Abstract
The long-term effect of nutrient supplementation of cassava-processing wastewater on biohydrogen production by a mixed culture has been assessed. An anaerobic sequential batch reactor (ASBR) was operated for 120 d and fed with cassava wastewater, without nutrient supplementation during the first 65 d, and with nutrient addition between days 66 and 120. The specific hydrogen production rate and the hydrogen yield obtained by feeding the bioreactor with cassava wastewater without supplementation were 44.6 mLH2/gVSS.d and 323 mL H2/g COD, respectively. However, nutrient addition favored nonspecific microbial growth, which culminated in a decreased specific hydrogen production of 23.1 mLH2/gVSS.d, with a hydrogen yield of 153.5 mL H2/g COD. During the final 35 d of operation, gas production was largely inhibited, attributed to increased growth of lactic acid bacteria, as evidenced by the presence of a high concentration (1.25 g/L) of LA in the reactor during this period.
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