Hydrogen has been studying as an alternative energy source to replace fossil fuels. This is justified because, in its combustion is generating primarily water vapor and by its energy content is approximately 2.5 times greater than any fossil fuel. Besides these advantages, hydrogen can be produced from renewable sources, such as various types of industrial and domestic waste rich in carbohydrates. Thus, the purpose of this study was to evaluate the production of hydrogen from a substrate real, the manipueira (wastewater processing cassava), as carbon source in anaerobic fluidized bed reactor (AFBR) operated under a progressive increase in the organic loading rate (OLR). The support material for the adhesion of biomass has been expanded clay (2.8 to 3.35 mm) and the reactor was inoculated with anaerobic sludge thermal pretreatment. The reactor was operated for 164 days and gradually increasing the organic loading rate was obtained by maintaining a constant influent COD (4000 mg. L-1) throughout the operation of the reactor and varying the hydraulic retention time (HRT) of 8 to 1 hour. The production of hydrogen ranged from 0.20 to 2.04 L.h-1.L-1, when the HRT reduced from 8 h to 1 h. The yield had an increase from 0.31 to 1.91 mol H2.mol glucose-1 by reducing the HRT from 8 to 2 h. By lowering the HRT for 1 h, the yield was reduced, reaching a value of 1.20 mol H2.mol glucose-1. The soluble metabolites present during the operation of the reactor were acetic acid, butyric acid, propionic acid and ethanol. The microscopic analysis indicated the presence of bacilli, which are morphologies similar to species of the genus Clostridium sp. and Enterobacter sp., which are known as potential production of hydrogen in fermentation processes. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O hidrogênio vem sendo estudado como fonte alternativa de energia em substituição aos combustíveis fósseis. Isso porque, na sua combustão há geração principalmente de vapor de água e por seu conteúdo energético ser aproximadamente 2,5 vezes maior do que qualquer combustível fóssil. Além dessas vantagens, o hidrogênio pode ser produzido a partir de fontes renováveis, tais como os diversos tipos de resíduos industriais e domésticos ricos em carboidratos. Dessa forma, o objetivo da pesquisa foi avaliar a produção de hidrogênio a partir de um substrato real, a manipueira (água residuária do processamento da mandioca), como fonte de carbono em reator anaeróbio de leito fluidificado (RALF) operado sob aumento progressivo da taxa de carregamento orgânico (TCO). O material suporte para a aderência da biomassa foi argila expandida com diâmetro entre 2,8 3,35 mm e o reator foi inoculado com lodo anaeróbio pré-tratado termicamente. O reator foi operado por 164 dias e o aumento progressivo da taxa de carregamento orgânico foi realizado mantendo a DQO afluente constante (4000 mg. L-1) durante toda a operação do reator e variando o tempo de detenção hidráulica (TDH) de 8 horas até 1 hora. Foi constatado que a produção volumétrica de hidrogênio aumentou de 0,20 até 2,04 L.h-1.L-1, quando foi reduzido o TDH de 8 h para 1 h. E o rendimento sofreu um incremento de 0,31 até 1,91 mol H2.mol glicose-1, com a redução do TDH de 8 para 2 h. Ao reduzir o TDH para 1 h, o rendimento sofreu uma redução, atingindo o valor de 1,20 mol H2.mol glicose-1. Os metabólitos solúveis presentes durante a operação do reator foram o ácido acético, ácido butírico, ácido propiônico e etanol. As análises microscópicas indicaram a presença de bacilos, os quais são morfologias semelhantes às espécies dos gêneros Clostridium sp. e Enterobacter sp., que são conhecidas como potenciais produtoras de hidrogênio em processos fermentativos.

Submitted by Rosangela Silva (rosangela.silva3@unioeste.br) on 2018-05-30T14:15:49Z No. of bitstreams: 2 Thiago Morais de Castro.pdf: 2981699 bytes, checksum: 66cbb29086744ea891ed186377e4ec48 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-05-30T14:15:49Z (GMT). No. of bitstreams: 2 Thiago Morais de Castro.pdf: 2981699 bytes, checksum: 66cbb29086744ea891ed186377e4ec48 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-01-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The main objective of this study was to evaluate the performance of the anaerobic co-digestion of different concentrations of industrial landfill leachate associated with crude residual glycerin, in a continuous anaerobic bioreactor with a fixed-structure bed (ABFSB) in the same process of anaerobic co-digestion. In this way, co-digestion tests were carried out in laboratory scale (400 mL of useful volume), batch operated in mesophilic conditions (30 ± 1 °C), with a 30-day incubation time in which five levels of (0, 1.5, 5, 8.5, and 10%) and five food/microorganism (F/M) levels (0.3, 0.5, 1, 0, 1.5, and 1.7), adopting experimental design of the Central Composite Rotational Design (CCRD). The results indicated a significant effect on the responses: methanogenic potential, removal of organic matter in terms of COD, accumulated production of CH4, and estimation of maximum production of CH4 using the modified Gompertz model, considering a confidence interval of 95% (p <0.05). From the results and with the desirability test it was verified that the ideal mixture was 95.13% of the industrial landfill leachate with 4.87% of the crude residual (v/v) residual glycerin with F/M ratio of 1.61 to optimize the process as a function of the response variables. From this recommended combination, with approximately 5% glycerin added to the leachate (v/v), the performance of ABFSB was evaluated in the co-digestion cited. The performance of the process was evaluated in three stages: biomass adaptation, gradual increase of organic loading rate (OLR) and reduction of alkaline supplementation. After the first 48-day period, the results were favorable to the application of the bioreactor in the evaluated anaerobic co-digestion, since the system presented stable conditions regarding the operational parameters with the addition of alkalinity with sodium bicarbonate (NaHCO3) and biomass adaptation. Thus, the second stage was started with application of increasing OLR (2, 3.5, 7.1 and 11.6 gCOD L-1 d-1). In the OLR of 7.1 gCOD L-1 d-1, the process reached the maximum methane flow rate (MFR) of 7.61 LNCH4 d-1, methane (MY) yield of 0.302 LNCH4 gCODrem-1 and volumetric methane production rate (VMPR) of 2.79 LNCH4 L-1 d-1, with total COD (ERCOD) and soluble COD removal efficiencies (ERsCOD) above 90%. Thus, the condition adopted in the third was OLR of 7.1 gCOD L-1 d-1, CODaffluent of 10.68 gO2 L-1 and hydraulic holding time of 35.2 h, aiming to optimize the quantity effectively required of NaHCO3. The minimum required concentration of alkalinity supplementation was of 0.28 gNaHCO3 gDQOaffluent-1. It is concluded that alkalinity supplementation was an important factor in the stability of the bioreactor. Finally, it is evidenced that the system is promising and that the results can serve as subsidy for industrial landfills to adopt this form of co-digestion, with biogas energy use. / O objetivo principal deste trabalho foi avaliar a codigestão anaeróbia de diferentes concentrações de lixiviado de aterro industrial e glicerina inicialmente em reatores em batelada e posteriormente o desempenho do processo em biorreator anaeróbio de leito fixo ordenado (Continuous Anaerobic Bioreactor with a Fixed-Structure Bed – ABFSB) em fluxo ascedente contínuo. Foram realizados ensaios de codigestão em reatores, em escala de laboratório, operados em batelada em condições mesofílicas (30 ±1 °C), com tempo de incubação de 30 dias, quando foram testados cinco níveis de adição de glicerina ao lixiviado (v/v) (0; 1,5; 5; 8,5 e 10%) e cinco níveis de relação alimento/microrganismo (A/M) (0,3; 0,5; 1,0; 1,5 e 1,7), adotando-se planejamento experimental do tipo Delineamento Composto Central Rotacional (DCCR). Os resultados obtidos indicaram efeito significativo para as variáveis respostas: potencial metanogênico, remoção de matéria orgânica, em termos de DQO, produção acumulada de CH4 e a estimativa da produção máxima de CH4 utilizando o modelo de Gompertz modificado, considerando intervalo de confiança de 95% (p<0,05). A partir dos resultados e com o ensaio da desejabilidade foi verificado que a mistura ideal foi de 95,13% do lixiviado de aterro industrial com 4,87% da glicerina residual bruta (v/v) com relação A/M de 1,61 para otimização do processo em função das variáveis respostas. A partir desta combinação recomendada, com aproximadamente 5% de glicerina adicionada ao lixiviado (v/v), avaliou-se o desempenho do ABFSB na codigestão citada. O desempenho do processo foi avaliado em três etapas: adaptação da biomassa, aumento gradual da carga orgânica volumétrica (COV) e redução da suplementação alcalina. Na primeira etapa o sistema apresentou condições estáveis quanto aos parâmetros operacionais com a suplementação da alcalinidade com bicarbonato de sódio (NaHCO3) e adaptação da biomassa. Na segunda etapa com aplicação de COV crescentes (2; 3,5; 7,1 e 11,6 gDQO L-1 d-1). Na COV de 7,1 gDQO L-1 d-1, o processo atingiu os máximos valores de vazão de metano (MFR) de 7,61 LNCH4 d-1, rendimento de metano (MY) de 0,302 LNCH4 gDQOrem-1 e a produção volumétrica de metano (VMPR) de 2,79 LNCH4 L-1 d-1, com eficiências de remoção de DQO total (ERDQO) e DQO solúvel (ERDQOs) superiores a 90%. Na terceira etapa com o COV de 7,1 gDQO L-1 d-1, DQOafluente de 10,68 gO2 L-1 e TDH de 35,2 h, visando otimizar a quantidade efetivamente necessária de NaHCO3. A concentração mínima necessária da suplementação de alcalinidade foi de 0,28 gNaHCO3 gDQOafluente-1. Concluiu-se que a suplementação da alcalinidade foi um fator de importância na estabilidade do biorreator, ficando evidenciado que o sistema é promissor e que os resultados podem servir de subsídio para que aterros industriais adotem esta forma de codigestão, com aproveitamento energético do biogás.

Este estudo investigou a aplicação de um reator anaeróbio operado em bateladas sequenciais com biomassa imobilizada (AnSBBR) com agitação na produção de biohidrogênio tratando água residuária sintética a base de sacarose, sendo o desempenho do biorreator avaliado de acordo com a influência conjunta do tempo de alimentação, do tempo de ciclo, da concentração afluente e da carga orgânica volumétrica aplicada (COVAS). O biorreator, com capacidade útil de 5,6 L, foi dividido em 3 partes: volume de meio tratado por ciclo de 1,5 L, volume residual de meio de 2,0 L e volume de suporte inerte com biomassa de 2,1 L. Foram aplicadas 6 condições experimentais de COVAS de 9,0 a 27,0 gDQO.L-1.d-1, combinado diferentes concentrações afluentes (3500 e 5400 mgDQO.L-1), tempos de ciclo (4, 3 e 2h), sendo tempo de enchimento do reator (tC) correspondente a 50% ao tempo de ciclo. Os resultados mostraram que o aumento COVAS contribuiu para a queda no consumo de sacarose de 99% para 86% e para o aumento do rendimento molar por carga removida (RMCRC,n) de 1,02 molH2.molSAC-1 na COVAS de 9,0 gDQO.L-1.d-1 até atingir o valor máximo de 1,48 molH2.molSAC-1 na COVAS de 18,0 gDQO.L-1.d-1 com queda a partir desse ponto. O aumento da COVAS resultou no aumento da produtividade molar volumétrica (PrM) de 24,5 para 81,2 molH2.m-3.d-1. A maior produtividade molar específica (PrME) obtida foi de 8,71 molH2.kgSVT-1.d-1 para a COVAS de 18,0 gDQO.L-1.d-1. A diminuição do tempo de ciclo resultou na diminuição do consumo de sacarose e no aumento da PrM. Foi verificado também que a diminuição do tC de 4h para 3h contribuiu para o aumento da PrME. O aumento da concentração afluente resultou na diminuição do consumo de sacarose apenas na faixa de 2h, no aumento do RMCRC,n e da PrM em todas as faixas de tC, e no aumento da PrME nas faixas de 4h e 3h. A estratégia de alimentação mostrou ser um parâmetro operacional de grande importância, sendo o aumento do tempo de enchimento responsável pelo aumento do consumo de sacarose, da PrM, da PrME e do RMCRC,n para todas as COAVS investigadas. Em todas as condições, houve o predomínio do ácido acético seguido pelo etanol, ácido butírico e propiônico. / This study investigated the feasibility of an anaerobic sequencing batch biofilm reactor (AnSBBR) with agitation on biohydrogen production treating synthetic wastewater from sucrose, the performance of the bioreactor was evaluated according the combined influence of fill time, cycle period, influent concentration and applied organic loading rate (COAVS) . The bioreactor, with working volume of 5,6L, was divided in 3 parts: 1,5L of fed volume per cycle, 2,0L of residual medium and 2,1L of inert support and biomass. The reactor was operated under six operating conditions with different COAVS ranging from 9,0 to 27,0 gCOD.L-1.d-1, obtained by the combination of different influent concentrations (3500 e 5400 mgCOD.L-1), cycle periods (4, 3 e 2h) and fill time corresponding to 50% of cycle period. The results showed that increasing COAVS resulted in lesser sucrose removal from 99% to 86% and improved yield per removed loading rate (RMCRC,n) of 1,02 molH2.molSUC-1 in COAVS of 9,0 gCOD.L-1.d-1 to maximum value of 1,48 molH2.molSUC-1 in COAVS of 18,0 gCOD.L-1.d-1 decreasing after that. Increasing COAVS improved molar productivity (PrM) from 24,5 to 81,2 molH2.m-3.d-1. The higher specific molar productivity (PrME) obtained was 8,71 molH2.kgTVS-1.d-1 in COAVS of 18,0 gCOD.L-1.d-1. Decreasing cycle period resulted in less sucrose consumption and increased PrM. It was observed that decreasing cycle period of 4h to 3h improved PrME. Increasing influent concentration resulted in less sucrose degradation only on range of 2h, in an increase of RMCRC,n and in an increase of PrM in all ranges of tC, and increased PrME on ranges of 4h and 3h. In all operational conditions, the main intermediate metabolic was acetic acid followed by ethanol, butyric and propionic acids. The feeding strategy had a great effective on hydrogen production, longer fill times resulted in better sucrose removal, PrM, PrME and RMCRC,n for all COAVS investigated.

The suitability of water hyacinth in biogas production was evaluated as a means of waste management in the interests of sustainable energy production. Batch anaerobic digestion (AD) of water hyacinth was conducted to determine the optimal pre-treatment method for maximum methane production. Physical pre-treatment methods produced a highest cumulative methane of 2.3 L during batch AD. The selected pre-treatment method, hand-cutting, was further evaluated in a semi-continuous AD using both mono- and co-digestion. The emphasis was on identifying microbial communities involved and their response to organic loading rates (OLRs). The Illumina Miseq results proved that bacterial communities were more sensitive to disturbances caused by irregular OLRs as compared to archaeal communities. In addition, the variation in substrate nutrients as a result of mono- and co-digestion of water hyacinth, contributed to variations in the bacterial diversity. For example, Bacteroides and Petrimonas diversity varied between mono- and co-digestion. Overall, the study verified that water hyacinth is a suitable feedstock for biogas production and the simple pre-treatment methods are recommended. Furthermore, OLRs influenced the microbial community structure and associated biogas yield. / National Research Foundation (South Africa) / Environmental Science / M. Sc. (Environmental Science)

Este estudo investigou a aplicação de um AnSBBR com recirculação da fase líquida tratando água residuária a base de glicerina (efluente do processo de produção de biodiesel) para a produção de biohidrogênio, sendo o desempenho do biorreator avaliado de acordo com a influência conjunta do tempo de alimentação, do tempo de ciclo e da concentração afluente. O biorreator teve um volume de meio tratado por ciclo de 1,5 L, volume residual de meio de 2,0 L e volume de suporte inerte com biomassa de 2,1 L, sendo mantido a 30°C durante todo o estudo. O trabalho foi divido em três fases: a Fase I foi realizada para determinar os melhores parâmetros de operação do reator (tipo de inóculo, tipo de glicerina, tipo de suporte, concentração de NaHCO3 e velocidade ascensional) para dar seguimento com a Fase II que estudou apenas o efeito da concentração do afluente, tempo de ciclo e tempo de enchimento. Os parâmetros utilizados na Fase II foram: lodo de abatedouro de aves pré-tratado por HST (Heat Shock Treatment 90°C por 10 minutos) como inóculo, glicerina pura comercial para eliminar interferência de possíveis resíduos, suporte de PEBD (polietileno de baixa densidade) e 100 mg.L-1 de NaHCO3. Na Fase II, foram aplicadas 6 condições experimentais com cargas orgânica volumétrica (COVAS) de 7,7 a 17,1 gDQO.L-1.d-1, combinando diferentes concentrações afluentes (3000, 4000 e 5000 mgDQO.L-1) e tempos de ciclo (4 e 3 h), sendo o tempo de alimentação igual a metade do tempo de ciclo. Os resultados mostraram que houve baixa remoção de DQO (máximo de 38% para amostras filtradas) e que houve predomínio do ácido acético e do ácido butírico em todas as condições. O aumento da XV concentração do afluente e a diminuição do tempo de ciclo favoreceram a produtividade e rendimento molares de hidrogênio nas condições investigadas. O ensaio com melhores resultados foi com carga orgânica de 17,1 gDQO.L-1.d-1 no qual obteve-se 100,8 molH2.m-3.d-1 e 20,0 molH2.kgDQO-1, com 68% de H2 e apenas 3% de CH4 no biogás. Na Fase III, determinou-se a influência do pré-tratamento do inóculo e a viabilidade do sistema tratando glicerina bruta industrial, sendo verificado que o pré-tratamento do lodo por HST melhora ligeiramente a produtividade e rendimento do processo e o uso da glicerina bruta industrial diminuiu consideravelmente a quantidade e qualidade do biogás obtido. / This study investigated the feasibility of an AnSBBR with recirculation of the liquid phase treating glycerin-based wastewater (effluent from biodiesel production process) on biohydrogen production; the performance of the bioreactor was evaluated according the combined influence of fill time, cycle period and influent concentration. The bioreactor had 1.5L of feeding volume per cycle, 2.0 L of residual medium, 2.1 L of inert support and biomass and it was kept at 30°C. This study was divided into three phases. Phase I was conducted to determine the best operational parameters for the reactor (type of inoculum, type of glycerin, type of support for biomass, NaHCO3 concentration and upflow velocity), so Phase II would use these parameters to study only the influence of affluent concentration, cycle time and filling time. The parameters used in Phase II were: sludge from poultry slaughterhouse pretreated by HST (Heat Shock Treatment 90°C for 10 minutes) as inoculum, pure glycerin so there would be no interferences from possible residues, LDPE (low density polyethylene) support, 100 mg.L-1 of NaHCO3 and 10.6 m.h-1 of upflow velocity. Phase II was operated under six conditions with different AOLRS ranging from 7.7 to 17.1 gCOD.L-1.d-1, obtained by the combination of different influent concentrations (3000, 4000 and 5000 mgCOD.L-1) and cycle periods (4 and 3 h), the filling time was equal to half of the cycle lenght. The results showed low COD removal (maximum of 38% for filtrated samples) and high concentrations of acetic acid and butyric acid in all conditions. Increasing the affluent concentration and decreasing the cycle length improved the molar productivy and hydrogen yield in the XVII investigated conditions. The condition with better results was the one operated with 17.1 gCOD.L-1.d-1 of AVOL, it reached 100.8 molH2.m-3.d-1 and 20.0 molH2.kgCOD-1, with 68% of H2 and only 3% of CH4 in its biogas. Phase III determined whether there is a real influence on the pretreatment of the sludge and the feasibility of this system treating industrial glycerin, the results show that the pretreatment of the sludge by HST slightly improves the productivity and the process yield and the wastewater made from industrial glycerin substantially decreased the quantity and the quality of the biogas generated.

Este estudo investigou a aplicação de um AnSBBR com recirculação da fase líquida tratando água residuária a base de glicerina (efluente do processo de produção de biodiesel) para a produção de biohidrogênio, sendo o desempenho do biorreator avaliado de acordo com a influência conjunta do tempo de alimentação, do tempo de ciclo e da concentração afluente. O biorreator teve um volume de meio tratado por ciclo de 1,5 L, volume residual de meio de 2,0 L e volume de suporte inerte com biomassa de 2,1 L, sendo mantido a 30°C durante todo o estudo. O trabalho foi divido em três fases: a Fase I foi realizada para determinar os melhores parâmetros de operação do reator (tipo de inóculo, tipo de glicerina, tipo de suporte, concentração de NaHCO3 e velocidade ascensional) para dar seguimento com a Fase II que estudou apenas o efeito da concentração do afluente, tempo de ciclo e tempo de enchimento. Os parâmetros utilizados na Fase II foram: lodo de abatedouro de aves pré-tratado por HST (Heat Shock Treatment 90°C por 10 minutos) como inóculo, glicerina pura comercial para eliminar interferência de possíveis resíduos, suporte de PEBD (polietileno de baixa densidade) e 100 mg.L-1 de NaHCO3. Na Fase II, foram aplicadas 6 condições experimentais com cargas orgânica volumétrica (COVAS) de 7,7 a 17,1 gDQO.L-1.d-1, combinando diferentes concentrações afluentes (3000, 4000 e 5000 mgDQO.L-1) e tempos de ciclo (4 e 3 h), sendo o tempo de alimentação igual a metade do tempo de ciclo. Os resultados mostraram que houve baixa remoção de DQO (máximo de 38% para amostras filtradas) e que houve predomínio do ácido acético e do ácido butírico em todas as condições. O aumento da XV concentração do afluente e a diminuição do tempo de ciclo favoreceram a produtividade e rendimento molares de hidrogênio nas condições investigadas. O ensaio com melhores resultados foi com carga orgânica de 17,1 gDQO.L-1.d-1 no qual obteve-se 100,8 molH2.m-3.d-1 e 20,0 molH2.kgDQO-1, com 68% de H2 e apenas 3% de CH4 no biogás. Na Fase III, determinou-se a influência do pré-tratamento do inóculo e a viabilidade do sistema tratando glicerina bruta industrial, sendo verificado que o pré-tratamento do lodo por HST melhora ligeiramente a produtividade e rendimento do processo e o uso da glicerina bruta industrial diminuiu consideravelmente a quantidade e qualidade do biogás obtido. / This study investigated the feasibility of an AnSBBR with recirculation of the liquid phase treating glycerin-based wastewater (effluent from biodiesel production process) on biohydrogen production; the performance of the bioreactor was evaluated according the combined influence of fill time, cycle period and influent concentration. The bioreactor had 1.5L of feeding volume per cycle, 2.0 L of residual medium, 2.1 L of inert support and biomass and it was kept at 30°C. This study was divided into three phases. Phase I was conducted to determine the best operational parameters for the reactor (type of inoculum, type of glycerin, type of support for biomass, NaHCO3 concentration and upflow velocity), so Phase II would use these parameters to study only the influence of affluent concentration, cycle time and filling time. The parameters used in Phase II were: sludge from poultry slaughterhouse pretreated by HST (Heat Shock Treatment 90°C for 10 minutes) as inoculum, pure glycerin so there would be no interferences from possible residues, LDPE (low density polyethylene) support, 100 mg.L-1 of NaHCO3 and 10.6 m.h-1 of upflow velocity. Phase II was operated under six conditions with different AOLRS ranging from 7.7 to 17.1 gCOD.L-1.d-1, obtained by the combination of different influent concentrations (3000, 4000 and 5000 mgCOD.L-1) and cycle periods (4 and 3 h), the filling time was equal to half of the cycle lenght. The results showed low COD removal (maximum of 38% for filtrated samples) and high concentrations of acetic acid and butyric acid in all conditions. Increasing the affluent concentration and decreasing the cycle length improved the molar productivy and hydrogen yield in the XVII investigated conditions. The condition with better results was the one operated with 17.1 gCOD.L-1.d-1 of AVOL, it reached 100.8 molH2.m-3.d-1 and 20.0 molH2.kgCOD-1, with 68% of H2 and only 3% of CH4 in its biogas. Phase III determined whether there is a real influence on the pretreatment of the sludge and the feasibility of this system treating industrial glycerin, the results show that the pretreatment of the sludge by HST slightly improves the productivity and the process yield and the wastewater made from industrial glycerin substantially decreased the quantity and the quality of the biogas generated.

Municipal wastewater treatment plants (WWTP) are important infrastructural components in a society and also important for sustainability. In a WWTP the most common treatment configuration is mechanical, biological, and chemical treatment of the wastewater. The treatments reduce nutrients and organic matter before the water is transferred to the recipient. During wastewater treatment, sludge is produced and then stabilized in an anaerobic digestion (AD) process.  The Käppala Association operates the third largest WWTP in Sweden. In the future the Käppala plant is expecting an increased number of connected households and also stricter sludge hygienization regulations. This implies that current strategies for the WWTP have to be developed. One idea has been to use a thermophilic AD process instead of mesophilic AD.Thermophilic AD has previously been shown to have higher capacities, lower hydraulic retention times (HRT) and increased pathogenic destruction compared to their mesophilic counterpart. A common negative aspect for a thermophilic process has been process instability.  In this study a 5 m3 pilot plant rented from Research Institutes of Sweden (RISE) was used to evaluate maximal organic loading rate (OLR) for a stable thermophilic AD process using mixed sludge as substrate. Four HRT were chosen, and each HRT was maintained for 3 retention times. Laboratory analyzes of the raw and digested sludge and on-line monitoring were performed regularly to collect information about process stability and efficiency. The pilot plant was controlled through a surveillance system where operating parameters were introduced. The main objectives of this study were to investigate how an increase of OLR affected pH, alkalinity, and volatile fatty acid (VFA) content and also how the alkalinity and VFA affected the process stability. Gas composition, gas production, degree of digestion (DD) and foaming were also investigated throughout this study. Results showed that VFA initially increased, and alkalinity decreased when every OLR increase occurred. The VFA and alkalinity returned to lower values after the process was given time to recover during constant OLR. The OLR increase caused slight variations in process pH but not enough for process failure. Increased OLR did not seem to have a large impact on the DD since it seemed to remain between 40-50% throughout the entire study. Composition monitoring showed an increased hydrogen sulfide content in the gas as a consequence of increased OLR. An OLR increase also lead to a volumetric gas production (VGP) and volumetric methane production (VMP) increase while efficiency of the AD process was seen to decrease when evaluating specific gas production (SGP) and specific methane production (SMP). The conclusion of the study was that a stable thermophilic AD process using mixed sludge as substrate could be operated with an OLR of 6.55 ± 0.06 kg VS m-3d-1and a HRT of 7 days. Maximal OLR for a stable thermophilic AD process was never achieved due to the process remaining relatively stable the entire experimental period. The process recovered from signs of instability during all HRT-transition times indicating it can maintain all investigated OLR. / Kommunala avloppsreningsverk är en viktig infrastruktur i ett samhälle och även viktigt för hållbarheten. I ett avloppsreningsverk renas spillvatten genom mekaniska, biologiska och kemiska behandlingar processteg. Behandlingarna minskar näringsämnen och organiskt material innan vattnet rinner ut i recipienten. Vid rening av avloppsvatten erhålls slam. Slammet kan användas som substrat för en anaerobisk nedbrytningsprocess. Käppalaförbundet driver det tredje största reningsverket i Sverige. I framtiden förväntas antal anslutna hushåll till reningsverket att öka samt strängare slamhanteringskrav appliceras. Detta innebär att nuvarande slamstrategi måste utvecklas. En idé är att tillämpa en termofilrötnings process. En termofil rötningsprocess har visat sig ha högre kapacitet, lägre uppehållstider och ökad patogen reduktion i jämförelse med en mesofil rötning. En nackdel med termofil rötning är den försämrade processtabiliteten.  I denna studie har en 5 m3 pilotanläggning inhyrd från RISE använts för att utvärdera den maximala organiska belastningen för en stabil termofil rötningsprocess med blandslam som substrat. Fyra uppehållstider valdes och varje uppehållstid hölls tre gånger. Regelbundna analyser av rå och rötslam utfördes för att erhålla information om process stabilitet och effektivitet. Pilotanläggningen styrdes genom ett människa-maskingränssnitt där driftparametrar matades in. Huvudmålen för studien var att se hur en ökning av organisk belastning påverkade pH, alkaliniteten och halt av flyktiga fettsyror samt att undersöka alkalinitetens och halten av flyktiga fettsyrors påverkan på processtabiliteten. Påverkan av en ökad organisk belastning på gas sammansättning, gasproduktion, rötningsgrad har även undersökts. Resultaten visade att flyktiga fettsyror initialt ökade och alkaliniteten minskade vid en belastnings ökning. Flyktiga syror och alkalinitet återgick till mer stabila värden efter processen fick återhämta sig vid en konstant belastning. Belastningsökningen orsakade små variationer i pH värdet men inte tillräckligt för att orsaka processkollaps. En ökad belastning verkade inte ha någon större påverkan på rötningsgraden då den låg runt 40–50% hela rötningsperioden. Skumutvecklingen visade sig inte heller vara ett problem. Resultaten visade även att väte sulfid ökade i gasen när en belastningsökning gjordes. Den volymetriska gas och metan produktionen ökade vid en ökad OLR medan specifika gas och metan produktionen minskade. Slutsatsen var att en stabil termofil rötningsprocess av blandslam kan drivas med en organisk belastning på 6.55 ± 0.06 kg VS m-3d-1 och en uppehållstid på 7 dagar. Maximal belastning för stabil termofil rötningsprocess uppnåddes dock ej då processen förblev relativt stabil under alla undersökta uppehållstider. Processen återhämtade sig även efter tecken på instabilitet vilket indikerar att AD processen kan behålla stabilitet vid de undersökta belastningar.

Kommunala avloppsreningsverk renar avloppsvatten och avlägsnar näringsämnen innan vattnet släpps ut i den omgivande miljön. Under reningen avskiljs partiklar som bildar råslam. Genom att bryta ner råslammet anaerobt (syrefritt) via rötning kan användbara produkter, såsom biogas till bussar, erhållas. Rötning innebär att organiskt material bryts ner under kontrollerade former. Sveriges tredje största kommunala avloppsreningsverk är Käppalaverket i Stockholm. Framtidsprognosen för verket visar att belastningen kommer öka, samtidigt förväntas kraven på slamhantering bli strängare.  Syftet med denna studie var att utreda en metod för att öka Käppalaverkets slambehandlingskapacitet. Idag rötas slammet konventionellt med mesofil rötning. Ett förslag för att öka kapaciteten är att förtjocka och därefter recirkulera slammet in i samma rötningskammare. Möjliga fördelar med detta kan vara ökad biogasproduktion samt möjlighet till högre belastning i rötkamrarna.  Till experimentet nyttjades en pilotanläggning bestående av två rötkammrar på 7 dm3. Rötkamrarna användes för att studera konventionell mesofil rötning (i studien benämnd BR01), jämfört med mesofil rötning med recirkulering (i studien benämnd BR02). Råslammet och rötslammet analyserades löpande (på dag- och veckobasis) med avseende på parametrarna: biogasproduktion och gassammansättning, torrsubstanshalt, halt av flyktiga syror, pH, alkalinitet, organisk belastning, andel mineraliserat kväve, utrötningsgrad samt reduktion av makromolekyler. Uppehållstiden (HRT) för slammet i rötkamrarna var inledningsvis 14 dagar. HRT sänktes stegvis  under studien (från 14 till 11 dagar och därefter till 9 dagar) genom att inflödet av råslam ökades. Därmed pressades BR01 och BR02 i syfte att utröna vid vilken belastning rötningsprocessen förändrades från stabil till instabil. Resultaten visade att under 11-dagars perioden var processen i BR01 stabilare än i BR02. Förhöjda halter av flyktiga syror uppmättes i BR02 under denna period. Under 9-dagars perioden med högre belastning observerades att processen i BR01 var instabil. Processen i BR02 var stabilare under samma period och ansågs därför prestera bättre under högre belastning. Statistiska t-tester visade att flertalet reaktorparametrar (i en och samma reaktor) genomgick säkerställda förändringar från experimentets start till slut. / Municipal wastewater treatment plants (WWTPs) purifies wastewater from nutrients before releasing it to the recipient. Particles that are separated from the water creates a sewage sludge. Anaerobic (without oxygen) digestion is mainly used as a stabilization method for the sludge. Digestion of the sludge produces energy-rich biogas and a nutrient-rich digestate which can be used as a fertilizer. The third largest municipal WWTP in Sweden is Käppala WWTP, situated in Stockholm. In the future, the amount of incoming wastewater is expected to increase. Simultaneously, regulations regarding sludge management are expected to be stricter. The main purpose of this study was to investigate a method to increase the sludge load to the digesters at Käppala WWTP. Today the sludge is digested conventionally with mesophilic anaerobic digestion. One suggestion is to recirculate thickened sludge into the same digestion reactor. This method has been shown to give an increased biogas production as well as improved digester performance.   During the experiment a pilot-digester consisting of two anaerobic reactors (each with a volume of 7 dm3) were used. These reactors were used to study conventional mesophilic digestion (BR01 in this study) and mesophilic digestion with sludge-recirculation (BR02 in this study). Several parameters of the sludge (raw and digested) were analysed on daily and weekly basis: biogas production and gas composition, dry matter content, volatile fatty acids, pH, alkalinity, organic loading, mineralised nitrogen, degree of digestion and reduction of macromolecules. The hydraulic retention time (HRT) of the sludge was initially 14 days. HRT was lowered stepwise (from 14 to 11 and finally down to 9 days) by increasing the inflow of raw sludge. This way the two reactors were pushed to see at what point the digestion process became unstable. The results showed that during the 11-days HRT period BR01 was more stable compared to BR02. Heightened VFA-content was measured in BR02 during this period. During the 9-days HRT period the process in BR01 was deemed unstable. The process in BR02 was more stable during the same period and was considered to have a better performance during high sludge inflow. Statistical t-tests showed that several digestion-parameters (compared for the same reactor) underwent statistically significant changes from the start to the end of the experiment.

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AD is regarded as a sustainable technology that could assist the UK Government meet internationally agreed GHG emission targets by 2050. However, the mature status of the technology is based on expensive systems that rely on high energy feedstock to be profitable. Meanwhile, the natural biodegradation of cow slurry is a recognised contributor to climate change despite having a relatively low CH4 potential because of the large volumes produced. Economic mixing is essential to the cost-effectiveness of farm AD but techniques applied are not always appropriate as slurry is a shear thinning thixotropic Herschel-Bulkley fluid and therefore challenging to mix. The apparent viscosity of slurry and the shear stress induced was most influenced by solids content (exponential change) followed by temperature (linear). Most shear thinning occurred before a rising shear rate of 20s-1 was achieved with the fluid acting near-Newtonian above. Thixotropic recovery occurred within 1 hour of resting. Rheological values were also much higher than previously reported. Highest CH4 production occurred in the first 10 days of the batch process using a range of mixing regimes with different shear rates and rest periods. During fed-batch operations, changing shear rate had a minimal effect on CH4 production using a 30-day HRT whereas shorter rest periods increased production. Specific CH4 production rate was highest when feeding and mixing coincided. However, when HRT was reduced (OLR increased) the CH4 produced by all mixed regimes significantly increased with highest values being achieved using high intensity mixing rested for short periods. Lower HRTs also requires smaller digesters. Parasitic mixing energy invariably had the most influence on net energy production. Signs of instability were evident after 20 days using the low HRT. Significant microbial adaptation was also observed as the experiments progressed. The research outcomes demonstrate that mixing regime and HRT can be managed to maximise net energy production whilst reducing capital expenditure.