A series of lab-scaled digestion studies including conventional mesophilic anaerobic digestion(MAD), thermophilic anaerobic digestion (TAD) at a range of treatment temperatures, and mesophilic high solids digestion of thermally pretreated wastewater sludge (THD) were carried out. Enhanced digestion performance in terms of solids destruction and methane generation by THD relative to MAD was achieved, and was largely attributable to the solubilization and subsequent biodegradation of energy-rich substrates within blended primary and secondary sludge. TAD was observed to underperform MAD, especially at elevated temperatures as methanogenic inhibition resulted in the accumulation of headspace hydrogen, thus resulting in poor removal of volatile fatty acids. The thermodynamics of fatty acid metabolism was favorable at each digestion temperature, thus it was concluded that microbial inhibition was the controlling factor in poor thermophilic performance. Inhibition by free unionized ammonia (NH₃) was characterized for THD and MAD biomass. Acetic acid degradation was equally affected over a range of NH₃ concentrations; however, methane generation by THD was less sensitive to ammonia inhibition, thus suggesting that methanogenesis by THD was less dependent on the NH₃-sensitive process of aceticlastic methanogenesis. Total ammonia nitrogen (TAN) and bicarbonate alkalinity were stoichiometrically produced from proteinaceous material during thermal hydrolytic pretreatment and subsequent high solids anaerobic digestion. Combined effects of TAN and high pH resulted in NH₃-inhibition during THD. Kinetic evaluations suggested that a growth rate reduction of approximately 65% was associated with in-situ NH₃ concentrations of the THD reactor. NH₃-inhibition was apparently responsible for a shift in dominant methanogenic community of the aceticlastic Methanosarcina barkeri in MAD to the hydrogenotrophic Methanoculleus bourgensis in THD. A similar shift in methanogenic community was observed between low temperature thermophilic digestion at 47°C, where the dominant order was Methanosarcinales, to high temperature thermophilic digestion at 59°C where the dominant order was Methanobacteriales. These findings support a process-driven pathway shift from aceticlastic to non-aceticlastic methanogenesis between 180 and 290 mg/L NH₃-N. Such a threshold is supported by previous literature related to ammonia tolerance of pure cultures of methanogens and has significant implications for the kinetic design of advanced anaerobic digestion processes. / Ph. D.

Sludge digestion has gained importance in recent year because of increasing interest in energy recovery and public concern over the safety of land applied biosolids. Many new alternatives are being researched for reducing excess sludge production and for more energy production. With an increase in solids destruction, the nutrients that are contained in sludge especially nitrogen, are released to solution and can be recycled as part of filtrate or centrate stream. Nitrogen has gained importance because it has adverse effects on ecosystem's as well as human health. NH₄⁺, NO₂⁻, NO₃⁻-, and organic nitrogen are the different forms of nitrogen found in wastewater. While ammonia is toxic to aquatic life, any form of nitrogen can be utilized by cyanobacteria and result in eutrophication. NO₂/NO₃, if consumed by infants through water, can affect the oxygen uptake capability. Hence, removal of nitrogen from wastewater stream before discharging is important. The main purpose of this study was to evaluate the performance of the Cambi process, a thermophylic hydrolysis process used as a pre-treatment step prior to anaerobic digestion. Thermal hydrolysis, as a pre-treatment to anaerobic digestion increases the biological degradation of organic volatile solids and biogas production. The thermal hydrolysis process destroys pathogens and hydrolysis makes the sludge readily available for digestion, while at the same time facilitating a higher degree of separation of solid and liquid phases after digestion. Experiments were conducted in three phases for anaerobic digestion using the Cambi process as pre-treatment. The phases of study includes comparison of two temperatures for thermal hydrolysis (Cambi 150°C and Cambi 170°C), comparison of two solid retention times in anaerobic digestion (15 Day and 20 Day) and comparison of two mesophilic temperatures in anaerobic digestion (37°C and 42°C). Different experimental analyses were conducted for each phase, such as pH, bio-gas production, COD removal, VS destruction, nitrogen removal, odor and dewatering characteristics and the results are compared among all the phases. The second part of the study deals with aerobic digestion of anaerobically digested sludge for effective nitrogen removal and additional VS destruction, COD removal. An aerobic digester is operated downstream to anaerobic digester and is operated with aerobic/anoxic phase for nitrification and de-nitrification. The aerobic/anoxic phases are operated in time cycles which included 40minutes/20minutes, 20minutes/20minutes, full aeration, 10minutes/30minutes, and 12minutes/12minutes. Different time cycles are experimented and aerobic digester is optimized for effective nitrogen removal. 12minutes aerobic and 12minutes anoxic phase gave better nitrogen removal compared to all the cycles. Over all the aerobic digester gave about 92% ammonia removal, 70% VS destruction and 70% COD removal. The oxygen uptake rates (OUR's) in the aerobic digester are measured corresponding to maximum nitrogen removal. The OUR's are found to be close to 60 mg/L during maximum nitrogen removal. The effluent from both anaerobic digester and aerobic digester was collected and analyzed for dewatering capability, cake solids concentration and odor potential. / Master of Science

This study is aimed to provide comprehensive evaluation and mechanistic understanding of the impact of process intensification techniques applied in main and side stream wastewater treatment on biosolids management in terms of anaerobic digestion enhancement, dewaterability improvement, odor mitigation, as well as phosphorus and nitrogen removal. The first part of this study was conducted to understand the effect of anaerobic digester solids retention time (SRT) on odor emission from biosolids. A kinetic model and inhibitory studies showed the emission of methanethiol (MT), a representative odor compound, was primarily determined by the dynamic concurrence of MT production from amino acid and utilization by methanogens in the course of anaerobic digestion. MT emission pattern follows a bell-shape curve with SRT in anaerobic digesters. However, for digested and dewatered biosolids, SRT ranging from 15 to 50 days in anaerobic digesters demonstrated insignificant effect on the odor emission from biosolids. In contrast, the peak odor emission was found to exponentially increase with both shear intensity and polymer dose applied during dewatering. The second part of this study investigated the impact of process intensification practices on sludge dewatering performance. The integration of high-rate activated sludge process and anaerobic digestion elevated the sludge orthophosphate level, leading to struvite scaling and dewaterability deterioration. Superior orthophosphate removal, significant improvement of sludge dewaterability, and favorable economics were achieved through sludge conditioning by cerium chloride. Continuous flow aerobic granulation technology offered significant process intensification of mainstream treatment trains. However, its impact on biosolids management was not studied. This study showed that there was little dewaterability difference between aerobic granular sludge and activated sludge when polymer was not added. However, about 75% polymer saving and improved dewatering performance were observed with polymer addition. When subjected to high shear, a greater dewaterability deterioration was observed for granular sludge than activated sludge. The last part of this study is focused on the impact of anaerobic digestion process intensification through thermal treatment including pre-pasteurization, thermophilic anaerobic digestion, temperature phased anaerobic digestion, and thermal hydrolysis pretreatment. Improved methane production, pathogen reduction, dewatering performance, and odor mitigation were observed with the involvement of these high-temperature processes. However, special cautions and measure should be taken during the start-up of these high rate processes as they are more liable to digester souring. In addition, the in-depth understanding of the mechanism of recalcitrant dissolved organic nitrogen formation during sludge thermal pretreatment was provided. / Doctor of Philosophy / This study is aimed to provide comprehensive evaluation and mechanistic understanding of the impact of process intensification techniques applied in main and side stream wastewater treatment on biosolids management in terms of anaerobic digestion enhancement, dewaterability improvement, odor mitigation, as well as phosphorus and nitrogen removal. The first part of this study was conducted to understand the effect of anaerobic digester solids retention time (SRT) on odor emission from biosolids. A kinetic model and inhibitory studies showed the emission of methanethiol (MT), a representative odor compound, was primarily determined by the dynamic concurrence of MT production from amino acid and utilization by methanogens in the course of anaerobic digestion. MT emission pattern follows a bell-shape curve with SRT in anaerobic digesters. However, for digested and dewatered biosolids, SRT ranging from 15 to 50 days in anaerobic digesters demonstrated insignificant effect on the odor emission from biosolids. In contrast, the peak odor emission was found to exponentially increase with both shear intensity and polymer dose applied during dewatering. The second part of this study investigated the impact of process intensification practices on sludge dewatering performance. The integration of high-rate activated sludge process and anaerobic digestion elevated the sludge orthophosphate level, leading to struvite scaling and dewaterability deterioration. Superior orthophosphate removal, significant improvement of sludge dewaterability, and favorable economics were achieved through sludge conditioning by cerium chloride. Continuous flow aerobic granulation technology offered significant process intensification of mainstream treatment trains. However, its impact on biosolids management was not studied. This study showed that there was little dewaterability difference between aerobic granular sludge and activated sludge when polymer was not added. However, about 75% polymer saving and improved dewatering performance were observed with polymer addition. When subjected to high shear, a greater dewaterability deterioration was observed for granular sludge than activated sludge. The last part of this study is focused on the impact of anaerobic digestion process intensification through thermal treatment including pre-pasteurization, thermophilic anaerobic digestion, temperature phased anaerobic digestion, and thermal hydrolysis pretreatment. Improved methane production, pathogen reduction, dewatering performance, and odor mitigation were observed with the involvement of these high-temperature processes. However, special cautions and measure should be taken during the start-up of these high rate processes as they are more liable to digester souring. In addition, the in-depth understanding of the mechanism of recalcitrant dissolved organic nitrogen formation during sludge thermal pretreatment was provided.

In order to study the performance and mechanisms of excess sludge reduction in the activated sludge that incorporates the Cannibal™ Process, laboratory activated sludge systems incorporating an anaerobic bioreactor into the sludge recycle stream were operated. In this study, the solids production in the Cannibal system was about 35-40% of the conventional system under steady state conditions. The reduction in waste sludge was optimized when the interchange rate, (the ratio of sludge fed from the activated sludge system to the bioreactor compared to the total mass in the activated sludge system) was set at about 10%. It was found that the release of protein from the anaerobic bioreactor was greater than that from the aerobic bioreactor. The SOUR data suggested that the released protein from the anaerobic bioreactor was easily degraded when the sludge was returned to the activated sludge system. It was also found that when the proportion of sludge added to the anaerobic bioreactor in batch tests was approximately 10%, the protein release was about 30 mg/L. When the proportion of sludge added was increased to 26 to 41%, the release was reduced to 10 and 6 mg/L, respectively. Within 30 hours, the protein release was complete. This suggests that there is an optimum or maximum amount of recycle or interchange (~10%) for the process to function best. / Master of Science

Le processus de dégradation anaérobie de la matière organique est un phénomène naturel largement répandu sur terre (ex. marais, lacs, rizières, systèmes digestifs d'animaux et humains). Une très grande diversité microbienne est entretenue durant ce processus, traduisant une diversité de voies métaboliques impliquées. Lorsqu'elle est complète, la digestion anaérobie aboutie à la formation de biogaz (mélange de méthane et de dioxyde de carbone). En termes de biotechnologie, le traitement par voie anaérobie de pollutions organiques permet de réduire le volume de déchets en générant du méthane valorisable sous plusieurs formes (électricité, chaleur, gaz naturel, biocarburant). Cependant, les digesteurs industriels sont optimisés pour un fonctionnement à 35°C ou à 55°C, ce qui nécessite un apport exogène d'énergie de maintenance. Ainsi, les travaux de thèse se sont intéressés à l'étude de la capacité d'adaptation de divers écosystèmes anaérobies industriels couvrant une variété de procédés et de conditions opératoires à convertir l'éthanol en biogaz à différentes températures. La première phase de l'étude avait pour but le conditionnement, en réacteurs de laboratoire d'écosystèmes à leur température d'origine avec un substrat facilement biodégradable (éthanol). Ensuite, les performances des communautés microbiennes (le potentiel méthanogène maximal et la cinétique de dégradation) ont été estimées sur un gradient de température de 5°C à 55°C en fioles. La phase de conditionnement des écosystèmes en réacteur batch a montré que la production de biogaz avoisinait la production théorique et que cette production s'accompagnait d'une diminution de la durée de réaction avec ajout successif du substrat. De plus, les cinétiques de production de biogaz obtenues les variaient fortement d'un écosystème à l'autre. Des profils d'empreintes moléculaires (CE-SSCP) des communautés bactériennes et archées ont été réalisés au début et à la fin du conditionnement. Ces profils de communauté ont été comparés entre eux par analyse en composante principale (ACP). Les populations bactériennes qui assuraient une performance efficiente étaient différentes de celles qui garantissaient une bonne capacité d'adaptation. Par ailleurs, le potentiel d'adaptation dépendait de la présence de populations d'Archaea méthanogènes bien spécifiques. En plaçant ensuite les écosystèmes conditionnés dans des conditions de température éloignées de la température d'origine, seuls les écosystèmes mésophiles se sont acclimatés aux températures psychrophiles. Comme attendu, l'activé spécifique maximale des méthanogènes était toujours obtenue à la température d'origine de l'écosystème. L'analyse des communautés bactériennes et archées à la fin de la période d'acclimatation a révélé que l'acclimatation des écosystèmes thermophiles et mésophiles à des températures plus faibles ne modifiait que légèrement la structure des communautés microbiennes. En revanche, des changements plus importants étaient obtenus lorsque la température d'incubation était augmentée par rapport à la température d'origine de l'écosystème. En résumé, l'étude de l'effet de la température d'incubation (de 5°C à 55°C) sur l'activité fermentaire et sur la structure des populations microbiennes est un bon modèle d'étude au laboratoire pour appréhender l'impact d'un facteur abiotique sur la dynamique structurelle et fonctionnelle d'une communauté microbienne complexe. / The process of anaerobic degradation of organic matter is a natural phenomenon widespread on Earth (eg, marshes, lakes, rice fields, digestive systems of animals and humans). A high microbial diversity is maintained during this process, reflecting a diversity of metabolic pathways involved. When complete, the anaerobic digestion accomplished in the formation of biogas (methane mixture and carbon dioxide). In terms of biotechnology, anaerobic treatment of organic pollution reduces the volume of waste and generates methane recoverable in several forms (electricity, heat, natural gas, biofuels). However, industrial digesters are optimized for operation at 35 ° C or 55 ° C, which requires exogenous energy maintenance. Thus, the thesis is interested in the study of the adaptability of various anaerobic ecosystems covering a variety of industrial processes and operating conditions to convert ethanol into biogas at different temperatures. The first phase of the study was to the conditioning, in laboratory reactors ecosystems to their original temperature with a readily biodegradable substrate (ethanol). Then, the performances of microbial communities (the maximum methanogenic potential and degradation kinetics) were estimated on a temperature gradient of 5 ° C to 55 ° C in glass bottles. The conditioning phase of the ecosystems in batch reactor showed that the biogas averaged theoretical production and this production was followed by a decrease in reaction time with successive addition of the substrate. In addition, the kinetics of the biogas obtained varied greatly from one ecosystem to another. Molecular fingerprinting profiles (CE-SSCP) of bacterial and archaeal communities were performed at the beginning and at the end of conditioning. These community profiles were compared with each other by principal component analysis (PCA). Bacterial populations that ensured efficient performance were different from those that ensured a good adaptability. In addition, the potential for adaptation depended on the presence of very specific methanogenic Archaea populations. When placing ecosystems conditioned in temperature away from the original temperature, only mesophilic ecosystems adapted to psychrophilic temperatures. As expected, specific methanogenic activity was always obtained at the original temperature of the ecosystem. Analysis of bacterial and archaeal communities at the end of the acclimation period revealed that acclimation thermophilic and mesophilic ecosystems to lower temperatures only modified slightly the structure of microbial communities. On the other hand, more significant changes were obtained when the incubation temperature was increased in comparison to the original temperature of the ecosystem. In summary, the study of the effect of incubation temperature (5 ° C to 55 ° C) on the fermentation activity and microbial population structure is a good model for laboratory study to understand the impact of abiotic factor on the structural and functional dynamics of a complex microbial community.

LD2668 .T4 1947 D68 / Master of Science

Cette étude porte sur l'évaluation de la performance d'un procédé biologique visant â réduire la concentration en sulfure d'hydrogène (H[indice inférieur2]S) présent dans le biogaz. De l'air est injecté dans la phase gazeuse d'un bioréacteur de digestion anaérobie (ratio volumique air/biogaz=1/20) de telle sorte à assurer à la surface du liquide, une zone en micro-aérobie.Cette recherche s'intéresse spécifiquement aux boues anaérobies psychrophiles (25[degrés celsius]), acclimatées à du lisier bovin ou porcin. Une première expérience vise à évaluer le potentiel de biotransformation des boues non alimentées en lisier et soumises à une charge connue en H[indice inférieur 2]S (entre 0,68 et 2,19 mg H[indice inférieur 2]S L[indice supérieur -1] boues h[indice supérieur -1]) injectée dans la phase liquide à la base du bioréacteur. Un taux maximal de biotransformation de 1,27 mg H[indice inférieur 2]S L[indice supérieur -1] boues h[indice supérieur -1] a été obtenu pour un taux de réduction du H[indice inférieur 2]S de 96,9%, une capacité 6,7 fois supérieure au taux maximal obtenu pour un bioréacteur alimenté avec du lisier bovin (0,19 mg H[indice inférieur 2]S L[indice supérieur -1] boues h[indice supérieur -1]). Une deuxième expérience consiste à évaluer l'impact d'un tel procédé sur le rendement en méthane et la stabilité d'un bioréacteur en opération. Deux bioréacteurs psychrophiles sont opérés en mode semi-batch et alimentés de manière identique avec du lisier bovin. Un seul des deux bioréacteurs est opéré en micro-aérobie. Ce bioréacteur a présenté des concentrations en H[indice inférieur 2]S indétectables (<50 ppm), sauf les journées où le ratio volumique air/biogaz était entre 0 et 0,056. Des concentrations variant entre 0 et 3500 ppm étaient mesurées dans l'effluent gazeux du bioréacteur sans injection d'air. Le bioréacteur en micro-aérobie a présenté un rendement spécifique en méthane 6,5% plus faible que le bioréacteur témoin, mais cet écart a diminué jusqu'à 0,87% pour les 4 derniers cycles de l'expérience durant lesquels le débit d'air a été réduit et maintenu à 4 ml/min.

Since 2000, there has been a marked decline in the number of harbour seals in some regions around Britain; one possible contributing cause is competition for prey with sympatric grey seals. To explore one important aspect of this interaction, in this thesis the diet of harbour seals is estimated using analysis of hard prey remains recovered from faeces and compared with equivalent results for grey seals. To estimate coefficients to account for partial and complete digestion of hard prey remains, 100 whole prey feeding trials were conducted with six harbour seals and 18 prey species. Differences were found among prey species and between harbour and grey seals highlighting the importance of applying predator- and prey-specific digestion correction factors when reconstructing diet. In a comprehensive exploration of the diet of harbour seals around Britain, sandeel and flatfish dominated in the North Sea and large gadoids dominated on the Scottish west coast with seasonal pulses of pelagic prey. Variation in diet was linked to regional and seasonal differences in prey distribution and abundance. Sex-specific variation in harbour seal diet was examined in four regions. The main difference detected was in The Wash, where female diet quality was significantly higher than males in winter, which appeared to be driven by greater consumption of pelagic prey by female seals associated with seasonal energetic requirements of their annual life cycle. Comparison of the diet of harbour and grey seals revealed regional differences in diet composition, diversity and quality between the two species. However, there was no consistent pattern in this variation in relation to regional variation in harbour and grey seals population trajectories and no clear evidence for interspecific competition for prey. Future work should focus on an integrated investigation of prey abundance and distribution, and seal diet and foraging behaviour/distribution.

La digestion anaérobie implique un écosystème complexe qui dégrade progressivement la matière organique est la transforme en dioxyde de carbone et en (bio)méthane. Ce biogaz est une source d'énergie renouvelable dont l'utilisation s'inscrit dans une optique de développement durable. Le potentiel biogaz reste néanmoins sous-exploité à cause d'un manque d'outils adaptés pour garantir la pérennité des installations et mieux maîtriser la qualité du biogaz. Nous proposons des stratégies pour mieux valoriser les résidus organiques liquides, à travers deux approches. L'une propose des méthodes pour identifier un risque de déstabilisation et prévenir un mauvais fonctionnement du procédé, l'autre repose sur la régulation de la qualité du biogaz. Ces méthodes nécessitent des modèles dynamiques pour décrire avec précision l'évolution des variables du système. Nous proposons une modélisation fine des transferts liquide-gaz, qui conduit à un modèle où le coefficient de transfert (kLa) dépend du débit total de biogaz.<br />Ce lien implique une relation linéaire entre la qualité du biogaz et la concentration en CO2 dissous, qui sert à améliorer les modèles existants. Un indice de risque de déstabilisation du procédé est construit à partir d'une analyse de stabilité d'un modèle simplifié. Cette procédure, appliquée à un procédé pilote, peut détecter une éventuelle déstabilisation du fermenteur, plus tôt que les indicateurs usuels (pH, acides gras volatils). Enfin, nous introduisons une nouvelle stratégie de contrôle de la qualité du biogaz basée sur la régulation de l'alcalinité dans le digesteur. Différentes lois de commande sont proposées et validées expérimentalement sur un réacteur pilote.

Diets were based on steam-flaked milo and contained chopped alfalfa hay in the control diet. At the 65% concentrate level, cottonseed hulls or chopped wheat straw replaced half the alfalfa hay. At the 90% concentrate level, roughage sources were chopped alfalfa hay, cottonseed hulls, or wheat straw. Six growing steers and three mature, rumen-cannulated steers per concentrate level were used in separate Latin square experiments. Total tract digestion coefficients, particulate passage rates, liquid turnover rates, and rumination time were measured in the intact steers. In situ digestion, rumen pH, and rumen dry matter distribution were evaluated in the cannulated steers. Competition between rates of passage and digestion were used to calculate apparent extent of ruminal digestion (AED). At the 65% concentrate level, total tract digestion coefficients for the wheat straw vs alfalfa hay diet were not different, apparently due to increased milo and alfalfa hay neutral detergent fiber (NDF) digestion in the wheat straw diet. Milo and alfalfa hay AED for NDF were higher (P<.10). Dietary AED for DM, NDF, and cell solubles were highest (P<.05) for the alfalfa hay diet. Differences between diets were minimal, indicating roughage source in 90% concentrate diets does not substantially influence milo digestion or passage as it does in 65% concentrate diets.