Biogas generation from liquid waste of beneng taro starch processing: The effect of initial pH

The starch extraction process from Beneng taro generates a substantial amount of liquid waste, characterized by high concentrations of organic compounds.Because of its chemical oxygen demand (COD), the Beneng taro starch processing wastewater (BTSPW) is not permitted to be discharged directly to the environment.Anaerobic digestion (AD) is proposed to be applied to convert COD in the BTSPW to biogas.The aim of the current research was to examine the influence of initial pH on the AD performance in converting BTSPW to biogas.The initial pHs varied to 5.7 (control), 6.5, 7.0, 7.5, and 8.0.The substrate to inoculum ratio was 80:20%v/v.The results revealed that initial pHs of 5.7, 6.5, 7.0, 7.5, and 8.0 generated total biogas yields of 61.8, 113.62, 132.3, 103.0, and 52.1 mL/g-COD added , respectively.Then, initial pHs of 5.7, 6.5, 7.0, 7.5, and 8.0 resulted in COD removals of 36.12,39.85, 40.58, 36.86, and 36.78%,respectively.Furthermore, initial pHs of 5.7, 6.5, 7.0, 7.5, and 8.0 resulted in total solid (TS) removals of 17, 28, 32, 24, and 13%, respectively.Hence, the optimal initial pH in AD of BTSPW is 7.0.Through the modified Gompertz model, the initial pH of 7.0 had the highest P m value (140.28 mL/g-COD added ) and the lowest λ value (3.79 days).The results of this study are in line with the hypothesis.