Influence of pH on biogas production in a batch anaerobic process of tofu wastewater

Abstract

As a popular soybean-based food in Indonesia, tofu production might cause a potential environmental problem, especially to the water body around the tofu industries. Approximately 17-45 tonnes of tofu wastewater are generated for every tonne of soybean used. The wastewater has a high organic concentration at pH of 3.5-4.5. Anaerobic digestion not only could be an efficient method to treat wastewater with high organic content, but also it produces less sludge and generate biogas as a renewable energy source. Anaerobic microorganisms normally work well in neutral pH. By pH lower than 5 the metabolism of methanogenic community could be easily hampered. The objective of this research was to test the influence of pH on anaerobic digestion of tofu wastewater. The experiments were performed in a batch mode using tofu whey waste water indigenous at pH 3.7 and neutralized wastewater at pH 7 Concentrations were varied at 20, 50, and 100% wastewater. Our results showed that at low pH of tofu wastewater did not have a negative influence on anaerobic digestion of tofu wastewater in a batch mode. A further addition of wastewater into the reactor (batch-wise) also showed a similar trend. It suggests that the presence of adequate buffer capacity was more important than adjustment of wastewater pH.