High-rate anaerobic reactors treating coffee processing wastewater at different OLR and post-treatments: effects on methane production, effluent quality and microbial populations.
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Data
2018-06-05
Autores
Botello Suárez, Wilmar Alirio
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Universidade Estadual Paulista (Unesp)
Resumo
Com o intuito de otimizar a geração de metano e reduzir a concentração de poluentes das águas residuárias do processamento de café (ARC), o presente estudo teve como objetivos gerais: (i) Avaliar o desempenho de reatores anaeróbios de alta taxa e analisar a microbiota associada a este processo sob diferentes condições operacionais, e (ii) Comparar a eficiência de sistemas de pós-tratamento na remoção de nitrogênio (N), fósforo (P), sólidos e compostos fenólicos presentes nas ARC biodigeridas. Para o desenvolvimento do primeiro objetivo, foi empregado um sistema UASB em dois estágios, e uma série de três reatores anaeróbios horizontais de leito fixo (RAHLF). Os sistemas foram submetidos a diferentes cargas orgânicas volumétricas (COV), de até 18,2 g DQO (L d)-1 (UASB) e 9,5 g DQO (L d)-1 (RAHLF), e operados de forma continua com recirculação parcial do efluente obtido. Os maiores valores médios de produção volumétrica de metano foram de 2,0 e 1,9 L CH4 (L d)-1 para os reatores UASB e RAHLF, respectivamente. Em condições de alta COV, a análise metagenômica da microbiota associada ao reator UASB de melhor desempenho evidenciou prevalência dos gêneros bacterianos sintróficos Syntrophus e Candidatus Cloacimonas assim como de arqueias hidrogenotrôficas e acetotrôficas dos géneros Methanosaeta, Methanosarcina, Methanoculleus, Methanobacterium e Methanomassiliicoccus. Em relação ao sistema RAHLF, análises de reação em cadeia da polimerase quantitativa (qPCR) dos principais grupos methanogênicos associados ao lodo dos reatores indicaram predominância de arqueias acetotróficas correspondentes à ordem Methanosarcinales. Os dois sistemas proporcionaram condições favoráveis para a remoção da matéria orgânica com simultânea produção de energia. Para a execução do segundo objetivo, o pós-tratamento biológico foi realizado em um reator em batelada sequencial (RBS) utilizando um ciclo de 24 h dividido em 4 fases: alimentação, reação (anaeróbia/aeróbia/anóxica), sedimentação e descarte. Operado sob curtos períodos de enchimento, este sistema permitiu atingir altos níveis de remoção de N (80%) e P (71%), apresentando altas concentrações de bactérias nitrificantes e desnitrificantes. O pós-tratamento químico foi baseado na reação de Fenton, e apresentou maiores níveis de remoção de sólidos totais (83%) e compostos fenólicos (99%) quando comparado com o RBS. A recirculação parcial do efluente do processo Fenton melhorou o desempenho de reatores anaeróbios tratando ARC, constituindo uma alternativa de reuso promissora. O sistema integrado (RBS seguido do processo Fenton), demostrou ser a melhor alternativa para atingir padrões de lançamento e disposição final.
In order to optimize the methane production and to reduce the pollutant concentrations from coffee processing wastewater (CPW), this study aimed: (i) To evaluate the performance of high-rate anaerobic reactors and to analyze the microbiota associated to this process at different operational conditions, and (ii) To compare the removal efficiency of post-treatment systems regarding nitrogen (N), phosphorus (P), solids and phenolic compounds contained in biodigested CPW. For the development of the first objective, a two-stage UASB system and a series of three horizontal-flow anaerobic immobilized biomass reactors (HAIB) were employed. The systems were submitted to different organic loading rates (OLRs), up to 18.2 g COD (L d) -1 (UASB) and 9.5 g COD (L d) -1 (HAIB), and operated continuously with partial effluent recirculation. The highest mean values of methane production rate were 2.2 and 1.9 L CH4 (L d)-1 for UASB and HAIB reactors, respectively. Under high OLR, the metagenomic analysis of the microbiota associated to the UASB reactor showed a high prevalence of the syntrophic genera Syntrophus and Candidatus Cloacimonas, as well as the hydrogenotrophic and acetotrophic methanogens Methanosaeta, Methanosarcina, Methanoculleus, Methanobacterium and Methanomassiliicoccus. Concerning the HAIB system, quantitative polymerase chain reaction (qPCR) analyses of the main methanogenic groups associated to the reactor sludge indicated the predominance of acetotrophic methanogens, corresponding to the order Methanosarcinales. Both systems provided favorable conditions for organic matter removal with simultaneous energy production. To achieve the second objective, the biological post-treatment was performed in a sequential batch reactor (SBR), using a 24-h cycle divided in 4 phases: feeding, reaction (anaerobic/aerobic/ anoxic), settle and decant. Operated at short inlet flow mode, this system showed high removal levels of N (80%) and P (71%), showing high concentrations of nitrifying and denitrifying bacteria. The Fenton reaction was used as chemical posttreatment, showing higher removal levels of total solids (83%) and phenolic compounds (99%) in comparison with the SBR option. The performance of anaerobic reactors treating CPW was improved by partial Fenton effluent recirculation, with which this activity represented a promising reuse alternative. The integrated system (SBR followed by Fenton process) was effective to meet with the discharge standards.
In order to optimize the methane production and to reduce the pollutant concentrations from coffee processing wastewater (CPW), this study aimed: (i) To evaluate the performance of high-rate anaerobic reactors and to analyze the microbiota associated to this process at different operational conditions, and (ii) To compare the removal efficiency of post-treatment systems regarding nitrogen (N), phosphorus (P), solids and phenolic compounds contained in biodigested CPW. For the development of the first objective, a two-stage UASB system and a series of three horizontal-flow anaerobic immobilized biomass reactors (HAIB) were employed. The systems were submitted to different organic loading rates (OLRs), up to 18.2 g COD (L d) -1 (UASB) and 9.5 g COD (L d) -1 (HAIB), and operated continuously with partial effluent recirculation. The highest mean values of methane production rate were 2.2 and 1.9 L CH4 (L d)-1 for UASB and HAIB reactors, respectively. Under high OLR, the metagenomic analysis of the microbiota associated to the UASB reactor showed a high prevalence of the syntrophic genera Syntrophus and Candidatus Cloacimonas, as well as the hydrogenotrophic and acetotrophic methanogens Methanosaeta, Methanosarcina, Methanoculleus, Methanobacterium and Methanomassiliicoccus. Concerning the HAIB system, quantitative polymerase chain reaction (qPCR) analyses of the main methanogenic groups associated to the reactor sludge indicated the predominance of acetotrophic methanogens, corresponding to the order Methanosarcinales. Both systems provided favorable conditions for organic matter removal with simultaneous energy production. To achieve the second objective, the biological post-treatment was performed in a sequential batch reactor (SBR), using a 24-h cycle divided in 4 phases: feeding, reaction (anaerobic/aerobic/ anoxic), settle and decant. Operated at short inlet flow mode, this system showed high removal levels of N (80%) and P (71%), showing high concentrations of nitrifying and denitrifying bacteria. The Fenton reaction was used as chemical posttreatment, showing higher removal levels of total solids (83%) and phenolic compounds (99%) in comparison with the SBR option. The performance of anaerobic reactors treating CPW was improved by partial Fenton effluent recirculation, with which this activity represented a promising reuse alternative. The integrated system (SBR followed by Fenton process) was effective to meet with the discharge standards.
Descrição
Palavras-chave
Arquéias metagogências, Biogas, Reatores UASB em dois estágios, Reator anaeróbico horizontal de leito fixo, Remoção biológica de nutrientes, Processo Fenton