The effect of precipitation on municipal solid waste decomposition and methane production in simulated landfill bioreactor with leachate recirculation

Abstract

The objective of this study is to investigate MSW degradation and methane production in a simulated landfill bioreactor with leachate recirculation under conditions with and without water addition at the representative level of annual precipitation. Experiments were carried out in four simulated reactors using 0.3 m diameter PVC pipe of 1.25 m height. Two leachate recirculation reactors were operated with water addition and the other two were operated without water addition. The results showed that leachate recirculation with precipitation led to greater performance in terms of accelerated biological stabilization and the onset of methanogenesis. In the reactors operated with precipitation, the reduction of COD was 24-54 times higher than that in reactors without precipitation. The percentage of waste decomposition was 59.0-61.4% and the methane production rate was 0.479-0.638 l/kg dry waste/day at the stabilization phase in the reactors operated with precipitation. Conversely, 19.6-22.4% of waste decomposition and 0.01 l/kg dry waste of methane production were found in reactors operated without precipitation. In this experiment, the feasibility of introducing moisture only by leachate recirculation, with no precipitation, seemed to be unsuitable for recirculation due to the high concentration of leachate pollutant. A large quantity of buffering chemical was used. Therefore, during the hydrolysis and acidogenesis phases, precipitation or water added was important for the waste decomposition as to dilute and flush out high TVA concentration and create a favorable environment for methanogenesis.

Keywords

• landfill
• leachate recirculation
• bioreactor
• precipitation