BIOLOGICAL PRETREATMENT OF MUNICIPAL SOLID WASTE PRIOR TO LANDFILLING

The conventional landfilling does not promote sustainable waste management due to uncontrolled emissions which potentially degrade the environment. In this regard, pre-treatment of municipal solid waste prior to landfilling significantly enhance waste stabilization and provides various advantages. So in this regard pre-treatment methods of municipal solid waste were investigated. The major objectives of biological pretreatment are to degrade most easily degradable organic matters of MSW in a short duration under controlled conditions so as to produce desired quality for landfill; and to enhance methanogenic condition in the landfill. Factors affecting the choice of pretreatment processes include the composition of MSW, retention times, odor emissions, fate of toxic chemicals and costs. To investigate the economical pretreatment method prior to landfilling for developing countries four pretreatment simulators were developed at bench scale in the laboratory at different operating conditions forced aeration and leachate recirculation (APSFALR), aerobic pretreatment simulator by natural convection of air with leachate recirculation (APSNCLR), aerobic pretreatment simulator by natural convection of air (APSNC) and anaerobic simulator (AS). The organic matter, pH, temperature, settlement, leachate quantity and quality were monitored regularly. In the leachate quality BOD(5), COD, NH(4)-N, pH and trace metals were analyzed. The molecular size distribution of dissolved organic matters (DOM) in leachate was determined after the pretreatment of 45 days. The results of these methods are compared. The APSNCLR method is economically effective method to reduce the organic matters, leachate COD and BOD5. With the biological pretreatment significant amount of easily biodegradable matters and volume of solids are reduced due to the decomposition of the waste. Landfilling of pretreated waste improves landfill behavior, characteristics, and operation. Leachate quantity, quality and landfill gas emissions also would be reduced. It is predicted by the comparison of carbon content in the fresh and pretreated MSW that resultantly increases the landfill age and decreases in aftercare monitoring period. The volumes of the solids were reduced and density increased significantly in eight weeks pretreatment of MSW due to biodegradation of organic matters. The BOD, COD(5) and NH(4)-N content also reduced significantly as compared to the anaerobic simulator. Pretreatment simulators results are compared and concluded that pretreatment with passive aeration and leachate recirculation is better as compared to the other pretreatment simulators.