Conversão anaeróbia de vinhaça e melaço em reatores UASB inoculados com lodo granulado

Neste trabalho avaliou-se a conversão anaeróbia da vinhaça e melaço em metano, com aumento gradual da carga orgânica volumétrica (COV), em dois reatores UASB (R1 e R2) com volumes de 40,5 e 21,5 L, na faixa de temperatura mesofílica. Os reatores UASB foram operados durante 350 dias, dos quais de 01 a 230 dias utilizou-se a vinhaça como afluente, de 231 a 308 dias o melaço de cana-de-açúcar e de 309 a 350 dias novamente a vinhaça. Os reatores foram operados com tempo de detenção hidráulica (TDH) de 2,8 e 1,8 d e COV de 0,2 a 11,5 g DQOtotal (L d)-1 no R1 e R2, respectivamente. Durante os primeiros 230 dias de operação, com vinhaça da safra de 2012, a produção volumétrica de metano foi crescente com o aumento da COV, atingindo valores de até 0,8 L CH4 (L d)-1 no R1 e de 1,3 L CH4 (L d)-1 no R2. Após 140 dias de operação com a correção de pH do afluente com solução de NaOH, a produção específica de metano foi crescente no R1 de 0,133 a 0,181 L CH4 (g DQOtotal removida)-1, e no R2, de 0,145 a 0,185 L CH4 (g DQOtotal removida)-1. Os valores médios das eficiências de remoção de DQOtotal variaram de 49 a 82%. As porcentagens da DQO removida convertida em metano foram de 48 a 58% no R1 e de 39 a 65 % no R2. A recirculação do efluente foi utilizada para a COV acima de 6 g DQOtotal (L d)-1 no R1 e de 8 g DQOtotal (L d)-1 no R2 e permitiu a manutenção do pH do afluente do R1 e do R2 na faixa de 6,5 a 6,8, mas provocou a diminuição das conversões de DQO em metano no R2, de 53% para 42%, em virtude do aumento da fração de DQO de difícil degradação no afluente. Após 230 dias de operação, com o tratamento do melaço no período de entressafra, a produção volumétrica de metano nos reatores R1 e R2 diminuiu para 0,294 e 0,163 L CH4 (L d)-1, respectivamente...The purpose of this study was to evaluate the anaerobic conversion of vinasse in methane, increasing gradually the organic load rate (OLR) on two UASB reactors (R1 and R2), each with a volume of 40.5 and 21.5 L in mesophilic temperature range. The UASB reactors were operated for 350 days, of which 01-230 days used the vinasse as affluent, 231-308 days, the molasses cane sugar and 309-350 dias again stillage. The reactors were operated with a hydraulic retention time (HRT) of 2.8 and 1.8 and OLR of 0.2 to 11.5 g total COD (L d)-1 in R1 and R2, respectively. During the first 230 days of operation, with vinasse from 2012 harvest, the volumetric methane production increased with the increase of OLR, reaching values of up to 0.8 L CH4 (L d)-1 in R1 and 1.3 L CH4 (L d)-1 in R2. After 140 days of operation with correcting the pH of the effluent with NaOH solution, the specific methane production in R1 was increased from 0.133 to 0.181 L CH4 (g CODtotal removed)-1, and R2, 0.145 to 0.185 L CH4 (g CODtotal removed)-1. The average values of totalCOD removal efficiencies ranged 49-82%. The percentages of removed COD converted to methane were between 48 and 58% in R1 and 39 to 65% in R2. The recirculation of the effluent was used for OLR above 6 g total COD (L d)-1 in R1 and 8 g of totalCOD (L d)-1 for R2 and allowed to maintain the pH of the effluent of R1 and R2 in the range from 6.5 to 6.8, but caused a decrease in methane conversion of COD in R2, 53% to 42% due to the increase of the fraction of COD influent degradation difficult. After 230 days of operation, with the treatment of molasses in the off-season, the volumetric methane production in the reactors R1 and R2 decreased to 0.294 and 0.163 L CH4 (L d)-1, respectively..

Biomethane production from vinasse in upflow anaerobic sludge blanket reactors inoculated with granular sludge

ABSTRACT The main objective of this study was to evaluate the anaerobic conversion of vinasse into biomethane with gradual increase in organic loading rate (OLR) in two upflow anaerobic sludge blanket (UASB) reactors, R1 and R2, with volumes of 40.5 and 21.5 L in the mesophilic temperature range. The UASB reactors were operated for 230 days with a hydraulic detection time (HDT) of 2.8 d (R1) and 2.8-1.8 d (R2). The OLR values applied in the reactors were 0.2-7.5 g totalCOD (L d)−1 in R1 and 0.2-11.5 g totalCOD (L d)−1 in R2. The average total chemical oxygen demand (totalCOD) removal efficiencies ranged from 49% to 82% and the average conversion efficiencies of the removed totalCOD into methane were 48-58% in R1 and 39-65% in R2. The effluent recirculation was used for an OLR above 6 g totalCOD (L d)−1 in R1 and 8 gtotalCOD (L d)−1 in R2 and was able to maintain the pH of the influent in R1 and R2 in the range from 6.5 to 6.8. However, this caused a decrease for 53-39% in the conversion efficiency of the removed totalCOD into methane in R2 because of the increase in the recalcitrant COD in the influent. The largest methane yield values were 0.181 and 0.185 (L) CH4 (gtotal COD removed)−1 in R1 and R2, respectively. These values were attained after 140 days of operation with an OLR of 5.0-7.5 g totalCOD (L d)−1 and total COD removal efficiencies around 70 and 80%