Performance of UASB reactors in two stages followed by post-treatment with activated sludge in wastewater batch of wet-processed coffee

Abstract

In this study it was evaluated the efficiency of the treatment of wet-processed coffee wastewater in upflow anaerobic sludge blanket (UASB) reactors in two stages, in bench scale, followed by post-treatment with activated sludge in batch. The first UASB reactor was submitted to an hydraulic retention time (HRT) of 6.2 d and organic loading rates (OLR) of 2.3 and 4.5g CODtotal (L d)-1, and the second UASB reactor to HRT of 3.1 d with OLR of 0.4 and 1.4g CODtotal (L d)-1. The average values of the affluent CODtotal increased from 13,891 to 27,926mg L-1 and the average efficiencies of removal of the CODtotal decreased from 95 to 91%, respectively, in the UASB reactors in two stages. The volumetric methane production increased from 0.274 to 0.323L CH4 (L reactor d)-1 with increment in the OLR. The average concentrations of total phenols in the affluent were of 48 and 163mg L-1, and the removal efficiencies in the UASB reactors in two stages of 92 and 90%, respectively, and increased to 97% with post-treatment. The average values of the removal efficiencies of total nitrogen and phosphorus were of 57 to 80% and 44 to 60%, respectively, in the UASB reactors in two stages and increased to 91 and 84% with the post-treatment.

Neste trabalho, avaliou-se a eficiência do tratamento de águas residuárias do beneficiamento de café por via úmida em reatores anaeróbios de fluxo ascendente com manta de lodo (UASB), em dois estágios, em escala de bancada, seguidos de pós-tratamento com lodos ativados em batelada. O primeiro reator UASB foi submetido a tempo de detenção hidráulica (TDH) de 6,2 d e a cargas orgânicas volumétricas (COV) de 2,3 e 4,5 g DQOtotal (L d)-1, e o segundo reator UASB a TDH de 3,1 d e a COV de 0,4 e 1,4 g DQOtotal (L d)-1. Os valores médios de DQOtotal do afluente aumentaram de 13.891 para 27.926 mg L-1, e as eficiências médias de remoção de DQOtotal diminuíram de 95 para 91%, respectivamente, nos reatores UASB, em dois estágios. A produção volumétrica de metano aumentou de 0,274 para 0,323 L CH4 (L reator d)-1com o acréscimo na COV. As concentrações médias de fenóis totais no afluente foram de 48 e 163 mg L-1, e as eficiências médias de remoção nos reatores UASB em dois estágios, de 92 e 90%, respectivamente, e aumentaram para 97% com o pós-tratamento. As eficiências médias de remoção de nitrogênio e fósforo total variaram, respectivamente, de 57 a 80% e de 44 a 60% nos reatores UASB em dois estágios e aumentaram para 91 e 84% com a inclusão do pós-tratamento.