Comparison of Aerobic and Anaerobic Degradation of Municipal Solid Waste

摘要

Four laboratory-scale landfill reactors were set and operated with different modes as follows: landfill with forced aeration and leachate recirculation (A1), landfill with natural aeration only (A2), landfill with leachate recirculation only (B1), and landfill with no aeration and leachate recirculation (B2). For each reactor, landfill gas, solid waste and leachate were periodically sampled and physical, chemical and biological parameters were monitored as the indicators of MSW stabilization process. Concentrations of CH4, CO2 and O2 were monitored by using landfill gas analyzer. For solid waste, settlement ratio, moisture content (MC) and volatile solid (VS) were measured. Leachate indicators included pH, conductivity, chemical oxygen demand (COD), biological oxygen demand (BOD) and NH3-N. All parameters were analyzed by standardized methods. CH4 concentration in B1 was higher than B2, which indicated that leachate recirculation was helpful to CH4 production. The rank of settlement ratio from high to slow was A1 >A2>B1>B2. VS of A1 decreased about 50% during experiment period, compared with A2 and B1 25-35% and B2 a slight decreasing which can be ignored. COD and BOD of A1 decreased from the beginning of the experiment, and the ratio of BOD/COD decreased exponentially from 0.55 to 0.024 after 100 days. For A2 and B1, COD and BOD began to decrease significantly after 200 days. The difference was that decrease of BOD/COD of B1 was below 0.01 after 300 days, but A2 kept high level (about 0.3-0.4) of decrease all the time. For B2, there was no significant change in COD and BOD. As for NH3-N, only A1 eliminated it and it accumulated up to about 3000 mg/L in the other three reactors. The results showed that forced aeration with leachate recirculation considerably decreases MSW stabilization time compared to that in the other three modes. Leachate recirculation was more effective on anaerobic degradation of MSW than aerobic degradation. Natural aeration and leachate recirculation had similar effects on solid waste biodegradation, while leachate recirculation was more effective on leachate disposal and natural aeration was more effective on solid waste degradation.