information is not integrated into colour sets and arc inscriptions of a CP-net, but is kept separately. This makes it easy to disable this auxiliary information if a CP-net is to be used for another purpose. This paper proposes...

  13. Tracking and quantification of nitrifying bacteria in biofilm and mixed liquor of a partial nitrification MBBR pilot plant using fluorescence in situ hybridization

    International Nuclear Information System (INIS)

    Abzazou, Tarik; Araujo, Rosa M.; Auset, María; Salvadó, Humbert

    2016-01-01

    A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification process for pre-treatment of ammonium-rich liquors (676 ± 195 mg L"−"1), and studied for 479 days under variations in hydraulic retention time. The main purpose of this work, was the study of dynamics abundance of total bacteria and single-cells nitrifying bacteria belonging to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in biofilms and mixed liquor of the plant. The microbial monitoring was successfully achieved using fluorescence in situ hybridization combined with flocs disaggregation protocol as a useful microbial monitoring tool. A partial nitrification process with a N-NH_4"+ removal rate of about 38.6 ± 14.8% was successfully achieved at 211 days after start-up, with a clear dominance of AOB, which accounted for 11.3 ± 17.0% of total bacterial cells compared with only 2.1 ± 4.0% of NOB. The effluent obtained was subsequently supplied to an Anammox reactor for complete ammonium treatment. - Highlights: • Partial nitrification process in a MBBR fed with ammonium-rich liquor was achieved. • The operational key parameters were the HRT and temperature. • DAPI and FISH were useful to monitoring microbial composition of MBBR pilot plant. • The AOB were the dominant nitrifying bacteria, presenting 11.3% of total bacteria. • A significant correlation (R = 0.68) between AOB and ammonia removal was found.

  14. Depth investigation of rapid sand filters for drinking water production reveals strong stratification in nitrification biokinetic behavior

    DEFF Research Database (Denmark)

    Tatari, Karolina; Smets, Barth F.; Albrechtsen, Hans-Jørgen

    2016-01-01

    The biokinetic behavior of NH4 + removal was investigated at different depths of a rapid sand filter treating groundwater for drinking water preparation. Filter materials from the top, middle and bottom layers of a full-scale filter were exposed to various controlled NH4 + loadings in a continuous......-flow lab-scale assay. NH4 + removal capacity, estimated from short term loading up-shifts, was at least 10 times higher in the top than in the middle and bottom filter layers, consistent with the stratification of Ammonium Oxidizing Bacteria (AOB). AOB density increased consistently with the NH4 + removal...... rate, indicating their primarily role in nitrification under the imposed experimental conditions. The maximum AOB cell specific NH4 + removal rate observed at the bottom was at least 3 times lower compared to the top and middle layers. Additionally, a significant up-shift capacity (4.6 and 3.5 times...

  15. A paradigm shift towards low-nitrifying production systems: the role of biological nitrification inhibition (BNI)

    Science.gov (United States)

    Subbarao, G. V.; Sahrawat, K. L.; Nakahara, K.; Rao, I. M.; Ishitani, M.; Hash, C. T.; Kishii, M.; Bonnett, D. G.; Berry, W. L.; Lata, J. C.

    2013-01-01

    Background Agriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems. Scope In this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4+)-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and

  16. A paradigm shift towards low-nitrifying production systems: the role of biological nitrification inhibition (BNI).

    Science.gov (United States)

    Subbarao, G V; Sahrawat, K L; Nakahara, K; Rao, I M; Ishitani, M; Hash, C T; Kishii, M; Bonnett, D G; Berry, W L; Lata, J C

    2013-07-01

    Agriculture is the single largest geo-engineering initiative that humans have initiated on planet Earth, largely through the introduction of unprecedented amounts of reactive nitrogen (N) into ecosystems. A major portion of this reactive N applied as fertilizer leaks into the environment in massive amounts, with cascading negative effects on ecosystem health and function. Natural ecosystems utilize many of the multiple pathways in the N cycle to regulate N flow. In contrast, the massive amounts of N currently applied to agricultural systems cycle primarily through the nitrification pathway, a single inefficient route that channels much of this reactive N into the environment. This is largely due to the rapid nitrifying soil environment of present-day agricultural systems. In this Viewpoint paper, the importance of regulating nitrification as a strategy to minimize N leakage and to improve N-use efficiency (NUE) in agricultural systems is highlighted. The ability to suppress soil nitrification by the release of nitrification inhibitors from plant roots is termed 'biological nitrification inhibition' (BNI), an active plant-mediated natural function that can limit the amount of N cycling via the nitrification pathway. The development of a bioassay using luminescent Nitrosomonas to quantify nitrification inhibitory activity from roots has facilitated the characterization of BNI function. Release of BNIs from roots is a tightly regulated physiological process, with extensive genetic variability found in selected crops and pasture grasses. Here, the current status of understanding of the BNI function is reviewed using Brachiaria forage grasses, wheat and sorghum to illustrate how BNI function can be utilized for achieving low-nitrifying agricultural systems. A fundamental shift towards ammonium (NH4(+))-dominated agricultural systems could be achieved by using crops and pastures with high BNI capacities. When viewed from an agricultural and environmental perspective, the

  17. Influence of soil humus content on the effect of nitrification inhibitors applied with liquid manure and slurry

    International Nuclear Information System (INIS)

    Peschke, H.

    1986-01-01

    The effect of the nitrification inhibitors nitrapyrin (NP), 1-carbomoyl-3-(5)-methyl-pyrazole (CMP) and dicyandiamide (DCD) applied with 15 N-labelled liquid manure and slurry was investigated in incubation experiments with ten soils of different humus content, including soils from three selected plots of both the Thyrow soil fertility experiment and the Lauchstaedt static experiment. A significant negative relation was found for liquid manure between the nitrification delay of the three inhibitors in relation to the C/sub t/ content, nitrification capacity, and nitrification turnover of the soil. This relationship was found in the slurry variants only when DCD was applied. (author)

  18. Effects of a catheter-associated urinary tract infection prevention campaign on infection rate, catheter utilization, and health care workers' perspective at a community safety net hospital.

    Science.gov (United States)

    Gray, Dorinne; Nussle, Richard; Cruz, Abner; Kane, Gail; Toomey, Michael; Bay, Curtis; Ostovar, Gholamabbas Amin

    2016-01-01

    Preventing catheter-associated urinary tract infections is in the forefront of health care quality. However, nurse and physician engagement is a common barrier in infection prevention efforts. After implementation of a multidisciplinary catheter-associated urinary tract infection (CAUTI) prevention campaign, we studied the impact of our campaign and showed its association with reducing the CAUTI rate and catheter utilization and the positive effect on health care workers' engagement and perspectives. CAUTI prevention campaigns can lead to lower infection rates and change health care workers' perspective. Copyright © 2016 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  19. Regulation and role of epiphytic nitrification and denitrification in macrophyte-dominated systems

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Peder G.

    2000-02-01

    This thesis examines mechanisms regulating bacterial nitrification and denitrification in attached microbial communities on surfaces of aquatic macrophytes. It also evaluates the role of epiphytic nitrification and denitrification for the nitrogen turnover in macrophyte-dominated nutrient-rich freshwater. Epiphytic nitrification is promoted in light and epiphytic denitrification occurs mainly in dark, because the metabolic activity of the aquatic macrophyte and its epiphytes induce in light high and in dark low oxygen concentrations in epiphytic communities. Epiphytic nitrification and denitrification are also affected by the physical and chemical characteristics of the aquatic macrophyte. The spatial distribution of nitrification in emergent macrophyte wetlands is related to the species composition of the emergent vegetation, possibly because of a macrophyte species-related release of organic nitrification inhibitors. Contrasting to nitrifying bacteria, which are lithotrophic, denitrifying bacteria use organic substances as an energy source and are therefore stimulated by the release of organic matter from aquatic macrophytes. Epiphytic communities support more denitrification in nutrient-rich than in nutrient-poor environments. In lakes and ponds, epiphytic denitrification is higher at sheltered locations than at locations exposed to wind-induced water movements or currents. In flowing water, epiphytic denitrification occurs mainly at low oxygen concentrations in the surrounding water. However, because aquatic macrophytes impede water flow and induce low oxygen concentrations in dark, epiphytic denitrification can be present within dense vegetation despite of high oxygen concentrations in the surrounding water. Epiphytic nitrification is almost unaffected by flow conditions, and can occur both in light and in dark. In shallow-water systems such as treatment wetlands, aquatic macrophytes often provide most of the accessible surface area for attached nitrifying and

  20. Potential Nitrification and Nitrogen Mineral of Soil in Coffee Agroforestry System with Various Shading Trees

    Directory of Open Access Journals (Sweden)

    Purwanto .

    2007-05-01

    Full Text Available The role of shading trees in coffee farms has been well understood to establish suitable condition for the growth of coffee trees, on the other hand their role in nitrogen cycle in coffee farming is not yet well understood. The objectives of this study are to investigate the influence of various legume shading trees on the concentration of soil mineral N (N-NH4 + and N-NO3-, potential nitrification and to study the controlling factors of nitrification under field conditions. This field explorative research was carried out in Sumberjaya, West Lampung. Twelve observation plots covered four land use systems (LUS, i.e. 1 Coffee agroforestry with Gliricidiasepium as shade trees; 2 Coffee agroforestry with Gliricidiaas shade trees and Arachis pintoias cover crops; 3Coffee agroforestry with Paraserianthes falcataria as shade trees; and 4 Mixed/multistrata coffee agroforestry with Gliricidiaand other fruit crops as shade trees. Measurements of soil mineral-N concentration were carried out every three weeks for three months. Results showed that shade tree species in coffee agroforestry significantly affected concentrations of soil NH4 +, NO3- and potential nitrification. Mixed coffee agroforestry had the highest NH4+/N-mineral ratio (7.16% and the lowest potential nitrification (0.13 mg NO2-kg-1 hour -1 compared to other coffee agroforestry systems using single species of leguminous shade trees. Ratio of NH4 + /N-mineral increased 0.8—21% while potential nitrification decreased 55—79% in mixed coffee agroforestry compared to coffee agroforestry with Gliricidia or P. falcatariaas shade trees. Coffee agroforestry with P. falcatariaas shade trees had potential nitrification 53% lower and ratio of NH4 + /N-mineral concentration 20% higher than that with Gliricidia. Coffee agroforestry with P. falcataria as shade trees also had organic C content 17% higher, total N 40% higher, available P 112% higher than that with Gliricidia. The presence of A. pintoiin

  1. Estimating the net effect of progesterone elevation on the day of hCG on live birth rates after IVF: a cohort analysis of 3296 IVF cycles.

    Science.gov (United States)

    Venetis, Christos A; Kolibianakis, Efstratios M; Bosdou, Julia K; Lainas, George T; Sfontouris, Ioannis A; Tarlatzis, Basil C; Lainas, Tryfon G

    2015-03-01

    What is the proper way of assessing the effect of progesterone elevation (PE) on the day of hCG on live birth in women undergoing fresh embryo transfer after in vitro fertilization (IVF) using GnRH analogues and gonadotrophins? This study indicates that a multivariable approach, where the effect of the most important confounders is controlled for, can lead to markedly different results regarding the association between PE on the day of hCG and live birth rates after IVF when compared with the bivariate analysis that has been typically used in the relevant literature up to date. PE on the day of hCG is associated with decreased pregnancy rates in fresh IVF cycles. Evidence for this comes from observational studies that mostly failed to control for potential confounders. This is a retrospective analysis of a cohort of fresh IVF/intracytoplasmic sperm injection cycles (n = 3296) performed in a single IVF centre during the period 2001-2013. Patients in whom ovarian stimulation was performed with gonadotrophins and GnRH analogues. Natural cycles and cycles where stimulation involved the administration of clomiphene were excluded. In order to reflect routine clinical practice, no other exclusion criteria were imposed on this dataset. The primary outcome measure for this study was live birth defined as the delivery of a live infant after 24 weeks of gestation. We compared the association between PE on the day of hCG (defined as P > 1.5 ng/ml) and live birth rates calculated by simple bivariate analyses with that derived from multivariable logistic regression. The multivariable analysis controlled for female age, number of oocytes retrieved, number of embryos transferred, developmental stage of embryos at transfer (cleavage versus blastocyst), whether at least one good-quality embryo was transferred, the woman's body mass index, the total dose of FSH administered during ovarian stimulation and the type of GnRH analogues used (agonists versus antagonists) during ovarian

  2. Nitrification of industrial and domestic saline wastewaters in moving bed biofilm reactor and sequencing batch reactor

    International Nuclear Information System (INIS)

    Bassin, Joao P.; Dezotti, Marcia; Sant'Anna, Geraldo L.

    2011-01-01

    Nitrification of saline wastewaters was investigated in bench-scale moving-bed biofilm reactors (MBBR). Wastewater from a chemical industry and domestic sewage, both treated by the activated sludge process, were fed to moving-bed reactors. The industrial wastewater contained 8000 mg Cl - /L and the salinity of the treated sewage was gradually increased until that level. Residual substances present in the treated industrial wastewater had a strong inhibitory effect on the nitrification process. Assays to determine inhibitory effects were performed with the industrial wastewater, which was submitted to ozonation and carbon adsorption pretreatments. The latter treatment was effective for dissolved organic carbon (DOC) removal and improved nitrification efficiency. Nitrification percentage of the treated domestic sewage was higher than 90% for all tested chloride concentrations up to 8000 mg/L. Results obtained in a sequencing batch reactor (SBR) were consistent with those attained in the MBBR systems, allowing tertiary nitrification and providing adequate conditions for adaptation of nitrifying microorganisms even under stressing and inhibitory conditions.

  3. Expected Net Present Value, Expected Net Future Value, and the Ramsey Rule

    OpenAIRE

    Gollier, Christian

    2010-01-01

    Weitzman (1998) showed that when future interest rates are uncertain, using the expected net present value implies a term structure of discount rates that is decreasing to the smallest possible interest rate. On the contrary, using the expected net future value criteria implies an increasing term structure of discount rates up to the largest possible interest rate. We reconcile the two approaches by introducing risk aversion and utility maximization. We show that if the aggregate consumption ...

  4. Nitrification of archaeal ammonia oxidizers in a high- temperature hot spring

    Science.gov (United States)

    Chen, Shun; Peng, Xiaotong; Xu, Hengchao; Ta, Kaiwen

    2016-04-01

    The oxidation of ammonia by microbes has been shown to occur in diverse natural environments. However, the link of in situ nitrification activity to taxonomic identities of ammonia oxidizers in high-temperature environments remains poorly understood. Here, we studied in situ ammonia oxidation rates and the diversity of ammonia-oxidizing Archaea (AOA) in surface and bottom sediments at 77 °C in the Gongxiaoshe hot spring, Tengchong, Yunnan, China. The in situ ammonia oxidation rates measured by the 15N-NO3- pool dilution technique in the surface and bottom sediments were 4.80 and 5.30 nmol N g-1 h-1, respectively. Real-time quantitative polymerase chain reaction (qPCR) indicated that the archaeal 16S rRNA genes and amoA genes were present in the range of 0.128 to 1.96 × 108 and 2.75 to 9.80 × 105 gene copies g-1 sediment, respectively, while bacterial amoA was not detected. Phylogenetic analysis of 16S rRNA genes showed high sequence similarity to thermophilic Candidatus Nitrosocaldus yellowstonii, which represented the most abundant operational taxonomic units (OTU) in both surface and bottom sediments. The archaeal predominance was further supported by fluorescence in situ hybridization (FISH) visualization. The cell-specific rate of ammonia oxidation was estimated to range from 0.410 to 0.790 fmol N archaeal cell-1 h-1, higher than those in the two US Great Basin hot springs. These results suggest the importance of archaeal rather than bacterial ammonia oxidation in driving the nitrogen cycle in terrestrial geothermal environments.

  5. Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial.

    Directory of Open Access Journals (Sweden)

    Judith Prommer

    Full Text Available Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies.

  6. Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial.

    Science.gov (United States)

    Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare

    2014-01-01

    Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies.

  7. Biochar Decelerates Soil Organic Nitrogen Cycling but Stimulates Soil Nitrification in a Temperate Arable Field Trial

    Science.gov (United States)

    Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare

    2014-01-01

    Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50–80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies. PMID:24497947

  8. Using the Triple Labelling Technique to apportion N2O Emissions to Nitrification and Denitrification from different Nitrogen Sources at different Water-Filled-Pore-Spaces

    Science.gov (United States)

    Loick, Nadine; Dixon, Elizabeth R.; Repullo Ruibérriz de Torres, Miguel A.; Ciganda, Veronica; Lopez-Aizpun, Maria A.; Matthews, G. Peter; Müller, Christoph; Cardenas, Laura M.

    2017-04-01

    Nitrous oxide (N2O) is considered to be an important greenhouse gas (GHG) accounting for approximately 6% of the current global warming. The atmospheric N2O concentration has been increasing since the Industrial Revolution, with soils representing its major source, making the understanding of its sources and removal processes very important for the development of mitigation strategies. In soils N gases are mainly produced via nitrification and denitrification. It is assumed that under dry/aerobic conditions nitrification is the dominant N consuming process, while denitrification becomes dominant under wetter conditions promoting anaerobicity. Nitrification and denitrification may occur simultaneously in different microsites of the same soil but there is often uncertainty associated with which process dominates in a particular soil under specific conditions. N2O predominantly derives from incomplete denitrification of nitrate (NO3-). The existence of different pools of NO3- in soils, namely the native soil pool, and the fertiliser-added one, has been suggested through a series of laboratory incubation experiments (Meijide et al., 2010; Bergstermann et al., 2011) using the denitrification incubation system, DENIS (Cardenas et al., 2003), in which soil cores are incubated under an N-free atmosphere, allowing direct measurements of all emitted N gases (NO, N2O and N2) as well as CO2. A third pool, NO3- produced from nitrification of applied NH4+, can also be a source of N2O via denitrification and also from nitrification. In this study labelling of substrate-N with 15N is used to quantify the underlying gross N transformation rates and link them to N-emissions to identify the production and consumption pathways and temporal dynamics of N2O. In three experiments twelve soil cores each were incubated in the DENIS to measure gaseous emissions, while parallel incubations under the same conditions were set up for destructive soil sampling at 7 time points. Using the triple

  9. Quantum net dynamics

    International Nuclear Information System (INIS)

    Finkelstein, D.

    1989-01-01

    The quantum net unifies the basic principles of quantum theory and relativity in a quantum spacetime having no ultraviolet infinities, supporting the Dirac equation, and having the usual vacuum as a quantum condensation. A correspondence principle connects nets to Schwinger sources and further unifies the vertical structure of the theory, so that the functions of the many hierarchic levels of quantum field theory (predicate algebra, set theory, topology,hor-ellipsis, quantum dynamics) are served by one in quantum net dynamics

  10. Using the quantum yields of photosystem II and the rate of net photosynthesis to moniter high irradiance and temperature stress in chrysanthemum (Dendrantherma grandiflora)

    DEFF Research Database (Denmark)

    Janka, Eshetu; Körner, Oliver; Rosenqvist, Eva

    2015-01-01

    and quantum yield of PSII remaining low until the temperature reaches 28 °C and 2) the integration of online measurements to monitor photosynthesis and PSII operating efficiency may be used to optimise dynamic greenhouse control regimes by detecting plant stress caused by extreme microclimatic conditions.......Under a dynamic greenhouse climate control regime, temperature is adjusted to optimise plant physiological responses to prevailing irradiance levels; thus, both temperature and irradiance are used by the plant to maximise the rate of photosynthesis, assuming other factors are not limiting...... irradiance, the maximum Pn and ETR were reached at 24 °C. Increased irradiance decreased the PSII operating efficiency and increased NPQ, while both high irradiance and temperature had a significant effect on the PSII operating efficiency at temperatures >28 °C. Under high irradiance and temperature, changes...

  11. Rapid Start-up and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin E.; Pensinger, Stuart; Pickering, Karen D.; Barta, Daniel; Shull, Sarah A.; Vega, Letticia M.; Christenson, Dylan; Jackson, W. Andrew

    2015-01-01

    Membrane aerated bioreactors (MABR) are attached-growth biological systems used for simultaneous nitrification and denitrification to reclaim water from waste. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal and implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to under two weeks, and that despite low ammonium removal rates, the MABRs are oversized.

  12. Genetic mitigation strategies to tackle agricultural GHG emissions: The case for biological nitrification inhibition technology.

    Science.gov (United States)

    Subbarao, G V; Arango, J; Masahiro, K; Hooper, A M; Yoshihashi, T; Ando, Y; Nakahara, K; Deshpande, S; Ortiz-Monasterio, I; Ishitani, M; Peters, M; Chirinda, N; Wollenberg, L; Lata, J C; Gerard, B; Tobita, S; Rao, I M; Braun, H J; Kommerell, V; Tohme, J; Iwanaga, M

    2017-09-01

    Accelerated soil-nitrifier activity and rapid nitrification are the cause of declining nitrogen-use efficiency (NUE) and enhanced nitrous oxide (N 2 O) emissions from farming. Biological nitrification inhibition (BNI) is the ability of certain plant roots to suppress soil-nitrifier activity, through production and release of nitrification inhibitors. The power of phytochemicals with BNI-function needs to be harnessed to control soil-nitrifier activity and improve nitrogen-cycling in agricultural systems. Transformative biological technologies designed for genetic mitigation are needed, so that BNI-enabled crop-livestock and cropping systems can rein in soil-nitrifier activity, to help reduce greenhouse gas (GHG) emissions and globally make farming nitrogen efficient and less harmful to environment. This will reinforce the adaptation or mitigation impact of other climate-smart agriculture technologies. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Programming NET Web Services

    CERN Document Server

    Ferrara, Alex

    2007-01-01

    Web services are poised to become a key technology for a wide range of Internet-enabled applications, spanning everything from straight B2B systems to mobile devices and proprietary in-house software. While there are several tools and platforms that can be used for building web services, developers are finding a powerful tool in Microsoft's .NET Framework and Visual Studio .NET. Designed from scratch to support the development of web services, the .NET Framework simplifies the process--programmers find that tasks that took an hour using the SOAP Toolkit take just minutes. Programming .NET

  14. Game Coloured Petri Nets

    DEFF Research Database (Denmark)

    Westergaard, Michael

    2006-01-01

    This paper introduces the notion of game coloured Petri nets. This allows the modeler to explicitly model what parts of the model comprise the modeled system and what parts are the environment of the modeled system. We give the formal definition of game coloured Petri nets, a means of reachability...... analysis of this net class, and an application of game coloured Petri nets to automatically generate easy-to-understand visualizations of the model by exploiting the knowledge that some parts of the model are not interesting from a visualization perspective (i.e. they are part of the environment...

  15. Nitrification of an industrial wastewater in a moving-bed biofilm reactor: effect of salt concentration.

    Science.gov (United States)

    Vendramel, Simone; Dezotti, Marcia; Sant'Anna, Geraldo L

    2011-01-01

    Nitrification of wastewaters from chemical industries can pose some challenges due to the presence of inhibitory compounds. Some wastewaters, besides their organic complexity present variable levels of salt concentration. In order to investigate the effect of salt (NaCl) content on the nitrification of a conventional biologically treated industrial wastewater, a bench scale moving-bed biofilm reactor was operated on a sequencing batch mode. The wastewater presenting a chloride content of 0.05 g l(-1) was supplemented with NaCl up to 12 g Cl(-) l(-1). The reactor operation cycle was: filling (5 min), aeration (12 or 24h), settling (5 min) and drawing (5 min). Each experimental run was conducted for 3 to 6 months to address problems related to the inherent wastewater variability and process stabilization. A PLC system assured automatic operation and control of the pertinent process variables. Data obtained from selected batch experiments were adjusted by a kinetic model, which considered ammonia, nitrite and nitrate variations. The average performance results indicated that nitrification efficiency was not influenced by chloride content in the range of 0.05 to 6 g Cl(-) l(-1) and remained around 90%. When the chloride content was 12 g Cl(-) l(-1), a significant drop in the nitrification efficiency was observed, even operating with a reaction period of 24 h. Also, a negative effect of the wastewater organic matter content on nitrification efficiency was observed, which was probably caused by growth of heterotrophs in detriment of autotrophs and nitrification inhibition by residual chemicals.

  16. Roughness and temperature effects on the filter media of a trickling filter for nitrification.

    Science.gov (United States)

    Kishimoto, Naoyuki; Ohara, Tetsuya; Hinobayashi, Jouji; Hashimoto, Tsutomu

    2014-01-01

    The performance of trickling filters using two types of plastic media with the same material, the same shape and different roughness was evaluated during a temperature-decreasing period to understand the roughness and temperature effects on the filter media. Real restaurant wastewater was used for the experiments. The chemical oxygen demand (COD) removal and nitrification performance of plastic media with a rough surface (LT-15) was superior to that with a smooth surface (KT-15). Because the biomass of microorganisms attached on the LT-15 was twice that attached on the KT-15, the larger biomass attached on the LT-15 was thought to be responsible for the higher performance. During the operation, the COD loading and water temperature varied in the range from 0.37 to 1.9 kg m(-3) d(-1) and 17.0--10.0 degrees C, respectively. However, the COD removal performance was not dependent on the COD loading or water temperature. On the contrary, the COD loading and the water temperature influenced the nitrification performance. Although a nitrification efficiency of 100% was recorded at a COD loading of 0.37 kg m(-3) d(-1), it deteriorated to 17-28% at higher COD loading. Moreover, a decline in the water temperature decreased the nitrification performance. The temperature-activity coefficient for nitrification was estimated to be 1.096. Based on this value, it was inferred that the COD loading should be set at less than 0.20 kg m(-3) d(-1) for the complete nitrification of the restaurant wastewater in winter, when the water temperature usually drops to around 10 degrees C.

  17. Effective mitigation of nitrate leaching and nitrous oxide emissions in intensive vegetable production systems using a nitrification inhibitor, dicyandiamide

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Min; Sun, Xuecheng; Hu, Chengxiao; Tan, Qiling; Zhao, Changsheng [Huazhong Agricultural Univ., Wuhan (China). Key Lab. of Subtropical Agricultural Resources and Environment; Di, Hong J. [Lincoln Univ., Christchurch (New Zealand). Center for Soil and Environment Research

    2011-07-15

    Vegetable production is one of the most intensive agricultural systems with high rates of nitrogen (N) fertilizer use and irrigation, conditions conducive for nitrate (NO{sub 3}{sup -}) leaching, and nitrous oxide (N{sub 2}O) emissions. The objective of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO{sub 3}{sup -} leaching and N{sub 2}O emissions in vegetable production systems. Twenty-four undisturbed soil monolith lysimeters (610 mm in diameter; 700 mm in depth; surface area, 0.29 m{sup 2}) with two different soils, Huangzongrang (alfisol) and Chaotu (fluvisols), were collected and installed in a field lysimeter facility in Central China under irrigated vegetable production conditions. Urea fertilizer was applied at 650 kg N ha{sup -1}, and DCD was applied at 10 kg ha{sup -1} to the lysimeters planted with three kinds of vegetables (capsicum, Capsicum annuum L.; amaranth, Amaranthus mangostanus L.; radish, Raphanus sativus L.). The results showed that DCD reduced NO3- leaching by 58.5% and 36.2% and N{sub 2}O emissions factor by 83.8% and 72.7% in the two soils. The average NO{sub 3}{sup -}-N concentration in the drainage water was decreased from 4.9 mg NL{sup -1} to 2.3 mg NL{sup -1} and from 4.4 mg NL{sup -1} to 3.3 mg NL{sup -1}, in the Huangzongrang and Chaotu soils, respectively. In addition to the environmental benefits, the use of DCD also increased the yields of capsicum and radish in alfisol soil significantly (P < 0.01); only the amaranth yield in fluvisol soil was declined (P < 0.01), and the other vegetables yields were not affected. Total N concentrations of the three vegetables were increased significantly (P < 0.01) with the application of DCD with urea compared with urea alone. These results showed that the nitrification inhibitor DCD has the potential to significantly reduce NO{sub 3}{sup -} leaching and N{sub 2}O emissions and to make vegetable farming more environmentally

  18. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1991-01-01

    This paper describes how Coloured Petri Nets (CP-nets) have been developed — from being a promising theoretical model to being a full-fledged language for the design, specification, simulation, validation and implementation of large software systems (and other systems in which human beings and...

  19. Net zero water

    CSIR Research Space (South Africa)

    Lindeque, M

    2013-01-01

    Full Text Available the national grid. The unfortunate situation with water is that there is no replacement technology for water. Water can be supplied from many different sources. A net zero energy development will move closer to a net zero water development by reducing...

  20. Construction of monophase nets

    International Nuclear Information System (INIS)

    Suarez A, Jose Antonio

    1996-01-01

    The paper refers to the use of monophase loads in commercial residential urbanizations and in small industries, for this reason it is considered unnecessary the construction of three-phase nets. The author makes a historical recount of these nets in Bogota, his capacities, uses and energy savings

  1. Presence of animal feeding operations and community socioeconomic factors impact salmonellosis incidence rates: An ecological analysis using data from the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2010.

    Science.gov (United States)

    Shaw, Kristi S; Cruz-Cano, Raul; Jiang, Chengsheng; Malayil, Leena; Blythe, David; Ryan, Patricia; Sapkota, Amy R

    2016-10-01

    Nontyphoidal Salmonella spp. are a leading cause of foodborne illness. Risk factors for salmonellosis include the consumption of contaminated chicken, eggs, pork and beef. Agricultural, environmental and socioeconomic factors also have been associated with rates of Salmonella infection. However, to our knowledge, these factors have not been modeled together at the community-level to improve our understanding of whether rates of salmonellosis are variable across communities defined by differing factors. To address this knowledge gap, we obtained data on culture-confirmed Salmonella Typhimurium, S. Enteritidis, S. Newport and S. Javiana cases (2004-2010; n=14,297) from the Foodborne Diseases Active Surveillance Network (FoodNet), and socioeconomic, environmental and agricultural data from the 2010 Census of Population and Housing, the 2011 American Community Survey, and the 2007 U.S. Census of Agriculture. We linked data by zip code and derived incidence rate ratios using negative binomial regressions. Multiple community-level factors were associated with salmonellosis rates; however, our findings varied by state. For example, in Georgia (Incidence Rate Ratio (IRR)=1.01; 95% Confidence Interval (CI)=1.005-1.015) Maryland (IRR=1.01; 95% CI=1.003-1.015) and Tennessee (IRR=1.01; 95% CI=1.002-1.012), zip codes characterized by greater rurality had higher rates of S. Newport infections. The presence of broiler chicken operations, dairy operations and cattle operations in a zip code also was associated with significantly higher rates of infection with at least one serotype in states that are leading producers of these animal products. For instance, in Georgia and Tennessee, rates of S. Enteritidis infection were 48% (IRR=1.48; 95% CI=1.12-1.95) and 46% (IRR=1.46; 95% CI=1.17-1.81) higher in zip codes with broiler chicken operations compared to those without these operations. In Maryland, New Mexico and Tennessee, higher poverty levels in zip codes were associated with

  2. Fusion through the NET

    International Nuclear Information System (INIS)

    Spears, B.

    1987-01-01

    The paper concerns the next generation of fusion machines which are intended to demonstrate the technical viability of fusion. In Europe, the device that will follow on from JET is known as NET - the Next European Torus. If the design programme for NET proceeds, Europe could start to build the machine in 1994. The present JET programme hopes to achieve breakeven in the early 1990's. NET hopes to reach ignition in the next century, and so lay the foundation for a demonstration reactor. A description is given of the technical specifications of the components of NET, including: the first wall, the divertors to protect the wall, the array of magnets that provide the fields containing the plasma, the superconducting magnets, and the shield of the machine. NET's research programme is briefly outlined, including the testing programme to optimise conditions in the machine to achieve ignition, and its safety work. (U.K.)

  3. Effects of cyanobacterial-driven pH increases on sediment nutrient fluxes and coupled nitrification-denitrification in a shallow fresh water estuary

    Directory of Open Access Journals (Sweden)

    Y. Gao

    2012-07-01

    Full Text Available Summer cyanobacterial blooms caused an elevation in pH (9 to ~10.5 that lasted for weeks in the shallow and tidal-fresh region of the Sassafras River, a tributary of Chesapeake Bay (USA. Elevated pH promoted desorption of sedimentary inorganic phosphorus and facilitated conversion of ammonium (NH4+ to ammonia (NH3. In this study, we investigated pH effects on exchangeable NH4+ desorption, pore water diffusion and the flux rates of NH4+, soluble reactive phosphorus (SRP and nitrate (NO3, nitrification, denitrification, and oxygen consumption. Elevated pH enhanced desorption of exchangeable NH4+ through NH3 formation from both pore water and adsorbed NH4+ pools. Progressive penetration of high pH from the overlying water into sediment promoted the mobility of SRP and the release of total ammonium (NH4+ and NH3 into the pore water. At elevated pH levels, high sediment-water effluxes of SRP and total ammonium were associated with reduction of nitrification, denitrification and oxygen consumption rates. Alkaline pH and the toxicity of NH3 may inhibit nitrification in the thin aerobic zone, simultaneously constraining coupled nitrification–denitrification with limited NO3 supply and high pH penetration into the anaerobic zone. Geochemical feedbacks to pH elevation, such as enhancement of dissolved nutrient effluxes and reduction in N2 loss via denitrification, may enhance the persistence of cyanobacterial blooms in shallow water ecosystems.

  4. Nitrous oxide in the Schelde estuary: production by nitrification and emission to the atmosphere

    NARCIS (Netherlands)

    De Wilde, H.; De Bie, M.J.M.

    2000-01-01

    Concentrations of nitrous oxide (N2O), oxygen, nitrate, and ammonium, as well as nitrification activity were determined along the salinity gradient of the Schelde Estuary, Northwest Europe, in October 1993, March 1994, and July 1996, The entire estuary was always supersaturated with N2O.

  5. Drinking Water Microbiome as a Screening Tool for Nitrification in Chloraminated Drinking Water Distribution Systems (abstract)

    Science.gov (United States)

    Many water utilities in the US using chloramine as disinfectant treatment in their distribution systems have experienced nitrification episodes, which detrimentally impact the water quality. Here, we used 16S rRNA sequencing data to generate high-resolution taxonomic profiles of...

  6. External and internal sources which inhibit the nitrification process in wastewater treatment plants

    DEFF Research Database (Denmark)

    Sinkjær, O.; Bøgebjerg, P.; Grüttner, H.

    1996-01-01

    the nitrification capacity monitored at the pilot plants has been in agreement with the design basis. The recycling of the scrubber water from the cleaning of sludge incineration flue gas was found to be an important internal source of inhibition at the Lynetten WWTP. Investigations show that it is possible...

  7. Effects of moisture level and potassium on NH4+ nitrification and ...

    African Journals Online (AJOL)

    To understand the impact of moisture level and potassium on NH4+ nitrification a greenhouse and laboratory studies were conducted using surface soil of Typic Hapludert (0–30 cm) of Ginchi, central Ethiopia. The treatments were two levels of moisture and three levels of fertilizer (six combinations replicated three times).

  8. Effects of graphite nanoparticles on nitrification in an activated sludge system.

    Science.gov (United States)

    Dong, Qian; Liu, Yanchen; Shi, Hanchang; Huang, Xia

    2017-09-01

    Graphite nanoparticles (GNPs) might result in unexpected effects during their transportation and transformation in wastewater treatment systems, including strong thermo-catalytic and catalytic effects and microbial cytotoxicity. In particular, the effects of GNPs on the nitrification process in activated sludge systems should be addressed. This study aimed to estimate the influence of GNPs on the nitrification process in a short-term nitrification reactor with exposure to different light sources. The results indicated that GNPs could only improve the efficiency of photothermal transformation slightly in the activated sludge system because of its photothermal effects under the standard illuminant (imitating 1 × sun). However, even with better photothermal effects, the nitrification efficiency still decreased significantly with GNP dosing under the standard illuminant, which might result from stronger cytotoxic effects of GNPs on the nitrifying bacteria. The disappearance of extracellular polymeric substances (EPS) around bacterial cells was observed, and the total quantity of viable bacteria decreased significantly after GNP exposuring. Variation in bacterial groups primarily occurred in nitrifying microbial communities, including Nitrosomonas sp., Nitrosospira sp., Comamonas sp. and Bradyrhizobiace sp. Nitrifiers significantly decreased, while the phyla Gammaproteobacteria, Deinocccus, and Bacteroidetes exhibited greater stability during GNP treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Marszal, Anna Joanna; Bourrelle, Julien S.; Gustavsen, Arild

    2010-01-01

    and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...

  10. Getting to Net Zero

    Energy Technology Data Exchange (ETDEWEB)

    2016-09-01

    The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.

  11. Pro NET Best Practices

    CERN Document Server

    Ritchie, Stephen D

    2011-01-01

    Pro .NET Best Practices is a practical reference to the best practices that you can apply to your .NET projects today. You will learn standards, techniques, and conventions that are sharply focused, realistic and helpful for achieving results, steering clear of unproven, idealistic, and impractical recommendations. Pro .NET Best Practices covers a broad range of practices and principles that development experts agree are the right ways to develop software, which includes continuous integration, automated testing, automated deployment, and code analysis. Whether the solution is from a free and

  12. Characteristics of N2O production and hydroxylamine variation in short-cut nitrification SBR process.

    Science.gov (United States)

    Hu, Bo; Ye, Junhong; Zhao, Jianqiang; Ding, Xiaoqian; Yang, Liwei; Tian, Xiaolei

    2018-01-01

    In order to study the characteristics of nitrous oxide (N 2 O) production and hydroxylamine (NH 2 OH) variation under oxic conditions, concentrations of NH 2 OH and N 2 O were simultaneously monitored in a short-cut nitrification sequencing batch reactor (SBR) operated with different influent ammonia concentrations. In the short-cut nitrification process, N 2 O production was increased with the increasing of ammonia concentration in influent. The maximum concentrations of dissolved N 2 O-N in the reactor were 0.11 mg/L and 0.52 mg/L when ammonia concentrations in the influent were 50 mg/L and 70 mg/L respectively. Under the low and medium ammonia load phases, the concentrations of NH 2 OH-N in the reactor were remained at a low level which fluctuated around 0.06 mg/L in a small range, and did not change with the variation of influent NH 4 + -N concentration. Based on the determination results, the half-saturation of NH 2 OH in the biochemical conversion process of NH 2 OH to NO 2 - -N was very small, and the value of 0.05 mg NH 2 OH-N/L proposed in the published literature was accurate. NH 2 OH is an important intermediate in the nitrification process, and the direct determination of NH 2 OH in the nitrification process was beneficial for revealing the kinetic process of NH 2 OH production and consumption as well as the effects of NH 2 OH on N 2 O production in the nitrification process.

  13. Developing a chloramine decay index to understand nitrification: A case study of two chloraminated drinking water distribution systems.

    Science.gov (United States)

    Moradi, Sina; Liu, Sanly; Chow, Christopher W K; van Leeuwen, John; Cook, David; Drikas, Mary; Amal, Rose

    2017-07-01

    The management of chloramine decay and the prevention of nitrification are some of the critical issues faced by water utilities that use chloramine as a disinfectant. In this study, potential association between high performance size exclusion chromatography (HPSEC) data obtained with multiple wavelength Ultraviolet (UV) detection from two drinking water distribution systems in Australia and nitrification occurrence was investigated. An increase in the absorbance signal of HPSEC profiles with UV detection at λ=230nm between apparent molecular weights of 200 to 1000Da was observed at sampling sites that experienced rapid chloramine decay and nitrification while its absorbance signal at λ=254nm decreased. A chloramine decay index (C.D.I) defined as the ratio of area beneath the HPSEC spectra at two different wavelengths of 230 and 254nm, was used in assessing chloramine decay occurrences. The C.D.Is of waters at locations that experienced nitrification were consistently higher than locations not experiencing nitrification. A simulated laboratory study showed that the formation of nitrite/nitrate and/or soluble microbial products and/or the release of extracellular polymeric substances (EPS) during nitrification may contribute to the C.D.I. increase. These findings suggest that C.D.I derived from HPSEC with multiple wavelength UV detection could be an informative index to track the occurrence of rapid chloramine decay and nitrification. Copyright © 2016. Published by Elsevier B.V.

  14. PhysioNet

    Data.gov (United States)

    U.S. Department of Health & Human Services — The PhysioNet Resource is intended to stimulate current research and new investigations in the study of complex biomedical and physiologic signals. It offers free...

  15. Blanket testing in NET

    International Nuclear Information System (INIS)

    Chazalon, M.; Daenner, W.; Libin, B.

    1989-01-01

    The testing stages in NET for the performance assessment of the various breeding blanket concepts developed at the present time in Europe for DEMO (LiPb and ceramic blankets) and the requirements upon NET to perform these tests are reviewed. Typical locations available in NET for blanket testing are the central outboard segments and the horizontal ports of in-vessel sectors. These test positions will be connectable with external test loops. The number of test loops (helium, water, liquid metal) will be such that each major class of blankets can be tested in NET. The test positions, the boundary conditions and the external test loops are identified and the requirements for test blankets are summarized (author). 6

  16. Net Community and Gross Photosynthetic Production Rates in the Eastern Tropical South Pacific, as Determined from O2/AR Ratios and Triple Oxygen Isotopic Composition of Dissolved O2

    Science.gov (United States)

    Prokopenko, M. G.; Yeung, L. Y.; Berelson, W.; Fleming, J.; Rollins, N.; Young, E. D.; Haskell, W. Z.; Hammond, D. E.; Capone, D. G.

    2010-12-01

    This study assesses the rates of ocean carbon production and its fate with respect to recycling or export in the Eastern Tropical South Pacific (ETSP). ETSP has been previously identified as a region where N2 fixation and denitrification may be spatially coupled; this is also a region of localized CO2 outgassing. Using an Equilibrated Inlet Mass Spectrometer (EIMS) system, we obtained continuous measurements of the biological O2 supersaturation in the mixed layer along the ship track encompassing a region bounded by 10-20° S and 80-100° W in January - March, 2010. Vertical profiles were also taken at selected stations and analyzed for dissolved O2/Ar ratios on EIMS and triple oxygen isotope composition (17O excess) on a multi-collector IRMS (Isotope Ratio Mass Spectrometer) at UCLA. Gas exchange rates were estimated using two approaches: the Rn-222 deficit method and the wind parameterization method, which utilized wind speeds extracted from ASCAT satellite database. Oxygen Net Community Production (O-NCP) rates calculated based on biological O2 supersaturation ranged from slightly negative to ~ 0.3 - 15 mmol/m2d, with higher rates along the northern part of the transect. Oxygen Gross Community Production (O-GPP) rates calculated from 17O excess were between 50 ± 20 and 200 ± 40 mmol/m2d, with higher rates observed along the northern cruise transect as well. Notably, the NCP/GPP ratios along the northern transect were higher by the factor of 2 to 3 than their southern counterparts. The O2/Ar-based NCP rates were comparable to POC flux measured with floating traps deployed at the southern stations, but exceeded by a factor of 5-10 the trap POC fluxes obtained at the northern stations. A one-dimensional box model has been constructed to quantify the magnitude of oxygen primary production below the mixed layer. The results of this work will be integrated with measurements of 15-N2 uptake that are in progress, to constrain the potential contribution of N2 fixation

  17. Programming NET 35

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Bestselling author Jesse Liberty and industry expert Alex Horovitz uncover the common threads that unite the .NET 3.5 technologies, so you can benefit from the best practices and architectural patterns baked into the new Microsoft frameworks. The book offers a Grand Tour" of .NET 3.5 that describes how the principal technologies can be used together, with Ajax, to build modern n-tier and service-oriented applications. "

  18. NET SALARY ADJUSTMENT

    CERN Multimedia

    Finance Division

    2001-01-01

    On 15 June 2001 the Council approved the correction of the discrepancy identified in the net salary adjustment implemented on 1st January 2001 by retroactively increasing the scale of basic salaries to achieve the 2.8% average net salary adjustment approved in December 2000. We should like to inform you that the corresponding adjustment will be made to your July salary. Full details of the retroactive adjustments will consequently be shown on your pay slip.

  19. Fluorescence Sensors for Early Detection of Nitrification in Drinking Water Distribution Systems - Interference Corrections and Feasibility Assessment

    Science.gov (United States)

    Do, T. D.; Pifer, A.; Chowdhury, Z.; Wahman, D.; Zhang, W.; Fairey, J.

    2017-12-01

    Detection of nitrification events in chloraminated drinking water distribution systems remains an ongoing challenge for many drinking water utilities, including Dallas Water Utilities (DWU) and the City of Houston (CoH). Each year, these utilities experience nitrification events that necessitate extensive flushing, resulting in the loss of billions of gallons of finished water. Biological techniques used to quantify the activity of nitrifying bacteria are impractical for real-time monitoring because they require significant laboratory efforts and/or lengthy incubation times. At present, DWU and CoH regularly rely on physicochemical parameters including total chlorine and monochloramine residual, and free ammonia, nitrite, and nitrate as indicators of nitrification, but these metrics lack specificity to nitrifying bacteria. To improve detection of nitrification in chloraminated drinking water distribution systems, we seek to develop a real-time fluorescence-based sensor system to detect the early onset of nitrification events by measuring the fluorescence of soluble microbial products (SMPs) specific to nitrifying bacteria. Preliminary data indicates that fluorescence-based metrics have the sensitivity to detect these SMPs in the early stages of nitrification, but several remaining challenges will be explored in this presentation. We will focus on benchtop and sensor results from ongoing batch and annular reactor experiments designed to (1) identify fluorescence wavelength pairs and data processing techniques suitable for measurement of SMPs from nitrification and (2) assess and correct potential interferences, such as those from monochloramine, pH, iron, nitrite, nitrate and humic substances. This work will serve as the basis for developing fluorescence sensor packages for full-scale testing and validation in the DWU and CoH systems. Findings from this research could be leveraged to identify nitrification events in their early stages, facilitating proactive

  20. Tracking and quantification of nitrifying bacteria in biofilm and mixed liquor of a partial nitrification MBBR pilot plant using fluorescence in situ hybridization

    Energy Technology Data Exchange (ETDEWEB)

    Abzazou, Tarik, E-mail: tabzazou@ub.edu [Department of Microbiology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028 Barcelona (Spain); Araujo, Rosa M., E-mail: raraujo@ub.edu [Department of Microbiology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028 Barcelona (Spain); Auset, María, E-mail: maria.auset.vallejo@acciona.com [ACCIONA AGUA, S.A., Av de les Garrigues 22, El Prat de Llobregat, 08820 Barcelona (Spain); Salvadó, Humbert, E-mail: hsalvado@ub.edu [Department of Animal Biology, Faculty of Biology, University of Barcelona, Av. Diagonal 643, 08028 Barcelona (Spain)

    2016-01-15

    A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification process for pre-treatment of ammonium-rich liquors (676 ± 195 mg L{sup −1}), and studied for 479 days under variations in hydraulic retention time. The main purpose of this work, was the study of dynamics abundance of total bacteria and single-cells nitrifying bacteria belonging to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in biofilms and mixed liquor of the plant. The microbial monitoring was successfully achieved using fluorescence in situ hybridization combined with flocs disaggregation protocol as a useful microbial monitoring tool. A partial nitrification process with a N-NH{sub 4}{sup +} removal rate of about 38.6 ± 14.8% was successfully achieved at 211 days after start-up, with a clear dominance of AOB, which accounted for 11.3 ± 17.0% of total bacterial cells compared with only 2.1 ± 4.0% of NOB. The effluent obtained was subsequently supplied to an Anammox reactor for complete ammonium treatment. - Highlights: • Partial nitrification process in a MBBR fed with ammonium-rich liquor was achieved. • The operational key parameters were the HRT and temperature. • DAPI and FISH were useful to monitoring microbial composition of MBBR pilot plant. • The AOB were the dominant nitrifying bacteria, presenting 11.3% of total bacteria. • A significant correlation (R = 0.68) between AOB and ammonia removal was found.

  1. [Effects of biochar and nitrification inhibitor incorporation on global warming potential of a vegetable field in Nanjing, China].

    Science.gov (United States)

    Li, Bo; Li, Qiao-Ling; Fan, Chang-Hua; Sun, Li-Ying; Xiong, Zheng-Qin

    2014-09-01

    The influences of biochar and nitrification inhibitor incorporation on global warming potential (GWP) of a vegetable field were studied using the static chamber and gas chromatography method. Compared with the treatments without biochar addition, the annual GWP of N2O and CH4 and vegetable yield were increased by 8.7%-12.4% and 16.1%-52.5%, respectively, whereas the greenhouse gas intensity (GHGI) were decreased by 5.4%-28.7% following biochar amendment. Nitrification inhibitor significantly reduced the N2O emission while had little influence on CH4 emission, decreased GWP by 17.5%-20.6%, increased vegetable yield by 21.2%-40.1%, and decreased the GHGI significantly. The combined application of biochar and nitrification inhibitor significantly increased both vegetable yield and GWP, but to a greater extent for vegetable yield. Therefore, nitrification inhibitor incorporation could be served as an appropriate practice for increasing vegetable yield and mitigating GHG emissions in vegetable field.

  2. Effects of urea and (NH4)2SO4 on nitrification and acidification of Ultisols from southern China.

    Science.gov (United States)

    Tong, Deli; Xu, Renkou

    2012-01-01

    The mechanisms for the effects of ammonium-based fertilizers on soil acidification in subtropical regions are not well understood. Two Ultisols collected from cropland and a tea garden in Anhui and Jiangxi Provinces in subtropical southern China, respectively, were used to study the effects of urea and (NH4)2SO4 on the nitrification and acidification of soils with incubation experiments. Nitrification occurred at very low pH with no N fertilizer added and led to lowering of the soil pH by 0.53 and 0.30 units for the soils from Jiangxi and Anhui, respectively. Addition of urea accelerated nitrification and soil acidification in both Ultisols; while nitrification was inhibited by the addition of (NH4)2SO4, and greater input of (NH4)2SO4 led to greater inhibition of nitrification. Ammonia-oxidizing bacteria (AOB) played an important role in nitrification in cropland soil under acidic conditions. Addition of urea increased the soil pH at the early stages of incubation due to hydrolysis and stimulated the increase in the AOB population, and thus accelerated nitrification and soil acidification. At the end of incubation, the pH of Ultisol from Jiangxi had decreased by 1.25, 1.54 and 1.84 units compared to maximum values for the treatments with 150, 300 and 400 mg/kg of urea-N added, respectively; the corresponding figures were 0.95, 1.25 and 1.69 for the Ultisol from Anhui. However, addition of (N-H4)2SO4 inhibited the increase in the AOB population and thus inhibited nitrification and soil acidification. Soil pH for the treatments with 300 and 400 mg/kg of (NH4)2SO4-N remained almost constant during the incubation. AOB played an important role in nitrification of the cropland soil under acidic conditions. Addition of urea stimulated the increase in the AOB population and thus accelerated nitrification and soil acidification; while addition of (NH4)2SO4 inhibited the increase in the AOB population and thus inhibited nitrification.

  3. Biological Petri Nets

    CERN Document Server

    Wingender, E

    2011-01-01

    It was suggested some years ago that Petri nets might be well suited to modeling metabolic networks, overcoming some of the limitations encountered by the use of systems employing ODEs (ordinary differential equations). Much work has been done since then which confirms this and demonstrates the usefulness of this concept for systems biology. Petri net technology is not only intuitively understood by scientists trained in the life sciences, it also has a robust mathematical foundation and provides the required degree of flexibility. As a result it appears to be a very promising approach to mode

  4. Reconfiguration of distribution nets

    International Nuclear Information System (INIS)

    Latorre Bayona, Gerardo; Angarita Marquez, Jorge Luis

    2000-01-01

    Starting of the location of the reconfiguration problem inside the context of the operation of distribution nets, of the quality indicators definition and of the presentation of the alternatives more used for reduction of technical losses, they are related diverse reconfiguration methodologies proposed in the technical literature, pointing out their three principals limitations; also are presents the results of lost obtained starting from simulation works carried out in distribution circuits of the ESSA ESP, which permitting to postulate the reconfiguration of nets like an excellent alternative to reduce technical losses

  5. NET system integration

    International Nuclear Information System (INIS)

    Farfaletti-Casali, F.; Mitchell, N.; Salpietro, E.; Buzzi, U.; Gritzmann, P.

    1985-01-01

    The NET system integration procedure is the process by which the requirements of the various Tokamak machine design areas are brought together to form a compatible machine layout. Each design area produces requirements which generally allow components to be built at minimum cost and operate with minimum technical risk, and the final machine assembly should be achieved with minimum departure from these optimum designs. This is carried out in NET by allowing flexibility in the maintenance and access methods to the machine internal components which must be regularly replaced by remote handling, in segmentation of these internal components and in the number of toroidal field coils

  6. Nitrification of leachates from manure composting under field conditions and their use in horticulture.

    Science.gov (United States)

    Cáceres, Rafaela; Magrí, Albert; Marfà, Oriol

    2015-10-01

    This work aimed to demonstrate the feasibility of nitrification applied to the treatment of leachates formed during composting of cattle and pig manure in order to promote their further use as liquid fertilizer in horticulture. Nitrification trials were successfully conducted in summer and winter seasons under Mediterranean climate conditions. Subsequently, effect of using the nitrified effluents as nutritive solution in the fertigation of lettuce (Lactuca sativa L.) was assessed in terms of productivity and nutrient uptake. Similar productivities were obtained when using the nitrified effluents and a standard nutritive solution. However, results also evidenced high nutrient uptake, which indicates that dosage should be adjusted to culture requirements. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Controls of oxygen isotope ratios of nitrate formed during nitrification in soils

    International Nuclear Information System (INIS)

    Mayer, B.; Bollwerk, S.M.; Vorhoff, B.; Mansfeldt, T.; Veizer, J.

    1999-01-01

    The isotopic composition of nitrate is increasingly used to determine sources and transformations of nitrogen in terrestrial and aquatic ecosystems. Oxygen isotope ratios of nitrate appear to be particularly useful, since they allow the differentiation between nitrate from atmospheric deposition (δ 18 O nitrate between +25 and +70 per mille), nitrate from fertilizers (δ 18 O nitrate +23 per mille), and nitrate derived from nitrification processes in soils (δ 18 O nitrate 3 molecule derive from H 2 O (with negative δ 18 O values dependent upon location) and one oxygen derives from atmospheric O 2 (δ 18 O = +23.5 per mille).. The objective of this study was to experimentally determine the extent to which water oxygen controls the δ 18 O value of nitrate, which is formed during nitrification in soils

  8. Side Effects of Nitrification Inhibitors on Non Target Microbial Processes in Soils

    OpenAIRE

    Johannes Carl Gottlieb Ottow; Gero Benckiser; Ferisman Tindaon

    2011-01-01

    Agricultural chemicals have been used extensively in modern agriculture and toxicological studies suggest a great potential for inducing undesirable effects on non target organisms. A model experiment was conducted in order to determine side effects of three nitrification inhibitors (NIs, 3,4dimethylpyrazolephosphate = DMPP, 4-Chlormethylpyrazole phosphate = ClMPP and dicyandiamide = DCD) on non target microbial processes in soils. Side effects and dose response curve of three NIs were quanti...

  9. EFFECTS OF NITRIFICATION INHIBITORS ON MINERAL NITROGEN DYNAMICS IN AGRICULTURE SOILS

    OpenAIRE

    Ferisman Tindaon; Gero Benckiser; ohannes Carl Gottlieb Ottow

    2011-01-01

    Experiments were conducted under laboratory conditions to elucidate the effect of three nitrification inhibitors viz, 3.4dimethylpyrazo-lephosphate (DMPP), 4-Chlormethylpyrazole (ClMP) and dicyandiamide (DCD) on mineral nitrogen dynamics of (NH4)2SO4 in soil incubated at 25oC in soils. The quantitative determination of ammonium, nitrite and nitrate were carried out spectrophotometrically, while potential denitrify-cation capacity (PDC) was measured gas chromatographically. DMPP, ClMP and DCD ...

  10. Effects of Nitrification Inhibitors on Mineral Nitrogen Dynamics in Agriculture Soils

    OpenAIRE

    Tindaon, Ferisman; Benckiser, Gero; Ottow, Johannes Carl Gottlieb

    2011-01-01

    Experiments were conducted under laboratory conditions to elucidate the effect of three nitrification inhibitors viz, 3.4dime-thylpyrazo-lephosphate (DMPP), 4-Chlormethylpyrazole (ClMP) and dicyandiamide (DCD) on mineral nitrogen dynamics of (NH4)2SO4 in soil incubated at 25oC in soils. The quantitative determination of ammonium, nitrite and nitrate were carried out spectrophotometrically, while potential denitrify-cation capacity (PDC) was measured gas chromatographically. DMPP, ClMP and DCD...

  11. Coloured Petri Nets

    CERN Document Server

    Jensen, Kurt

    2009-01-01

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. This book introduces the constructs of the CPN modelling language and presents the related analysis methods. It provides a comprehensive road map for the practical use of CPN.

  12. Safety nets or straitjackets?

    DEFF Research Database (Denmark)

    Ilsøe, Anna

    2012-01-01

    Does regulation of working hours at national and sector level impose straitjackets, or offer safety nets to employees seeking working time flexibility? This article compares legislation and collective agreements in the metal industries of Denmark, Germany and the USA. The industry has historically...

  13. Neuronal nets in robotics

    International Nuclear Information System (INIS)

    Jimenez Sanchez, Raul

    1999-01-01

    The paper gives a generic idea of the solutions that the neuronal nets contribute to the robotics. The advantages and the inconveniences are exposed that have regarding the conventional techniques. It also describe the more excellent applications as the pursuit of trajectories, the positioning based on images, the force control or of the mobile robots management, among others

  14. Net4Care platform

    DEFF Research Database (Denmark)

    2012-01-01

    , that in turn enables general practitioners and clinical staff to view observations. Use the menus above to explore the site's information resources. To get started, follow the short Hello, World! tutorial. The Net4Care project is funded by The Central Denmark Region and EU via Caretech Innovation....

  15. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism an...

  16. Game Theory .net.

    Science.gov (United States)

    Shor, Mikhael

    2003-01-01

    States making game theory relevant and accessible to students is challenging. Describes the primary goal of GameTheory.net is to provide interactive teaching tools. Indicates the site strives to unite educators from economics, political and computer science, and ecology by providing a repository of lecture notes and tests for courses using…

  17. BacillusRegNet

    DEFF Research Database (Denmark)

    Misirli, Goksel; Hallinan, Jennifer; Röttger, Richard

    2014-01-01

    As high-throughput technologies become cheaper and easier to use, raw sequence data and corresponding annotations for many organisms are becoming available. However, sequence data alone is not sufficient to explain the biological behaviour of organisms, which arises largely from complex molecular...... the associated BacillusRegNet website (http://bacillus.ncl.ac.uk)....

  18. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  19. Effects of C/N ratio on nitrous oxide production from nitrification in a laboratory-scale biological aerated filter reactor.

    Science.gov (United States)

    He, Qiang; Zhu, Yinying; Fan, Leilei; Ai, Hainan; Huangfu, Xiaoliu; Chen, Mei

    2017-03-01

    Emission of nitrous oxide (N 2 O) during biological wastewater treatment is of growing concern. This paper reports findings of the effects of carbon/nitrogen (C/N) ratio on N 2 O production rates in a laboratory-scale biological aerated filter (BAF) reactor, focusing on the biofilm during nitrification. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and microelectrode technology were utilized to evaluate the mechanisms associated with N 2 O production during wastewater treatment using BAF. Results indicated that the ability of N 2 O emission in biofilm at C/N ratio of 2 was much stronger than at C/N ratios of 5 and 8. PCR-DGGE analysis showed that the microbial community structures differed completely after the acclimatization at tested C/N ratios (i.e., 2, 5, and 8). Measurements of critical parameters including dissolved oxygen, oxidation reduction potential, NH 4 + -N, NO 3 - -N, and NO 2 - -N also demonstrated that the internal micro-environment of the biofilm benefit N 2 O production. DNA analysis showed that Proteobacteria comprised the majority of the bacteria, which might mainly result in N 2 O emission. Based on these results, C/N ratio is one of the parameters that play an important role in the N 2 O emission from the BAF reactors during nitrification.

  20. A dynamic model for the nitrification of higher concentrated wastewaters and control by experiments; Ein dynamisches Prozessmodell fuer die Nitrifikation hoeher belasteter Abwaesser und praktische Anwendungen

    Energy Technology Data Exchange (ETDEWEB)

    Pirsing, A. [Siemens AG, Anlagentechnik ANL A73, Karlsruhe (Germany); Wiesmann, U. [Inst. fuer Verfahrenstechnik, Technische Univ. Berlin (Germany)

    1995-07-01

    Wastewater with high ammonia concentration is produced by many industries. However, the removal of higher loaded industrial effluents still poses many questions. Dynamic modelling is helpful to understand the process of nitrification and to investigate algorithms of process control. Therefore, a dynamic model of nitrification in completely mixed reactors is proposed based on mass balances for the components ammonia, nitrite, nitrate, dissolved oxygen, carbon dioxide, pH, nitrosomonas and nitrobacter. The biological reaction rates consider oxygen limitation and substrate inhibition. The process model presented it tested by lab scale experiments using an aerated stirred tank reactor. (orig.) [Deutsch] Es wird ein mathematisches Prozessmodell fuer die Nitrifikation von Industrieabwaessern mit hoher Ammoniumkonzentration vorgestellt, das bislang vernachlaessigte Phaenomene wie z.B. Substratueberschusshemmung und Sauerstofflimitierung beruecksichtigt. Als theoretische Grundlage dienen Bilanzgleichungen fuer insgesamt acht Komponenten. Das Simulationsmodell wird durch den Vergleich mit experimentellen Ergebnissen aus einer Laborversuchsanlage auf seine Richtigkeit ueberprueft. In dem Beitrag werden auf diesem Modell basierende Anwendungsbeispiele behandelt. So werden die Moeglichkeiten der dynamischen Prozesssimulation zur Steigerung der Betriebsstabilitaet bei schwankenden Zulaufkonzentrationen und -volumenstroemen gezeigt. Darueber hinaus gelingt die Rekonstruktion der Umsatzraten r(O{sub 2}) und r(NH{sub 3}) aus der Sauerstoff- und Kohlendioxidkonzentration in der Abluft. (orig.)

  1. Impacts of organic and inorganic fertilizers on nitrification in a cold climate soil are linked to the bacterial ammonia oxidizer community.

    Science.gov (United States)

    Fan, Fenliang; Yang, Qianbao; Li, Zhaojun; Wei, Dan; Cui, Xi'an; Liang, Yongchao

    2011-11-01

    The microbiology underpinning soil nitrogen cycling in northeast China remains poorly understood. These agricultural systems are typified by widely contrasting temperature, ranging from -40 to 38°C. In a long-term site in this region, the impacts of mineral and organic fertilizer amendments on potential nitrification rate (PNR) were determined. PNR was found to be suppressed by long-term mineral fertilizer treatment but enhanced by manure treatment. The abundance and structure of ammonia-oxidizing bacterial (AOB) and archaeal (AOA) communities were assessed using quantitative polymerase chain reaction and denaturing gradient gel electrophoresis techniques. The abundance of AOA was reduced by all fertilizer treatments, while the opposite response was measured for AOB, leading to a six- to 60-fold reduction in AOA/AOB ratio. The community structure of AOA exhibited little variation across fertilization treatments, whereas the structure of the AOB community was highly responsive. PNR was correlated with community structure of AOB rather than that of AOA. Variation in the community structure of AOB was linked to soil pH, total carbon, and nitrogen contents induced by different long-term fertilization regimes. The results suggest that manure amendment establishes conditions which select for an AOB community type which recovers mineral fertilizer-suppressed soil nitrification.

  2. Insights on the marine microbial nitrogen cycle from isotopic approaches to nitrification

    Directory of Open Access Journals (Sweden)

    Karen L Casciotti

    2012-10-01

    Full Text Available The microbial nitrogen (N cycle involves a variety of redox processes that control the availability and speciation of N in the environment and are involved with the production of nitrous oxide (N2O, a climatically important greenhouse gas. Isotopic measurements of ammonium (NH4+, nitrite (NO2-, nitrate (NO3-, and N2O can now be used to track the cycling of these compounds and to infer their sources and sinks, which has lead to new and exciting discoveries. For example, dual isotope measurements of NO3- and NO2- have shown that there is NO3- regeneration in the ocean’s euphotic zone, as well as in and around oxygen deficient zones, indicating that nitrification may play more roles in the ocean’s N cycle than generally thought. Likewise, the inverse isotope effect associated with NO2- oxidation yields unique information about the role of this process in NO2- cycling in the primary and secondary NO2- maxima. Finally, isotopic measurements of N2O in the ocean are indicative of an important role for nitrification in its production. These interpretations rely on knowledge of the isotope effects for the underlying microbial processes, in particular ammonia oxidation and nitrite oxidation. Here we review the isotope effects involved with the nitrification process, the insights provided by this information, and provide a prospectus for future work in this area.

  3. Insights on the marine microbial nitrogen cycle from isotopic approaches to nitrification.

    Science.gov (United States)

    Casciotti, Karen L; Buchwald, Carolyn

    2012-01-01

    The microbial nitrogen (N) cycle involves a variety of redox processes that control the availability and speciation of N in the environment and that are involved with the production of nitrous oxide (N(2)O), a climatically important greenhouse gas. Isotopic measurements of ammonium (NH(+) (4)), nitrite (NO(-) (2)), nitrate (NO(-) (3)), and N(2)O can now be used to track the cycling of these compounds and to infer their sources and sinks, which has lead to new and exciting discoveries. For example, dual isotope measurements of NO(-) (3) and NO(-) (2) have shown that there is NO(-) (3) regeneration in the ocean's euphotic zone, as well as in and around oxygen deficient zones (ODZs), indicating that nitrification may play more roles in the ocean's N cycle than generally thought. Likewise, the inverse isotope effect associated with NO(-) (2) oxidation yields unique information about the role of this process in NO(-) (2) cycling in the primary and secondary NO(-) (2) maxima. Finally, isotopic measurements of N(2)O in the ocean are indicative of an important role for nitrification in its production. These interpretations rely on knowledge of the isotope effects for the underlying microbial processes, in particular ammonia oxidation and nitrite oxidation. Here we review the isotope effects involved with the nitrification process and the insights provided by this information, then provide a prospectus for future work in this area.

  4. An assessment of nitrification inhibitors to reduce nitrous oxide emissions from UK agriculture

    International Nuclear Information System (INIS)

    Misselbrook, T H; Cardenas, L M; Camp, V; Thorman, R E; Williams, J R; Rollett, A J; Chambers, B J

    2014-01-01

    A trial was conducted consisting of 14 experiments across sites in England of contrasting soil type and annual rainfall to assess the effectiveness of nitrification inhibitors (predominantly dicyandiamide (DCD) but limited assessment also of 3, 4-dimethylpyrazole phosphate (DMPP) and a commercial product containing two pyrazole derivatives) in reducing direct nitrous oxide (N 2 O) emissions from fertilizer nitrogen (N), cattle urine and cattle slurry applications to land. Measurements were also made of the impact on ammonia (NH 3 ) volatilization, nitrate (NO 3 − ) leaching, crop yield and crop N offtake. DCD proved to be very effective in reducing direct N 2 O emissions following fertilizer and cattle urine applications, with mean reduction efficiencies of 39, 69 and 70% for ammonium nitrate, urea and cattle urine, respectively. When included with cattle slurry a mean, non-significant reduction of 56% was observed. There were no N 2 O emission reductions observed from the limited assessments of the other nitrification inhibitors. Generally, there were no impacts of the nitrification inhibitors on NH 3 volatilization, NO 3 − leaching, crop yield or crop N offtake. Use of DCD could give up to 20% reduction in N 2 O emissions from UK agriculture, but cost-effective delivery mechanisms are required to encourage adoption by the sector. Direct N 2 O emissions from the studied sources were substantially lower than IPCC default values and development of UK country-specific emission factors for use in inventory compilation is warranted. (paper)

  5. Biodegradation of plastics in soil and effects on nitrification activity. A laboratory approach.

    Directory of Open Access Journals (Sweden)

    Giulia eBettas Ardisson

    2014-12-01

    Full Text Available The progressive application of new biodegradable plastics in agriculture calls for improved testing approaches to assure their environmental safety. Full biodegradation (≥ 90% prevents accumulation in soil, which is the first tier of testing. The application of specific ecotoxicity tests is the second tier of testing needed to show safety for the soil ecosystem. Soil microbial nitrification is widely used as a bioindicator for evaluating the impact of chemicals on soil but it is not applied for evaluating the impact of biodegradable plastics. In this work the International Standard test for biodegradation of plastics in soil (ISO 17556, 2012 was applied both to measure biodegradation and to prepare soil samples needed for a subsequent nitrification test based on another International Standard (ISO 14238, 2012. The plastic mulch film tested in this work showed full biodegradability and no inhibition of the nitrification potential of the soil in comparison with the controls. The laboratory approach suggested in this Technology Report enables (i to follow the course of biodegradation, (ii a strict control of variables and environmental conditions, (iii the application of very high concentrations of test material (to maximize the possible effects. This testing approach could be taken into consideration in improved testing schemes aimed at defining the biodegradability of plastics in soil.

  6. Biodegradation of plastics in soil and effects on nitrification activity. A laboratory approach.

    Science.gov (United States)

    Bettas Ardisson, Giulia; Tosin, Maurizio; Barbale, Marco; Degli-Innocenti, Francesco

    2014-01-01

    The progressive application of new biodegradable plastics in agriculture calls for improved testing approaches to assure their environmental safety. Full biodegradation (≥90%) prevents accumulation in soil, which is the first tier of testing. The application of specific ecotoxicity tests is the second tier of testing needed to show safety for the soil ecosystem. Soil microbial nitrification is widely used as a bioindicator for evaluating the impact of chemicals on soil but it is not applied for evaluating the impact of biodegradable plastics. In this work the International Standard test for biodegradation of plastics in soil (ISO 17556, 2012) was applied both to measure biodegradation and to prepare soil samples needed for a subsequent nitrification test based on another International Standard (ISO 14238, 2012). The plastic mulch film tested in this work showed full biodegradability and no inhibition of the nitrification potential of the soil in comparison with the controls. The laboratory approach suggested in this Technology Report enables (i) to follow the course of biodegradation, (ii) a strict control of variables and environmental conditions, (iii) the application of very high concentrations of test material (to maximize the possible effects). This testing approach could be taken into consideration in improved testing schemes aimed at defining the biodegradability of plastics in soil.

  7. Partial nitrification using aerobic granules in continuous-flow reactor: rapid startup.

    Science.gov (United States)

    Wan, Chunli; Sun, Supu; Lee, Duu-Jong; Liu, Xiang; Wang, Li; Yang, Xue; Pan, Xiangliang

    2013-08-01

    This study applied a novel strategy to rapid startup of partial nitrification in continuous-flow reactor using aerobic granules. Mature aerobic granules were first cultivated in a sequencing batch reactor at high chemical oxygen demand in 16 days. The strains including the Pseudoxanthomonas mexicana strain were enriched in cultivated granules to enhance their structural stability. Then the cultivated granules were incubated in a continuous-flow reactor with influent chemical oxygen deamnad being stepped decreased from 1,500 ± 100 (0-19 days) to 750 ± 50 (20-30 days), and then to 350 ± 50 mg l(-1) (31-50 days); while in the final stage 350 mg l(-1) bicarbonate was also supplied. Using this strategy the ammonia-oxidizing bacterium, Nitrosomonas europaea, was enriched in the incubated granules to achieve partial nitrification efficiency of 85-90% since 36 days and onwards. The partial nitrification granules were successfully harvested after 52 days, a period much shorter than those reported in literature. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Redistribution of wastewater alkalinity with a microbial fuel cell to support nitrification of reject water.

    Science.gov (United States)

    Modin, Oskar; Fukushi, Kensuke; Rabaey, Korneel; Rozendal, René A; Yamamoto, Kazuo

    2011-04-01

    In wastewater treatment plants, the reject water from the sludge treatment processes typically contains high ammonium concentrations, which constitute a significant internal nitrogen load in the plant. Often, a separate nitrification reactor is used to treat the reject water before it is fed back into the plant. The nitrification reaction consumes alkalinity, which has to be replenished by dosing e.g. NaOH or Ca(OH)(2). In this study, we investigated the use of a two-compartment microbial fuel cell (MFC) to redistribute alkalinity from influent wastewater to support nitrification of reject water. In an MFC, alkalinity is consumed in the anode compartment and produced in the cathode compartment. We use this phenomenon and the fact that the influent wastewater flow is many times larger than the reject water flow to transfer alkalinity from the influent wastewater to the reject water. In a laboratory-scale system, ammonium oxidation of synthetic reject water passed through the cathode chamber of an MFC, increased from 73.8 ± 8.9 mgN/L under open-circuit conditions to 160.1 ± 4.8 mgN/L when a current of 1.96 ± 0.37 mA (15.1 mA/L total MFC liquid volume) was flowing through the MFC. These results demonstrated the positive effect of an MFC on ammonium oxidation of alkalinity-limited reject water. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. The effect of soil properties on the toxicity of silver to the soil nitrification process.

    Science.gov (United States)

    Langdon, Kate A; McLaughlin, Mike J; Kirby, Jason K; Merrington, Graham

    2014-05-01

    Silver (Ag) is being increasingly used in a range of consumer products, predominantly as an antimicrobial agent, leading to a higher likelihood of its release into the environment. The present study investigated the toxicity of Ag to the nitrification process in European and Australian soils in both leached and unleached conditions. Overall, leaching of soils was found to have a minimal effect on the final toxicity data, with an average leaching factor of approximately 1. Across the soils, the toxicity was found to vary by several orders of magnitude, with concentrations of Ag causing a 50% reduction in nitrification relative to the controls (EC50) ranging from 0.43 mg Ag/kg to >640 mg Ag/kg. Interestingly, the dose-response relationships in most of the soils showed significant stimulation in nitrification at low Ag concentrations (i.e., hormesis), which in some cases produced responses up to double that observed in the controls. Soil pH and organic carbon were the properties found to have the greatest influence on the variations in toxicity thresholds across the soils, and significant relationships were developed that accounted for approximately 90% of the variability in the data. The toxicity relationships developed from the present study will assist in future assessment of potential Ag risks and enable the site-specific prediction of Ag toxicity. © 2014 SETAC.

  10. Solid respirometry to characterize nitrification kinetics: a better insight for modelling nitrogen conversion in vertical flow constructed wetlands.

    Science.gov (United States)

    Morvannou, Ania; Choubert, Jean-Marc; Vanclooster, Marnik; Molle, Pascal

    2011-10-15

    We developed an original method to measure nitrification rates at different depths of a vertical flow constructed wetland (VFCW) with variable contents of organic matter (sludge, colonized gravel). The method was adapted for organic matter sampled in constructed wetland (sludge, colonized gravel) operated under partially saturated conditions and is based on respirometric principles. Measurements were performed on a reactor, containing a mixture of organic matter (sludge, colonized gravel) mixed with a bulking agent (wood), on which an ammonium-containing liquid was applied. The oxygen demand was determined from analysing oxygen concentration of the gas passing through the reactor with an on-line analyzer equipped with a paramagnetic detector. Within this paper we present the overall methodology, the factors influencing the measurement (sample volume, nature and concentration of the applied liquid, number of successive applications), and the robustness of the method. The combination of this new method with a mass balance approach also allowed determining the concentration and maximum growth rate of the autotrophic biomass in different layers of a VFCW. These latter parameters are essential inputs for the VFCW plant modelling. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. SolNet

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Vajen, Klaus; Bales, Chris

    2014-01-01

    -accompanying Master courses, placements of internships, and PhD scholarship projects. A new scholarship project, “SHINE”, was launched in autumn 2013 in the frame work of the Marie Curie program of the European Union (Initial Training Network, ITN). 13 PhD-scholarships on solar district heating, solar heat......SolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference...... for industrial processes, as well as sorption stores and materials started in December 2013. Additionally, the project comprises a training program with five PhD courses and several workshops on solar thermal engineering that will be open also for other PhD students working in the field. The research projects...

  12. Turkey's net energy consumption

    International Nuclear Information System (INIS)

    Soezen, Adnan; Arcaklioglu, Erol; Oezkaymak, Mehmet

    2005-01-01

    The main goal of this study is to develop the equations for forecasting net energy consumption (NEC) using an artificial neural-network (ANN) technique in order to determine the future level of energy consumption in Turkey. In this study, two different models were used in order to train the neural network. In one of them, population, gross generation, installed capacity and years are used in the input layer of the network (Model 1). Other energy sources are used in input layer of network (Model 2). The net energy consumption is in the output layer for two models. Data from 1975 to 2003 are used for the training. Three years (1981, 1994 and 2003) are used only as test data to confirm this method. The statistical coefficients of multiple determinations (R 2 -value) for training data are equal to 0.99944 and 0.99913 for Models 1 and 2, respectively. Similarly, R 2 values for testing data are equal to 0.997386 and 0.999558 for Models 1 and 2, respectively. According to the results, the net energy consumption using the ANN technique has been predicted with acceptable accuracy. Apart from reducing the whole time required, with the ANN approach, it is possible to find solutions that make energy applications more viable and thus more attractive to potential users. It is also expected that this study will be helpful in developing highly applicable energy policies

  13. Online measurement of nitrification inhibitors in sewage received by an industrial sewage treatment plant. Development of a nitrification toximeter; Online-Messung nitrifikationshemmender Stoffe im Zulauf einer Industrieklaeranlage - Entwicklung eines Nitrifikationstoximeters

    Energy Technology Data Exchange (ETDEWEB)

    Haid, M. [BASF AG, Ludwigshafen am Rhein (Germany)

    1999-07-01

    At an industrial sewage treatment plant, the ammonium freight in the effluent is to be further reduced in the future through nitrification. But constantly low effluent concentrations are only possible if the nitrification process is not inhibited. Bouts of critical concentrations of nitrification inhibitors in sewage received by treatment plant are potentially disturbing. Online measurement of nitrification inhibitors in sewage arriving at the treatment plant is to recognize such bouts and permit timely alert so that counter-measures can be taken, which may consist in routing sewage with such toxic concentrations into a storage basin, whereby a sharp slump in the nitrification process can be avoided. (orig.) [German] In einer Industrieklaeranlage soll kuenftig durch Nitrifikation die Ammoniumfracht im Auslauf weiter gesenkt werden. Konstant niedrige Ablaufwerte sind aber nur dann moeglich, wenn der Nitrifikationsprozess ungestoert ablaufen kann. Stoesse nitrifikationshemmender Stoffe in kritischen Konzentrationen im Zulauf zur Klaeranlage sind eine moegliche Stoergroesse. Mit Hilfe einer Online-Nitrifikationshemmmessung im Klaeranlagenzulauf sollen solche Stoesse erkannt und rechtzeitig alarmiert werden, damit Gegenmassnahmen, wie z.B. das Auffangen des toxischen Stosses durch eine Sicherheitsschaltung in einem Speicherbecken, eingeleitet und so signifikante Einbrueche des Nitrifikationsprozesses vermieden werden koennen. (orig.)

  14. Net one, net two: the primary care network income statement.

    Science.gov (United States)

    Halley, M D; Little, A W

    1999-10-01

    Although hospital-owned primary care practices have been unprofitable for most hospitals, some hospitals are achieving competitive advantage and sustainable practice operations. A key to the success of some has been a net income reporting tool that separates practice operating expenses from the costs of creating and operating a network of practices to help healthcare organization managers, physicians, and staff to identify opportunities to improve the network's financial performance. This "Net One, Net Two" reporting allows operations leadership to be held accountable for Net One expenses and strategic leadership to be held accountable for Net Two expenses.

  15. Proof Nets for Lambek Calculus

    NARCIS (Netherlands)

    Roorda, Dirk

    1992-01-01

    The proof nets of linear logic are adapted to the non-commutative Lambek calculus. A different criterion for soundness of proof nets is given, which gives rise to new algorithms for proof search. The order sensitiveness of the Lambek calculus is reflected by the planarity condition on proof nets;

  16. Net metering: zero electricity bill

    International Nuclear Information System (INIS)

    Mangi, A.; Khan, Z.

    2011-01-01

    Worldwide move towards renewable energy sources, environmental concerns and decentralization of the power sector have made net metering an attractive option for power generation at small scale. This paper discusses the net metering, economical issues of renewable sources in Pakistan, technical aspects, installation suitability according to varying terrain, existing utility rules and formulation of legislation for net metering making it economically attractive. (author)

  17. The Net Advance of Physics

    Science.gov (United States)

    THE NET ADVANCE OF PHYSICS Review Articles and Tutorials in an Encyclopædic Format Established 1995 [Link to MIT] Computer support for The Net Advance of Physics is furnished by The Massachusetts Newest Additions SPECIAL FEATURES: Net Advance RETRO: Nineteenth Century Physics History of Science

  18. 78 FR 72393 - Net Investment Income Tax

    Science.gov (United States)

    2013-12-02

    ... of Article 23 (Relief from Double Taxation) of the 2006 United States Model Income Tax Convention... taxation of ANSTs at the lowest individual tax rate. Furthermore, section 646 treats all distributions, to... of Net Investment Income. The regulations affect individuals, estates, and trusts whose incomes meet...

  19. Modeling nitrous oxide production during biological nitrogen removal via nitrification and denitrification: extensions to the general ASM models.

    Science.gov (United States)

    Ni, Bing-Jie; Ruscalleda, Maël; Pellicer-Nàcher, Carles; Smets, Barth F

    2011-09-15

    Nitrous oxide (N(2)O) can be formed during biological nitrogen (N) removal processes. In this work, a mathematical model is developed that describes N(2)O production and consumption during activated sludge nitrification and denitrification. The well-known ASM process models are extended to capture N(2)O dynamics during both nitrification and denitrification in biological N removal. Six additional processes and three additional reactants, all involved in known biochemical reactions, have been added. The validity and applicability of the model is demonstrated by comparing simulations with experimental data on N(2)O production from four different mixed culture nitrification and denitrification reactor study reports. Modeling results confirm that hydroxylamine oxidation by ammonium oxidizers (AOB) occurs 10 times slower when NO(2)(-) participates as final electron acceptor compared to the oxic pathway. Among the four denitrification steps, the last one (N(2)O reduction to N(2)) seems to be inhibited first when O(2) is present. Overall, N(2)O production can account for 0.1-25% of the consumed N in different nitrification and denitrification systems, which can be well simulated by the proposed model. In conclusion, we provide a modeling structure, which adequately captures N(2)O dynamics in autotrophic nitrification and heterotrophic denitrification driven biological N removal processes and which can form the basis for ongoing refinements.

  20. Effects of inoculum type and bulk dissolved oxygen concentration on achieving partial nitrification by entrapped-cell-based reactors.

    Science.gov (United States)

    Rongsayamanont, Chaiwat; Limpiyakorn, Tawan; Khan, Eakalak

    2014-07-01

    An entrapment of nitrifiers into gel matrix is employed as a tool to fulfill partial nitrification under non-limiting dissolved oxygen (DO) concentrations in bulk solutions. This study aims to clarify which of these two attributes, inoculum type and DO concentration in bulk solutions, is the decisive factor for partial nitrification in an entrapped-cell based system. Four polyvinyl alcohol entrapped inocula were prepared to have different proportions of nitrite-oxidizing bacteria (NOB) and nitrite-oxidizing activity. At a DO concentration of 3 mg l(-1), the number of active NOB cells in an inoculum was the decisive factor for partial nitrification enhancement. However, when the DO concentration was reduced to 2 mg l(-1), all entrapped cell inocula showed similar degrees of partial nitrification. The results suggested that with the lower bulk DO concentration, the preparation of entrapped cell inocula is not useful as the DO level becomes the decisive factor for achieving partial nitrification. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Horizontal ichthyoplankton tow-net system with unobstructed net opening

    Science.gov (United States)

    Nester, Robert T.

    1987-01-01

    The larval fish sampler described here consists of a modified bridle, frame, and net system with an obstruction-free net opening and is small enough for use on boats 10 m or less in length. The tow net features a square net frame attached to a 0.5-m-diameter cylinder-on-cone plankton net with a bridle designed to eliminate all obstructions forward of the net opening, significantly reducing currents and vibrations in the water directly preceding the net. This system was effective in collecting larvae representing more than 25 species of fish at sampling depths ranging from surface to 10 m and could easily be used at greater depths.

  2. Effect of irrigation, nitrogen application, and a nitrification inhibitor on nitrous oxide, carbon dioxide and methane emissions from an olive (Olea europaea L.) orchard

    Energy Technology Data Exchange (ETDEWEB)

    Maris, S.C., E-mail: stefania@macs.udl.cat [University of Lleida, Environment and Soil Science Department, Av. Alcalde Rovira Roure 191, E-25198 Lleida (Spain); Teira-Esmatges, M.R. [University of Lleida, Environment and Soil Science Department, Av. Alcalde Rovira Roure 191, E-25198 Lleida (Spain); Arbonés, A.; Rufat, J. [Programa Ús Eficient de l’Aigua, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Parc Científic i Tecnològic Agroalimentari de Lleida (PCiTAL). Parc de Gardeny, Edifici Fruitcentre, E-2503 Lleida (Spain)

    2015-12-15

    Drip irrigation combined with nitrogen (N) fertigation is applied in order to save water and improve nutrient efficiency. Nitrification inhibitors reduce greenhouse gas emissions. A field study was conducted to compare the emissions of nitrous oxide (N{sub 2}O), carbon dioxide (CO{sub 2}) and methane (CH{sub 4}) associated with the application of N fertiliser through fertigation (0 and 50 kg N ha{sup −1}), and 50 kg N ha{sup −1} + nitrification inhibitor in a high tree density Arbequina olive orchard. Spanish Arbequina is the most suited variety for super intensive olive groves. This system allows reducing production costs and increases crop yield. Moreover its oil has excellent sensorial features. Subsurface drip irrigation markedly reduced N{sub 2}O and N{sub 2}O + N{sub 2} emissions compared with surface drip irrigation. Fertiliser application significantly increased N{sub 2}O + N{sub 2}, but not N{sub 2}O emissions. Denitrification was the main source of N{sub 2}O. The N{sub 2}O losses (calculated as emission factor) ranging from − 0.03 to 0.14% of the N applied, were lower than the IPCC (2007) values. The N{sub 2}O + N{sub 2} losses were the largest, equivalent to 1.80% of the N applied, from the 50 kg N ha{sup −1} + drip irrigation treatment which resulted in water filled pore space > 60% most of the time (high moisture). Nitrogen fertilisation significantly reduced CO{sub 2} emissions in 2011, but only for the subsurface drip irrigation strategies in 2012. The olive orchard acted as a net CH{sub 4} sink for all the treatments. Applying a nitrification inhibitor (DMPP), the cumulative N{sub 2}O and N{sub 2}O + N{sub 2} emissions were significantly reduced with respect to the control. The DMPP also inhibited CO{sub 2} emissions and significantly increased CH{sub 4} oxidation. Considering global warming potential, greenhouse gas intensity, cumulative N{sub 2}O emissions and oil production, it can be concluded that applying DMPP with 50 kg N ha{sup −1

  3. Master Robotic Net

    Directory of Open Access Journals (Sweden)

    Vladimir Lipunov

    2010-01-01

    Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

  4. Ureic nitrogen transformation in multi-layer soil columns treated with urease and nitrification inhibitors.

    Science.gov (United States)

    Giovannini, Camilla; Garcia-Mina, Josè M; Ciavatta, Claudio; Marzadori, Claudio

    2009-06-10

    The use of N-(n-butyl)thiophosphoric triamide (NBPT), as a urease inhibitor, is one of the most successful strategies utilized to increase the efficiency of urea-based fertilization. To date, NBPT has been added to the soil incorporated in fertilizers containing either urea or the inhibitor at a fixed percentage on the urea weight. The possibility of using NBPT physically separated from urea-based fertilizers could make its use more flexible. In particular, a granulated product containing NBPT could be utilized in soils treated with different urea-based fertilizers including livestock urine, the amount depending on soil characteristics and/or the urea source (e.g., mineral fertilizer, organo-mineral fertilizer, or animal slurry). In this study, a multilayer soil column device was used to investigate the influence of an experimental granular product (RV) containing NBPT and a garlic extract, combining the ability to protect NBPT by oxidation and nitrification inhibition activity, on (a) spatial variability of soil urease and nitrification activities and (b) timing of urea hydrolysis and mineral-N form accumulation (NO(2)(-), NO(3)(-), NH(4)(+)) in soil treated with urea. The results clearly demonstrated that RV can, effectively, inhibit the soil urease activity along the soil column profile up to 8-10 cm soil layer depth and that the inhibition power of RV was dependent on time and soil depth. However, nitrification activity is not significantly influenced by RV addition. In addition, the soil N transformations were clearly affected by RV; in fact, RV retarded urea hydrolysis and reduced the accumulation of NH(4)(+)-N and NO(2)(-)-N ions along the soil profile. The RV product was demonstrated to be an innovative additive able to modify some key ureic N trasformation processes correlated with the efficiency of the urea-based fertilization, in a soil column higher than 10 cm.

  5. Land Use Effects on Net Greenhouse Gas Fluxes in the US Great Plains: Historical Trends and Model Projections

    Science.gov (United States)

    Del Grosso, S. J.; Parton, W. J.; Ojima, D. S.; Mosier, A. R.; Mosier, A. R.; Paustian, K.; Peterson, G. A.

    2001-12-01

    We present maps showing regional patterns of land use change and soil C levels in the US Great Plains during the 20th century and time series of net greenhouse gas fluxes associated with different land uses. Net greenhouse gas fluxes were calculated by accounting for soil CO2 fluxes, the CO2 equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Both historical and modern agriculture in this region have been net sources of greenhouse gases. The primary reason for this, prior to 1950, is that agriculture mined soil C and resulted in net CO2 emissions. When chemical N fertilizer became widely used in the 1950's agricultural soils began to sequester CO2-C but these soils were still net greenhouse gas sources if the effects of increased N2O emissions and decreased CH4 uptake are included. The sensitivity of net greenhouse gas fluxes to conventional and alternative land uses was explored using the DAYCENT ecosystem model. Model projections suggest that conversion to no-till, reduction of the fallow period, and use of nitrification inhibitors can significantly decrease net greenhouse gas emissions in dryland and irrigated systems, while maintaining or increasing crop yields.

  6. Limitations of shallow nets approximation.

    Science.gov (United States)

    Lin, Shao-Bo

    2017-10-01

    In this paper, we aim at analyzing the approximation abilities of shallow networks in reproducing kernel Hilbert spaces (RKHSs). We prove that there is a probability measure such that the achievable lower bound for approximating by shallow nets can be realized for all functions in balls of reproducing kernel Hilbert space with high probability, which is different with the classical minimax approximation error estimates. This result together with the existing approximation results for deep nets shows the limitations for shallow nets and provides a theoretical explanation on why deep nets perform better than shallow nets. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Shielding calculations for NET

    International Nuclear Information System (INIS)

    Verschuur, K.A.; Hogenbirk, A.

    1991-05-01

    In the European Fusion Technology Programme there is only a small activity on research and development for fusion neutronics. Never-the-less, looking further than blanket design now, as ECN is getting involved in design of radiation shields for the coils and biological shields, it becomes apparent that fusion neutronics as a whole still needs substantial development. Existing exact codes for calculation of complex geometries like MCNP and DORT/TORT are put over the limits of their numerical capabilities, whilst approximate codes for complex geometries like FURNACE and MERCURE4 are put over the limits of their modelling capabilities. The main objective of this study is just to find out how far we can get with existing codes in obtaining reliable values for the radiation levels inside and outside the cryostat/shield during operation and after shut-down. Starting with a 1D torus model for preliminary parametric studies, more dimensional approximation of the torus or parts of it including the main heterogeneities should follow. Regular contacts with the NET-Team are kept, to be aware of main changes in NET design that might affect our calculation models. Work on the contract started 1 July 1990. The technical description of the contract is given. (author). 14 refs.; 4 figs.; 1 tab

  8. Can nitrification bring us to Mars? The role of microbial interactions on nitrogen recovery in life support systems

    Science.gov (United States)

    Christiaens, Marlies E. R.; Lasseur, Christophe; Clauwaert, Peter; Boon, Nico; Ilgrande, Chiara; Vlaeminck, Siegfried

    2016-07-01

    Human habitation in space requires artificial environment recirculating fundamental elements to enable the highest degree of autonomy . The European Space Agency, supported by a large consortoium of European organisationsdevelop the Micro-Ecological Life Support System (MELiSSA) to transform the mission wastes waste (a.o. organic fibers, CO2, and urine) into water, oxygen, and food (Lasseur et al., 2010). Among these wastes, astronauts' urine has a high potential to provide nitrogen as a fertilizer for food production. As higher plant growth in space is typically proposed to be performed in hydroponics, liquid fertilizer containing nitrates is preferred. An Additional Unit for Water Treatment is developed for urine nitrification by means of a synthetic microbial community. The key players in this consortium are ureolytic bacteria to hydrolyse the main nitrogen source in urine, urea, to ammonium and carbon dioxide as well as oxidation of organic compounds present in urine, ammonium oxidizing bacteria (AOB) to convert ammonium to nitrite (nitritation), and the nitrate oxidizing bacteria (NOB) to produce nitrate (nitratation). Pure AOB strains Nitrosomonas ureae Nm10 and Nitrosomonas europaea ATCC 19718, pure NOB strains Nitrobacter winogradskyi Nb-255 and Nitrobacter vulgaris Z, and interactions within synthetic consortia of one AOB and one NOB or all together were tested. As the initial salinity of fresh urine can be as high as 30 mS/cm, the functionality of selected pure strains and synthetic consortia was evaluated by means of the nitritation and nitratation activity at varying NaCl salinities (5, 10, and 30 mS/cm). The nitritation activity of pure AOB strains was compared with the synthetic consortia. Both N. ureae and Ns. europaea benefit from the presence of Nb. winogradskyi as the ammonium oxidation rates of 1.7 ± 0.7 and 6.4 ± 0.6 mg N/L.d at 5 mS/cm, respectively, doubled. These results are in line with the findings of Perez et al (2015) observing a lower

  9. Succession of Biofilm Microbial Community during Nitrification in Lab-Scale Reactors Simulating Chloraminated Drinking Water Distribution System Conditions: the Impact of Simultaneously Increasing Monochloramine and Chlorine to Nitrogen Mass Ratios

    Science.gov (United States)

    Chloramination has been shown to promote nitrifying bacteria and 30 to 63% of utility plants using secondary chloramine disinfection experience nitrification episodes. Although nitrifying bacteria are not considered human pathogens, nitrification can affect drinking water qualit...

  10. Nitrogen management in grasslands and forage-based production systems – Role of biological nitrification inhibition (BNI

    Directory of Open Access Journals (Sweden)

    G.V. Subbarao

    2013-12-01

    Full Text Available Nitrogen (N, the most critical and essential nutrient for plant growth, largely determines the productivity in both extensive and intensive grassland systems. Nitrification and denitrification processes in the soil are the primary drivers of generating reactive N (NO3-, N2O and NO, largely responsible for N loss and degradation of grasslands. Suppressing nitrification can thus facilitate retention of soil N to sustain long-term productivity of grasslands and forage-based production systems. Certain plants can suppress soil nitrification by releasing inhibitors from roots, a phenomenon termed ‘biological nitrification inhibition’ (BNI. Recent methodological developments [e.g. bioluminescence assay to detect biological nitrification inhibitors (BNIs from plant-root systems] led to significant advances in our ability to quantify and characterize BNI function in pasture grasses. Among grass pastures, BNI capacity is strongest in low-N environment grasses such as Brachiaria humidicola and weakest in high-N environment grasses such as Italian ryegrass (Lolium perenne and B. brizantha. The chemical identity of some of the BNIs produced in plant tissues and released from roots has now been established and their mode of inhibitory action determined on nitrifying Nitrosomonas bacteria. Synthesis and release of BNIs is a highly regulated and localized process, triggered by the presence of NH4+ in the rhizosphere, which facilitates release of BNIs close to soil-nitrifier sites. Substantial genotypic variation is found for BNI capacity in B. humidicola, which opens the way for its genetic manipulation. Field studies suggest that Brachiaria grasses suppress nitrification and N2O emissions from soil. The potential for exploiting BNI function (from a genetic improvement and a system perspective to develop production systems, that are low-nitrifying, low N2O-emitting, economically efficient and ecologically sustainable, is discussed.

  11. The equivalency between logic Petri workflow nets and workflow nets.

    Science.gov (United States)

    Wang, Jing; Yu, ShuXia; Du, YuYue

    2015-01-01

    Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.

  12. The Equivalency between Logic Petri Workflow Nets and Workflow Nets

    Science.gov (United States)

    Wang, Jing; Yu, ShuXia; Du, YuYue

    2015-01-01

    Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented. PMID:25821845

  13. Modeling Nitrous Oxide Production during Biological Nitrogen Removal via Nitrification and Denitrification: Extensions to the General ASM Models

    DEFF Research Database (Denmark)

    Ni, Bing-Jie; Ruscalleda, Maël; Pellicer i Nàcher, Carles

    2011-01-01

    on N2O production from four different mixed culture nitrification and denitrification reactor study reports. Modeling results confirm that hydroxylamine oxidation by ammonium oxidizers (AOB) occurs 10 times slower when NO2– participates as final electron acceptor compared to the oxic pathway. Among......Nitrous oxide (N2O) can be formed during biological nitrogen (N) removal processes. In this work, a mathematical model is developed that describes N2O production and consumption during activated sludge nitrification and denitrification. The well-known ASM process models are extended to capture N2O...

  14. Use of dissolved inorganic carbon isotopes to track photosynthesis, respiration, and nitrification along a 56 mile transect in the Sacramento River and San Francisco Bay

    Science.gov (United States)

    Silva, S. R.; Kendall, C.; Peek, S.; Young, M. B.

    2013-12-01

    A decline in phytoplankton stocks in the San Francisco Bay and Delta is thought to contribute to the pelagic organism decline observed over the past two decades. One factor controlling phytoplankton growth rate is the availability of nutrients. Although there is an excess of nutrients in the Bay and Delta, the type and relative abundance of nutrients is critical to phytoplankton growth. To evaluate the response of phytoplankton to nutrient sources and to better understand phytoplankton dynamics downstream, we tested the hypothesis that the δ13C values of dissolved inorganic carbon (DIC) along with conventional water chemistry analyses will record events such as increased nitrification (related to the Sacramento River Wastewater Treatment Plant ammonium input) and algal blooms, and reflect the balance between photosynthesis and bacterial respiration. Multiple parameters affect [DIC] and its δ13C, including DIC sources, pH, and biological processes. Consumption of CO2 by phytoplankton during photosynthesis and by autotrophic bacteria during nitrification both result in increases in δ13C-DIC. However, photosynthesis and nitrification have very different relationships to chlorophyll and nutrient concentrations. The balance between heterotrophic bacterial respiration and photosynthesis should be reflected in trends in DIC, nutrient, and chlorophyll concentration, and δ13C-DIC. The δ13C of DIC should also be reflected in the δ13C of phytoplankton with approximately a 20 per mil fractionation. Significant deviation in the fractionation factor may indicate local variations in growth rate, nutrient availability, or speciation. Combined, these parameters should provide a gauge of the relative importance of the above mentioned processes. To test this hypothesis, we collected 19 water samples per cruise between July 2012 and July 2013 along a 56 mile transect between Rio Vista on the Sacramento River and San Francisco Bay near Angel Island during 8 cruises on the USGS RV

  15. Art/Net/Work

    DEFF Research Database (Denmark)

    Andersen, Christian Ulrik; Lindstrøm, Hanne

    2006-01-01

    The seminar Art|Net|Work deals with two important changes in our culture. On one side, the network has become essential in the latest technological development. The Internet has entered a new phase, Web 2.0, including the occurrence of as ‘Wiki’s’, ‘Peer-2-Peer’ distribution, user controlled...... on the ‘network’ itself as a phenomenon and are often using technological networks as a mean of production and distribution. This changes the artistic practice and the distribution channels of art works – and the traditional notions of ‘work’, ‘origin’ and ‘rights’ are increasingly perceived as limiting...... the praxis of the artist. We see different kinds of interventions and activism (including ‘hacktivism’) using the network as a way of questioning the invisible rules that govern public and semi-public spaces. Who ‘owns’ them? What kind of social relationships do they generate? On what principle...

  16. Net4Care

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak; Hansen, Klaus Marius

    2012-01-01

    , health centers are getting larger and more distributed, and the number of healthcare professionals does not follow the trend in chronic diseases. All of this leads to a need for telemedical and mobile health applications. In a Danish context, these applications are often developed through local...... (innovative) initiatives with little regards for national and global (standardization) initiatives. A reason for this discrepancy is that the software architecture for national (and global) systems and standards are hard to understand, hard to develop systems based on, and hard to deploy. To counter this, we...... propose a software ecosystem approach for telemedicine applications, providing a framework, Net4Care, encapsulating national/global design decisions with respect to standardization while allowing for local innovation. This paper presents an analysis of existing systems, of requirements for a software...

  17. Applying the Nernst equation to simulate redox potential variations for biological nitrification and denitrification processes.

    Science.gov (United States)

    Chang, Cheng-Nan; Cheng, Hong-Bang; Chao, Allen C

    2004-03-15

    In this paper, various forms of Nernst equations have been developed based on the real stoichiometric relationship of biological nitrification and denitrification reactions. Instead of using the Nernst equation based on a one-to-one stoichiometric relation for the oxidizing and the reducing species, the basic Nernst equation is modified into slightly different forms. Each is suitable for simulating the redox potential (ORP) variation of a specific biological nitrification or denitrification process. Using the data published in the literature, the validity of these developed Nernst equations has been verified by close fits of the measured ORP data with the calculated ORP curve. The simulation results also indicate that if the biological process is simulated using an incorrect form of Nernst equation, the calculated ORP curve will not fit the measured data. Using these Nernst equations, the ORP value that corresponds to a predetermined degree of completion for the biochemical reaction can be calculated. Thus, these Nernst equations will enable a more efficient on-line control of the biological process.

  18. Continuous ammonium enrichment of a woodland stream: uptake kinetics, leaf decomposition, and nitrification

    Energy Technology Data Exchange (ETDEWEB)

    Newbold, J D; Elwood, J W; Schulze, M S; Stark, R W; Barmeier, J C

    1983-01-01

    In order to test for nitrogen limitation and examine ammonium uptake by stream sediments, ammonium hydroxide was added continuously at concentrations averaging 100 /sup +/gl/sup -1/ for 70 days to a second-order reach of Walker Branch, an undisturbed woodland stream in Tennessee. Ammonium uptake during the first 4 h of addition corresponded to adsorption kinetics rather than to first-order uptake or to Michaelis-Menten kinetics. However, the calculated adsorption partition coefficient was two to four orders of magnitude greater than values reported for physical adsorption of ammonium, suggesting that the uptake was largely biotic. Mass balance indicated that the uptake of ammonium from the water could be accounted for by increased nitrogen content in benthic organic detritus. Nitrification, inferred from longitudinal gradients in NO/sub 3/, began soon after enrichment and increased dramatically near the end of the experiment. Both ammonium and nitrate concentrations dropped quickly to near background levels when input ceased, indicating little desorption or nitrification of excess nitrogen stored in the reach. There was no evidence of nitrogen limitation as measured by weight loss, oxygen consumption, phosphorus content, and macroinvertebrate density of red oak leaf packs, or by chlorophyll content and aufwuchs biomass on plexiglass slides. A continuous phosphorus enrichment 1 year earlier had demonstrated phosphorus limitation in Walker Branch. 38 references, 6 figures, 3 tables.

  19. Microbial nitrification in throughfall of a Japanese cedar associated with archaea from the tree canopy.

    Science.gov (United States)

    Watanabe, Keiji; Kohzu, Ayato; Suda, Wataru; Yamamura, Shigeki; Takamatsu, Takejiro; Takenaka, Akio; Koshikawa, Masami Kanao; Hayashi, Seiji; Watanabe, Mirai

    2016-01-01

    To investigate the nitrification potential of phyllospheric microbes, we incubated throughfall samples collected under the canopies of Japanese cedar (Cryptomeria japonica) and analyzed the transformation of inorganic nitrogen in the samples. Nitrate concentration increased in the unfiltered throughfall after 4 weeks of incubation, but remained nearly constant in the filtered samples (pore size: 0.2 and 0.4 µm). In the unfiltered samples, δ(18)O and δ(15)N values of nitrate decreased during incubation. In addition, archaeal ammonia monooxygenase subunit A (amoA) genes, which participate in the oxidation of ammonia, were found in the throughfall samples, although betaproteobacterial amoA genes were not detected. The amoA genes recovered from the leaf surface of C. japonica were also from archaea. Conversely, nitrate production, decreased isotope ratios of nitrate, and the presence of amoA genes was not observed in rainfall samples collected from an open area. Thus, the microbial nitrification that occurred in the incubated throughfall is likely due to ammonia-oxidizing archaea that were washed off the tree canopy by precipitation.

  20. Performances and nitrification properties of biological aerated filters with zeolite, ceramic particle and carbonate media.

    Science.gov (United States)

    Qiu, Liping; Zhang, Shoubin; Wang, Guangwei; Du, Mao'an

    2010-10-01

    The performance and nitrification properties of three BAFs, with ceramic, zeolite and carbonate media, respectively, were investigated to evaluate the feasibility of employing these materials as biological aerated filter media. All three BAFs shown a promising COD and SS removal performance, while influent pH was 6.5-8.1, air-liquid ratio was 5:1 and HRT was 1.25-2.5 h, respectively. Ammonia removal in BAFs was inhibited when organic and ammonia nitrogen loading were increased, but promoted effectively with the increase pH value. Zeolite and carbonate were more suitable for nitrification than ceramic particle when influent pH below 6.5. It is feasible to employ these media in BAF and adequate bed volume has to be supplied to satisfy the requirement of removal COD, SS and ammonia nitrogen simultaneously in a biofilter. The carbonate with a strong buffer capacity is more suitable to treat the wastewater with variable or lower pH. Copyright 2010 Elsevier Ltd. All rights reserved.

  1. Partial Nitrification and Denitrifying Phosphorus Removal in a Pilot-Scale ABR/MBR Combined Process.

    Science.gov (United States)

    Wu, Peng; Xu, Lezhong; Wang, Jianfang; Huang, Zhenxing; Zhang, Jiachao; Shen, Yaoliang

    2015-11-01

    A pilot-scale combined process consisting of an anaerobic baffled reactor (ABR) and an aerobic membrane bioreactor (MBR) for the purpose of achieving easy management, low energy demands, and high efficiencies on nutrient removal from municipal wastewater was investigated. The process operated at room temperature with hydraulic retention time (HRT) of 7.5 h, recycle ratio 1 of 200%, recycle ratio 2 of 100%, and dissolved oxygen (DO) of 1 mg/L and achieved good effluent quality with chemical oxygen demand (COD) of 25 mg/L, NH4 (+)-N of 4 mg/L, total nitrogen (TN) of 11 mg/L, and total phosphorus (TP) of 0.7 mg/L. The MBR achieved partial nitrification, and NO2 (-)-N has been accumulated (4 mg/L). Efficient short-cut denitrification was occurred in the ABR with a TN removal efficiency of 51%, while the role of denitrification and phosphorus removal removed partial TN (14%). Furthermore, nitrogen was further removed (11%) by simultaneous nitrification and denitrification in the MBR. In addition, phosphorus accumulating organisms in the MBR sufficiently uptake phosphorus; thus, effluent TP further reduced with a TP removal efficiency of 84%. Analysis of fluorescence in situ hybridization (FISH) showed that ammonia oxidizing bacteria (AOB) and phosphorus accumulating organisms (PAOs) were enriched in the process. In addition, the accumulation of NO2 (-)-N was contributed to the inhibition on the activities of the NOB rather than its elimination.

  2. Near-Net Forging Technology Demonstration Program

    Science.gov (United States)

    Hall, I. Keith

    1996-01-01

    Significant advantages in specific mechanical properties, when compared to conventional aluminum (Al) alloys, make aluminum-lithium (Al-Li) alloys attractive candidate materials for use in cryogenic propellant tanks and dry bay structures. However, the cost of Al-Li alloys is typically five times that of 2219 aluminum. If conventional fabrication processes are employed to fabricate launch vehicle structure, the material costs will restrict their utilization. In order to fully exploit the potential cost and performance benefits of Al-Li alloys, it is necessary that near-net manufacturing methods be developed to off-set or reduce raw material costs. Near-net forging is an advanced manufacturing method that uses elevated temperature metal movement (forging) to fabricate a single piece, near-net shape, structure. This process is termed 'near-net' because only a minimal amount of post-forge machining is required. The near-net forging process was developed to reduce the material scrap rate (buy-to-fly ratio) and fabrication costs associated with conventional manufacturing methods. The goal for the near-net forging process, when mature, is to achieve an overall cost reduction of approximately 50 percent compared with conventional manufacturing options for producing structures fabricated from Al-Li alloys. This NASA Marshall Space Flight Center (MSFC) sponsored program has been a part of a unique government / industry partnership, coordinated to develop and demonstrate near-net forging technology. The objective of this program was to demonstrate scale-up of the near-net forging process. This objective was successfully achieved by fabricating four integrally stiffened, 170- inch diameter by 20-inch tall, Al-Li alloy 2195, Y-ring adapters. Initially, two 2195 Al-Li ingots were converted and back extruded to produce four cylindrical blockers. Conventional ring rolling of the blockers was performed to produce ring preforms, which were then contour ring rolled to produce

  3. High-level Petri Nets

    DEFF Research Database (Denmark)

    various journals and collections. As a result, much of this knowledge is not readily available to people who may be interested in using high-level nets. Within the Petri net community this problem has been discussed many times, and as an outcome this book has been compiled. The book contains reprints...... of some of the most important papers on the application and theory of high-level Petri nets. In this way it makes the relevant literature more available. It is our hope that the book will be a useful source of information and that, e.g., it can be used in the organization of Petri net courses. To make......High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable descriptions than can be obtained by means...

  4. Neural Net Safety Monitor Design

    Science.gov (United States)

    Larson, Richard R.

    2007-01-01

    The National Aeronautics and Space Administration (NASA) at the Dryden Flight Research Center (DFRC) has been conducting flight-test research using an F-15 aircraft (figure 1). This aircraft has been specially modified to interface a neural net (NN) controller as part of a single-string Airborne Research Test System (ARTS) computer with the existing quad-redundant flight control system (FCC) shown in figure 2. The NN commands are passed to FCC channels 2 and 4 and are cross channel data linked (CCDL) to the other computers as shown. Numerous types of fault-detection monitors exist in the FCC when the NN mode is engaged; these monitors would cause an automatic disengagement of the NN in the event of a triggering fault. Unfortunately, these monitors still may not prevent a possible NN hard-over command from coming through to the control laws. Therefore, an additional and unique safety monitor was designed for a single-string source that allows authority at maximum actuator rates but protects the pilot and structural loads against excessive g-limits in the case of a NN hard-over command input. This additional monitor resides in the FCCs and is executed before the control laws are computed. This presentation describes a floating limiter (FL) concept1 that was developed and successfully test-flown for this program (figure 3). The FL computes the rate of change of the NN commands that are input to the FCC from the ARTS. A window is created with upper and lower boundaries, which is constantly floating and trying to stay centered as the NN command rates are changing. The limiter works by only allowing the window to move at a much slower rate than those of the NN commands. Anywhere within the window, however, full rates are allowed. If a rate persists in one direction, it will eventually hit the boundary and be rate-limited to the floating limiter rate. When this happens, a persistent counter begins and after a limit is reached, a NN disengage command is generated. The

  5. Net neutrality and audiovisual services

    OpenAIRE

    van Eijk, N.; Nikoltchev, S.

    2011-01-01

    Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication networks: the control over the distribution of audiovisual services constitutes a vital part of the problem. In this contribution, the phenomenon of net neutrality is described first. Next, the European a...

  6. NetView technical research

    Science.gov (United States)

    1993-01-01

    This is the Final Technical Report for the NetView Technical Research task. This report is prepared in accordance with Contract Data Requirements List (CDRL) item A002. NetView assistance was provided and details are presented under the following headings: NetView Management Systems (NMS) project tasks; WBAFB IBM 3090; WPAFB AMDAHL; WPAFB IBM 3084; Hill AFB; McClellan AFB AMDAHL; McClellan AFB IBM 3090; and Warner-Robins AFB.

  7. Initial CAD investigations for NET

    International Nuclear Information System (INIS)

    Katz, F.; Leinemann, K.; Ludwig, A.; Marek, U.; Olbrich, W.; Schlechtendahl, E.G.

    1985-11-01

    This report summarizes the work done under contract no. 164/84-7/FU-D-/NET between the Commission of the European Communities and KfK during the period from June 1, 1984, through May 31, 1985. The following topics are covered in this report: Initial modelling of NET version NET2A, CAD system extension for remote handling studies, analysis of the CAD information structure, work related to the transfer of CAD information between KfK and the NET team. (orig.) [de

  8. Understanding Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Salom, Jaume; Widén, Joakim; Candanedo, José

    2011-01-01

    Although several alternative definitions exist, a Net-Zero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures...... and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid...

  9. Valuing ecosystem services. A shadow price for net primary production

    International Nuclear Information System (INIS)

    Richmond, Amy; Kaufmann, Robert K.; Myneni, Ranga B.

    2007-01-01

    We analyze the contribution of ecosystem services to GDP and use this contribution to calculate an empirical price for ecosystem services. Net primary production is used as a proxy for ecosystem services and, along with capital and labor, is used to estimate a Cobb Douglas production function from an international panel. A positive output elasticity for net primary production probably measures both marketed and nonmarketed contributions of ecosystems services. The production function is used to calculate the marginal product of net primary production, which is the shadow price for ecosystem services. The shadow price generally is greatest for developed nations, which have larger technical scalars and use less net primary production per unit output. The rate of technical substitution indicates that the quantity of capital needed to replace a unit of net primary production tends to increase with economic development, and this rate of replacement may ultimately constrain economic growth. (author)

  10. Rare, but challenging tumors: NET

    International Nuclear Information System (INIS)

    Ivanova, D.; Balev, B.

    2013-01-01

    Full text: Introduction: Gastroenteropancreatic Neuroendocrine Tumors (GEP - NET) are a heterogeneous group of tumors with different locations and many different clinical, histological, and imaging performance. In a part of them a secretion of various organic substances is present. The morbidity of GEP - NET in the EU is growing, and this leads to increase the attention to them. What you will learn: Imaging methods used for localization and staging of GEP - NET, characteristics of the study’s protocols; Classification of GEP - NET; Demonstration of typical and atypical imaging features of GEP - NET in patients registered at the NET Center at University Hospital ‘St. Marina’, Varna; Features of metastatic NET, The role of imaging in the evaluation of treatment response and follow-up of the patients. Discussion: The image semiotics analysis is based on 19 cases of GEP - NET registered NET Center at University Hospital ‘St. Marina’. The main imaging method is multidetector CT (MDCT), and magnetic resonance imaging (MRI ) has advantages in the evaluation of liver lesions and the local prevalence of anorectal tumors. In patients with advanced disease and liver lesions the assessment of skeletal involvement (MRI/ nuclear medical method) is mandatory. The majority of GEP - NET have not any specific imaging findings. Therefore it is extremely important proper planning and conducting of the study (MDCT and MR enterography; accurate assessment phase of scanning, positive and negative contrast). Conclusion: GEP - NET is a major diagnostic challenge due to the absence of typical imaging characteristics and often an overlap with those of the tumors of different origin can be observed. Therefore, a good knowledge of clinical and imaging changes occurring at different locations is needed. MDCT is the basis for the diagnosis, staging and follow-up of these neoplasms

  11. Nitrification in moving bed and fixed bed biofilters treating effluent water from a large commercial outdoor rainbow trout RAS

    DEFF Research Database (Denmark)

    Suhr, Karin; Pedersen, Per Bovbjerg

    2010-01-01

    The nitrification performance of two fixed bed (FB) biofilters and two moving bed (MB) biofilters was evaluated. They received the same cold (8 degrees C) influent water from a commercial outdoor RAS facility producing rainbow trout (average density 32 kg m(-3)). The filters were constructed as f...

  12. Meta-analysis of the effect of urease and nitrification inhibitors on crop productivity and nitrogen use efficience

    NARCIS (Netherlands)

    Abalos, D.; Jeffery, S.L.; Sanz-Cobena, A.; Guardia, G.; Vallejo, A.

    2014-01-01

    Nitrification and urease inhibitors are proposed as means to reduce nitrogen losses, thereby increasing crop nitrogen use efficiency (NUE). However, their effect on crop yield is variable. A meta-analysis was conducted to evaluate their effectiveness at increasing NUE and crop productivity. Commonly

  13. Effect of iron ions and electric field on nitrification process in the periodic reversal bio-electrocoagulation system.

    Science.gov (United States)

    Qian, Guangsheng; Hu, Xiaomin; Li, Liang; Ye, Linlin; Lv, Weijian

    2017-11-01

    This study explored the nitrification mechanism of a periodic reversal bio-electrocoagulation system with Fe-C electrodes. The ammonia nitrogen removal was compared in four identical cylindrical sequencing bath reactors. Two of them were reactors with Fe-C electrodes (S1) and C-C electrodes (S2), respectively. The other two were a reactor with iron ions (S3) and a traditional SBR (S4), respectively. The results demonstrated that the effect on enhancing nitrification in S1 was the best among all four SBRs, followed by S3, S2 and S4. Iron ions increased the biomass, and electric field improved the proton transfer and enzyme activity. The dominant bacterial genera in the four SBRs were Hyphomicrobium, Thauera, Nitrobacter, Nitrosomonas, Paracoccus and Hydrogenophaga. The iron ions may increase the levels of Nitrosomonas and Nitrobacter, both of which were the main microbes of the nitrification process. This study provided a significant and meaningful understanding of nitrification in a bio-electrocoagulation system. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. A novel bench-scale column assay to investigate site-specific nitrification biokinetics in biological rapid sand filters

    DEFF Research Database (Denmark)

    Tatari, Karolina; Smets, Barth F.; Albrechtsen, Hans-Jørgen

    2013-01-01

    A bench-scale assay was developed to obtain site-specific nitrification biokinetic information from biological rapid sand filters employed in groundwater treatment. The experimental set-up uses granular material subsampled from a full-scale filter, packed in a column, and operated with controlled...

  15. Relative nitrogen mineralization and nitrification potentials in relation to soil chemistry in oak forest soils along a historical deposition gradient

    Science.gov (United States)

    Ralph E. J. Boerner; Elaine Kennedy Sutherland

    1996-01-01

    This study quantified soil nutrient status and N mineralization/nitrification potentials in soils of oak-dominated, unmanaged forest stands in seven USDA Forest Service experimental forests (EF) ranging along a historical and current acidic deposition gradient from southern Illinois to central West Virginia.

  16. Differential contributions of ammonia oxidizers and nitrite oxidizers to nitrification in four paddy soils

    Science.gov (United States)

    Wang, Baozhan; Zhao, Jun; Guo, Zhiying; Ma, Jing; Xu, Hua; Jia, Zhongjun

    2015-01-01

    Rice paddy fields are characterized by regular flooding and nitrogen fertilization, but the functional importance of aerobic ammonia oxidizers and nitrite oxidizers under unique agricultural management is poorly understood. In this study, we report the differential contributions of ammonia-oxidizing archaea (AOA), bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to nitrification in four paddy soils from different geographic regions (Zi-Yang (ZY), Jiang-Du (JD), Lei-Zhou (LZ) and Jia-Xing (JX)) that are representative of the rice ecosystems in China. In urea-amended microcosms, nitrification activity varied greatly with 11.9, 9.46, 3.03 and 1.43 μg NO3−-N g−1 dry weight of soil per day in the ZY, JD, LZ and JX soils, respectively, over the course of a 56-day incubation period. Real-time quantitative PCR of amoA genes and pyrosequencing of 16S rRNA genes revealed significant increases in the AOA population to various extents, suggesting that their relative contributions to ammonia oxidation activity decreased from ZY to JD to LZ. The opposite trend was observed for AOB, and the JX soil stimulated only the AOB populations. DNA-based stable-isotope probing further demonstrated that active AOA numerically outcompeted their bacterial counterparts by 37.0-, 10.5- and 1.91-fold in 13C-DNA from ZY, JD and LZ soils, respectively, whereas AOB, but not AOA, were labeled in the JX soil during active nitrification. NOB were labeled to a much greater extent than AOA and AOB, and the addition of acetylene completely abolished the assimilation of 13CO2 by nitrifying populations. Phylogenetic analysis suggested that archaeal ammonia oxidation was predominantly catalyzed by soil fosmid 29i4-related AOA within the soil group 1.1b lineage. Nitrosospira cluster 3-like AOB performed most bacterial ammonia oxidation in the ZY, LZ and JX soils, whereas the majority of the 13C-AOB in the JD soil was affiliated with the Nitrosomona communis lineage. The 13C-NOB was overwhelmingly

  17. Nitrification is a primary driver of nitrous oxide production in laboratory microcosms from different land-use soils

    Directory of Open Access Journals (Sweden)

    Rui Liu

    2016-09-01

    Full Text Available Most studies on soil N2O emissions have focused either on the quantifying of agricultural N2O fluxes or on the effect of environmental factors on N2O emissions. However very limited information is available on how land-use will affect N2O production, and nitrifiers involved in N2O emissions in agricultural soil ecosystems. Therefore, this study aimed at evaluating the relative importance of nitrification and denitrification to N2O emissions from different land-use soils and identifying the potential underlying microbial mechanisms. A 15N-tracing experiment was conducted under controlled laboratory conditions on four agricultural soils collected from different land-use. We measured N2O fluxes, nitrate (NO3− and ammonium (NH4+ concentration and15N2O, 15NO3− and 15NH4+ enrichment during the incubation. Quantitative PCR was used to quantify ammonia-oxidizing archaea (AOA and ammonia-oxidizing bacteria (AOB. Our results showed that nitrification was the main contributor to N2O production in soils from sugarcane, dairy pasture and cereal cropping systems, while denitrification played a major role in N2O production in the vegetable soil under the experimental conditions. Nitrification contributed to 96.7% of the N2O emissions in sugarcane soil followed by 71.3% in the cereal cropping soil and 70.9% in the dairy pasture soil, while only around 20.0% of N2O was produced from nitrification in vegetable soil. The proportion of nitrified nitrogen as N2O (PN2O value varied across different soils, with the highest PN2O value (0.26‰ found in the cereal cropping soil, which was around 10 times higher than that in other three systems. AOA were the abundant ammonia oxidizers, and were significantly correlated to N2O emitted from nitrification in the sugarcane soil, while AOB were significantly correlated with N2O emitted from nitrification in the cereal cropping soil. Our findings suggested that soil type and land-use might have strongly affected the

  18. Nitrification Is a Primary Driver of Nitrous Oxide Production in Laboratory Microcosms from Different Land-Use Soils.

    Science.gov (United States)

    Liu, Rui; Hu, Hangwei; Suter, Helen; Hayden, Helen L; He, Jizheng; Mele, Pauline; Chen, Deli

    2016-01-01

    Most studies on soil N2O emissions have focused either on the quantifying of agricultural N2O fluxes or on the effect of environmental factors on N2O emissions. However, very limited information is available on how land-use will affect N2O production, and nitrifiers involved in N2O emissions in agricultural soil ecosystems. Therefore, this study aimed at evaluating the relative importance of nitrification and denitrification to N2O emissions from different land-use soils and identifying the potential underlying microbial mechanisms. A (15)N-tracing experiment was conducted under controlled laboratory conditions on four agricultural soils collected from different land-use. We measured N2O fluxes, nitrate ([Formula: see text]), and ammonium ([Formula: see text]) concentration and (15)N2O, (15)[Formula: see text], and (15)[Formula: see text] enrichment during the incubation. Quantitative PCR was used to quantify ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Our results showed that nitrification was the main contributor to N2O production in soils from sugarcane, dairy pasture and cereal cropping systems, while denitrification played a major role in N2O production in the vegetable soil under the experimental conditions. Nitrification contributed to 96.7% of the N2O emissions in sugarcane soil followed by 71.3% in the cereal cropping soil and 70.9% in the dairy pasture soil, while only around 20.0% of N2O was produced from nitrification in vegetable soil. The proportion of nitrified nitrogen as N2O (PN2O-value) varied across different soils, with the highest PN2O-value (0.26‰) found in the cereal cropping soil, which was around 10 times higher than that in other three systems. AOA were the abundant ammonia oxidizers, and were significantly correlated to N2O emitted from nitrification in the sugarcane soil, while AOB were significantly correlated with N2O emitted from nitrification in the cereal cropping soil. Our findings suggested that soil

  19. Linear Logic on Petri Nets

    DEFF Research Database (Denmark)

    Engberg, Uffe Henrik; Winskel, Glynn

    This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...

  20. Net neutrality and audiovisual services

    NARCIS (Netherlands)

    van Eijk, N.; Nikoltchev, S.

    2011-01-01

    Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication

  1. Properties of porous netted materials

    International Nuclear Information System (INIS)

    Daragan, V.D.; Drozdov, B.G.; Kotov, A.Yu.; Mel'nikov, G.N.; Pustogarov, A.V.

    1987-01-01

    Hydraulic and strength characteristics, efficient heat conduction and inner heat exchange coefficient are experimentally studied for porous netted materials on the base of the brass nets as dependent on porosity, cell size and method of net laying. Results of the studies are presented. It is shown that due to anisotropy of the material properties the hydraulic resistance in the direction parallel to the nets plane is 1.3-1.6 times higher than in the perpendicular one. Values of the effective heat conduction in the direction perpendicular to the nets plane at Π>0.45 agree with the data from literature, at Π<0.45 a deviation from the calculated values is marked in the direction of the heat conduction decrease

  2. Purifying capability, enzyme activity, and nitrification potentials in December in integrated vertical flow constructed wetland with earthworms and different substrates.

    Science.gov (United States)

    Xu, Defu; Gu, Jiaru; Li, Yingxue; Zhang, Yu; Howard, Alan; Guan, Yidong; Li, Jiuhai; Xu, Hui

    2016-01-01

    The response of purifying capability, enzyme activity, nitrification potentials, and total number of bacteria in the rhizosphere in December to wetland plants, substrates, and earthworms was investigated in integrated vertical flow constructed wetlands (IVFCW). The removal efficiency of total nitrogen (TN), NH4-N, chemical oxygen demand (COD), and total phosphorus (TP) was increased when earthworms were added into IVFCW. A significantly average removal efficiency of N in IVFCW that employed river sand as substrate and in IVFCW that employed a mixture of river sand and Qing sand as substrate was not found. However, the average removal efficiency of P was higher in IVFCW with a mixture of river sand and Qing sand as substrate than in IVFCW with river sand as substrate. Invertase activity in December was higher in IVFCW that used a mixture of river sand and Qing sand as substrate than in IVFCW which used only river sand as substrate. However, urease activity, nitrification potential, and total number of bacteria in December was higher in IVFCW that employed river sand as substrate than in IVFCW with a mixture of river sand and Qing sand as substrate. The addition of earthworms into the integrated vertical flow constructed wetland increased the above-ground biomass, enzyme activity (catalase, urease, and invertase), nitrification potentials, and total number of bacteria in December. The above-ground biomass of wetland plants was significantly positively correlated with urease and nitrification potentials (p earthworms into IVFCW increased enzyme activity and nitrification potentials in December, which resulted in improving purifying capability.

  3. NET remote workstation

    International Nuclear Information System (INIS)

    Leinemann, K.

    1990-10-01

    The goal of this NET study was to define the functionality of a remote handling workstation and its hardware and software architecture. The remote handling workstation has to fulfill two basic functions: (1) to provide the man-machine interface (MMI), that means the interface to the control system of the maintenance equipment and to the working environment (telepresence) and (2) to provide high level (task level) supporting functions (software tools) during the maintenance work and in the preparation phase. Concerning the man-machine interface, an important module of the remote handling workstation besides the standard components of man-machine interfacing is a module for graphical scene presentation supplementing viewing by TV. The technique of integrated viewing is well known from JET BOOM and TARM control using the GBsim and KISMET software. For integration of equipment dependent MMI functions the remote handling workstation provides a special software module interface. Task level support of the operator is based on (1) spatial (geometric/kinematic) models, (2) remote handling procedure models, and (3) functional models of the equipment. These models and the related simulation modules are used for planning, programming, execution monitoring, and training. The workstation provides an intelligent handbook guiding the operator through planned procedures illustrated by animated graphical sequences. For unplanned situations decision aids are available. A central point of the architectural design was to guarantee a high flexibility with respect to hardware and software. Therefore the remote handling workstation is designed as an open system based on widely accepted standards allowing the stepwise integration of the various modules starting with the basic MMI and the spatial simulation as standard components. (orig./HP) [de

  4. Importance of copper for nitrification in biological rapid sand filters for drinking water production

    DEFF Research Database (Denmark)

    Wagner, Florian Benedikt

    nitrification during drinking water production provided the motivation to investigate if a lack of copper could be responsible for the problems in nitrifying biofilters. Copper is believed to be an essential cofactor in the enzyme ammonia monooxygenase (AMO), which catalyzes the first essential step...... be supplied in a controlled fashion, and that little maintenance and no chemicals are required. Copper dosing through the novel electrolysis method, as well as through passive dosing from solid copper and active dosing of copper solution, was studied at nine more DWTPs, which all shared a long history...... and chemical speciation modelling were carried out for Nærum DWTP. Results showed that substantial amounts of copper were bound to iron oxide-hydroxides in the filter and that bicarbonate heavily complexed copper in the water phase. Only total copper...

  5. Influence of natural zeolite and nitrification inhibitor on organics degradation and nitrogen transformation during sludge composting.

    Science.gov (United States)

    Zhang, Junya; Sui, Qianwen; Li, Kun; Chen, Meixue; Tong, Juan; Qi, Lu; Wei, Yuansong

    2016-01-01

    Sludge composting is one of the most widely used treatments for sewage sludge resource utilization. Natural zeolite and nitrification inhibitor (NI) are widely used during composting and land application for nitrogen conservation, respectively. Three composting reactors (A--the control, B--natural zeolite addition, and C--3,4-dimethylpyrazole phosphate (DMPP) addition) were established to investigate the influence of NI and natural zeolite addition on organics degradation and nitrogen transformation during sludge composting conducted at the lab scale. The results showed that, in comparison with the control, natural zeolite addition accelerated organics degradation and the maturity of sludge compost was higher, while the DMPP addition slowed down the degradation of organic matters. Meanwhile, the nitrogen transformation functional genes including those responses for nitrification (amoA and nxrA) and denitrification (narG, nirS, nirK, and nosZ) were quantified through quantitative PCR (qPCR) to investigate the effects of natural zeolites and DMPP addition on nitrogen transformation. Although no significant difference in the abundance of nitrogen transformation functional genes was observed between treatments, addition of both natural zeolite and DMPP increases the final total nitrogen content by 48.6% and 23.1%, respectively. The ability of natural zeolite for nitrogen conservation was due to the absorption of NH3 by compost, and nitrogen conservation by DMPP was achieved by the source reduction of denitrification. Besides, it was assumed that the addition of natural zeolite and DMPP may affect the activity of these genes instead of the abundance.

  6. Controls on the variability of net infiltration to desert sandstone

    Science.gov (United States)

    Heilweil, Victor M.; McKinney, Tim S.; Zhdanov, Michael S.; Watt, Dennis E.

    2007-01-01

    As populations grow in arid climates and desert bedrock aquifers are increasingly targeted for future development, understanding and quantifying the spatial variability of net infiltration becomes critically important for accurately inventorying water resources and mapping contamination vulnerability. This paper presents a conceptual model of net infiltration to desert sandstone and then develops an empirical equation for its spatial quantification at the watershed scale using linear least squares inversion methods for evaluating controlling parameters (independent variables) based on estimated net infiltration rates (dependent variables). Net infiltration rates used for this regression analysis were calculated from environmental tracers in boreholes and more than 3000 linear meters of vadose zone excavations in an upland basin in southwestern Utah underlain by Navajo sandstone. Soil coarseness, distance to upgradient outcrop, and topographic slope were shown to be the primary physical parameters controlling the spatial variability of net infiltration. Although the method should be transferable to other desert sandstone settings for determining the relative spatial distribution of net infiltration, further study is needed to evaluate the effects of other potential parameters such as slope aspect, outcrop parameters, and climate on absolute net infiltration rates.

  7. Flood effects on efflux and net production of nitrous oxide in river floodplain soils

    Science.gov (United States)

    Riaz, Muhammad; Bruderer, Christian; Niklaus, Pascal A.; Luster, Jörg

    2016-04-01

    Floodplain soils are often rich in nutrients and exhibit high spatial heterogeneity in terms of geomorphology, soil environmental conditions and substrate availability for processes involved in carbon and nutrient cycling. In addition, fluctuating water tables lead to temporally changing redox conditions. In such systems, there are ideal conditions for the occurrence of hot spots and moments of nitrous oxide emissions, a potent greenhouse gas. The factors that govern the spatial heterogeneity and dynamics of N2O formation in floodplain soils and the surface efflux of this gas are not fully understood. A particular issue is the contribution of N2O formation in the subsoil to surface efflux. We studied this question in the floodplain of a restored section of the Thur river (NE Switzerland) which is characterized by a flashy flow regime. As a consequence, the floodplain soils are unsaturated most of the time. We showed earlier that saturation during flood pulses leads to short phases of generally anoxic conditions followed by a drying phase with anoxic conditions within aggregates and oxic conditions in larger soil pores. The latter conditions are conducive for spatially closely-coupled nitrification-denitrification and related hot moments of nitrous oxide formation. In a floodplain zone characterized by about one meter of young, sandy sediments, that are mostly covered by the tall grass Phalaris arundinacea, we measured at several time points before and after a small flood event N2O surface efflux with the closed-chamber method, and assessed N2O concentrations in the soil air at four different depths using gas-permeable tubings. In addition, we calculated the N2O diffusivity in the soil from Radon diffusivity. The latter was estimated in-situ from the recovery of Radon concentration in the gas-permeable tubings after purging with ambient air. All these data were then used to calculate net N2O production rates at different soil depths with the gradient method. In

  8. Conformal Nets II: Conformal Blocks

    Science.gov (United States)

    Bartels, Arthur; Douglas, Christopher L.; Henriques, André

    2017-08-01

    Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.

  9. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  10. Loss of protection with insecticide-treated nets against pyrethroid-resistant Culex quinquefasciatus mosquitoes once nets become holed: an experimental hut study

    Directory of Open Access Journals (Sweden)

    Irish SR

    2008-06-01

    Full Text Available Abstract Background An important advantage of pyrethroid-treated nets over untreated nets is that once nets become worn or holed a pyrethroid treatment will normally restore protection. The capacity of pyrethroids to kill or irritate any mosquito that comes into contact with the net and prevent penetration of holes or feeding through the sides are the main reasons why treated nets continue to provide protection despite their condition deteriorating over time. Pyrethroid resistance is a growing problem among Anopheline and Culicine mosquitoes in many parts of Africa. When mosquitoes become resistant the capacity of treated nets to provide protection might be diminished, particularly when holed. An experimental hut trial against pyrethroid-resistant Culex quinquefasciatus was therefore undertaken in southern Benin using a series of intact and holed nets, both untreated and treated, to assess any loss of protection as nets deteriorate with use and time. Results There was loss of protection when untreated nets became holed; the proportion of mosquitoes blood feeding increased from 36.2% when nets were intact to between 59.7% and 68.5% when nets were holed to differing extents. The proportion of mosquitoes blood feeding when treated nets were intact was 29.4% which increased to 43.6–57.4% when nets were holed. The greater the number of holes the greater the loss of protection regardless of whether nets were untreated or treated. Mosquito mortality in huts with untreated nets was 12.9–13.6%; treatment induced mortality was less than 12%. The exiting rate of mosquitoes into the verandas was higher in huts with intact nets. Conclusion As nets deteriorate with use and become increasingly holed the capacity of pyrethroid treatments to restore protection is greatly diminished against resistant Culex quinquefasciatus mosquitoes.

  11. KM3NeT

    CERN Multimedia

    KM3NeT is a large scale next-generation neutrino telescope located in the deep waters of the Mediterranean Sea, optimized for the discovery of galactic neutrino sources emitting in the TeV energy region.

  12. Pickering nuclear fish diversion net

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, J.; Lew, A. [Ontario Power Generation, Toronto, Ontario (Canada)

    2013-07-01

    Pickering Fish Diversion Net - An Engineered Environmental Solution that has significantly reduced fish impingement at the Pickering Nuclear Facility. Note: As a recent urgent request/discussed by Mark Elliot, CNE-OPG and Jacques Plourde, CNS.

  13. PolicyNet Publication System

    Data.gov (United States)

    Social Security Administration — The PolicyNet Publication System project will merge the Oracle-based Policy Repository (POMS) and the SQL-Server CAMP system (MSOM) into a new system with an Oracle...

  14. Net Neutrality: Background and Issues

    National Research Council Canada - National Science Library

    Gilroy, Angele A

    2006-01-01

    .... The move to place restrictions on the owners of the networks that compose and provide access to the Internet, to ensure equal access and nondiscriminatory treatment, is referred to as "net neutrality...

  15. Net accumulation of the Greenland ice sheet

    DEFF Research Database (Denmark)

    Kiilsholm, Sissi; Christensen, Jens Hesselbjerg; Dethloff, Klaus

    2003-01-01

    High-resolution (50 km) climate change simulations for an area covering the entire Arctic have been conducted with the regional climate model (RCM) HIRHAM. The experiments were forced at the lateral boundary by large-scale atmospheric conditions from transient climate change scenario simulations...... with HIRHAM for periods representing present-day (1961-1990) and the future (2071-2100) in the two scenarios. We find that due to a much better representation of the surface topography in the RCM, the geographical distribution of present-day accumulation rates simulated by the RCM represents a substantial...... improvement compared to the driving OAGCM. Estimates of the regional net balance are also better represented by the RCM. In the future climate the net balance for the Greenland Ice Sheet is reduced in all the simulation, but discrepancies between the amounts when based on ECHAM4/OPYC3 and HIRHAM are found...

  16. NetBeans GUI Builder

    OpenAIRE

    Pusiankova, Tatsiana

    2009-01-01

    This work aims at making readers familiar with the powerful tool NetBeans IDE GUI Builder and helping them make their first steps to creation of their own graphical user interface in the Java programming language. The work includes theoretical description of NetBeans IDE GUI Builder, its most important characteristics and peculiarities and also a set of practical instructions that will help readers in creation of their first GUI. The readers will be introduced to the environment of this tool ...

  17. Multiflavor string-net models

    Science.gov (United States)

    Lin, Chien-Hung

    2017-05-01

    We generalize the string-net construction to multiple flavors of strings, each of which is labeled by the elements of an Abelian group Gi. The same flavor of strings can branch, while different flavors of strings can cross one another and thus they form intersecting string nets. We systematically construct the exactly soluble lattice Hamiltonians and the ground-state wave functions for the intersecting string-net condensed phases. We analyze the braiding statistics of the low-energy quasiparticle excitations and find that our model can realize all the topological phases as the string-net model with group G =∏iGi . In this respect, our construction provides various ways of building lattice models which realize topological order G , corresponding to different partitions of G and thus different flavors of string nets. In fact, our construction concretely demonstrates the Künneth formula by constructing various lattice models with the same topological order. As an example, we construct the G =Z2×Z2×Z2 string-net model which realizes a non-Abelian topological phase by properly intersecting three copies of toric codes.

  18. Global Distribution of Net Electron Acceptance in Subseafloor Sediment

    Science.gov (United States)

    Fulfer, V. M.; Pockalny, R. A.; D'Hondt, S.

    2017-12-01

    We quantified the global distribution of net electron acceptance rates (e-/m2/year) in subseafloor sediment (>1.5 meters below seafloor [mbsf]) using (i) a modified version of the chemical-reaction-rate algorithm by Wang et al. (2008), (ii) physical properties and dissolved oxygen and sulfate data from interstitial waters of sediment cores collected by the Ocean Drilling Program, Integrated Ocean Drilling Program, International Ocean Discovery Program, and U.S. coring expeditions, and (iii) correlation of net electron acceptance rates to global oceanographic properties. Calculated net rates vary from 4.8 x 1019 e-/m2/year for slowly accumulating abyssal clay to 1.2 x 1023 e-/m2/year for regions of high sedimentation rate. Net electron acceptance rate correlates strongly with mean sedimentation rate. Where sedimentation rate is very low (e.g., 1 m/Myr), dissolved oxygen penetrates more than 70 mbsf and is the primary terminal electron acceptor. Where sedimentation rate is moderate (e.g., 3 to 60 m/Myr), dissolved sulfate penetrates as far as 700 mbsf and is the principal terminal electron acceptor. Where sedimentation rate is high (e.g., > 60 m/Myr), dissolved sulfate penetrates only meters, but is the principal terminal electron acceptor in subseafloor sediment to the depth of sulfate penetration. Because microbial metabolism continues at greater depths than the depth of sulfate penetration in fast-accumulating sediment, complete quantification of subseafloor metabolic rates will require consideration of other chemical species.

  19. Inhibition of the Nitrification Process of Activated Sludge Micro-Organism by Scrubber Water from an Industrial Flue Gas Cleaning Process

    DEFF Research Database (Denmark)

    Thomsen, Jens Peter

    2007-01-01

    the nitrogen removal. A major sewage cleaning plant in the southern part of Denmark is a recipient of industrial sewage from a major fish meal industry. Severe nitrification inhibition was observed in scrubber water from an incineration of process air, and the processes that lead to the production were stopped......The microbial transformation of ammonia to nitrate, the nitrification, is a central process in the nitrogen biogeochemical cycle. In a modern wastewater treatment plant, the nitrification process is a key process in the removal of nitrogen and inhibitory compounds in sewage can seriously affect....... In order to investigate the relation between incineration temperatures and the production of inhibitory compounds, the process air was burned at temperatures from 800°C to 1000°C. The termically affected condensate was collected and the nitrification inhibition effect of the condensate was tested using...

  20. Evaluation of Nitrification Inhibition Using Sequencing Batch Reactors and BioWin Modeling, and the Effect of Aqueous Film Forming Foam on Biological Nutrient Removal

    OpenAIRE

    Hingley, Daniel McCabe

    2011-01-01

    To evaluate continuous and sporadic nitrification inhibition at the HRSD Nansemond Wastewater Treatment Plant, which has a history of nitrification upsets, continuous sequencing batch reactors (SBRs) were operated to simulate the full-scale plant. Four reactors were operated in this study. One reactor was fed with raw influent (RWI) from the Nansemond Wastewater Treatment Plant (NP). Another was fed with NP primary clarifier influent (PCI), which includes the raw influent, as well as plant re...

  1. Current as an indicator of ammonia concentration during wastewater treatment in an integrated microbial electrolysis cell - Nitrification system

    DEFF Research Database (Denmark)

    Zhao, Nannan; Angelidaki, Irini; Zhang, Yifeng

    2018-01-01

    with synthetic ammonia-rich wastewater. A good linear relationship (R2 = 0.9419) was observed between current (0.5130–3.906 mA) and ammonia levels (0–62.1 mg NH4+-N/L). Such linear relationship was always obtained regardless of the tested external power supply or wastewater pH. The external electrochemical cell......A key challenge for ammonia monitoring during nitrogen removal process is the extra cost and toxic reagent consuming. Herein the feasibility of current generated by an integrated microbial electrolysis cell (MEC) - nitrification reactor as an indicator of initial ammonia levels (NH3/NH4......+) in wastewater was explored. In this loop system, ammonia was first oxidized to nitrate in the nitrification reactor, and then the effluent was introduced into the cathode of MEC where nitrate was reduced as electron acceptor. The correlation between current and ammonia concentration was first investigated...

  2. [Identification and Nitrogen Removal Characteristics of a Heterotrophic Nitrification-Aerobic Denitrification Strain Isolated from Marine Environment].

    Science.gov (United States)

    Sun, Qing-hua; Yu, De-shuang; Zhang, Pei-yu; Lin, Xue-zheng; Li, Jin

    2016-02-15

    A heterotrophic nitrification-aerobic denitrification strain named y5 was isolated from marine environment by traditional microbial isolation method using seawater as medium. It was identified as Klebsiella sp. based on the morphological, physiological and 16S rRNA sequence analysis. The experiment results showed that the optimal carbon resource was sodium citrate; the optimal pH was 7.0; and the optimal C/N was 17. The strain could use NH4Cl, NaNO2 and KNO3 as sole nitrogen source, and the removal efficiencies were77.07%, 64.14% and 100% after 36 hours, respectively. The removal efficiency reached 100% after 36 hours in the coexistence of NH4Cl, NaNO2 and KNO3. The results showed that the strain y5 had independent and efficient heterotrophic nitrification and aerobic denitrification activities in high salt wastewater.

  3. Green net national product for the sustainability and social welfare

    OpenAIRE

    Mohajan, Haradhan

    2010-01-01

    This paper discusses the theory of green national accounting and, emphasizes on social welfare and sustainable accounting. Weitzman provides a foundation for net national product as the stationary equivalent of a wealth maximizing path when there is a constant interest rate and no exogenous technological progress. An attempt has been taken here to make the relationship with different incomes and green net national product, under no exogenous technological progress and a constant utility disco...

  4. [Zr(NEtMe)2(guan-NEtMe)2] as a novel ALD precursor: ZrO2 film growth and mechanistic studies

    NARCIS (Netherlands)

    Blanquart, T.; Niinistö, J.; Aslam, N.; Banerjee, M.; Tomczak, Y.; Gavagnin, M.; Longo, V.; Puukilainen, E.; Wanzenboeck, H.D.; Kessels, W.M.M.; Devi, A.; Hoffmann-Eifert, S.; Ritala, M.; Leskelä, M.

    2013-01-01

    [Zr(NEtMe)2(guan-NEtMe2)2], a recently developed compound, was investigated as a novel precursor for the atomic layer deposition (ALD) of ZrO2. With water as the oxygen source, the growth rate remained constant over a wide temperature range, whereas with ozone the growth rate increased steadily with

  5. Mass distribution of free insecticide-treated nets do not interfere with continuous net distribution in Tanzania.

    Science.gov (United States)

    Eze, Ikenna C; Kramer, Karen; Msengwa, Amina; Mandike, Renata; Lengeler, Christian

    2014-05-27

    To protect the most vulnerable groups from malaria (pregnant women and infants) the Tanzanian Government introduced a subsidy (voucher) scheme in 2004, on the basis of a public-private partnership. These vouchers are provided to pregnant women at their first antenatal care visit and mothers of infants at first vaccination. The vouchers are redeemed at registered retailers for a long-lasting insecticidal net against the payment of a modest top-up price. The present work analysed a large body of data from the Tanzanian National Voucher Scheme, focusing on interactions with concurrent mass distribution campaigns of free nets. In an ecologic study involving all regions of Tanzania, voucher redemption data for the period 2007-2011, as well as data on potential determinants of voucher redemption were analysed. The four outcome variables were: pregnant woman and infant voucher redemption rates, use of treated bed nets by all household members and by under- five children. Each of the outcomes was regressed with selected determinants, using a generalized estimating equation model and accounting for regional data clustering. There was a consistent improvement in voucher redemption rates over the selected time period, with rates >80% in 2011. The major determinants of redemption rates were the top-up price paid by the voucher beneficiary, the retailer- clinic ratio, and socio-economic status. Improved redemption rates after 2009 were most likely due to reduced top-up prices (following a change in policy). Redemption rates were not affected by two major free net distribution campaigns. During this period, there was a consistent improvement in net use across all the regions, with rates of up to 75% in 2011. The key components of the National Treated Nets Programme (NATNETS) seem to work harmoniously, leading to a high level of net use in the entire population. This calls for the continuation of this effort in Tanzania and for emulation by other countries with endemic malaria.

  6. Potential for Nitrogen Fixation and Nitrification in the Granite-Hosted Subsurface at Henderson Mine, CO

    Science.gov (United States)

    Swanner, Elizabeth D.; Templeton, Alexis S.

    2011-01-01

    The existence of life in the deep terrestrial subsurface is established, yet few studies have investigated the origin of nitrogen that supports deep life. Previously, 16S rRNA gene surveys cataloged a diverse microbial community in subsurface fluids draining from boreholes 3000 feet deep at Henderson Mine, CO, USA (Sahl et al., 2008). The prior characterization of the fluid chemistry and microbial community forms the basis for the further investigation here of the source of NH4+. The reported fluid chemistry included N2, NH4+ (5–112 μM), NO2− (27–48 μM), and NO3− (17–72 μM). In this study, the correlation between low NH4+ concentrations in dominantly meteoric fluids and higher NH4+ in rock-reacted fluids is used to hypothesize that NH4+ is sourced from NH4+-bearing biotite. However, biotite samples from the host rocks and ore-body minerals were analyzed by Fourier transform infrared (FTIR) microscopy and none-contained NH4+. However, the nitrogenase-encoding gene nifH was successfully amplified from DNA of the fluid sample with high NH4+, suggesting that subsurface microbes have the capability to fix N2. If so, unregulated nitrogen fixation may account for the relatively high NH4+ concentrations in the fluids. Additionally, the amoA and nxrB genes for archaeal ammonium monooxygenase and nitrite oxidoreductase, respectively, were amplified from the high NH4+ fluid DNA, while bacterial amoA genes were not. Putative nitrifying organisms are closely related to ammonium-oxidizing Crenarchaeota and nitrite-oxidizing Nitrospira detected in other subsurface sites based upon 16S rRNA sequence analysis. Thermodynamic calculations underscore the importance of NH4+ as an energy source in a subsurface nitrification pathway. These results suggest that the subsurface microbial community at Henderson is adapted to the low nutrient and energy environment by their capability of fixing nitrogen, and that fixed nitrogen may support subsurface biomass via

  7. Nitrification inhibition by hexavalent chromium Cr(VI)--Microbial ecology, gene expression and off-gas emissions.

    Science.gov (United States)

    Kim, Young Mo; Park, Hongkeun; Chandran, Kartik

    2016-04-01

    The goal of this study was to investigate the responses in the physiology, microbial ecology and gene expression of nitrifying bacteria to imposition of and recovery from Cr(VI) loading in a lab-scale nitrification bioreactor. Exposure to Cr(VI) in the reactor strongly inhibited nitrification performance resulting in a parallel decrease in nitrate production and ammonia consumption. Cr(VI) exposure also led to an overall decrease in total bacterial concentrations in the reactor. However, the fraction of ammonia oxidizing bacteria (AOB) decreased to a greater extent than the fraction of nitrite oxidizing bacteria (NOB). In terms of functional gene expression, a rapid decrease in the transcript concentrations of amoA gene coding for ammonia oxidation in AOB was observed in response to the Cr(VI) shock. In contrast, transcript concentrations of the nxrA gene coding for nitrite oxidation in NOB were relatively unchanged compared to Cr(VI) pre-exposure levels. Therefore, Cr(VI) exposure selectively and directly inhibited activity of AOB, which indirectly resulted in substrate (nitrite) limitation to NOB. Significantly, trends in amoA expression preceded performance trends both during imposition of and recovery from inhibition. During recovery from the Cr(VI) shock, the high ammonia concentrations in the bioreactor resulted in an irreversible shift towards AOB populations, which are expected to be more competitive in high ammonia environments. An inadvertent impact during recovery was increased emission of nitrous oxide (N2O) and nitric oxide (NO), consistent with recent findings linking AOB activity and the production of these gases. Therefore, Cr(VI) exposure elicited multiple responses on the microbial ecology, gene expression and both aqueous and gaseous nitrogenous conversion in a nitrification process. A complementary interrogation of these multiple responses facilitated an understanding of both direct and indirect inhibitory impacts on nitrification. Copyright

  8. Colorectal Cancer Safety Net: Is It Catching Patients Appropriately?

    Science.gov (United States)

    Althans, Alison R; Brady, Justin T; Times, Melissa L; Keller, Deborah S; Harvey, Alexis R; Kelly, Molly E; Patel, Nilam D; Steele, Scott R

    2018-01-01

    Disparities in access to colorectal cancer care are multifactorial and are affected by socioeconomic elements. Uninsured and Medicaid patients present with advanced stage disease and have worse outcomes compared with similar privately insured patients. Safety net hospitals are a major care provider to this vulnerable population. Few studies have evaluated outcomes for safety net hospitals compared with private institutions in colorectal cancer. The purpose of this study was to compare demographics, screening rates, presentation stage, and survival rates between a safety net hospital and a tertiary care center. Comparative review of patients at 2 institutions in the same metropolitan area were conducted. The study included colorectal cancer care delivered either at 1 safety net hospital or 1 private tertiary care center in the same city from 2010 to 2016. A total of 350 patients with colorectal cancer from each hospital were evaluated. Overall survival across hospital systems was measured. The safety net hospital had significantly more uninsured and Medicaid patients (46% vs 13%; p presentation, a similar percentage of patients at each hospital presented with stage IV disease (26% vs 20%; p = 0.06). For those undergoing resection, final pathologic stage distribution was similar across groups (p = 0.10). After a comparable median follow-up period (26.6 mo for safety net hospital vs 29.2 mo for tertiary care center), log-rank test for overall survival favored the safety net hospital (p = 0.05); disease-free survival was similar between hospitals (p = 0.40). This was a retrospective review, reporting from medical charts. Our results support the value of safety net hospitals for providing quality colorectal cancer care, with survival and recurrence outcomes equivalent or improved compared with a local tertiary care center. Because safety net hospitals can provide equivalent outcomes despite socioeconomic inequalities and financial constraints, emphasis should be focused

  9. Efficacy of PermaNet® 3.0 and PermaNet® 2.0 nets against laboratory-reared and wild Anopheles gambiae sensu lato populations in northern Tanzania.

    Science.gov (United States)

    Kweka, Eliningaya J; Lyaruu, Lucile J; Mahande, Aneth M

    2017-01-18

    Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times. Both washed and unwashed PermaNet® 2.0 and PermaNet® 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto. The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet® 3.0 and PermaNet® 2.0 nets was found to be higher than after use of the washed PermaNet® 2.0 and PermaNet® 3.0 nets. Given the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.

  10. Impact of Nitrification on the Formation of N-Nitrosamines and Halogenated Disinfection Byproducts within Distribution System Storage Facilities.

    Science.gov (United States)

    Zeng, Teng; Mitch, William A

    2016-03-15

    Distribution system storage facilities are a critical, yet often overlooked, component of the urban water infrastructure. This study showed elevated concentrations of N-nitrosodimethylamine (NDMA), total N-nitrosamines (TONO), regulated trihalomethanes (THMs) and haloacetic acids (HAAs), 1,1-dichloropropanone (1,1-DCP), trichloroacetaldehyde (TCAL), haloacetonitriles (HANs), and haloacetamides (HAMs) in waters with ongoing nitrification as compared to non-nitrifying waters in storage facilities within five different chloraminated drinking water distribution systems. The concentrations of NDMA, TONO, HANs, and HAMs in the nitrifying waters further increased upon application of simulated distribution system chloramination. The addition of a nitrifying biofilm sample collected from a nitrifying facility to its non-nitrifying influent water led to increases in N-nitrosamine and halogenated DBP formation, suggesting the release of precursors from nitrifying biofilms. Periodic treatment of two nitrifying facilities with breakpoint chlorination (BPC) temporarily suppressed nitrification and reduced precursor levels for N-nitrosamines, HANs, and HAMs, as reflected by lower concentrations of these DBPs measured after re-establishment of a chloramine residual within the facilities than prior to the BPC treatment. However, BPC promoted the formation of halogenated DBPs while a free chlorine residual was maintained. Strategies that minimize application of free chlorine while preventing nitrification are needed to control DBP precursor release in storage facilities.

  11. Simultaneous nitrification, denitrification and phosphorus removal (SNDPR) in a full-scale water reclamation plant located in warm climate.

    Science.gov (United States)

    Yang, Qin; Shen, Nan; Lee, Zarraz M-P; Xu, Guangjing; Cao, Yeshi; Kwok, Beehong; Lay, Winson; Liu, Yu; Zhou, Yan

    The combination of simultaneous nitrification-denitrification (SND) with enhanced biological phosphorus removal (EBPR) provides a more efficient and economically viable option for nutrient removal from municipal wastewater compared to conventional two-step nitrification-denitrification. This study analyzed the nutrients (N and P) profiles in a full-scale municipal wastewater reclamation plant (WRP) located in the tropical region, in which more than 90% of nitrogen was removed. Interestingly, average SND efficiency in aerobic zones was found to be up to 50%, whereas phosphorus profile displayed a clear cyclic release and uptake pattern with a phosphorus removal efficiency of up to 76%. The capability of sludge to perform SND and EBPR was further confirmed through a series of batch experiments. Microbial analysis revealed the presence of Accumulibacter and Tetrasphaera phosphate accumulating organisms in the plant, while few glycogen accumulating organisms (GAO) was observed. This study showed the significant occurrence of combined SND and EBPR, known as simultaneous nitrification, denitrification and phosphorus removal (SNDPR), in the studied WRP under warm climate. The possible causes behind the observed SNDPR were also discussed.

  12. Molecular biological and isotopic biogeochemical prognoses of the nitrification-driven dynamic microbial nitrogen cycle in hadopelagic sediments.

    Science.gov (United States)

    Nunoura, Takuro; Nishizawa, Manabu; Kikuchi, Tohru; Tsubouchi, Taishi; Hirai, Miho; Koide, Osamu; Miyazaki, Junichi; Hirayama, Hisako; Koba, Keisuke; Takai, Ken

    2013-11-01

    There has been much progress in understanding the nitrogen cycle in oceanic waters including the recent identification of ammonia-oxidizing archaea and anaerobic ammonia oxidizing (anammox) bacteria, and in the comprehensive estimation in abundance and activity of these microbial populations. However, compared with the nitrogen cycle in oceanic waters, there are fewer studies concerning the oceanic benthic nitrogen cycle. To further elucidate the dynamic nitrogen cycle in deep-sea sediments, a sediment core obtained from the Ogasawara Trench at a water depth of 9760 m was analysed in this study. The profiles obtained for the pore-water chemistry, and nitrogen and oxygen stable isotopic compositions of pore-water nitrate in the hadopelagic sediments could not be explained by the depth segregation of nitrifiers and nitrate reducers, suggesting the co-occurrence of nitrification and nitrate reduction in the shallowest nitrate reduction zone. The abundance of SSU rRNA and functional genes related to nitrification and denitrification are consistent with the co-occurrence of nitrification and nitrate reduction observed in the geochemical analyses. This study presents the first example of cooperation between aerobic and anaerobic nitrogen metabolism in the deep-sea sedimentary environments. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  13. Photosynthetic pigments content, photosynthesis rate and chloroplast structure in young plants of Mikania laevigata Schultz Bip. ex Baker grown under colored netsTeores de pigmentos fotossintéticos, taxa de fotossíntese e estrutura de cloroplastos de plantas jovens de Mikania laevigata Schultz Bip. ex Baker cultivadas sob malhas coloridas

    Directory of Open Access Journals (Sweden)

    Anacleto Ranulfo dos Santos

    2011-12-01

    Full Text Available Guaco (Mikania laevigata is a medicinal plant used to treat fever, rheumatism, flu and respiratory tract diseases. Understanding the physiology of this species and its responses to environmental conditions has become necessary to improving the cultivation methods. In this context, this work aimed to access the effects of shading by using colored nets in on photosynthetic pigment concentration, photosynthetic rate and ultrastructure of chloroplasts of Mikania laevigata. The plants were cultivated during four months under nets with 50% shading in blue, red and gray color nets and under full sunlight (0%. The plants grown under full sunlight had decreased contents of a and b chlorophyll, and of carotenoids, while those grown under blue nets shown higher concentrations of a and b chlorophyll. The lowest density of chloroplasts was found in plants cultivated under full sunlight. Elongated chloroplasts were noticed in treatments with 50% shading. Regarding the potential rate of photosynthesis no significant change was observed among the plants grown under red, blue and gray nets, which leads to the conclusion that the spectrum transmitted by different coloured nets did not affect guaco photosynthetic apparatus.O guaco (Mikania laevigata é uma planta medicinal, usada para o tratamento de febre, reumatismo, gripe e doenças do trato respiratório. O entendimento do comportamento fisiológico dessa espécie e as suas respostas às condições do ambiente tornam-se necessários ao aperfeiçoamento dos métodos de cultivo. Nesse contexto, o presente trabalho teve como objetivo avaliar os efeitos do sombreamento com uso de malhas coloridas na concentração de pigmentos fotossintéticos, na taxa de fotossíntese e na ultra-estrutura de cloroplastos de plantas de Mikania laevigata. As plantas foram cultivadas por quatro meses sob malhas de 50% de sombreamento nas cores azul, vermelha e cinza e a pleno sol (0%. As plantas mantidas a pleno sol tiveram os

  14. Plant water stress effects on the net dispersal rate of the insect vector Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) and movement of its egg parasitoid, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae)

    Science.gov (United States)

    Homalodisca vitripennis, one of the main vectors of Xylella fastidiosa, is associated with citrus plantings in California, USA. Infested citrus orchards act as a source of vectors to adjacent vineyards where X. fastidiosa causes Pierce’s disease (PD). An analysis of the pattern and rate of movement ...

  15. Setting a price for solar net-metering in California

    OpenAIRE

    Knezevic, Laura M

    2014-01-01

    Net-metering programs are an effective policy tool for promoting investment in solar photovoltaics, yet little attention has been paid to the rate at which excess energy generation is credited until recently. Like most States, California customers who participate in net-metering receive a credit for excess generation at the current retail rate for electricity. This buy-back rate does not take into account the value of solar energy to the utility or the costs to the customer of purchasing an...

  16. Lead toxicity thresholds in 17 Chinese soils based on substrate-induced nitrification assay.

    Science.gov (United States)

    Li, Ji; Huang, Yizong; Hu, Ying; Jin, Shulan; Bao, Qiongli; Wang, Fei; Xiang, Meng; Xie, Huiting

    2016-06-01

    The influence of soil properties on toxicity threshold values for Pb toward soil microbial processes is poorly recognized. The impact of leaching on the Pb threshold has not been assessed systematically. Lead toxicity was screened in 17 Chinese soils using a substrate-induced nitrification (SIN) assay under both leached and unleached conditions. The effective concentration of added Pb causing 50% inhibition (EC50) ranged from 185 to >2515mg/kg soil for leached soil and 130 to >2490mg/kg soil for unleached soil. These results represented >13- and >19-fold variations among leached and unleached soils, respectively. Leaching significantly reduced Pb toxicity for 70% of both alkaline and acidic soils tested, with an average leaching factor of 3.0. Soil pH and CEC were the two most useful predictors of Pb toxicity in soils, explaining over 90% of variance in the unleached EC50 value. The relationships established in the present study predicted Pb toxicity within a factor of two of measured values. These relationships between Pb toxicity and soil properties could be used to establish site-specific guidance on Pb toxicity thresholds. Copyright © 2016. Published by Elsevier B.V.

  17. Rapid Startup and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin; Vega, Leticia

    2014-01-01

    The Membrane Aerated Bioreactor (MABR) is an attached-growth biological system for simultaneous nitrification and denitrification. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal. Implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to two weeks and that the surface area to volume ratio baseline used in the Alternative Water Processor (AWP) test was higher than what was needed to remove the organic carbon and ammonium from the system.

  18. Evaluating the Contributions of Atmospheric Deposition of Carbon and Other Nutrients to Nitrification in Alpine Environments

    Science.gov (United States)

    Oldani, K. M.; Mladenov, N.; Williams, M. W.

    2013-12-01

    The Colorado Front Range of the Rocky Mountains contains undeveloped, barren soils, yet in this environment there is strong evidence for a microbial role in increased nitrogen (N) export. Barren soils in alpine environments are severely carbon-limited, which is the main energy source for microbial activity and sustenance of life. It has been shown that atmospheric deposition can contain high amounts of organic carbon (C). Atmospheric pollutants, dust events, and biological aerosols, such as bacteria, may be important contributors to the atmospheric organic C load. In this stage of the research we evaluated seasonal trends in the chemical composition and optical spectroscopic (fluorescence and UV-vis absorbance) signatures of snow, wet deposition, and dry deposition in an alpine environment at Niwot Ridge in the Rocky Mountains of Colorado to obtain a better understanding of the sources and chemical character of atmospheric deposition. Our results reveal a positive trend between dissolved organic carbon concentrations and calcium, nitrate and sulfate concentrations in wet and dry deposition, which may be derived from such sources as dust and urban air pollution. We also observed the presence of seasonally-variable fluorescent components that may be attributed to fluorescent pigments in bacteria. These results are relevant because atmospheric inputs of carbon and other nutrients may influence nitrification in barren, alpine soils and, ultimately, the export of nitrate to alpine watersheds.

  19. Side Effects of Nitrification Inhibitors on Non Target Microbial Processes in Soils

    Directory of Open Access Journals (Sweden)

    Johannes Carl Gottlieb Ottow

    2011-01-01

    Full Text Available Agricultural chemicals have been used extensively in modern agriculture and toxicological studies suggest a great potential for inducing undesirable effects on non target organisms. A model experiment was conducted in order to determine side effects of three nitrification inhibitors (NIs, 3,4dimethylpyrazolephosphate = DMPP, 4-Chlor-methylpyrazole phosphate = ClMPP and dicyandiamide = DCD on non target microbial processes in soils. Side effects and dose response curve of three NIs were quantified under laboratory conditions using silty clay, loam and a sandy soils. Dehydrogenase, dimethylsulfoxide reductase as well as nitrogenase activity (NA and potential denitrification capacity were measured as common and specific non target microbial processes. The influence of 5-1000 times the base concentration, dose response curves were examined, and no observable effect level = NOEL, as well as effective dose ED10 and ED50 (10% and 50% inhibition were calculated. The NOEL for microbial non target processes were about 30–70 times higher than base concentration in all investigated soils. The potential denitrification capacity revealed to be the most sensitive parameter. ClMPP exhibited the strongest influence on the non target microbial processes in the three soils. The NOEL, ED10 and ED50 values were higher in clay than in loamy or sandy soil. The NIs was the most effective in sandy soils.

  20. MATT: Multi Agents Testing Tool Based Nets within Nets

    Directory of Open Access Journals (Sweden)

    Sara Kerraoui

    2016-12-01

    As part of this effort, we propose a model based testing approach for multi agent systems based on such a model called Reference net, where a tool, which aims to providing a uniform and automated approach is developed. The feasibility and the advantage of the proposed approach are shown through a short case study.

  1. Proposal to support the 4th international conference on nitrification and related processes (ICoN4)

    International Nuclear Information System (INIS)

    Klotz, Martin Gunter

    2016-01-01

    The 4th International Conference on Nitrification and Related Processes (ICoN4) commencing between June 27 and July 1, 2015, at the University of Alberta in Edmonton, Alberta, Canada brings together an international collection of academic, government, and private sector researchers of the global biogeochemical nitrogen cycle to share their scientific discoveries, innovations and pertinent societal impacts. The classical understanding of “nitrification” describes the two-step transformation of ammonium to nitrite and nitrite to nitrate; however, we now know from the analysis genome sequences, the application of ‘omics technologies, microbial ecology, biogeochemistry, and microbial physiology that the transformation of ammonium is not performed by a few particular groups of microorganisms nor is it confined to oxic environments. Past ICoN meetings have explored the interconnections between ammonium- and nitrite-consuming processes in all ecosystems, the emission of greenhouse gases by these processes and their control, and the intersection between intermediates of the nitrification process and other elemental cycles; this has generated tremendous progress in our understanding of the global nitrogen cycle and it has generated excitement in the next generation of N cycle researchers. Nitrification research has a long-standing connection to the Community Science Program of the DOE. Between 1999 and 2001, the JGI generated the first genome sequence of an ammonia-oxidizing bacterium, Nitrosomonas europaea ATCC 19718, and it has subsequently sequenced, or is in the process of sequencing over 50 additional genomes from ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing archaea. Autotrophic ammonia- and nitrite-transforming microorganisms play also a critical role in carbon cycling and sequestration in nearly all ecosystems. Not only do they control the concentration and speciation of biologically available N to plants and other

  2. Proposal to support the 4th international conference on nitrification and related processes (ICoN4)

    Energy Technology Data Exchange (ETDEWEB)

    Klotz, Martin Gunter [Univ. of North Carolina, Charlotte, NC (United States)

    2016-11-04

    The 4th International Conference on Nitrification and Related Processes (ICoN4) commencing between June 27 and July 1, 2015, at the University of Alberta in Edmonton, Alberta, Canada brings together an international collection of academic, government, and private sector researchers of the global biogeochemical nitrogen cycle to share their scientific discoveries, innovations and pertinent societal impacts. The classical understanding of “nitrification” describes the two-step transformation of ammonium to nitrite and nitrite to nitrate; however, we now know from the analysis genome sequences, the application of ‘omics technologies, microbial ecology, biogeochemistry, and microbial physiology that the transformation of ammonium is not performed by a few particular groups of microorganisms nor is it confined to oxic environments. Past ICoN meetings have explored the interconnections between ammonium- and nitrite-consuming processes in all ecosystems, the emission of greenhouse gases by these processes and their control, and the intersection between intermediates of the nitrification process and other elemental cycles; this has generated tremendous progress in our understanding of the global nitrogen cycle and it has generated excitement in the next generation of N cycle researchers. Nitrification research has a long-standing connection to the Community Science Program of the DOE. Between 1999 and 2001, the JGI generated the first genome sequence of an ammonia-oxidizing bacterium, Nitrosomonas europaea ATCC 19718, and it has subsequently sequenced, or is in the process of sequencing over 50 additional genomes from ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing archaea. Autotrophic ammonia- and nitrite-transforming microorganisms play also a critical role in carbon cycling and sequestration in nearly all ecosystems. Not only do they control the concentration and speciation of biologically available N to plants and other

  3. Implementing NetScaler VPX

    CERN Document Server

    Sandbu, Marius

    2014-01-01

    An easy-to-follow guide with detailed step-by step-instructions on how to implement the different key components in NetScaler, with real-world examples and sample scenarios.If you are a Citrix or network administrator who needs to implement NetScaler in your virtual environment to gain an insight on its functionality, this book is ideal for you. A basic understanding of networking and familiarity with some of the different Citrix products such as XenApp or XenDesktop is a prerequisite.

  4. Net4Care PHMR Library

    DEFF Research Database (Denmark)

    2014-01-01

    The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the SimpleClinicalDocument......The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the Simple...

  5. Net present value approaches for drug discovery.

    Science.gov (United States)

    Svennebring, Andreas M; Wikberg, Jarl Es

    2013-12-01

    Three dedicated approaches to the calculation of the risk-adjusted net present value (rNPV) in drug discovery projects under different assumptions are suggested. The probability of finding a candidate drug suitable for clinical development and the time to the initiation of the clinical development is assumed to be flexible in contrast to the previously used models. The rNPV of the post-discovery cash flows is calculated as the probability weighted average of the rNPV at each potential time of initiation of clinical development. Practical considerations how to set probability rates, in particular during the initiation and termination of a project is discussed.

  6. Coloured Petri Nets and the Invariant Method

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1981-01-01

    processes to be described by a common subnet, without losing the ability to distinguish between them. Our generalization, called coloured Petri nets, is heavily influenced by predicate transition-nets introduced by H.J. Genrich and K. Lautenbach. Moreover our paper shows how the invariant-method, introduced...... for Petri nets by K. Lautenbach, can be generalized to coloured Petri nets....

  7. Using Pure Cultures to Define the Site Preference of Nitrous Oxide Produced by Microbial Nitrification and Denitrification

    Science.gov (United States)

    Sutka, R. L.; Breznak, J. A.; Ostrom, N. E.; Ostrom, P. H.; Gandhi, H.

    2004-12-01

    Defining the site preference of nitrous oxide (N2O) produced in pure culture studies is crucial to interpreting field data. We have previously demonstrated that the intramolecular distribution of nitrogen isotopes (isotopomers) can be used to differentiate N2O produced by nitrifier denitrification and nitrification in cultures of Nitrosomonas europaea. Here, we have expanded on our initial results and evaluated the isotopomeric composition of N2O produced during nitrification and nitrifier denitrification with cultures of Nitrosospira multiformis. In addition, we have analyzed N2O produced during methanotrophic nitrification, denitrification, and fungal denitrification. To evaluate N2O production during nitrification and nitrifier denitrification, we compared the site preference of N2O formed as a result of nitrite reduction and hydroxylamine oxidation with Nitrosomonas europaea and Nitrosospira multiformis. The average site preference of N2O produced by hydroxylamine oxidation was similar for Nitrosomonas europaea (33.0 ± 3.5 ‰ ) and Nitrosospira multiformis (33.1 ± 4.2 ‰ ). Nitrous oxide produced by nitrifier-denitrification by Nitrosomonas europaea and Nitrosospira multiformis had a similar site preference of - 1.4 ± 4.4 ‰ and - 1.1 ± 2.6 ‰ respectively. The results indicate that it is possible to differentiate between N2O produced by nitrite reduction and hydroxylamine oxidation by ammonia oxidizing bacteria. Methanotrophic nitrification was evaluated by analyzing the N2O produced during hydroxylamine oxidation in concentrated cell suspensions of two methane oxidizing bacteria. The site preference of N2O produced by the two methane oxidizers, Methylococcus capsulatus Bath and Methylosinus trichosporium was 31.8 ± 4.7 ‰ and 33.0 ± 4.5 ‰ respectively. The results indicate that a site preference of 33 ‰ is applicable for nitrification regardless of whether a methane oxidizer or ammonia oxidizer is involved in the reaction. To determine the site

  8. High success rates of sedation-free brain MRI scanning in young children using simple subject preparation protocols with and without a commercial mock scanner–the Diabetes Research in Children Network (DirecNet) experience

    Science.gov (United States)

    Barnea-Goraly, Naama; Weinzimer, Stuart A.; Mauras, Nelly; Beck, Roy W.; Marzelli, Matt J.; Mazaika, Paul K.; Aye, Tandy; White, Neil H.; Tsalikian, Eva; Fox, Larry; Kollman, Craig; Cheng, Peiyao; Reiss, Allan L.

    2013-01-01

    Background The ability to lie still in an MRI scanner is essential for obtaining usable image data. To reduce motion, young children are often sedated, adding significant cost and risk. Objective We assessed the feasibility of using a simple and affordable behavioral desensitization program to yield high-quality brain MRI scans in sedation-free children. Materials and methods 222 children (4–9.9 years), 147 with type 1 diabetes and 75 age-matched non-diabetic controls, participated in a multi-site study focused on effects of type 1 diabetes on the developing brain. T1-weighted and diffusion-weighted imaging (DWI) MRI scans were performed. All children underwent behavioral training and practice MRI sessions using either a commercial MRI simulator or an inexpensive mock scanner consisting of a toy tunnel, vibrating mat, and video player to simulate the sounds and feel of the MRI scanner. Results 205 children (92.3%), mean age 7±1.7 years had high-quality T1-W scans and 174 (78.4%) had high-quality diffusion-weighted scans after the first scan session. With a second scan session, success rates were 100% and 92.5% for T1-and diffusion-weighted scans, respectively. Success rates did not differ between children with type 1 diabetes and children without diabetes, or between centers using a commercial MRI scan simulator and those using the inexpensive mock scanner. Conclusion Behavioral training can lead to a high success rate for obtaining high-quality T1-and diffusion-weighted brain images from a young population without sedation. PMID:24096802

  9. High success rates of sedation-free brain MRI scanning in young children using simple subject preparation protocols with and without a commercial mock scanner-the Diabetes Research in Children Network (DirecNet) experience

    International Nuclear Information System (INIS)

    Barnea-Goraly, Naama; Marzelli, Matt J.; Mazaika, Paul K.; Weinzimer, Stuart A.; Ruedy, Katrina J.; Beck, Roy W.; Kollman, Craig; Cheng, Peiyao; Mauras, Nelly; Fox, Larry; Aye, Tandy; White, Neil H.; Tsalikian, Eva; Reiss, Allan L.

    2014-01-01

    The ability to lie still in an MRI scanner is essential for obtaining usable image data. To reduce motion, young children are often sedated, adding significant cost and risk. We assessed the feasibility of using a simple and affordable behavioral desensitization program to yield high-quality brain MRI scans in sedation-free children. 222 children (4-9.9 years), 147 with type 1 diabetes and 75 age-matched non-diabetic controls, participated in a multi-site study focused on effects of type 1 diabetes on the developing brain. T1-weighted and diffusion-weighted imaging (DWI) MRI scans were performed. All children underwent behavioral training and practice MRI sessions using either a commercial MRI simulator or an inexpensive mock scanner consisting of a toy tunnel, vibrating mat, and video player to simulate the sounds and feel of the MRI scanner. 205 children (92.3%), mean age 7 ± 1.7 years had high-quality T1-W scans and 174 (78.4%) had high-quality diffusion-weighted scans after the first scan session. With a second scan session, success rates were 100% and 92.5% for T1-and diffusion-weighted scans, respectively. Success rates did not differ between children with type 1 diabetes and children without diabetes, or between centers using a commercial MRI scan simulator and those using the inexpensive mock scanner. Behavioral training can lead to a high success rate for obtaining high-quality T1-and diffusion-weighted brain images from a young population without sedation. (orig.)

  10. High success rates of sedation-free brain MRI scanning in young children using simple subject preparation protocols with and without a commercial mock scanner-the Diabetes Research in Children Network (DirecNet) experience

    Energy Technology Data Exchange (ETDEWEB)

    Barnea-Goraly, Naama; Marzelli, Matt J.; Mazaika, Paul K. [Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford, CA (United States); Weinzimer, Stuart A. [Yale University, Pediatric Endocrinology, New Haven, CT (United States); Ruedy, Katrina J.; Beck, Roy W.; Kollman, Craig; Cheng, Peiyao [Jaeb Center for Health Research, Tampa, FL (United States); Mauras, Nelly; Fox, Larry [Nemours Children' s Clinic, Pediatric Endocrinology, Jacksonville, FL (United States); Aye, Tandy [Stanford University, Department of Pediatrics, Stanford, CA (United States); White, Neil H. [Washington University in St. Louis, Department of Pediatrics, St. Louis, MO (United States); Tsalikian, Eva [University of Iowa, Pediatric Endocrinology, Iowa City, IA (United States); Reiss, Allan L. [Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford, CA (United States); Stanford University, Department of Pediatrics, Stanford, CA (United States); Stanford University, Department of Radiology, Diabetes Research in Children Network (DirecNet), Stanford, CA (United States); Collaboration: on behalf of the Diabetes Research in Children Network (DirecNet)

    2014-02-15

    The ability to lie still in an MRI scanner is essential for obtaining usable image data. To reduce motion, young children are often sedated, adding significant cost and risk. We assessed the feasibility of using a simple and affordable behavioral desensitization program to yield high-quality brain MRI scans in sedation-free children. 222 children (4-9.9 years), 147 with type 1 diabetes and 75 age-matched non-diabetic controls, participated in a multi-site study focused on effects of type 1 diabetes on the developing brain. T1-weighted and diffusion-weighted imaging (DWI) MRI scans were performed. All children underwent behavioral training and practice MRI sessions using either a commercial MRI simulator or an inexpensive mock scanner consisting of a toy tunnel, vibrating mat, and video player to simulate the sounds and feel of the MRI scanner. 205 children (92.3%), mean age 7 ± 1.7 years had high-quality T1-W scans and 174 (78.4%) had high-quality diffusion-weighted scans after the first scan session. With a second scan session, success rates were 100% and 92.5% for T1-and diffusion-weighted scans, respectively. Success rates did not differ between children with type 1 diabetes and children without diabetes, or between centers using a commercial MRI scan simulator and those using the inexpensive mock scanner. Behavioral training can lead to a high success rate for obtaining high-quality T1-and diffusion-weighted brain images from a young population without sedation. (orig.)

  11. Household economic modelsof gill net fishermen at Madura strait

    Science.gov (United States)

    Primyastanto, M.

    2018-04-01

    The purposes of this research was to analyze household economic models of gill net fishermen at Madura strait. 30 families of gillnet fishermenwere used for purposive sampling. Data analysis used descriptive qualitative and quantitative (regression analysis). Quantitative descriptive analysis was used to analyze research and compare to factors that affecting household economic models of gill net fishermen family. Research results showed tha thousehold economic models of gill net fishermen at Madura strait was production value level or fishermen revenue at sea was strongly influenced byp roduction asset production, education level, fuel, and work flow. Work flow rate of fishermen families affected by asset production, non fisheries workflow and number of male workforce. Non fishing income level was strongly influenced by non-fishery business assets, number of family members owned andnon-fishing work flow. Spending levels of gill net fishermen at Madura strait was affected by fishing income, non-fishing income, fishermen wife education and fishermen family members.

  12. Nitrogen cycling in a deep ocean margin sediment (Sagami Bay, Japan)

    DEFF Research Database (Denmark)

    Glud, Ronnie N.; Thamdrup, Bo; Stahl, Henrik

    2009-01-01

    variable NO3- penetration depths, NO3- consumption rates, and nitrification. On average the turnover time of the pore-water NO3- pool was similar to 0.2 d. Net release of NH4+ during mineralization (0.95 mmol m(-2) d(-1)) sustained a net efflux of ammonia (53%), nitrification (24%), and anammox activity...

  13. D.NET case study

    International Development Research Centre (IDRC) Digital Library (Canada)

    lremy

    The mission was defined to build, “A society where information and ... innovative ideas and projects around different themes (using ICT), and piloting them to test .... like D.Net with several projects that had moved beyond their pilot phase.

  14. Petri Nets in Cryptographic Protocols

    DEFF Research Database (Denmark)

    Crazzolara, Federico; Winskel, Glynn

    2001-01-01

    A process language for security protocols is presented together with a semantics in terms of sets of events. The denotation of process is a set of events, and as each event specifies a set of pre and postconditions, this denotation can be viewed as a Petri net. By means of an example we illustrate...

  15. Complexity metrics for workflow nets

    NARCIS (Netherlands)

    Lassen, K.B.; Aalst, van der W.M.P.

    2009-01-01

    Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc., are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system

  16. Reference Guide Microsoft.NET

    NARCIS (Netherlands)

    Zee M van der; Verspaij GJ; Rosbergen S; IMP; NMD

    2003-01-01

    Met behulp van het rapport kunnen ontwikkelaars, beheerders en betrokken managers bij ICT projecten meer inzicht krijgen in de .NET technologie en een goede keuze maken in de inzetbaarheid van deze technologie. Het rapport geeft de bevindingen en conclusies van een verkennende studie naar het

  17. Complexity Metrics for Workflow Nets

    DEFF Research Database (Denmark)

    Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.

    2009-01-01

    Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc.\\ are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system...

  18. Communicating with the Net Generation

    Science.gov (United States)

    2011-03-11

    resource investment is necessary to sustain a high quality all-volunteer force. 9 Leadership Technique for the Net Generation Army Regulation 600...Generations at Work, Millenials at Work, http://www.generationsatwork. com /articles_millennials_at_work.php (accessed November 21, 2010). 31 Thomas

  19. Net Neutrality in the Netherlands

    NARCIS (Netherlands)

    van Eijk, N.

    2014-01-01

    The Netherlands is among the first countries that have put specific net neutrality standards in place. The decision to implement specific regulation was influenced by at least three factors. The first was the prevailing social and academic debate, partly due to developments in the United States. The

  20. Surgery for GEP-NETs

    DEFF Research Database (Denmark)

    Knigge, Ulrich; Hansen, Carsten Palnæs

    2012-01-01

    Surgery is the only treatment that may cure the patient with gastroentero-pancreatic (GEP) neuroendocrine tumours (NET) and neuroendocrine carcinomas (NEC) and should always be considered as first line treatment if R0/R1 resection can be achieved. The surgical and interventional procedures for GEP...

  1. Net4Care PHMR Tutorial

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak

    Goal To demonstrate how to use the Net4Care PHMR builder module to a) Create a SimpleClinicalDocument instance and populate it with relevant administrative and medical information to form a tele medical report of a set of measurements, b) Use the provided DanishPHMRBuilder to generate a correctly...

  2. Business Profile of Boat Lift Net and Stationary Lift Net Fishing Gear in Morodemak Waters Central Java

    Science.gov (United States)

    Hapsari, Trisnani D.; Jayanto, Bogi B.; Fitri, Aristi D. P.; Triarso, I.

    2018-02-01

    Lift net is one of the fishing gears that is used widely in the Morodemak coastal fishing port (PPP) for catching pelagic fish. The yield of fish captured by these fishing gear has high economic value, such as fish belt (Trichiurus sp), squids (Loligo sp) and anchovies (Stelophorus sp). The aims of this research were to determine the technical aspects of boat lift net and stationary lift net fishing gear in Morodemak Waters Demak Regency; to find out the financial aspect of those fishing gears and to analyze the financial feasibility by counting PP, NPV, IRR, and B/C ratio criteria. This research used case study method with descriptive analysis. The sampling method was purposive sampling with 22 fishermen as respondents. The result of the research showed that the average of boat lift net acceptance was Rp 388,580,000. The financial analysis of fisheries boat lift net with the result of NPV Rp 836,149,272, PP 2.44 years, IRR value 54%, and B/C ratio 1.73. The average of stationary lift net acceptance was Rp 27,750,000. The financial analysis lift net with the result of NPV Rp 37,937,601; PP 1.96 years, IRR value 86%, and B/C ratio 1.32. This research had a positive NPV value, B/C ratio >1, and IRR > discount rate (12 %). This study concluded that the fishery business of boat lift net and stationary lift net in Morodemak coastal fishing port (PPP) was worth running.

  3. Effect of Free Ammonia, Free Nitrous Acid, and Alkalinity on the Partial Nitrification of Pretreated Pig Slurry, Using an Alternating Oxic/Anoxic SBR

    Directory of Open Access Journals (Sweden)

    Marisol Belmonte

    2017-01-01

    Full Text Available The effect of free ammonia (NH3 or FA, free nitrous acid (HNO2 or FNA, and total alkalinity (TA on the performance of a partial nitrification (PN sequencing batch reactor (SBR treating anaerobically pretreated pig slurry was studied. The SBR was operated under alternating oxic/anoxic (O/A conditions and was fed during anoxic phases. This strategy allowed using organic matter to partially remove nitrite (NO2- and nitrate (NO3- generated during oxic phases. The desired NH4+ to NO2- ratio of 1.3 g N/g N was obtained when an Ammonium Loading Rate (ALR of 0.09 g NH4+-N/L·d was applied. The system was operated at a solid retention time (SRT of 15–20 d and dissolved oxygen (DO levels higher than 3 mg O2/L during the whole operational period. PN mainly occurred caused by the inhibitory effect of FNA on nitrite oxidizing bacteria (NOB. Once HNO2 concentration was negligible, NH4+ was fully oxidized to NO3- in spite of the presence of FA. The use of biomass acclimated to ammonium as inoculum avoided a possible effect of FA on NOB activity.

  4. .net

    Directory of Open Access Journals (Sweden)

    Le Comité de Rédaction d' EspacesTemps.net

    2002-06-01

    Full Text Available EspacesTemps lance aujourd'hui deux objets différents : un site internet et, sur ce site, Le Journal . Il s'agit donc de bien plus, et, au fond, de tout autre chose qu'un simple outil de communication destiné à informer nos lecteurs de nos parutions. Ce n'est pas non plus la « mise en ligne » de nos numéros-papier. L'internet nous donne au contraire l'occasion de réaliser, dans de meilleures conditions, ce que nous avons tenté de faire depuis quelques ...

  5. Caught in the Net: Perineuronal Nets and Addiction

    Directory of Open Access Journals (Sweden)

    Megan Slaker

    2016-01-01

    Full Text Available Exposure to drugs of abuse induces plasticity in the brain and creates persistent drug-related memories. These changes in plasticity and persistent drug memories are believed to produce aberrant motivation and reinforcement contributing to addiction. Most studies have explored the effect drugs of abuse have on pre- and postsynaptic cells and astrocytes; however, more recently, attention has shifted to explore the effect these drugs have on the extracellular matrix (ECM. Within the ECM are unique structures arranged in a net-like manner, surrounding a subset of neurons called perineuronal nets (PNNs. This review focuses on drug-induced changes in PNNs, the molecules that regulate PNNs, and the expression of PNNs within brain circuitry mediating motivation, reward, and reinforcement as it pertains to addiction.

  6. Army Net Zero Prove Out. Net Zero Energy Best Practices

    Science.gov (United States)

    2014-11-18

    recovery and cogeneration opportunities, offsetting the remaining demand with the production of renewable energy from onsite sources so that the Net...implementing energy recovery and cogeneration opportunities, and then offsetting the remaining demand with the production of renewable energy from on-site...they impact overall energy performance. The use of energy modeling in the design stage provides insights that can contribute to more effective design

  7. Net alkalinity and net acidity 2: Practical considerations

    Science.gov (United States)

    Kirby, C.S.; Cravotta, C.A.

    2005-01-01

    The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples. Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5-4) or near neutral (pH 6-7); ??? 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6. The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze. The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= -net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH mine drainage treatment can lead to systems with insufficient Alkalinity to neutralize metal and H+ acidity and is not recommended. The use of net alkalinity = -Hot Acidity titration is recommended for the planning of mine drainage treatment. The use of net alkalinity = (Alkalinitymeasured - Aciditycalculated) is recommended with some cautions

  8. CLIMATIC FORECASTING OF NET INFILTRATION AT YUCCA MOUNTAIN, USING ANALOGUE METEOROLOGICAL DATA

    International Nuclear Information System (INIS)

    B. Faybishenko

    2005-01-01

    Net infiltration is a key hydrologic parameter that controls the rate of deep percolation through the unsaturated zone, the groundwater recharge, radionuclide transport, and seepage into the underground tunnels. Because net infiltration is largely affected by climatic conditions, future changes in climatic conditions will potentially alter net infiltration. The objectives of this presentation are to: (1) Present a conceptual model and a semi-empirical approach for regional, climatic forecasting of net infiltration, based on the precipitation and temperature data from analogue meteorological stations, and (2) Demonstrate the results of forecasting net infiltration for future climates--interglacial, monsoon and glacial--over the Yucca Mountain region for the period of 500,000 years. Calculations of the net infiltration were performed using a modified Budyko's water-balance model, for which potential evapotranspiration was evaluated from the temperature-based Thornthwaite formula. (Both Budyko's and Thornthwaite's formulae have been used broadly in hydrological studies.) The results of calculations were used for ranking net infiltration, along with the aridity and precipitation-effectiveness (P-E) indexes, for future climatic scenarios. Using this approach, we determined a general trend of increasing net infiltration from the present-day (interglacial) climate to monsoon, intermediate (glacial transition), and then to the glacial climate. Ranking of the aridity and P-E indexes is practically the same as that of net infiltration. The validation of the computed net infiltration rates yielded a good match with other field and modeling study results of groundwater recharge and net infiltration evaluation

  9. Partial nitrification enhances natural attenuation of nitrogen in a septic system plume.

    Science.gov (United States)

    Caschetto, M; Robertson, W; Petitta, M; Aravena, R

    2018-06-01

    Natural attenuation of nitrogen (N) was investigated in a well characterized septic system plume at a campground in Ontario, Canada. Total inorganic N (TIN) concentrations in deeper portions of the plume were about one third of the septic tank value of 40.7mgL -1 . NH 4 + and NO 3 - isotopic characterization were used to provide insight into potential attenuation processes. Concentrations of NH 4 + and NO 3 - were highly variable in the plume, but approached the septic tank TIN value in some shallow zones and exhibited δ 15 N values like the tank value of +6‰. However, isotopic enrichment (up to +24‰ for NH 4 + and +45‰ for NO 3 - ) and declining TIN concentrations in the deeper zones indicated that anaerobic ammonium oxidation contributed to the TIN attenuation. The degree of isotopic enrichment increased at lower NH 4 + concentrations and was consistent with Rayleigh-type distillation with an enrichment factor (Ɛ) of -5.1‰. Additionally, decreasing DOC values with depth and the concomitant enrichment of δ 15 N NO3 and δ 18 O NO3 , suggested that denitrification was also active. The N attenuation observed in the Killarney plume was partly due to incomplete nitrification that occurred because of the shallow water table, which varied from only 0.2-0.7m below the tile bed infiltration pipes. Moreover, some of the monitoring locations with the shallowest water table distances from the infiltration pipes, had the highest degree of TIN attenuation (70-90%) in the plume. This behavior suggests that controlling water table distance from the infiltration pipes could be a useful mechanism for enhancing N attenuation in septic system plumes. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Membrane biofouling in a wastewater nitrification reactor: Microbial succession from autotrophic colonization to heterotrophic domination.

    Science.gov (United States)

    Lu, Huijie; Xue, Zheng; Saikaly, Pascal; Nunes, Suzana P; Bluver, Ted R; Liu, Wen-Tso

    2016-01-01

    Membrane biofouling is a complex process that involves bacterial adhesion, extracellular polymeric substances (EPS) excretion and utilization, and species interactions. To obtain a better understanding of the microbial ecology of biofouling process, this study conducted rigorous, time-course analyses on the structure, EPS and microbial composition of the fouling layer developed on ultrafiltration membranes in a nitrification bioreactor. During a 14-day fouling event, three phases were determined according to the flux decline and microbial succession patterns. In Phase I (0-2 days), small sludge flocs in the bulk liquid were selectively attached on membrane surfaces, leading to the formation of similar EPS and microbial community composition as the early biofilms. Dominant populations in small flocs, e.g., Nitrosomonas, Nitrobacter, and Acinetobacter spp., were also the major initial colonizers on membranes. In Phase II (2-4 d), fouling layer structure, EPS composition, and bacterial community went through significant changes. Initial colonizers were replaced by fast-growing and metabolically versatile heterotrophs (e.g., unclassified Sphingobacteria). The declining EPS polysaccharide to protein (PS:PN) ratios could be correlated well with the increase in microbial community diversity. In Phase III (5-14 d), heterotrophs comprised over 90% of the community, whereas biofilm structure and EPS composition remained relatively stable. In all phases, AOB and NOB were constantly found within the top 40% of the fouling layer, with the maximum concentrations around 15% from the top. The overall microbial succession pattern from autotrophic colonization to heterotrophic domination implied that MBR biofouling could be alleviated by forming larger bacterial flocs in bioreactor suspension (reducing autotrophic colonization), and by designing more specific cleaning procedures targeting dominant heterotrophs during typical filtration cycles. Copyright © 2015 Elsevier Ltd. All

  11. ANALYSIS OF TRICKLE BED AND PACKED BUBBLE COLUMN BIOREACTORS FOR COMBINED CARBON OXIDATION AND NITRIFICATION

    Directory of Open Access Journals (Sweden)

    Iliuta I.

    2002-01-01

    Full Text Available Biological removal of nitrogen and carbon by combined nitrification-oxidation in gas-liquid trickle-bed reactors (TBRs and packed bubble columns (PBCs was analyzed theoretically using a transient two-dimensional model. The model describes TBR and PBC performances at steady state as well as their transient response to a pulse or step increase in inlet methanol and NH4+-nitrogen concentrations. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time-domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the piston-dispersion-exchange model was used to interpret the residence time distribution curves obtained. Gas-liquid mass transfer parameters were determined by a stationary method based on the least-squares fit of the calculated concentration profiles in gas phase to the experimental values. Analysis of steady-state performances showed that under like operating conditions, the TBR outperforms the PBC in terms of conversions. A pulse change in the inlet methanol or NH4+-nitrogen concentration causes a negligible transient change in the outlet methanol concentration and a negligible or high transient change in the outlet NH4+-nitrogen concentration. A step change in the inlet methanol concentration causes the negligible transient change in the methanol outlet concentration and a relatively important transient change in the NH4+-nitrogen outlet concentration. A step increase in the NH4+-nitrogen inlet concentration induces a drastic transient change in the NH4+-nitrogen outlet concentration but a negligible transient change in the methanol outlet concentration.

  12. Membrane biofouling in a wastewater nitrification reactor: microbial succession from autotrophic colonization to heterotrophic domination

    KAUST Repository

    Lu, Huijie

    2015-10-22

    Membrane biofouling is a complex process that involves bacterial adhesion, extracellular polymeric substances (EPS) excretion and utilization, and species interactions. To obtain a better understanding of the microbial ecology of biofouling process, this study conducted rigorous, time-course analyses on the structure, EPS and microbial composition of the fouling layer developed on ultrafiltration membranes in a nitrification bioreactor. During a 14-day fouling event, three phases were determined according to the flux decline and microbial succession patterns. In Phase I (0-2 days), small sludge flocs in the bulk liquid were selectively attached on membrane surfaces, leading to the formation of similar EPS and microbial community composition as the early biofilms. Dominant populations in small flocs, e.g., Nitrosomonas, Nitrobacter, and Acinetobacter spp., were also the major initial colonizers on membranes. In Phase II (2-4 d), fouling layer structure, EPS composition, and bacterial community went through significant changes. Initial colonizers were replaced by fast-growing and metabolically versatile heterotrophs (e.g., unclassified Sphingobacteria). The declining EPS polysaccharide to protein (PS:PN) ratios could be correlated well with the increase in microbial community diversity. In Phase III (5-14 d), heterotrophs comprised over 90% of the community, whereas biofilm structure and EPS composition remained relatively stable. In all phases, AOB and NOB were constantly found within the top 40% of the fouling layer, with the maximum concentrations around 15% from the top. The overall microbial succession pattern from autotrophic colonization to heterotrophic domination implied that MBR biofouling could be alleviated by forming larger bacterial flocs in bioreactor suspension (reducing autotrophic colonization), and by designing more specific cleaning procedures targeting dominant heterotrophs during typical filtration cycles.

  13. Net alkalinity and net acidity 1: Theoretical considerations

    International Nuclear Information System (INIS)

    Kirby, Carl S.; Cravotta, Charles A.

    2005-01-01

    Net acidity and net alkalinity are widely used, poorly defined, and commonly misunderstood parameters for the characterization of mine drainage. The authors explain theoretical expressions of 3 types of alkalinity (caustic, phenolphthalein, and total) and acidity (mineral, CO 2 , and total). Except for rarely-invoked negative alkalinity, theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined 'CO 2 -acidity' is closely related to most standard titration methods with an endpoint pH of 8.3 used for determining acidity in mine drainage, but it is unfortunately named because CO 2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/mass-action approach and employing graphs to illustrate speciation with changes in pH, the authors explore the concept of principal components and how to assign acidity contributions to aqueous species commonly present in mine drainage. Acidity is defined in mine drainage based on aqueous speciation at the sample pH and on the capacity of these species to undergo hydrolysis to pH 8.3. Application of this definition shows that the computed acidity in mgL -1 as CaCO 3 (based on pH and analytical concentrations of dissolved Fe II , Fe III , Mn, and Al in mgL -1 ):acidity calculated =50{1000(10 -pH )+[2(Fe II )+3(Fe III )]/56+2(Mn) /55+3(Al)/27}underestimates contributions from HSO 4 - and H + , but overestimates the acidity due to Fe 3+ and Al 3+ . However, these errors tend to approximately cancel each other. It is demonstrated that 'net alkalinity' is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. Further, it is shown that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: (1) alkalinity and acidity values based on aqueous speciation (2) measured alkalinity minus calculated acidity, or (3) taking the negative of the

  14. Net alkalinity and net acidity 1: Theoretical considerations

    Science.gov (United States)

    Kirby, C.S.; Cravotta, C.A.

    2005-01-01

    Net acidity and net alkalinity are widely used, poorly defined, and commonly misunderstood parameters for the characterization of mine drainage. The authors explain theoretical expressions of 3 types of alkalinity (caustic, phenolphthalein, and total) and acidity (mineral, CO2, and total). Except for rarely-invoked negative alkalinity, theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined "CO 2-acidity" is closely related to most standard titration methods with an endpoint pH of 8.3 used for determining acidity in mine drainage, but it is unfortunately named because CO2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/mass- action approach and employing graphs to illustrate speciation with changes in pH, the authors explore the concept of principal components and how to assign acidity contributions to aqueous species commonly present in mine drainage. Acidity is defined in mine drainage based on aqueous speciation at the sample pH and on the capacity of these species to undergo hydrolysis to pH 8.3. Application of this definition shows that the computed acidity in mg L -1 as CaCO3 (based on pH and analytical concentrations of dissolved FeII, FeIII, Mn, and Al in mg L -1):aciditycalculated=50{1000(10-pH)+[2(FeII)+3(FeIII)]/56+2(Mn)/ 55+3(Al)/27}underestimates contributions from HSO4- and H+, but overestimates the acidity due to Fe3+ and Al3+. However, these errors tend to approximately cancel each other. It is demonstrated that "net alkalinity" is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. Further, it is shown that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: (1) alkalinity and acidity values based on aqueous speciation, (2) measured alkalinity minus calculated acidity, or (3) taking the negative of the value obtained in a

  15. Nitrifier-induced denitrification is an important source of soil nitrous oxide and can be inhibited by a nitrification inhibitor 3,4-dimethylpyrazole phosphate.

    Science.gov (United States)

    Shi, Xiuzhen; Hu, Hang-Wei; Zhu-Barker, Xia; Hayden, Helen; Wang, Juntao; Suter, Helen; Chen, Deli; He, Ji-Zheng

    2017-12-01

    Soil ecosystem represents the largest contributor to global nitrous oxide (N 2 O) production, which is regulated by a wide variety of microbial communities in multiple biological pathways. A mechanistic understanding of these N 2 O production biological pathways in complex soil environment is essential for improving model performance and developing innovative mitigation strategies. Here, combined approaches of the 15 N- 18 O labelling technique, transcriptome analysis, and Illumina MiSeq sequencing were used to identify the relative contributions of four N 2 O pathways including nitrification, nitrifier-induced denitrification (nitrifier denitrification and nitrification-coupled denitrification) and heterotrophic denitrification in six soils (alkaline vs. acid soils). In alkaline soils, nitrification and nitrifier-induced denitrification were the dominant pathways of N 2 O production, and application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) significantly reduced the N 2 O production from these pathways; this is probably due to the observed reduction in the expression of the amoA gene in ammonia-oxidizing bacteria (AOB) in the DMPP-amended treatments. In acid soils, however, heterotrophic denitrification was the main source for N 2 O production, and was not impacted by the application of DMPP. Our results provide robust evidence that the nitrification inhibitor DMPP can inhibit the N 2 O production from nitrifier-induced denitrification, a potential significant source of N 2 O production in agricultural soils. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  16. Impact of temperature on ammonium and nitrite removal rates in RAS moving bed biofilters

    DEFF Research Database (Denmark)

    Kinyage, John Peter Hewa; Pedersen, Lars-Flemming

    2016-01-01

    The impact of temperature on bacterial processes is well known; however temperature related data on nitrification rates in aquaculture systems are fragmented and compiled from different studies. We sought to determine ammonium and nitrite removal kinetics over a temperature range from 6 to 36 °C...

  17. Les dispositifs du Net art

    OpenAIRE

    Fourmentraux, Jean-Paul

    2010-01-01

    La pratique du Net art radicalise la question du potentiel communicationnel d’un média —Internet— qui constitue tout à la fois le support technique, l’outil créatif et le dispositif social de l’œuvre. Les technologies de l’information et de la communication (TIC) placent en effet l’œuvre d’art au cœur d’une négociation socialement distribuée entre l’artiste et le public. L’article est focalisé sur cette construction collective du Net art et sur ses mises en scènes. Il montre le travail artist...

  18. Complexity Metrics for Workflow Nets

    DEFF Research Database (Denmark)

    Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.

    2009-01-01

    analysts have difficulties grasping the dynamics implied by a process model. Recent empirical studies show that people make numerous errors when modeling complex business processes, e.g., about 20 percent of the EPCs in the SAP reference model have design flaws resulting in potential deadlocks, livelocks......, etc. It seems obvious that the complexity of the model contributes to design errors and a lack of understanding. It is not easy to measure complexity, however. This paper presents three complexity metrics that have been implemented in the process analysis tool ProM. The metrics are defined...... for a subclass of Petri nets named Workflow nets, but the results can easily be applied to other languages. To demonstrate the applicability of these metrics, we have applied our approach and tool to 262 relatively complex Protos models made in the context of various student projects. This allows us to validate...

  19. dotNet som multimediaplattform

    OpenAIRE

    Johansson, Glenn

    2008-01-01

    As the speed and complexity of computers have increased so have software and the expectations of users. Software development follows a straightforward evolution where complicated tasks are made easier by better tools; this repeats itself as those tasks in turn are automated. Software mechanics that were seen as revolutionary a decade ago are seen as obvious requirements that no multimedia application can be without. dotNet is the next step in line and makes it easier and faster to build softw...

  20. Effects of combined application of organic and inorganic fertilizers plus nitrification inhibitor DMPP on nitrogen runoff loss in vegetable soils.

    Science.gov (United States)

    Yu, Qiaogang; Ma, Junwei; Zou, Ping; Lin, Hui; Sun, Wanchun; Yin, Jianzhen; Fu, Jianrong

    2015-01-01

    The application of nitrogen fertilizers leads to various ecological problems such as large amounts of nitrogen runoff loss causing water body eutrophication. The proposal that nitrification inhibitors could be used as nitrogen runoff loss retardants has been suggested in many countries. In this study, simulated artificial rainfall was used to illustrate the effect of the nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen loss from vegetable fields under combined organic and inorganic nitrogen fertilizer application. The results showed that during the three-time simulated artificial rainfall period, the ammonium nitrogen content in the surface runoff water collected from the DMPP application treatment increased by 1.05, 1.13, and 1.10 times compared to regular organic and inorganic combined fertilization treatment, respectively. In the organic and inorganic combined fertilization with DMPP addition treatment, the nitrate nitrogen content decreased by 38.8, 43.0, and 30.1% in the three simulated artificial rainfall runoff water, respectively. Besides, the nitrite nitrogen content decreased by 95.4, 96.7, and 94.1% in the three-time simulated artificial rainfall runoff water, respectively. A robust decline in the nitrate and nitrite nitrogen surface runoff loss could be observed in the treatments after the DMPP addition. The nitrite nitrogen in DMPP addition treatment exhibited a significant low level, which is near to the no fertilizer application treatment. Compared to only organic and inorganic combined fertilizer treatment, the total inorganic nitrogen runoff loss declined by 22.0 to 45.3% in the organic and inorganic combined fertilizers with DMPP addition treatment. Therefore, DMPP could be used as an effective nitrification inhibitor to control the soil ammonium oxidation in agriculture and decline the nitrogen runoff loss, minimizing the nitrogen transformation risk to the water body and being beneficial for the ecological environment.

  1. NET model coil test possibilities

    International Nuclear Information System (INIS)

    Erb, J.; Gruenhagen, A.; Herz, W.; Jentzsch, K.; Komarek, P.; Lotz, E.; Malang, S.; Maurer, W.; Noether, G.; Ulbricht, A.; Vogt, A.; Zahn, G.; Horvath, I.; Kwasnitza, K.; Marinucci, C.; Pasztor, G.; Sborchia, C.; Weymuth, P.; Peters, A.; Roeterdink, A.

    1987-11-01

    A single full size coil for NET/INTOR represents an investment of the order of 40 MUC (Million Unit Costs). Before such an amount of money or even more for the 16 TF coils is invested as much risks as possible must be eliminated by a comprehensive development programme. In the course of such a programme a coil technology verification test should finally prove the feasibility of NET/INTOR TF coils. This study report is almost exclusively dealing with such a verification test by model coil testing. These coils will be built out of two Nb 3 Sn-conductors based on two concepts already under development and investigation. Two possible coil arrangements are discussed: A cluster facility, where two model coils out of the two Nb 3 TF-conductors are used, and the already tested LCT-coils producing a background field. A solenoid arrangement, where in addition to the two TF model coils another model coil out of a PF-conductor for the central PF-coils of NET/INTOR is used instead of LCT background coils. Technical advantages and disadvantages are worked out in order to compare and judge both facilities. Costs estimates and the time schedules broaden the base for a decision about the realisation of such a facility. (orig.) [de

  2. NET-2 Network Analysis Program

    International Nuclear Information System (INIS)

    Malmberg, A.F.

    1974-01-01

    The NET-2 Network Analysis Program is a general purpose digital computer program which solves the nonlinear time domain response and the linearized small signal frequency domain response of an arbitrary network of interconnected components. NET-2 is capable of handling a variety of components and has been applied to problems in several engineering fields, including electronic circuit design and analysis, missile flight simulation, control systems, heat flow, fluid flow, mechanical systems, structural dynamics, digital logic, communications network design, solid state device physics, fluidic systems, and nuclear vulnerability due to blast, thermal, gamma radiation, neutron damage, and EMP effects. Network components may be selected from a repertoire of built-in models or they may be constructed by the user through appropriate combinations of mathematical, empirical, and topological functions. Higher-level components may be defined by subnetworks composed of any combination of user-defined components and built-in models. The program provides a modeling capability to represent and intermix system components on many levels, e.g., from hole and electron spatial charge distributions in solid state devices through discrete and integrated electronic components to functional system blocks. NET-2 is capable of simultaneous computation in both the time and frequency domain, and has statistical and optimization capability. Network topology may be controlled as a function of the network solution. (U.S.)

  3. Nitrification and N2O production processes in soil incubations after ammonium fertilizer application at high concentrations

    Science.gov (United States)

    Deppe, Marianna; Well, Reinhard; Giesemann, Anette; Flessa, Heinz

    2016-04-01

    High concentrations of ammonium as they occur, e.g., after point-injection of ammonium fertilizer solution according to the CULTAN fertilization technique may retard nitrification. Potential advantages in comparison to conventional fertilization include a higher N efficiency of crops, reduced nitrate leaching, and lower N2O and N2 emissions. Dynamics of nitrification due to plant uptake and dilution processes, leading to decreasing ammonium concentrations in fertilizer depots, has only poorly been studied before. Furthermore, there is little information about the relative contribution of different N2O production processes under these conditions. To elucidate the process dynamics a laboratory incubation study was conducted. After fertilization with ammonium sulfate at 5 levels (from 0 to 5000 mg NH4+-N kg-1; 20mg NO3--N kg-1 each), sandy loam soil was incubated in dynamic soil microcosms for 21 days. N2O, CH4 and CO2 fluxes as well as isotope signatures of N2O and, at three dates, NO3- and NH4+ were measured. To identify N2O production processes, acetylene inhibition (0.01 vol.%), 15N tracer approaches, and isotopomer data (15N site preference and δ18O) were used. N2O emissions were highest at 450mg NH4+-N kg-1 and declined with further increasing concentrations. At 5000 mg NH4+-N kg-1 nitrification was completely inhibited. However, approximately 90% of N2O production was inhibited by acetylene application, and there was no change in the relative contribution of nitrification and denitrification to N2O production with N level. Applying the non-equilibrium technique to our 15N tracer data revealed heterogeneous distribution of denitrification in soil, with at least two distinct NO3- pools, and spatial separation of NO3- formation and consumption. In comparison with the acetylene inhibition and 15N tracer approaches the results of the isotopomer approach were reasonable and indicated substantial contribution of nitrifier-denitrification (10-40%) to total N2O

  4. The Uniframe .Net Web Service Discovery Service

    National Research Council Canada - National Science Library

    Berbeco, Robert W

    2003-01-01

    Microsoft .NET allows the creation of distributed systems in a seamless manner Within NET small, discrete applications, referred to as Web services, are utilized to connect to each other or larger applications...

  5. Long Term RadNet Quality Data

    Data.gov (United States)

    U.S. Environmental Protection Agency — This RadNet Quality Data Asset includes all data since initiation and when ERAMS was expanded to become RadNet, name changed to reflect new mission. This includes...

  6. Special Section on Coloured Petri Nets

    DEFF Research Database (Denmark)

    1998-01-01

    Special section on coloured Petri nets, their basic concepts, analysis methods, tool support and industrial applications.......Special section on coloured Petri nets, their basic concepts, analysis methods, tool support and industrial applications....

  7. Aktivasi Keterlibatan Publik dalam Program Berita ‘NET 10’

    Directory of Open Access Journals (Sweden)

    Dinar Safa Anggraeni

    2017-06-01

    Full Text Available This research entitled Activation of The Public Engagement in `NET 10` News Program. An intrinsic case study by Robert E. Stake on Activating The Public Engagement in `NET 10` Citizen Journalism NET TV’s News Program. This research aimed to understand NET TV’s public management strategy in 'NET 10' news program. In addition, this research also aimed to determine how the editorial staff considere the standard of news value and news judgment on citizen journalist news, and the function of public sphere in the mass media of citizen journalism. The method used qualitative research with intrinsic case study approach by Robert E. Stake to NET TV’s editorial. The results showed the editorial’s strategy of public management by following action: (1 provided easily of joining  'NET CJ', (2 created  campaigns to increase the number of CJ, (3 nature CJ by keeping good and giving relationship evaluations, (4 provides rewards for the creator of CJ news aired in 'NET 10', and (5 educates CJ in making a citizen journalism news. NET TV used curation techniques in the process of citizen journalism news gatekeeper to keep the news value and news judment standard of citizen journalism news. Unfortunately, ‘NET 10’’s citizen journalism news rate of the proportion of news comprehensive continues to fall down because the editorial put loyalty forward. 'NET CJ' act as a opinions catalyst of the citizens to the government.

  8. Effects of pH and seasonal temperature variation on simultaneous partial nitrification and anammox in free-water surface wetlands.

    Science.gov (United States)

    He, Yuling; Tao, Wendong; Wang, Ziyuan; Shayya, Walid

    2012-11-15

    Design considerations to enhance simultaneous partial nitrification and anammox in constructed wetlands are largely unknown. This study examined the effects of pH and seasonal temperature variation on simultaneous partial nitrification and anammox in two free-water surface wetlands. In order to enhance partial nitrification and inhibit nitrite oxidation, furnace slag was placed on the rooting substrate to maintain different pH levels in the wetland water. The wetlands were batch operated for dairy wastewater treatment under oxygen-limited conditions at a cycle time of 7 d. Fluorescence in situ hybridization analysis found that aerobic ammonium oxidizing bacteria and anammox bacteria accounted for 42-73% of the bacterial populations in the wetlands, which was the highest relative abundance of ammonium oxidizing and anammox bacteria in constructed wetlands enhancing simultaneous partial nitrification and anammox. The two wetlands removed total inorganic nitrogen efficiently, 3.36-3.38 g/m(2)/d in the warm season with water temperatures at 18.9-24.9 °C and 1.09-1.50 g/m(2)/d in the cool season at 13.8-18.9 °C. Plant uptake contributed 2-45% to the total inorganic nitrogen removal in the growing season. A seasonal temperature variation of more than 6 °C would affect simultaneous partial nitrification and anammox significantly. Significant pH effects were identified only when the temperatures were below 18.9 °C. Anammox was the limiting stage of simultaneous partial nitrification and anammox in the wetlands. Water pH should be controlled along with influent ammonium concentration and temperature to avoid toxicity of free ammonia to anammox bacteria. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Towards new information resources for public health--from WordNet to MedicalWordNet.

    Science.gov (United States)

    Fellbaum, Christiane; Hahn, Udo; Smith, Barry

    2006-06-01

    In the last two decades, WordNet has evolved as the most comprehensive computational lexicon of general English. In this article, we discuss its potential for supporting the creation of an entirely new kind of information resource for public health, viz. MedicalWordNet. This resource is not to be conceived merely as a lexical extension of the original WordNet to medical terminology; indeed, there is already a considerable degree of overlap between WordNet and the vocabulary of medicine. Instead, we propose a new type of repository, consisting of three large collections of (1) medically relevant word forms, structured along the lines of the existing Princeton WordNet; (2) medically validated propositions, referred to here as medical facts, which will constitute what we shall call MedicalFactNet; and (3) propositions reflecting laypersons' medical beliefs, which will constitute what we shall call the MedicalBeliefNet. We introduce a methodology for setting up the MedicalWordNet. We then turn to the discussion of research challenges that have to be met to build this new type of information resource. We build a database of sentences relevant to the medical domain. The sentences are generated from WordNet via its relations as well as from medical statements broken down into elementary propositions. Two subcorpora of sentences are distinguished, MedicalBeliefNet and MedicalFactNet. The former is rated for assent by laypersons; the latter for correctness by medical experts. The sentence corpora will be valuable for a variety of applications in information retrieval as well as in research in linguistics and psychology with respect to the study of expert and non-expert beliefs and their linguistic expressions. Our work has to meet several considerable challenges. These include accounting for the distinction between medical experts and laypersons, the social issues of expert-layperson communication in different media, the linguistic aspects of encoding medical knowledge, and

  10. NetBeans IDE 8 cookbook

    CERN Document Server

    Salter, David

    2014-01-01

    If you're a Java developer of any level using NetBeans and want to learn how to get the most out of NetBeans, then this book is for you. Learning how to utilize NetBeans will provide a firm foundation for your Java application development.

  11. History-dependent stochastic Petri nets

    NARCIS (Netherlands)

    Schonenberg, H.; Sidorova, N.; Aalst, van der W.M.P.; Hee, van K.M.; Pnueli, A.; Virbitskaite, I.; Voronkov, A.

    2010-01-01

    Stochastic Petri Nets are a useful and well-known tool for performance analysis. However, an implicit assumption in the different types of Stochastic Petri Nets is the Markov property. It is assumed that a choice in the Petri net only depends on the current state and not on earlier choices. For many

  12. Putting Petri nets to work in Industry

    NARCIS (Netherlands)

    Aalst, van der W.M.P.

    1994-01-01

    Petri nets exist for over 30 years. Especially in the last decade Petri nets have been put into practive extensively. Thanks to several useful extensions and the availability of computer tools, Petri nets have become a mature tool for modelling and analysing industrial systems. This paper describes

  13. Aplicació Microsoft .Net : Hotel Spa

    OpenAIRE

    Marquès Palmer, Jordi

    2010-01-01

    Desenvolupament d'una aplicació amb Microsoft .NET, WCF, WPF, Linq2SQL, d'un Hotel Spa. Desarrollo de una aplicación con Microsoft .NET, WCF, WPF, Linq2SQL, de un Hotel Spa. Application development using Microsoft .NET, WCF, WPF, Linq2SQL, for a Spa Hotel.

  14. Delta Semantics Defined By Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kyng, Morten; Madsen, Ole Lehrmann

    and the possibility of using predicates to specify state changes. In this paper a formal semantics for Delta is defined and analysed using Petri nets. Petri nets was chosen because the ideas behind Petri nets and Delta concide on several points. A number of proposals for changes in Delta, which resulted from...

  15. The K-NET - A year after

    International Nuclear Information System (INIS)

    Kinoshita, S.; Ohtani, K.; Katayama, T.

    2001-01-01

    We started to release the K-NET strong-motion data from June 1996 and about one year passed. In this article, we report the development of K-NET and some applications using the K-NET information released on the Internet. (author)

  16. 47 CFR 65.500 - Net income.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Net income. 65.500 Section 65.500... OF RETURN PRESCRIPTION PROCEDURES AND METHODOLOGIES Interexchange Carriers § 65.500 Net income. The net income methodology specified in § 65.450 shall be utilized by all interexchange carriers that are...

  17. 47 CFR 65.450 - Net income.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Net income. 65.450 Section 65.450... OF RETURN PRESCRIPTION PROCEDURES AND METHODOLOGIES Exchange Carriers § 65.450 Net income. (a) Net income shall consist of all revenues derived from the provision of interstate telecommunications services...

  18. INMARSAT-C SafetyNET

    Science.gov (United States)

    Tsunamis 406 EPIRB's National Weather Service Marine Forecasts INMARSAT-C SafetyNET Marine Forecast Offices greater danger near shore or any shallow waters? NATIONAL WEATHER SERVICE PRODUCTS VIA INMARSAT-C SafetyNET Inmarsat-C SafetyNET is an internationally adopted, automated satellite system for promulgating

  19. Basis Risk and Net Interest Income of Banks

    Directory of Open Access Journals (Sweden)

    Mielus Piotr

    2016-12-01

    Full Text Available The results of the banking sector are shaped primarily by commissions and net interest income. Net interest income is determined by the difference between the profitability of bank assets and liabilities. In the case when a different method is used to determine interest for each side of the balance sheet, there occurs a basis risk that may lead to the deterioration in the net interest income of the sector. This is the situation in the Polish banking sector, which is characterized by the presence of variable interest rates for long-term assets and fixed interest rates for short-term liabilities. The study aims to verify the following thesis: in an environment of falling interest rates we can observe the deterioration in net interest income of the banking sector, as a result of the materialization of the basis risk. The authors of the article state that the source of the basis risk is the mismatch between the reference rate used to define the interest flow of loans and the actual cost of financing the balance through term deposits collected from non-financial entities.

  20. Avaliação de um reator de lodo ativado aplicado à nitrificação utilizando ensaios cinéticos = Evaluation of an activated sludge reactor applied to nitrification using kinetic assays

    Directory of Open Access Journals (Sweden)

    Valeria Reginatto

    2008-01-01

    Full Text Available Neste trabalho, um reator em escala laboratorial de lodo ativado, aplicado ao processo da nitrificação, foi acompanhado por meio de ensaios cinéticos de atividade específica. A atividade de nitrificação da biomassa foi determinada por respirometria nacaracterização do inóculo e na avaliação da biomassa do reator em duas condições: durante a alimentação do reator com meio sintético autotrófico; e após a sua alimentação com efluente de um reator UASB, utilizado para desnitrificação. O reator atingiu uma eficiência em torno de 90% de nitrificação em ambas as condições de operação. O modelo cinético de Andrews, que inclui uma constante da inibição pelo substrato (Ki, ajustou-se melhor aos resultados obtidos nos testes de atividade do que o de Monod. Entretanto, observou-se aumento daconstante de inibição (Ki do lodo após operação do reator em relação ao inóculo, demonstrando a adaptação da biomassa às novas condições (cargas de nitrificação.In this work, an activated sludge lab-scale reactor used fornitrification was monitored by specific activity kinetic assays. The nitrification biomass activity was carried out by respirometric methods in order to characterize the inoculum and the reactor sludge after two different operation conditions: during the feeding of the reactor with synthetic autotrophic medium, and after feeding it with effluent from an UASB reactor used for denitrification. The efficiency of nitrification reached 90% in both operation conditions. Results obtained by the kinetic activity assays were better adjusted by the kinetic model of Andrews, which includes the inhibition constant by the substrate (Ki, than the Monod model. However, an increase was observed in the inhibition constant (Ki of the sludge after the operation of the reactor as compared with the inoculum. This effect demonstrates an adaptation of the biomass to the new nitrification conditions (loading rate.

  1. Net-infiltration map of the Navajo Sandstone outcrop area in western Washington County, Utah

    Science.gov (United States)

    Heilweil, Victor M.; McKinney, Tim S.

    2007-01-01

    As populations grow in the arid southwestern United States and desert bedrock aquifers are increasingly targeted for future development, understanding and quantifying the spatial variability of net infiltration and recharge becomes critically important for inventorying groundwater resources and mapping contamination vulnerability. A Geographic Information System (GIS)-based model utilizing readily available soils, topographic, precipitation, and outcrop data has been developed for predicting net infiltration to exposed and soil-covered areas of the Navajo Sandstone outcrop of southwestern Utah. The Navajo Sandstone is an important regional bedrock aquifer. The GIS model determines the net-infiltration percentage of precipitation by using an empirical equation. This relation is derived from least squares linear regression between three surficial parameters (soil coarseness, topographic slope, and downgradient distance from outcrop) and the percentage of estimated net infiltration based on environmental tracer data from excavations and boreholes at Sand Hollow Reservoir in the southeastern part of the study area.Processed GIS raster layers are applied as parameters in the empirical equation for determining net infiltration for soil-covered areas as a percentage of precipitation. This net-infiltration percentage is multiplied by average annual Parameter-elevation Regressions on Independent Slopes Model (PRISM) precipitation data to obtain an infiltration rate for each model cell. Additionally, net infiltration on exposed outcrop areas is set to 10 percent of precipitation on the basis of borehole net-infiltration estimates. Soils and outcrop net-infiltration rates are merged to form a final map.Areas of low, medium, and high potential for ground-water recharge have been identified, and estimates of net infiltration range from 0.1 to 66 millimeters per year (mm/yr). Estimated net-infiltration rates of less than 10 mm/yr are considered low, rates of 10 to 50 mm/yr are

  2. NET 40 Generics Beginner's Guide

    CERN Document Server

    Mukherjee, Sudipta

    2012-01-01

    This is a concise, practical guide that will help you learn Generics in .NET, with lots of real world and fun-to-build examples and clear explanations. It is packed with screenshots to aid your understanding of the process. This book is aimed at beginners in Generics. It assumes some working knowledge of C# , but it isn't mandatory. The following would get the most use out of the book: Newbie C# developers struggling with Generics. Experienced C++ and Java Programmers who are migrating to C# and looking for an alternative to other generic frameworks like STL and JCF would find this book handy.

  3. Nitrogen removal from sludge digester liquids by nitrification/denitrification or partial nitritation/anammox: environmental and economical considerations.

    Science.gov (United States)

    Fux, C; Siegrist, H

    2004-01-01

    In wastewater treatment plants with anaerobic sludge digestion, 15-20% of the nitrogen load is recirculated to the main stream with the return liquors from dewatering. Separate treatment of this ammonium-rich digester supernatant significantly reduces the nitrogen load of the activated sludge system. Two biological applications are considered for nitrogen elimination: (i) classical autotrophic nitrification/heterotrophic denitrification and (ii) partial nitritation/autotrophic anaerobic ammonium oxidation (anammox). With both applications 85-90% nitrogen removal can be achieved, but there are considerable differences in terms of sustainability and costs. The final gaseous products for heterotrophic denitrification are generally not measured and are assumed to be nitrogen gas (N2). However, significant nitrous oxide (N2O) production can occur at elevated nitrite concentrations in the reactor. Denitrification via nitrite instead of nitrate has been promoted in recent years in order to reduce the oxygen and the organic carbon requirements. Obviously this "achievement" turns out to be rather disadvantageous from an overall environmental point of view. On the other hand no unfavorable intermediates are emitted during anaerobic ammonium oxidation. A cost estimate for both applications demonstrates that partial nitritation/anammox is also more economical than classical nitrification/denitrification. Therefore autotrophic nitrogen elimination should be used in future to treat ammonium-rich sludge liquors.

  4. Effect of nitrification inhibitors on the content of available nitrogen forms in the soil under maize (Zea mays, L. growing

    Directory of Open Access Journals (Sweden)

    Zuzana PANAKOVA

    2016-12-01

    Full Text Available The objective of this research was to investigate the effect of nitrification inhibitors (dicyandiamide and 1,2,4 triazole on the content of nitrate and ammonium nitrogen in the soil and the effectiveness of nitrogen-sulphur nutrition of maize. The research was conducted in field small-plot experiment with maize on Haplic Luvisol with dominance of clay fraction in experimental years 2012 to 2015. The dose of nitrogen in all experimental treatments was 160 kg*ha-1 and was applied at one shot or split in three partial doses. Soil samples from all examined treatments were taken from three soil depths (0.0-0.3 m, 0.3-0.6 m and 0.6-0.9 m, respectively by probe rod in 4-5 week intervals. Achieved results indicate that on the average of four years and three depths of the soil profile, application of nitrification inhibitors contained in fertilizer ENSIN considerably reduced portion of nitrate nitrogen from the content of mineral nitrogen in the soil by 7-32 relative %. The application of fertilizer ENSIN considerably increased content of ammonium nitrogen in the soil by 10-59 relative %. A favourable effect on increase of ammonium nitrogen content and reduction of nitrate nitrogen content was found out in spite of the fact that in this treatment the total dose of fertilizer was applied at one shot.

  5. [Isolation, Identification and Nitrogen Removal Characteristics of a Heterotrophic Nitrification-Aerobic Denitrification Strain y3 Isolated from Marine Environment].

    Science.gov (United States)

    Sun, Qing-hua; Yu, De-shuang; Zhang, Pei-yu; Lin, Xue-zheng; Xu, Guang-yao; Li, Jin

    2016-03-15

    A heterotrophic nitrification--aerobic denitrification bacterium named y3 was isolated from the sludge of Jiaozhou Bay using the enrichment medium with seawater as the matrix. It was identified as Pseudomonas sp. based on the morphological observation, physiological experiments and sequence analysis of 16S rRNA. The experiment results showed that the optimal carbon resource was sodium citrate, the optimal pH was 7.0, and the optimal C/N was 13. The strain could use NH₄Cl, NaNO₂ and KNO₃ as sole nitrogen source, and the removal efficiencies were 98.69%, 78.38% and 72.95% within 20 hours, respectively. There was no nitrate and nitrite accumulation during the heterotrophic nitrification process. Within 20 hours, the nitrogen removal efficiencies were 99.56%, 99.75% and 99.41%, respectively, in the mixed system with NO₃⁻-N: NO²⁻-N of 2:1, 1:1 and 1:2. When the NH₄⁺-N: NO₃⁻-N ratios were 2: 1 , 1: 1 , 1: 2, the nitrogen removal efficiencies were all 100% . When the NH₄⁺-N:NO₂⁻-N ratios were 2:1,1:1,1:2, the nitrogen removal efficiencies were 90.43%, 92.79% and 99.96%, respectively. They were higher than those with single nitrogen source. As a result, strain y3 had good nitrogen removal performance in high saline wastewater treatment.

  6. Nitrifying bacterial biomass and nitrification activity evaluated by FISH and an automatic on-line instrument at full-scale Fusina (Venice, Italy) WWTP.

    Science.gov (United States)

    Badoer, S; Miana, P; Della Sala, S; Marchiori, G; Tandoi, V; Di Pippo, F

    2015-12-01

    In this study, monthly variations in biomass of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were analysed over a 1-year period by fluorescence in situ hybridization (FISH) at the full-scale Fusina WWTP. The nitrification capacity of the plant was also monitored using periodic respirometric batch tests and by an automated on-line titrimetric instrument (TITrimetric Automated ANalyser). The percentage of nitrifying bacteria in the plant was the highest in summer and was in the range of 10-15 % of the active biomass. The maximum nitrosation rate varied in the range 2.0-4.0 mg NH4 g(-1) VSS h(-1) (0.048-0.096 kg TKN kg(-1) VSS day(-1)): values obtained by laboratory measurements and the on-line instrument were similar and significantly correlated. The activity measurements provided a valuable tool for estimating the maximum total Kjeldahl nitrogen (TKN) loading possible at the plant and provided an early warning of whether the TKN was approaching its limiting value. The FISH analysis permitted determination of the nitrifying biomass present. The main operational parameter affecting both the population dynamics and the maximum nitrosation activity was mixed liquor volatile suspended solids (MLVSS) concentration and was negatively correlated with ammonia-oxidizing bacteria (AOB) (p = 0.029) and (NOB) (p = 0.01) abundances and positively correlated with maximum nitrosation rates (p = 0.035). Increases in concentrations led to decreases in nitrifying bacteria abundance, but their nitrosation activity was higher. These results demonstrate the importance of MLVSS concentration as key factor in the development and activity of nitrifying communities in wastewater treatment plants (WWTPs). Operational data on VSS and sludge volume index (SVI) values are also presented on 11-year basis observations.

  7. Complete nitrogen removal from municipal wastewater via partial nitrification by appropriately alternating anoxic/aerobic conditions in a continuous plug-flow step feed process.

    Science.gov (United States)

    Ge, Shijian; Peng, Yongzhen; Qiu, Shuang; Zhu, Ao; Ren, Nanqi

    2014-05-15

    This study assessed the technical feasibility of removing nitrogen from municipal wastewater by partial nitrification (nitritation) in a continuous plug-flow step feed process. Nitrite in the effluent accumulated to over 81.5  ± 9.2% but disappeared with the transition of process operation from anoxic/oxic mode to the anaerobic/anoxic/oxic mode. Batch tests showed obvious ammonia oxidizing bacteria (AOB) stimulation (advanced ammonia oxidation rate) and nitrite (NOB) oxidizing bacteria inhibition (reduced nitrite oxidation rate) under transient anoxic conditions. Two main factors contributed to nitritation in this continuous plug-flow process: One was the alternating anoxic and oxic operational condition; the step feed strategy guaranteed timely denitrification in anoxic zones, allowing a reduction in energy supply (nitrite) to NOB. Fluorescence in Situ Hybridization and quantitative real-time polymerase chain reaction analysis indicated that NOB population gradually decreased to 1.0  ± 0.1% of the total bacterial population (dominant Nitrospira spp., 1.55 × 10(9) copies/L) while AOB increased approximately two-fold (7.4  ± 0.9%, 1.25 × 10(10) copies/L) during the above anoxic to anaerobic transition. Most importantly, without addition of external carbon sources, the above wastewater treatment process reached 86.0  ± 4.2% of total nitrogen (TN) removal with only 7.23 ± 2.31 mg/L of TN in the effluent, which met the discharge requirements. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Possibilistic Fuzzy Net Present Value Model and Application

    Directory of Open Access Journals (Sweden)

    S. S. Appadoo

    2014-01-01

    Full Text Available The cash flow values and the interest rate in the net present value (NPV model are usually specified by either crisp numbers or random variables. In this paper, we first discuss some of the recent developments in possibility theory and find closed form expressions for fuzzy possibilistic net present value (FNPV. Then, following Carlsson and Fullér (2001, we discuss some of the possibilistic moments related to FNPV model along with an illustrative numerical example. We also give a unified approach to find higher order moments of FNPV by using the moment generating function introduced by Paseka et al. (2011.

  9. Towards a Standard for Modular Petri Nets

    DEFF Research Database (Denmark)

    Kindler, Ekkart; Petrucci, Laure

    2009-01-01

    concepts could or should be subject to import and export in high-level Petri nets. In this paper, we formalise a minimal version of modular high-level Petri nets, which is based on the concepts of modular PNML. This shows that modular PNML can be formalised once a specific version of Petri net is fixed....... Moreover, we present and discuss some more advanced features of modular Petri nets that could be included in the standard. This way, we provide a formal foundation and a basis for a discussion of features to be included in the upcoming standard of a module concept for Petri nets in general and for high-level...

  10. Neural net prediction of tokamak plasma disruptions

    International Nuclear Information System (INIS)

    Hernandez, J.V.; Lin, Z.; Horton, W.; McCool, S.C.

    1994-10-01

    The computation based on neural net algorithms in predicting minor and major disruptions in TEXT tokamak discharges has been performed. Future values of the fluctuating magnetic signal are predicted based on L past values of the magnetic fluctuation signal, measured by a single Mirnov coil. The time step used (= 0.04ms) corresponds to the experimental data sampling rate. Two kinds of approaches are adopted for the task, the contiguous future prediction and the multi-timescale prediction. Results are shown for comparison. Both networks are trained through the back-propagation algorithm with inertial terms. The degree of this success indicates that the magnetic fluctuations associated with tokamak disruptions may be characterized by a relatively low-dimensional dynamical system

  11. Climatic Forecasting of Net Infiltration at Yucca Mountain Using Analogue Meteorological Data

    International Nuclear Information System (INIS)

    B. Faybishenko

    2006-01-01

    At Yucca Mountain, Nevada, future changes in climatic conditions will most likely alter net infiltration, or the drainage below the bottom of the evapotranspiration zone within the soil profile or flow across the interface between soil and the densely welded part of the Tiva Canyon Tuff. The objectives of this paper are to: (a) develop a semi-empirical model and forecast average net infiltration rates, using the limited meteorological data from analogue meteorological stations, for interglacial (present day), and future monsoon, glacial transition, and glacial climates over the Yucca Mountain region, and (b) corroborate the computed net-infiltration rates by comparing them with the empirically and numerically determined groundwater recharge and percolation rates through the unsaturated zone from published data. In this paper, the author presents an approach for calculations of net infiltration, aridity, and precipitation-effectiveness indices, using a modified Budyko's water-balance model, with reference-surface potential evapotranspiration determined from the radiation-based Penman (1948) formula. Results of calculations show that net infiltration rates are expected to generally increase from the present-day climate to monsoon climate, to glacial transition climate, and then to the glacial climate. The forecasting results indicate the overlap between the ranges of net infiltration for different climates. For example, the mean glacial net-infiltration rate corresponds to the upper-bound glacial transition net infiltration, and the lower-bound glacial net infiltration corresponds to the glacial transition mean net infiltration. Forecasting of net infiltration for different climate states is subject to numerous uncertainties-associated with selecting climate analogue sites, using relatively short analogue meteorological records, neglecting the effects of vegetation and surface runoff and runon on a local scale, as well as possible anthropogenic climate changes

  12. Net metering in British Columbia : white paper

    International Nuclear Information System (INIS)

    Berry, T.

    2003-01-01

    Net metering was described as being the reverse registration of an electricity customer's revenue meter when interconnected with a utility's grid. It is a provincial policy designed to encourage small-distributed renewable power generation such as micro-hydro, solar energy, fuel cells, and larger-scale wind energy. It was noted that interconnection standards for small generation is an important issue that must be addressed. The British Columbia Utilities Commission has asked BC Hydro to prepare a report on the merits of net metering in order to support consultations on a potential net metering tariff application by the utility. This report provides information on net metering with reference to experience in other jurisdictions with net metering, and the possible costs and benefits associated with net metering from both a utility and consumer perspective. Some of the barriers and policy considerations for successful implementation of net metering were also discussed. refs., tabs., figs

  13. Pro-Nets versus No-Nets: Differences in Urban Older Adults' Predilections for Internet Use

    Science.gov (United States)

    Cresci, M. Kay; Yarandi, Hossein N.; Morrell, Roger W.

    2010-01-01

    Enthusiasm for information technology (IT) is growing among older adults. Many older adults enjoy IT and the Internet (Pro-Nets), but others have no desire to use it (No-Nets). This study found that Pro-Nets and No-Nets were different on a number of variables that might predict IT use. No-Nets were older, had less education and income, were…

  14. Risk assessment for invasive species produces net bioeconomic benefits.

    Science.gov (United States)

    Keller, Reuben P; Lodge, David M; Finnoff, David C

    2007-01-02

    International commerce in live organisms presents a policy challenge for trade globalization; sales of live organisms create wealth, but some nonindigenous species cause harm. To reduce damage, some countries have implemented species screening to limit the introduction of damaging species. Adoption of new risk assessment (RA) technologies has been slowed, however, by concerns that RA accuracy remains insufficient to produce positive net economic benefits. This concern arises because only a small proportion of all introduced species escape, spread, and cause harm (i.e., become invasive), so a RA will exclude many noninvasive species (which provide a net economic benefit) for every invasive species correctly identified. Here, we develop a simple cost:benefit bioeconomic framework to quantify the net benefits from applying species prescreening. Because invasive species are rarely eradicated, and their damages must therefore be borne for long periods, we have projected the value of RA over a suitable range of policy time horizons (10-500 years). We apply the model to the Australian plant quarantine program and show that this RA program produces positive net economic benefits over the range of reasonable assumptions. Because we use low estimates of the financial damage caused by invasive species and high estimates of the value of species in the ornamental trade, our results underestimate the net benefit of the Australian plant quarantine program. In addition, because plants have relatively low rates of invasion, applying screening protocols to animals would likely demonstrate even greater benefits.

  15. Using Routine Data for Quality Assessment in NeuroNet Telestroke Care

    DEFF Research Database (Denmark)

    Theiss, Stephan; Günzel, Franziska; Storm, Anna

    2013-01-01

    : Routine clinical data from the HELIOS hospital information system were compared before and after implementation of the NeuroNet concept, including neurologic acute stroke teleconsultations, standard operating procedures, and peer review quality management in 3 hospital cohorts: 5 comprehensive stroke...... centers, 5 NeuroNet hospitals, and 5 matched control hospitals. RESULTS: During the study period, the rate of thrombolytic therapy increased by 4.8% in NeuroNet hospitals, while ischemic stroke in-hospital mortality decreased (relative risk reduction ∼29% in NeuroNet and control hospitals). The odds ratio...... for thrombolytic therapy in comprehensive stroke centers compared to NeuroNet hospitals was reduced from 3.7 to 1.3 between 2006 and 2009. Comprehensive stroke care coding according to German Diagnosis Related Groups definitions increased by 45% in NeuroNet (P

  16. Contribution of nitrification and denitrification to the NO and N2O emissions of an acid forest soil, a river sediment and a fertilized grassland soil

    NARCIS (Netherlands)

    Kester, R.A.; Meijer, M.L.; Libochant, J.A.; De Boer, W.; Laanbroek, H.J.

    1997-01-01

    Most studies determining the contribution of nitrification and denitrification to NO and N2O emissions from soils have been performed in agricultural systems, often with homogenized soil samples. More information about the nitrifier and denitrifier contribution in non-agricultural systems may

  17. Removal of nitrogen and organic matter in a submerged-membrane bioreactor operating in a condition of simultaneous nitrification and denitrification

    Directory of Open Access Journals (Sweden)

    Izabela Major Barbosa

    2016-04-01

    Full Text Available This study evaluated the removal of nitrogen and organic matter in a membrane bioreactor system operating in a condition of simultaneous nitrification and denitrification controlled by intermittent aeration. A submerged-membrane system in a bioreactor was used in a pilot scale to treat domestic wastewater. The dissolved oxygen concentration was maintained between 0.5 and 0.8 mg L-1. The concentration of the mixed liquor suspended solids (MLSS in the system ranged from 1 to 6 g L-1. The system efficiency was evaluated by the removal efficiency of organic matter, quantified by Chemical Oxygen Demand (COD, Biochemical Oxygen Demand (BOD5 and Total Organic Carbon (TOC. Nitrogen removal was assessed by quantifying Total Kjeldahl Nitrogen (TKN and ammonia nitrogen. During the system start-up, the removal efficiencies of COD and NTK were around 90% and 80%, respectively. After the simultaneous nitrification and denitrification (SND conditions were established, the removal efficiencies of COD and NTK were 70% and 99%, respectively. These results showed that sewage treatment with the membrane bioreactor (MBR system, operating with simultaneous nitrification and denitrification conditions, was able to remove organic matter and promote nitrification and denitrification in a single reactor, producing a high-quality permeate.

  18. Soil microbial toxicity of eight polycyclic aromatic compounds: effects on nitrification, the genetic diversity of bacteria, and the total number of protozoans

    DEFF Research Database (Denmark)

    Sverdrup, Line Emilie; Ekelund, Flemming; Krogh, Paul Henning

    2002-01-01

    mg/kg. For effects on nitrification, toxicity (NOEC values) expressed as soil pore-water concentrations (log10(micromol/L)) showed a significant inverse relationship with lipophilicity (log octanol-water partition coefficient) of the substances (r2 = 0.69, p = 0.011, n = 8). This finding could...

  19. Shell Biofilm Nitrification and Gut Denitrification Contribute to Emission of Nitrous Oxide by the Invasive Freshwater Mussel Dreissena polymorpha (Zebra Mussel)

    Science.gov (United States)

    Svenningsen, Nanna B.; Heisterkamp, Ines M.; Sigby-Clausen, Maria; Larsen, Lone H.; Nielsen, Lars Peter; Stief, Peter

    2012-01-01

    Nitrification in shell biofilms and denitrification in the gut of the animal accounted for N2O emission by Dreissena polymorpha (Bivalvia), as shown by gas chromatography and gene expression analysis. The mussel's ammonium excretion was sufficient to sustain N2O production and thus potentially uncouples invertebrate N2O production from environmental N concentrations. PMID:22492461

  20. Bound states in string nets

    Science.gov (United States)

    Schulz, Marc Daniel; Dusuel, Sébastien; Vidal, Julien

    2016-11-01

    We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.

  1. -Net Approach to Sensor -Coverage

    Directory of Open Access Journals (Sweden)

    Fusco Giordano

    2010-01-01

    Full Text Available Wireless sensors rely on battery power, and in many applications it is difficult or prohibitive to replace them. Hence, in order to prolongate the system's lifetime, some sensors can be kept inactive while others perform all the tasks. In this paper, we study the -coverage problem of activating the minimum number of sensors to ensure that every point in the area is covered by at least sensors. This ensures higher fault tolerance, robustness, and improves many operations, among which position detection and intrusion detection. The -coverage problem is trivially NP-complete, and hence we can only provide approximation algorithms. In this paper, we present an algorithm based on an extension of the classical -net technique. This method gives an -approximation, where is the number of sensors in an optimal solution. We do not make any particular assumption on the shape of the areas covered by each sensor, besides that they must be closed, connected, and without holes.

  2. The Net Reclassification Index (NRI)

    DEFF Research Database (Denmark)

    Pepe, Margaret S.; Fan, Jing; Feng, Ziding

    2015-01-01

    The Net Reclassification Index (NRI) is a very popular measure for evaluating the improvement in prediction performance gained by adding a marker to a set of baseline predictors. However, the statistical properties of this novel measure have not been explored in depth. We demonstrate the alarming...... result that the NRI statistic calculated on a large test dataset using risk models derived from a training set is likely to be positive even when the new marker has no predictive information. A related theoretical example is provided in which an incorrect risk function that includes an uninformative...... marker is proven to erroneously yield a positive NRI. Some insight into this phenomenon is provided. Since large values for the NRI statistic may simply be due to use of poorly fitting risk models, we suggest caution in using the NRI as the basis for marker evaluation. Other measures of prediction...

  3. NETS - Danish participation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Alsen, S. (Grontmij - Carl Bro, Glostrup (Denmark)); Theel, C. (Baltic Sea Solutions, Holeby (Denmark))

    2008-12-15

    Within the NICe-funded project 'Nordic Environmental Technology Solutions (NETS)' a new type of networking at the Nordic level was organized in order to jointly exploit the rapidly growing market potential in the environmental technology sector. The project aimed at increased and professionalized commercialization of Nordic Cleantech in energy and water business segments through 1) closer cooperation and joint marketing activities, 2) a website, 3) cleantech product information via brochures and publications 4) and participating in relevant trade fairs and other industry events. Facilitating business-to-business activities was another core task for the NETS project partners from Norway, Sweden, Finland and Denmark with the aim to encourage total solutions for combined Cleantech system offers. The project has achieved to establish a Cleantech register of 600 Nordic Cleantech companies, a network of 86 member enterprises, produced several publications and brochures for direct technology promotion and a website for direct access to company profiles and contact data. The project partners have attended 14 relevant international Cleantech trade fairs and conferences and facilitated business-to-business contacts added by capacity building offers through two company workshops. The future challenge for the project partners and Nordic Cleantech will be to coordinate the numerous efforts within the Nordic countries in order to reach concerted action and binding of member companies for reliable services, an improved visibility and knowledge exchange. With Cleantech's growing market influence and public awareness, the need to develop total solutions is increasing likewise. Marketing efforts should be encouraged cross-sectional and cross-border among the various levels of involved actors from both the public and the private sector. (au)

  4. NETS - Danish participation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Alsen, S [Grontmij - Carl Bro, Glostrup (Denmark); Theel, C [Baltic Sea Solutions, Holeby (Denmark)

    2008-12-15

    Within the NICe-funded project 'Nordic Environmental Technology Solutions (NETS)' a new type of networking at the Nordic level was organized in order to jointly exploit the rapidly growing market potential in the environmental technology sector. The project aimed at increased and professionalized commercialization of Nordic Cleantech in energy and water business segments through 1) closer cooperation and joint marketing activities, 2) a website, 3) cleantech product information via brochures and publications 4) and participating in relevant trade fairs and other industry events. Facilitating business-to-business activities was another core task for the NETS project partners from Norway, Sweden, Finland and Denmark with the aim to encourage total solutions for combined Cleantech system offers. The project has achieved to establish a Cleantech register of 600 Nordic Cleantech companies, a network of 86 member enterprises, produced several publications and brochures for direct technology promotion and a website for direct access to company profiles and contact data. The project partners have attended 14 relevant international Cleantech trade fairs and conferences and facilitated business-to-business contacts added by capacity building offers through two company workshops. The future challenge for the project partners and Nordic Cleantech will be to coordinate the numerous efforts within the Nordic countries in order to reach concerted action and binding of member companies for reliable services, an improved visibility and knowledge exchange. With Cleantech's growing market influence and public awareness, the need to develop total solutions is increasing likewise. Marketing efforts should be encouraged cross-sectional and cross-border among the various levels of involved actors from both the public and the private sector. (au)

  5. Effect of Potassium Chlorate on the Treatment of Domestic Sewage by Achieving Shortcut Nitrification in a Constructed Rapid Infiltration System.

    Science.gov (United States)

    Fang, Qinglin; Xu, Wenlai; Yan, Zhijiao; Qian, Lei

    2018-04-04

    A constructed rapid infiltration (CRI) system is a new type of sewage biofilm treatment technology, but due to its anaerobic zone it lacks the carbon sources and the conditions for nitrate retention, and its nitrogen removal performance is very poor. However, a shortcut nitrification–denitrification process presents distinctive advantages, as it saves oxygen, requires less organic matter, and requires less time for denitrification compared to conventional nitrogen removal methods. Thus, if the shortcut nitrification–denitrification process could be applied to the CRI system properly, a simpler, more economic, and efficient nitrogen removal method will be obtained. However, as its reaction process shows that the first and the most important step of achieving shortcut nitrification–denitrification is to achieve shortcut nitrification, in this study we explored the feasibility to achieve shortcut nitrification, which produces nitrite as the dominant nitrogen species in effluent, by the addition of potassium chlorate (KClO₃) to the influent. In an experimental CRI test system, the effects on nitrogen removal, nitrate inhibition, and nitrite accumulation were studied, and the advantages of achieving a shortcut nitrification–denitrification process were also analysed. The results showed that shortcut nitrification was successfully achieved and maintained in a CRI system by adding 5 mM KClO₃ to the influent at a constant pH of 8.4. Under these conditions, the nitrite accumulation percentage was increased, while a lower concentration of 3 mM KClO₃ had no obvious effect. The addition of 5mM KClO₃ in influent presumably inhibited the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), but inhibition of nitrite-oxidizing bacteria (NOB) was so strong that it resulted in a maximum nitrite accumulation percentage of up to over 80%. As a result, nitrite became the dominant nitrogen product in the effluent. Moreover, if the shortcut

  6. Effect of Potassium Chlorate on the Treatment of Domestic Sewage by Achieving Shortcut Nitrification in a Constructed Rapid Infiltration System

    Directory of Open Access Journals (Sweden)

    Qinglin Fang

    2018-04-01

    Full Text Available A constructed rapid infiltration (CRI system is a new type of sewage biofilm treatment technology, but due to its anaerobic zone it lacks the carbon sources and the conditions for nitrate retention, and its nitrogen removal performance is very poor. However, a shortcut nitrification–denitrification process presents distinctive advantages, as it saves oxygen, requires less organic matter, and requires less time for denitrification compared to conventional nitrogen removal methods. Thus, if the shortcut nitrification–denitrification process could be applied to the CRI system properly, a simpler, more economic, and efficient nitrogen removal method will be obtained. However, as its reaction process shows that the first and the most important step of achieving shortcut nitrification–denitrification is to achieve shortcut nitrification, in this study we explored the feasibility to achieve shortcut nitrification, which produces nitrite as the dominant nitrogen species in effluent, by the addition of potassium chlorate (KClO3 to the influent. In an experimental CRI test system, the effects on nitrogen removal, nitrate inhibition, and nitrite accumulation were studied, and the advantages of achieving a shortcut nitrification–denitrification process were also analysed. The results showed that shortcut nitrification was successfully achieved and maintained in a CRI system by adding 5 mM KClO3 to the influent at a constant pH of 8.4. Under these conditions, the nitrite accumulation percentage was increased, while a lower concentration of 3 mM KClO3 had no obvious effect. The addition of 5mM KClO3 in influent presumably inhibited the activity of ammonia-oxidizing bacteria (AOB and nitrite-oxidizing bacteria (NOB, but inhibition of nitrite-oxidizing bacteria (NOB was so strong that it resulted in a maximum nitrite accumulation percentage of up to over 80%. As a result, nitrite became the dominant nitrogen product in the effluent. Moreover, if the

  7. Higher-moment measurements of net-kaon, net-charge and net-proton multiplicity distributions at STAR

    International Nuclear Information System (INIS)

    Sarkar, Amal

    2014-01-01

    In this paper, we report the measurements of the various moments, such as mean, standard deviation (σ), skewness (S) and kurtosis (κ) of the net-kaon, net-charge and net-proton multiplicity distributions at mid-rapidity in Au + Au collisions from √(s NN )=7.7 to 200 GeV with the STAR experiment at RHIC. This work has been done with the aim to locate the critical point on the QCD phase diagram. These moments and their products are related to the thermodynamic susceptibilities of conserved quantities such as net baryon number, net charge, and net strangeness as well as to the correlation length of the system which diverges in an ideal infinite thermodynamic system at the critical point. For a finite system, existing for a finite time, a non-monotonic behavior of these variables would indicate the presence of the critical point. Furthermore, we also present the moment products Sσ, κσ 2 of net-kaon, net-charge and net-proton multiplicity distributions as a function of collision centrality and energy. The energy and the centrality dependence of higher moments and their products have been compared with different models

  8. Uncertainty in Forest Net Present Value Estimations

    Directory of Open Access Journals (Sweden)

    Ilona Pietilä

    2010-09-01

    Full Text Available Uncertainty related to inventory data, growth models and timber price fluctuation was investigated in the assessment of forest property net present value (NPV. The degree of uncertainty associated with inventory data was obtained from previous area-based airborne laser scanning (ALS inventory studies. The study was performed, applying the Monte Carlo simulation, using stand-level growth and yield projection models and three alternative rates of interest (3, 4 and 5%. Timber price fluctuation was portrayed with geometric mean-reverting (GMR price models. The analysis was conducted for four alternative forest properties having varying compartment structures: (A a property having an even development class distribution, (B sapling stands, (C young thinning stands, and (D mature stands. Simulations resulted in predicted yield value (predicted NPV distributions at both stand and property levels. Our results showed that ALS inventory errors were the most prominent source of uncertainty, leading to a 5.1–7.5% relative deviation of property-level NPV when an interest rate of 3% was applied. Interestingly, ALS inventory led to significant biases at the property level, ranging from 8.9% to 14.1% (3% interest rate. ALS inventory-based bias was the most significant in mature stand properties. Errors related to the growth predictions led to a relative standard deviation in NPV, varying from 1.5% to 4.1%. Growth model-related uncertainty was most significant in sapling stand properties. Timber price fluctuation caused the relative standard deviations ranged from 3.4% to 6.4% (3% interest rate. The combined relative variation caused by inventory errors, growth model errors and timber price fluctuation varied, depending on the property type and applied rates of interest, from 6.4% to 12.6%. By applying the methodology described here, one may take into account the effects of various uncertainty factors in the prediction of forest yield value and to supply the

  9. Determinants of the net interest margins in BH banks

    Directory of Open Access Journals (Sweden)

    Plakalović Novo

    2015-01-01

    Full Text Available In this paper, the subject of analysis is influence of certain macroeconomic and microeconomic variables on bank net interest margins in Bosnia and Herzegovina (BH for the period from 2008 to 2013 through a multiple linear regression models. The level and dynamics of NIM indicate the efficiency of financial intermediation. The observed period is characterized by the reduction in net interest margins of banks over the previous decade, which was characterized by high GDP growth, bank loans and high-interest rates and high profitability. Therefore, this study examines the factors that affect the level of net interest margins in the domestic banking industry. The main objective of this paper is to determine whether there is interdependence in the movement between the independent and dependent variables through a multiple linear regression. The net interest margin will be observed as a dependent variable, and liquidity risk, operating costs, credit risk, the index of market concentration, funding risk, the growth rate of gross domestic product and consumer price index will be used as independent variables.

  10. Application and Theory of Petri Nets

    DEFF Research Database (Denmark)

    This volume contains the proceedings of the 13th International Conference onApplication and Theory of Petri Nets, held in Sheffield, England, in June 1992. The aim of the Petri net conferences is to create a forum for discussing progress in the application and theory of Petri nets. Typically....... Balbo and W. Reisig, 18 submitted papers, and seven project papers. The submitted papers and project presentations were selectedby the programme committee and a panel of referees from a large number of submissions....

  11. TwiddleNet: Smartphones as Personal Servers

    OpenAIRE

    Gurminder, Singh; Center for the Study of Mobile Devices and Communications

    2012-01-01

    TwiddleNet uses smartphones as personal servers to enable instant content capture and dissemination for firstresponders. It supports the information sharing needs of first responders in the early stages of an emergency response operation. In TwiddleNet, content, once captured, is automatically tagged and disseminated using one of the several networking channels available in smartphones. TwiddleNet pays special attention to minimizing the equipment, network set-up time, and content...

  12. Effectiveness of insecticide-treated and untreated nets to prevent malaria in India.

    Science.gov (United States)

    Van Remoortel, Hans; De Buck, Emmy; Singhal, Maneesh; Vandekerckhove, Philippe; Agarwal, Satya P

    2015-08-01

    India is the most malaria-endemic country in South-East Asia, resulting in a high socio-economic burden. Insecticide-treated or untreated nets are effective interventions to prevent malaria. As part of an Indian first-aid guideline project, we aimed to investigate the magnitude of this effect in India. We searched MEDLINE, Embase and Central to systematically review Indian studies on the effectiveness of treated or untreated vs. no nets. Parasite prevalence and annual parasite incidence served as malaria outcomes. The overall effect was investigated by performing meta-analyses and calculating the pooled risk ratios (RR) and incidence rate ratios. Of 479 articles, we finally retained 16 Indian studies. Untreated nets decreased the risk of parasite prevalence compared to no nets [RR 0.69 (95% CI; 0.55, 0.87) in high-endemic areas, RR 0.49 (95% CI; 0.28, 0.84) in low-endemic areas], as was the case but more pronounced for treated nets [RR 0.35 (95% CI; 0.26, 0.47) in high-endemic areas, risk ratio 0.16 (95% CI; 0.06, 0.44) in low-endemic areas]. Incidence rate ratios showed a similar observation: a significantly reduced rate of parasites in the blood for untreated nets vs. no nets, which was more pronounced in low-endemic areas and for those who used treated nets. The average effect of treated nets (vs. no nets) on parasite prevalence was higher in Indian studies (RR 0.16-0.35) than in non-Indian studies (data derived from a Cochrane systematic review; RR 0.58-0.87). Both treated and untreated nets have a clear protective effect against malaria in the Indian context. This effect is more pronounced there than in other countries. © 2015 John Wiley & Sons Ltd.

  13. Shortcut nitrification-denitrification by means of autochthonous halophilic biomass in an SBR treating fish-canning wastewater.

    Science.gov (United States)

    Capodici, Marco; Corsino, Santo Fabio; Torregrossa, Michele; Viviani, Gaspare

    2018-02-15

    Autochthonous halophilic biomass was cultivated in a sequencing batch reactor (SBR) aimed at analyzing the potential use of autochthonous halophilic activated sludge in treating saline industrial wastewater. Despite the high salt concentration (30 g NaCl L -1 ), biological oxygen demand (BOD) and total suspended solids (TSS), removal efficiencies were higher than 90%. More than 95% of the nitrogen was removed via a shortcut nitrification-denitrification process. Both the autotrophic and heterotrophic biomass samples exhibited high biological activity. The use of autochthonous halophilic biomass led to high-quality effluent and helped to manage the issues related to nitrogen removal in saline wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Evaluation of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) for N2O mitigation after grassland cultivation

    DEFF Research Database (Denmark)

    Kong, Xianwang

    Temporary grasslands cover ca. 11 million ha and constitute more than 10% of the total arable land within EU-28; in Denmark, ca. 60% of the grasslands are included in crop rotations. The high productivity and the positive residual effect on succeeding crops are the main reasons of placing...... archaea (AOA), as revealed by mRNA transcripts of amoA gene. This inhibitory effect could be limited to the soil volume in close contact with residues, where residue decomposition and subsequent nitrification took place. In the field study, there was a trend towards lower biomass yield and N...... grasslands in crop rotations. At the transition phase, the mineralization of grass and clover residues incorporated by grassland cultivation can supply nitrogen to a succeeding crop; however, the plant N-uptake is low for several weeks at the early growth stage. During this period, as a result of increasing...

  15. Effects of cattle slurry and nitrification inhibitor application on spatial soil O2 dynamics and N2O production pathways

    DEFF Research Database (Denmark)

    Quan, Nguyen Van; Wu, Di; Kong, Xianwang

    2017-01-01

    decomposition. Here, we applied O2 planar optode and N2O isotopomer techniques to investigate the linkage between soil O2 dynamics and N2O production pathways in soils treated with cattle slurry (treatment CS) and tested the effect of the nitrification inhibitor 3,4-dimethyl pyrazole phosphate, DMPP (treatment......Application of cattle slurry to grassland soil has environmental impacts such as ammonia volatilization and greenhouse gas emissions. The extent, however, depends on application method and soil conditions through their effects on infiltration and oxygen (O2) availability during subsequent...... CSD). Twodimensional planar optode images of soil O2 over time revealed that O2 depletion ultimately extended to 1.5 cm depth in CS, as opposed to 1.0 cm in CSD. The 15N site preference (SP) and d18O of emitted N2O varied between 11-25‰and 35e47‰, respectively, indicating a mixture of production...

  16. Professional Visual Basic 2010 and .NET 4

    CERN Document Server

    Sheldon, Bill; Sharkey, Kent

    2010-01-01

    Intermediate and advanced coverage of Visual Basic 2010 and .NET 4 for professional developers. If you've already covered the basics and want to dive deep into VB and .NET topics that professional programmers use most, this is your book. You'll find a quick review of introductory topics-always helpful-before the author team of experts moves you quickly into such topics as data access with ADO.NET, Language Integrated Query (LINQ), security, ASP.NET web programming with Visual Basic, Windows workflow, threading, and more. You'll explore all the new features of Visual Basic 2010 as well as all t

  17. NASA Net Zero Energy Buildings Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Pless, S.; Scheib, J.; Torcellini, P.; Hendron, B.; Slovensky, M.

    2014-10-01

    In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategic approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.

  18. Pro Agile NET Development with Scrum

    CERN Document Server

    Blankenship, Jerrel; Millett, Scott

    2011-01-01

    Pro Agile .NET Development with SCRUM guides you through a real-world ASP.NET project and shows how agile methodology is put into practice. There is plenty of literature on the theory behind agile methodologies, but no book on the market takes the concepts of agile practices and applies these in a practical manner to an end-to-end ASP.NET project, especially the estimating, requirements and management aspects of a project. Pro Agile .NET Development with SCRUM takes you through the initial stages of a project - gathering requirements and setting up an environment - through to the development a

  19. Transformation-Dissolution Reactions Partially Explain Adverse Effects of Metallic Silver Nanoparticles to Soil Nitrification in Different Soils.

    Science.gov (United States)

    Bollyn, Jessica; Willaert, Bernd; Kerré, Bart; Moens, Claudia; Arijs, Katrien; Mertens, Jelle; Leverett, Dean; Oorts, Koen; Smolders, Erik

    2018-04-25

    Risk assessment of metallic nanoparticles (NP) is critically affected by the concern that toxicity goes beyond that of the metallic ion. This study addressed this concern for soils with silver (Ag)-NP using the Ag-sensitive nitrification assay. Three agricultural soils (A,B,C) were spiked with equivalent Ag doses of either Ag-NP (d = 13 nm) or AgNO 3 . Soil solution was isolated and monitored over 97 days with due attention to accurate Ag fractionation at low (∼10 µg L -1 ) Ag concentrations. Truly dissolved (soils decreased with reaction half-lives of 4 to 22 days depending on the soil, denoting important Ag-ageing reactions. In contrast, truly dissolved Ag in Ag-NP-amended soils first increased by dissolution and subsequently decreased by ageing; the concentration never exceeding that in the AgNO 3 -amended soils. The half-lives of Ag-NP transformation-dissolution were about 4 days (soils A&B) and 36 days (soil C). The Ag toxic thresholds (EC10, mg Ag kg -1 soil) of nitrification, either evaluated at 21 or 35 days after spiking, were similar between the two Ag forms (soils A&B) but were factors 3 to 8 lower for AgNO 3 than for Ag-NP (soil C), largely corroborating with dissolution differences. This fate and bio-assay showed that Ag-NPs are not more toxic than AgNO 3 at equivalent total soil Ag concentrations and that differences in Ag-dissolution at least partially explain toxicity differences between the forms and among soils. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  20. Acceleration of aged-landfill stabilization by combining partial nitrification and leachate recirculation: A field-scale study

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Jinwook [R& D Center, Samsung Engineering Co., Ltd., 415-10 Woncheon-dong, Youngtong-gu, Suwon, Gyeonggi-do 443-823 (Korea, Republic of); Kim, Seungjin; Baek, Seungcheon [Department of Civil and Environmental Engineering, Hanyang University, Sa 3-dong, Sangnok-gu, Ansan, Gyeonggi-do 426-791 (Korea, Republic of); Lee, Nam-Hoon [Department of Environmental & Energy Engineering, Anyang University, 22 Samdeok-ro, 37 Beon-gil, Manan-gu, Anyang, Gyeonggi-do 430-714 (Korea, Republic of); Park, Seongjun; Lee, Junghun; Lee, Heechang [Department of Civil and Environmental Engineering, Hanyang University, Sa 3-dong, Sangnok-gu, Ansan, Gyeonggi-do 426-791 (Korea, Republic of); Bae, Wookeun, E-mail: wkbae@hanyang.ac.kr [Department of Civil and Environmental Engineering, Hanyang University, Sa 3-dong, Sangnok-gu, Ansan, Gyeonggi-do 426-791 (Korea, Republic of)

    2015-03-21

    Highlights: • To solve the drawbacks (NH{sub 4}{sup +} accumulation) of leachate recirculation, ex-situ SBR was applied. • Produced NO{sub 2}{sup −} was recirculated and denitrified to N{sub 2} in landfill with insufficient carbon source. • Despite the inhibition of methanogenesis by DO and nitrate, CH{sub 4} fraction eventually increased. - Abstract: Leachate recirculation for rapid landfill stabilization can result in the accumulation of high-strength ammonium. An on-site sequencing batch reactor (SBR) was therefore, applied to oxidize the ammonium to nitrite, which was then recirculated to the landfill for denitrification to nitrogen gas. At relatively higher ammonium levels, nitrite accumulated well in the SBR; the nitrite was denitrified stably in the landfill, despite an insufficient biodegradable carbon source in the leachate. As the leachate was recirculated, the methane and carbon dioxide contents produced from the landfill fluctuated, implying that the organic acids and hydrogen produced in the acid production phase acted as the carbon source for denitrification in the landfill. Leachate recirculation combined with ex-situ partial nitrification of the leachate may enhance the biodegradation process by: (a) removing the nitrogen that is contained with the leachate, and (b) accelerating landfill stabilization, because the biodegradation efficiency of landfill waste is increased by supplying sufficient moisture and its byproducts are used as the carbon source for denitrification. In addition, partial nitrification using an SBR has advantages for complete denitrification in the landfill, since the available carbon source is in short supply in aged landfills.