Volatile fatty acid (VFA) and methane generation from sewage sludge and banana straw: Influence of pH and two-phase anaerobic fermentation

Abstract

Sewage sludge and banana straw were mixed for two-phase anaerobic fermentation while maintaining the pH of the acidogenic phase at 5.5, 6.5, 7.5, 8.5, 9.5, and 10.5. Under these conditions, batch tests were performed to investigate the effects of pH values on the production of volatile fatty acid (VFA) and methane from mixed fermentations. In the fermentation with acidogenic phase, the concentration of VFA in each experimental group reached its highest value on day 2, among which the highest VFA concentration was 7,592 mg L-1. The concentration of VFA in the range of acidity increased with increasing pH, while the range of alkalinity decreased. Cumulative yield and production speed of methane in alkaline experimental group was higher than that of the acid experimental group on day 20, and the maximum methane yield was observed in the 8.5 group, which was 280 mL g-1-VS.