Factors affecting hydrogen production from cassava wastewater by a co-culture of anaerobic sludge and Rhodospirillum rubrum.

Series of batch experiments were used to investigate the effects of environmental factors, i.e., total nitrogen and total phosphorus concentrations, initial pH, illumination pattern and stirring conditions on hydrogen production from cassava wastewater by a co-culture of anaerobic sludge and Rhodospirillum rubrum. The maximum of the hydrogen yield of 150.46 and 340.19 mL g-COD(-1) was obtained at the total nitrogen and total phosphorus concentrations of 0.2 and 0.04 M, respectively. An effect of initial pH was investigated at COD:N:P ratio of 100:10:1. Results indicated that an optimum initial pH for hydrogen production was pH 7 with a high hydrogen yield of 158.78 mL g-COD(-1) was obtained. No significantly different (p < 0.05) in the effect of illumination pattern (24 h of light and 12 h dark/light cycle) on hydrogen production were observed under continuous-illumination and periodic-illumination with hydrogen yield of 131.84 and 126.92 mL g-COD(-1), respectively. Therefore, a periodic-illumination was applicable in hydrogen fermentation due to its cost-effective. Hydrogen fermentation with a stirring at 100 rpm provided more effective hydrogen production (164.83 mL g-COD(-1)) than static-fermentation (93.93 mL g-COD(-1)). The major soluble products from hydrogen fermentation were acetic and butyric acids, in the ranges of 28.33-48.30 and 35.23-66.07%, respectively, confirming an ability of a co-culture to produce hydrogen from cassava wastewater.