Thèses sur le sujet « Denitrification processe »

A captivating challenge for environmental catalysis is nowadays the rational design of efficient catalysts able to take on the new challenges in energy, economy, and environment sustainability of industrial processes. A catalytic structure must be developed so as to be active, stable, resistant, when working in the presence of poisons (e.g., water, sulphur), but also easily to handle and manage, non-toxic, biocompatible and bioavailable in the view of environment sustainability and circular economy. In this scenario, hydroxyapatite (HAP, Ca10(PO4)6(OH)2) has emerged as bio-material characterized by interesting properties (e.g., thermal/chemical stability, low water solubility, modest morphological properties, and intrinsic amphotericity of surface), which make it a promising support for active metal phases (e.g., Cu, Fe, Mn, Sn), giving rise to heterogeneous catalysts for reactions of industrial chemistry and environment protection. The main scope of this Thesis under the joint supervision between Università degli Studi di Milano (Italy) and Université Claude Bernard Lyon 1 (France) is to develop eco-friendly HAP-based catalysts for environmental reactions devoted to the abatement of nitrogen-containing air pollutants (NOx, NH3, and N2O). During three years of work a commercial bare HAP, coming from the NOVOSOL® process (patented procedure by Solvay), has been at first characterized to assess its applicability as support for innovative eco-friendly catalysts for air-quality protection. The used hydroxyapatite was proven to be a mesoporous, crystalline material characterized by good thermal and chemical stability. Considering that HAP possesses a multifunctional surface, whose acid and basic sites may act as anchoring centres for the immobilization of metal species, it has been properly functionalized with selected metal species, in particular Cu(II) and/or Fe(III), from nitrate precursors in different amount (1 < wt.% Me < 13), according to a wet deposition procedure (contact time of 15 min, 24 h, or 48 h, T = 40°C, calcination at 500°C for 1 h), already reported in previous studies. In this way, different series of metal loaded HAP-catalysts (mono- and bi-metallic) have been obtained, varying some parameters (i.e., metal loading, pH of the Fe-precursor solution, and time of contact between the bare HAP support and the aqueous metal solution) during the preparation. Morphology, structure, acidity, metal speciation and sitting at the HAP surface have been studied through targeted physico-chemical techniques (e.g., N2-physisorption, XRPD, NH3-titration, UV-DR, Mӧssbauer, XP, and EXAFS spectroscopies, CO adsorption at -196°C followed by FT-IR, TEM-EDX) to elucidate the main bulk and surface properties. In general, a complex scenario emerged. The copper- and/or iron-introduction onto HAP did not cause evident modifications in the sample morphology, independently on the metal nature and loading. All the samples were described by mesoporosity and only minor microporosity: they were characterized by surface area values in 60-95 m2·g-1 interval, according to the N2 adsorption/desorption isotherms collected at -196°C. Concerning copper-HAP samples, UV-DRS results indicated that the copper-phase was present in highly dispersed and isolated ions/small nanoclusters onto HAP. However, when the Cu-concentration onto HAP was higher than 6 wt.%, copper-species additionally reacted with phosphate groups at the HAP surface, giving rise to a further Cu-containing crystalline phase (libethenite, JCPDS: 00-036-0404), revealed by XRPD and TEM-EDX. Regarding iron-HAP samples, UV-DRS, Mössbauer and XPS results indicated that both isolated and aggregated Fe-species were present on all the catalyst surfaces. Eventually, the bimetallic samples were characterized by a higher dispersion of metal species than the monometallic counterparts, as revealed by NH3-titrations, TEM-EDX, and XPS analyses. Three environmental reactions have been then selected to abate NOx, NH3, and N2O: NH3-SCR, Selective Catalytic Reduction of NOx by NH3, NH3-SCO, Selective Catalytic Oxidation of NH3, and the catalytic N2O-decomposition reaction. Catalytic tests have been performed in continuous reaction lines equipped with flow reactor and inline instruments (FT-IR and µ-GC) for quantitative analysis of fed/vented gaseous species. The catalytic performances have been studied under ideal and quasi-real feeding, also evaluating the time-on-stream stability, reusability and the resistance to some poisoning species (e.g., sulphur dioxide, alkaline species) of selected samples. Copper-HAP samples have been studied in the NH3-SCR and the N2O-decomposition reaction. The observed catalytic performances under ideal- and quasi-real feeding mixtures suggested that the SCR activity was driven by the Cu-dispersion, as reported for Cu-zeolites. However, the studied Cu-HAP samples were less active than conventional Cu-based systems, even if selectivity to the desired N2 higher than 93% was obtained in the whole temperature range studied. Considering that N2O could be obtained as the undesired by-product due to the unselective NH3 oxidation by O2 for temperatures higher than 400°C in the NH3-SCR, Cu-HAP samples have been additionally studied in the N2O decomposition reaction in the view of their potential use for reducing N2O emissions in post-treatment approaches. The obtained results indicated that Cu-HAP samples can be valid alternatives to some conventional catalytic systems because they require ca. 450°C to efficiently decompose N2O. Differently from what observed in the NH3-SCR, here the catalytic activity was governed by the Cu-Cu distance, according to the reaction mechanism known for Cu-zeolites. Indeed, the most active catalyst possessed dispersed copper-species together with small Cu-aggregates, providing the ideal active sites with the optimal Cu-Cu distance. Iron-HAP catalysts have been tested in the NH3-SCR, NH3-SCO, and N2O-decomposition reactions. They showed modest catalytic performances in the studied reactions, but they remained less active than commercial Fe-based systems. However, they have been studied to evaluate their potentialities for the abatement of gaseous pollutants among the worst of our environment. The obtained results indicated that the studied environmental reactions could be also performed in a single cascade process to achieve the desired zero-emissions goal. For the cascade process, the most promising catalyst among those studied is at an average concentration of Fe (about 6–9 wt.%), to guarantee a surface composed of isolated Fe3+ ions or oligonuclear species that ensure good activity with an equally good selectivity. Eventually, bimetallic copper iron-HAP catalysts have been studied in the NH3-SCR reaction. The obtained results indicated that they were active under both dry/wet feeding, even if they remained less active than conventional bimetallic zeolites. Their activity seemed to be governed by the total metal dispersion, even if, when the catalytic performances of the bimetallic samples were compared with those of the monometallic counterparts, no clear trend of activity was identified due to the fact that the metal-phase could experience different environment, if present alone onto HAP or copresent with another one. To cut a long story short, results obtained in this Thesis enlightened the potential use of hydroxyapatite as promising eco-friendly support for environmental reactions devoted to the abatement of nitrogen-containing air pollutants (NOx, NH3, and N2O). Even if the obtained copper and/or iron hydroxyapatite-based catalysts are not as performant as the commercial catalytic systems, it seems that the suitable route to obtain ever more active and effective HAP-based catalysts is the suitable control of the surface metal distribution onto HAP that is not an easy task. In this context, also in accordance with the positive effects of these innovative HAP-based catalysts on the environment, current investigations are ongoing to develop ever more effective sustainable catalysts for air-quality protection.
Aujourd'hui un défi captivant pour la catalyse environnementale est la conception rationnelle de catalyseurs efficaces capables de relever les nouveaux défis en matière de durabilité énergétique, économique et environnementale des procédés industriels. Une structure catalytique doit être développée de manière à être active, stable, résistante, lorsqu'on travaille en présence de poisons (ex. eau, soufre), mais aussi facilement manipulable et maniable, non toxique, biocompatible et biodisponible dans l'optique de durabilité de l'environnement et économie circulaire. Dans ce scénario, l'hydroxyapatite (HAP, Ca10(PO4)6(OH)2) est apparue comme un biomatériau caractérisé par des propriétés intéressantes (par exemple, stabilité thermique/chimique, faible solubilité dans l'eau, faibles propriétés morphologiques), qui en font un support prometteur pour les phases métalliques actives (ex. Cu, Fe, Mn, Sn), donnant naissance à des catalyseurs hétérogènes pour les réactions de chimie industrielle et de protection de l'environnement. Le principal objectif de cette thèse en cotutelle entre l'Università degli Studi di Milano (Italie) et l'Université Claude Bernard Lyon 1 (France) a été de développer des catalyseurs écologiques à base d’HAP pour les réactions environnementales consacrées à la réduction de polluants de l'air contenant de l'azote (NOx, NH3 et N2O). Pendant trois ans de travail, une HAP commerciale, issue du procédé NOVOSOL® (procédé breveté par Solvay), a d'abord été caractérisée pour évaluer son applicabilité comme support de catalyseurs innovants et respectueux de l'environnement pour la protection de la qualité de l'air. L'hydroxyapatite utilisée s'est avérée être un matériau cristallin et mésoporeux caractérisé par une bonne stabilité thermique et chimique. Considérant que l’HAP possède une surface multifonctionnelle, dont les sites acides et basiques peuvent servir de centre d'ancrage pour l'immobilisation d'espèces métalliques, elle a été correctement fonctionnalisée avec des espèces métalliques sélectionnées, en particulier Cu(II) et/ou Fe(III), à partir de précurseurs de nitrate en quantité différente (1 < wt.% Me < 13), selon une procédure de dépôt par voie humide (temps de contact de 15 min, 24 h ou 48 h, T = 40°C, calcination à 500°C pendant 1 h), déjà rapporté dans de précédentes études. De cette manière, différentes séries de catalyseurs à base d’HAP chargés en métal (mono- et bi-métalliques) ont été préparés, en faisant varier les paramètres suivants: charge en métal, pH de la solution de fer, temps de contact entre le support HAP et la solution précurseur métallique. La morphologie, la structure, l'acidité, la spéciation des métaux et la fonctionalisation à la surface du HAP ont été étudiées par les techniques physico-chimiques suivantes: physisorption d’N2, XRPD, titrage par NH3, spectroscopies UV-DR, Mӧssbauer, XP et EXAFS, adsorption de CO à -196°C suivi par FT-IR et TEM-EDX afin de relier les performances catalytiques aux propriétés texturales, structurales et chimiques des solides préparés. De manière générale, les résultats montrent que l'introduction de cuivre et/ou de fer sur l’HAP ne provoque pas de modifications majeures dans la morphologie des échantillons, indépendamment de la nature du métal et de la charge. Tous les échantillons présentent des isothermes de type mésoporeux avec la présence au début de l’isotherme d’un faible volume microporeux. Les surfaces spécifiques calculées à partir du modèle BET varient entre 60 et 95 m2·g-1. En ce qui concerne les échantillons de cuivre-HAP, les résultats UV-DRS montrent que la phase de cuivre est présente sous de nanoclusters ioniques très bien dispersés et isolés sur l’HAP. Cependant, lorsque la masse de Cu sur l’HAP est supérieure à 6 %, les espèces de cuivre réagisse également avec les groupes phosphate de surface, donnant naissance à une autre phase cristalline contenant du Cu (libethenite, JCPDS: 00-036-0404), détectée par XRPD et TEM-EDX. En ce qui concerne les échantillons de Fe-HAP, les résultats UV-DRS, Mössbauer et XPS montrent que des espèces de Fe isolées et agrégées sont présentes à la surface des catalyseurs. Concernant la caractérisation des systèmes bimétalliques, les résultats montrent une dispersion plus élevée des espèces métalliques que sur les systèmes monométalliques, confirmé par des titrages par NH3 et les analyses TEM-EDX et XPS. Trois réactions environnementales ont ensuite été sélectionnées pour réduire les NOx, NH3 et N2O: la réduction catalytique sélective des NOx par NH3 (NH3-SCR), l’oxydation catalytique sélective d’NH3 (NH3-SCO), et la réaction de décomposition catalytique de l’N2O. Les tests catalytiques ont été effectués en réacteur continu équipé d'un réacteur à lit fixe et d'outils analytiques en ligne (FT-IR et µ-GC) pour l'analyse quantitative des espèces gazeuses alimentées/éventées. Les performances catalytiques ont été étudiées dans des conditions d'alimentation modéles et/ou quasi-réelles, évaluant également la stabilité, la réutilisabilité et la résistance à certaines espèces empoisonnantes (par exemple, le dioxyde de soufre, les espèces alcalines) des échantillons sélectionnés. Les échantillons de cuivre-HAP ont été étudiés dans la NH3-SCR et la réaction de décomposition de l’N2O. Les performances catalytiques observées montrent que l'activité SCR est sensible à la dispersion de Cu, comme indiqué pour les zéolithes de Cu. Cependant, les échantillons de Cu-HAP étudiés se sont révélés moins actifs que les échantillons à base de Cu conventionnels, même si une sélectivité en N2 supérieure à 93% a été obtenue dans toute la gamme de température étudiée. Considérant que le protoxyde d’azote (N2O) peut être formé en tant que sous-produit indésirable en raison de l'oxydation non sélective du NH3 par l'O2 pour des températures supérieures à 400 °C dans la NH3-SCR, des échantillons de Cu-HAP ont également été étudiés dans la réaction de décomposition de N2O en vue de leur utilisation potentielle pour prévenir la formation de N2O dans les systèmes de post-traitement. Les résultats obtenus ont indiqué que les échantillons de Cu-HAP peuvent être des alternatives valables à certains systèmes catalytiques conventionnels car ils nécessitent env. 450°C pour décomposer efficacement N2O. Contrairement à ce qui a été observé dans la NH3-SCR, ici l'activité catalytique était régie par la distance entre deux atomes de cuivre (Cu-Cu), selon le mécanisme de réaction connu pour les zéolithes Cu.8 En effet, le catalyseur le plus actif posséde des espèces de cuivre dispersées avec de petites quantités de Cu agrégées, qui permet d’obtenir une optimisation de la distance Cu-Cu. Les catalyseurs Fe-HAP ont été testés dans les réactions de NH3-SCR, de NH3-SCO et de décomposition d’N2O. Ils ont montré des performances catalytiques modestes dans les réactions étudiées, mais ils sont restés moins actifs que les systèmes commerciaux à base de Fe. Cependant, ils ont été étudiés pour évaluer leurs potentialités pour l'abattement des polluants gazeux parmi les pires de notre environnement. Les résultats obtenus ont indiqué que les réactions environnementales étudiées pouvaient également être effectuées dans un processus en cascade unique pour atteindre l'objectif de zéro émissions. Pour le procédé en cascade, le catalyseur le plus prometteur parmi ceux étudiés présente une concentration moyenne en Fe d’environ 6 à 9 % en poids, générant une surface composée d’ions Fe3+ isolés et d'espèces oligonucléaires assurant une bonne activité et une excellente sélectivité. Finalement, les catalyseurs bimétalliques Cu-Fe-HAP ont été testés dans la réaction de NH3-SCR. Les résultats obtenus indiquent qu'ils sont actifs en absence et en présence de vapeur d’eau dans le milieu réactionnel, même si ils restent moins actifs que les zéolithes bimétalliques conventionnelles. Leur activité semble être gouvernée par la dispersion métallique totale, même si, lorsque les performances catalytiques des échantillons bimétalliques ont été comparés à ceux des homologues monométalliques, aucune tendance claire de l'activité n'a été identifiée en raison du fait que la phase métallique présente un environnement différent (monométallique ou bimétallique). Les résultats obtenus dans ce travail de thèse ont permis de valider le potentiel de l’hydroxyapatite en tant que support écologique prometteur pour les applications dans le domaine de la chimie environnementale et notamment le cas de la réduction des polluants atmosphériques contenant de l'azote (NOx, NH3 et N2O). Même si les catalyseurs à base d'hydroxyapatite de cuivre et/ou de fer obtenus ne sont pas aussi performants que les systèmes catalytiques commerciaux, il semble que la voie appropriée pour obtenir des catalyseurs à base d’HAP toujours plus actifs et efficaces requiert un contrôle précis de la distribution des métaux en surface. Ce n'est pas une tâche facile. Dans ce contexte, également en accord avec les effets positifs de ces catalyseurs innovants à base d’HAP sur l'environnement, des recherches sont en cours pour développer des catalyseurs durables toujours plus efficaces pour la protection de la qualité de l'air.

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The groundwater quality has been compromised as a result of the intensification of human activities over the years. Groundwater contamination by nitrate is one of the effects of this degradation, a socio-environmental problem that affects many regions of the world and particular the city of Natal (RN). Developing techniques for nitrate removal in water is intended to eliminate or reduce the concentration of this compound, and those that involve biological processes have produced economic and environmental advantages. This study proposes a technology for biological removal of nitrate in water supply for humans, using the endocarp s coconut as a carbon source and bacteria support. The experiments were performed in pilot scale anoxic, testing different areas of the substrate surface. Results showed high rates nitrate removal during the monitoring period, noting the occurrence of denitrification after the beginning of system operation. The best performance was achieved in the treatment system containing substrate surface area increased, indicating that the decrease in the endocarp size contributed to increased bacterial activity, improving the ability to remove nitrate. About the quality analyzed aspects of water, it was found that the proposed technology has the potential water use for human consumption
A qualidade da ?gua subterr?nea vem sendo cada vez mais comprometida como consequ?ncia da intensifica??o das a??es antr?picas ao longo dos anos. Um dos efeitos dessa degrada??o ? a contamina??o dos mananciais subterr?neos por nitrato, um problema s?cio-ambiental que atinge diversas regi?es do mundo e, em particular, a cidade do Natal (RN). T?cnicas para remo??o de nitrato em ?guas t?m sido desenvolvidas a fim de eliminar, ou reduzir, a concentra??o deste composto, sendo que, as que envolvem processos biol?gicos t?m apresentado vantagens econ?micas e ambientais. Esse estudo prop?e uma tecnologia de remo??o biol?gica do nitrato em ?gua de abastecimento humano, utilizando o endocarpo de coco como fonte de carbono e suporte bacteriano. Os experimentos foram realizados em c?maras an?xicas em escala piloto, testando diferentes ?reas superficiais do substrato. Os resultados mostraram elevadas taxas de remo??o de nitrato ao longo do per?odo de monitoramento, observando a ocorr?ncia da desnitrifica??o logo ap?s o in?cio do funcionamento do sistema. O melhor desempenho foi alcan?ado no sistema de tratamento contendo substrato de maior ?rea superficial, indicando que a diminui??o no tamanho do endocarpo contribuiu com o aumento da atividade bacteriana, melhorando a capacidade de remo??o de nitrato. Quanto ? qualidade da ?gua analisada, verificou-se que a tecnologia proposta tem potencialidade de uso da ?gua para consumo humano

Aerobic denitrification is a biological nitrogen removal process in which nitrification and denitrification occur simultaneously (in the same reactor) under identical environmental conditions. This contrasts to traditional separate stage nitrification denitrification in which the nitrification and denitrification processes occur sequentially in different reactors under opposing environmental conditions. While aerobic denitrification has long been identified in other ecosystems (such as the nitrogen cycle within soil) it was not thought possible within wastewater treatment processes. The existence of aerobic denitrification within wastewater treatment systems was first identified in the early 1980's following nitrogen mass balances that suggested unexplained nitrogen losses were occurring in the aeration tanks of many full-scale biological nutrient removal facilities (total nitrogen losses of up to 30% were frequently occurring U.S.EPA (1987)). Since then researchers and engineers have attempted to elucidate the mechanics behind the aerobic denitrification phenomenon and the conditions required for its optimization. It is thought that aerobic denitrification may offer advantages and possible savings when compared to alternative traditional separate stage nitrification denitrification processes. The use of real time parameters such as ORP, pH, DO and airflow rate (oxygen demand) can provide immediate insight into a biological treatment process. This knowledge can be used to ensure optimum performance in terms of real time pollutant concentrations and hydraulic loads. This research aimed to elucidate some operational aspects of the aerobic denitrification phenomenon, to investigate opportunities for several types of real time control (ORP, pH, DO, and airflow), and to develop a process control system using the online parameters. An activated sludge process was established within two lab-scale sequencing batch reactors. The reactors were operated under a range of conditions using raw domestic wastewater as the feed. ORP, pH, DO, and airflow were measured online in real time while other biochemical parameters (such as the various forms of nitrogen) were measured periodically using HACH photometric procedures. Dissolved oxygen concentration was the operational variable (dissolved oxygen set points (DOSP) 4.0-0.5 mg/L), other parameters such as MLSS concentration and feed strength were maintained (where possible) at a consistent value (~3000 mg/L and ~600 mg/L COD respectively). The system was operated under both nitrification and aerobic denitrification conditions with the dissolved oxygen concentration determining the degree to which aerobic denitrification existed (~40% TN removal at DOSP 0.5 mg/L). The biochemical event of interest was the depletion of ammonia nitrogen. The key online profiles of interest were the ORP-time profile and the pH-time profile. The research sought to demonstrate the credibility of ORP and pH as real time control parameters for the depletion of ammonia nitrogen in the aerobic denitrification process. To achieve this a microprocessor-software based process control system was developed by using the relationship between online measurements and biochemical events. The results indicated the ORP-time profile does not provide any feature for the depletion of ammonia nitrogen when the dissolved oxygen is maintained at a fixed concentration. That is the previously identified "ammonia elbow" is probably the result of dissolved oxygen concentration breakthrough rather than nutrient depletion. The lack of an ammonia depletion elbow meant that ORP could not be used for process control within the aerobic denitrification process. The pH-time profile showed an "ammonia valley" feature at the point of ammonia depletion. This feature was consistently present in both the nitrification and aerobic denitrification processes. The research incorporated the feature into the process control system and successfully used it to control the length of the aerobic denitrification treatment sequence. With respect to elucidating some operational aspects of the aerobic denitrification phenomenon the main variable of interest was the dissolved oxygen concentration. The results indicated the aerobic denitrification process has an optimum dissolved oxygen concentration around but probably below 0.5 mg/L. The process probably does not have an optimum concentration but an optimum range. It is likely this range is influenced by variables such as the biomass concentration and the release of reducing power in terms of the ability to hydrolyze stored carbon polymers. A secondary objective of this research was to elucidate advantages of aerobic denitrification relative to alternative traditional separate stage nitrification denitrification processes. For example it has been proposed that aerobic denitrification may require smaller treatment reactors, require less air for nitrification, produce less sludge per unit of wastewater treated (relative to a traditional nitrification-denitrification process), and have less dependence on organic carbon for denitrification. The results suggested the low dissolved oxygen concentrations required for the aerobic denitrification process significantly inhibit the nitrification process. This causes a considerable extension in the required aeration times for the oxidation of ammonia nitrogen (~300% increase in aeration time relative to a traditional nitrification process). The longer aeration times suggest the process may not offer savings in terms of aeration requirements (aerobic denitrification required ~200% more air per unit of wastewater treated relative to a traditional nitrification process) or treatment tank sizes (relative to traditional separate stage processes). A reduction in the quantity of sludge produced (per unit of wastewater treated) of over 30% was demonstrated for the aerobic denitrification process. While aerobic nitrogen removal has been achieved under certain conditions autotrophically by other researchers this work found the process is probably undertaken predominantly by heterotrophic micro-organisms. The low dissolved oxygen concentrations required for the process also appear to favor heterotrophic denitrification using stored intracellular carbon (biosorption). This research demonstrated the aerobic denitrification process was able to remove nitrogen with less dependence on organic carbon (the organic carbon requirements for aerobic denitrification were not quantified but experimental data suggests a possible 40% saving) either by the use of a shortened nitrification-denitrification pathway and/or the ability to use stored carbon.

La present tesi es basa en l'estudi dels processos de bioremediació com a tecnologies de descontaminació d'aqüífers.
Concretament, es pretén estudiar la desnitrificació i la decloració reductiva com a tecnologies de bioremediació per eliminar, respectivament, els nitrats i els hidrocarburs alifàtics clorats (o CAHs, de chlorinated aliphatic hydrocarbons) de les aigües subterrànies contaminades. A més, es pretén aplicar tecnologies avançades que permetin millorar en el coneixement d'aquests processos.
L'aqüífer associat a la riera d'Argentona, situat a Argentona (Espanya), ha estat la zona d'estudi per tal d'investigar el procés de desnitrificació. En primer lloc, s'han dut a terme experiments en batch amb aigua subterrània i sòl subsuperficial del mencionat aqüífer. A partir d'aquests primers estudis, s'ha observat la baixa capacitat de l'aqüífer per eliminar els nitrats de manera natural, però alhora s'ha vist la viabilitat d'aplicar un procés de bioremediació com és l'addició de matèria orgànica. Paral·lelament, s'ha estudiat la influència de diferents factors com ara la presència d'oxigen i la tipologia de donador d'electrons sobre el procés de desnitrificació.
Posteriorment, s'ha desenvolupat un model matemàtic per descriure el consum d'oxigen, de nitrats i de matèria orgànica per part de la població microbiana facultativa i heterotròfica present en el material d'aqüífer. Alguns paràmetres del model han estat calibrats i s'ha estudiat la qualitat d'aquests paràmetres. El model desenvolupat constitueix una primera aproximació per tal d'obtenir un model de desnitrificació in situ.
Per tal d'avançar en l'estudi del procés de desnitrificació en condicions naturals, s'han realitzat experiments en dinàmic simulant el flux d'aigua subterrània a través de l'aqüífer. L'eficiència d'injectar matèria orgànica en aquestes condicions s'ha demostrat.
Paral·lelament, s'han estudiat els efectes hidrodinàmics de l'aplicació de la bioremediació i, els resultats han demostrat la importància de dissenyar acuradament les tecnologies de bioremediació a escala de camp. Per altra banda, s'ha descrit la desnitrificació en condicions dinàmiques integrant en un model matemàtic les reaccions bioquímiques i els processos de transport que tenen lloc a la columna experimental.
Finalment, s'han aplicat les noves tecnologies de biologia molecular per entendre els efectes de l'aplicació d'un procés de bioremediació a nivell microbià. Per una banda, l'aplicació de la tècnica de la reacció en cadena de la polimerasa a temps real (o real-time PCR, de real-time polymerase chain reaction) ha demostrat el creixement de la població microbiana i, concretament, de la població desnitrificant en el material d'aqüífer estimulat. Per altra banda, l'electroforesi en gel de gradient desnaturalitzant (o DGGE, de denaturing gradient gel electrophoresis) ha permès investigar els canvis en la població microbiana indígena del material d'aqüífer a causa de l'estimulació amb matèria orgànica.
Amb l'objectiu d'avançar en el coneixement dels processos de bioremediació en aigües subterrànies, s'ha estudiat també la decloració reductiva de CAHs. En aquest cas, s'han aplicat metodologies experimentals destinades a l'estudi de la posible aplicació d'una barrera reactiva permeable per eliminar una ploma que conté majoritàriament cis-1,2-dicloroetilè i clorur de vinil, i que flueix cap al riu Zenne, prop de la ciutat de Brussel·les (Bèlgica).
L'estudi ha inclòs experiments en batch per tal d'investigar el potencial degradatiu del material d'aqüífer i dels propis sediments del riu Zenne. Així mateix, també s'han dut a terme experiments en columna que simulaven el flux d'aigua subterrània a través dels sediments del riu o del material d'aqüífer. Els resultats han demostrat el gran potencial degradatiu dels sediments, que a la llarga es podrien potenciar com a biobarrera natural del sistema per tal de prevenir que les aigües contaminades arribin a l'aigua superficial del riu Zenne.
This thesis is based on the study of bioremediation processes as reliable technologies to remove contaminants from groundwater.
Specifically, it is aimed to study denitrification and reductive dechlorination as bioremediation technologies to remove nitrates and chlorinated aliphatic hydrocarbons (CAHs), respectively, from polluted groundwater. In addition, it is aimed to apply advanced technologies which allow improving on the knowledge of these processes.
The aquifer associated to the Stream Argentona, located in Argentona, Catalunya (Spain), was selected as study site to investigate the denitrification process. In the first part, microcosm experiments containing groundwater and subsoil from the aquifer were performed. From these first studies it was observed the low capacity of the aquifer to eliminate nitrates under natural conditions, but, at the same time, it was noted the feasibility of applying a bioremediation process such as the addition of organic matter. In addition, the influence of different factors such as the presence of oxygen and the type of electron donor on the denitrification process was studied.
Afterwards, a mathematical model was developed to explain the microbiological processes that occur when stimulating the aquifer material with an organic carbon source. The model could successfully explain the consumption of oxygen, nitrates and organic matter by the indigenous facultative heterotrophic microbial population from aquifer. Some parameters of the model were calibrated from experimental data and the quality of these parameters was investigated. The developed model constitutes a first approach in order to have reliable models for in situ denitrification.
In order to advance in the study of the denitrification process in natural conditions, dynamic experiments were carried out simulating the groundwater flow through the aquifer. The efficiency of injecting organic matter under these conditions was demonstrated. At the same time, hydrodynamic effects of the process were observed, indicating the importance to design properly bioremediation technologies before its application in field-scale. Furthermore, an integrated model coupling the biochemical reactions and the transport processes inside the column was developed and applied to describe denitrification under dynamic conditions.
Finally, molecular microbiological techniques were applied to investigate microbial changes due to the application of enhanced denitrification. On the one hand, real-time polymerase chain reaction (real-time PCR) assays revealed the growth of microbial population, specially of denitrifying bacteria in aquifer material stimulated with an organic carbon source. On the other hand, the denaturing gradient gel electrophoresis (DGGE) method allowed to investigate changes in the indigenous microbial community due to the amendment with organic matter.
In order to advance in the knowledge of bioremediation processes in groundwater, reductive dechlorination of CAHs in groundwater was studied. In this case, experiments at laboratory scale were applied, aimed to study the possible application of a permeable reactive barrier (PRB) to eliminate a CAH-contaminated plume, containing basically cis-1,2-dichloroethene and vinyl chloride, which flows to the River Zenne near Brussels, Belgium.
The study included batch experiments in order to investigate the degradation potential in aquifer and sediments of the River Zenne, as well as column experiments which simulated the groundwater flow through the sediments of the river or the aquifer material. The results demonstrated the high degradation potential of the sediments, which in the long term could be enhanced to act as a natural biobarrier of the system in order to prevent groundwater contaminants from arriving at the surface water of the River Zenne.

It is crucial to study the denitrification process driven by bacteria as it is one of the most important environmental processes for several reasons: i) it has an application in the removal of nitrogen (N) from high-N waste materials ii), it is one of the mechanisms to N-fertilizer¿s loss, iii) it contributes to the emissions of gasses with large global warming potential, and iv) it is the mechanism by which the global nitrogen cycle is balanced. Many models have been developed in the framework of continuous models to deal with the complexity of the denitrification process in order to become predictive models, but some of the assumptions contained in them are not realistic enough in those contexts, and also they have their own constraints and limitations. On the other hand, the researchers have paid more attention to the role of microbial activity with the advance of experimental techniques. Discrete models, such as individual-based models (IBMs), can be developed and applied to microbial systems due to the fact that they allow representation of some intracellular characteristics regarding the complexity of the micro-organisms, which constitutes a key advantage of this modelling approach in the study of the different biotechnological processes. The IBM is able to incorporate and accommodate the behaviour of denitrifying bacteria, and investigate their metabolism from different and attractive perspectives. A key factor in modelling the microbial activity is the methodology followed to represent metabolic pathways. A cellular metabolic model could be based on a non-equilibrium thermodynamic approach such as the Thermodynamic Electron Equivalents Model (TEEM), which is developed for biomass yield prediction using the associated standard Gibbs free energies and the bioenergetics growth efficiency between cell anabolism and catabolism. The main objective of this doctoral thesis is to develop an IBM to study denitrification processes driven by denitrifying bacteria, using TEEM to write microbial metabolic reactions (MMRs) which represent the metabolic pathways as the center of the individual sub-model. Two new computational models of the INDISIM family, INDISIM-Paracoccus and INDISIM-Denitrification have been designed, implemented on the NetLogo platform, parameterized and calibrated with experimental data to analyze the system dynamics in a bioreactor in batch and continuous culture with denitrifying bacteria growing in it. The bioreactor conditions can be aerobic and/or anaerobic, and the growing media is liquid medium with an electron donor, C-source, N-source, and oxygen and all N-oxides as electron acceptors. An open access and open source tool has been developed to write MMRs based on TEEM. It is called MbT-tool which stands for Metabolism-based on Thermodynamics. Using MbT-Tool three sets of MMRs have been written, which are the centre of the individual sub-model for INDISIM-Paracoccus and INDISIM-denitrification, representing reactions involved in: i) cellular maintenance, ii) individual mass synthesis, and iii) individual mass degradation to reduce cytotoxic products. The simulation results obtained with INDISIM-Paracoccus and INDISIM-Denitrification have been compared with experimental data published by Felgate et al. (2012) regarding the growth of Paracoccus denitrificans and Achromobacter xylosoxidans in a bioreactor. According to the statistical analysis of the simulations results, for both denitrifying bacteria tested, the IBMs developed show better adjustments in the assays with electron donor limited than in the assays with electron acceptor limited.
L’estudi del procés de desnitrificació és rellevant, ja que és un important procés mediambiental, a causa que: i) és un dels mecanismes que ocasiona una pèrdua dels fertilitzants de nitrogen (N), ii) és d’utilitat en l’eliminació de N en residus amb un alt contingut en N, iii) contribueix en les emissions de gasos d’alt potencial sobre l’escalfament global, i iv) és el mecanisme pel qual es tanca el cicle del N. S’han desenvolupat diversos models continus per tractar la complexitat del procés de desnitrificació en sistemes ambientals per tal de que puguin ser models amb capacitat predictiva, però alguns dels supòsits que es fan no són prou realistes i tenen les seves mancances i limitacions. D’altra banda, els investigadors estan posant més atenció en el rol que juga l’activitat microbiana, des de que en els darrers anys s’ha desenvolupat i avançat en tècniques experimentals de manera important. Models discrets, com els models basats en l’individu (IBMs), poden ser desenvolupats i utilitzats en sistemes microbians ja que permeten la representació d’algunes característiques intracel·lulars atenent a la complexitat dels microorganismes, cosa que resulta clau a l’hora d’abordar aquest nou enfoc per l’estudi de diversos processos biotecnològics. Els IBMs són capaços d’incorporar el comportament de les bactèries desnitrificants i d’investigar el seu metabolisme des de perspectives diferents. Un factor clau en la modelització de l’activitat microbiana és la metodologia seguida per a representar les rutes metabòliques. Un model de metabolisme cel·lular podria estar basat en l’enfoc de la termodinàmica de no-equilibri, com per exemple el denominat Model Termodinàmic d’Electrons Equivalents (TEEM). TEEM va ser desenvolupat per predir el rendiment de la biomassa utilitzant les energies lliures estàndards de Gibbs associades i l’eficiència bioenergètica de creixement entre els processos anabòlics i catabòlics de la cèl·lula. L’objectiu principal d’aquesta tesis doctoral és desenvolupar un IBM per l’estudi dels processos de desnitrificació duts a terme per bactèries desnitrificants, mitjançant l’ús del TEEM per descriure les reaccions metabòliques microbianes (MMRs) que representen les vies metabòliques i són el centre del sub-model individual. Dos nous models computacionals de la família d’INDISIM, l’INDISIM-Paracoccus i l’INDISIM-Denitrification han estat dissenyats, implementats en la plataforma de NetLogo, i parametritzats i calibrats amb dades experimentals per analitzar la dinàmica d’un sistema format per bactèries desnitrificants en un bioreactor en un cultiu tancat i/o continu, en condicions aeròbies i/o anaeròbies. El medi de cultiu és líquid i conté un donador d’electrons, oxigen i òxids de N com acceptors d’electrons, una font de carboni i una de N. S’ha creat una eina d’accés i codi obert per escriure les MMRs basades en el TEEM i és anomenada MbT-tool (Metabolisme basat en la Termodinàmica). Utilitzant MbT-tool es poden descriure tres grups de MMRs, que seran el centre del sub-model individual per l’INDISIM-Paracoccus i l’INDISIM-denitrification, i que són reaccions involucrades en: i) el manteniment cel·lular, ii) la síntesi individual de massa, i iii) la degradació individual de massa per reduir els productes citotòxics. Els resultats de simulació obtinguts amb INDISIM-Paracoccus i INDISIM-Denitrification han estat comparats amb les dades experimentals publicades per Felgate et al. (2012), sobre el creixement de Paracoccus denitrificans i Achromobacter xylosoxidans en un bioreactor. Segons l’anàlisi estadístic dels resultats, per les dues bactèries desnitrificants amb les quals s’ha testat, els IBMs desenvolupats mostren millors ajustos en els assajos amb donadors d’electrons limitants que en els assajos amb acceptors d’electrons limitants. El desenvolupament d’un IBM i la seva aplicació amb cert nivell de detall i complexitat intracel·lular constitueix una avantatge per la investigació de la desnitrificació bacterià.
Es relevante estudiar la desnitrificación ya que es un importante proceso medioambiental, debido a que: i) es uno de los mecanismos que explica la pérdida de fertilizantes de nitrógeno (N), ii) tiene aplicación en la remoción de N proveniente de residuos con alto contenido de N, iii) contribuye a las emisiones de gases que presentan gran potencial de calentamiento global, y iv) es el mecanismo por el cual se balancea el ciclo del N. Varios modelos han sido desarrollados usando el enfoque de la modelización continua para hacer frente a la complejidad del proceso de la desnitrificación, con la finalidad de obtener modelos predictivos, pero algunas de sus suposiciones no son suficientemente reales en este contexto, además estos modelos tienen sus propias restricciones y limitaciones. Por otro lado, los investigadores están prestando más atención al rol de la actividad microbiana, desde que en los últimos años se han desarrollado y avanzado las técnicas experimentales de manera importante. Modelos discretos, como los modelos-basados en el individuo (IBMs), pueden ser desarrollados y aplicados a sistemas microbianos ya que permiten representar algunas de las características intracelulares relacionadas con la complejidad de los microorganismos, lo cual constituye una ventaja clave de este enfoque de modelización en el estudio de diversos procesos biotecnológicos. El IBM es capaz de incorporar y adaptar el comportamiento de las bacterias desnitrificantes e investigar su metabolismo desde perspectivas distintas. Un factor clave para modelizar la actividad microbiana es la metodología utilizada para representar las rutas metabólicas. Un modelo metabólico celular puede estar basado en la termodinámica del no equilibrio como el Modelo Termodinámico de Electrones Equivalentes (TEEM), el cual está desarrollado para la predicción del rendimiento de la biomasa usando las energías estándar de Gibbs junto con la eficiencia bioenergética de crecimiento entre anabolismo y catabolismo celular. El objetivo principal de esta tesis doctoral es desarrollar un IBM para estudiar la desnitrificación bacteriana, usando el TEEM para escribir reacciones metabólicas microbianas (MMRs) las cuales representan a las rutas metabólicas y son el centro del sub-modelo individual. Dos nuevos modelos computacionales de la familia INDISIM, el INDISIM-Paracoccus y el INDISIM-Denitrification, han sido diseñados, implementados en la plataforma NetLogo, parametrizados y calibrados con datos experimentales para estudiar la dinámica del crecimiento de las bacterias desnitrificantes dentro de un bioreactor en cultivos cerrados y continuos, en condiciones aerobias o anaerobias. El medio de cultivo es líquido y contiene un donador de electrones, oxígeno y los óxidos de N como aceptores de electrones, una fuente de carbono y una fuente de N. Una herramienta de acceso libre y código abierto ha sido desarrollada para escribir las MMRs basadas en TEEM y es llamada MbT-Tool (Metabolismo basado en la Termodinámica). Utilizando MbT-Tool se pueden escribir tres grupos de MMRs que han sido el centro del sub-modelo individual para INDISIM-Paracoccus e INDISIM-Denitification, y que representan las reacciones involucradas en: i) el mantenimiento celular, ii) la síntesis de masa individual, y iii) la degradación de la masa individual para reducir productos citotóxicos. Los resultados de simulación obtenidos con INDISIM-Paracoccus e INDISIMDenitrification han sido comparados los datos experimentales publicados por Felgate et al. (2012) relacionados con el crecimiento de Paracoccus denitrificans y Achromobacter xylosoxidans dentro de un bioreactor. De acuerdo con el análisis estadístico de los resultados de simulación, los IBMs desarrollados muestran mejores ajustes para los experimentos con donador de electrones limitado que para los ensayos con aceptor de electrones limitado. El desarrollo y aplicación de IBMs con algunos detalles y complejidad intracelular, constituyen una ventaja clave en la investigación y comprensión de los diferentes pasos de la desnitrificación bacteriana.

In order to size the anoxic reactors in nutrient (N and P) removal activated sludge plants, it is essential to know the denitrification kinetics that are operative in such systems. To date, denitrification kinetics have been accurately defined only for systems that remove N alone; little research has been performed on denitrification in N and P removal plants.

This research is part of a project aimed at verifying the potential of a specifically assessed wooded riparian zone in removing excess of combined nitrogen from the Zero river flow for the reduction of nutrient input into Venice Lagoon. General objectives of this project were to increase knowledge on the processes which allow the riparian strips to act as a buffer and to identify the most appropriate management strategies in order to maximize the efficiency of these systems in supporting the microbial activities involved in the process. For this purpose, specific objectives were pursued to determine seasonal fluctuations of the microbial populations in the soil/water of the wooded riparian strip. The bacterial communities were determined by combined approaches involving cultivation, microscopic approaches and DNA bases techniques to characterize both culturable and total microbial community inside and outside the riparian strip. ARDRA and DGGE analyses of soil collected at different depths, showed a clear decrease of the microbial diversity in deeper horizons as compared to the medium depth and surface ones. A comparison between this soil and that collected from an undisturbed zone external to the riparian strip, indicated that this effect can be also observed in the external area, although higher microbial diversity was always present in the internal soil. DGGE cluster analysis and PCA of both genetic and chemical properties of water samples indicated that the bacterial populations present at the drainage ditches are rich in denitrifiers as a result of a mixing of bacterial communities carried by the Zero river flux and those already present in the soil of the riparian strip. Taken together, the overall results confirm what it was demonstrated by other chemical-physical analysis: the wooded riparian buffer zone assessed for water remediation (nitrogen removal from Zero river) is effectively working as a result of the special conditions there produced to support the work of specific microbial populations. The microbiological analysis here accomplished can also contribute to understand the bacterial population dynamic of an agricultural soil when transformed in a wooded strip and to provide key indications for the management of a phytoremediation site.
Questa ricerca fa parte di un più ampio progetto finalizzato a verificare l’attività di zone riparie atte a rimuovere l’eccesso di azoto combinato nel fiume Zero, con il fine ultimo di ridurre l’imput di nutrienti nella Laguna di Venezia. Obiettivo generale di questa ricerca è stato quello di aumentare le conoscenze relative ai processi che consentono alle zone riparie di agire come tamponi e identificare le strategie di gestione più appropriate per massimizzare l’efficienza di questi sistemi nel supportare le attività microbiche coinvolte. A questo scopo, sono stati perseguiti obiettivi specifici per determinare le fluttuazioni stagionali delle popolazioni microbiche nei suoli/acque della fascia tampone. Le comunità microbiche sono state determinate tramite un approccio combinato che ha previsto la coltivazione, tecniche microscopiche e tecniche molecolari al fine di caratterizzare sia la comunità microbica coltivabile sia quella totale, all’interno e all’esterno della fascia tampone. Le analisi ARDRA e DGGE di suoli raccolti a diverse profondità, mostrano una chiara diminuzione della diversità microbica negli orizzonti più profondi rispetto agli strati intermedi e superficiali. Il confronto tra suoli raccolti nella fascia tampone e suoli raccolti in una zona indisturbata esterna, indicano che questo effetto può essere osservato anche all’esterno sebbene una maggiore diversità microbica sia sempre rilevabile all’interno. Indagine DGGE e elaborazioni statistiche con PCA, sia delle proprietà genetiche che di quelle chimiche dei campioni d’acqua, hanno indicato che le popolazioni microbiche presenti nelle scoline sono ricche di denitrificanti e sono il frutto del rimescolamento delle comunità microbiche del fiume Zero con quelle già presenti nei suoli della fascia tampone. Nel complesso, questi risultati confermano quanto dimostrato da altre analisi fisico-chimiche: la fascia tampone messa a punto per il biorimedio delle acque (rimozione dell’azoto dal fiume Zero), sta effettivamente funzionando come risultato delle speciali condizioni che favoriscono specifiche popolazioni microbiche. Le analisi microbiologiche qui riportate possono inoltre contribuire alla comprensione delle dinamiche di popolazioni in suoli agricoli convertiti in fasce tampone e fornire indicazioni chiave per la gestione di siti di fitorimedio.

The research in this thesis was conducted at the Hampton Road Sanitation District's biological nutrient removal pilot, located at the Chesapeake-Elizabeth WWTP in Virginia Beach, VA. The pilot is operated in an A/B process with a high-rate, carbon-diverting A-stage, followed by a biological nitrogen removal B-stage containing four intermittently aerated CSTRs, followed by an anammox polishing MBBR. The goal of this research was to successfully combine short-cut nitrogen removal with sidestream enhanced biological nutrient removal (EBPR) in the most efficient way possible, specifically aiming to decrease cost and energy requirements, divert the most amount of carbon possible before B-stage, and to achieve low effluent nitrogen and phosphorus concentrations. A RAS fermenter (SBPR) and an A-stage WAS fermenter that feeds VFA into the SBPR (the supernatant of the fermenter is called fermentate) were implemented in order to enhance biological phosphorus removal. About 8 months after the RAS and WAS fermenter implementation, there was a 28 day consecutive period of low B-stage effluent OP <1 mg/L, with an average of 0.5 ± 0.1 mg/L OP. Following this low effluent OP period, bio-P became more unstable and there was high nitrite accumulation in the B-stage effluent for 106 days with concentrations ranging from 1.1-5.9 mg/L NO2. The nitrite accumulation was not due to NOB out-selection, confirmed by AOB and NOB maximum activity tests. It was determined that the nitrite accumulation was due to partial denitrification of nitrate to nitrite by bacteria using internally stored carbon, because profiles and activity tests showed anoxic nitrite accumulation at the end of the aerobic process. Post-anoxic denitrification using internally stored carbon compounds has been observed in other EBPR systems (Vocks, Adam, Lesjean, Gnirss, and Kraume, 2005). Fermentate addition was then halted, and nitrite accumulation and bio-P activity ceased all together, linking the fermentate addition to both bio-P activity and nitrite accumulation. Fermentate was then controlled to dose at 60% of the sCOD/OP (fermentate sCOD g/day / total OP- fermentate + influent - g/day) of the first low effluent OP period. During this fermentate dosing period where the average sCOD/OP was 15.6 ± 3.0 g/g, no nitrite accumulation was observed, but another consecutive low effluent OP period was observed with an average of 0.6 ± 0.2 mg/L OP. Linear correlation analysis shows that the highest r2 values relating the low effluent OP periods and the COD loads to the SBPR for both periods were between VFA g/day vs OP effluent mg/L, at r2=0.18 for the first low effluent OP period and r2=0.65 for the second. There were also high tCOD r2 values for the second low effluent OP period showing that COD hydrolysis in the SBPR could have impacted bio-P activity. However, the VFA r2 value was higher than any tCOD r2 value, concluding that the fermentate dosing mainly worked to enhance biological phosphorus removal by increasing the VFA load in g VFA as acetate/day. Since no nitrite was observed in a period with a lower VFA/OP dose, then the probable VFA load needed to provide enough internal storage to produce nitrite accumulation by partial denitrification is between 5-9 (g VFA as acetate/ g total OP). If sidestream EBPR systems could be studied further to promote nitrite accumulation and bio-P activity to produce low effluent OP, then short-cut nitrogen removal and EBPR could be successfully combined in an efficient way.
Master of Science
It is important to reduce nitrogen and phosphorus concentrations in wastewater treatment effluent in order to both protect the environment from eutrophication and to meet the increasingly stringent nutrient effluent discharge limits imposed by the EPA. Conventional biological nitrogen removal is achieved through nitrification and denitrification converting ammonia to nitrogen gas, where nitrogen gas is volatile and leaves the system naturally. Phosphorus removal can be achieved through either chemical addition or through biological phosphorus removal, where phosphorus is taken up in cells and removed from the system by the subsequent solids wasting of these cells. The combination of biological nitrogen and phosphorus removal can be improved to increase energy efficiency, reduce costs including aeration and chemical addition costs, increase system capacity and reduce tank sizes, and reduce biomass production, all while achieving low effluent N and P concentrations. Short-cut nitrogen removal can increase the efficiency of biological nitrogen removal. Deammonification, the combination of partial nitritation and anammox, has the potential to reduce wastewater treatment plant (WWTP) aeration costs by 63%, carbon requirements by 100%, and biomass production by 80% (Nifong, Nelson, Johnson, and B. Bott, 2013). Deammonification is the combination of partial nitritation and anammox. Anaerobic ammonia oxidation (anammox) is a useful class of bacteria that converts ammonia and nitrite straight to nitrogen gas in anaerobic conditions, which is a more direct pathway than the conventional nitrification-denitrification pathway. Anammox requires a nitrite supply, which can supplied by partial nitratation of ammonia to nitrite, performed by ammonia oxidizing bacteria (AOB) aerobically in the deammonification process. In order for partial nitratation to work, there needs to be nitrite oxidizing bacteria (NOB) out-selection so that the nitrite produced by AOB does not get oxidized to nitrate. Enhanced biological phosphorus removal (EBPR) is accomplished by the taking up and storing of orthophosphate (OP) by phosphorus accumulating organisms (PAOs). These organisms require an anaerobic carbon-storage phase followed by an aerobic growth phase where the internally stored carbon is used for growth. During the cell growth phase of PAOs in aerobic conditions, PAOs are able to take up more OP than they previously released in anaerobic conditions, creating a net OP removal from the system. There has been recent success in recycle activated sludge (McIlroy et al.) fermentation to enhance biological phosphorus removal, which works to promote hydrolysis, fermentation, and EBPR enhancement (Houweling, Dold, and Barnard, 2010). A portion of the RAS is introduced to an anaerobic zone before returning to the main process, allowing for extra VFA production and adsorption by PAOs. RAS fermentation solves the issue of carbon needed for EBPR in VFA/carbon limited systems without having to add too much additional carbon, creating a carbon efficient EBPR system. The research outlined in this study was done at the Hampton Road Sanitation District's (HRSD) pilot plant located within HRSD's Chesapeake-Elizabeth WWTP in Virginia Beach VA. The pilot is run in an A/B process that works in two separate steps: the A-stage is the first step that works to remove carbon by oxidation, and by adsorption so it can potentially be diverted, and the B-stage is the second step where biological nitrogen removal (BNR) is done. The BNR phase consists of an anaerobic selector followed by four completely stirred tank reactors (CSTRs) that are intermittently aerated to provide aerobic and anoxic phases. The pilot also has an anammox polishing step following B-stage. The nitrogen removal goal for this research was short-cut nitrogen removal via deammonification, by producing partial nitritation in B-stage and polishing with anammox. A B-stage RAS fermenter, along with an A-stage waste activated sludge (WAS) fermenter that feeds VFA into the RAS fermenter, was implemented to the existing pilot to enhance biological phosphorus removal. The overall goal of this study was to successfully combine short-cut nitrogen removal with sidestream EBPR to achieve low effluent N and P concentrations in the most energy and carbon efficient way possible. EBPR was achieved about eight months after the implementation of the RAS and WAS fermenter to the pilot. A period of B-stage effluent OP that was consistently below 1 mg/L OP was observed right before an unexpected period of high nitrite in the B-stage effluent. The high effluent nitrite lasted for 106 days and ranged from 1.1-5.9 mg/L of effluent nitrite during this time. The nitrite accumulation was unexpected because weekly maximum activity tests for AOB and NOB showed that NOB out-selection was not occurring. The first phase of this research investigates the cause of the nitrite accumulation. Based on profiles taken in the reactors in the aerobic and anoxic phases, and based on denitrification activity tests, it was determined that the nitrite accumulation was due to partial denitrification of nitrate to nitrite. Because this partial denitrification was happening in the reactor anoxic times where external should have been used up, it was determined that the source of the partial denitrification was from a bacteria using internally stored carbon during anoxic periods as the electron supply for partial denitrification. Research has showed that EBPR systems promote bacteria that are capable of storing carbon internally and keeping that carbon stored through an aerobic phase and then using that stored carbon for denitrification following an aerobic phase (Vocks et al., 2005), like observed in this research. The second phase of this research sought to link the nitrite accumulation and bio-P activity to the VFA added to the RAS fermenter. The VFA addition was decreased in phases, and with that a decrease in nitrite in the effluent was observed. The bio-P activity became more unstable after the nitrite accumulation occurred, but all bio-P activity ceased after VFA addition to the RAS fermenter ceased. It was concluded, unsurprisingly, that the VFA added to the RAS fermenter was the source of the internally stored carbon that caused the nitrite accumulation, and necessary for bio-P enhancement. The third phase of this research sought to recreate the low effluent OP period and the nitrite accumulation by controlling the VFA dose to the RAS fermenter. The average soluble chemical oxygen demand (sCOD) per OP (fermenter sCOD g/day / total OP-fermenter + influent- g/day) of the period of low effluent OP was calculated, and the dose from the WAS fermenter was controlled to meet 60% of the calculated value. The calculated dose was 13.6 gC/gP, but the actual average dose from controlling the load during this period was 15.6 ± 3.0 gC/gP. The average VFA/OP (g VFA as acetate/ g total OP) dose for the first low effluent OP period was 9.4 ± 3.6 g/g, and the average dose for the third phase of research was 5.5 ± 1.3 g/g. No nitrite accumulation occurred in this phase, but another consistent low effluent OP period did occur. From linear correlation analysis, the highest r2 values relating the low effluent OP periods and the COD loads to the RAS fermenter for both periods were between VFA g/day vs OP mg/L, at r2=0.18 for the first period and r2=0.65 for the second. This shows that effluent OP < 1 mg/L can be achieve at 5.5 or 9.4 (g VFA as acetate/ g total OP). Since no nitrite was observed in phase 3, than the probable VFA load needed to provide enough internal storage to produce nitrite accumulation by partial denitrification is probably between 5.5-9.4 (g VFA as acetate/ g total OP). This research was significant because the link between nitrite accumulation and bio-P enhancement with sidestream RAS and WAS fermentation was confirmed. Partial denitrification of nitrate to nitrite could be used as an alternative source of nitrite for anammox, instead of NOB out-selection and partial nitritation of ammonia to nitrite by AOB, in combined EBPR and short-cut nitrogen removal systems. If sidestream EBPR systems could be used to promote nitrite accumulation and bio-P activity to produce low effluent OP and nitrogen removal efficiently than short-cut nitrogen removal and EBPR could be successfully combined in an efficient way. Future work needs to be done on the organism that is capable of nitrite accumulation and if that organism can be enhanced in conjunction with EBPR organisms to promote both nitrite accumulation and low effluent OP simultaneously.

It has been illegal to deposit household waste in Swedish landfills since 2005. The large amount of waste deposited prior to this does however continue to pose an environmental concern, mainly in the form of leachate water. This study focused on enhancing the denitrification process in a leachate water treatment plant through bioaugmentation. The two strains Brachymonas denitrificans and Comamonas denitrificans as well a commercial seed mix from ClearBlu Environmental® (CBE-mix) containing amongst others, Pseudomonas putida AD 21 and Pseudomonas fluorescens, were investigated as candidates. Nitrite, nitrate, and ammonium concentrations were measured in laboratory-, and pilot-scale studies to follow the processes of nitrification and denitrification. The pilot study was conducted for 10 days in the middle of May 2020 with leachate from the treatment plant in an aerated and nonaerated setup in open field conditions. C. denitrificans and B. denitrificans were both shown to be able to adapt to growth in landfill leachate. The addition of these strains led to a higher rate of nitrate reduction compared to the control during the first days of the pilot experiment but showed no difference in the total amount of nitrate reduced. The combined nitrogen concentration of ammonium, nitrate, and nitrite was 6.7% lower than the control when using a culture augmented with the CBE-mix in the aerated setup. This could indicate aerated denitrification. The amount of nitrate reduced during the pilot experiment was increased with 32% when augmenting the community with the CBE-mix in a nonaerated setup. An explanation could be that certain strains in the mix were able to utilize hard to degrade organic carbon present in the leachate or that the mix had a higher ratio of reduced nitrate to consumed organic carbon than the indigenous community.
Det har varit olagligt att deponera hushållsavfall i Sverige sedan 2005, den stora mängd avfall som deponerats innan dess fortsätter dock att utgöra ett miljöproblem, främst genom genereringen av lakvatten. Den här studien fokuserade på möjligheten att förbättra denitrifikationen i ett reningsverk för lakvatten genom bioaugmentation. Två stammar tillhörande Brachymonas denitrificans, och Comamonas denitrificans, samt en kommersiell bakterieblandning från ClearBlu Environmental® innehållande bland andra Pseudomonas putida AD 21 och Psedomonas flourescens, undersöktes som möjliga kandidater. Ammonium-, nitrat- och nitritkoncentrationer mättes i odlingsstudier i labbskala och i en pilotstudie för att undersöka nitrifikation och denitrification. Pilotstudien utfördes i en luftad och en o luftad konfiguration utomhus i mitten av maj 2020, med lakvatten från reningsverket under en 10 dagars period. C. denitrificans och B. denitrificans klarade båda av att anpassa sig till tillväxt i lakvatten. Tillsats av dessa arter ledde till en ökning i nitratreduktionshastighet i början av pilotexperimentet men gav ingen total minskning av nitratmängden. Den sammanlagda slutkoncentrationen av ammonium-, nitrat- och nitritkväve var 6,7% lägre än i kontrollen när en kultur argumenterad med den kommersiella bakteriemixen användes i den luftade konfigurationen. Mängden reducerat nitrat ökade med 32% när en kultur augmenterad med den kommersiella mixen användes i den oluftade konfigurationen. En möjlig förklaring är att vissa stammar i mixen klarade av att tillgodogöra sig svårnedbrytbara kolföreningar i lakvattnet eller att ration mellan reducerat nitrat mot konsumerat organiskt kol var högre än i det ursprungliga microbsamhället.

The effect of naturally produced volatile fatty acids (VFAs) on the removal of 2, 4-D from a wastewater during the denitrification process was studied in this thesis. The VFAs were generated from an anaerobic digester using soya flour solution as a synthetic feed. The digester was operated at an SRT and HRT of 10 days. The pH (4.8 ± 0.2) and temperature (32 ± 3 ℃) of the digester were not controlled. A mean VFA concentration of 3153 ± 801 mg/L was achieved with acid speciation results of acetic (51.4 %), propionic (27.5 %), n-butyric (19.6 %) and iso-valeric (1.4 %). The specific VFA production rate was 0.014 mg VFA/mg VSS/day. The extent of the digestion process converting the substrate from a particulate to soluble form was evaluated as the specific TOC solubilization rate (0.007 mg TOC/mg VSS/day), soluble COD production rate (0.022 mg SCOD/mg VSS/day) and percent VSS reduction (14 %). The low solubilization rate is possibly due to high feed solids (3.4%) which led to a heavily overloaded bioreactor. It also suggests that the particulate substrate was not entirely amenable to solubilization. The acclimation of 2, 4-D degrading bacteria was developed successfully in an SBR fed with sewage and 2, 4-D (30-100 mg/L) as carbon and energy sources. A mean MLSS of 3653 ± 547 mg/L and an SRT of 20 ± 9 days were observed during the research period. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) of 101 ± 50 mL/g and less than 5 mg/L of effluent suspended solids. The specific 2, 4-D degradation rate was 0.046 ± 0.018 mg/mg MLSS/day. However, the removal of 2, 4-D during 60 minutes of non-aerated phase was negligible while more than 90 % of the 2, 4-D was removed within 240 minutes of the aerated phase. The successful degradation of 2, 4-D is related to the length of the acclimation period, as the acclimation period increased, the specific biodegradation rate increased. A biosorption study using ultrasound pre-treatment of the SBR acclimated biomass suggested that less than 10 % of the removal of 2, 4-D was due to biosorption, while more than 90 % removal of the 2, 4-D was likely due to biodegradation. Denitrification batch tests (using SBR-acclimated biomass) demonstrated that the addition of a digester effluent rich in naturally-produced VFAs increased both the 2 specific denitrification rate and the 2, 4-D degradation efficiency, as compared to that using 2, 4-D as a sole carbon source. In particular, the specific denitrification rates increased from 0.0119 ± 0.0039 to 0.0192 ± 0.0079 to 0.024 ± 0.003 g NO₃-N/g VSS per day, when using 2, 4-D alone, 2, 4-D plus natural VFAs and natural VFAs alone as carbon sources. The percent 2, 4-D removal increased from 28.33 ± 11.88 using 2, 4-D alone as a carbon source to 54.17 ± 21.89 using 2, 4-D plus natural VFAs as carbon sources. The specific 2, 4-D degradation rate and 2, 4-D removal efficiency of unacclimated biomass were 2.0 to 2.5 times less than those of the acclimated biomass. Natural VFAs and synthetic VFAs were found to be identical in denitrification batch tests in terms of their use as a carbon source. The mean specific denitrification and VFA-C consumption rates as well as the mean specific 2, 4-D degradation rate derived from experiments using natural VFAs and 2, 4-D as carbon sources were close to the valuess from experiments using synthetic VFAs and 2, 4-D as carbon sources. Further exploration of 2, 4-D degradation behaviour with pulsed additions of NO₃-N did not find further significant 2, 4-D removal, although almost all of NO₃-N was used by the end of the experimental run due to endogenous carbon sources used for cell maintenance and growth. However, the higher the concentration of biomass used in the denitrification batch system, the larger the amount of 2, 4-D degraded and the faster the VFA-C and NO₃-N were consumed. Further research with respect to optimisation of the acid-phase anaerobic digestion process (e.g. to adjust SRT and HRT or to lower the solid content of synthetic feed) would improve the specific VFA production rate and the solubilization rate. More research on the SBR could be carried out to investigate its maximum 2, 4-D removal capability as well as the removal of other structurally related herbicides. Attempts could be made to stimulate the growth of denitrifiers in the SBR (e.g. to add certain amounts of NO₃-N according to proper C: N ratios or to increase the length of non-aerated time). More microbiological studies of 2, 4-D degrading bacteria may also be helpful to understand the combined SBR/denitrification and 2, 4-D degradation process. More theoretical aspects of modelling kinetics could be developed to apply the combined process in-situ at 2, 4-D contaminated sites.

Este trabalho teve como objetivo geral a caracterização de um sistema de tratamento biológico de remoção de fenol em reator anaeróbio de leito fluidificado utilizando o nitrato como aceptor final de elétrons. O reator foi construído em acrílico transparente, com dimensões equivalentes a 190 cm de altura e 5,3 cm de diâmetro interno, totalizando um volume de 4192 cm³, dos quais cerca de 44% (1831 cm³) foram ocupados pelo meio suporte, na situação de leito fixo. Para imobilização da biomassa foram utilizadas partículas de poliestireno, que foram previamente ativadas através de ataque ácido, com o intuito de aumentar a rugosidade e a porosidade da superfície do material, facilitando a aderência da biomassa ao meio suporte. O reator foi inoculado com lodo proveniente de reator UASB, responsável pelo tratamento de despejos de suinocultura. A realização do experimento foi dividida em cinco fases, que foram alteradas de acordo com o desempenho e a estabilidade do sistema diante do aumento das concentrações de fenol e nitrato. As concentrações médias de fenol afluente estudadas foram de 52, 107, 201, 335 e 518 mg/L, de maneira que não foi detectada presença de fenol no efluente para concentrações de até 335 mg/L. A eficiência de remoção reduziu-se para aproximadamente 70%, quando foi operado com concentrações de fenol afluente superiores a 500 mg/L. A relação entre carbono (proveniente exclusivamente do fenol) e N - \'NO IND. 3\' foi aproximadamente 1, portanto, as concentrações médias afluentes de N - \'NO IND. 3\' testadas foram equivalentes a 45, 79, 157, 260 e 362 mg/L, cujas eficiências de remoção de nitrogênio foram de 94%, 89%, 86%, 79% e 51%, respectivamente. O pH efluente variou entre 7,64 e 8,35, estando de acordo com sistemas que realizam o processo de desnitrificação. Em geral, cerca de 3,8 g DQO foi consumido por grama de N - \'NO IND. 3\' removido. Não foi observado acúmulo de nitrito no sistema, considerando que o valor médio da concentração efluente foi de 1,5 mg/L de N - \'NO IND. 2\' para todo período de operação. O experimento teve duração de 162 dias, nos quais o sistema mostrou resultados satisfatórios para redução de carbono e nitrogênio, mesmo quando operado com elevadas concentrações de fenol e nitrato.
This work aimed the general characterization of a phenol removal biological treatment system in an anaerobic fluidized bed reactor using nitrate as the final electron acceptor. The reactor was built in transparent acrylic, with equivalent dimensions of 190 cm height and 5.3 cm intern diameter, resulting in 4,192 cm³ volume, which 44% were occupied by the support medium in a fix bed situation. Polystyrene particles were used to immobilize biomass, these particles were previously activated through acid attack, in order to increase materials roughness and superficial porosity, facilitating biomass adherence to the support medium. The reactor was inoculated with sludge from UASB reactor, responsible for swine culture effluent treatment. The experiment was divided in five phases, which were modified according to system performance and stability under the increase of phenol and nitrate concentrations. The mean phenol affluent concentrations studied were: 52, 107, 201, 335 and 518 mg/L, so that no phenol was detected in effluent in concentrations bellow 335 mg/L. The removal efficiency decreased to about 70% for affluent phenol concentrations over 500 mg/L. Carbon (exclusively from phenol) and N -\'NO IND. 3\' ratio was nearly 1, therefore the N \'NO IND. 3\' mean affluent concentrations tested were equivalent to 45, 79, 157, 260 e 362 mg/L, whose nitrogen removal efficiency were 94%, 89%, 86%, 79% e 51%, respectively. Effluent pH varied between 7.64 and 8.35, in agreement with denitrification process systems. In general, around 3.8 g DQO were consumed per gram of removed N \'NO IND. 3\'. No nitrite accumulation was observed in the system, considering that the mean effluent concentration was 1.5 mg/L de N - \'NO IND. 2\' to all operation period. Experiment lasted 162 days, during this time the system showed satisfactory results for carbon and nitrogen reduction, even when operated with high phenol and nitrate concentrations.

The purpose of this study was to investigate the effects of copper on the treatment of an abandoned landfill leachate by a Modified Ludzack Ettinger (MLE) single-sludge, activated sludge treatment system. MLE systems are designed to accomplish nitrification and denitrification, and at least two systems were used: one to which copper was added, and one maintained as a control. The system that did not receive copper additions gave an indication of the treatability of the leachate by an MLE system. Copper was added at concentrations of 1.0, 2.0, 2.5, and 5.0 mgCu/L in the influent and the sludge age was varied from 8 to 30 day. It was determined that copper did inhibit nitrification and denitrification. A strong linear relationship was shown to exist between the specific copper loading on the system, that is the total copper entering the system within a day divided by the total biomass within the system, and the soluble copper concentration within the system. The adsorption of copper by the activated sludge, and the resulting soluble copper concentration in the mixed liquor, could be generally described by the Freundlich Isotherm. Intermittent inhibition of nitrification unrelated to copper addition also occurred during treatment of the landfill leachate which was obtained from the abandoned Dixie Caverns Landfill near Roanoke, Virginia. The inhibiting substance was not identified during this study. It did not significantly inhibit denitrification, but did cause elevated effluent suspended solids concentrations. An additional treatment step would be needed for reliable treatment of the leachate. Copper additions caused inhibition of both nitrification and denitrification. The degree of nitrification and denitrification inhibition was a strong function of the soluble copper to ML VSS ratio in the reactors, i.e., the toxin -to -microorganism (TIM) ratio. Nitrification and denitrification appeared to be equally sensitive to copper. Both were severely inhibited at a soluble copper to ML VSS ratio of 0.001 in aerobic and anoxic reactors, respectively. Nitrosomonas species were more strongly inhibited by copper concentrations than were the Nitrobacter species. The denitrifiers appeared to be as sensitive to copper as the Nitrosomonas species.
Master of Science

The hybrid activated sludge-biofilm system called Integrated Fixed Film Activated Sludge (IFAS) has recently become popular for enhanced nitrification and denitrification in aerobic zones because it is an alternative to increasing the volume of treatment plant units to accomplish year round nitrification and nitrogen removal. Biomass is retained on the fixed-film media and remains in the aerobic reactor, thus increasing the effective mean cell resident time (MCRT) of the biomass and providing the temperature sensitive, slow growing nitrifiers a means of staying in the system when they otherwise would washout. While the utilization of media in aerobic zones to enhance nitrification and denitrification has been the subject of several studies and full-scale experiments, the effects and performances of fixed film media integrated into the anoxic zones of biological nutrient removal (BNR) systems have not adequately been evaluated as well as the impacts of integrated media upon enhanced biological phosphorus removal (EBPR). Also, user-friendly software designed specifically to simulate the complex mixture of biological processes that occur in IFAS systems are not available. The purpose of this research was to more fully investigate the effects of integrated fixed film media on EBPR, to evaluate the impacts of media integrated into the anoxic zone on system performance, and to develop a software program that could be used to simulate the effects of integrating the various types of media into suspended growth biological nutrient removal (BNR) systems. The UCT type configuration was chosen for the BNR system, and Accuweb rope-like media was selected for integration into the anoxic zones of two IFAS systems. The media also was integrated into the aerobic reactors of one of the systems for comparison and for further investigation of the performance of the Accuweb media on enhanced nitrification and denitrification in the aerobic zones. The experiments were conducted at 10 day total MCRT during the initial phase, and then at 6 days MCRT for the experimental temperature of 10 oC. A13 hour hydraulic retention time (HRT) was used throughout the study. A high and a low COD/TP ratio were used during the investigation to further study the effects of integrated media on EBPR. The PC Windows based IFAS program began with the concepts of IAWQ model No. 2 and a zero-dimensional biofilm model was developed and added to predict the IFAS processes. Experimental data from the initial study and existing data from similar studies performed at high temperatures (>10oC) indicated that there were no significant differences in BNR performances between IFAS systems with media integrated into the anoxic and aerobic or only aerobic zones and a suspended growth control system maintained at the same relative high MCRT and temperature values. Even though greater biological nitrogen removal could not be achieved for the experimental conditions used, the experimental results indicated that the IFAS systems with fixed film media installed in the anoxic zone have a greater potential for denitrification than conventional BNR systems. As much as 30 percent of the total denitrification was observed to occur in the aerobic zones of the system installed the media only anoxic zones and 37% in the system with integrated media in both anoxic and aerobic zones where as no denitrification was observed in the aerobic zones of the control system when the systems were operated at 6 days MCRT and COD/TP of 52. It is statistically confirmed EBPR can be maintained in IFAS systems as well as Control systems, but the IFAS processes tend to have more phosphorus release in the anoxic zones with integrated fixed film installed. Further, the combination of split flow to the anoxic zone and fixed film media in the anoxic zone resulted in the decreased EBPR performances in the IFAS system relative to the control system.
Ph. D.

The objective of this dissertation was to provide a controlled comparison of identical continuous flow BNR processes both with and without prefermentation in order to provide a stronger, more quantitative, technical basis for design engineers to evaluate the potential benefits of prefermentation to EBPR in treating domestic wastewater. In addition, the even less understood effect of prefermentation on denitrification kinetics and anoxic phosphorus (P) uptake was studied and quantified. Other aspects of BNR performance, which might change due to use of prefermentation, will also be addressed, including anaerobic stabilization. Potential benefits to BNR processes derived from prefermentation are compared and contrasted with the more well-known benefits of primary clarification. Finally, some biokinetic parameters necessary to successfully model both the activated sludge systems and the prefermenter were determined and compared for the prefermented versus the non-prefermented system. Important findings developed during the course of this dissertation regarding the impact of prefermentation upon the performance of activated sludge treatment systems are summarized below: • For a septic COD-limited (TCOD:TP < 40:1) wastewater, prefermentation was found to enhance EPBR by 27.7% at a statistical significance level of alpha=0.05 (95% confidence level). • For septic P-limited (TCOD:TP > 40:1) wastewaters, prefermentation was not found to improve EBPR at a statistical significance level of alpha=0.05 (95% confidence level). • The increased anaerobic P release and aerobic P uptakes due to prefermentation correlated with greater PHA formation and glycogen consumption during anaerobiosis of prefermented influent. • Improvements in biological P removal of septic, non-P limited wastewater occurred even when all additional VFA production exceeded VFA requirements using typical design criteria (e.g. 6 g VFA per 1 g P removal). • Prefermentation increased RBCOD content by an average of 28.8% and VFA content by an average of 18.8%, even for a septic domestic wastewater. • Prefermentation increased specific anoxic denitrification rates for both COD-limited (14.6%) and P-limited (5.4%) influent wastewaters. This increase was statistically significant at alpha=0.05 for COD-limited wastewater, but not for P-limited wastewater.
Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering

The gap between resource demand for the industrialized world and non-renewable feedstock like fossil fuels, essential agricultural fertilizer is getting increasingly severe, which has resulted in alarming-increasingly impacts on worldwide environmental problems. Meanwhile, wastewater treatment plants (WWTPs), as an essential facility for urbanization, is also confronting new rising challenges such as energy consumption and operation costs rather than only improving effluent wastewater quality. It is thereby important to develop new approaches for next-generation WWTPs with less energy consumption and costs in a sustainable way. The objective was to study the application of volatile fatty acids (VFAs) from waste as an external carbon source on denitrification by manometric tracking method in the lab-scale. Food waste and primary sludge were used for anaerobic fermentation to produce VFAs, which was then used as a sole external carbon source with various C/N ratio in denitrification batch test. The results were compared with traditional external carbon sources, acetate and methanol. It was found that the maximum denitrification rate with VFAs as an external carbon source was 15.73 ± 0.95 mg NOx-N/g VSS h, faster than those with acetate and methanol as external carbon sources. When C/N ratio ≥ 4.5 nitrate removal efficiency and the highest maximum denitrification rate were reached, the optimum C/N ratio for dosing VFAs as an external carbon source was thus determined as 4.5. In addition, denitrification capacity experiments with addition of VFAs produced from three different pH-controlled digestion reactors as an external carbon source were then conducted under an optimum C/N ratio of 4.5. As a result of the composition difference between VFAs produced from different pH environment, it was observed that, with VFAs from pH-10 digestion reactor denitrification rate was slightly higher than those with VFAs from pH-5 and none-pH-controlled digestion reactors. Furthermore, denitrification batch test using chemical tracking method was conducted to compare with manometric tracking method, and it was proven that the results obtained from manometric denitrification tests were reliable and valid. The overall results show that VFAs produced from anaerobic fermentation are an excellent external carbon source for denitrification, and it realizes the utilization of carbon resource recovery from WWTPs, which is crucial for next-generation wastewater treatment.
Klyftan mellan resursefterfrågan i den industrialiserade världen och icke-förnybar råvara som fossila bränslen, essentiell jordbruksgödsel, blir allt svårare, vilket har resulterat i oroväckande effekter på globala miljöproblem. Samtidigt står avloppsreningsverk (ARV), som är en viktig anläggning för urbanisering, inför nya ökande utmaningar som energiförbrukning och driftkostnader snarare än att förbättra kvaliteten på renat avloppsvatten. Det är därmed viktigt att utveckla nya strategier för nästa generations ARV med mindre energiförbrukning och kostnader på ett hållbart sätt. Målet var att studera tillämpningen av flyktiga fettsyror (VFA) från avfall som en extern kolkälla i denitrifikation med manometrisk metod i laboratorieskala. Matavfall och primärslam användes för anaerob rötning för att producera VFA, som sedan användes som en extern kolkälla med olika C/N-förhållanden i denitrifikationstest. Resultaten jämfördes med traditionella externa kolkällor, acetat och metanol. Det visade sig att maximal denitrifikationskapacitet med VFA som extern kolkälla var 15,73 ± 0,95 mg NOx-N/g VSS h, snabbare än de med acetat och metanol som extern kolkälla. När C/N-förhållandet ≥4,5 uppnåddes högsta nitratborttagningseffektivitet och maximala denitrifikationskapacitet, varför det optimala C/N-förhållandet för dosering av VFA som extern kolkälla bestäms som 4,5. Dessutom genomfördes experiment med denitrifikationskapacitets med tillsats av VFA producerat från tre olika pH-kontrollerade rötningsreaktorer som externa kolkällor under ett optimalt C/N-förhållande av 4,5. Som ett resultat av kompositionsskillnaden mellan VFA producerade från olika pH-miljöer, det observerades att med VFA från pH-10 kontrollerad reaktor denitrifikationskapacitet var något högre än med VFA från pH-5 och en icke-pH-kontrollerad reaktor. Vidare utfördes denitrifikationstest med användning av kemisk metod för jämförelse med manometrisk metod, och det visades att resultat erhållna från manometrisk denitrifikationstest var tillförlitliga och giltiga. De övergripande resultaten visar att VFA som produceras från anaerob rötning är en utmärkt extern kolkälla för denitrifikationsprocessen, vilket betyder att utnyttjandet av kolresursåtervinning från AVR är avgörande för nästa generations avloppsrening.

Located in the south-west region of Spencer Gulf, South Australia, a multi-million dollar aquaculture industry based on the ranching of southern bluefin tuna (Thunnus maccoyii) contributes significantly to the regional economy. The interaction between aquaculture activities and the environment is of significant interest to industry stakeholders, management authorities and the broader science community. No studies, to the best of my knowledge, have investigated the relationships between the hydrodynamics and biogeochemistry of the system and the ability of the benthic ecosystem to deal with the increased loads of organic material from aquaculture activities. This thesis uses a multi-disciplinary approach combined with modern statistical techniques to explore the linkages between hydrodynamics, sediment geochemistry, sedimentary nutrient cycling and the aquaculture industry. Modelling results have identified that swell entering the mouth of Spencer Gulf from directly south causes the greatest swell heights in the central tuna farming zone. Winds from the north-east through to south-east generate the greatest wind-wave heights in the central tuna farming zone. This is directly related to the available fetch. The energy contained in the locally generated wind waves was the same order of magnitude as that of the dissipated oceanic swells. Yet the incoming swell poses the greatest risk to aquaculture activities as the increased wave length causes swell energy to penetrate to the seafloor. The results of this work suggest that the sediment geochemistry is tightly coupled to both the hydrodynamic regime and the buildup of silt originating from aquaculture activities. In the more exposed regions of the tuna farming zone, periodic resuspension events caused by swell propagating into the area from the Southern Ocean, resuspend fine unconsolidated sediments into the lower 10 m of the water column. This material is then advected through the region by the residual (low-frequency) currents until it settles out in areas of lower energy. This process has created two distinct provinces within the region that can either be classified as depositional or erosional. The combined effect of wave action and tidal currents have generated a heterogeneous distribution of biogeochemical properties within the sediments. Denitrification rates were measured in these heterogeneous sediments using a novel technique based on Bayesian statistics to explicitly account for the spatial variability of the sediment biogeochemistry. The denitrification rates were found to be generally low, largely due to the lack of organic matter entering the sediments. However, adjacent to aquaculture activities, the high organic loads stimulate sedimentary denitrification, with rates reaching values of up to three orders of magnitude greater than the control sites. Denitrification efficiencies were high adjacent to the aquaculture activities, with up to 95% of the dissolved inorganic nitrogen produced from the breakdown of organic matter in the sediments being removed. Variability in the denitrification efficiencies was related to the textural characteristics of the sediments, with high efficiencies in finer sediments. It is proposed that this is due to the lower permeability of these sediments restricting the advective exchange of porewater nutrients.

Nitrogen pollution is a growing problem that is detrimental to the environment and the economy. Traditional treatment of nitrogen is a multi-stage process, expensive, operationally intensive, and requires large land areas. This research studied the effects of BiOWiSH® Aqua (Aqua), a biological enhancement product, on the simultaneous nitrification and denitrification process in a membrane aerated bioreactor (MABR) to determine if it is a feasible application for wastewater treatment. The MABR used during experimentation was a small-scale batch reactor with a continuous flow of air through a silicone membrane. The effect of carbon source and concentration on nitrogen removal rates and biomass growth/behavior were determined through a series of laboratory experiments with Aqua and wastewater. With glucose and solely Aqua cultures, average reduction rates in nitrogen concentrations were 1.2 mg-N/L/hour for all C:N ratios investigated. When wastewater was used as the main carbon source, creating a mix of wastewater and Aqua bacteria in the MABR, average reduction rates were 10.9 mg-N/L/hour. A maximum reduction rate of 21.3 mg-N/L/hour occurred at a 2:1 C:N ratio. This research concluded that pure Aqua cultures are not efficient at removing nitrogen or greatly augment the nitrogen reduction process. MABRs can use the biochemical oxygen demand in wastewater as a useful/viable carbon source. High carbon to nitrogen ratios (C:N ratio of 30:1) did not result in faster nitrogen reduction rates but did experience rapid biofilm growth and death. This shows that high C:N ratios are not an efficient operationally for MABRs due to the excess sludge created. C:N ratios of v approximately 3:1 provided the most consistent nitrogen reduction for both glucose and wastewater. This research concluded that C:N ratios, pH, and oxygen diffusion heavily affect the MABR’s performance. In addition, MABRs can utilize low C:N ratios during treatment, particularly during the treatment of high-strength wastewater.

Thesis (M.S. in environmental science)--Washington State University, May 2010.
Title from PDF title page (viewed on July 21, 2010). "School of Earth and Environmental Science." Includes bibliographical references (p. 23-28).

Advanced wastewater treatment plants must meet permit requirements for organics, solids, nutrients and indicator bacteria, while striving to do so in a cost effective manner. This requires meeting day-to-day fluctuations in climate, influent flows and pollutant loads as well as equipment availability with appropriate and effective process control measures. A study was carried out to assess performance and process control strategies at the Falkenburg Road Advanced Wastewater Treatment Plant in Hillsborough County, Florida. Three main areas for control of the wastewater treatment process are aeration, return and waste sludge flows, and addition of chemicals. The Falkenburg AWWTP uses oxidation ditches where both nitrification and denitrification take place simultaneously in a low dissolved oxygen, extended aeration environment. Anaerobic selectors before the oxidation ditches help control the growth of filamentous organisms and may also initiate biological phosphorus removal. The addition of aluminum sulfate for chemical phosphorus removal ensures phosphorus permit limits are met. Wasting is conducted by maintaining a desired mixed liquor suspended solids (MLSS) concentration in the oxidation ditches. For this study, activated sludge modeling was used to construct and calibrate a model of the plant. This required historical data to be collected and compiled, and supplemental sampling to be carried out. Kinetic parameters were adjusted in the model to achieve simultaneous nitrification-denitrification. A sensitivity analysis found maximum specific growth rates of nitrifying organisms and several half saturation constants to be influential to the model. Simulations were run with the calibrated model to observe relationships between sludge age, MLSS concentrations, influent loading, and effluent nitrogen concentrations. Although the case-study treatment plant is meeting discharge permit limits, there are several recommendations for improving operation performance and efficiency. Controlling wasting based on a target MLSS concentration causes wide swings in the sludge age of the system. Mixed liquor suspended solids concentration is a response variable to changes in sludge age and influent substrate. Chemical addition for phosphorus removal should also be optimized for cost savings. Finally, automation of aeration control using online analyzers will tighten control and reduce energy usage.

The Integrated Film Activated Sludge Process (IFAS) was developed to reduce the cost of additional facilities required to complete year round nitrification in the design of new or retrofit wastewater treatment plants. The purpose of this project was to develop a computer-based mechanistic model, called IFAS, which can be used as a tool by scientists and engineers to optimize their designs and to troubleshoot a full-scale treatment plant. The program also can be employed to assist researchers conducting their studies of IFAS wastewater treatment processes. IFAS enables the steady-state simulation of nitrification-denitrification processes as well as carbonaceous removal in systems utilizing integrated media, but this current version supports only sponge type media. The IFAS program was developed by incorporating empirical equations for integrated biofilm carbonaceous uptake and nitrification developed by Sen and Randall (1995) into the general activated sludge model, developed by the International Association on Water Quality (IAWQ, previously known as IAWRC), plus the biological phosphorus removal model of Wentzel et al (1989). The calibration and evaluation of the IFAS model was performed using existing data from both an IFAS system and a conventional activated sludge bench-scale plant operated over a wide range of Aerobic Mean Cell Residence Times (Aerobic MCRT's). The model developed provides a good fit and a reasonable prediction of the experimental data for both the IFAS and the conventional pilot-scale systems. The phosphorus removal component of the model has not yet been calibrated because of insufficient data and the lack of adequately defined parameters.
Master of Science

This thesis is comprised of two phases; the first phase concerns the effect of arsenic on the denitrification process in the presence of naturally-produced volatile fatty acids (VFAs); while the second phase evaluates the arsenic removal efficiency of New Zealand Iron Sand (NZIS) by adsorption. To accomplish the first phase of the study, VFAs were first produced naturally in an acid-phase anaerobic digester by using commercially-available soy flour. Secondly, a denitrifying biomass was cultivated in a sequencing batch reactor (SBR) using domestic wastewater as a feed solution. Finally, a series of biological denitrification batch tests were conducted in the presence of different concentrations of arsenic and nitrate. As mentioned, the VFAs were generated from an anaerobic digester using 40 g/L soy solution as a synthetic feed. The digester was operated at a solids retention time (SRT) and hydraulic retention time (HRT) of 10 days. The pH of the digester was measured to be 4.7 to 4.9 while the mean temperature was 31 ± 4 °C; however, both these parameters were not controlled. In the effluent of the digester, a mean VFA concentration of 5,997 ± 538 mg/L as acetic acid was achieved with acid speciation results of acetic (33 %), propionic (29 %), butyric (21 %), iso-valeric (5%) and n-valeric acid (12 %). The specific VFA production rate was estimated to be 0.028 mg VFA as acetic acid/mg VSS per day. The effluent sCOD was measured to be 14,800 mg/L (27.9 % of the total COD), as compared to 9,450 mg/L (16.8 % of total COD) in the influent of the digester. Thus, the COD solubilization increased by 11.1 % during digestion yielding a specific COD solubilization rate of 0.025 mg sCOD/mg VSS per day. The extent of the digestion process converting the substrate from particulate to soluble form was also evaluated via the specific TOC solubilization rate (0.008 mg TOC/mg VSS per day), and VSS reduction percentage (17.7 ± 1.8 %). A denitrifying biomass was developed successfully in an SBR fed with domestic sewage (100 % denitrification was achieved for the influent concentration of sCOD = 285 ± 45 mg/L and NH₄⁺-N = 32.5 ± 3.5 mg/L). A mean mixed liquor suspended solids (MLSS) of 3,007 ± 724 mg/L and a mean SRT of 20.7 ± 4.4 days were measured during the period of the research. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) measured to be between 50-120 mL/g (with a mean value of 87 ± 33 mL/g) resulting in a very low effluent solids concentration (in many cases less than 20 mg/L). Several preliminary tests were conducted to estimate the right dosage of VFAs (digester effluent), nitrates and arsenic to be added and to confirm the occurrence of denitrification in an appropriate time frame of 4-6 h. From these tests, an optimum C/N ratio was observed to be somewhere between 2 to 4, somewhat higher than all the theoretical C/N ratios required for a complete denitrification using the four major VFAs identified in the digester effluent. During the denitrification batch tests, it was also observed that some NO₃⁻- N was removed instantaneously by reacting with As (III) (As₂O₃); while an increase in alkalinity of around 5.60 mg as CaCO₃ produced per mg NO₃⁻- N reduction was also observed. This latter number was very close to the theoretical value of alkalinity production (i.e. 5.41 mg as CaCO₃ per mg NO₃⁻- N). The effect of arsenic on the denitrification process was evaluated by observing the specific denitrification rate in series of denitrification batch tests (with different concentrations of arsenic). Results from the denitrification batch tests showed that there was a clear effect for both As (III) and As (V) on denitrification. In particular, the specific denitrification rate fell from 0.37 to 0.01 g NO₃⁻- N /g VSS per day as the concentration of As (III) increased from 0 to 50 mg/L. In contrast, there was comparatively less effect for As (V); i.e. only a 37 % decrease in the specific denitrification rate (from 0.34 g NO₃⁻- N /g VSS per day to 0.23 g NO₃⁻- N /g VSS per day) when the initial arsenic concentration increased from 0 to a very high level of 2,000 mg/L. The effects of both the As (III) and As (V) forms of inorganic arsenic on the denitrification rate were further quantified by constructing exponential equation models. It was suspected that the effect of As (III) on denitrification was more substantial than the effect of As (V) because of the former’s toxicity to microbes. Finally, the fate of arsenic was tracked by examining bacterial uptake. During the normal denitrification batch tests (i.e. designed for evaluation of the effect of arsenic on denitrification), no significant arsenic removal was observed. However, additional batch tests with a comparatively low concentration of biomass revealed that the denitrifying biomass removed 1.35 µg As (III) /g dry biomass and 2.10 µg As (V) /g dry biomass. In the second phase of this research, a series of arsenic adsorption batch tests as well as a column test were performed to examine the arsenic (As (III) and As (V)) removal efficiency of NZIS from an arsenic-contaminated water. The kinetics and isotherms for adsorption were analysed in addition to studying the effect of pH during the batch tests. Breakthrough characteristics for both As (III) and As (V) were studied to appraise the effectiveness of NZIS treating an arsenic contaminated water. Batch tests were performed with different concentrations of arsenic as well as at different pH conditions. A maximum adsorption of As (III) of approximately 90 % occurred at a pH of 7.5, while the As (V) adsorption reached its maximum value of 97.6 % at a very low pH value of 3. Both Langmuir and Freundlich Models were tested and found to fit with R² values of more than 0.92 in all cases. From the Langmuir adsorption model, the maximum adsorption capacity of NZIS for As (III) was estimated to be 1,250 µg/g, significantly higher (about three times) than for As (V) of 500 µg/g. In column tests, arsenic-contaminated water with total As concentration of 400 µg/L (in either form of As) were treated and a pore volume (PV) of 700 and 300 yielded a total arsenic level less than the WHO guideline value of 10 µg/L for As (III) and As (V) respectively; while, the breakthrough occurred after a throughput of approximately 3,000 PV of As (III) and 2,700 PV of As (V) with an average flow rate of approximately 1.0 mL/min.

This paper is about improving the efficiency of nitrogen and other organic nutrient removal from activated sewage treatment by adopting an innovative technology. The work is to study the changes in nitrogen removal in pilot-scale experiments with the ITEST unit. The report also describes the various sources contributing to the eutrophication of the sea and water, caused by an increase in nutrient levels in different water bodies. Ineffective treatment of sewage contributes to the eutrophication. In the Baltic regions the temperature will be zero (0) or less than zero degree-centigrade during winter season. It results in decreased or fall in temperatures of incoming water to wastewater treatment plants. The temperature is an important parameter for sewage/wastewater treatment processes. Bacteriological nitrification and denitrification is an effective process for removing nitrogen from wastewater. From various research works and articles, it can be found that 23 + / - 2 °C, is the optimum temperature for nitrification and denitrification processes. So, the main aim is to study the effect of maintaining the incoming wastewater temperature by use of heat exchangers on incoming water to an activated sludge process line in pilot plant scale. In the pilot plant there were two testing lines; one line with heating system and the second line without heating system. A temperature of 19 to 20 °C was maintained in the influent to testing line. The nitrogen removal rates were compared between the two lines during the test period of approximately more than 8 months. Other biological activities in the treatment process were also compared between the two lines.

Groundwater represents the most important raw material. Germany struggles to maintain the best water quality possible by providing advanced monitoring systems and legal measures to prevent further pollution. In areas involved in the intensive growing of plantations, one of the major contamination factors derives from nitrate. The aim of this master thesis is the characterisation of the Water Protection Area of Bremen (Germany). Denitrification is a natural process, representing the best means of natural reduction of the hazardous nitrate ion, which is dangerous both for human health and for the development of eutrophication. The study has been possible thanks to the collaboration with the University of Bremen, the Geological Service of Bremen (GDfB) and Peter Spiedt (Water Supply Company of Bremen). It will be defined whether nitrate amounts in the groundwater still overcome the threshold legally imposed, and state if the denitrification process takes place, thanks to new samples collected in 2015 and their integration with historical data. Gas samples have been gathered to test them with the “N2/Ar method”, which is able to estimate the denitrification rate quantitatively. Analyses stated the effective occurrence of the reaction, nevertheless showing that it only affects the chemical of the deep aquifers and not shallow ones. Temporal trends concentrations of nitrate have shown that no real improvement took place in the past years. It will be commented that despite the denitrification being responsible for an efficacious lowering in the nitrate ion, it needs reactive materials to take place. Since the latter are finite elements, it is not an endless process. It is thus believed that is clearly necessary to adopt a better attitude in order to maintain the best chemical qualities possible in such an important area, providing drinking water.

With ever increasing regulation of the quality of drinking water and wastewater treatment, there is a need to develop methods to remove nitrogenous compounds from water. These processes are mediated by a variety of micro-organisms that can oxidise ammonia to nitrate, and then reduced to gaseous nitrogen by another set of organisms. This two stage process involves the relatively slow oxidation of ammonia to nitrate followed a relatively fast reduction of nitrate to nitrogen. Nitrate reduction normally requires anaerobic environments and the addition of organic matter to provide reducing power (electrons) for nitrate reduction. In practical situations the nitrate reduction can be problematic in those precise quantities of organic matter to ensure that the process occurs while not leaving residual organic matter. The aim of this study was to investigate microbial denitrification using electrochemical sources to replace organic matter as a redactant. The work also involved developing a system that could be optimised for nitrate removal in applied situations such as water processing in fish farming or drinking water, where high nitrate levels represent a potential health problem. Consequently, the study examined a range of developments for the removal of nitrate from water based on the development of electrochemical biotransformation systems for nitrate removal. This also offers considerable scope for the potential application of these systems in broader bio-nanotechnology based processes (particularly in bioremediation). The first stage of the study was to investigate the complex interactions between medium parameters and their effects on the bacterial growth rates. The results proved that acetate is a good carbon source for bacterial growth, and therefore it was used as an organic substrate for the biological process. High nitrate removal rate of almost 87% was successfully achieved by using a microbial fuel cell (MFC) enriched with soil inocula with the cathodes cells fed with nitrate and the anode fed with acetate. The maximum power density obtained was 1.26 mW/m2 at a current density of 10.23 mA/m2. The effects of acetate, nitrate and external resistance on current generation and denitrification activity were investigated, and the results demonstrated that nitrate removal was greatly dependent on the magnitude of current production within the MFC. Increase of acetate (anode) and nitrate (cathode) concentrations improved the process, while increasing external resistance reduced the activity. Furthermore, for a clear understanding of the nitrate reduction process, the analysis of the associated bacteria was performed through biochemical tests and examination of morphological characteristics. A diversity of nitrate reducing bacteria was observed; however a few were able to deliver complete denitrification. Pure cultures in MFC were examined and the voltage output achieved was about 36% of that obtained by mixed cultures. The nitrate removal gained was 56.2%, and this is almost 31% lower than that obtained by the mixed bacterial experiment. In an attempt to improve the MFC, modifications to the electrochemical properties of the electrode were investigated through the use of a cyclic voltammetry using carbon nanomaterials to coat the graphite felts electrodes. Among all the nanomaterials used in this study, graphitised carbon nanofibres (GCNFs) was selected for further investigation as it offered the best electrochemical performance and was thought to provide the largest active surface area. The performance of the MFC system coupled with the GCNFs modified electrodes was evaluated and significant improvements were observed. The highest voltage output achieved was about 41 mV with over 95% nitrate removal. The work is discussed in the context of improved MFC performance, potential analytic applications and further innovations using a bio-nanotechnology approach to analyse cell-electrode interactions.

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.

Two ecological models of nitrogen processes in treatment wetlands have been evaluated and compared. These models have been implemented, simulated, and visualized in the Modelica language. The differences and similarities between the Modelica modeling environment used in this thesis and other environments or tools for ecological modeling have been evaluated. The modeling tools evaluated are PowerSim, Simile, Stella, the MathModelica Model Editor, and WEST.

The evaluation and the analysis have been performed using McCall’s factors for software quality (McCall et al, 1977), a correlation analysis and the Constant Comparative Method (Glaser&Strauss, 1999). The results show that the modeling tools and the models can both be separated into two categories: Simple Components and Complex Components for the modeling tools, and Simple Models and Complex Models for the models. The major difference between the Simple Components and the Complex Components is the higher possibility of the Complex Components to create and reuse separate components and the higher complexity in these components. The similarities between the categories are that they are consistent, easy to overview and use, if no new components are to be created. The major difference between the Simple Models and the Complex models lies in the number of functions and in the possibility of reuse and expansion. The similarities between all the models are that they are all consequent, logical, valid, specialized, and easy to use if the user has programming skill.

To conclude thisthesis, the nitrogen decrease in a constructed treatment wetland can well be simulated using the Nitrification/Denitrification model expressed in Modelica and the MathModelica Model Editor. However, some changes to the Model Editor are recommended to make the creation of the model easier. The most important of these changes are the addition of a tutorial, the ddition of useful error handling and messages, and the removal of unnecessary Visio features.

This study describes the variation of an important greenhouse gas, nitrous oxide (N2O) at site-specific from the bio-lines unit at Wastewater Treatment Plant (WWTP) in Halmstad. The sampling campaign at the WWTP was carried out for three consecutive days during the weekdays in March 2021 with total of 144 samples were taken in GHG sample vials (exetainers) and analysed for N2O measurements using gas chromatography. Other nitrogen parameters data (NO2-N, NO3-N, and total nitrogen) were also collected. Using statistical analysis, comparisons were focused on a year period (March 2020 and 2021). This study found that N2O concentration generated in March 2021 was significantly lower than March 2020. Results also showed significant differences of N2O concentration between the three different zones (anaerobic, anoxic, and aerobic) among the bio-lines, where the highest N2O concentration was only found in aerobic zones. Correlation analysis showed only total nitrogen is negatively correlated with N2O-N in the aerobic zones. These findings will enable better understanding of processes along the bio-lines as a step for WWTP operators to improve N2O monitoring.

Este trabalho de doutorado apresenta os resultados da avaliação de duas configurações diferentes de reatores com biomassa imobilizada em matrizes cúbicas de poliuretano, denominados reator misto radial de leito fixo (RMRLF), utilizado para o tratamento de esgoto sanitário peneirado e reator aeróbio-anaeróbio horizontal de leito fixo (RAAHLF) para o pós-tratamento de efluente de reator de manta de lodo tipo upflow anaerobic sludge blanket (UASB) tratando esgoto sanitário. O estudo avalia duas propostas de tratamento para remoção biológica de matéria orgânica e nitrogênio por meio do acompanhamento do desempenho dos reatores sob diferentes condições operacionais, quais sejam: variação na carga orgânica aplicada, diferentes dosagens de solução alcalina e variação na taxa de aplicação de ar comprimido para o fornecimento de oxigênio dissolvido aos reatores na etapa de nitrificação. Foram desenvolvidos ensaios para obtenção de dados sobre o comportamento hidrodinâmico no RMRLF, dados sobre transferência e consumo de oxigênio dissolvido e viabilidade da utilização de biogás como doador de elétrons para a desnitrificação autótrofa. Os principais parâmetros de desempenho foram avaliados através de análises físico-químicas das amostras e a observação dos microrganismos envolvidos no processo. O RMRLF operou durante todo o período dos experimentos com a temperatura do líquido no seu interior variando entre o valor mínimo de 14 'GRAUS' Celsius até máximo de 30 'GRAUS' Celsius. Os valores da demanda química de oxigênio (DQO) no efluente do reator mantiveram média inferior a 50 mg/L. A remoção de nitrogênio como nitrato aumentou em 75% após o início do fornecimento do 'H IND.2'S' por meio da injeção de biogás. O RAAHLF operou com a temperatura do líquido no seu interior variando entre mínimo de 14 'GRAUS' Celsius e máximo de 26 'GRAUS' Celsius. Os valores de DQO no efluente, em média, foram inferiores a 66 mg/L e a remoção de nitrato foi incrementada em 87% após o fornecimento do 'H IND.2'S' pela injeção de biogás na câmara anóxica do reator. Os resultados demonstram o potencial destes reatores como alternativa para o tratamento e pós-tratamento de esgoto sanitário com resultados promissores de remoção de matéria orgânica e nitrogênio.
This work presents results of the evaluation of two different immobilized biomass reactor configurations, referred as radial flow anaerobic/aerobic immobilized biomass reactor (RAAIB) utilized for the treatment of the sanitary screened wastewater and horizontal aerobic/anaerobic immobilized biomass reactor (HAAIB) for the post-treatment of an upflow anaerobic sludge blanket reactor (UASB) treating sanitary wastewater. This study evaluates the two proposals for the biological organic matter and nitrogen removal by the evaluation of the reactors performance under several operational conditions, such as organic matter load variation, alkalinity solution feeding, variation on the compressed air supply for the nitrification step and biogas supply for the denitrification process. Assays were developed in order to obtain data on the hydrodynamic behavior in the RAAIB reactor, oxygen transfer and consumption and the viability of use biogas as electron donor for the autotrofic denitrification. The main performance parameters were measured thru physical-chemical analysis and microscopic observations. The RAAIB reactor was operated during all the experiment period with its liquid temperature varying from 14 'DEGREES' Celsius to 30 'DEGREES' Celsius. The chemical oxygen demand (COD) values in the effluent presented a mean value below 50 mg/L. The nitrogen as nitrate removal efficiency incresead up to 75% after supplying 'H IND.2'S' thru biogas injection. The HAAIB reactor operated with temperatures varying from 14 'DEGREES' Celsius to 26 'DEGREES' Celsius. The COD values in the effluent presented a concentration value lower than 66 mg/L and the nitrate removal increased 87% after supplying 'H IND.2'S' thru the biogas injection in the anoxic reactor. The collected data proved the viability of the use of these reactors as an alternative for the treatment and post-treatment of sanitary wastewater due to the promising results obtained in the assays performed in the reactors.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.
Industrial wastewater management pertaining to the mining industry has become increasingly stringent, with companies being required to develop environmentally benign wastewater management practices worldwide. The industries that utilise cyanide compounds for the recovery of precious and base metals in a process known as the cyanidation process, have contributed substantially to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. Hence, a biotechnological approach was undertaken in this study to remediate free cyanide (CN-) and thiocyanate (SCN-), which are the major chemical contaminants which are normally found in cyanidation wastewaters. Furthermore, this biotechnological approach was investigated to understand the fundamental aspects of using this approach such that the information gathered can be utilized in pilot plant studies. Therefore, bioprospecting of potential CN- and SCN--degrading organisms was undertaken using two approaches; (i) culture-dependent approach and (ii) culture-independent approach. Using the culture-dependent approach, Pseudomonas aeruginosa STK 03, Exiguobacterium acetylicum and Bacillus marisflavi were isolated from an oil spill site and river sediment samples, respectively. STK 03 was evaluated for the biodegradation of CN- and SCN- under alkaline conditions. The organism had a CN- degradation efficiency of 80% and 32% from an initial concentration of 250 and 450 mg CN-/L, respectively. Additionally, the organism was able to degrade SCN-, achieving a degradation efficiency of 78% and 98% from non- and CN- spiked cultures, respectively. Furthermore, the organism was capable of heterotrophic nitrification but was unable to denitrify aerobically, with the autotrophic degradation of CN- by STK 03 being abortive.

Under 90-talet uppdagades övergödningsproblematiken i Östersjön, varför omgivande länder enades gällande åtgärder för att minska problemen. De svenska reningsverk som genom sina utsläpp av kväve och fosfor påverkade Östersjön tvingades då införa gränsvärden för kväve- och fosforutsläppen. Vid Arboga reningsverk, vars recipient är Arbogaån som mynnar i Galten, Mälaren, har kvävereducering sedan en tid tillbaka varit i drift. Dock krävdes från och med år 2012 att totalkvävehalten i utgående avloppsvatten ej översteg 15 mg tot-N/l. Införandet av detta gränsvärde resulterade i åtgärder för att minska kväveutsläppen.Rejektvattenbehandling är en vanlig metod för att minska halterna totalkväve i utgående avloppsvatten. Normalt utgör rejektvattnet 0,5–1,0 % av totala inflödet till reningsverket men 10–20 % av inkommande totalkvävebelastningen. I Arboga resulterade det nya gränsvärdet för totalkväveutsläpp i en nybyggnation av en rejektvattenbehandling utformad med fördenitrifikation. Detta innebär att rejektvattnet pumpas genom fyra zoner, två anaeroba följt av två aeroba. Ammoniumkvävet i inkommande vatten omvandlas genom detta processupplägg via nitrat till kvävgas.Denna studie syftade till att kartlägga rejektvattenbehandlingens effekt på halterna av totalkväve i utgående avloppsvatten från Arboga reningsverk. Detta inkluderade både simuleringar i Benchmark Simulation Model no. 2 (BSM2) samt studier genom vattenprovtagning vid Arboga reningsverk. Vid simuleringarna genomförda i BSM2 påvisades en märkbart lägre halt totalkväve i utgående avloppsvatten efter rejektvattenbehandlingens införande. Även vid den provtagningscykel som genomfördes på Arboga reningsverk under april år 2012 påvisades att markanta förändringar skett i utgående halter totalkväve och ammoniumkväve. Halterna totalkväve och ammoniumkväve i utgående avloppsvatten sjönk med ca 40 % respektive 65 % relativt samma tidsperiod år 2008–2011. Detta är dock endast resultat från det initiala skedet av rejektvattenbehandlingen som togs i drift 16 februari år 2012. Studien visade sammanfattningsvis att denna typ av processlösning för rejektvattenbehandling ledde till lägre halter av totalkväve och ammoniumkväve i utgående vatten från Arboga reningsverk. Dock krävs vidare studier för att kartläggaden slutgiltiga effekten av rejektvattenbehandlingen, då den i nuläget ännu ej nått sin slutgiltiga kapacitet.
Eutrophication problems were discovered in the Baltic Sea during the 1990s, why thesurrounding countries came to an agreement regarding measures to reduce the problem. Swedish wastewater treatment plants that influence the Baltic Sea by their emissions ofnitrogen and phosphorus have since introduced limit values for nitrogen and phosphorusconcentrations in the effluent water.At Arboga wastewater treatment plant (WWTP) a nitrogen reduction process withactive sludge was implemented a few years back. The recipient Arbogaån leading intoGalten, Mälaren, has eutrophication issues, and from the year 2012 the concentration oftotal nitrogen in treated wastewater must not exceed 15 mg tot-N/l. This limit resulted inmeasures to reduce nitrogen emissions.Reject water treatment is a common method to reduce the levels of total nitrogen intreated wastewater. Normally, the reject water contributes to 0.5–1.0 % of the totalinflow to the treatment plant but 10–20 % of the incoming total nitrogen load. In Arboga, the new limit for total nitrogen emissions resulted in a reject water treatmentfacility with predenitrification. The reject water is routed through four zones, twoanaerobic followed by two aerobic. Ammonium is by this process converted in to nitrogen gas via nitrate. This study aimed at identifying the effect from what implementing a reject watertreatment on the levels of total nitrogen in treated wastewater from Arboga WWTP.This included simulations in the Benchmark Simulation Model no. 2 (BSM2) as well aswater sampling at Arboga WWTP. The simulations that were carried out in BSM2 showed a significantly lower content of total nitrogen in treated wastewater after thereject water treatment was implemented. The sampling cycle conducted at ArbogaWWTP in April 2012 revealed that changes occurred in the levels of total nitrogen andammonium in the effluent water. The concentrations of total nitrogen and ammonia nitrogen in treated wastewater decreased by about 40 % and 65 %, compared to thesame time period in 2008–2011. This is, however, only results from the initial stage ofthe reject water treatment, which began operating on February 16th 2012.In summary, this study showed that this type of process solution for reject watertreatment resulted in lower levels of total nitrogen and ammonia in the effluent water at  Arboga WWTP. Further studies are needed to determine the final efficiency of the rejectwater treatment, since it yet has to reach its full capacity.

Este trabalho apresenta o desempenho de um sistema de reatores seqüenciais em batelada aeróbio/anaeróbio, na remoção de matéria carbonácea (DQO) e nitrogenada, no tratamento de esgoto sanitário sintético, simulando esgoto doméstico. O sistema era composto por dois reatores dispostos em série, um aeróbio (RSBAe), responsável pela remoção de matéria carbonácea e nitrificação e outro, anaeróbio (RSBAn), responsável pela desnitrificação. Os reatores foram construídos em acrílico transparente, com volume total de 16,5 L e volume útil de 13,5 L. A operação dos reatores foi realizada com ciclos de 12h e 24h, na fase de adaptação, e de 24h, nas fases subseqüentes. O RSBAn foi agitado intermitentemente recirculando-se o biogás produzido e o RSBAe foi aerado/misturado continuamente. Foram testadas, como fontes de carbono para a desnitrificação, seis diferentes substratos, sendo que eram compostos por combinações dos constituintes do substrato sintético (variações percentuais de proteínas, carboidratos e lipídeos em termos de DQO), e as outras duas, metanol e etanol. A eficiência atingida, na remoção de DQO, foi em média de 95%, e as eficiências alcançadas na nitrificação e desnitrificação foram em média de 99%, para qualquer uma das fontes de carbono utilizadas.
This work presents the performance of (aerobic/anaerobic) sequencing batch reactors in the removal of carbonaceous (COD) and nitrogen matter treating synthetic substrate, simulating domestic wastewater. The system was composed of two reactors in series, one aerobic (RSBAe), responsible for the carbonaceous and nitrogen removal and another, anaerobic (RSBAn), responsible for denitrification. The reactors were built in transparent Plexiglas with total volume of 16,5 L and useful volume of 13,5 L. The reactors operation was carried out with cycles of 12h and 24h, in the adaptation phase, and 24h, in the other phases. The RSBAn were agitated intermittently by recycling the produced biogas and the RSBAe were aerated/agitated continuously. Six different subtracts were tested as carbon sources for denitrification four of them were composed by synthetic substrate combinations (percent variations of protein, carboidrates and lipids as COD) and the other two, methanol and ethanol. The COD removaI efficiency, in the COD removal, was about 95%, and the achieved efficiency in the nitrification and denitrification were about 99%, for any of the carbon source assayed.

På Käppalaverket i Stockholm står luftningen av de biologiska bassängerna för omkring en femtedel av verkets totala elenergiförbrukning. I ett försök att minska energikostnaden utvärderades under hösten 2010 nya metoder för luftflödesreglering på verket. Grundtanken var att styra luftflödet efter medelvärdet på utgående ammoniumkoncentration under en längre tid, istället för som idag efter momentana värden. Ett vanligt sätt att styra luftflöden på reningsverk idag är att använda återkoppling från utgående ammoniumkoncentration, vilket syftar till att alltid hålla den utgående koncentrationen vid ett valt börvärde. Lagstiftade gränsvärden på ammonium avser dock normalt medelvärden över en längre tid, såsom kvartal eller år. Istället för att anpassa luftflödet efter den inkommande belastningen är det därför möjligt att hålla luftflödet relativt konstant medan istället den utgående koncentrationen tillåts variera. I denna studie visades en energibesparing kunna erhållas om luftflödets variation reduceras. Två strategier utvärderades i vilka luftflödet respektive syrehalten hölls så konstant som möjligt. Dessa jämfördes med den idag använda styrstrategin på Käppalaverket, i vilken luftflödet anpassas efter den inkommande belastningen genom återkoppling. Studien inkluderade både simuleringar i modellen Benchmark Simulation Model no. 1 och fullskaleförsök på Käppalaverket. I både simuleringar och fullskaleförsök resulterade de två utvärderade strategierna i en lägre luftförbrukning per reningsgrad än den idag använda återkopplingsstrategin. I fullskaleförsöken erhölls en luftflödesreduktion på 11 % då luftflödet hölls konstant och 15 % då syrehalten hölls konstant. Båda strategierna genererade dock en kraftigt varierande utgående ammoniumkoncentration. Variationerna var störst då luftflödet hölls konstant och korrelerade inte med den dygnsbaserade belastningsprofilen. Sammanfattningsvis visade studien att en reducering av luftflödets variation resulterar i en lägre luftförbrukning men också i en ökad instabilitet. En konstant syrehalt gav en större energivinst och även en stabilare ammoniumreduktion än ett konstant luftflöde, varför denna metod har störst potential till vidare implementering i fullskala.
The aeration of the bioreactors is responsible for one fifth of the energy consumption at the Käppala wastewater treatment plant (WWTP) in Stockholm. In this report, new methods for aeration control were evaluated in order to reduce the energy costs at the plant. The main idea was to control the effluent ammonia concentration in terms of mean values instead of momentary values. A quite common approach for aeration control is to use feedback from the effluent ammonia concentration, thus aiming to keep the effluent concentration consistently at a certain set point. However, discharge limits normally refer to mean values over longer periods of time, such as months or years. Instead of adjusting the airflow to the incoming load it is therefore possible the keep the airflow fairly constant while allowing a fluctuating effluent concentration. In this paper, it was shown that by reducing the variation of the airflow, energy could be saved. Two methods were evaluated in which the airflow and oxygen concentration respectively was held constant. These methods were compared to the control strategy used today at the Käppala WWTP, where feedback control adjusts the airflow to the influent load. The study consisted of simulations with the Benchmark simulation model no. 1 (BSM1) as well as full scale experiments at the Käppala WWTP. Both the simulations and full scale experiments showed a reduced aeration per nutrient removal for the evaluated methods. In full scale, the total airflow reduction was 11 % when the airflow was held constant and 15 % when the oxygen concentration was held constant. However, the methods resulted in large variations of the effluent ammonia concentration, which did not correlate to the daily influent load. The variations were especially large when the airflow was held constant. In summary, this study showed that a reduced airflow variation results in lower aeration costs but also less stability. A constant oxygen concentration required less aeration and provided a more stable degree of ammonia removal than a constant airflow. For this reason, aeration control with a constant oxygen concentration has the best potential for further use at the Käppala WWTP.

This master thesis in energy optimization was made during the autumn of 2006 at Käppala wastewater treatment plant in Lidingö, Stockholm. A preceding thesis, where all electricity consumption was mapped, showed that the aeration in the biological treatment is the single largest consumer in the plant, and it is therefore of interest to reduce this cost. The oxygen control strategy used at Käppala WWTP is working well from a nutrient removal point of view, but not from an economic one. The last aerobic zones have a very low oxygen consumption during low loading periods which give rise to enhanced dissolved oxygen concentrations with excessive costs and reduced denitrification as a result. But also during periods of normal loading unnecessary high oxygen concentration are sometimes given.

By modifying the aeration control strategy three full-scale experiments have been made, with the intention to reduce the air consumption. The experiments were carried out during week 37-50 in the autumn of 2006 and showed that savings could be made.

The regular oxygen control at Käppala WWTP controls the oxygen level in the aerobic compartment with two DO-setpoints; one in the first aerobic zone and one in the last. The zones in between are controlled by an airflow fractionation depending on the oxygen level in the first and last zone. In the first strategy to be evaluated, all four zones in the aerated part were individually controlled with its own setpoint. Two different setpoint combinations were tested. By using the fact that the efficiency in the oxygen transfer rate was higher at low airflows, savings of approximately 16 % were achieved. In the second strategy tested, an ammonia-feedback control combined with a DO-feedback controlled the DO-set point in the first aerobic zone. This strategy adjusted the DO- set points to the loading variations, and this gave a decreased airflow of approximately 9 %. Finally the two strategies were combined. All zones were then controlled individually with DO-set points set by an ammonium-feedback and a DO-feedback. The strategy gave savings in the airflow of approximately 18 %. In all three trials the aerated zones were more efficiently used, and the estimated savings are 550 000 SEK/year, and with a preserved nutrient removal efficiency.

Under hösten 2006 har ett examensarbete om energieffektivisering på Käppalaverket på Lidingö utförts. Ett föregående examensarbete där all elenergiförbrukning kartlades visade att blåsmaskinerna i biosteget står för den enskilt största förbrukningen i verket och det är därför av intresse att minska denna kostnad. Syrestyrningsstrategin som används på Käppalaverket fungerar mycket bra ur reningssynpunkt, men är inte optimal ur energisynpunkt. Dels luftas de första aeroba zonerna för mycket vid låg belastning vilket ger upphov till kraftigt förhöjda syrekoncentrationer i de sista aeroba zonerna med höga luftningskostnader och risk för försämrad denitrifikation, men även under normal belastning har det visat sig att onödigt höga syrekoncentrationer ibland ges.

Tre fullskaliga optimeringsförsök har utförts, med syfte att minska luftförbrukningen med bibehållen reningsgrad. Försöken pågick från vecka 37 till 50 hösten 2006, och visade att det finns möjlighet att spara energi genom att modifiera syrestyrningsstrategin.

Den reguljära syreregleringen i Käppalaverket styr syrehalten i den aeroba bassängen mot två syrebörvärden; ett i den första luftade zonen och ett i den sista. Luftflödet till de mellanliggande zonerna styrs av luftflödesandelar beroende på syrehalten i dessa två zoner. Den första strategin som utvärderades styrde istället samtliga zoner individuellt med egna börvärden, där två olika strukturer på de satta börvärdena användes. Genom att utnyttja en högre effektivitet i syreöverföringshastigheten vid låga luftflöden uppnåddes luftflödesbesparingar på ca 16 % i första försöket.

I den andra strategin styrdes syrebörvärdet i den första luftade zonen med hjälp av två återkopplingar, en från utgående ammoniumhalt och en från syrehalten i den sista luftade zonen.

Tack vare att strategin anpassade syrebörvärdena efter belastningen av syretärande ämnen erhölls luftflödesbesparingar på ca 9 %. Slutligen kombinerades de två strategierna; samtliga zoner styrdes individuellt med börvärden satta av en ammonium-återkoppling och en syre-återkoppling. Strategin medförde luftflödesbesparingar på ca 18 %. I samtliga försök utnyttjades de luftade zonerna bättre, och besparingspotentialen uträknad från 2005 års elpriser blev som mest 550 000 SEK/år, detta med en bibehållen reningsgrad.

One of the main problems of diffused groundwater contamination is produced by nitrate (NO3‾). NO3‾ pollution is linked with fertilizer application, manure management and wastewater. Many areas of Spain have NO3‾ concentration over the human consumption (0.8 mM NO3‾) established by the Directive 98/83/CE. Endorheic basins located in semiarid or arid regions constitute one of the most vulnerable environments to NO3‾ pollution. The Petrola basin (Central Spain) is an outstanding example of these endorheic systems. Nitrate concentration in surface and groundwater from Petrola basin ranged from <1.6x10-3 mM to 2.5 mM. The observed variation in NO3‾ concentration could be linked with naturalattenuation. In this basin two different sediments are able to produce denitrification: 1) the organic and sulphide-rich sediment from the Utrillas Facies (Lower Cretaceous) and 2) the bottom lake sediment. Laboratory experiments coupled with field data can be applied to improve the understanding of the nitrogen cycle in Petrola basin. The study of Cretaceous Utrillas Facies and bottom lake sediments in laboratory experiments combining multi-isotopic techniques and chemical data showed that natural attenuation produced by both materials was mainly linked with the oxidation of the organic matter. In the case of Utrillas Facies, isotopic values of δ34SSO4 and δ18OSO4 ruled out pyrite as electron donor. Bottom lake sediments showed higher potential to remove NO3‾ than the Utrillas Facies. Important differences between both sediments were observed in the amount of reactive organic carbon, and in the nitrogen reduction rate. These differences were linked to the variation in the reactivity of the different organic carbon sources. Despite the remarkable differences, similar isotopic fractionation of N and O during denitrification for the Utrillas Facies and the bottom lake sediment were observed. The Utrillas Facies displayed values of ‾11.6‰ and ‾15.7‰ for εN and ‾12.1‰ and ‾13.8‰ for εO whereas denitrification produced by the bottom lake sediments showed εN of ‾14.7‰ and εO of ‾14.5‰. The hydrogeological study showed that groundwater flow in the Petrola basin can be considered as the result of two main flow components: a regional groundwater flow, from the recharge areas (Zone 1) to the discharge ones located near the lake (Zone 2) and the density driven flow from surface water from the lake towards the underlying aquifer (Zone 3). Isotopic results from the field showed that denitrification was taking place in the basin although it was restricted to the surrounding area (Zone 2) and under the lake (Zone 3). In addition, the using the isotopic fractionations obtained in the laboratory experiments, the percentage of NO3 ‾ attenuation was calculated. NO3‾ removed ranged from 0% to 60% with an average percentage of 20%. The degree of denitrification observed at field scale showed an important spatial variability related with the amount, availability and reactivity of labile organic matter as well as spatial variation of NO3‾ supply. Attenuation processes by heterotrophic denitrification reactions were more likely to occur in zones of the saline lake-aquifer system. Density downflow from surface water effectively transported the DOC to aquifer zones under reducing conditions; however, its influence decreased with depth becoming negligible in the deepest part of the aquifer. As consequence of the incomplete NO3‾ attenuation observed in groundwater of Petrola basin a biostimulation treatment was proposed. Periodically injecting an organic carbon source might be a suitable method to remove NO3‾ from groundwater during long-term treatments. The induced attenuation experiment showed that the injection of glucose enhanced denitrification. Remarkable presence of NO2‾ was produced during the first days due to enzymatic repression of nitrite reductase as well as the pH conditions of the system. Changes in C/N ratio to stoichiometric or lower ratio did not further affect the achieved complete NO3‾ attenuation because secondary carbon sources were available in the system (DOC in the input water and/or biofilms). The isotopic fractionation values of N and O during induced denitrification were ‾8.8‰ and ‾8.0‰ respectively.
Esta tesis se centra en la descripción y cuantificación de los procesos de atenuación natural del nitrato en la cuenca endorreica de Pétrola. Para ello se realizan diversos experimentos en columna y batch con sedimentos de la cuenca para determinar el potencial de atenuación de todos ellos caracterizándolos, química e isotópicamente. Los resultados obtenidos permitieron evaluar ambos sedimentos como una fuente de electrones capaz de producir procesos de atenuación mediante desnitrificación heterótrofa. A continuación los procesos y conocer la extensión de los mismos. La atenuación producida en la cuenca llega hasta el 60% pero la media es tan solo de un 20%. Mediante el estudio hidrogeológico se identifican las zonas de la cuenca donde se está produciendo la atenuación así como el papel de los sedimentos estudiados. Finalmente, como la atenuación natural no consigue la completa eliminación del nitrato, se propone un tratamiento de remediación, realizando un primer ensayo de bioestimulación periódica en columna utilizando glucosa. Los resultados obtenidos mostraron como un tratamiento viable utilizando una cantidad de glucosa por debajo de la estequiométrica debido a los fuentes secundarias de electrones presentes en el sistema.

Thesis (MScEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: Urine contains up to 80% of nitrogen, 50 % of phosphates and 90 % of potassium of the total load in domestic wastewater but makes up less than 1% of the total volume (Larsen et al., 1996). The source separation and separate treatment of this concentrated waste stream can have various downstream advantages on wastewater infrastructure and treated effluent quality. The handling of undiluted source separated urine however poses various challenges from the origin onward. The urine has to be transported to a point of discharge and ultimately has to be treated in order to remove the high loads of organics and nutrients. Wilsenach (2006) proposed onsite treatment of source separated urine in a sequencing batch reactor before discharging it into the sewer system. This study focused on the treatment of urine in a sequencing batch reactor (SBR) primarily for removal of nitrogen through biological nitrification-denitrification. The aim of the study was to determine nitrification and denitrification kinetics of undiluted urine as well as quantification of the stoichiometric reactions. A further objective was to develop a mathematical model for nitrification and denitrification of urine using experimental data from the SBR. The SBR was operated in 24 hour cycles consisting of an anoxic denitrification phase and an aerobic nitrification phase. The sludge age and hydraulic retention time was maintained at 20 days. pH was controlled through influent urine during volume exchanges. Undiluted urine for the study was obtained from a source separation system at an office at the CSIR campus in Stellenbosch. Conditions in the reactor were monitored by online temperature, pH and ORP probes. The OUR of the system was also measured online. One of the main challenges in the biological treatment of undiluted urine was the inhibiting effect thereof on nitrification rate. The anoxic mass fraction was therefore limited to 17 % in order to allow longer aerobic phases and compensate for the slow nitrification rates. Volume exchanges were also limited to 5% of the reactor volume in order to maintain pH within optimal range. Samples from the reactor were analysed for TKN, FSA-N, nitrite-N, nitrate-N and COD. From the analytical results it was concluded that ammonia oxidising organisms and nitrite oxidising organism were inhibited as significant concentrations of ammonia-N and nitrite-N were present in the effluent. It was also concluded that nitrite oxidising organisms were more severely inhibited than ammonia oxidising organisms as nitrate-N was present in very low concentrations in the effluent and in some instances not present at all. Ultimately the experimental system was capable of converting 66% of FSA-N to nitrite- N/nitrate-N of which 44% was converted to nitrogen gas. On average 48% of COD was removed. A mathematical model was developed in spreadsheet form using a time step integration method. The model was calibrated with measured online data from the SBR and evaluated by comparing the output with analytical results. Biomass in the model was devised into three groups, namely heterotrophic organisms, autotrophic ammonia oxidisers (AAO) and autotrophic nitrite oxidisers (ANO). It was found that biomass fractionation into these three groups of 40% heterotrophs, 30% AAO and 30% ANO produced best results. The model was capable of reproducing the general trends of changes in substrate for the various organism groups as well as OUR. The accuracy of the results however varies and nearexact results were not always achievable. The model has some imperfections and limitations but provides a basis for future work.

A remoção de nitrogênio acoplada à oxidação de sulfeto pode ser uma opção adequada para o pós-tratamento de efluentes de reatores anaeróbios, os quais contêm nitrogênio amoniacal, que deve ser nitrificado, e sulfeto, que poderia ser utilizado como doador de elétrons endógeno para a desnitrificação autotrófica. Com base nessa constatação, esta pesquisa propôs a aplicação da nitrificação e desnitrificação autotrófica acoplada à oxidação de sulfeto, em um único reator, para a remoção de nitrogênio de efluentes de reatores anaeróbios tratando esgoto sanitário. Visto que existem lacunas na literatura referente ao processo desnitrificante autotrófico citado, as bases teóricas para a determinação das condições operacionais partiram da caracterização cinética e de aspectos fundamentais da desnitrificação autotrófica com uso de sulfeto como doador de elétrons. Numa primeira etapa, avaliou-se o efeito da concentração de sulfeto na desnitrificação, com uso de nitrato e nitrito como receptores de elétrons, em reatores verticais de leito fixo. Os resultados revelaram que compostos intermediários de enxofre foram principalmente formados quando se aplicou excesso de sulfeto, fato que foi mais evidente com o uso de nitrato. Evidências visuais sugeriram que enxofre elementar foi o principal intermediário formado, o qual também estava sendo utilizado quando aplicadas concentrações estequiométricas de sulfeto relativas a nitrato/nitrito. De modo geral, a desnitrificação autotrófica não foi afetada pela desnitrificação heterotrófica residual via atividade endogênica. Numa segunda etapa, determinou-se a cinética intrínseca da desnitrificação autotrófica via nitrato e nitrito com uso de diferentes concentrações de sulfeto em reatores diferenciais de leito fixo. Este bioprocesso pôde ser descrito por modelo cinético de ordem ½ para biofilmes. As constantes cinéticas variaram entre 0,425-0,658 mg N1/2 / L1/2 h para desnitrificação via nitrito e entre 0,190-0,609 mg N1/2 / L1/2 h para desnitrificação via nitrato. Neste último, o menor valor foi devido ao uso de elétrons doados a partir de compostos intermediários de enxofre formados. Numa terceira etapa, utilizou-se um reator de leito fixo operado em batelada alimentada seqüencial, com ciclos de 8 horas, submetido à aeração intermitente e empregando a desnitrificação autotrófica com uso de sulfeto presente no efluente sanitário, pré-tratado anaerobiamente, como doador de elétrons. O prévio estabelecimento da nitrificação com posterior aplicação de baixas concentrações de sulfeto foi a melhor estratégia de partida do reator. A alimentação em batelada alimentada com aplicação de sulfeto em excesso apenas nos períodos anóxicos foi a melhor estratégia de alimentação, proporcionando eficiência média de 85,7% e 53,0% para nitrificação e desnitrificação, respectivamente. O acúmulo de nitrito foi observado após aplicação de carga de choque de sulfeto, que inibiu as bactérias oxidadoras de nitrito. No entanto, houve dificuldade em se estabelecer a desnitrificação via nitrito em função da toxicidade deste composto aos organismos desnitrificantes instalados no reator. A baixa eficiência global de remoção de nitrogênio e algumas restrições operacionais indicaram que a desnitrificação autotrófica usando sulfeto em um único reator operado em bateladas seqüenciais não foi adequada para a proposta desta pesquisa.
Nitrogen removal coupled with sulfide oxidation may be suitable for the post treatment of effluents from anaerobic reactors. These effluents contain ammonium, which must be nitrified, and sulfide, which could be used as an endogenous electron donor for autotrophic denitrification. Since there are gaps in literature regarding the mentioned autotrophic denitrifying process, the theoretical basis for determination of operating conditions came from the characterization of kinetics and fundamentals aspects of autotrophic denitrification using sulfide as electron donor. In a first step, the effect of sulfide concentration on this bioprocess using nitrate and nitrite as electron acceptors in vertical fixed-bed reactors was evaluated. The results showed that intermediary sulfur compounds were mainly produced when excess of electron donor was applied, which was more evident when nitrate was used. Visual evidences suggested that elemental sulfur was the intermediary compound produced. There was also evidence that the elemental sulfur previously formed was being used when sulfide was applied in stoichiometric concentration relative to nitrate/nitrite. For all conditions assayed, autotrophic denitrification was not affected by residual heterotrophic denitrification via endogenic activity, occurring as a minor additional nitrogen removal process. In a second step, the intrinsic kinetics of sulfide-oxidizing autotrophic denitrification via nitrate and nitrite in systems containing attached cells was determined. Differential reactors were fed with nitrified synthetic domestic sewage and different sulfide concentrations. This bioprocess could be described by a half-order kinetic model for biofilms. The half-order kinetic coefficients ranged from 0.425 to 0.658 mg N1/2 / L1/2 h for denitrification via nitrite and from 0.190 to 0.609 mg N1/2 / L1/2 h for denitrification via nitrate. In this latter, the lower value was due to the use of electrons donated from intermediary sulfur compounds formed. In a third step, a sequencing fed-batch biofilm reactor of 8-h cycles was operated under intermittent aeration, applying autotrophic denitrification using sulfide present in the sanitary effluent, anaerobically pre-treated, as electron donor. The effect of the start-up period and the feeding strategy were evaluated. The previous establishment of nitrification process with subsequent application of sulfide in low concentrations was the best start-up strategy. The fed-batch mode with sulfide application in excess only in the anoxic periods was the best feeding strategy, providing average efficiencies of 85.7% and 53.0% for nitrification and denitrification, respectively. Nitrite accumulation was observed after application of shock loading of sulfide, which inhibited nitrite-oxidizing bacteria. However, it was difficult to establish denitrification via nitrite due to the toxicity of this compound to denitrifying organisms developed inside the reactor. The low overall efficiency of nitrogen removal and some operational constraints indicated that autotrophic denitrification using sulfide in a single sequencing fed-batch reactor was not suitable for the purpose of this research.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The swine industry has shown strong development and, thus, has produced large volumes of effluents that must be correctly managed. Therefore, when such effluent cannot be released into soil, a treatment must be carried out to avoid environmental impacts of swine wastewater. Nitrogen is one of the elements that takes part in swine waste and it must be under constant evaluation, but, in some cases, it must be removed. Nitrification/denitrification (NDF) process is a frequent applied technology. However, when the effluent presents low C/N ratio, such as effluents after anaerobic processes, there is some decrease on denitrification efficiency and the total nitrogen removal can be affected. In this case, Nitritation/denitritation (NDT) process can be used to improve the system performance as well as save energy cost with aeration and external source of carbon due to the lower C/N requirement. Thus, this study aimed at evaluating swine wastewater based on NDF and NDT processes at different C/N ratios in order to obtain a system with efficient nitrogen removal and low oxygen and carbon consumption. Four phases were carried out during this experiment: Phase I) DO from 2.0-3.0 mgO2L-1 to 1.5 C/N; Phase II) DO from 0.6-0.7 mgO2L-1 to 1.5 C/N; Phase III) DO from 0.6 to 0.7 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75 and 0.6); Phase IV) DO from 2.0 to 3.0 mgO2L-1, different C/N ratios (1.5, 0.9, 0.75, and 0.6). The best operational condition was obtained at nitritation/denitritation process, whose C/N ratio was 0.9, and the optimum N removal was 86.3%. Under this condition, the system saved almost 36.8% of total organic carbon consumption and nearly 74% of dissolved oxygen consumed when compared to the conventional process for N-removal. This strategy can be very useful for nitrogen removal with low carbon rates, as the digestate from anaerobic processes.
A atividade suinocultura tem apresentado forte crescimento, e assim vem produzindo grandes volumes de efluentes que devem ser corretamente administrados. Portanto, quando não é possível a aplicação deste tipo de efluente no solo, o tratamento deve ser aplicado para que se evitem impactos ambientais. O nitrogênio é um dos elementos presentes nos dejetos de suínos que deve estar sob constante avaliação, e em alguns casos deve ser removido. O processo de nitrificação/desnitrificação (NDF) é uma tecnologia frequentemente aplicada, porém, quando o efluente apresenta baixa relação C/N, como efluentes pós-processos anaeróbios, a eficiência da desnitrificação é reduzida e a remoção de nitrogênio total pode ser afetada. Neste caso, o processo de nitritação/desnitritação (NDT) pode ser utilizado para melhorar o desempenho do sistema e economizar energia com aeração e com fonte externa de carbono, devido ao requisito de baixa relação C/N. Assim, o objetivo deste estudo foi avaliar a água residuária de suinocultura utilizando nitrificação/desnitrificação e nitritação/desnitritação em diferentes relações C/N, a fim de se obter um sistema com eficiente remoção de nitrogênio e baixo consumo de oxigênio e carbono. Quatro fases foram realizadas durante o experimento: Fase I) OD entre 2,0-3,0 mgO2 L-1 (nitrificação) e C/N 1,5; Fase II) OD entre 0,6-0,7 mgO2 L-1 (nitritação), e C/N 1,5; Fase III) OD entre 0,6-0,7 mgO2 L-1, diferentes relações C/N (1,5, 0,9, 0,75 e 0,6); Fase IV) OD entre 2,0-3,0 mgO2 L-1, diferentes relações de C/N (1,5, 0,9, 0,75 e 0,6). A melhor condição operacional foi encontrada no processo nitritação/desnitritação, com relação C/N de 0,9, cuja remoção de N considerada ótima foi de 86,3%. Nesta condição, a economia do sistema foi de 36,8% do consumo total de carbono orgânico e de cerca de 74% do consumo de oxigênio dissolvido, quando comparado com o processo convencional de remoção de N. Esta estratégia pode ser muito útil para a remoção do nitrogênio de efluentes de baixo teor de carbono, como os provenientes de processos anaeróbios.

This thesis focuses on the study of the global green house gas (GHG) emissions from wastewater systems. Nitrous oxide (N2O) and methane (CH4) are the main GHG directly emitted from wastewater treatment plants (WWTP). In this thesis, different studies were performed in order to determine the N2O production when using different combination of electron acceptors during denitrification. Firstly, three different external carbon sources where used in a mixed denitrifying culture. Secondly, a denitrifying polyphosphate accumulating organism (dPAO) and a denitrifying glycogen accumulating organism (dGAO) enriched cultures were used to assess the effect of using an internal carbon source (polyhydroxyalkanoates, PHA) for denitrification on the N2O production. Results indicated that electron competition during the reduction of different nitrogen oxides is a significant factor in ordinary heterotrophic denitrification processes using external carbon sources as the electron donor, but not in PHA-driven denitrification processes conducted by dPAO or dGAO. Results also showed that generally, higher N2O accumulation was detected in the tests conducted with dGAO than those conducted with dPAO, especially when nitrite was used as electron acceptor. Later, the effect of DO at a constant pH level and the effect of pH at a constant DO level on N2O and NO production in a partial nitrification sequencing batch reactor (SBR) were explored. Also, the relationship between NO production and the ammonia oxidation rate (AOR) as well as the N2O production rate and the AOR were studied. Results showed that these relationships were linear and exponential, respectively. This investigation highlighted the importance of also monitoring NO emissions since they may lead to N2O emissions. The last investigation of this thesis was a long-term full-scale study in the WWTP of Girona in order to assess the N2O and CH4 emission dynamics of the plug-flow reactors. Results showed seasonal and spatial variations on N2O emissions but only spatial variations on CH4 emissions. Finally, the overall carbon footprint of the plug-flow reactor was assessed.
Aquesta tesi està centrada en l'estudi de les emissions dels gasos d'efecte hivernacle (GEH) dels sistemes de tractament d'aigua residual. L'òxid nitrós (N2O) i el metà (CH4) són els principals GEH emesos directament en les estacions depuradores d'aigües residuals (EDAR). En aquesta tesi s'han realitzat diferents estudis per a identificar la producció de N2O usant diferents combinacions d'acceptors d'electrons durant la desnitrificació. En primer lloc es varen utilitzar tres fonts de carboni externes en un cultiu mix desnitrificant. En segon lloc es va utilitzar un cultiu enriquit amb organismes desnitrificants acumuladors de fòsfor (dPAO) i un cultiu enriquit amb organismes desnitrificants acumuladors de glicogen (dGAO) per tal d'avaluar l'efecte d'utilitzar una font de carboni interna (polihidroxialcanoats, PHA) per la desnitrificació en la producció de N2O. Els resultats van indicar que la competició d'electrons durant la reducció dels diferents òxids de nitrogen és un factor significatiu en els processos de desnitrificació heterotròfica ordinària utilitzant fonts de carboni externes com a donador d'electrons però no en els processos de desnitrificació utilitzant PHA com a font de carboni interna com en els dPAO i dGAO. Els resultats també varen demostrar que generalment en els experiments realitzats amb els dGAOs es detectava una acumulació major de N2O que en els experiments amb dPAOs, especialment quan s'utilitzava nitrit com a acceptor d'electrons. Més endavant es va explorar l'efecte del oxigen dissolt (DO) a un nivell constant de pH i l'efecte del pH a un nivell constant de DO en la producció de N2O i NO en la nitrificació parcial en un reactor discontinu seqüencial (SBR). També es va estudiar la relació entre la producció de NO i la velocitat d'oxidació d'amoni (AOR) així com la producció de N2O i la AOR. Els resultats van mostrar que les relacions eren lineal i exponencial, respectivament. Aquesta investigació va destacar la importància de supervisar també les emissions de NO, ja que poden conduir a emissions de N2O. L'última investigació d'aquesta tesi va ser un estudi a l'EDAR de Girona per a avaluar les dinàmiques d'emissions de N2O i CH4 en els reactors de flux pistó. Els resultats van mostrar variacions estacionals i espacials en les emissions de N2O en el reactor de flux pistó però només variacions espacials en les emissions de CH4. Finalment, es va avaluar la petjada de carboni global del reactor flux pistó.