Le procédé à biofilm R3F / MBBR est une technologie récente en France qui vient s'ajouter à la gamme des procédés biologiques de traitement de la matière organique et azotée des eaux usées. Sa valeur ajoutée repose sur sa compacité grâce au développement d'une quantité importante de biomasse bactérienne dans un ouvrage à emprise au sol faible. Ainsi, le procédé R3F / MBBR s'avère être une solution intéressante pour le traitement de l'azote dans un contexte de contrainte foncière importante. Le principe de la technologie est l'emploi de biomédias, supports plastiques de quelques centimètres, sur lesquels un biofilm bactérien se développe. Ces biomédias sont mis en suspension dans le réacteur par insufflation d'air ou par brassage mécanique. Aujourd'hui, la modélisation est devenue un outil précieux d'aide au dimensionnement. S'il existe beaucoup de modèles de biofilm aujourd'hui, peu de travaux de recherche ont abouti à l'élaboration d'un modèle dynamique R3F / MBBR à destination de l'ingénierie et capable de simuler le procédé en conditions réelles. Ainsi, l'objectif principal de cette thèse est la construction d'un modèle dynamique utilisable en ingénierie. La validation d'un tel modèle avec des données de terrain n'ayant pas encore été faite, ce point constituera une originalité. Pour ce faire, le fonctionnement d'une unité pilote R3F alimentée par des eaux résiduaires urbaines a été étudié. Le suivi du pilote pendant près de 2 ans en régime pseudo-permanent a d'abord permis d'évaluer les performances de 3 biomédias, travail là encore jamais réalisé. Ensuite, le régime dynamique, par l'application d'à-coups de charge hydraulique à une charge surfacique appliquée donnée, a été étudié. Une campagne de mesure intensive pendant une période de 4 jours en régime dynamique a servi de base pour le calage du modèle. Une période de 30 jours en régime pseudo-permanent a servi de base pour la validation du modèle.Ce travail de modélisation a abouti à l'élaboration d'un protocole de calage qui informe des paramètres à mesurer, et à modifier pour obtenir un modèle dynamique du procédé R3F / MBBR capable de simuler son fonctionnement en conditions réelles. Des protocoles de mesure ont également été élaborés pour estimer la valeur des paramètres à mesurer. Des simulations prédictives réalisées avec le modèle nouvellement calé ont ensuite permis d'évaluer le procédé dans de nouvelles conditions de fonctionnement. Une étude critique du modèle a abouti à la détermination de faiblesses qui limitent la qualité des simulations. Pour ces faiblesses, des propositions d'amélioration ont été apportées. / The R3F / MBBR biofilm process is a relatively recent technology in France able to treat organic and nitrogen matters from domestic wastewaters. Its advantage is its compactness due to the development of a significant quantity of bacterial biomass in a tank with low surface area. Thus, the R3F / MBBR process is a relevant solution for nitrogen treatment in a difficult property context. The principle of this technology is the plastic carriers of few centimeters use, on which a bacterial biofilm grows. These carriers freely move in the tank thanks to a air flow rate or a mixing. Nowadays, modeling has become a relevant tool for design. Lots of biofilm models exist but few research works have led to the carrying out of a R3F / MBBR dynamic model for engineering and able to simulate the process in real conditions. Thus, the principal objective of this thesis is the achievement of a R3F / MBBR dynamic model useful in engineering. The validation of such a model with experimental measurements has never been carried out and will represent an original point. The operating of a R3F pilot-scale wastewater plant fed with domestic wastewater has been studied. The follow-up of the pilot-scale unit, during almost 2 years, has first allowed evaluating the performances of 3 carriers in steady state, a work that has never been achieved. Then, the dynamic state has been studied in applying peak-loads but conserving the daily loading. During 4 days, an intensive measurement campaign in dynamic state has been used to calibrate the model. Another 30 days in steady state has been used to validate the model. This modeling work has led to a calibration protocol which informs about the parameters to measure, and to adjust in order to obtain a R3F / MBBR dynamical model able to simulate its operating in real conditions. Some measurement protocols have also been created to estimate the value of parameters to measure. Some predictive simulations carried out with the calibrated model have then allowed assessing the process in new operating conditions. A critical study of the model has led to the identification of some weaknesses which limit the quality of simulations. Thus, propositions to enhance the model have been brought.

Le cycle océanique de l'azote est à l'origine de deux rétro-actions climatiques au sein du système terre. D'unepart, il participe au contrôle du réservoir d'azote fixé disponible au développement du phytoplancton et à lamodulation de la pompe biologique, un des mécanismes de séquestration du carbone anthropique. D'autre part,le cycle de l'azote produit un gaz à effet de serre et destructuer d'ozone, le protoxyde d'azote (N2O). L'évolutionfuture du cycle de l'azote sous l'influence du rechauffement climatique, de la déoxygénation et de l'acidificationdes océans reste une question ouverte. Les processus tels que la fixation d'azote, la dénitrification et laproduction de protoxyde d'azote seront modifiés sous l'influence conjuguée des ces trois stresseurs. Cesinteractions peuvent être évaluées grâce aux modèles globaux de biogéochimie marine. Nous utilisons NEMOPISCESet l'ensemble des modèles CMIP5 pour projeter les modifications des taux de fixation d'azote, denitrification, de production et des flux air-mer de N2O à l'horizon de 2100 en réponse au scénario 'business-asusual'.Les effets liés à l'action combinée du rechauffement climatique et de l'acidification des océans sur leréservoir d'azote fixé, la production primaire et la rétro-action sur le bilan radiatif sont également évalués danscette thèse.! / The marine nitrogen cycle is responsible for two climate feedbacks in the Earth System. Firstly, it modulates thefixed nitrogen pool available for phytoplankton growth and hence it modulates in part the strength of thebiological pump, one of the mechanisms contributing to the oceanic uptake of anthropogenic CO2. Secondly, thenitrogen cycle produces a powerful greenhouse gas and ozone (O3) depletion agent called nitrous oxide (N2O).Future changes of the nitrogen cycle in response to global warming, ocean deoxygenation and oceanacidification are largely unknown. Processes such as N2-fixation, nitrification, denitrification and N2Oproduction will experience changes under the simultaneous effect of these three stressors. Global oceanbiogeochemical models allow us to study such interactions. Using NEMO-PISCES and the CMIP5 modelensemble we project changes in year 2100 under the business-as-usual high CO2 emissions scenario in globalscale N2-fixation rates, nitrification rates, N2O production and N2O sea-to-air fluxes adding CO2 sensitivefunctions into the model parameterizations. Second order effects due to the combination of global warming intandem with ocean acidification on the fixed nitrogen pool, primary productivity and N2O radiative forcingfeedbacks are also evaluated in this thesis.

Increasing pressure is being placed on the dairy industry to reduce nitrogen losses from soil. Nitrification inhibitors are a management strategy that could be implemented on dairy farms to help reduce losses of nitrogen. Nitrification inhibitors work by temporarily inhibiting the microbial conversion of soil ammonium to nitrate. Past trials have indicated that nitrification inhibitors can increase grass production and decrease nitrate leaching; however, little is known about the long-term effects on other soil nitrogen processes such as denitrification. Denitrification rates in soils can be limited by the availability of substrate (carbon and nitrate) and by insufficient anaerobic microsites. The objective of this thesis was to establish whether the nitrification inhibitor, dicyandiamide (DCD), could decrease denitrification rates in dairy farm soils by limiting nitrate availability. A field trial was established at Dexcel's research farm near Hamilton, New Zealand on a Typic Orthic Allophanic Soil. Twenty replicated field plots were established in a paddock, ten plots acted as controls and ten plots had DCD applied to the soil once a month at a rate of 30 kg ha-1 yr-1. Denitrification rates were measured using the acetylene inhibition technique on intact soil cores. Ammonium and nitrate concentration, soil carbon availability, denitrifying enzyme activity and soil pH were measured from soil samples collected monthly. Two further field experiments and one laboratory experiment were undertaken. The distribution of denitrifying enzyme activity with soil depth was measured to ensure that the depth to which denitrification was sampled (15 cm) in the field experiment was sufficient. DCD degradation in the field during 20 days was measured to establish how long the effects of DCD might last. A laboratory study investigated whether DCD would decrease denitrifying enzyme activity in soil, when soil conditions were optimized for denitrification. More than 80% of the denitrifying enzyme activity occurred in the top 15 cm of the soil profile, indicating that the depth to which samples were collected was sufficient. There was no significant decrease in denitrification rates in the field experiment when DCD was added. Nitrification was partially inhibited as shown by a significant increase in soil ammonium (+14%) and a significant decline in soil nitrate (-17%) in the DCD-amended soils compared to the control soils. However, the decline in soil nitrate was not great enough for nitrate to limit denitrification. Nitrate concentrations were consistently greater than 5 mg NO3- kg-1 soil (the proposed threshold for declines in denitrification). The laboratory study supported the field study with DCD having no effect on denitrifying enzyme activity and nitrate concentrations remaining above 5 mg NO3- kg-1 soil. So while DCD reduced nitrification rates and the formation of nitrate, denitrification rates were not limited by nitrate availability. DCD was completely degraded in the soil 19 days after DCD application, with a half-life of 2.9 days, which may be a reason for the minor inhibition of nitrification. Denitrifying enzyme activity, carbon availability and soil pH were all unaffected by the application of DCD.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 114-131). Also available on the World Wide Web.

Quaternary ammonium compounds (QACs) are widely used in commercial and consumer applications as disinfectants, fabric softeners, hair conditioners, and emulsifying agents. The massive production and utilization of QACs has led to their extensive discharge into the environment, raising concerns globally. Several studies have reported on potential risks and detrimental effects of QACs on the natural environment and public wastewater treatment plants. Biological treatment has been found to be an effective way to remove QACs and especially aerobic treatment processes can provide rapid biodegradation via a consortium of bacteria. Although extensive research has been conducted on the fate and effect of QACs, relatively little is known about their effect on aerobic biological treatment processes, especially on nitrification. Research was conducted on the fate and effect of alkyl benzyl dimethyl ammonium chloride (AB), a QAC widely used as disinfectant, in mixed aerobic and nitrifying cultures. The results of this study demonstrated that up to 50 mg/L AB was efficiently degraded in a mixed aerobic culture fed with dextrin and peptone, although trace residual AB levels were observed. Nitrification of the produced ammonia was complete at an AB concentration of 20 mg/L after an acclimation period, but was almost completely inhibited at 50 mg/L. Mixed aerobic cultures maintained only with AB as external nitrogen and carbon source achieved a high degree of AB degradation at both 20 and 50 mg/L. Ammonia oxidation by a nitrifying culture, enriched with ammonium chloride and sodium bicarbonate, was inhibited with increasing AB concentration and completely ceased at 15 mg/L AB. Degradation or utilization of AB was not observed for all tested AB concentrations between 2 to 20 mg/L. Based on these experimental results, and assuming non-competitive inhibition, a relatively low value of the AB inhibition coefficient was obtained, which indicates a relatively high susceptibility of the ammonia oxidizers to AB. The results of this study have significant implications for both engineered and natural systems relative to the fate and effect of QACs.

Azospirillum brasilense reduced nitrate in W-containing Mo-limited medium, but at lower rates than in W-free medium. However nitrate reduction by Paracoccus denitrificans was completely suppressed under the same conditions. Nitrite reductase activity of growing A. brasilense was negatively affected by tungstate. Nitrite accumulation was shown to be the result of an inhibitory effect of nitrate on nitrite reductase activity. Both resting whole cell and cell-free extract preformed nitrite reductase activities were equally affected by increasing levels of tungstate. Preformed nitrate reductase activity of the cell-free extract was shown to be more sensitive to increasing concentrations of tungstate than whole cell activity, suggesting that the cytoplasmic membrane served as a protective barrier against tungsten inactivation of nitrate reductase.

Anaerobic digestion (AD) has been shown to be an effective technique for energy recovery and stabilization of livestock wastes, municipal sludges and industrial wastewaters. However, further treatment is required to remove nitrogen from AD effluents to avoid detriments to surface and ground waters. The high free ammonia (FA) concentrations present in AD effluents can inhibit nitrification processes in conventional biological nitrogen removal (BNR) systems. The overall goal of this research was to develop a process for removal of nitrogen from AD swine waste (ADSW) effluent. The proposed solution was to incorporate particulate chabazite, which has a high cation exchange capacity, into a sequencing batch reactor (SBR) to adsorb ammonium and therefore ease nitrification inhibition. The process developed is called a chabazite-SBR. Three research questions were used to guide this research. First question (Chapter 3): How does chabazite pretreatment with groundwater (GW) affect the kinetics and cation exchange capacity during ammonium (NH4+) uptake? Kinetics and isotherm batch tests were performed with GW pretreated chabazite. In addition, sodium chloride (NaCl), and deionized water (DI) pretreated chabazite was included for comparison because these are typically used pretreatment methods. The Ion Exchange (IX) isotherm model was used to calculate the cation exchange capacity and the pseudo-first and film diffusion kinetics models were applied to quantify the effect of the pretreatment on the reaction rate. Results showed that the exchange capacity was slightly higher for GW pretreated chabazite compared with the other common pretreatment strategies; however, the enhancement was not significantly different. The kinetics of NH4+ uptake during the first four hours of contact was significantly improved by GW pretreatment when compared with other common pretreatment strategies. This was caused by an enhancement in film diffusion mechanisms. The findings of this first part of the research were important because it was shown that NaCl pretreatment is not needed to improve the kinetics and cation exchange capacity of chabazite. Second question (Chapter 4): How does addition of chabazite to ADSW centrate affect nitrification rates? Nitrification batch test with varying NH4+ concentrations were performed to identify the inhibitory NH4+ concentration. Additional nitrification batch tests treating real and synthetic waste with initial NH4+ concentration of 1,000 mg-N L-1 with added zeolite were performed. For the mixed liquor tested in this study, NH4+ concentrations must be maintained below 200 mg-N L-1 to relieve nitrification inhibition. Treatment of ADSW centrate requires a chabazite dose of 150 g L-1 to ease FA inhibition of nitrification. The rate of nitrification increased, by approximately a factor of 3, when chabazite was added to a batch reactor treating high NH4+ strength wastewater. However, Na+ release from the chabazite also plays a role in nitrification inhibition. The findings of this part of the research showed the potential for using chabazite for overcoming FA inhibition of nitrification during treatment of high NH4+ strength wastewater. Third question (Chapter 5): How effective is the chabazite-SBR in removing total nitrogen concentrations from ADSW centrate? A chabazite-SBR was operated for 40 weeks (cycles) to study the TN removal efficiency with varying carbon source. The efficiency of IX was also monitored over time. The chabazite-SBR process achieved stable TN removal from ADSW centrate during the 40 weeks of operation. Simultaneous nitrification-denitrification reduced chemical input requirements. Addition of an external organic carbon source at a rate of 3.2 g-COD g-N-1 resulted in maximum TN removal. An overall TN removal efficiency of 84% was achieved, with specific nitrification and denitrification rates of 0.43 and 1.49 mg-N g-VSS-1 hr-1, respectively. The IX stage of the chabazite-SBR was able to reduce FA concentrations to below the inhibitory level for nitrification inhibition over 40 chabazite-SBR cycles with no loss in IX efficiency over time and no fresh zeolite added to the reactor.

Une savane est définie par la coexistence entre des arbres et des Poacées. Dans la savane de Lamto en Côte d’Ivoire, l’espèce dominante de Poacée est connue pour inhiber la nitrification et avant mon étude, l’impact des arbres sur la nitrification était très mal connu. L’étape de la nitrification est conduite par deux différentes communautés, les archées et les bactéries nitrifiantes ayant le gène amoA. Le but de cette étude est de comprendre l’impact de ces deux types de végétaux sur le cycle de l’azote, notamment sur les communautés nitrifiantes et également de comprendre l’impact de la saisonnalité et du passage du feu sur ces processus. Des échantillonnages ont été réalisés sous les Poacées et les arbres à Lamto durant les saisons humides et sèche et également avant et après le passage du feu. Cela a mis en évidence plusieurs effets : (i) les Poacées dominantes de la savane inhibent la nitrification, (ii) les arbres dominants stimulent la nitrification, (iii) les archées nitrifiantes son prédominantes dans cette savane et elles contribueraient majoritairement à la nitrification, (iv) la saisonnalité à un impact direct sur les abondances et l’activité des micro-organismes du sol (l’activité transcriptionelle des archées nitrifiantes diminuent en saison humide), (v) le feu a un effet indirect sur les communautés microbiennes du sol par son impact sur les caractéristiques physico-chimiques des sols, notamment il diminue l’activité des archées nitrifiantes. Enfin, la dénitrification est supérieure sous les arbres que sous les Poacées. Cette étude a permis de mieux comprendre les interactions entres les bactéries et archées nitrifiantes, la végétation et la saisonnalité. / A savanna is defined by the coexistence between trees and grasses. Savannas represent 12-13% of continental surfaces. In the Lamto savanna in Ivory Coast, the dominant grass species inhibits nitrification (the transformation of ammonium into nitrate) and the impact of trees on nitrification before this study was not known. Nitrification is conducted by two different communities. The archaea nitrifiers that have the amoA-AOA gene and bacteria nitrifiers that have the amoA-AOB gene. The aim of this study is to analyse the impacts of both plant types on nitrogen cycling, particularly on the nitrifier communities, and understand the impact of seasonality and fire on these processes. Sampling was conducted under grasses and trees in the Lamto savanna during the wet and dry seasons and also before and after the fire. This study has highlighted for the first time different effects including: (i) the dominant savanna grasses inhibit nitrification, (ii) dominant trees stimulate nitrification, (iii) the archaea nitrifiers are predominant in this savanna and they are mainly responsible for nitrification in this ecosystem, (iv) seasonality has a direct impact on the abundances and activities of soil microorganisms and the wet season reduced archaea nitrifier transcriptional activities, (v) fire has an indirect impact on soil microbial communities due to its impacts on soil physico-chemical characteristics: it decrees the abundance of archaea nitrifiers. In addition, denitrification is higher under trees than grasses. This study permitted to better understand the interactions between nitrifiers, vegetation and seasons.

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