Anaerobic digestion pathways in biochemistry: a teaching practice / 生物工程学报

Anaerobic digestion is another important anaerobic catabolism pathway besides lactic acid and ethanol fermentation, which is of great significance for recycling resources, maintaining the ecological balance, optimizing the energy structure, alleviating the energy crisis, and promoting the implementation of the "Carbon Peaking and Carbon Neutrality" strategy. However, such an important metabolic process has not been involved in the current textbooks and teaching of biochemistry courses, making the teaching system incomplete. The anaerobic digestion process involves many reactions and complex metabolic pathways. In order to improve the students' understanding to this process, we created a full chart of the whole anaerobic digestion process based on systemic literature review and integrated it into the classroom teaching through the BOPPPS teaching mode. It was found that the classroom teaching assisted by this metabolic chart could help students establish the structural framework of the anaerobic digestion process and enrich the knowledge system of metabolism, achieving a good teaching effect. This paper introduces the content of the metabolic pathways of anaerobic digestion and the design of the teaching process, which would facilitate the teaching reforms and perfection of textbooks for related courses, such as Biochemistry, Environmental Engineering Microbiology and New Energy Engineering.

Gerenciamento de resíduos sólidos orgânicos do Consórcio do Maciço de Baturité: Análise técnica e econômica da geração de biogás por aterro sanitário e usina de digestão anaeróbia / Management of solid organic waste of the Baturité Massif Consortium: a technical and economic analysis of biogas generation from a landfill and an anaerobic digestion plant

RESUMO Os sistemas de recuperação de biogás contribuem para a mitigação de gases do efeito estufa, além de agregarem valor econômico ao processo de decomposição anaeróbia da matéria orgânica. O presente trabalho busca analisar os potenciais energéticos e a viabilidade econômica de implementação de um sistema de recuperação de biogás de aterro sanitário (cenário 1) ou de uma usina de digestão anaeróbia (cenário 2) para o Consórcio do Maciço de Baturité no estado do Ceará, Brasil. Para isso, foi estimada a projeção populacional, seguida da estimativa da produção de biogás pelo software LandGEM. Para o sistema de recuperação de biogás do aterro sanitário, foi obtida a potência ótima de 460 kW, com geração de energia máxima de 3.223.680 kWh/ano, enquanto, para a usina de digestão anaeróbia, foram obtidos valores de potência e energia de 252 kW e 1.986.754,86 kWh, respectivamente. De acordo com a análise econômica, ambos os projetos possuem inviabilidade de implementação, todavia o preço da unidade de energia gerada (kWh) é 42,42% maior para a usina de digestão anaeróbia em relação ao do sistema de recuperação de biogás do aterro sanitário. A metodologia aplicada pode ser utilizada para estudos preliminares em outros tipos de consórcio, contribuindo para melhores gerenciamento de resíduos e aproveitamento energético de sistemas de biogás no país.

ABSTRACT Biogas recovery systems contribute to the mitigation of greenhouse gases, besides adding economic value to the anaerobic decomposition of organic matter. This research aims to analyze the energy potentials and economic feasibility of implementing a landfill biogas recovery system (scenario 1) and an anaerobic digestion plant (scenario 2) for the Baturité Massif Consortium in the state of Ceará, Brazil. To that end, a population projection followed by an estimate of biogas production were made using the LandGEM software. For the biogas recovery system of the landfill, an optimum power of 460 kW and a maximum energy generation of 3,223,680 kWh/yr were obtained, whereas the anaerobic digestion plant resulted a power and energy of 252 kW and 1,986,754.86 kWh respectively. According to the economic analysis, both projects are unfeasible, but the price of the energy unit generated (kWh) is 42.42% higher for the anaerobic digestion plant than for the biogas recovery system of the landfill. The methodology applied can be used for preliminary studies in other consortiums, contributing to a better waste management and energy use of biogas systems in the country.

Microorganisms in the typical anaerobic digestion system of organic solid wastes: a review / 生物工程学报

The facultative anaerobic and strict anaerobic microorganisms enriched and acclimated during the anaerobic digestion process are crucial for the efficiency of the anaerobic digestion system. Most of the problems encountered during running anaerobic digestion processes could be effectively improved via stimulation of microbial metabolic activity. Benefited from the rapid development of microbiome techniques, deeper insights into the microbial diversity in anaerobic digestion systems, e.g. the microbe-microbe interactions and microbe-environment interactions, have been gained. A complex and intricate metabolic network exists in the anaerobic digestion system of solid organic wastes. However, little is known about these interactions and the underlying mechanisms. This review briefly summarized the representative interactions between microbial communities during anaerobic digestion process discovered to date. In addition, typical issues encountered during the anaerobic digestion of solid organic wastes and how microbes can tackle and alleviate these issues were discussed. Finally, future priorities on microbiome research were proposed based on present contribution of microbiome analysis in anaerobic digestion system.

Fatores que influenciam a produção de ácidos carboxílicos a partir de resíduos agroindustriais / Factors that influence the production of carboxylic acids from agroindustrial wastes

RESUMO Os ácidos carboxílicos (ACs) são componentes químicos de base produzidos principalmente a partir da plataforma petroquímica. Entretanto, em razão de impactos ambientais, risco de escassez e elevados preços do petróleo, a produção biológica de AC por meio da digestão anaeróbia de recursos renováveis de baixo custo, como resíduos orgânicos das atividades agroindustriais, vem recebendo atenção crescente. Nesse contexto, o presente artigo objetiva discutir o processo de digestão anaeróbia aliada ao alongamento de cadeia carboxílica, a fim de orientar tomadas de decisão, como, por exemplo, escolha do substrato e definição das condições ambientais e dos parâmetros operacionais. Em geral, as condições que apresentam melhor viabilidade para produção de ácidos carboxílicos de cadeia média (ACCM) são: pH próximo a 6,0; temperatura mesofílica, já que oferece maior estabilidade operacional e os rendimentos obtidos em condições termofílicas não se mostram muito superiores; pressão parcial de hidrogênio (PPH) próxima a 10-5 aliada à limitação de CO2; tempo de residência celular (θc) inferior a 5 dias; e tempo de detenção hidráulica (TDH) baixo para sistemas contínuos. Uma das configurações mais promissoras é o uso de sistemas de dois estágios utilizando baixo pH como inibidor da metanogênese e extração de ACs em linha, para evitar a inibição devido à toxicidade dos produtos.

ABSTRACT Carboxylic acids (CA) are basic chemical components produced mainly through the petrochemical platform. However, due to environmental impacts, risk of scarcity and high petroleum prices, organic production of CA from the anaerobic digestion of low-cost renewable resources, such as organic wastes from agro-industrial activities, has been receiving increasing attention. In this context, the present paper aims to discuss the process of anaerobic digestion allied to the carboxylic chain elongation process, in order to guide decision making such as substrate choice, definition of environmental conditions, and operational parameters. In general, the conditions that present the best viability for MCCA production are: pH close to 6.0; mesophilic temperature since it offers greater operational stability and the yields obtained under thermophilic conditions are not much higher; hydrogen partial pressure (HPP) close to 10-5 combined with CO2 limitation; solids retention time (θc) < 5 days and low hydraulic retention time (HRT) for continuous systems. One of the most promising configurations is the use of two-stage systems using low pH as a methanogenesis inhibitor and inline CA extraction to avoid inhibition due to product toxicity.

Aplicabilidade de sistema reator anaeróbio compartimentado seguida de filtro anaeróbio no tratamento de efluentes de suinocultura de pequeno porte / Applicability of compartmentalized anaerobic reactor system followed by anaerobic filter on small swine wastewater treatment

RESUMO O objetivo deste trabalho foi avaliar o desempenho de um sistema composto de reator anaeróbio compartimentado (RAC) seguido por filtro anaeróbio (FA), tratando águas residuárias de uma granja suinícola de pequeno porte. Foram analisados os parâmetros: pH, ácidos voláteis totais (AVT), demanda química de oxigênio total (DQOt), demanda química de oxigênio dissolvida (DQOdiss), demanda química de oxigênio devida aos sólidos suspensos (DQOSS), sólidos suspensos totais (SST), sólidos suspensos voláteis (SSV) e nitrogênio total kjeldhal (NTK). Os valores efluentes no RAC e no FA, de DQOt, SST e NTK, foram 6.633 e 4.361 mg.L-1, 2.418 e 595 mg.L-1 e 888 e 954 mg.L-1, respectivamente, para uma carga orgânica volumétrica (COV) de 7,01 kgDQO(m3.d)-1 no RAC e 28,3 kgDQO(m3.d)-1 no FA, e tempo de detenção hidráulico de 70,5 e 17,8 h no RAC e no FA, respectivamente. O sistema RAC seguido de FA mostrou eficiência de remoção média de 88,8% para DQOt e 80,5% de SST. Conclui-se que o sistema de tratamento anaeróbio, composto por RAC seguido de FA, foi eficiente na remoção de DQO e SST, possibilitando, nas condições operacionais impostas, alcançar valores médios de remoção acima de 80%, tornando-se uma ótima alternativa de tratamento de efluentes de suinocultura para granjas de pequeno porte.

ABSTRACT The aim of this work was to assess the performance of a system composed by a compartmentalized anaerobic reactor (CAR) followed by anaerobic filter (AF) in the treatment of the wastewater of as mall pigfarm.The following parameters were analyzed: pH, total volatilefatty acids (VFA), total demand of chemical oxygen (DCOt), dissolved chemical oxygen demand (CODdiss), chemical oxygen demand due to suspended solids (CODSS), total suspended solids (TSS), volatile suspended solids (VSS) and total kjeldhal nitrogen (TKN). The effluents and AF values for the CAR, the DCOt, TSS and TKN were 6,633 and 4,361mg.L-1, 2,418 and 595 mg.L-1, and 888 and 954 mg.L-1, respectively, for a volumetric organic load (VOL) of 7.01 kgDCO(m3.d)-1 in CAR and 28.3 kgDCO(m3.d)-1 in AF, and hydraulic detention time of 70.5 hand 17.8 hin CAR and AF, respectively. The CAR system followed by FA presented a mean removal efficiency of 88.8% for COD and 80.5% for TSS. It is concluded that the anaerobic treatment system consisting of CAR followed by AF was efficient in removing DCO and TSS, allowing with the imposed operating conditions to achieve average removal values above 80%, becoming a great alternative for wastewater treatment in small swinefarms.

Efecto del pretratamiento térmico de residuos de alimentos sobre la producción de metano / Effect of the thermal pretreatment of from food waste on methane production

RESUMEN Los residuos de alimentos son el componente principal de los residuos sólidos municipales y dado su elevado contenido de materia orgánica tienen alto potencial de producción de metano, mediante la digestión anaerobia; sin embargo, la predominancia de material lignocelulósico dificulta su hidrólisis. En este estudio, mediante ensayos de potencial bioquímico de metano, se evaluó el efecto de diferentes condiciones de pretratamiento térmico del sustrato, aplicando temperaturas entre 72 - 128°C y tiempos de exposición de 15 - 33 minutos sobre el rendimiento de producción de CH4. Para evaluar el efecto de las condiciones de pretratamiento, se empleó la metodología de superficie de respuesta y la aplicación de los modelos cinéticos de primer orden y de ajuste de Gompertz modificado. Los parámetros cinéticos identificados fueron validados, mediante niveles de confianza, usando la matriz de información de fisher. Se encontró que la región óptima, para alcanzar un mayor rendimiento en la digestión anaerobia, en cuanto a la producción de CH4, superior a 150mLCH4 gSV-1 y tiempos de la fase de latencia menores a 1 día, fue alrededor de 100°C, con tiempos de exposición cercanos a 15 minutos, condición en que se alcanzó una mayor solubilidad y mejorando positivamente la etapa hidrolítica del proceso anaerobio.

ABSTRACT Food waste are the main component of the municipal solid waste and given their high content of organic matter, have high potential for methane production through the anaerobic digestion. However, the predominance of lignocellulosic material hinders its hydrolysis. In this study, by means of assays of biochemical methane potential, the effect of different thermal pre-treatment conditions of the substrate was evaluated by applying temperatures between 72 - 128°C and exposure times of 15 - 33 minutes on the conditions on the performance of CH4. To evaluate the effect of pretreatment, we used the Response Surface Methodology accompanied by the application of first order kinetic and modified Gompertz models. The identified kinetic parameters were validated using confidence levels using the fisher information matrix. It was found that the optimal region, to reach a higher yield in the anaerobic digestion with regard to the production of CH4 higher than 150mLCH4 gVS-1 and lag-phase times less than 1 day, was around 100°C with exposure times close to 15 minutes, condition in which a greater solubility was reached and positively improving the hydrolytic stage of the anaerobic process.

Evaluation of triclosan toxic effects on the methanogenic activity

BACKGROUND: Triclosan (TCS) is an antimicrobial agent widely used in health care and consumer products. This compound is present in sludge of wastewater treatment plants (WWTPs), and because of its bactericidal characteristics, it can inhibit the methanogenic activity in anaerobic digestion (AD) technology. The aim of this study was to evaluate the toxic effects of TCS on the methanogenic activity. RESULTS: Batch anaerobic reactors were used with TCS concentrations of 7.8, 15.7, 23.5, and 31.4 mg/L. These assays consisted in three successive feedings (I, II, and III), wherein the sludge was exposed to each TCS concentration and volatile fatty acid (VFA) substrate. For evaluation of the residual sludge activity during feeding III, only VFA was used. The results showed that the increase in TCS concentrations correlated with the reduction in methane (CH4) production. In this case, the minimum values were achieved for TCS concentration of 31.4 mg/L with CH4 levels between 101.9 and 245.3 during feedings I, II, and III. Regarding the effect of TCS on VFA consumption, an inhibitory effect was detected for TCS concentrations of 23.5 and 31.4 mg/L, with concentrations of acetic, butyric, and propionic acids at the end of the assay (37 d) between 153.6 and 206.8, 62.5 and 60.1, and 93.4 and 110 mg/L, respectively. Regarding the removal of TCS during AD, these values were above 47%. Conclusion: TCS is an inhibitor of methanogenic activity with a decrease between 63 and 70% during the different feedings. The CH4 production was not recovered during feeding III, with inhibition percentages of 21­72%.

Insights into the microbial community structure of anaerobic digestion of municipal solid waste landfill leachate for methane production by adaptive thermophilic granular sludge

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.

Efeito da variação da carga orgânica volumétrica natural na produção de biogás a partir de dejeto suíno em diferentes tempos de retenção hidráulica / The effect of organic loading rate's natural variation on the biogas yields from swine manure digestion at different hydraulic retention time

RESUMO O estudo sobre reatores anaeróbios em laboratório prioriza o controle de determinados parâmetros que são de difícil controle em campo, o que dificulta o processo de scale-up. Entre os parâmetros está a carga orgânica volumétrica (COV). No caso do dejeto suíno, esse parâmetro pode sofrer alterações diárias em função das condições climáticas, das mudanças no manejo, da alimentação dos animais, entre outros. A fim de verificar o impacto dessa variação na produtividade de biogás, foi analisado o comportamento de um reator anaeróbio de mistura completa (CSTR) em dois diferentes tempos de retenção hidráulica (TRHs) - 20 e 30 dias - durante um período total de 180 dias. Os resultados demonstraram que a elevação da COV resulta em piora da eficiência de tratamento, bem como na produção de biogás. O ensaio com TRH de 20 dias obteve uma melhor resposta às alterações de carga orgânica.

ABSTRACT The study of anaerobic digesters at laboratory focuses on the control of certain parameters that are not so easy to control in the field, which makes it difficult to process scale-up. One example is the Organic Loading Rate. To swine manure, this parameter can change daily due to weather conditions, management practices, feeding and others. In order to verify the impact of this fluctuation on biogas yield, the behavior of a CSTR reactor was analyzed in two different Hydraulic Retention Times (20 and 30 days) for a total period of 180 days. The result demonstrated that the increase of OLR result in a decrease of treatment efficiency as well as biogas yields. The study with HRT of 20 days had a better response to changes in organic load.

Ammonia determines transcriptional profile of microorganisms in anaerobic digestion

ABSTRACT Anaerobic digestion is important for the management of livestock manure with high ammonia level. Although ammonia effects on anaerobic digestion have been comprehensively studied, the molecular mechanism underlying ammonia inhibition still remains elusive. In this study, based on metatranscriptomic analysis, the transcriptional profile of microbial community in anaerobic digestion under low (1500 mg L-1) and high NH4 + (5000 mg L-1) concentrations, respectively, were revealed. The results showed that high NH4 + concentrations significantly inhibited methane production but facilitated the accumulations of volatile fatty acids. The expression of methanogenic pathway was significantly inhibited by high NH4 + concentration but most of the other pathways were not significantly affected. Furthermore, the expressions of methanogenic genes which encode acetyl-CoA decarbonylase and methyl-coenzyme M reductase were significantly inhibited by high NH4 + concentration. The inhibition of the co-expressions of the genes which encode acetyl-CoA decarbonylase was observed. Some genes involved in the pathways of aminoacyl-tRNA biosynthesis and ribosome were highly expressed under high NH4 + concentration. Consequently, the ammonia inhibition on anaerobic digestion mainly focused on methanogenic process by suppressing the expressions of genes which encode acetyl-CoA decarbonylase and methyl-coenzyme M reductase. This study improved the accuracy and depth of understanding ammonia inhibition on anaerobic digestion.

Key microbial populations involved in anaerobic degradation of phenol and p-cresol using different inocula

Background: Anaerobic digestion is an alternative bioprocess used to treat effluents containing toxic compounds such as phenol and p-cresol. Selection of an adequate sludge as inoculum containing an adapted microbial consortium is a relevant factor to improve the removal of these pollutants. The objective of this study is to identify the key microorganisms involved in the anaerobic digestion of phenol and p-cresol and elucidate the relevance of the bamA gene abundance (a marker gene for aromatic degraders) in the process, in order to establish new strategies for inocula selection and improve the system's performance. Results: Successive batch anaerobic digestion of phenol and p-cresol was performed using granular or suspended sludge. Granular sludge in comparison to suspended sludge showed higher degradation rates both for phenol (11.3 ± 0.7 vs 8.1 ± 1.1 mg l-1 d-1) and p-cresol (7.8 ± 0.4 vs 3.7 ± 1.0 mg l-1 d-1). After three and four re-feedings of phenol and p-cresol, respectively, the microbial structure from both sludges was clearly different from the original sludges. Anaerobic digestion of phenol and p-cresol generated an abundance increase in Syntrophorhabdus genus and bamA gene, together with hydrogenotrophic and aceticlastic archaea. Analysis of results indicates that differences in methanogenic pathways and levels of Syntrophorhabdus and bamA gene in the inocula, could be the causes of dissimilar degradation rates between each sludge. Conclusions: Syntrophorhabdus and bamA gene play relevant roles in anaerobic degradation of phenolics. Estimation of these components could serve as a fast screening tool to find the most acclimatized sludge to efficiently degrade mono-aromatic compounds.

GIS-Based Estimate of GHG Emission from Livestock in Anambra State of Nigeria

The need for improved livestock waste management in developing countries has been emphasized by various researchers. Consideration has been given globally to advocacy for a transition from fossil energy system to Renewable Energy (RE), based on several socio-economic and environmental advantages. Green House Gas (GHG) from agricultural sector of Anambra State, with appropriate waste management strategy such as Anaerobic Digestion (AD) will definitely mitigate Methane emission hazards and will as well supply the much needed energy for domestic and industrial uses. An investigation was carried out in this study to estimate the Methane Emission Potential (MEP) of the study area as a result of poor livestock waste management system practiced in the area. This was achieved by incorporating Geographical Information System (GIS) capability to the Methane estimation. The result of the study shows that two Local Government Areas (LGA) which are Anambra West and Anambra East were the least in MEP with virtually none and 0.000646 Gg/year respectively. Idemili North LGA with MEP of 0.017962 Gg/year was observed to be the highest in Methane emission. On incorporating spatial density mapping on MEP, Onitsha North and Idemili North LGA were identified as the highest risk LGAs, with MEP of 0.00018 Gg/year and 0.000272 Gg/year respectively. The study suggests that an improved livestock waste management system using AD should be incorporated in the study area especially in the high risk zones of Onitsha and Idemili North LGA.

Evaluation of biogas and syngas as energy vectors for heat and power generation using lignocellulosic biomass as raw material

The use of nonrenewable energy sources to provide the worldwide energy needs has caused different problems such as global warming, water pollution, and smog production. In this sense, lignocellulosic biomass has been postulated as a renewable energy source able to produce energy carriers that can cover this energy demand. Biogas and syngas are two energy vectors that have been suggested to generate heat and power through their use in cogeneration systems. Therefore, the aim of this review is to develop a comparison between these energy vectors considering their main features based on literature reports. In addition, a techno-economic and energy assessment of the heat and power generation using these vectors as energy sources is performed. If lignocellulosic biomass is used as raw material, biogas is more commonly used for cogeneration purposes than syngas. However, syngas from biomass gasification has a great potential to be employed as a chemical platform in the production of value-added products. Moreover, the investment costs to generate heat and power from lignocellulosic materials using the anaerobic digestion technology are higher than those using the gasification technology. As a conclusion, it was evidenced that upgraded biogas has a higher potential to produce heat and power than syngas. Nevertheless, the implementation of both energy vectors into the energy market is important to cover the increasing worldwide energy demand.

Tratabilidade do lodo biológico têxtil e produção de biogás em reator UASB em diferentes temperaturas / Textile biological sludge treatability and biogas production in UASB reactor under different temperatures

RESUMO Neste trabalho avaliou-se o comportamento de um reator UASB em escala laboratorial (16 L) no tratamento de lodo biológico têxtil com produção de biogás, operando em diferentes temperaturas, 35 (mesofílica), 45 e 55ºC (termofílica), com tempo de detenção hidráulica (TDH) constante de 24 h. O reator UASB apresentou-se apto a tratar o lodo têxtil, sendo influenciado positivamente pelo incremento da temperatura, mostrando maiores remoções nas temperaturas termofílicas e com altas taxas de remoção de todos os parâmetros físico-químicos monitorados: demanda química de oxigênio (DQO) (97% em 45 e 55ºC), demanda bioquímica de oxigênio (DBO) (95% em 45ºC e 94% em 55ºC), fósforo total (P-total) (95% a 45 e 55ºC) e nitrogênio total (N-total) (94% a 45 e 55ºC). Quanto à produção de biogás e à concentração de metano, os maiores valores foram observados a 45ºC. Com base nos resultados alcançados, confirmam-se a tratabilidade do lodo têxtil e a produção de biogás em UASB, com melhor performance a 45ºC.

ABSTRACT The aim of this work was to evaluate the behavior of a laboratory-scale UASB reactor (16 L) in the treatment of textile biological sludge with biogas production, operating at different temperatures - 35 (mesophilic), 45 and 55ºC (thermophilic) -, with constant hydraulic retention time of 24 h. The UASB reactor was able to treat the textile sludge, being positively influenced by increasing temperature, with greater removals in thermophilic temperatures and high removal rates of all monitored physical and chemical parameters: chemical oxygen demand (COD) (97% at 45 and 55ºC), biochemical oxygen demand (BOD) (95% at 45ºC and 94% at 55ºC), total phosphorus (P-total) (95% at 45 and 55ºC) and total nitrogen (N-total) (94% at 45 and 55ºC). As for biogas production and methane concentration, the highest values were observed at 45ºC. Based on the results, textile sludge treatability and biogas production in UASB are confirmed, with best performance at 45ºC.

Biohythane production from palm oil mill effluent – a preliminary evaluation of a two-stage anaerobic digestion

@#Aims:This research aims to investigate the potential of biohythane (biohydrogen and biomethane) production from palm oil mill effluent (POME) in a two-stage anaerobic digestion (AD) system.Methodology and results:A two-stage AD system was configured with a thermophilic dark fermenter (TDF) for biohydrogen (H2) production and a thermophilic anaerobic contact digester (TACD) for biomethane (CH4) production. To adjust pH 5.5 for dark fermentation, the settled sludge was recirculated from TACD to TDF. The hydraulic retention time (HRT) applied in TDF and TACD was 3.75 and 6.25 day, respectively.Conclusion, significance and impact of study:The sludge recirculation from TACD was able to adjust the pH in TDF to the optimum value of 5.5. The total COD and TSSdegradation were 63.12 and 77.94 %, respectively. The H2production in TDF was 1.54 L H2/L POME and the CH4production in TACD was 19.87 L CH4/L POME. The H2and CH4yielded 0.085 L/g CODremovedand 0.339 L/g CODremoved, respectively, with total energy recovery equivalent to 661.02 MJ/m3POME. Only 2.28 % of this energy was contributed by H2and the remaining was dominated by CH4.

Balanço de massa no tratamento de resíduos sólidos orgânicos provenientes de restaurantes em biorreator / Mass balance in the treatment of organic wastes from restaurants in bioreactor

RESUMO O tratamento de resíduos sólidos orgânicos por digestão anaeróbia é realizado por um consórcio de micro-organismos, no qual as archaea metanogênicas são as limitantes do processo, por serem mais sensíveis às mudanças nas condições do meio e possuírem crescimento lento. Para acompanhar a evolução do tratamento, algumas variáveis do processo de digestão anaeróbia são monitoradas, dentre elas, a demanda química de oxigênio (DQO), geralmente utilizada para estimar a matéria degradável e passível de ser convertida em biogás. Com o objetivo de avaliar a eficiência do processo de conversão de biomassa em metano, este artigo se baseou no balanço de massa adaptado da literatura, utilizando valores de DQO e volume de biogás gerado no reator anaeróbio, aqui chamado de biorreator. A produção de biogás foi monitorada diariamente utilizando o método de deslocamento de água, com o auxílio de um contador eletrônico. Com base no balanço de massa, o tratamento mostrou-se viável, visto que 50% da concentração de DQO que entrou no sistema foi convertida em gás metano. Comparando-se aos valores descritos na literatura, que se encontram na faixa de 50 a 70%, a eficiência do tratamento poderá ser elevada com ajustes nos parâmetros de controle que influenciam o processo de digestão anaeróbia, tais como manter a temperatura constante em 37°C e o pH e a alcalinidade equilibrados, o que poderá melhorar as condições do meio em todas as etapas de degradação da matéria orgânica e aumentar a conversão em gás metano.

ABSTRACT The treatment of organic solid waste by anaerobic digestion is carried out by a consortium of microorganisms, in which the methanogenic archaea bacteria are the limiting of the process because they are more sensitive to changes in environmental conditions and have slow growth. To monitor the treatment, some variables of anaerobic digester process are monitored, among them, the chemical oxygen demand (COD), usually used to estimate the degradable material and that can be converted into biogas. In order to evaluate the efficiency of biomass conversion process into methane, this article is based on adapted mass balance of the literature using COD values ​​and volume of biogas generated in anaerobic reactor, here called the bioreactor. Biogas production was monitored daily using the water displacement method, with the aid of an electronic counter.The treatment was satisfactory, based on mass balance, which showed that 50% of the amount of COD entered into the system was completely converted into methane gas. Comparing to the values described in the literature that are in the range of 50 to 70%, the treatment efficiency can be elevated with adjustments to control parameters which influence the process of anaerobic digestion, such as keep the temperature constant at 37°C and balanced pH and alkalinity, which can improve the environmental conditions at all stages of degradation of organic matter and increase conversion into methane gas.

Green conversion of municipal solid wastes into fuels and chemicals

Presently, the society is facing a serious challenge for the effective management of the increasing amount of produced municipal solid wastes. The accumulated waste has caused a series of environmental problems such as uncontrolled release of greenhouse gases. Moreover, the increasing amount of wastes has resulted in a shortage of areas available for waste disposal, resulting in a nonsustainable waste management. These problems led to serious public concerns, which in turn resulted in political actions aiming to reduce the amount of wastes reaching the environment. These actions aim to promote sustainable waste management solutions. The main objective of these policies is to promote the recycling of municipal solid waste and the conversion of waste to energy and valuable chemicals. These conversions can be performed using either biological (e.g., anaerobic digestion) or thermochemical processes (e.g., pyrolysis). Research efforts during the last years have been fruitful, and many publications demonstrated the effective conversation of municipal solid waste to energy and chemicals. These processes are discussed in the current review article together with the change of the waste policy that was implemented in the EU during the last years.

Tratamento de efluentes de abatedouro de frangos por meio de reator UASB seguido de filtro anaeróbio / Treatment of waste water poultry slaughter house through UASB reactor followed by anaerobic filter

O Brasil é um dos maiores produtores de aves do mundo e se destaca na exportação de carne de frango, que tem papel relevante na economia do país. Como resultado do crescimento da indústria de processamento do frango, há também um significativo aumento na geração de efluentes. Uma alternativa interessante para o tratamento desses resíduos são os reatores anaeróbios. Este trabalho teve como objetivo avaliar o desempenho do sistema reator UASB-Filtro anaeróbio no tratamento de efluentes de abate de frangos. O estudo foi desenvolvido em um abatedouro avícola, situado na região metropolitana de Belo Horizonte, Minas Gerais. O sistema de tratamento foi composto por peneira estática, caixa de gordura, reator UASB e filtro anaeróbio. A vazão média diária de efluentes do abatedouro foi de 30m³/dia. A carga orgânica aplicada no reator UASB foi de 0,71kg DQO/m³.d. O monitoramento do sistema foi realizado por meio de análises físico-químicas do afluente e dos efluentes da caixa de gordura, reator UASB e filtro anaeróbio. Os parâmetros avaliados foram: temperatura, pH, demanda química de oxigênio (DQO), demanda bioquímica de oxigênio (DBO), sólidos suspensos totais (SST), e sólidos suspensos voláteis (SSV). Os valores efluentes médios encontrados para DBO, DQO e SST foram 106, 290 e 56mg/L, respectivamente. A eficiência de remoção do sistema para DBO variou de 83 a 99%, e para DQO de 50 a 98%. A eficiência de remoção média de SST e SSV foi de 92%. Conclui-se que o sistema reator UASB seguido de filtro anaeróbio apresentou alto desempenho na remoção de sólidos e carga orgânica. Dessa forma, esses reatores tornam-se uma alternativa viável para o tratamento de águas residuárias de frigoríficos, já que oferecem bons resultados de remoção de poluentes.

Brazil is one of the largest poultry producers in the world and stands out in exportation of chicken meat, which plays an important role in the economy. As a result of the growth of the poultry processing industry, there is also a significant increase in the generation of wastewater. An interesting alternative for the treatment of such wastes is anaerobic. This study aimed to evaluate the performance of the system UASB reactor-anaerobic filter on wastewater treatment of slaughtering chickens. The study was conducted in a poultry slaughterhouse located in the metropolitan region of Belo Horizonte, Minas Gerais. The treatment system was composed of static sieve, grease trap, UASB reactor and anaerobic filter. The daily average flow of effluent from the abattoir was 30m³/day. The organic load applied to the UASB reactor was 0.71kg COD/m³.d. The monitoring system was performed by means of physico-chemical analysis of the influent and effluent of fat, UASB reactor and anaerobic filter. The parameters evaluated were: temperature, pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (SS) and volatile suspended solids (VSS). The mean values for effluent BOD, COD and SS were 106, 290 and 56mg/L, respectively. The removal efficiency of BOD to the system ranged 83-99% for COD and 50-98%. The average removal efficiency of SS and SSV were 92%. We conclude that the system UASB reactor followed by anaerobic filter showed high performance in removing solids and organic load. Thus, these reactors become a viable alternative for treating wastewater slaughterhouses, offering good results in removing pollutants.

Análise comparativa dos efeitos da carga orgânica e do tempo de detenção hidráulica na digestão anaeróbia mesofílica de lodo adensado de estação de tratamento de esgoto / Comparison of organic loading rate and hydraulic retention time effects on the mesophilic anaerobic digestion of thickened waste activated sludge

RESUMO Esta pesquisa comparou o desempenho de um digestor anaeróbio de lodo sob diferentes estratégias operacionais. Foi avaliada a influência do aumento da carga orgânica volumétrica (COV) (OP I) e o efeito da redução do tempo de detenção hidráulica (TDH) (OP II e OP III) no processo anaeróbio. As cargas aplicadas variaram entre 0,5 e 4,5 kgSV.m-3.d-1 e o TDH foi reduzido de 15 a 5 dias. Produção de gás metano, degradação do material orgânico e a diversidade microbiana foram utilizadas para medição e comparação do desempenho do processo. Foram necessários períodos de aclimatação a cada nova COV aplicada o que levou às instabilidades na remoção de SV e DQO do lodo. A operação com TDH entre 7 e 5 dias apresentou as maiores eficiências de remoção de SV, superiores a 70%, o que influenciou positivamente na estabilidade do processo. As COV aplicadas de 2,5 e 3,5 kgSV.m-3.d-1 resultaram nas maiores produções de metano durante a OP I. Para TDH inferiores a sete dias a produção de CH4 foi prejudicada apesar da existência de microorganismos metanogênicos atuantes no digestor. Comparativamente, a estratégia de redução do TDH resultou em um melhor desempenho do sistema que a fixação da COV. Quanto menor o TDH aplicado, melhor os resultados obtidos na operação do digestor, sugerindo que a eficiência do processo é otimizada em sistemas de alta carga com operação em baixos tempos de detenção hidráulica.

ABSTRACT This study compared the performance of a pilot anaerobic sludge digester under different operating strategies. The influence of increasing organic loading rate - OLR (OP I) and the effect of hydraulic retention time - HRT reduction (OP II and OP III) in anaerobic process were evaluated. The applied loads ranged between 0.5 and 4.5 kgSV.m-3.d-1; HRT was reduced from 15 to 5 days. Production of methane, organic matter degradation and microbial diversity were used to measure and compare the system´s performance. Acclimation periods were taken for each new OLR applied, leading to instabilities in sludge VS and COD removals. The experimental time with HRT between 7 and 5 days showed the highest VS efficiency removals (higher than 70%), which positively influenced process stability. The applied OLR of 2.5 and 3.5 kgVS.m-3.d-1 resulted in higher yields of methane during OP I. CH4 production showed impaired with HRT lower than 7 days, although it was observed active methanogenic microorganisms in the digester. Comparatively, HRT reduction resulted in a better system performance than the increasing OLR approach. The lower HRT applied, the better the results obtained in the operation of the digester, suggesting that the process efficiency is optimized with high load operation at low hydraulic retention times.

Residuos agroindustriales con potencial para la producción de metano mediante la digestión anaerobia / Agroindustrial wastes methanization and bacterial composition in anaerobic digestion

Las toneladas de residuos orgánicos que se generan anualmente en la agroindustria pueden aprovecharse como materia prima para la producción de metano. Para que los residuos orgánicos se puedan convertir a metano a gran escala, es importante que previamente se realicen sobre ellos pruebas de biodegradabilidad; un parámetro importante que conviene establecer es su potencial bioquímico de metano. En el presente trabajo se estudió la biodegradabilidad, la producción de metano y el comportamiento de poblaciones de eubacterias y arqueobacterias durante la digestión anaerobia de residuos de plátano, mango y papaya provenientes de la agroindustria, adicionando un inóculo microbiano. Los residuos de mango y plátano tenían mayor contenido de materia orgánica (94 y 75 %, respectivamente) que el residuo de papaya con base en su relación sólidos volátiles/sólidos totales. Después de 63 días de tratamiento, la mayor producción de metano se observó en la digestión anaerobia del residuo de plátano: 63,89 ml de metano por g de demanda química de oxígeno del residuo. Los resultados del potencial bioquímico de metano demostraron que el residuo de plátano tiene el mejor potencial para ser usado como materia prima en la producción de metano. A través de un análisis por PCR-DGGE con oligonucleótidos específicos se logró evaluar el tamaño y la composición de las poblaciones de eubacterias y arqueobacterias presentes en la digestión anaerobia de residuos agroindustriales a lo largo del proceso.

The tons of organic waste that are annually generated by agro-industry, can be used as raw material for methane production. For this reason, it is important to previously perform biodegradability tests to organic wastes for their full scale methanization. This paper addresses biodegradability, methane production and the behavior of populations of eubacteria and archaeabacteria during anaerobic digestion of banana, mango and papaya agroindustrial wastes. Mango and banana wastes had higher organic matter content than papaya in terms of their volatile solids and total solid rate (94 and 75 % respectively). After 63 days of treatment, the highest methane production was observed in banana waste anaerobic digestion: 63.89 ml CH4/per gram of chemical oxygen demand of the waste. In the PCR-DGGE molecular analysis, different genomic footprints with oligonucleotides for eubacteria and archeobacteria were found. Biochemical methane potential results proved that banana wastes have the best potential to be used as raw material for methane production. The result of a PCR- DGGE analysis using specific oligonucleotides enabled to identify the behavior of populations of eubacteria and archaeabacteria present during the anaerobic digestion of agroindustrial wastes throughout the process.