Methane recovery from acidic tofu wastewater using an anaerobic fixed-bed reactor with bamboo as the biofilm carrier

Wastewater generated during acid coagulation in tofu processing has high organic concentrations and low pH. Several small industries in Indonesia discharge such wastewater without treatment, necessitating economical treatment to control water pollution. In this study, the feasibility of methane production from the treatment of acidic tofu processing wastewater was investigated. For this, anaerobic treatment of tofu processing wastewater using a fixed-bed reactor employing cut bamboo as the carrier was examined and compared to an upflow anaerobic sludge blanket reactor. Without neutralization, the fixed-bed reactor outperformed the upflow anaerobic sludge blanket reactor at a chemical oxygen demand load of 4.3 kg chemical oxygen demand/m³ day. The highest total organic carbon removal efficiency and methane gas yield were 95% and 0.98 L/g total organic carbon removed, respectively. The two most abundant bacteria were the genus Paludibacter and the unclassified Bacteriodetes; both from the family Porphyromonadaceae. Hydrogenotrophic methanogens from the genera Methanoculleus and Methanobacterium were the dominant archaea, indicating that hydrogenotrophic methanogenesis was a major methane formation pathway.