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BACKGROUND: The amount of municipal solid waste (MSW) gradually increased along with the rapid development of modern cities. A large amount of landfill leachate are generated with excessive chemical oxygen demand (COD), which create a great deal of pressure on the environment-friendly treatment process. Anaerobic digestion is an ideal technique to solve the above problem. RESULTS: A thermophilic granular sludge was successfully adapted for anaerobic digestion of MSW leachate (from an aging large-scale landfill) for methane production. The COD degradation efficiency improved by 81.8%, while the methane production rate reached 117.3 mL CH4/(g VS d), which was 2.34-fold more than the control condition. The bacterial and archaeal communities involved in the process were revealed by 16S rRNA gene high-throughput pyrosequencing. The richness of the bacterial community decreased in the process of thermophilic granular sludge, while the archaeal community structure presented a reverse phenomenon. The bacterial genus, Methanosaeta was the most abundant during the mesophilic process, while Methanobacterium, Methanoculleus, Methanosaeta and Methanosarcina were more evenly distributed. The more balanced community distribution between hydrogenotrophic and acetotrophic methanogens implied a closer interaction between the microbes, which further contributed to higher methane productivity. The detailed relationship between the key functional communities and anaerobic digestion performances were demonstrated via the multivariate canonical correspondence analysis. Conclusions: With the assistance of adaptive thermophilic granular sludge, microbial community structure was more evenly distributed, while both of COD degradation rate and methane production was improved during anaerobic digestion of MSW landfill leachate.

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In microbial fuel cells (MFCs), the oxidation of organic compounds catalyzed by microorganisms (anode) generates electricity via electron transfer to an external circuit that acts as an electron acceptor (cathode). Microbial fuel cells differ in terms of the microorganisms employed and the nature of the oxidized organic compound. In this study, a consortium of anaerobic microorganisms helped to treat the secondary sludge obtained from a sewage treatment plant. The microorganisms were grown in a 250 mL bioreactor containing a carbon cloth. The reactor was fed with media containing acetate (as the carbon source) for 48 days. Concomitantly, the electrochemical data were measured with the aid of a digital multimeter and data acquisition system. At the beginning of the MFC operation, power density was low, probably due to slow microorganism growth and adhesion. The power density increased from the 15th day of operation, reaching a value of 13.5 W cm2 after ca. 24 days of operation, and remained stable until the end of the process. Compared with data in the literature, this power density value is promising; improvements in the MFC design and operation could increase this value even further. The system investigated herein employed excess sludge as a biocatalyst in an MFC. This opens up the possibility of using organic acids and/or carbohydrate-rich effluents to feed MFCs, and thereby provide simultaneous effluent treatment and energy generation.

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In microbial fuel cells (MFCs), the oxidation of organic compounds catalyzed by microorganisms (anode) generates electricity via electron transfer to an external circuit that acts as an electron acceptor (cathode). Microbial fuel cells differ in terms of the microorganisms employed and the nature of the oxidized organic compound. In this study, a consortium of anaerobic microorganisms helped to treat the secondary sludge obtained from a sewage treatment plant. The microorganisms were grown in a 250 mL bioreactor containing a carbon cloth. The reactor was fed with media containing acetate (as the carbon source) for 48 days. Concomitantly, the electrochemical data were measured with the aid of a digital multimeter and data acquisition system. At the beginning of the MFC operation, power density was low, probably due to slow microorganism growth and adhesion. The power density increased from the 15th day of operation, reaching a value of 13.5 W cm2 after ca. 24 days of operation, and remained stable until the end of the process. Compared with data in the literature, this power density value is promising; improvements in the MFC design and operation could increase this value even further. The system investigated herein employed excess sludge as a biocatalyst in an MFC. This opens up the possibility of using organic acids and/or carbohydrate-rich effluents to feed MFCs, and thereby provide simultaneous effluent treatment and energy generation.(AU)

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Microalgal heterotrophic bioreactors are a potential technological development that can convert organic matter, nitrogen and phosphorus of wastewaters into a biomass suitable for energy production. The aim of this work was to evaluate the performance of microalgal heterotrophic bioreactors in the secondary treatment of cattle-slaughterhouse wastewater and the reuse of microalgal sludge for biodiesel production. The experiments were performed in a bubble column bioreactor using the microalgae Phormidium sp. Heterotrophic microalgal bioreactors removed 90 % of the chemical oxygen demand, 57 % of total nitrogen and 52 % of total phosphorus. Substantial microalgal sludge is produced in the process (substrate yield coefficient of 0.43 mg sludge mg chemical oxygen demand¹), resulting in a biomass with high potential for producing biodiesel (ester content of more than 99 %, cetane number of 55, iodine value of 73.5 g iodine 100 g¹, unsaturation degree of ~75 % and a cold filter plugging point of 5 ºC).

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Microalgal heterotrophic bioreactors are a potential technological development that can convert organic matter, nitrogen and phosphorus of wastewaters into a biomass suitable for energy production. The aim of this work was to evaluate the performance of microalgal heterotrophic bioreactors in the secondary treatment of cattle-slaughterhouse wastewater and the reuse of microalgal sludge for biodiesel production. The experiments were performed in a bubble column bioreactor using the microalgae Phormidium sp. Heterotrophic microalgal bioreactors removed 90 % of the chemical oxygen demand, 57 % of total nitrogen and 52 % of total phosphorus. Substantial microalgal sludge is produced in the process (substrate yield coefficient of 0.43 mg sludge mg chemical oxygen demand¹), resulting in a biomass with high potential for producing biodiesel (ester content of more than 99 %, cetane number of 55, iodine value of 73.5 g iodine 100 g¹, unsaturation degree of ~75 % and a cold filter plugging point of 5 ºC).(AU)

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Este estudo teve como objetivo avaliar a presença de rotavírus (RVA), adenovírus (AdV), norovírus (NoV) e vírus da hepatite A (HAV) em amostras ambientais (esgoto e lodo de esgoto primário e tratado) geradas e obtidas em diferentes Estações de Tratamento de Esgoto (ETEs) da cidade do Rio de Janeiro pela detecção, quantificação e caracterização molecular, assim como determinar a eficiência de diferentes metodologias de recuperação viral em lodo de esgoto. A concentração destes vírus foi determinada em ETEs hospitalares que operam por processos anaeróbios (reator UASB e filtros anaeróbios) e aeróbio (lodo ativado de aeração prolongada) e em uma ETE urbana de grande porte (Alegria, Caju) que utiliza processo de lodo ativado convencional. Os resultados demonstraram que os efluentes hospitalares são contaminados com elevadas cargas virais, especialmente RVA, apontando para o risco da disseminação ambiental quando processos de tratamento biológicos convencionais (aeróbios e anaeróbios) não são adequados para a remoção viral. Uma grande variabilidade de genótipos virais foi encontrada nos efluentes hospitalares, particularmente para AdV, para os quais foram detectadas espécies C e D, comumente envolvidas em casos de infecções respiratórias e conjuntivite nosocomial. Apenas genótipo GII.4 de NoV foi detectado nos efluentes hospitalares, confirmando a prevalência desse genótipo no Brasil. No estudo que avaliou a detecção de HAV nas águas residuárias urbanas foi constatado que 58 por cento das amostras de esgoto bruto foram positivas para HAV e as cargas de genomas virais não foram detectadas nos efluentes tratados do processo de lodo ativado convencional. A análise filogenética baseada na região do genoma VP1/2A de HAV detectados em 2009-2010 demonstrou a prevalência do subgenótipo IA e os isolados apresentaram maior identidade de nucleotídeos com isolados de HAV do Brasil e Argentina. A detecção viral obtida em diversas etapas da ETE de grande porte demonstrou a predominância de RVA e AdV e o sistema de lodo ativado convencional reduziu as cargas de genomas virais em 1 – 1,5 unidades log10 no efluente final tratado. A análise da eficiência dos métodos de detecção viral em lodo de esgoto demonstrou que a presença de inibidores nas amostras afeta o desempenho da amplificação de ácidos nucléicos e o uso do controle interno (bacteriófago PP7) pode ser adequado para monitorar as etapas de detecção viral. O método baseado na eluição utilizando extrato de carne foi o mais viável para recuperar os vírus pesquisados, sobretudo AdV em lodo de esgoto. Os AdV foram predominantes nas amostras de lodo de esgoto tratado e, portanto, poderiam ser considerados bons indicadores para a presença de vírus de disseminação entérica nesses resíduos. Esse é o primeiro estudo demonstrando a ocorrência de RVA e NoV GII em lodo de esgoto digerido anaerobicamente no Brasil, e espera-se que esse trabalho contribua para expandir essa linha de investigação, incluindo a análise de biossólidos produzidos por outros processos de estabilização.

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A process configuration combining thermal hydrolysis (TH) and anaerobic digestion (AD) of sludge has been studied with the objective of analysing the feasibility of the technology for full scale installations. The study has been performed through pilot scale experiments and energy integration considerations, and a scheme of the most profitable option is presented: thermal hydrolysis unit fed with 7 percent total solids (TS) secondary sludge, anaerobic digestion of the hydrolysed sludge together with fresh primary sludge, and a cogeneration unit to produce green electricity and provide hot steam for the thermal hydrolysis process. From a technical and practical point of view, the process scheme proposed is considered to be feasible. Based on the results of the pilot plant performance and the laboratory studies, the process has proven to operate successfully at a concentration of 7-8 percent TS. After the thermal hydrolysis, sludge viscosity becomes radically smaller, and this favours the digesters mixing and performance (40 percent more biogas can be obtained in nearly half the residence time compared to the conventional digestion). From an economic point of view, the key factors in the energy balance are: the recovery of heat from hot streams, and the concentration of sludge. The article presents the main energy integration schemes and defines the most profitable one: an energetically self-sufficient process, with a cogeneration unit. The scheme proposed has proven to need no additional energy input for the sludge hydrolysis, generates more that 1 MW green electricity (246 kW surplus with respect to the conventional process), and produces 58 percent less volume of Class A biowaste. The study and balances here presented set the basis for the scale-up to a demonstration plant (hydrolysis + anaerobic digestion + cogeneration unit).

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Membranes themselves represent a significant cost for the full scale application of anaerobic membrane bioreactors (AnMBR). The possibility of operating an AnMBR with a self-forming dynamic membrane generated by the substances present in the reactor liquor would translate into an important saving. A self-forming dynamic membrane only requires a support material over which a cake layer is formed, which determines the rejection properties of the system. The present research studies the application of self-forming dynamic membranes in AnMBRs. An AnMBR was operated under thermophilic and mesophilic conditions, using woven and non woven materials as support for the dynamic membranes. Results showed that the formation of a cake layer over the support materials enables the retention of more than 99 percent of the solids present in the reactor. However, only low levels of flux were achieved, up to 3 L/m² x h, and reactor operation was unstable, with sudden increases in filtration resistance, due to excessive cake layer formation. Further fine-tuning of the proposed technology involves looking for conditions that can control effectively cake layer formation.

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A finalidade deste trabalho é apresentar uma avaliação da etapa de tratamento de lodos da Estação de Tratamento de Esgotos do Arrudas (Belo Horizonte), em especial os teores de sólidos ao longo do sistema, as principais variáveis de projeto e operação. O processo de tratamento é o de lodos ativados convencional com adensamento por gravidade, digestão anaeróbia e desidratação mecânica. Desde sua entrada em operação até o momento, a estação passou por três fases operacionais quanto ao adensamento dos lodos. A maior concentração média do lodo primário (4,8 por cento) foi atingida no adensador por gravidade quando esse recebia apenas lodo primário. O lodo misto alcançou uma concentração média de 2,7 por cento enquanto o valor esperado de projeto era 5,0 por cento. O lodo secundário excedente, concentrado no adensador por gravidade não ultrapassou 1,8 por cento. A maior concentração média da torta do lodo desidratado (28,3 por cento) foi obtida quando o lodo digerido era proveniente do tratamento primário.

This paper aims to evaluate the sludge treatment stage at the Arrudas Wastewater Treatment Plant (Belo Horizonte, Brazil), especially the solids contents throughout the sludge treatment line, as well as the main design and operating variables. The conventional activated sludge plant has a typical solids-line flowsheet: gravity thickening, anaerobic digestion and mechanical dewatering. Three main operational phases have been identified, whose implications in the plant behaviour are analysed in the paper. The highest concentration of primary sludge (mean value of 4.8 percent) was reached in the gravitational thickening when it was fed with primary sludge only. The mixed sludge concentrated in the gravitational thickening reached only a mean concentration of 2.7 percent, whereas the expected result was 5.0 percent. The excess secondary sludge concentrated in the gravitational thickener did not reach 1.8 percent. The largest concentration of the dewatered sludge cake (means value of 28.3 percent) was obtained when the digested sludge came from the primary treatment.

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Esse artigo apresenta uma revisão sobre os diferentes protocolos para a determinação da atividade metanogênica específica (AME) de lodos anaeróbios. Os protocolos propostos se diferem tanto em relação aos procedimentos adotados para a incubação do lodo, quanto ao método utilizado para quantificação do metano produzido durante o teste. São discutidos os princípios dos métodos manométricos e volumétricos, e descritos brevemente os protocolos de incubação do lodo, de medição do metano e o procedimento para cálculo da AME obtida pelos métodos mais utilizados pela comunidade científica nacional.

This paper presents a review on the different methodologies to determine the specific methanogenic activity (SMA) of anaerobic sludges. The protocols available in the literature differ not only regarding the procedures adopted to incubate the sludge, but also in relation to the method utilized to quantify the methane produced during the test. This paper discusses the principles of manometric and volumetric methods, and briefly describes the protocols mostly used by the Brazilian research community for sludge incubation, methane measurement and calculation of SMA.

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