In this study, anaerobic co-digestion experiments for mixtures consisting of sewage sludge with food wastewater and livestock wastewater were conducted to assess the methane yields, the volatile solids (VS) removal rates and the dynamic kinetics. An augmented simplex centroid design (ASCD) was employed to design the mixing rate of organic wastes for the anaerobic co-digestion. Also, synergistic effects on the anaerobic co-digestion were studied using models obtained by the ASCD. As a result, synergistic effects were not observed in terms of methane yield and VS removal rate. It was just showed that there was a linear relationship between the cumulative methane yield and the mixing rate of food wastewater. The results might be attributable that the sewage sludge and the livestock wastewater had very lower C/N ratio compared with food wastewater that had a C/N ratio within a range required for a correctly operating anaerobic co-digestion. Therefore, increasing mixing rates of food wastewater increased the methane yield and VS removal rate, but there was not a synergistic effect by the anaerobic co-digestion.

The main objective of this experimental investigation was CH4 recovery from biogas generated in municipal and wastewater treatment plant. The polysulfone hollow fiber membrane was prepared in order to investigate the permeation properties of CH4 and CO2. Permeability of CO2 in Polysulfone membrane was 11-fold higher than of CH4 gas. A membrane pilot plant for upgrading biogas was constructed and operated at a municipal wastewater treatment plant. The raw biogas contained 66 ~ 68 Vol % CH4, the balance being mainly CO2. The effect of the operating pressure of feed and permeate side and feed flowrate on CH4 recovery concentration and efficiency were investigated with double stage membrane pilot plant. The CH4 concentration in the retentate stream was raised in these tests to 93 Vol % CH4.