Literatura académica sobre el tema "Via-nitrite processes"
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Artículos de revistas sobre el tema "Via-nitrite processes"
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Barat, R., J. Serralta, M. V. Ruano, E. Jiménez, J. Ribes, A. Seco y J. Ferrer. "Biological Nutrient Removal Model No. 2 (BNRM2): a general model for wastewater treatment plants". Water Science and Technology 67, n.º 7 (1 de abril de 2013): 1481–89. http://dx.doi.org/10.2166/wst.2013.004.
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This paper presents the plant-wide model Biological Nutrient Removal Model No. 2 (BNRM2). Since nitrite was not considered in the BNRM1, and this previous model also failed to accurately simulate the anaerobic digestion because precipitation processes were not considered, an extension of BNRM1 has been developed. This extension comprises all the components and processes required to simulate nitrogen removal via nitrite and the formation of the solids most likely to precipitate in anaerobic digesters. The solids considered in BNRM2 are: struvite, amorphous calcium phosphate, hidroxyapatite, newberite, vivianite, strengite, variscite, and calcium carbonate. With regard to nitrogen removal via nitrite, apart from nitrite oxidizing bacteria two groups of ammonium oxidizing organisms (AOO) have been considered since different sets of kinetic parameters have been reported for the AOO present in activated sludge systems and SHARON (Single reactor system for High activity Ammonium Removal Over Nitrite) reactors. Due to the new processes considered, BNRM2 allows an accurate prediction of wastewater treatment plant performance in wider environmental and operating conditions.
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Pijuan, M., L. Ye y Z. Yuan. "Could nitrite/free nitrous acid favour GAOs over PAOs in enhanced biological phosphorus removal systems?" Water Science and Technology 63, n.º 2 (1 de enero de 2011): 345–51. http://dx.doi.org/10.2166/wst.2011.062.
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Enhanced biological phosphorus removal (EBPR) normally occurs together with nitrogen removal in wastewater treatment plants (WWTPs). In recent years, efforts have been devoted to remove nitrogen via the nitrite pathway (oxidation of ammonia to nitrite and reduction of nitrite to nitrogen gas without going through nitrate), reducing the requirement for carbon and oxygen in the plant. However nitrite and free nitrous acid (FNA), the protonated species of nitrite, have been shown to cause EBPR deterioration under certain concentrations. This study provides a direct comparison between the different levels of FNA inhibition in the aerobic processes of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) by reviewing the studies published in this area. Also, new data is presented assessing the FNA effect on the anaerobic metabolism of these two groups of bacteria. Overall, FNA has shown inhibitory effects on most of the processes involved in the metabolism of PAOs and GAOs. However, the inhibition-initiation levels are different between different processes and, even more importantly between the two groups. In general, PAOs appear to be more affected than GAOs at the same level of FNA, thus giving GAOs competitive advantage over PAOs in EBPR systems when nitrite is present.
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Pambrun, V., E. Paul y M. Spérandio. "Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes". Water Science and Technology 50, n.º 6 (1 de septiembre de 2004): 269–76. http://dx.doi.org/10.2166/wst.2004.0385.
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Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30°C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2−/gN-NH4+, and 0.4gN-NO2−/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.
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Guieysse, B., M. Plouviez, M. Coilhac y L. Cazali. "Nitrous oxide (N<sub>2</sub>O) production in axenic <i>Chlorella vulgaris</i> cultures: evidence, putative pathways, and potential environmental impacts". Biogeosciences Discussions 10, n.º 6 (17 de junio de 2013): 9739–63. http://dx.doi.org/10.5194/bgd-10-9739-2013.
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Abstract. Using antibiotic assays and genomic analysis, this study demonstrates nitrous oxide (N2O) is generated from axenic C. vulgaris cultures. In batch assays, this production is magnified under conditions favoring intracellular nitrite accumulation, but repressed when nitrate reductase (NR) activity is inhibited. These observations suggest N2O formation in C. vulgaris might proceed via NR-mediated nitrite reduction into nitric oxide (NO) acting as N2O precursor via a pathway similar to N2O formation in bacterial denitrifiers, although NO reduction to N2O under oxia remains unproven in plant cells. Alternatively, NR may reduce nitrite to nitroxyl (HNO), the latter being known to dimerize to N2O under oxia. Regardless of the precursor considered, an NR-mediated nitrite reduction pathway provides a unifying explanation for correlations reported between N2O emissions from algae-based ecosystems and NR activity, nitrate concentration, nitrite concentration, and photosynthesis repression. Moreover, these results indicate microalgae-mediated N2O formation might significantly contribute to N2O emissions in algae-based ecosystems. These findings have profound implications for the life cycle analysis of algae biotechnologies and our understanding of the global biogeochemical nitrogen cycle.
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Bristow, Laura A., Tage Dalsgaard, Laura Tiano, Daniel B. Mills, Anthony D. Bertagnolli, Jody J. Wright, Steven J. Hallam et al. "Ammonium and nitrite oxidation at nanomolar oxygen concentrations in oxygen minimum zone waters". Proceedings of the National Academy of Sciences 113, n.º 38 (6 de septiembre de 2016): 10601–6. http://dx.doi.org/10.1073/pnas.1600359113.
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A major percentage of fixed nitrogen (N) loss in the oceans occurs within nitrite-rich oxygen minimum zones (OMZs) via denitrification and anammox. It remains unclear to what extent ammonium and nitrite oxidation co-occur, either supplying or competing for substrates involved in nitrogen loss in the OMZ core. Assessment of the oxygen (O2) sensitivity of these processes down to the O2concentrations present in the OMZ core (<10 nmol⋅L−1) is therefore essential for understanding and modeling nitrogen loss in OMZs. We determined rates of ammonium and nitrite oxidation in the seasonal OMZ off Concepcion, Chile at manipulated O2levels between 5 nmol⋅L−1and 20 μmol⋅L−1. Rates of both processes were detectable in the low nanomolar range (5–33 nmol⋅L−1O2), but demonstrated a strong dependence on O2concentrations with apparent half-saturation constants (Kms) of 333 ± 130 nmol⋅L−1O2for ammonium oxidation and 778 ± 168 nmol⋅L−1O2for nitrite oxidation assuming one-component Michaelis–Menten kinetics. Nitrite oxidation rates, however, were better described with a two-component Michaelis–Menten model, indicating a high-affinity component with aKmof just a few nanomolar. As the communities of ammonium and nitrite oxidizers were similar to other OMZs, these kinetics should apply across OMZ systems. The high O2affinities imply that ammonium and nitrite oxidation can occur within the OMZ core whenever O2is supplied, for example, by episodic intrusions. These processes therefore compete with anammox and denitrification for ammonium and nitrite, thereby exerting an important control over nitrogen loss.
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Caballero, Antonio, Abraham Esteve-Núñez, Gerben J. Zylstra y Juan L. Ramos. "Assimilation of Nitrogen from Nitrite and Trinitrotoluene in Pseudomonas putida JLR11". Journal of Bacteriology 187, n.º 1 (1 de enero de 2005): 396–99. http://dx.doi.org/10.1128/jb.187.1.396-399.2005.
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ABSTRACT Pseudomonas putida JLR11 releases nitrogen from the 2,4,6-trinitrotoluene (TNT) ring as nitrite or ammonium. These processes can occur simultaneously, as shown by the observation that a nasB mutant impaired in the reduction of nitrite to ammonium grew at a slower rate than the parental strain. Nitrogen from TNT is assimilated via the glutamine syntethase-glutamate synthase (GS-GOGAT) pathway, as evidenced by the inability of GOGAT mutants to use TNT. This pathway is also used to assimilate ammonium from reduced nitrate and nitrite. Three mutants that had insertions in ntrC, nasT, and cnmA, which encode regulatory proteins, failed to grow on nitrite but grew on TNT, although slower than the wild type.
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Guieysse, B., M. Plouviez, M. Coilhac y L. Cazali. "Nitrous Oxide (N<sub>2</sub>O) production in axenic <i>Chlorella vulgaris</i> microalgae cultures: evidence, putative pathways, and potential environmental impacts". Biogeosciences 10, n.º 10 (25 de octubre de 2013): 6737–46. http://dx.doi.org/10.5194/bg-10-6737-2013.
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Abstract. Using antibiotic assays and genomic analysis, this study demonstrates nitrous oxide (N2O) is generated from axenic Chlorella vulgaris cultures. In batch assays, this production is magnified under conditions favouring intracellular nitrite accumulation, but repressed when nitrate reductase (NR) activity is inhibited. These observations suggest N2O formation in C. vulgaris might proceed via NR-mediated nitrite reduction into nitric oxide (NO) acting as N2O precursor via a pathway similar to N2O formation in bacterial denitrifiers, although NO reduction to N2O under oxia remains unproven in plant cells. Alternatively, NR may reduce nitrite to nitroxyl (HNO), the latter being known to dimerize to N2O under oxia. Regardless of the precursor considered, an NR-mediated nitrite reduction pathway provides a unifying explanation for correlations reported between N2O emissions from algae-based ecosystems and NR activity, nitrate concentration, nitrite concentration, and photosynthesis repression. Moreover, these results indicate microalgae-mediated N2O formation might significantly contribute to N2O emissions in algae-based ecosystems (e.g. 1.38–10.1 kg N2O-N ha−1 yr−1 in a 0.25 m deep raceway pond operated under Mediterranean climatic conditions). These findings have profound implications for the life cycle analysis of algae biotechnologies and our understanding of the global biogeochemical nitrogen cycle.
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Mascarenhas, Romila, Zhu Li, Carmen Gherasim, Markus Ruetz y Ruma Banerjee. "The human B12 trafficking protein CblC processes nitrocobalamin". Journal of Biological Chemistry 295, n.º 28 (26 de mayo de 2020): 9630–40. http://dx.doi.org/10.1074/jbc.ra120.014094.
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In humans, cobalamin or vitamin B12 is delivered to two target enzymes via a complex intracellular trafficking pathway comprising transporters and chaperones. CblC (or MMACHC) is a processing chaperone that catalyzes an early step in this trafficking pathway. CblC removes the upper axial ligand of cobalamin derivatives, forming an intermediate in the pathway that is subsequently converted to the active cofactor derivatives. Mutations in the cblC gene lead to methylmalonic aciduria and homocystinuria. Here, we report that nitrosylcobalamin (NOCbl), which was developed as an antiproliferative reagent, and is purported to cause cell death by virtue of releasing nitric oxide, is highly unstable in air and is rapidly oxidized to nitrocobalamin (NO2Cbl). We demonstrate that CblC catalyzes the GSH-dependent denitration of NO2Cbl forming 5-coordinate cob(II)alamin, which had one of two fates. It could be oxidized to aquo-cob(III)alamin or enter a futile thiol oxidase cycle forming GSH disulfide. Arg-161 in the active site of CblC suppressed the NO2Cbl-dependent thiol oxidase activity, whereas the disease-associated R161G variant stabilized cob(II)alamin and promoted futile cycling. We also report that CblC exhibits nitrite reductase activity, converting cob(I)alamin and nitrite to NOCbl. Finally, the denitration activity of CblC supported cell proliferation in the presence of NO2Cbl, which can serve as a cobalamin source. The newly described nitrite reductase and denitration activities of CblC extend its catalytic versatility, adding to its known decyanation and dealkylation activities. In summary, upon exposure to air, NOCbl is rapidly converted to NO2Cbl, which is a substrate for the B12 trafficking enzyme CblC.
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Jacob, Juliane, Tina Sanders y Kirstin Dähnke. "Nitrite consumption and associated isotope changes during a river flood event". Biogeosciences 13, n.º 19 (11 de octubre de 2016): 5649–59. http://dx.doi.org/10.5194/bg-13-5649-2016.
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Abstract. In oceans, estuaries, and rivers, nitrification is an important nitrate source, and stable isotopes of nitrate are often used to investigate recycling processes (e.g. remineralisation, nitrification) in the water column. Nitrification is a two-step process, where ammonia is oxidised via nitrite to nitrate. Nitrite usually does not accumulate in natural environments, which makes it difficult to study the single isotope effect of ammonia oxidation or nitrite oxidation in natural systems. However, during an exceptional flood in the Elbe River in June 2013, we found a unique co-occurrence of ammonium, nitrite, and nitrate in the water column, returning towards normal summer conditions within 1 week. Over the course of the flood, we analysed the evolution of δ15N–NH4+ and δ15N–NO2− in the Elbe River. In concert with changes in suspended particulate matter (SPM) and δ15N SPM, as well as nitrate concentration, δ15N–NO3− and δ18O–NO3−, we calculated apparent isotope effects during net nitrite and nitrate consumption. During the flood event, > 97 % of total reactive nitrogen was nitrate, which was leached from the catchment area and appeared to be subject to assimilation. Ammonium and nitrite concentrations increased to 3.4 and 4.4 µmol L−1, respectively, likely due to remineralisation, nitrification, and denitrification in the water column. δ15N–NH4+ values increased up to 12 ‰, and δ15N–NO2− ranged from −8.0 to −14.2 ‰. Based on this, we calculated an apparent isotope effect 15ε of −10.0 ± 0.1 ‰ during net nitrite consumption, as well as an isotope effect 15ε of −4.0 ± 0.1 ‰ and 18ε of −5.3 ± 0.1 ‰ during net nitrate consumption. On the basis of the observed nitrite isotope changes, we evaluated different nitrite uptake processes in a simple box model. We found that a regime of combined riparian denitrification and 22 to 36 % nitrification fits best with measured data for the nitrite concentration decrease and isotope increase.
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Alvarino, Teresa, Evina Katsou, Simos Malamis, Sonia Suarez, Francisco Omil y Francesco Fatone. "Inhibition of biomass activity in the via nitrite nitrogen removal processes by veterinary pharmaceuticals". Bioresource Technology 152 (enero de 2014): 477–83. http://dx.doi.org/10.1016/j.biortech.2013.10.107.
Texto completoTesis sobre el tema "Via-nitrite processes"
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SPINELLI, MATTEO. "Studio del processo biologico via nitrito applicato a reflui a basso carico di azoto". Doctoral thesis, Università Politecnica delle Marche, 2018. http://hdl.handle.net/11566/252879.
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La crescente attenzione per la ricerca di nuovi processi di trattamento delle acque reflue persegue l’obbiettivo di combinare il raggiungimento di alti standard di qualità nell’effluente, la riduzione dei inquinanti rilasciati direttamente o indirettamente nell’atmosfera e il recupero di energia e di preziose materie prime dalle acque di scarico. Le prestazioni del processo via nitrito per il trattamento di reflui a basso contenuto di azoto sono state valutate su un pilota da 3 m3, alimentato con acqua reflua reale di origine urbana, al fine di comprendere i meccanismi che favoriscono l’avvio e la stabilità del processo. Studiando selettivamente la combinazione dei diversi parametri in gioco si è cercato di evidenziare quelli che maggiormente incidono sulle prestazioni del processo, cercando di velocizzare la fase di startup e ridurre progressivamente il dosaggio dei reagenti esterni necessari per il condizionamento della biomassa. La sperimentazione è stata suddivisa in tre parti, ognuna corrispondente a una configurazione di lavoro diversa. Ogni configurazione è stata preceduta da studi preliminari in laboratorio per poi passare alla validazione dei risultati ottenuti in scala dimostrativa. Inoltre, durante le fasi in scala pilota, attraverso il monitoraggio in continuo delle emissioni gassose si è cercato di comprendere i meccanismi di formazione e rilascio in atmosfera degli off-gasses, incentrando l’attenzione soprattutto sul protossido di azoto (N2O). Attraverso il monitoraggio delle costanti cinetiche si è messa in luce una notevole differenza di efficacia delle prestazioni in funzione della strategia d’inibizione adottata, passando da un processo stabilmente sopra al 90% via nitrito nella configurazione iniziale a percentuali intorno al 10% durante il condizionamento sull’influente. Le condizioni applicate per l’inibizione dei batteri nitrificanti e il lungo mantenimento delle condizioni di inibizione della biomassa ha permesso di ottenere una notevole crescita delle velocità di nitritazione permettendo di raggiungere un notevole decremento in termini di protossido di azoto rilasciato.The growing attention to the research of new wastewater treatment processes pursues the objective of combine the achievement of high quality standards in the effluent, the reduction of pollutants released directly or indirectly into the atmosphere and the recovery of energy and precious raw materials from wastewater. The performances of the via nitrite process for the treatment of low strength of nitrogen wastewater was evaluated on a 3 m3 pilot plant, fed with real urban wastewater, in order to understand the mechanisms that promote the start-up and stability of the process. Studying selectively the combination of the different parameters involved, we tried to highlight those that most affect the performance of the process, trying to speed up the start-up phase and progressively reduce the dosage of the external reagents needed for the biomass conditioning. The experimentation was divided in three parts, each corresponding to a different work configuration. Each configuration was preceded by preliminary studies in the laboratory and then the results obtained were validated on the demonstrative scale. Moreover, during the pilot scale phases, through the continuous monitoring of gaseous emissions, we tried to understand the mechanisms of formation and release into the atmosphere of off-gasses, focusing the attention on nitrous oxide (N2O). Through the monitoring of the kinetic constants, a considerable difference in terms of performance has been highlighted according to the inhibition strategy adopted, moving from a stable 90% via nitrite process in the initial configuration to around 10% during the conditioning of the influent flow. The conditions applied for the inhibition of nitrifying bacteria and the long maintenance of the biomass inhibition have allowed a remarkable increase in nitrite speeds, allowing a considerable decrease in the amount of nitrous oxide released.
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Conca, Vincenzo. "Scale-up of Innovative and Sustainable via-Nitrite Biological Processes for Resource Recovery in Existing Wastewater Treatment Plants". Doctoral thesis, 2021. http://hdl.handle.net/11562/1042911.
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Over the last years, the transition from wastewater treatment plants to water resource recovery facilities has gained a lot of attention. The aim of these thesis was the deep investigation of novel via-nitrite bioprocesses for the integration of via-nitrite nitrogen and phosphorus removal from the sludge reject water with resource recovery such as nutrients, chemical precursors and high added-value bioproducts. The biological via-nitrite nitrogen and phosphorus removal from the sludge reject water through the S.C.E.N.A. process was investigated in a full-scale sequencing batch reactor (SBR) with a volume of 70 m3 located in Carbonera WWTP. Fermentation yields showed values in the range of 0.16-0.26 g CODVFA/gVSfed, while nitrogen mass balances showed that around 28-30 kg N per day were removed. At the same time, phosphorus was efficiently removed biologically, resulting in a phosphorus concentration in the sludge up to 39.7 mg P/kg TS and a daily phosphorus recovery of 1.21 kg P/day. The phosphorus-rich sludge was tested in real field and the results showed that the utilization of P-rich sludge led to similar effects on plant growth and quality parameters with respect to inorganic fertilizers. The combination of cellulosic primary sludge recovery by wastewater micro-sieving with production of bio-based volatile fatty acids in a pilot-scale platform was evaluated. The rotating belt filter allowed to separate around 50% of solids. The potential production of bio-based volatile fatty acids without pH control was 232 mgCOD/gVS and the yields further improved adjusting the initial pH to value of 9 (521 mgCOD/gVS). Semi-continuous reactor (2.6 m3) was employed and the acids production using a hydraulic retention time of 6 days was around 154 mgCOD/gVS. Conditioning primary cellulosic sludge to pH 9 enhanced volatile fatty acid production to 322 mgCOD/gVS. The utilization of the fermentation liquid fraction as carbon source for nutrients removal would reduce significantly the cost for external carbon source, while the biopolymer production would enhance the benefit from 72 to 186 €/ton TS of recovered sludge. The polyhydroxyalkanoates (PHAs) production integrated with the via-nitrite nitrogen removal from anaerobic reject water was investigated at pilot scale under long term period. Results showed that around 80% of the influent ammonia was efficiently removed by the system when both nitritation and selection SBR operated with volumetric nitrogen loading rate (vNLR) of 1.64-1.72 kgN/m3 d and 0.60-0.63 kgN/m3 d. Accumulation tests showed PHA yields ranging between 0.58 and 0.61 g CODPHA/g CODVFA, indicating an effective selection strategy. The integration of nitrogen removal and PHA production in the sidestream resulted in a methane recovery up to 4.0 m3CH4/PE y and a maximal PHA production of 1.2 kgPHA/PE y with a potential revenue for the WWTP up to 6.5 €/PE y. Data Analytics was deployed to predict the dissolved nitrous oxide (N2O) concentration in a full-scale sidestream sequence batch reactor (SBR) treating the sludge reject water. On average, the N2O emissions were equal to 7.6% of the NH4-N load and can contribute up to 97 % to the operational carbon footprint of the studied bioprocess. The results of the study revealed that the aerobic dissolved N2O concentration was correlated with the drop of average aerobic conductivity rate, the DO and the changes of conductivity between sequential cycles. Additionally, the analysis showed that N2O was always consumed after the depletion of NO2- during denitritation (after the “nitrite knee”). Based on these findings SVM classifiers were constructed to predict whether dissolved N2O will be consumed during the anoxic and anaerobic phases. The proposed approach accurately predicted the N2O emissions as a latent parameter from other low-cost sensors that are traditionally deployed in biological batch processes.
Libros sobre el tema "Via-nitrite processes"
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Kirchman, David L. The nitrogen cycle. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0012.
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Nitrogen is required for the biosynthesis of many cellular components and can take on many oxidation states, ranging from −3 to +5. Consequently, nitrogen compounds can act as either electron donors (chemolithotrophy) or electron acceptors (anaerobic respiration). The nitrogen cycle starts with nitrogen fixation, the reduction of nitrogen gas to ammonium. Nitrogen fixation is carried out only by prokaryotes, mainly some cyanobacteria and heterotrophic bacteria. The ammonium resulting from nitrogen fixation is quickly used by many organisms for biosynthesis, being preferred over nitrate as a nitrogen source. It is also oxidized aerobically by chemolithoautotrophic bacteria and archaea during the first step of nitrification. The second step, nitrite oxidation, is carried out by other bacteria not involved in ammonia oxidation, resulting in the formation of nitrate. Some bacteria are capable of carrying out both steps (“comammox”). This nitrate can then be reduced to nitrogen gas or nitrous oxide during denitrification. It can be reduced to ammonium, a process called “dissimilatory nitrate reduction to ammonium.” Nitrogen gas is also released by anaerobic oxidation of ammonium (“anammox”) which is carried out by bacteria in the Planctomycetes phylum. The theoretical contribution of anammox to total nitrogen gas release is 29%, but the actual contribution varies greatly. Another gas in the nitrogen cycle, nitrous oxide, is a greenhouse gas produced by ammonia-oxidizing bacteria and archaea. The available data indicate that the global nitrogen cycle is in balance, with losses from nitrogen gas production equaling gains via nitrogen fixation. But excess nitrogen from fertilizers is contributing to local imbalances and several environmental problems in drinking waters, reservoirs, lakes, and coastal oceans.
Actas de conferencias sobre el tema "Via-nitrite processes"
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Li, Lingyun, Yongzhen Peng, Lei Wu, Shuying Wang y Lun Li. "Rapid Achievement of Nitrogen Removal via Nitrite and Nitrifying Communities Transfer by Process Optimization". En 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5163279.
Texto completoInformes sobre el tema "Via-nitrite processes"
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Van Rijn, Jaap, Harold Schreier y Yossi Tal. Anaerobic ammonia oxidation as a novel approach for water treatment in marine and freshwater aquaculture recirculating systems. United States Department of Agriculture, diciembre de 2006. http://dx.doi.org/10.32747/2006.7696511.bard.
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Ammonia waste removal in recirculating aquaculture systems is typically accomplished via the action of nitrifying bacteria in specially designed biofilters that oxidize ammonia to produce nitrate. In the majority of these systems nitrate is discharged to the environment through frequent water exchanges. As environmental considerations have made it necessary to eliminate nitrate release, new strategies for nitrate consumption are being developed. In the funding period we showed that ammonia removal from wastewater could take place by an anaerobic ammonia oxidation process carried out by bacterial Planctomycetessp. Referred to as “anammox”, this process occurs in the absence of an organic source and in the presence of nitrite (or nitrate) as an electron acceptor as follows: NH₃ + HNO₂ -> N₂ + 2H₂O. Annamox has been estimated to result in savings of up to 90% of the costs associated with was wastewater treatment plants. Our objective was to study the applicability of the anammox process in a variety of recirculating aquaculture systems to determine optimal conditions necessary for efficient ammonia waste removal. Both seawater and freshwater systems operated with either conventional aerobic treatment of ammonia to nitrate (USA) or, in addition, denitrifying biofilters as well as anaerobic digestion of sludge (Israel) were tested. Molecular tools were used to screen and monitor different treatment compartments for the presence of Planctomycetes. Optimal conditions for the enrichment of the anammox bacteria were tested using laboratory scale biofilters as well as a semi-commercial system. Enrichment studies resulted in the isolation of some unique heterotrophic bacteria capable of plasmid-mediated autotrophic growth in the presence of ammonia and nitrite. Our studies have not only demonstrated the presence and viability of Planctomycetes spp. in recirculating marine and freshwater systems biofilter units but also demonstrated the applicability of the anammox process in these systems. Using our results we have developed treatment schemes that have allowed for optimizing the anammox process and applying it to recirculating systems.
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Desiderati, Christopher. Carli Creek Regional Water Quality Project: Assessing Water Quality Improvement at an Urban Stormwater Constructed Wetland. Portland State University, 2022. http://dx.doi.org/10.15760/mem.78.
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Stormwater management is an ongoing challenge in the United States and the world at-large. As state and municipal agencies grapple with conflicting interests like encouraging land development, complying with permits to control stormwater discharges, “urban stream syndrome” effects, and charges to steward natural resources for the long-term, some agencies may turn to constructed wetlands (CWs) as aesthetically pleasing and functional natural analogs for attenuating pollution delivered by stormwater runoff to rivers and streams. Constructed wetlands retain pollutants via common physical, physicochemical, and biological principles such as settling, adsorption, or plant and algae uptake. The efficacy of constructed wetlands for pollutant attenuation varies depending on many factors such as flow rate, pollutant loading, maintenance practices, and design features. In 2018, the culmination of efforts by Clackamas Water Environment Services and others led to the opening of the Carli Creek Water Quality Project, a 15-acre constructed wetland adjacent to Carli Creek, a small, 3500-ft tributary of the Clackamas River in Clackamas County, OR. The combined creek and constructed wetland drain an industrialized, 438-acre, impervious catchment. The wetland consists of a linear series of a detention pond and three bioretention treatment cells, contributing a combined 1.8 acres of treatment area (a 1:243 ratio with the catchment) and 3.3 acre-feet of total runoff storage. In this study, raw pollutant concentrations in runoff were evaluated against International Stormwater BMP database benchmarks and Oregon Water Quality Criteria. Concentration and mass-based reductions were calculated for 10 specific pollutants and compared to daily precipitation totals from a nearby precipitation station. Mass-based reductions were generally higher for all pollutants, largely due to runoff volume reduction on the treatment terrace. Concentration-based reductions were highly variable, and suggested export of certain pollutants (e.g., ammonia), even when reporting on a mass-basis. Mass load reductions on the terrace for total dissolved solids, nitrate+nitrite, dissolved lead, and dissolved copper were 43.3 ± 10%, 41.9 ± 10%, 36.6 ± 13%, and 43.2 ± 16%, respectively. E. coli saw log-reductions ranging from -1.3 — 3.0 on the terrace, and -1.0 — 1.8 in the creek. Oregon Water Quality Criteria were consistently met at the two in-stream sites on Carli Creek for E. coli with one exception, and for dissolved cadmium, lead, zinc, and copper (with one exception for copper). However, dissolved total solids at the downstream Carli Creek site was above the Willamette River guidance value 100 mg/L roughly 71% of the time. The precipitation record during the study was useful for explaining certain pollutant reductions, as several mechanisms are driven by physical processes, however it was not definitive. The historic rain/snow/ice event in mid-February 2021 appeared to impact mass-based reductions for all metals. Qualitatively, precipitation seemed to have the largest effect on nutrient dynamics, specifically ammonia-nitrogen. Determining exact mechanisms of pollutant removals was outside the scope of this study. An improved flow record, more targeted storm sampling, or more comprehensive nutrient profiles could aid in answering important questions on dominant mechanisms of this new constructed wetland. This study is useful in establishing a framework and baseline for understanding this one-of-a-kind regional stormwater treatment project and pursuing further questions in the future.