Digestão anaeróbia de vinhaça em reatores UASB termofílicos, em série, com adição de Fe, Ni e Co
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Data
2017-07-20
Autores
Araujo, Daniele Medeiros de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho avaliou-se os efeitos da suplementação de ferro, níquel e cobalto na produção de metano da vinhaça proveniente da destilação do etanol de cana-de-açúcar, em reatores anaeróbios de fluxo ascendente com manta de lodo (UASB, R1 e R2) termofílicos, em série. Para determinar os efeitos da adição do Fe, Ni e Co, o experimento foi realizado em 3 diferentes fases. Na fase I foi realizada a partida dos reatores UASB, R1 e R2, com o aumento gradativo da carga orgânica volumétrica (COV) até valores de 9,4 g DQOtotal (L d)-1. Nas fases II e III a COV variou entre 9,9 a 14,9 g DQOtotal (L d)-1, e a fase III distinguiu-se da fase II pela suplementação com Fe, Ni e Co, na vinhaça afluente. Para o R1, a suplementação com elementos traço induziu ao decréscimo de ácidos voláteis totais, de 1801 para 834 mg L-1, aumento na produção volumétrica de metano (PVM) em 101% e aumento na eficiência remoção de DQO para 53%. O Fe foi considerado o principal elemento traço por seus efeitos de precipitação com sulfeto e participação nas fases acetogênicas e metanogênicas da digestão anaeróbia. As relações Fe/DQO, Ni/DQO e Co/DQO de 12,59, 0,138 e 0,191 mg (g DQOremovida)-1, respectivamente, foram consideradas ideais para o R1, pois, possibilitaram as mais altas PVM atingindo até 1,4 L CH4 (L d)-1. No sistema (R1+R2), a adição de Fe, Ni e Co promoveu estabilidade operacional, e auxiliou na remoção de DQO, melhorando a eficiência total do sistema. Porém, não favoreceu a PVM, que manteve-se com média 0,571 L CH4 (L d)-1 e foi semelhante a fase II, sem adição de elementos traço, com valores médios de 0,555 L CH4 (L d)-1. Portanto, verificou-se que com a suplementação de elementos traço, apenas o R1 seria suficiente, porém, para realizar o tratamento da vinhaça sem a suplementação de elementos traço, o R2 é essencial para a obtenção de metano, mas, sem garantia de estabilidade operacional para o sistema de digestão anaeróbio.
In this study was evaluated the effects of supplementation with iron, nickel and cobalt on vinasse in reactors upflow anaerobic sludge blanket (UASB, R1 and R2) thermophilic, in series. To determine the effects of the addition of trace elements, the experiment was conducted in 3 phases. During the first phase was characterized by the gradual increase of the organic loading rate (OLR) up to 9.4 g CODtotal (L d)-1, and start-up of system. In the phase II and III the OLR varied between 9.9 to 14.9 g CODtotal (L d)-1, the phase III distinguished of phase II only in trace element supplementation. For R1, trace element supplementation induced a decreased in total volatile acids, from 1801 to 834 mg L-1, increase in methane production rate (MPR) by 101% and increased in chemical oxygen demand (COD) removal efficiency to 53%. The Fe was considered the most relevant in the system due to its ability to precipitate with sulfide and participation in acetogenic and methanogenic phases of anaerobic digestion. The ratios Fe/COD, Ni/COD and Co/COD 12.59, 0.138, 0.191 mg g-1 CODremoved, respectively, they were considered ideal for R1, as they enabled as higher MPR reaching up to 1.4 L CH4 (L d)-1. For the system (R1+R2), the supplementation of Fe, Ni and Co promoted operational stability, and assisted in the removal of COD increasing the total efficiency of the system. However it did not favor the MPR, which remained on average of 0.571 L CH4 (L d)-1, and was similar to phase II, without addition of trace elements, with mean of 0.555 L CH4 (L d)-1. Therefore, it was verified that with the addition of trace elements, only R1 would be sufficient for the treatment of vinasse, but , if the treatment in chosen without the addition of trace elements, R2 would be essential for obtaining methane, but, without assurance of operational stability for the anaerobic digestion system.
In this study was evaluated the effects of supplementation with iron, nickel and cobalt on vinasse in reactors upflow anaerobic sludge blanket (UASB, R1 and R2) thermophilic, in series. To determine the effects of the addition of trace elements, the experiment was conducted in 3 phases. During the first phase was characterized by the gradual increase of the organic loading rate (OLR) up to 9.4 g CODtotal (L d)-1, and start-up of system. In the phase II and III the OLR varied between 9.9 to 14.9 g CODtotal (L d)-1, the phase III distinguished of phase II only in trace element supplementation. For R1, trace element supplementation induced a decreased in total volatile acids, from 1801 to 834 mg L-1, increase in methane production rate (MPR) by 101% and increased in chemical oxygen demand (COD) removal efficiency to 53%. The Fe was considered the most relevant in the system due to its ability to precipitate with sulfide and participation in acetogenic and methanogenic phases of anaerobic digestion. The ratios Fe/COD, Ni/COD and Co/COD 12.59, 0.138, 0.191 mg g-1 CODremoved, respectively, they were considered ideal for R1, as they enabled as higher MPR reaching up to 1.4 L CH4 (L d)-1. For the system (R1+R2), the supplementation of Fe, Ni and Co promoted operational stability, and assisted in the removal of COD increasing the total efficiency of the system. However it did not favor the MPR, which remained on average of 0.571 L CH4 (L d)-1, and was similar to phase II, without addition of trace elements, with mean of 0.555 L CH4 (L d)-1. Therefore, it was verified that with the addition of trace elements, only R1 would be sufficient for the treatment of vinasse, but , if the treatment in chosen without the addition of trace elements, R2 would be essential for obtaining methane, but, without assurance of operational stability for the anaerobic digestion system.
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Palavras-chave
Biogás, Reatores anaeróbios, Metano, Metanogênese, Micronutrientes, Biogas, Anaerobic reactors, Methane, Methanogeneses, Micronutrients