Biological pretreatment of municipal solid waste prior to landfilling

Abstract

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 BOD5, COD, NH4-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, COD5 and NH4-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.