Dissertations / Theses: 'Anaerobic Digestor'

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Santiago, Aníbal da Fonseca. "Sistema condominial de coleta de esgoto e tratamento em decanto-digestor seguido de alagados construídos. Estudo de caso: município de Nova Redenção - BA." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-27022009-154750/.

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Este trabalho foi desenvolvido no município de Nova Redenção, localizado na região da Chapada Diamantina no estado da Bahia, nordeste brasileiro. Nesse município é grave o quadro de saneamento ambiental, assim como em outros do interior do Brasil. A falta de recursos financeiros e humanos é fator que dificulta a resolução desse problema. Acredita-se que estudos e aprimoramentos de tecnologias simplificadas de coleta e tratamento de esgoto doméstico que superem essas dificuldades estão em consonância com as peculiaridades dessas localidades e são, atualmente, tópicos importantes para pesquisa. Esta proposta teve como objetivo a concepção, instalação e avaliação de um sistema condominial de coleta de esgoto (SCE) em porção da zona urbana do município, onde moram, aproximadamente, 250 habitantes. Também se estudou a concepção, instalação e partida do sistema tratamento do esgoto - decanto-digestor seguido de alagados construídos de fluxo sub-superficial. Avaliou-se a aceitação do SCE pela comunidade e seu funcionamento. Caracterizaram-se os afluentes e efluentes das unidades do sistema de tratamento em termos de remoção da matéria orgânica (MO), sólidos (SST), nutrientes (N e P) e Escherichia coli. Realizou-se estudo da hidrodinâmica das unidades do sistema, com uso de traçador. Efetuou-se o balanço hídrico nos alagados. A rede condominial instalada mostrou-se, como em experiências de outros autores, satisfatória e adequada em sua aplicação em comunidades com características semelhantes à desse estudo. O aspecto da tecnologia do SCE mais estranhado pela comunidade foi o diâmetro utilizado para o esgotamento, devido, principalmente, ao receio que a tubulação entupisse. Não se registrou nenhuma queixa entre vizinhos quanto ao fato da rede passar dentro dos lotes. O sistema de tratamento estudado mostrou, depois de onze semanas de monitoramento, 85% de remoção de DQO e 86% de \'DBO IND.5\'; 90% de remoção de SST; a remoção de nitrogênio amoniacal, fósfoto total e solúvel foram de: 25%, 36% e 40%, respectivamente. A remoção de E. coli foi de 2,1 unidades logarítmicas. A areia utilizada, de granulometria muito fina, afetou sobremaneira a hidrodinâmica dos alagados construídos, fazendo com que houvesse uma lâmina sobre o material suporte. Isso diminuiu o tempo de detenção hidráulica dos alagados e pode ter ocasionado em menor eficiência do sistema.
This work was developed in the city of Nova Redenção, located in the region of the Chapada Diamantina in the state of Bahia, northeastern Brazil. In this city there are serious problems of environmental sanitation as well as in other within the country. Lack of financial and human resources is a factor that complicates the resolution of this problem. It is believed that studies and improvements in technologies for simplified collection and treatment of domestic sewage are in line with the peculiarities of these locations and are, today, important topics for research. This proposal was aimed at the design, installation and evaluation of a \'condominial\' sewerage (CS) in the village portion of the township, where live approximately 250 people. The objective of the study was also the design, installation and start of the sewage treatment system - septic tank followed by sub-superficial flow constructed wetlands. The acceptance of the CS by the community and its operation were evaluated. The treatment system was characterized in terms of removal of organic matter (OM), solids (TSS), nutrients (N and P) and Escherichia coli. The hydrodynamics of the system units was studied, using tracer. The water balance of constructed wetlands has been done. The \'condominial\' sewerage demonstrated, as well as in other experiences, good and proper application in communities with similar characteristics to this study. The community did not accept only the small diameter used, due mainly to their fear of clogging. Complaints from neighbors about the tubes passing through backyards were not registered. The treatment system study showed, after eleven weeks of monitoring, 85% of removal of COD and 86% of BOD5, 90% of removal of TSS, the removal of ammonia nitrogen, total and soluble fósfoto were: 25%, 36% and 40% respectively. The removal of E. coli was 2.1 logarithmic units. The sand used, of a very fine particle size, has particularly affected the hydrodynamics of the constructed wetlands, creating a sheet of water on the support material. It reduced the hydraulic detention time of the flooded water, which may be the cause of low efficiency.

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Castano, Juan Mauricio. "Anaerobic Digestion of Low Rate Digesters in Temperate Climates." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345220853.

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Moraes, Luciana de Mattos. "Avaliação da biodegradabilidade anaerobia de lodos de esgoto provenientes de reatores anaerobios sequenciais." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257154.

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Orientador: Durval Rodrigues de Paula Junior
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola
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Resumo: O potencial de aplicabilidade do processo anaeróbio pode ser avaliado a partir do conhecimento de poucas características dos resíduos a serem tratados. Uma avaliação preliminar dessas características pode auxiliar na escolha do sistema de tratamento mais adequado, permitindo, dessa forma, estimativas de produção de sólidos biológicos, de requisitos de nutrientes, de produção de metano, etc. A caracterização dos resíduos, por meio de testes de biodegradabilidade, é de fundamental importância, uma vez que os resíduos apresentam grande variabilidade quanto à qualidade, quantidade, Demanda Química de Oxigênio (DQO) e presença de compostos orgânicos refratários. Acrescentam-se ainda outras características importantes ao tratamento anaeróbio, notadamente pH, alcalinidade, nutrientes inorgânicos, temperatura e a eventual presença de compostos potencialmente tóxicos. Durante esse trabalho foi desenvolvida uma metodologia para avaliação da biodegradabilidade anaeróbia de lodos de esgoto estabilizados por reatores anaeróbios, utilizando testes simplificados de bancada, visando promover um maior conhecimento sobre a cinética de biodegradação dos lodos. De forma a agregar informações complementares sobre os lodos estudados realizou-se também a identificação morfológica dos diferentes grupos de microrganismos responsáveis pelo processo de digestão anaeróbia. A metodologia desenvolvida propõe a determinação da ¿biodegradabilidade anaeróbia intrínseca¿ dos lodos de esgoto por meio do monitoramento da produção e da composição do biogás (quanto às concentrações de CH4 e CO2). Os testes foram realizados em frascos de 280mL de volume preenchidos com 50% do seu volume com proporções de lodo e água de forma a garantir uma concentração de Sólidos Voláteis em torno de 10mg.L-1; os outros 50% constituíram o ¿headspace¿ que, após os frascos terem sido vedados, foi preenchido com N2. Os ensaios foram realizados em mesa agitadora (150rpm), sob temperatura controlada (35°C) e tiveram a duração de 15 dias, monitorando-se a cada 2 dias, a pressão interna do frasco e a composição do biogás. A avaliação da ¿biodegradabilidade anaeróbia intrínseca¿ das amostras de lodo foi quantificada por meio da determinação da taxa específica máxima de produção de CH4 (KCH4) e da taxa específica máxima de produção de CO2 (KCO2), as quais representam os ¿coeficientes de biodegradabilidade intrínseca¿ e foram obtidos por meio da aplicação de modelos matemáticos ajustados aos perfis de concentração molar de CH4 e CO2 em função do tempo. Os resultados obtidos nos testes de biodegradabilidade refletiram, de maneira geral, o comportamento dos reatores anaeróbios seqüenciais (Sistema B) operados em escala real com TDHs de 30, 20 e 10 dias, indicando que a metodologia desenvolvida permitiu a estimativa de ¿coeficientes de biodegradabilidade anaeróbia intrínseca¿ de lodos de esgoto por meio de testes simplificados de bancada com boa reprodutibilidade
Abstract: The potential of applicability of an anaerobic process can be evaluated from the knowledge of some characteristics of the residues to be treated. A preliminary evaluation of these characteristics can assist in the choice of a more suitable treatment system, what allows to estimate the production of biological solids, requirements for nutrients, methane production, etc. The characterization of the residues, through biodegradability tests, is of fundamental importance, once that the residues present a great variability for the quality, amount, Chemical Oxygen Demand (COD) and the presence of refractory organics. There are other important characteristics for the anaerobic treatment of sewage sludge, like pH, alkalinity, inorganic nutrients, temperature and the presence or not of very toxic compounds. During this work, a methodology for the evaluation of the anaerobic biodegradability of sewage sludge, stabilized by anaerobic reactors was developed using simplified bench tests, aiming to know more about the kinetics of biodegradation of sludge. With the intention to add complementary information about the studied sludge, it was also achieved the morphologic identification of the different groups of microorganisms that are responsible for the anaerobic digestion process. The developed methodology considers the determination of the ¿intrinsic anaerobic biodegradability¿ of sewage sludge through the monitoring of the production and of the composition of biogas (concentrations of CH4 and CO2). The tests had been carried out in bottles of 280mL filled with 50% of its volume with sludge and water ratios to guarantee a volatile solids concentration about 10mg.L-1; the other 50% constituted the ¿headspace¿ that, after the bottles had been hinted, were filled with N2. The assays had been carried through in a shaker (150rpm), under controlled temperature (35°C) and had the duration of 15 days, monitoring the pressure inside the flask and the composition of the biogas in every 2 days. The evaluation of the ¿intrinsic anaerobic biodegradability¿ of the sludge was quantified through the determination of the maximum specific tax of production of CH4 (KCH4) and of the maximum specific rate of CO2 production (KCO2), which represent the intrinsic biodegradability coefficients¿ and had been achieved through the application of mathematical models adjusted to the profiles of molar concentration of CH4 and CO2 in function of the time. The results obtained in the biodegradability tests had reflected, in a general way, the behavior of the sequential anaerobic reactors (System B) operated in real scale with HDTs (Hydraulic Detention Time) of 30, 20 and 10 days, indicating that the developed methodology allowed to estimate the ¿intrinsic biodegradability coefficients¿ of sewage sludge through simplified bench tests with good reproducibility
Doutorado
Agua e Solo
Doutor em Engenharia Agrícola

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Kidby, David W. "Biogas hydrogen as an indicator of digester instability in anaerobic sewage sludge digesters." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280473.

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Velho, Douglas Ferreira. "Digestão anaeróbia de resíduos de restaurantes: partida do reator e avaliação do biofertilizante." Universidade do Vale do Rio dos Sinos, 2016. http://www.repositorio.jesuita.org.br/handle/UNISINOS/5823.

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Comitesinos - Comitê de Gerenciamento da Bacia Hidrográfica do Rio dos Sinos
FUNDEPE - Fundação Universitária para Desenvolvimento do Ensino e da Pesquisa
Petrobras - Petróleo Brasileiro S. A.
UNISINOS - Universidade do Vale do Rio dos Sinos
O crescente aumento na geração de resíduos sólidos urbanos, somado às formas inadequadas de tratamento e disposição contribuem de forma direta e significativa com a problemática ambiental. Diante deste cenário, se faz necessário o desenvolvimento de alternativas que permitam outros benefícios além da disposição final apropriada. A digestão anaeróbia é uma alternativa viável e economicamente interessante para tratamento da fração orgânica dos resíduos sólidos urbanos. Considerando que em nosso país a fração orgânica é predominante nos resíduos sólidos urbanos, correspondendo em média a mais de 40% na composição, ao mesmo tempo que reduz o volume de resíduos enviados para os aterros sanitários, o processo gera produtos como o biogás e biofertilizante para uso agrícola. Esta pesquisa teve como objetivo avaliar a tratabilidade da fração orgânica dos resíduos sólidos domésticos provenientes do preparo e pós consumo das refeições de um restaurante universitário em um reator operado por batelada e qualificar as características do biofertilizante gerado. Para atingir este objetivo, a pesquisa foi realizada em três etapas, sendo que na etapa inicial foram realizadas quatro bateladas nas quais foram analisadas a proporção adequada de resíduos e inóculo para partida do reator sem que ocorresse acidificação. A segunda etapa consistiu na realização de seis bateladas, nas quais foram monitorados os principais parâmetros de operação e a terceira etapa onde foram avaliados os parâmetros químicos, físicos e microbiológicos do biofertilizante gerado ao final dos ensaios da segunda etapa. Os resultados da primeira etapa apontaram que a proporção de 6:1 em termos de sólidos totais voláteis, sendo lodo proveniente de um reator UASB e resíduos sólidos putrescíveis respectivamente, apresentaram uma partida adequada do sistema, sem que ocorresse acidificação, com o pH variando entre 6,9 e 7,7. Na segunda fase o monitoramento dos principais parâmetros de operação permitiu que no decorrer dos ensaios a proporção em termos de STV fosse reduzida, chegando a 1:1 de inóculo e substrato respectivamente, na batelada 10, portanto permitindo o tratamento de uma quantidade maior de resíduos em relação aos ensaios iniciais. Os resultados obtidos no monitoramento apontaram que o pH manteve-se dentro da faixa considerada ideal entre 6,0 e 8,0, porém o período de vinte e dois dias adotado como tempo de retenção mostrou-se insuficiente para degradação e consequente remoção da matéria orgânica, sendo que apenas a batelada 10 mostrou-se eficiente na remoção de STV 8,1% e carbono orgânico total 33,5%. A análise física do biofertilizante gerado no final de cada ensaio apontou umidade acima do permitido pela legislação, sendo indicado apenas para uso via aspersão. Quimicamente o biofertilizante apresentou insuficiência de nitrogênio, evidenciada nas elevadas relações C:N iniciais e finais obtidas e carência de macronutrientes como fósforo cujos resultados ficaram abaixo de 1%, mínimo imposto pela legislação e potássio, elemento que não foi detectado na pelo equipamento utilizado. A qualidade sanitária do composto atendeu a legislação quanto a presença de ovos viáveis de helmintos, sendo que todos os ensaios apresentaram resultados inferiores a uma unidade/4g, porém apresentou resultados acima do limite estabelecido para coliformes termotolerantes. O teste de germinação confirmou a ausência da fitotoxidade dos produtos.
The increase in the generation of municipal solid waste, together with the inadequate forms of treatment and disposal contribute directly and significantly to the environmental problems. In this scenario, it is necessary to develop alternatives to other benefits in addition to the appropriate disposal. Anaerobic digestion is a viable alternative and economically interesting for the treatment of the organic fraction of municipal solid waste. Whereas in our country the organic fraction is predominant in urban solid waste, corresponding to an average of over 40% in the composition, at the same time reducing the volume of waste sent to landfills, the process generates products such as biogas and biofertilizers for agricultural use. This research aimed to evaluate the treatability of the organic fraction of household waste from the preparation and after consumption of meals from a university restaurant in a reactor operated by batch and qualify the characteristics of the generated biofertilizers. To achieve this goal, the research was conducted in three phases, with the initial phase were held four batches were analyzed in which the proportions of the waste and inoculum for starting the reactor without acidification occurred. The second stage consisted of six batches, which were monitored in the main operating parameters and the third stage where we evaluated the chemical, physical and microbiological biofertilizer generated at the end of the second stage trials. The first step results indicated that the ratio of 6: 1 in terms of total volatile solids, and sludge from a UASB reactor and solid waste putrescible respectively, showed a suitable starting system without occur acidification to pH between 6.9 and 7.7. In the second stage, the monitoring of key operating parameters allowed during the experiment the proportion in terms STV be reduced, reaching 1: 1 inoculum and substrate respectively in the batch 10, thus allowing treatment of a larger quantity of waste compared to the initial test. The results showed that monitoring the pH was maintained within the range considered optimal between 6.0 and 8.0, but the period twenty-two days adopted as the retention time was insufficient to degradation and subsequent removal of matter organic, and only the batch 10 was effective in removing STV 8.1% and 33.5% total organic carbon. Physical analysis of biofertilizers generated at the end of each test pointed humidity above those permitted by law and is intended only for use via spraying. Chemically biofertilizer showed nitrogen deficiency, evidenced in the high ratios C: Initial N and obtained final and lack of nutrients such as phosphorus whose results were below 1% minimum required by the legislation and potassium, an element that was not detected in the equipment used. The sanitary quality of the compound met the legislation for the presence of viable helminth eggs, and all tests showed lower results to a unit / 4G, but showed results above the limit for fecal coliforms. The germination test confirmed the absence of phytotoxicity of products.

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Ledesma, Lina Marcela Sánchez. "Produção de estruvita a partir de esgoto doméstico." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3147/tde-14082015-144656/.

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A escassez das fontes de fósforo e o alto consumo de energia associado à produção de fertilizantes nitrogenados serão problemas que deverão ser enfrentados no futuro. A recuperação de nutrientes das águas residuárias na forma de estruvita tem sido considerada como uma alternativa para atenuar estes problemas. Na América Latina, a produção de estruvita a partir de esgoto ainda não é uma tecnologia bem conhecida e, portanto, a finalidade deste trabalho é contribuir com uma melhor compreensão dos fenômenos envolvidos. Para isso, a pesquisa foi dividida em três etapas: 1) produção de estruvita a partir de efluente de reator anaeróbio de fluxo ascendente com manto de lodo (RAFA); 2) produção de estruvita a partir de sobrenadante de digestor anaeróbio de lodo de um processo com remoção biológica de fósforo (DALRBF) e 3) influência do cálcio na estruvita produzida na etapa 2. Nas três etapas, ajustaram-se as concentrações de magnésio, a fim de obter razões fósforo:magnésio (P:Mg) pré-estabelecidas, e o pH entre 8,00 e 10,50. Os resultados da primeira etapa mostraram que não foi possível produzir estruvita no efluente do RAFA nas condições testadas. No entanto, foram observadas remoções de fósforo e de nitrogênio, devido à formação de fosfatos de cálcio e de magnésio amorfos. Os resultados da segunda etapa comprovaram a viabilidade de produção de estruvita de sobrenadante de DALRBF e mostraram que os consumos molares dos íons fosfato (PO43-), amônio (NH4+) e magnésio (Mg2+) ou as remoções destes (%) não devem ser os únicos parâmetros para avaliar a formação de estruvita, pois outros compostos cristalizam ou precipitam e reduzem a qualidade do mineral. Para um meio com condições semelhantes às testadas nesta etapa, uma razão P:Mg 1:2 e um pH igual a 9,50 asseguram a máxima recuperação de nutrientes como estruvita com concentração mínima de impurezas, facilitando seu posterior uso como fertilizante. Os resultados da terceira etapa mostraram que uma fase amorfa de fosfato de cálcio ou de magnésio se forma na superfície da estruvita.
The shortage of the phosphorus sources and high-energy consumption associated to the nitrogen fertilizers production will be problems in the future. The nutrient recovery from wastewater as struvite has been considered as an alternative to alleviate these problems. In Latin America, production of struvite from wastewater is not yet a wellknown technology and therefore the purpose of this work is to contribute to a better understanding of the phenomena involved. This research work was performed in three phases: 1) production of struvite from upflow anaerobic sludge blanket reactor effluent; 2) production of struvite from anaerobic digester supernatant of enhanced biological phosphorus removal process (ADS-EBPR) and 3) influence of calcium in the struvite produced in the phase 2. In three phases, the magnesium concentrations were adjusted to obtain the preset phosphorus:magnesium (P:Mg) ratios and the pH was adjusted between 8,00 and 10,50. The results of the first phase showed that it is not possible to produce struvite in the upflow anaerobic sludge blanket reactor effluent in the tested conditions. However, removal of nitrogen and phosphorus was observed because amorphous calcium and magnesium phosphates were produced. The results of the second phase showed that it is possible to produce struvite in the ADS-EBPR and the molar consumptions of phosphate (PO43-), ammonia (NH4+) and magnesium (Mg2+) or removals (%) should not be the only parameters to evaluate the struvite formation, because other compounds crystallize or precipitate and reduce the quality of the mineral. In the similar conditions tested in this phase, a P:Mg ratio 1:2 and pH 9,50 assure maximum nutrients recovery as struvite with minimum impurities concentration, facilitating its subsequent use as fertilizer. The results of the third phase showed that amorphous calcium or magnesium phosphates were produced on the struvite surface.

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Racz, Tiffany A. "Anaerobic Digestion of Wastewater-Grown Algae Biomass With Optimized Biogas Yields and Nutrient Solubilzation." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/2245.

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Whole-cell algae biomass grown on nutrient-rich wastewater can be anaerobically digested to produce renewable heat and power, and to solubilize nutrients to grow additional algae biomass in a biorefinery system. In this study, algae biomass was grown on clarified primary wastewater in 33-m2 ponds at a 4-day residence time with sedimentation harvesting of the biomass. Lab digesters were used to test biogas yields and nutrient solubilization from the anaerobic digestion of algal biomass with and without mixing and with sonication as a pretreatment. Additionally, algae were fed to unheated and unmixed 1135-L pilot digesters to determine the effects of seasonal temperatures and organic loading rates on biogas yields and nutrient solubilization. Finally a scalability experiment was conducted to determine how well lab digesters replicated the nutrient solubilization and biogas yields of pilot digesters when they were operated at the same average daily temperature, and organic load. Overall, the tested conditions included mixing, temperature, feed pretreatment by sonication, scale, and organic loading. It was determined that unmixed, 20˚C digesters fed an average variable organic loading of 0.12 g VS/L-day had the highest yield of 0.3 L CH4/g VS fed. Compared to similarly operated digesters (30˚C, constant organic load 0.25 g VS/L-day) sonicated feed increased the mass yield of methane by 18% (0.28 L CH4/g VSintroduced), and mixing increased the mass yield of methane by 4% (0.25 L CH4/g VS). For the same digesters, sonicated feed increased the average nitrogen and phosphorus solubilization 10% and 11% with 36% N and 28% particulate P remaining, respectively. Eliminating mixing increased the average nitrogen and phosphorus solubilization by 13% and 27%, with 40% and 31% remaining as particulates, respectively. The pilot digesters produced an overall average mass yield of 0.19 L CH4/g VS, with a summer average of 0.46 L CH4/g VS and a winter average of 0.15 L CH4/g VS. For the pilot digesters, the average amount of remaining particulate nitrogen and phosphorus was 36% and 39%, respectively, with an average of 57% volatile solids destruction. Finally for the scale experiment, the pilot digesters exhibited mass and volumetric yields of 47% and 28% (0.19 L CH4/g VS; 0.011 L CH4/L-d) greater than the lab digesters. Additionally, the pilot digesters had 2% greater nitrogen solubilization and 29% less phosphorus solubilization with 23% N and 15% P, than the lab digesters. Based on these results, for a low organic load (0.01 – 0.65 g VS/L-day), it is recommended that digesters be unmixed and heated which, and have a longer winter residence time. In addition to benefiting methane yield and nutrient solubilization, these digester operating conditions would allow increased supply of nutrients to ponds during the most productive months when nutrients are being consumed at faster rates in the algae ponds.

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Tang, Jing. "Comparison of Dairy Manure Anaerobic Digestion Performance in Gas-lift and Bubble Column Digesters." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/46319.

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Anaerobic digestion is one of the most promising management options for dairy manure treatment. Manure wastewater from dairy farms has been used for methane production for decades. However, performance failure due to inadequate mixing is routine. In general, the mixng of anaerobic digester is achived throguh mechnical stirring, liquid circulation, and gas circulation, among which the gas circulation proves to be the most effcient way. In this work, we studied the liquid flow pattern of two differetn type of gas-circualtion based anaerobic digesters, with the aim to understand the effects of hydrodynamic behavior of the digesting liquid on the anaerobic digestion performance, so a better mixing strategy can be provided. We used two 20-L gas circulation based anaerobic digesters with confined (gas-lift) and unconfined (bubble column) design. The anaerobic digestion performance and mixing behaviors were studied at different gas recirculation rate. It was found that the biogas production from the bubble column was constantly higher than that from gas-lift digester. However, the overall flow of the two digesters, which is indicated by residence time distribution (RTD), showed a similar pattern. Furhter investigation of local liquid flow behavior using Computational Fluid Dynamic (CFD) indicate that the bubble column accumulated higher portion of sludge in the bottom of the digester, which has a higher TS and VS, COD, and biomethane production potential than those from the gas-lift digester. This is the reason that the biogas production from the bubble column is higher than the gas-lift digester. Through this study, a thorough characterization of the flow behavior of the anaerobic digester were developed, and provided a deep insight of its influence on the anaerobic digestion performance.
Master of Science

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Ganidi, Nafsika. "Anaerobic digestion foaming causes." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3450.

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Anaerobic digestion foaming has been encountered in several sewage treatment plants in the UK. Foaming has raised major concerns for the water utilities due to significant impacts on process efficiency and operational costs. Several foaming causes have been suggested over the past few years by researchers. However, the supporting experimental information is limited and in some cases site specific. The present report aimed to provide a better understanding of the anaerobic digestion foaming problem and to identify the underlying mechanisms of foaming. Field and laboratory investigation identified organic loading as a cause of foaming. Bench scale batch digestion studies in sludge showed that the critical organic loading for foaming was at 2.5 kg VS.m -3 while the 5 kg VS.m -3 resulted in persistent foaming. Moreover, full scale foaming digesters exhibited higher foaming potential in digested sludge under aeration in the laboratory than the full scale non- foaming digesters indicating that the concentration of surface active agents was higher. Further investigation of the effect of the surface active compounds, BSA and n-valeric acid on foaming showed that both compounds induced persistent foaming at all the examined concentrations. Filamentous bacteria contribution to foam initiation and stabilization was considered insignificant, apart from one occasion (FI:5), due to the abundance of filaments in foaming sludge (FI≤3) and their partitioning in foam (FI≤3). Part of the current work also assessed the cost implications of a foaming incident at the full scale. The antifoam cost was found to be of major concern for the water utilities costing between £1.30 and £13.00 per 1000 m 3 of digester volume per day. However, there was no information on biogas and energy loss whereas the information provided on cleaning, maintenance costs and manpower working hours was poor. Thus, the overall cost of a foaming incident at the full scale could not be estimated at this stage.

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Christodoulides, Jacqueline S. "Mixing in anaerobic digesters." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533276.

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Peruzzo, Vanessa Verona. "Estudo da acidogênese e metanogênese aplicada no tratamento da vinhaça da cana-de-açúcar." reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/2900.

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A vinhaça, água residuária do processo, apresenta em sua composição DQO de 20 a 100 g DQO.L-1 e um ótimo potencial de produção de biogás por meio da digestão anaeróbia. Para avaliar a capacidade de produção de biogás, foram realizados experimentos sob o efeito gradual da carga orgânica volumétrica (COV) e da relação A/M, avaliando a etapa metanogênica. Como no processo de fabricação do etanol é adicionado ácido sulfúrico para evitar a contaminação bacteriana, foi avaliado a interferência da adição de diferentes concentrações de sulfetos no processo em valore de pH 7,0 e 7,5. O fermentador foi alimentado com Na2S.9H2O, variando a concentração do íon S2- de 0 a 1000 mg.L-1. Para obter uma boa eficiência na produção de metano, a etapa acidogênica também foi avaliada. Para isso, se manteve as mesmas concentrações de biomassa e substrato, porém, ajustando os valores de pH em 5,0, 5,5, 6,0 e 6,5. Na etapa metanogênica uma satisfatória redução da elevada carga orgânica presente na vinhaça foi alcançada, com eficiência de remoção entre 82,0% e 90,3% em processo mesofílico. Um ajuste polinomial foi realizado para avaliar a produção específica de metano, que variou de 379 mL CH4.h-1 a 872 mL CH4.h-1 e atividade metanogênica de 0,33 mmol CH4.gSVT-1 h-1 a 0,77 mmol CH4.gSVT-1 h-1. Para a etapa da sulfetogênese, o pH afetou consideravelmente o desempenho das arqueas metanogênicas, ocorrendo inibição mais acentuada para o pH 7,5. Na concentração mais baixa testada, de 50 mg S2-.L-1, foi observada inibição de 31,85% para pH 7,0 e de 67% para pH 7,5 e para a concentração mais elevada de 1000 mg S2-.L-1 a inibição foi de 59,75% e de 94,07% respectivamente. Na última etapa da acidogênese, maiores concentrações de ácido propiônico e acético foram alcançadas em pH 5,0 e 5,5, com 1374,66 e 1477,23 mg C3H6O2.L-1 e 993,05 e 767,80 mg CH3COOH.L-1. Maiores taxas de produção de AGV ocorreram em pH 6,5, alcançando para o ácido propiônico 8,82 mmol.d-1 gSVT-1 e 7,99 mmol.d-1 gSVT-1 para ácido acético. A produção acumulada de metano nas primeiras 60 horas atingiu 2210 mL, 5300 mL, 7210 mL e 7620 mL CH4, respectivamente para pH 5,0, 5,5, 6,0 e
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Centro de Pesquisa e Desenvolvimento Leopoldo Américo Miguêz de Mello, CENPES.
The vinasse, wastewater of the process, presents in its composition a COD of 20 to 100 g COD.L-1 and an excellent biogas production potential through anaerobic digestion. To evaluate the biogas production capacity, experiments were carried out under the gradual effect of organic volumetric load (OVL) and A/M ratio, evaluating the methanogenic step. Considering that sulfuric acid is added to the ethanol production process to prevent bacterial contamination, the interference of the addition of different sulfide concentrations in the process at pH 7.0 and 7.5 was evaluated. The fermenter was fed with Na2S.9H2O, varying the concentration of the S2- ion from 0 to 1000 mg.L-1. In order to obtain good efficiency in the production of methane, the acidogenic step was also evaluated. For this, the same concentrations of biomass and substrate were maintained, however, the pH to was adjusted 5.0, 5.5, 6.0 and 6.5. In the methanogenic stage a satisfactory reduction of the organic load present in the vinasse was achieved, with removal efficiency in the range of 82.0% and 90.3% for mesophilic process. A polynomial fit was performed to evaluate the specific production of methane, ranging from 379 mL CH4.h-1 to 872 mL CH4.h-1 and a methanogenic activity of 0.33 mmol CH4.gSVT-1 h-1 at 0.77 mmol CH4.g SVT-1 h-1. For the sulfetogenic stage, the pH considerably affected the performance of the methanogenic archaea, with a more pronounced inhibition at pH 7.5. The lowest concentration tested, 50 mg S2-.L-1, resulted in an inhibition of 31.85% inhibition pH 7.0 and 67% at pH 7.5. The highest concentration, 1000 mg S2-.L-1, the inhibition was 59.75% and 94.07% respectively. Higher concentrations of propionic and acetic acid were reached at pH 5.0 and 5.5, with 1374.66 and 1477.23 mg C3H6O2.L-1 and 993.05 and 767.80 mg CH3COOH.L-1. Higher rates of VFA production occurred at pH 6.5, yielding 8.82 mmol.d-1 gSVT-1 and 7.99 mmol.d-1 gSVT-1 for acetic acid for propionic acid. Cumulative methane production in the first 60 hours increased 2210 mL, 5300 mL, 7210 mL and 7620 mL CH4, respectively to pH 5.0, 5.5, 6.0 and 6.5.

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12

Lehtinen, Silja. "Building a Small Scale Anaerobic Digester in Quelimane." Thesis, KTH, Industriell ekologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214458.

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Anaerobic digestion is a process where biogas is generated from organic substance in the absence of oxygen. The most common application of the anaerobic digestion technology in developing countries is small-scale household digesters producing biogas for cooking purposes. These systems are usually fed with cattle dung or organic household waste. The typical small-scale digester models are fixed-dome digester, floating-drum digester and rubber-balloon digester. Biogas systems contribute to self-sustainability of energy production, improve waste management and mitigate deforestation and health problems caused by poor waste management and usage of traditional cooking fuels such as firewood and charcoal. Anaerobic digestion technology is still quite unknown in Mozambique. An initiative to implement this technology in the municipality of Quelimane located in Zambézia province in the central part of the country, was taken in 2015 and background studies were performed during spring 2015 and 2016. As a part of the study resulting in this report, performed in spring 2017, a small-scale biogas digester was installed in Quelimane city. The digester was fed with the initial input of cow manure in order to create population of anaerobic bacteria and in the future it’s planned to be fed with food waste. The purpose of the first installed digester is to serve for educational purposes and to produce cooking fuel for the few people working in the municipal location where the digester is installed. It’s estimated that the digester has a potential to produce daily 0.3 m3 of biogas from 2 kg of food waste which can be used for preparing lunch for the employees or for heating water. In the future, possible applications of anaerobic digestion technology in Quelimane are a municipal biogas plant, cooling systems for the fish industry and biogas based latrines in the less developed areas located outside of the city center.

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Bishop, Clark Paul. "The economics of anaerobic digestion." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Summer2007/c_bishop_072307.pdf.

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14

Aftab, Shahbaz. "Anaerobic digestion of food wastes." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283399.

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15

Dapelo, Davide. "Gas mixing in anaerobic digestion." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6879/.

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Mesophilic anaerobic digestion is one of the most used and successful technologies to treat the sludges resulting from wastewater treatment. However, traditional approaches to digester design are firmly rooted in empiricism and rule of thumb rather than science. Mixing is an energy-intensive operation, and therefore the need to lower the wastewater process carbon footprint requires searching how to lower the input mixing energy without compromising–and indeed enhancing–biogas production. In particular, the literature on gas mixing is still particularly poor. For the first time, an Euler-Lagrangian CFD model was developed for gas mixing in anaerobic digestion. The model was validated against laboratory experiments with PIV and PEPT techniques. Full-scale simulations reproducing a real digester were performed with the validated model, and different scenarios were reproduced. Shear rate distribution was used as a parameter to assess the most appropriate value of input mixing power. The simulations also low-viscosity flow patterns for the first time. This phenomenon is intrinsically linked to the non-Newtonian nature of sludge, and leads to short-circuited mixing. Switching biogas injection between two different nozzle series was found to be an effective strategy to mitigate the issue of the low-viscosity flow patterns. Final recommendations on input mixing power and switching time were given to improve mixing efficiency in the full-scale design taken into consideration. A journal paper published in Water Research and a conference paper presented at the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing (Civil-Comp) were produced. Two other papers are currently in preparation.

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Climenhaga, Martha Anne. "Anaerobic digestion of catering wastes." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/73611/.

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This research addresses gaps in current knowledge regarding process issues associated with long term semi-continuous digestion of food waste as a sole substrate, and the role of trace elements and biomass retention in digestion of food wastes. Source segregated food wastes were collected from a university catering facility and found, in characterisation studies, to have a total solids (TS) content of 28.1±0.25 %, a volatile solids (VS) content of 95.5±0.06% of TS and a chemical oxygen demand (COD) of 422±16 g kgwet weight -1. The total Kjeldahl nitrogen (TKN) and total lipid content were 22±1% and 3.8±0.24% of TS, respectively. The substrate was then processed during a number of digestion trials using mesophilic continuously-stirred tank reactors (CSTRs), to establish the suitability of this substrate for CSTR digestion. It was found that although good specific methane production of 0.36 l gVSadded -1 was obtained from the substrate, the process was unstable at a hydraulic retention time (HRT) of 25 days, with methanogenic failure occurring after 80 days or when the organic loading rate (OLR) was increased. Further digestion trials were initiated, therefore, to investigate the effects of trace element supplementation and extending HRT on process stability, areas for which there is little information in existing literature. Reactors with hydraulic retention times of 25, 30, 50, 100, and 180 days supplemented with a trace element solution showed stable digestion for longer periods than duplicate control digesters without supplementation. The time points of failure in the control digesters were shown to be related to washout time, as calculated using the HRT. Trace element supplementation allowed stable operation at an OLR up to 3.5 gVS l-1d-1, with specific methane production ranging from 0.41-0.47 l gVSadded -1 and VS destruction of 63-77%. Supplementation with trace elements did not, however, guarantee indefinite stable operation, as digesters at the shortest (25 days) and longest (180 days) retention time eventually showed methanogenic failure. A slow methanogenic biomass growth rate and accumulation of inhibitory substances, respectively, were hypothesised as possible reasons for these failures. Analysis of metal concentrations in the digestate showed that cobalt was the metal most likely to be responsible for the observed benefits of the mixed trace metal supplementation as the concentration of this increased in the supplemented digester whilst decreasing in its non-supplemented control. The relative importance of the liquid and solid fractions in maintaining stability were investigated in novel digestion trials in which solid and liquid retention times were uncoupled. Digesters with SRT of 25 days and HRT of over 150 days exhibited methanogenic failure after approximately 45 days. In contrast, reactors with SRT of over 150 days and HRT of 25 days maintained stable digestion, with specific methane production of 0.53 l gVSadded -1, and also showed recovery from a thermal shock applied during the experiment. Inhibitory compounds such as VFA were kept low by flushing through the system while alkalinity was regenerated by the action of biomass kept in the system. The retention of solids may also have facilitated the retention of trace metals.

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Roberts, Keiron. "Anaerobic digestion of marine microalgae." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388117/.

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Anaerobic digestion is a simple and energetically efficient way in comparison to some other biofuel methods of producing renewable energy from a range of biomass types. Although digestion of micro-algal biomass was first suggested in the 1950s, only a few studies have been conducted for assessment of its performance. This work assessed the potential for energy recovery from microalgae via anaerobic digestion for both freshwater and marine species. This research screened seven laboratory-grown marine and freshwater microalgal species (Nannochloropsis. oculata, Thalassiosira . pseudonana, Dunaliella. salina, Rhododomas sp, Isochrysis. galbana, Chlorella. vulgaris and Scenedesmus sp) and two samples from large-scale cultivation systems for their suitability as a substrate for anaerobic digestion. Biochemical methane production and a theoretical maximum growth yield of each species were employed to offer a means of comparing methane productivity per unit of cultivation under standard conditions. The data generated were useful in determining suitable species to culture and digest under continuous operation. A review of the literature highlighted a gap in the knowledge for the continuous digestion of different marine micro-algal species, as well as the potential inhibitory effect of high salinities on the anaerobic digestion process to non-acclimatised systems run under continuous operation. Addition of total salt ≥ 10g L-1 caused reactor failure, supporting the findings of the literature review. It was possible, however, to gradually adapt the inoculum to marine concentrations of chloride salts (31.1 g L-1) with <7% difference in specific methane production of controls. Addition of sulphate showed competition between methanogens and sulphate-reducing bacteria with further minor losses in methane yield. There was up to 60% reduction in SMP for the highest sulphate loaded reactors, however, the population successfully adapted to sulphate concentrations above those typically found in seawater and showed gaseous H2S productivity in proportion to the applied sulphate load. This suggests that the effects of marine concentrations of chloride and sulphate salts can be overcome by a gradual acclimatisation. The selected algal species I. galbana and D. salina were continuously cultivated in a photobioreactor under low and high sulphate media and continuously digested using the salt adapted inoculum. The specific methane production for I. galbana and D. salina was 0.19 and 0.23 L CH4 g-1 VS, with a VS destruction of 32% and 50% respectively. Addition of a high SO4 grown D. salina as a feed resulted in a reduction of SMP to 0.19 L CH4 g-1 VS with an increase in H2S production. Loses in total solids and sulphur were observed under continuous study due to oxidation of H2S and struvite precipitation within the reactors, which was not observed under batch analysis. This highlights the importance in conducting continuous studies over batch, as these effects can be overlooked.

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Ghoor, Tasneem. "Developments in anaerobic digestion modelling." Doctoral thesis, Faculty of Engineering and the Built Environment, 2019. https://hdl.handle.net/11427/31718.

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Anaerobic digestion (AD) is notorious for being susceptible to failure and is regarded as unstable and sensitive. Thus, to avoid failure, anaerobic digesters are frequently operated far below their optimal level. In order to run a digester closer to capacity, a better understanding of AD failure is required. Under conditions approaching failure, or during startup, intermediate products such as acetate, propionate and hydrogen accumulate. Successful AD modelling during failure requires the AD model to be suitably calibrated. Some AD models have been calibrated to the initial slow rate-limiting hydrolysis step only with the result that these models cannot be used to predict AD failure. Without adequate modelling of AD dynamics, the AD model cannot be used to model digester start-up, digester failure or even upflow anaerobic sludge bed (UASB) reactors (which have temporary failure conditions at the bottom of the bed). This study aims to develop an AD model capable of predicting failure and digester start-up conditions. Development of an improved model was accomplished by means of calibrating the AD model to a UASB reactor dataset wherein temporary failure conditions are present in the bottom of the reactor, evident by the presence of the abovementioned intermediate products. After comparing and contrasting available AD models to identify one for further development, the AD model subset (PWM_SA_AD) of plantwide model South Africa (PWM_SA) was selected because (1) it characterizes the organics’ composition using routine wastewater treatment measurements rather than carbohydrates, lipids and proteins, which is typical of other models, (2) external speciation reduces model stiffness, (3) includes aqueous, gas and solid phases for pH calculation, gas evolution and mineral precipitation and (4) contains the same components as PWM_SA enabling plant-wide modelling without needing component transformers between process units. Before calibration, PMW_SA_AD was rigorously tested for mass balance, stoichiometric and kinetic correctness. Because the UASB reactor undergoes temporary failure observed by the accumulation of AD intermediate substrates in the bottom of the bed, the glucose fed UASB reactor system of Sam-Soon et al. (1989) was modelled to calibrate the Monod kinetic constants of the acidogens, acetoclastic methanogens, acetogens and hydrogenotrophic methanogens. This required coding into WEST® (MikebyDHI, 2016), the platform on which PWM_SA runs, a six-in-series completely-mixed AD system with a solids retention factor for each digester that retained a fraction of the reactor’s solids. Determination of the parameters that required calibration was identified with sensitivity analysis. Due to the complexity of the physical, biological and aqueous interactions, many model simulations were needed to identify the important parameters with the lasso (least absolute shrinkage and selection operator) feature selection method. Not unexpectedly the most important parameters that required calibration were the retention factor for each digester in the series; and the maximum specific growth rates and the half-saturation coefficients for the four AD biomass groups, which were global parameters, i.e. for each biomass group the same values in each digester of the series applies. Stability of the complex six-in-series UASB reactor needed the initial masses in each digester to be reasonably close to the final steady-state masses. Steady-state Microsoft Excel AD spreadsheet models were set-up to calculate these initial masses. Following the calibration procedure wherein the modelled AD intermediate products matched the measurements from the UASB reactor dataset, it was expected that the pH also would be predicted well. However, this was not the case. So, the assumption of equilibrium between the headspace CO2 partial pressure and aqueous phase CO2 concentration was replaced by a rate-controlled CO2 evolution. With this correction, the predicted pH matched well with that observed along the height of the UASB reactor. The calibrated model was then tested to observe how the UASB reactor system fails irrecoverably by gradually decreasing the influent alkalinity from the dataset value of 6000 mg/L as CaCO3. Irrecoverable failure occurred at an influent alkalinity of 4200mg/L as CaCO3 because the specific growth rate of the acetoclastic methanogens, which progressively decreases the further the pH falls below 7, fell below the minimum required to utilise the high acetate concentration. The role of the sensitivity of the acetogens to hydrogen in digester failure was also tested. Counter-intuitively, it was found that this in and of itself did not cause failure but that to a degree, postponed failure because the acetogen inactivity at high hydrogen concentration delayed the acetate load on the acetoclastic methanogens. To verify the acetogen effect on failure, acetogen sensitivity to hydrogen was increased, and the alkalinity was gradually decreased. Irrecoverable failure now occurred at an influent alkalinity of 4000mg/L as CaCO3. The above modes of UASB reactor failure predicted by PWM_SA_AD were compared with ADM1 (Anaerobic Digestion Model No. 1). ADM1 was coded into PWM_SA_AD as an independent subset using the same external speciation routine. Although ADM1 has previously been documented to be incapable of predicting AD failure, this comparison showed that ADM1 predicted the same failure modes as PWM_SA_AD but at a higher influent alkalinity of 5000mg/L as CaCO3. One of the main reasons why ADM1 fails at sooner is that the specific growth rate of the acetoclastic methanogens in ADM1 is slower than in the PWM_SA_AD model calibrated to the UASB reactor data. The UASB reactor system calibrated PWM_SA_AD model was applied to model digester start-up with primary sewage sludge. This was done by adding to the single completelymixed anaerobic digester a percentage of seed and filling the rest of the volume with wastewater treatment plant effluent with 250 mg/L as CaCO3 alkalinity. The percentage of seed was the percentage of the anaerobic digester volume, which was filled with seed sludge containing the same biomass concentrations as those at steady state after start-up is complete and the set digester sludge age is reached. The hydrolysis rate of biodegradable particulate organics (BPO) was modelled with saturation kinetics (also known as Contois (1959) kinetics) with constants obtained from Sötemann et al. (2005b). Three different startup cases were investigated (1) setting the influent pump at the final steady-state flow rate but switching it off and on with either a pH controller or a Ripley ratio controller, (2) increasing the influent flow by a fixed proportion of the final steady-state flow daily (t1/t -1), where t is the start-up duration, (3) same as (2) but adding either a pH controller or a Ripley ratio controller. Two modes failure, resulting in an inability to start up, were found: (1) BPO overload which causes acetoclastic methanogen overload and surprisingly (2) acetoclastic methanogen starvation. BPO overload results in a high acetate concentration and low pH, which slow the acetoclastic methanogens below the tipping point to start up. It is exacerbated by low percentage of seed and during the slow hydrolysis and acidification of BPO, or a setpoint which is not sufficiently conservative. Acetoclastic methanogen starvation is as a result of a too conservative setpoint which prevents flow from entering the digester, thereby depriving the organisms of the substrate. Plotting the specific growth rate to the maximum specific growth rate ratio of the acetoclastic methanogens indicated that under starvation conditions, the ratio is extremely low. The reason for the low ratio is due to the low bulk liquid concentrations on which Monod kinetics depends. The limitations of Monod kinetics are made apparent here because the initial seed amount is significantly below the final steadystate mass. So, for these cases, further investigations are required to identify if saturation kinetics will allow better predictions. Through the development of the model, although the model was capable of predicting failure and start-up in line with the expected principles, it is not possible to find a unique set of kinetic constants, resulting in a degree of freedom with the choice of a maximum specific growth rate of acidogens. This degree of freedom may have been eliminated if sufficient measurements were available. Overall, the investigation provided useful insight into the mode of AD failure and difficulties regarding modelling digester start-up. There is, therefore, the scope for further additions to the study, with a specific focus on the residual COD, sludge bed measurements, gas flow and hydrogen concentration in the bed and modelling the acidogen, acetogen, acetoclastic methanogen and hydrogenotrophic methanogen specific growth rates with saturation kinetics. This will enable greater insight into the failure modes and the effect of hydrogen and growth rate kinetics on the AD system failure.

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Arthur-Mensah, Kojo. "Anaerobic digestion of detergent wastewaters." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288882.

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20

Montelius, Josefine. "Förbehandling av skogsindustriellt slam för ett ökat metanutbyte vid rötning : En kombination av termisk och kemisk förbehandling." Thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-31178.

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Vid tillverkning av massa och papper förorenas årligen 505 miljoner kubikmeter vatten som måste renas innan det släpps tillbaka till omgivningen. Vid reningen avskiljs först stora partiklar som sedan avvattnas och förbränns. Vattnet som blir kvar genomgår ytterligare en rening, varvid det bildas bioslam. Bioslammet innehåller mycket intracellulärt vatten, vilket gör det kostsamt och energikrävande att avvattna. Det är även sedan 2005 förbjudet att dumpa organiskt material, varför en mer ekonomiskt attraktiv behandling av slammet är anaerob nedbrytning. I denna nedbrytning omvandlas det organiska materialet till metan och koldioxid där metanet är den eftertraktade gasen. Bioslammet innehåller dock partiklar såsom träfiberrester och mikroorganismer med komplex struktur och är näringsfattigt. Någon form av sönderdelande förbehandling underlättar därför rötningsprocessen. I detta projekt undersöktes termisk förbehandling i kombination med kemisk förbehandling på bioslam från Stora Enso Skoghalls bruk på Hammarö. Själva rötningen skedde i två omgångar varav den första omgången med termisk förbehandling vid 70C och den andra vid 140C. Den kemiska förbehandlingen skedde med tillsats av lut (natriumhydroxid), kalk (kalciumhydroxid) och syra (fosforsyra) vid pH 9 och 11 för baserna och pH 2 och 4 för syran. Även neutrala prov (endast värmebehandling) och ett blankprov (ingen förbehandling) gjordes. Bioslammet ympades med kommunalt slam från Fiskartorpets reningsverk i Kristinehamn som har en mesofil bakteriekultur. Rötningen varade i 19 dagar per omgång i en temperatur på 35C och skedde satsvis i E-kolvar försedda med påsar för gasuppsamling. Totalt rötades 42 prov per omgång som utgjordes av sju mätpunkter á sex replikat för goda statistiska underlag. Resultaten gav en indikation för högst metanproduktion för proven behandlade med kalk vid 140C och för provet utan kemisk förbehandling vid 140C. Lägst produktion hade det kalkbehandlade provet vid pH 9 och 70C följt av blankprovet. Lutproven gav lägre metanproduktion vid 140C än vid 70C och fosforsyran hade så gott som oförändrad produktion mellan temperaturerna. Gemensamt för alla prover som behandlats vid 70C var att de fick en högre procentandel metan då de behandlats vid 140C. De resultat som erhållits är dock osäkra då det i vissa fall var stor spridning mellan provens biogasproduktion inom de enskilda förbehandlingsområdena.
In the pulp and paper process 505 million tons of water are polluted annually, which has to be purified before it is returned to the surrounding lakes. When the water is treated bigger particles are first separated to form sludge, then dewatered and finally incinerated. The excess water is further treated were a type of sludge  bio sludge  is formed. The bio sludge contains high concentration of intracellular water, why it is expensive and energy demanding to dewater. It is also forbidden to dump organic waste since 2005, why a more economically attractive treatment of the water is anaerobic digestion. In the digestion organic compounds is converted into methane and carbon dioxide where the methane is the desired gas. The bio sludge also contains fiber residues and microorganisms with complex structure and is nutrient-poor, which makes it hard to digest. Some kind of disintegrating pretreatment is needed and co-digestion with a more nutrient-rich sludge to facilitate the digestion process. In this project thermal pretreatment in combination with chemical pretreatment was examined on bio sludge from Stora Enso Skoghalls bruk at Hammarö. The anaerobe digestion was done by two rounds whereof the first round thermal pretreated at 70C and the second at 140C. The chemical pretreatment was done by additive of sodium hydroxide, calcium hydroxide and phosphoric acid at pH 9 and 11 for the bases and pH 2 and 4 for the acid. Also neutral samples (no chemical pretreatment) and a reference sample (no pretreatment) were done. The bio sludge were co-digested with municipal sludge from Fiskartorpets reningsverk in Kristinehamn which has a mesophilic bacterial culture. The anaerobic digestion lasted for 19 days per round at a temperature of 35C and were done batch wise in E-flasks provided with a small bag for gas collection. Totally 42 samples were made per round which consisted of seven measurement points and six replicates each for a good statistical basis. The results gave an indication of the highest methane production for the samples treated with calcium hydroxide at 140C and the neutral sample treated at 140C. The sample treated with calcium hydroxide at pH 9 and 70C gave the lowest production of methane followed by the reference sample. The samples treated with sodium hydroxide gave a lower methane production at 140C than at 70C while the acid treated samples had almost the same production at the two different temperatures. All the samples had in common a higher proportion of methane in the biogas when treated at 140C than at 70C. The results should be taken with caution since the distribution amongst the samples within the same pretreatment method sometimes is very high.

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Torres, i. Castillo Ricard. "Estudi de la digestió anaeròbica en una i dues fases dels residus ramaders: estudi en planta pilot d'un sistema en dues fases." Doctoral thesis, Universitat de Barcelona, 1992. http://hdl.handle.net/10803/666135.

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Donat el problema que representa l'abocament dels residus agrícoles i ramaders, es proposa la digestió anaeròbica del jaç per a solucionar-lo. S'ha dissenyat els dispositius experimentals necessaris per a l'estudi en una fase amb recirculació de lixiviat, en dues fases en semicontinu, hidrolitzadors, i planta pilot per a la digestió del jaç boví. Amb això, s'ha experimentat diferents temperatures d'operació, diferents concentracions inicials de substrat, diferents TRH, i diferents continguts d'humitat en els sistemes. Així, s'ha trobat que el procés en dues fases proporciona una velocitat de digestió superior al procés en una fase. A tot això s'ha provat diferents models cinètics a nivell global. D'aquests el que millor descriu el sistema experimental és el model de Chen i Hashimoto. També hem provat un model cinètic en dues fases que proporciona un ajust millor al de qualsevol model global assajat. Finalment s'ha realitzat un estudi del valor agronòmic del residu produït en la digestió, obtenint-se uns resultats òptims.

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Tanneru, Charan Tej. "Anaerobic and Combined Anaerobic/Aerobic Digestion of Thermally Hydrolyzed Sludge." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/45880.

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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

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23

Andlay, Gunjan. "Commercialization of Anaerobic Contact Process for Anaerobic Digestion of Algae." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270240284.

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24

Fagbohungbe, Michael. "Optimisation of small scale anaerobic digestion technology : anaerobic digestion process regimes for energy recovery from waste." Thesis, Lancaster University, 2015. http://eprints.lancs.ac.uk/79342/.

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The recent advances in anaerobic digestion (AD) technology and changes in government policies have contributed to the gradual increase in the establishment of on-site small-scale anaerobic digesters in developed regions, particularly in Europe. However, these advances have not completely eradicated some of the challenges with operating AD system. The project is aimed at investigating the potential of optimizing small-scale AD through high solid digestion (HSAD) and reduction of substrate induced inhibition (SII). The study of different inocula, changes to environmental conditions, adsorption of inhibitors and reactor modification was explored. To investigate these possibilities, an onsite mono-substrate such as citrus fruit waste (CFW) with an average dry matter of 16% was used as the substrate, biochar material (rice husk, coconut shell and wood biochar) were used as adsorbent while an operating temperature from 35 - 55 ⁰C were also investigated. Limonene is an inhibitory compound and a constituent of CFW, this was used as the inhibitor, a compartmentalized anaerobic reactor (CAR) was designed to improve HSAD while selected inocula from digested sewage sludge, compost and landfill leachate and their mixture were used as an inoculant. In the first study, the acclimation rate of different inocula to increasing concentration of limonene compound was investigated and the mixed inocula recorded the highest recovery rate and methane yield with a value of 544 ± 21 ml CH4. The mixed inocula benefited from the synergistic effect of using a broader microbial community to mitigate limonene inhibition. This was followed up with the biochar study on AD of CFW and the result showed that microbial lag phase reduced by 50% which was attributed to sorption of limonene compound and biofilm formation on the biochar material. The study on AD of CFW at a different operating temperature of 35-55 ⁰C showed that the higher temperature of 45 and 55 ⁰C IV outperformed the other incubation with no detectable microbial lag phase. Finally, the optimization option for HSAD was investigated using a CAR and compared against the conventional continuous stirred tank reactor and a 34%, 43.3%, 48.5% and 79.9% higher cumulative methane production for organic loading rates of 1.42, 2.85, 4.00 and 5.00 gVSL-1 day -1, respectively was achieved. This performance was attributed to the lower compartment of the CAR which facilitated leachate treatment and distribution. The result showed that limonene a constituent of CFW and an example of SII can be counteracted by (i) inoculating with a mixture of inocula (ii) addition of biochar (iii) operation at high temperature of 45 and 55 ⁰C and (iv) the single stage compartmentalized reactor improved HSAD and reduced limonene suppression.

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25

Nogueira, Ricardo Galbiatti Sandoval. "Enteric and feces methane emissions, fermentative ruminal parameters and feeding behavior of cattle fed cottonseed and vitamin E." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/10/10135/tde-02052017-125157/.

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Problems about greenhouse gas emissions attributed to cattle production and improvements in the productivity of these animals has been growing and becoming increasingly important. Cattle releases methane as part of their digestive process, and this represents loss of energy for the animal. The decomposition of feces releases methane and it can be recovered by digester and transformed into different types of energy. Thus, aiming to quantify the potential production of enteric methane and anaerobic fecal decomposition, as well as to evaluate ruminal and behavioral parameters of cattle fed with cottonseed and vitamin E. Six cannulated cows (864±16 kg) were distributed in a replicate 3x3 Latin square. Treatments were: 1) control diet; 2) CS: basal diet plus 30% cottonseed and 3) CSVitE: basal diet plus 30% of cottonseed plus 500 UI of vitamin E. Results were compared through orthogonal contrast and values were considered significant when P0,05. No differences were observed for dry matter intake (DMI), as well as digestibility of DM and neutral detergent fiber (NDF). Animals supplemented with cottonseed spent more time eating and ruminating and less time in idles. Reduction in the concentration and production of acetate, butyrate and the acetate: propionate ratio was observed in animals fed cottonseed compared to the control. Enteric methane mitigation was observed for the cottonseed treatments compared to the control. Changes in the substrates characteristics used to load the digesters were observed. However, no differences were verified for the total biogas production, methane yield and capacity to recover the energy of the feces in the form of methane. Inclusion of 30% cottonseed can be used as a strategy to mitigate enteric methane, without causing losses in the DMI, nutrients digestibility and anaerobic digestion of feces. In addition, it promoted favorable changes in the ingestive behavior, ruminal fermentation products, as well as in the energy partition of the gastrointestinal tract. Vitamin E when is used as antioxidant had not effect on ruminal fermentation, feeding behavior and feces anaerobic digestion, thus the inclusion is not advised due absence of positive results.
A problemática das emissões de gases de efeito estufa atribuída à produção de bovinos e melhorias na produtividade desses animais vem crescendo e se tornando cada vez mais importante. Bovinos emitem metano como parte do seu processo digestivo, e isto representa perda de energia para o animal. A decomposição das fezes gera metano, este pode ser recuperado por biodigestores e transformado em diferentes tipos de energia. Assim, objetivou-se quantificar o potencial de produção do metano entérico e da decomposição anaeróbia das fezes, bem como avaliar parâmetros ruminais e comportamentais de bovinos alimentados com caroço de algodão e vitamina E. Foram utilizadas seis vacas fistuladas não gestantes e não lactantes (876 kg±16). Os tratamentos foram: 1) Controle: dieta basal; 2) CA: dieta basal mais 30% de caroço de algodão; 3) CAVitE: dieta basal mais 30% de caroço de algodão mais 500 UI vitamina E. O delineamento experimental utilizado foi o quadrado latino. Os resultados foram comparados por contrastes ortogonais e foram considerados significantes valores de P0,05. Não foram verificadas diferenças para o consumo de matéria seca (MS), bem como digestibilidade da MS e da fibra em detergente neutro (FDN). Os animais suplementados com caroço de algodão passaram maior tempo comendo e ruminando e menor tempo em ócio. Houve redução na concentração e produção de acetato, butirato e da relação acetato:propionato dos animais que receberam caroço de algodão comparado ao controle. A inclusão do caroço de algodão provocou mitigação das emissões de metano entérico. Houve alteração nas características dos substratos utilizados para abastecer os biodigestores. No entanto, não foram verificadas diferenças para a produção total de biogás, rendimento de metano e capacidade dos biodigestores em recuperar a energia das fezes na forma de metano. A inclusão de 30% caroço de algodão pode ser utilizada como estratégia para mitigar metano entérico, sem causar perdas no consumo, digestibilidade dos alimentos e na biodigestão anaeróbia das fezes. Além disso, sua inclusão promoveu alterações favoráveis no comportamento ingestivo, nos produtos da fermentação ruminal, bem como na partição de energia do trato gastrointestinal. A vitamina E quando utilizada como antioxidante não possui efeitos sobre a fermentação ruminal, comportamento ingestivo e biodigestão anaeróbia das fezes, assim sua inclusão não é indicada devido a ausência de resultados favoráveis a sua utilização.

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26

Ortega, Charleston Luis S. "Hyperthermophilic anaerobic digestion of food waste." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19271.

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The anaerobic digestion (AD) of the organic fraction (OFMSW) of municipal solid waste (MSW) is a sustainable and environmentally interesting solution as compared to landfilling. Anaerobic digestion operated under mesophilic temperatures degrades only a fraction of the complex compounds found in OFMSW, whereas under higher temperatures, such as thermophilic and hyperthermophilic, the degradation could be more extensive. The objective of this study was therefore to evaluate the effect of a thermal transition from 35°C (mesophilic) to 70°C (hyperthermophilic), on an anaerobic inoculum fed OFMSW. The research methodology was divided into the following stages: 1) a mesophilic, industrial wastewater treating granular sludge was upgraded to thermophilic conditions and adapted for the treatment of OFMSW (Chapter Three); 2) during the thermal transition from mesophilic to thermophilic conditions, a microbial phylogenetic characterization (16sDNA PCR followed by DGGE) of the sludge was carried out (Chapter Four); 3) to evaluate substrate (protein and vegetable oil) limiting degradation rates for the production of methane, a serum bottle batch test (MP) was developed (Chapter Five); and 4) the thermophilically adapted and OFMSW treating sludge was upgraded to hyperthermophilic conditions and both reactor performance and sludge methane and substrate activities were evaluated (Chapter Six). The one-step temperature upgrading from 35 to 55 ?C and the feeding of OFMSW resulted in a fully adapted inoculum without an initial time-consuming temperature acclimatization stage. The substrate loading rate program was a key factor in increase the population of thermophilic methanogens. Genomic deoxyribonucleic acid (16S rDNA) tools were used to cha
Le procédé de digestion anaérobie, visant à traiter la fraction organique des déchets solides, a l'avantage d'être plus intéressant que le procédé d'enfouissement des déchets en termes d'impact sur l'environnement. Le procédé de digestion anaérobie opère à des températures mésophiles et permet la dégradation partielle des composés complexes. A des températures plus élevées, telles thermophiles et hyper thermophiles, la dégradation de ces composés est plus efficace. Par conséquent, l'objectif fut d'évaluer l'effet d'une transition de température de 35°C (mésophile) à 70°C (hyper-thermophile) sur les microorganismes anaérobiques et leur dégradation des déchets alimentaire. La méthodologie a été divisée en plusieurs étapes, soit: 1) une boue de traitement d'effluents industriels du type granulaire mésophile a été soumise à des température thermophiles et à un traitement visant à l'adapter au traitement des déchets alimentaires (Chapitre 3); 2) les populations microbiennes présentes pendant la phase de transition de température mésophile à thermophile ont été caractérisées par un outil moléculaire (PCR et DGGE-ADNr16S) (Chapitre 4); 3) un test en batch a été développé afin d'étudier les vitesses limitantes de dégradation des substrats (protéines et huile végétale) (Chapitre 5); 4) la boue préalablement adaptée aux températures thermophiles et au traitement des déchets a été soumise à des températures hyper-thermophiles. La performance du réacteur et les activités de production de méthane et de dégradation du substrat ont alors été évaluées (Chapitre 6). L'étape d'adaptation a consisté à augmenter la température d'un seul coup, de 35 à 55°C, afin d'adapter le

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27

Lafitte-Trouque, Sandrine. "Enhanced anaerobic digestion of sewage sludge." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369392.

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Peck, M. W. "Anaerobic digestion of separated cattle slurry." Thesis, University of South Wales, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373421.

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29

Yirong, Chaowana. "Thermophilic anaerobic digestion of food waste." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/366736/.

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There is a requirement in the European Union to divert organic wastes from landfill because of the risk of methane emissions. One alternative is anaerobic digestion of organic wastes, such as food waste, to stabilise them whilst at the same time recovering the energy from them. One problem with this approach is that the high nitrogen content of food waste may lead to ammonia inhibition. A solution to this has been found for mesophilic digestion but had not been attempted in thermophilic digestion where ammonia toxicity is known to be more acute. The work was carried out in laboratory-scale semi-continuous digesters operated over long time periods to provide maximum opportunity for acclimatisation, and in duplicate to give an indication of reproducibility. A series of experimental runs were undertaken at thermophilic temperatures to assess the influence of trace element (TE) addition on the digestion process. These were carried out at organic loading rates (OLR) of 2, 3 and 4 g volatile solids (VS) l-1 day-1 against unsupplemented controls at OLR 2 g VS l-1 day-1. Although TE addition could offset the accumulation of VFA which occurred in response to an increasing concentration of total ammonical nitrogen (TAN), it could not prevent this. The high alkalinity resulting from ammonia, however, allowed the digesters to continue to produce methane until VFA had accumulated to high concentrations before eventual failure due to a rapid drop in pH. To determine the threshold inhibitory ammonia concentration in thermophilic digestion, one pair of digesters was run on synthetic low nitrogen food waste (low-N food waste) at an OLR 2 g VS l-1 day-1 and compared to a control pair running on domestic food waste at the same loading. All four digesters received TE supplementation. The digesters fed with low-N food waste showed consistently stable performance with pH ~7.4, IA/PA ratio ~0.4-0.5, SMP 0.39 l CH4 g-1 VS, 52-55% CH4, total VFA <500 mg l-1 and 88% VS destruction whereas the controls showed signs of failure after 112 days and irreversible VFA accumulation at a TAN concentration >3.5 g N l-1. One of the low N digesters was supplemented with urea slowly and one by a shock dose: both showed signs of VFA accumulation at TAN >2.5 gl-1 and, again, an irreversible trend in propionic acid build-up when TAN >4 g N l-1. Long term operation showed meta-stable conditions when the digesters were operated at TAN between 2.5 - 3.5g l-1 with oscillations in VFA (especially propionic acid) concentration. Mesophilic digestion at 37oC with TE addition showed very stable performance with pH ~8, IA/PA ≤ 0.3, SMP ~0.48 l CH4 g-1 VS, 55-60% CH4, total VFA < 300 mg l-1 and VS destruction ~75-78% with a final total ammonia nitrogen (TAN) concentration of 4.5 g N l-1. As the temperature in digesters was raised from 35 to 43 oC in 1oC steps a change in performance was noted when the temperature reached 40 oC. Above this temperature VFA concentrations rose above 4000 mg l-1 and biogas and methane production fluctuated. It is probable that the higher temperature increased the concentration of free ammonia nitrogen (FAN) to ~800 g N l-1 at the measured TAN concentration ~5.5-6.0 g N l-1 and this was sufficient be inhibitory even with TE dosing. Fluorescent in situ hybridisation (FISH) was used to identify the methanogenic populations in some of the trials over selected time periods. This showed changes in population structure both in relation to temperature (mesophilic or thermophilic) and also in response to increasing concentrations of TAN. At high TAN concentrations Methanomicrobiales was the dominant methanogenic group and under mesophilic conditions this proved to be extremely ammonia tolerant. A 14C radio-labelling assay confirmed the dominant pathway to methane formation was by the hydrogenotrophic route which reflected the known metabolic pathway of this methanogen. It was concluded that thermophilic digestion of source segregated domestic food waste would lead to instability and failure of the process unless measures were introduced to reduce the TAN concentration to < 3.5 g N l-1, and preferably to < 2.5 g N l-1. Keywords: Anaerobic digestion, food waste, biogas, VFA accumulation, ammonia inhibition, Fluorescent in situ Hybridisation (FISH).

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Verma, Nitin. "Anaerobic Digestion: Factors Effecting Odor Generation." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/43768.

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Land application of anaerobically stabilized biosolids is a beneficial method of handling the solid residuals from a wastewater treatment plant. One of the main issues that restrict land application of biosolids is nuisance odors associated with biosolids. Despite its importance, few studies have been done to enhance our knowledge of odor causing processes. This study was conducted to evaluate the effects of some factors that have been thought to be linked to odor generation from biosolids. The first part of this study has looked at the role of metals, iron and aluminum in particular, in determining the odor causing processes. The results showed that iron correlated well with headspace organic sulfur odor. In general, as the iron content of sludge increased greater amounts of odorous sulfur gases were produced from dewatered biosolids cakes. Aluminum did not show any relationship with organic sulfur odors. Parameters commonly used for assessing the performance of anaerobic digesters (volatile solids reduction (VSR), residual biological activity (RBA) and effluent volatile fatty acid (VFA) content) also showed no correlation with odors. The second part of the study focused on determining the impact of anaerobic digester solids retention time (SRT) on the odor generation from dewatered biosolids cakes and also on elucidating the nature and impact of the various Extracellular Polymeric Substances (EPS) fractions on odors. The results showed that odors decreased with an increase in the anaerobic digester SRT. VSR and RBA correlated with odors; however, as only one type of sludge was assessed, the conclusions about any relationship may not be universal. The results also showed that sulfur gas generation was a function of EPS material bound to iron, again showing that iron plays an important role in odor generation from dewatered sludge cakes. The third part of the study looked at the effects of advanced digestion processes on odor generation. Digested sludge from acid/gas and temperature phased anaerobic digestion systems were analyzed in the lab. The results show that both acid/gas system and temperature phased digestion had a positive impact on odor generation from dewatered biosolids cake. Comparison of sludge from pancake shaped and egg shaped digesters showed that egg shaped digester was more efficient with regard to odor reduction.
Master of Science

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31

Frear, Craig. "Anaerobic digestion strategies for dairy manures." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Summer2009/c_frear_061509.pdf.

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Thesis (Ph. D.)--Washington State University, August 2009.
Title from PDF title page (viewed on July 31, 2009). "Department of Biological Systems Engineering." Includes bibliographical references.

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Stephenson, Robert John. "A comparison of retained biomass anaerobic digester designs." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26740.

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The principles behind anaerobic digestion are fairly well understood, but the limits of application of each digester design are not known. Because there are significant differences in the properties of the many wastewaters requiring treatment optimal anaerobic digester performance requires the matching of feed characteristics to a digester design and mode of operation. No consensus has yet emerged on digester design, operating conditions or feed/digester match-ups. In this study, three bench scale retained biomass anaerobic digester designs were examined for their response to a sequence of varied hydraulic retention times (HRTs) and influent wastewater concentrations. The digester designs studied were the upflow anaerobic filter, the upflow anaerobic expanded bed and the upflow anaerobic sludge bed. The wastewater was screened and diluted dairy cow manure obtained from the UBC dairy barn. The parameters monitored included the total and soluble chemical oxygen demand (TCOD and SCOD), volatile and suspended solids (VS and SS), total volatile fatty acids (VFAs), total Kjeldahl and ammonia nitrogen (TKN and NH₃-N), pH, biogas production, and the methane (CH₄) and carbon dioxide (C0₂) content of the biogas. Wastewater treatment efficiencies, measured in terms of TCOD, SCOD, VS, and TVFA removals, and methane productivity and methane yield for each of the digester designs were examined for the range of the operating conditions. The anaerobic filter digester effected a mean TCOD removal efficiency of 47% ± 14% at a mean 4.0 day HRT, 51% ± 9% at a mean 2.3 day HRT and 35% ± 11% at a mean 1.3 day HRT. The expanded bed digester effected a mean TCOD removal of 45% ± 15% at a mean 4.3 day HRT, 38% ± 12% at a mean 2.5 day HRT and 28% ± 9% at a mean 1.3 day HRT. The sludge bed digester effected a mean TCOD removal of 53% ± 9% at a mean 3.8 day HRT, 45% ± 12% at a mean 2.2 day HRT and 32% ± 10% at a mean 1.2 day HRT. For all three digesters, the difference in the treatment efficiency over the range of HRTs tested, from 5 to 1.25 days was not in proportion to the change in HRT. Methane productivity, measured against either the removal or addition of substrate in terms of TCOD, SCOD, VS and TVFA, demonstrated considerable variability. Methane production increased with both substrate addition and substrate removal. Methane yield increased with increasing HRT. The sludge bed digester generally exhibited the greatest but most variable methane yields. It produced 0.095 L CH₄/g VS added at a mean 3.8 day HRT and 0.037 L CH₄/g VS added at a mean 1.2 day HRT. The anaerobic filter delivered the greatest methane yield at the intermediate HRT, 0.044 L CH₄/g VS added at a mean 2.3 day HRT. The expanded bed demonstrated low methane yields over the range of feed strengths and HRTs tested. Biogas composition averaged 62.1% methane and 17.1% carbon dioxide for the anaerobic filter, 43.6% methane and 5.3% carbon dioxide for the expanded bed. and 61.1% methane and 18.9% carbon dioxide for the sludge bed.
Applied Science, Faculty of
Graduate

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33

Campbell, Alison June. "The behaviour of pharmaceuticals in anaerobic digester sludge." Thesis, University of Portsmouth, 2013. https://researchportal.port.ac.uk/portal/en/theses/the-behaviour-of-pharmaceuticals-in-anaerobic-digester-sludge(995bec06-33fd-4c74-96a3-db4aba5a1c30).html.

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Pharmaceuticals are biologically active compounds that may be consumed in hundreds of tonnes per year, and which are excreted into municipal sewerage systems. Many pharmaceuticals persist during sewage treatment, and significant environmental risk has been linked to incomplete removal of pharmaceuticals. Evaluation of this risk is important and should be as representative as possible, taking into consideration all significant exposure routes and removal processes. Sludge treatment processes are of particular interest because they offer a final opportunity for the removal of persistent compounds before the disposal of treated biosolids. During environmental risk assessment, it is currently assumed that anaerobic sludge treatment results in insignificant removal of persistent and adsorptive compounds from sewage sludge. This project was undertaken to address whether this assumption is valid. This thesis describes research into the behaviour and fate of pharmaceuticals in anaerobic digester sludge, and examines how redox conditions influence removal efficiency. Nine commonly used pharmaceuticals (caffeine, cimetidine, fluoxetine, ibuprofen, metformin, naproxen, paroxetine, propranolol and salicylic acid) were selected for use based upon detection levels within sewage sludge and predicted anaerobic biodegradability. Initial experiments were conducted to identify toxicity to anaerobic microorganisms and anaerobic biodegradability. No toxicity to the microorganisms in anaerobic sludge was identified at ≤ 50 mg C L-1for any of the selected pharmaceuticals. The extent of removal in anaerobic sludge and the principal removal mechanism was found to vary between the selected pharmaceuticals. Metformin and salicylic acid were removed by 82 and 93% through mineralisation, respectively; naproxen was completely removed through primary biodegradation; fluoxetine, paroxetine and propranolol were removed by 92 and 96 and 55% due to adsorption, respectively. It was hypothesised that the removal of pharmaceuticals in anaerobic sludge through biodegradation and adsorption would be observed at varying rates under differing redox conditions. Test systems using headspace gas flushing and chemical amendment were evaluated for the control of redox conditions, with Eh measurements and DOC removal being used to indicate the stability of the system and its capacity for biodegradation. The addition of nitrate, sulfate and carbonate resulted in poised Eh values in the region of +200, -200 and -200 mV, respectively and 81, 78 and 74% removal of DOC, respectively. This methodology was subsequently used to evaluate the removal of naproxen, propranolol and fluoxetine under carbonate-, nitrate- and sulfate-amended conditions. Significant differences (p = 0.001) in the removal of naproxen through primary biodegradation were found to exist between different redox conditions. Naproxen was completely removed under control conditions, while 26, 98 and 61% removal was observed under nitrate- sulfate- and carbonate amended conditions, respectively. Some differences were observed in Kd values, however, redox amendment was found to have little influence upon the elimination of propranolol and fluoxetine through adsorption. It was identified from this work that pharmaceuticals within the aqueous phase degraded under anaerobic conditions as predicted, while pharmaceuticals associated with the biosolids were removed through adsorption and present a potential threat to the environment on the disposal of treated biosolids. This work supports the current industry assumption that anaerobic treatment of biosolids offers limited opportunity for the removal of adsorptive pharmaceuticals, and also found no evidence for their enhanced removal under redox-controlled conditions. While research described within this thesis increases knowledge of the behaviour of pharmaceuticals in sewage sludge under anaerobic conditions, data is presented for a limited range of test substances only, and further investigation into the behaviour of additional compound classes is recommended.

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Holloway, Ryan W. "Forward osmosis for concentration of anaerobic digester centrate." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1436020.

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35

Bouaziz, Alexandre N. (Alexandre Nathanel). "Design of an anaerobic digester in Quebec, Canada." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90008.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 81-84).
.In response to the future Quebec, Canada regulations prohibiting landfilling of organic matter by 2020, EBI, a waste management company located near Montreal is considering constructing an anaerobic digester. This thesis focuses on designing a scalable prototype based on the waste types available from the existing facilities of the company and the Montreal area. Based on an extended literature review and a feedstock analysis realized for this project, the study covers the elements composing an anaerobic digestion facility, the design criteria and calculations as well as a preliminary cost assessment and scalability strategy to help EBI realize the project.
by Alexandre N. Bouaziz.
M. Eng.

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Jeyanayagam, Samuel S. "Engineering analysis of a Chinese-type anaerobic digester." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49800.

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Davis, Owen S. "Heat transfer through anaerobic digester concrete tank walls." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29909.

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This dissertation is a study of the heat transfer through concrete walls in anaerobic digester facilities. In the biogas industry, the term “heat loss” is synonymous with heat transfer. The dissertation identifies the reasons why heat is critical in the operations of these facilities. Concrete has traditionally been a material used for the retention of liquid-based products and additionally provides good thermal insulating properties. It combines the benefits of being relatively cost effective for the construction of large tanks and requiring low maintenance during the operational life span. The research focuses on the thermal properties of the various constituents of concrete and the influence these have on the overall thermal properties of the concrete tank. The constituents forming part of the study are cement, corex slag, water, fine and coarse aggregate. The study showed that the aggregates have a greater influence on the thermal conductivity than the other constituents. It also showed that the mineral composition of the aggregates has a greater effect on the thermal conductivity than the porosity of the aggregates. The study also looked at the influence of the interfacial transition zone around the aggregate and this was found to be not significant and generally can be ignored as a contributor to the thermal conductivity of normal / structural concrete. The effects of the porosity of the binder paste does affect the thermal conductivity specifically when aqueous solutions are being retained. The capillary pores of the paste can be filled with liquid (mainly water) and less with air. Due to water having a higher thermal conductivity than air, the thermal conductivity of the binder paste is significantly increased. The effects of reinforcement on the thermal conductivity of concrete was also investigated. Different types and arrangements of reinforcement could have a big influence. Steel fibres and reinforcement if aligned in the direction of the thermal gradient will greatly increase the thermal conductivity. However, it was found that the reinforcement used in the sample wall did not increase the thermal conductivity significantly as it was mainly aligned perpendicularly to the direction of the thermal gradient. Similarly, no steel fibres were used in the concrete. Once the thermal conductivities of the constituent materials were determined, the effective thermal conductivity of the concrete could be calculated using the effective medium theory. The subsequent heat losses, which are a function of the thermal conductivity, the temperature gradient between the internal and external faces of the concrete wall, the contact surface area and the heat transfer coefficient, could be calculated as a function of time. The New Horizons Waste to Energy Project in Cape Town was used as a reference project and the research was based on the materials used in the construction of the concrete anaerobic tanks. The project was also used for the measurement of the temperature gradients and subsequent calculation of actual heat losses at various points along the concrete walls. Furthermore, a computational model was developed using Abaqus to compare the results with those derived from the theoretical model. The heat loss from the computational model compares very well with that of the theoretical model.

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Conklin, Anne. "Acetoclastic methanogenesis : a key to anaerobic digester stability /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10131.

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39

Machado, Francisca LÃvia de Oliveira. "Co-anaerobic digestion of microalgae and glycerol from biodiesel residual." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8714.

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CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior
Microalgae, microscopic life forms with photosynthetic capacity, produce oxygen thanks to light energy. Due to this capacity, microalgae are used for sewage treatment in stabilization ponds, however, this activity generates a large amount of microalgal biomass. In view of this excess of biomass production and its disposal in water bodies produces unpleasant effects, it has been evaluated the re-use of this biomass as a substrate for methane production in anaerobic digestion. Since microalgae have a rigid cell wall, the application of microalgae hydrolysis tests was necessary in order to improve its biodegradability. Heat pretreatment for 30 minutes at 120ÂC and 1 kgf/cm2 resulted in the best pretreatment applied. In order to improve C/N ratio, residual glycerol coming from biodiesel production was used to perform co-digestion with microalgae. Residual glycerol coming from biodiesel production (1Kg of glycerol per 10 Kg of biodiesel generated) is an impure residue which is also produced at large scale as a byproduct from the trans-esterification of fats and oils. In fact, the presence of impurities limits its applications. In this study, different COD/N ratios of 20 (phase 2), 40 (phase 3) and 70 (phase 4) were tested and the organic loading rate (OLR) applied ranged from 0,06 to 0,75 kg/m3.d. In the phase 1 only microalgae was used on the influent. Two modified UASB reactors were used. One of them was fed with pretreated microalgae, while the other one was fed with non-pretreated microalgae. Both of them were operated in co-digestion with glycerol. COD removal efficiencies ranged between 40% and 90%. Biogas produced presented values of 73% and 84% for each bioreactor treating pretreated and non-pretreated microalgae, respectively. Neither nitrogen nor ammonia and total and volatile suspended solids was significantly removed. Moreover, microalgae were the sole source of macro and micro-nutrients in this work. Sodium bicarbonate was used as a buffer during the phase 4, since pH fall down enough to harm the anaerobic digestion process at the beginning of phase 4. Based on the maintenance of adequate VFA/Alk ratios, both reactors presented a stable operation, specially the reactors treating pre-treated microalgae. Instability periods were mainly observed in some operation phases in the reactor without pretreatment. Specific methanogenic activity tests were carried out in order to evaluate the quality of the inoculum in terms of activity and methane production. Methane production presented a mean value of 0,26 g DQO-CH4/g SSV.d.
As microalgas, seres microscÃpicos com capacidade fotossintÃtica, produzem oxigÃnio na presenÃa de energia luminosa. Devido a isso as microalgas sÃo utilizadas para tratamento de esgotos em lagoas de estabilizaÃÃo, porÃm essa atividade gera uma grande quantidade de biomassa algal. Tendo em vista a produÃÃo dessa biomassa e sua destinaÃÃo em corpos hÃdricos provocando efeitos desagradÃveis, buscou-se avaliar a reutilizaÃÃo dessa biomassa como substrato para produÃÃo de metano a partir da digestÃo anaerÃbia. Devido Ã presenÃa de uma parede celular rÃgida, verificou-se a necessidade da aplicaÃÃo de testes de hidrÃlise para as microalgas com a finalidade de melhorar sua biodegradabilidade, sendo observado o melhor prÃ-tratamento aplicado, o tÃrmico por 30 minutos a 120ÂC e 1 kgf/cm2. Para melhorar a relaÃÃo C/N, utilizou-se o glicerol residual do biodiesel para realizaÃÃo de co-digestÃo com microalgas. O glicerol residual do biodiesel (1 kg de glicerol para cada 10 kg de biodiesel produzido), alÃm de ser um resÃduo impuro, Ã tambÃm produzido em grande escala como subproduto da transesterificaÃÃo de Ãleos e gorduras e sem muitas aplicaÃÃes devido exatamente a presenÃa de impurezas. Foram testadas relaÃÃes DQO/N de 20 (fase 2), 40 (fase 3) e 70 (fase 4), alÃm da relaÃÃo apenas das microalgas (fase 1), sendo as COV aplicadas, variando de 0,06 a 0,75 kg/m3.d. Foram utilizados dois reatores semelhantes ao UASB (UASB modificado), nos quais continham microalgas brutas e prÃ-tratadas, ambos em co-digestÃo com o glicerol. As remoÃÃes de DQO variaram de 40 a 90%. O biogÃs produzido teve rendimentos de atÃ 73% para o reator degradando microalgas prÃ-tratadas e 84% para o reator degradando microalgas brutas. NÃo houve remoÃÃes significativas de amÃnia e sÃlidos suspensos totais e volÃteis, tambÃm nÃo foram utilizados macro e micronutrientes, sendo esses nutrientes fornecidos apenas pelas microalgas. O bicarbonato de sÃdio como tampÃo foi utilizado apenas na Ãltima fase (fase 4), devido a queda do pH para uma faixa nÃo aceitÃvel para digestÃo anaerÃbia, no inÃcio dessa fase. As condiÃÃes de estabilidade foram mantidas, baseadas na relaÃÃo AGV/Alc, que se manteve em faixas aceitÃveis, principalmente para o reator operando microalgas prÃ-tratadas, sendo observado valores indicativos de instabilidade em algumas fases no reator sem prÃ-tratamento. Foi realizado teste de atividade metanogÃnica especÃfica para avaliar o lodo de inÃculo quanto a atividade e produÃÃo de metano, obtendo-se valor mÃdio de 0,26 g DQO-CH4/g SSV.d.

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40

Alsaigh, Ahmad. "Anaerobic digestion of fatty slaughterhouse waste optimising the digestion process." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21377/.

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The continued growth of world population and food production leads to a continued increase in organic waste, responsible for many environmental and health problems when disposed in the wrong way. In Makkah city, huge amount of raw slaughterhouse waste from the Hajj sacrifice is generated and disposed in landfill without any treatment each year during Hajj. The huge number of pilgrims and a slaughterhouse waste generated from sacrificed animal (2.5 million animals in 2014) results in an environmental and health problems from the landfill area. One of the most applicable and effective methods to treat organic waste materials is anaerobic digestion (AD). In AD, bioactivity of four different groups of microorganisms in sequential metabolic steps under oxygen free conditions is responsible for breaking down complex organic waste into the simplest compounds and producing energy in form of biogas (a mixture of methane and carbon dioxide). However, the process can collapse when the organic waste contains high fatty materials (such as slaughterhouse waste) as long chain fatty acids (LCFAs) produce a strong inhibitory effect on some AD microorganisms. In a batch system, adding a small amount of fat to a large volume of anaerobic seeding sludge in order to provide sufficient amount of anaerobic inoculum could work effectively. However, this will lead to the disadvantage of wasting most of the reactor volume and therefore reducing the capacity to receive fresh organic waste. This research looks into the possibility of optimising the digestion process in order to achieve a good anaerobic digestion process for high fat concentration substrate with a minimum amount of seeding sludge in the reactor. Different strategies were studied to achieve this goal. These included the use of different fat concentrations in co-digestion with vegetable waste, different I/S (inoculum to substrate) ratios vs/vs, different operating conditions of single stage reactors (mesophilic CSTR, thermophilic CSTR, and mesophilic up-flow), and study of different multi stage reactor sets (two, three, and four stages) in order to optimise the digestion process.

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41

Monson, Kevin D. "The effect of various control actions on anaerobic digester performance." Thesis, University of South Wales, 2004. https://pure.southwales.ac.uk/en/studentthesis/the-effect-of-various-control-actions-on-anaerobic-digester-performance(fe5cc949-4123-4827-a530-8f0a7ec5848e).html.

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The sugar industry processes sugar cane and sugar beet to manufacture edible sugar. A high rate anaerobic system followed by an activated sludge process to 'polish' the effluent is presently the best available technology not entailing excessive costs for the treatment of wastewater from sugar processing factories. Upflow anaerobic sludge blanket (UASB) reactor systems are the most commonly implemented, with the higher loaded expanded granular sludge bed (EGSB) type systems gradually replacing at least some of the UASB applications. This higher loading carries with it a greater risk of process instability, especially given the irregular quantity and composition of sugar processing wastes. Control actions are required for process efficiency, preferably with appropriate control parameters monitored on-line. The need to balance economics (with regards to quantities of chemicals dosed) with the safety/stability of the process further exacerbates the need for close control. There are a limited number of control actions available e.g. bicarbonate alkalinity (BA) dosing, temporary diversion of load by feed rate variation, or dilution with final effluent. Monitoring of conventional anaerobic digester systems typically consists of a combination of intermittent manual sampling followed by off-line analysis coupled with qualitative observations. Hence a decline in reactor performance could go unnoticed for a significant period of time. A simple yet reliable control system could not only minimise labour, but could also react to any changes in reactor conditions as soon as they occurred, leading to more efficient process operation, higher quality treatment and ultimately greater economic gain. The industrially recognised 'bottleneck' in the quest for automatic control is the availability of reliable and cheap on-line analysers. In the work presented here a series of experiments have been carried out on a simulated sugar processing wastewater using an on-line BA monitor in conjunction with an adaptive control strategy developed in a parallel PhD project. The possibility of achieving successful automatic control of an EGSB reactor through its start up phase and also during steady state operation (including some degree of process optimisation) and a series of organic step-change experiments was investigated. Two different control actions to maintain a BA set-point in the reactor, organic loading rate (OLR) variation and BA dosing, were compared. Research was carried out on a 30 1 EGSB reactor rig operating at 37 °C, fitted with on-line sensors to measure temperature, gas production, carbon dioxide percentage and pH. All sensors were interfaced with a PC configured to scan the sensors at one minute intervals. Five attempts to automatically start-up the EGSB reactor were made (Experiments 1-5), using OLR variation as a control action at a constant hydraulic retention time (HRT) of 23.3 hours, with various improvements and adjustments made to the reactor and control system after each. It was concluded that it was not possible to automatically control start-up to steady state using OLR as a control action using the BA monitor and controller in their present forms. Main reasons for this were the susceptibility of the laboratory-scale BA monitor to blockage by biomass washed out of the reactor (a common occurrence during the start-up phase) and the severity of loading rate oscillations. For Experiment 6 BA was dosed according to the relationship of the on-line BA monitor output to the BA setpoint, and OLR was changed approximately weekly according to operator expertise based on on- and off-line data and visual observations. HRT was maintained at 22 hours. A successful, sustainable startup was achieved, with mean % COD removal during the first 10 weeks being 78 % at a mean OLR of 9 kgCOD/m3 /day. After the successful start-up period, the reactor's HRT was approximately halved to 11.2 hours, and two OLR stepchange experiments (from 10.0 kgCOD/m 3/day to 28.1 kgCOD/m3 /day, and from 11.8 kgCOD/m3/day to 32.4 kgCOD/mVday) of twelve hour duration were carried out, followed by a removal of the control system and a similar organic step-change experiment (13.0 kgCOD/m 3/day to 32.9 kgCOD/m 3/day). It was found that approximately halving the HRT had no significant effect on the biomass or biomass activity. The HRT change did however adversely affect the smoothness of control, although control was not lost, as the on-line BA was always kept between 1500 and 2000 mgCaCO3/l. All parameters measured (pH, BA TVFA, effluent COD, carbon dioxide percentage, off-line methane percentage) indicated that conditions were less severe during and after organic step-changes when control was present. The controller also minimised the time spent at pH values potentially damaging to the bacteria (time spent at pH less than 6.0 in the two OLR step-change experiments where control was present (Experiments 6.3 and 6.4) was no greater than one hour, and in the experiment with no control (Experiment 6.5) was 8 hours) and returned the reactor to conditions conducive to efficient waste water treatment faster than when no control was present. Throughout all experiments controller oscillations remained severe. In this case, BA dosing as a control action was preferable, as the destructive effect of severe oscillations in the volume of BA dosed was considerably less than the effect of severe oscillations in the OLR, which repeatedly led to washout. Although it was possible to control the reactor subjected to OLR step-changes using the BA monitor based control system, control of the start-up phase was problematic. The BA monitor was not reliable or robust enough to provide the requisite data for use in the automatic control of the start-up of a high rate anaerobic digester. A thorough professional re-engineering of the B A monitor to deal with a greater sample flow rate, deliverable by a full-scale reactor (using wider bore tubing and larger flows, a more precise pumping system, and possibly with a suitable low maintenance sample filtration unit) could provide a suitably reliable and robust instrument.

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42

Yan, Jing-Qing. "Anaerobic digestion of cheese whey in an upflow anaerobic sludge blanket reactor." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/31898.

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The anaerobic digestion of cheese whey was studied in an upfiow anaerobic sludge blanket reactor for its start-up characteristics, the effects of various process parameters, the effect of sulfate addition and the determination of optimal operating conditions. Start-up of an UASB reactor treating cheese whey was extremely difficult due to its tendency to acidify. Various start-up strategies were tested to facilitate start-up and to ensure stable operation. Among the operating parameters, sludge loading rate was the most critical for proper start-up of the UASB reactor. The initial sludge loading rate during start-up period should not exceed 0.25 g COD/g VSS. The response of whey digestion to several process parameters was investigated. Without pH-control, over 97% COD removal was obtained for influent concentrations from 5 to 28.8 g COD/1 and HRT of 5 days. However, instability was observed when the influent concentration was increased to 38.1 g COD/1. Gas production from whey is affected by organic loading rate (OLR). At an OLR less than 4 g COD/l-d, higher influent strength resulted in a higher methane production rate. When the OLR was greater than 6, higher strength feed or shorter hydraulic retention time (HRT) produced less methane. From the profiles of substrate concentration measured at various levels above the bottom of the reactor, two reaction stages, acidogenesis and methanogenesis were distinguished. It was experimentally illustrated that the rate of acidogenesis is much faster than the rate of methanogenesis in a whey anaerobic digestion system. The accumulation of VFAs in the first stage being faster than its assimilation in the second stage creates a distinct acidogenic phase in the bottom of the reactor. The instability caused by high influent concentration could be attributed to the accumulation of VFAs beyond the assimilative capacity of the methanogenic stage. A set of empirical models for accumulation and degradation of VFAs was developed using linear regression analysis. The requirement for maintaining this system in a dynamic balance was that the degradation capacity for VFA in the second stage be greater than the accumulation of VFA in the first stage. Based on this idea, the optimal influent concentration was given as between 25 to 30 g COD/1 for system stability. A hypothesis was proposed in this study that a proper amount of sulfate may be applied to moderate the detrimental influence of excess hydrogen on a stressed anaerobic reactor. The effect of sulfate was tested to study the biochemical mechanism. The permissible influent COD concentration was increased from 30 g COD/1 to 50 g COD/1 by using sulfate addition. The pH in the reactor was on the average 0.8 units higher and the concentration of butyric acid in the acidogenic phase much lower with added sulfate than without sulfate addition. The significant improvement of process stability and treatment efficiency made by the addition of sulfate clearly illustrated that sulfate acted like a stimulator which helped to maintain conditions favorable to methanogenesis. The mechanism of this stimulation is explained according to thermodynamics and hydrogen regulation which suggested that sulfate is able to promote the β-oxidation of VFAs by consuming hydrogen. A two-stage inhibition mechanism was proposed to explain the inhibition of high VFA concentrations and the stimulation of sulfate. Higher hydrogen pressure is the cause of preliminary inhibition, resulting in the accumulation of VFAs, which subsequently inhibit the activity and growth of methanogens in the second inhibition stage. The mechanism of inhibition of methanogens from VFAs was interpreted as being caused by the acidification of the internal cytoplasm and destruction of the pH gradient by non-ionized acids based on the theory of bacterial membrane transport. A new control strategy for stabilization of an anaerobic system is recommended. Under the optimal operating conditions based on the results in the first three steps, over 97% reduction of COD was achieved when the influent COD was 30 g /l using an HRT of 2 days, an OLR of 16.61 g COD/l-d and sulfate concentration of 0.2 g/1.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

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43

Siddiqui, Zuhaib. "Optimisation of Hydrogen and Methane Production from Co-digested Food Waste and Biosolids using Phase Separated Anaerobic Digestion." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521530.

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44

Demitry, Morris Elya. "Anaerobic Digestion Process Stability and the Extension of the ADM1 for Municipal Sludge Co-Digested with Bakery Waste." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4945.

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Uncertainty about anaerobic digestion process stability is the main issue preventing more widespread use of the process as a source of energy recovery in wastewater treatment facilities. The overall objective of this research was to study the feasibility of enhancing biogas production inside wastewater facilities using co-digestion of municipal sludge with bakery waste. Another objective was to improve the stability index and a mathematical model that can be useful tools to predict the process stability of municipal sludge digestion alone, and when it is mixed with bakery waste, as a substrate for microorganisms. Experiments were conducted in three phases. In phase 1, a full-scale anaerobic digester at Central Weber Sewer Improvement District, Ogden, UT, receiving a mixture of primary and secondary sludge, was monitored for one hundred days. Chemical oxygen demand (COD), and volatile solids (VS) mass balances were conducted to evaluate the stability of the digester and its capability of producing methane gas. The COD mass balance accounted for nearly 90% of the methane gas produced while the VS mass balance showed that 91% of the organic matter removed resulted in biogas formation. Other parameters monitored included: pH, alkalinity, VFA, and propionic acid. The values of these parameters showed that the digester was running under stable steady state conditions. At mesophilic temperature, the stability index was determined and equal to 0.40 L (CH4)/ g(ΔVS) In phase 2, the feasibility of adding BW to MS was tested in batch reactors scale. The biogas production was enhanced and the digester was stable until the range of 37- 40% of BW to 63-60% of MS. The ADM1 coefficients were modified to accurately predict the digester performance. The modified model outputs (pH, VFA, and methane) were within acceptable ranges when compared with the observed data from the batch reactors. In phase 3, the feasibility of MS and BW were tested using an Induced Bed Reactor (IBR) with a 50:50% ratio of MS:BW (COD basis). The process was stable during different hydraulic retention times and the ADM1 was modified to predict the stability of the process in the IBR.

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45

Pathak, Ankit Bidhan. "Anaerobic Co-Digestion of High Strength Food Waste with Municipal Sewage Sludge: An assessment of Digester Performance and gas production." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/48596.

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Anaerobic digestion is perhaps the simplest and most widely accepted method for solids and residuals management in the field of wastewater treatment. An emerging trend with regard to anaerobic digestion is the addition of additional organic or industrial wastes rich in degradable material (COD) that can lead to increased methane production and reduce the energy demand of the facility. The objective of this research was to evaluate the effect of adding significant quantities (>20% of feed volume) of High Strength Food Wastes (HSW) to digesters treating conventional municipal sludge by monitoring key parameters such as pH, influent and effluent solids, ammonia, Volatile Fatty Acids (VFAs) and alkalinity. Daily gas production was also closely monitored. Four digesters were set up and exposed to different food waste loading rates. A comparison was drawn between the performance of these reactors, one of which was fed only with sewage sludge and served as the control. If the bacteria in the system are able to metabolize this additional COD, it should show up as an increase in gas production with little or no increase in effluent COD. Ammonia is another crucial parameter that needs to be closely watched as it can have an inhibitory effect on methane production. As part of this study, the impact of addition of free ammonium (simulating high ammonium concentration in the feed sludge or food waste) on digester performance was assessed. The digesters were closely monitored for signs of poor performance or failure.
Master of Science

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46

Wendland, Claudia. "Anaerobic digestion of blackwater and kitchen refuse." Hamburg : GFEU, 2008. http://d-nb.info/995843090/34.

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47

Nordlander, Eva. "System studies of Anaerobic Co-digestion Processes." Doctoral thesis, Mälardalens högskola, Framtidens energi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-36515.

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Production of biogas through anaerobic digestion is one pathway to achieving the European Union (EU) goals of reducing greenhouse gas emissions, increasing the share of renewable energy, and improving energy efficiency. In this thesis, two different models (Anaerobic Digestion Model No. 1 and an artificial neural network) are used to simulate a full-scale co-digester in order to evaluate the feasibility of such models. This thesis also includes models of two systems to study the inclusion of microalgae in biogas plants and wastewater treatment plants. One of the studies is a life-cycle assessment in which replacement of the ley crop with microalgae is evaluated. The other study concerns the inclusion of microalgae in case studies of biological treatment in three wastewater treatment plants. Finally, the co-digestion between microalgae and sewage sludge has been simulated to evaluate the effect on biogas and methane yield. The results showed that Anaerobic Digestion Model No.1 and the artificial neural network are suitable for replicating the dynamics of a full-scale co-digestion plant. For the tested period, the artificial neural network showed a better fit for biogas and methane content than the Anaerobic Digestion Model No. 1. Simulations showed that co-digestion with microalgae tended to reduce biomethane production. However, this depended on the species and biodegradability of the microalgae. The results also showed that inclusion of microalgae could decrease carbon dioxide emissions in both types of plants and decrease the energy demand of the studied wastewater treatment plants. The extent of the decrease in the wastewater treatment plants depended on surface volume. In the biogas plant, the inclusion of microalgae led to a lower net energy ratio for the methane compared to when using ley crop silage. Both studies show that microalgae cultivation is best suited for use in summer in the northern climate.

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Kearney, Theresa Elizabeth. "Survival of pathogenic bacteria in anaerobic digesters." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334706.

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Yadav, Vibhash Kumar. "Anaerobic digestion of high-sulphate molasses wastewater." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327828.

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50

Kasapgil, Bahar. "Two-phase anaerobic digestion of dairy wastewater." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386051.

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