The mesophilic anaerobic co-digestion of sewage sludge and landfill leachate

The feasibility of co-digesting landfill leachate and sewage sludge at the North End Water Pollution Control Centre (NEWPCC) of the City of Winnipeg was investigated. Three reactors were operated in semi-continuous feed mode under steady-state conditions for two months in the summer of 2001, and for three months in the winter of 2001. While one reactor remained as a control reactor (retention time of 16 days), receiving only sludge, the other two received various concentrations of leachate in addition to the same sludge volume as the control reactors.; Leachate addition resulting in retention times of 15 and 14.3 days resulted in a slight increase on average effluent volatile solids from 11.7 to 12.2 and 12.4 kg/m3, respectively. Volatile solids destruction increased from 46.1 percent to 48.6 and 49.0 percent.; A further increase in leachate addition resulting in retention times of 13.3 days increased the methane production efficiency from 0.80 to 0.87 m3 per kg of VS destroyed. A further increase resulting in a retention time of 12.8 days resulted in a decrease to 0.81 m3/kg of VS destroyed. No increase in total methane production was observed at retention times of 13.3 and 12.8 days; due to a decrease in volatile solids destruction with increasing leachate addition.; Co-digestion of leachate and sewage sludge was shown to have no negative impact on methane production at a retention time of 14.3 days, but was shown to reduce methane production by up to eight percent when the retention time was reduced to 12.8 days. Thus, it was determined that co-digestion is a feasible leachate treatment method in quantities not reducing retention times below 14.3 days, which corresponds to a leachate addition by volume of seven percent.