ANAEROBIC CO-DIGESTION OF SEWAGE SLUDGE AND GROUND GRASS

Abstract

 Anaerobic co-digestion of sewage sludge and ground grass from a riverbed was investigated. We conducted experiments using laboratory-scale and pilot-scale digesters.
 Laboratory-scale experiment was conducted under the condition that the mixture ratio of sewage sludge and grass was 1:0.5 based on TS. The grass was ground to about 2-3 mm in length in pretreatment. This pretreatment got methane conversion efficiency of grass to be almost parallel to that of the sewage sludge. Degradability of grass co-digested with sewage sludge was the same level between those of other two wastewater treatment plants.
 Pilot-scale experiment was conducted in 500L digesters under the same condition of the mixture ratio. The operation was satisfactory and the specific biogas production (SBP) of the grass was 384 NL/kg-VS. This value of SBP was the same level to that of previous study for rice straw pretreated by grinding plus soaking in an enzyme solution.