PubMed2003
The feasibility of mesophilic anaerobic co-digestion of landfill leachate and sewage sludge was examined in a bench-scale experiment. Three complete-mix, flow-through digesters were operated in a semi-continuous mode. During both phases of research all digesters received 500 ml d(-1) of raw sludge and Reactor 1 was always the control reactor--fed sludge only. During Phase 1, leachate volumes less than 12% of the sludge volume were fed to Reactors 2 and 3. During Phase 2 larger amounts of leachate were added, exceeding 20% of sludge volume which led to an overall decrease in the hydraulic residence time of the digesters. All reactors achieved stable operation, which indicated that the co-digestion of sewage sludge and landfill leachate is feasible During Phase 1, an increase in the average daily methane production from 2.5 l d(-1) to 3.1 l d(-1) and 3.2 l d(-1) was observed; the biomethanation production (BMP) increased from 0.46 to 0.6 m3 - 0.7 m3 CH4 (kg VS rem.)(-1). The average volatile solids reduction (VSR) increased from 46.1% to 48.6% and 49.0%. In Phase 2, the total methane production in the control reactor was significantly higher, at 4.6 l d(-1), while the addition of larger, by volume, amounts of leachate, decreased the methane production to 4.3 l d(-1) and 4.2 l d(-1), respectively. The average BMP values were 0.8, 0.87, and 0.81 m3 CH4 (kg VS rem.)(-1), respectively. In Phase 2, leachate addition decreased the average VSR from 51% to 49% and 45.6%. After calculating that leachate addition to digesters would not increase heavy metal concentrations in the produced biosolids it was concluded that mesophilic anaerobic co-digestion of sewage sludge and landfill leachate is feasible, and provides a promising alternative to aerobic co-treatment.