Codisposal of municipal refuse, sewage sludge and marine dredgings for methane production

As marine disposal of sewage sludge and dredged sediments may impose seriou s adverse effects to marine ecosystems, landfilling seems to be the most fe asible method for the final disposal of these wastes. A batch experiment wa s conducted to study waste degradation and gas production after sewage slud ge and marine dredgings were mixed with municipal refuse at 13 different ra tios for 36 days. The addition of sludge and dredgings to municipal refuse enhanced gas production, compared with the degradation of refuse or sludge alone. A proper mixing ratio of wastes can also shorten the time to reach t he final phase of anaerobiosis. The highest gas production was obtained fro m the ratio of 75-20-5 (refuse-sludge-dredgings) (wet weight basis). Its av erage daily gas production rate was 1.42 1 kg(-1) waste mixture; methane co ntent was 68.3%. The results indicated that codisposal of the three wastes would be beneficial for energy recovery from landfill gas. (C) 1999 Elsevie r Science Ltd. All rights reserved.