Anaerobic Digestion of Industrial Tempeh Wastewater with Sludge from Cow Manure Biogas Digester as Inoculum: Effect of F/M Ratio on the Methane Production

Abstract

Industrial tempeh wastewater contains high organic compounds that will negatively affect the water ecosystem's quality whenever discharged without proper treatments. Biological treatment, in particular, anaerobic digestion, is the potential to be an effective solution for eliminating that contaminant. Considering its advantages, especially to produce methane gas, a study to evaluate the anaerobic digestion process's performance to reduce the organic substances in industrial tempeh wastewater was conducted. Sludge from cow manure biogas digester was used as inoculum to foster an anaerobic decomposition process. Hence the particular focus was given to elaborate the effect of F/M ratio on methane production. With a practical volume of 4L each, controlled batch reactors were employed with several operational parameters (pH, COD, VFAs) to be monitored to understand the process. Results elucidated that methane production was closely related to the composition of the substrate to microorganism. The maximum methane production (8720 mL) followed by the highest organic reduction (67.7%) were found in F/M = 1.12. The measured operational parameters informed a sequence of the process involved in the complete anaerobic decomposition. Accumulation of VFAs, because of higher substrate loading, tended to hamper methanogens metabolism resulted in low methane production. In addition to that, inoculum from biogas digester of cow manure was proved to play a significant role in the anaerobic decomposition for industrial tempeh wastewater. This finding is essential for arranging an effective yet low-cost wastewater treatment for tempeh producers, which is a basis for further study.