Collapse, explosion and water pollution by leachate have been three major problems in confining the development of sanitary landfilling technology as an economical method for disposal of municipal refuse. Potential risk factors including settlement of landfilled refuse, the generation of methane, carbon dioxide and other gases from landfill, the dynamic changes in temperature within the landfill and its ambient environment, as well as COD(Cr), BOD5, nutrients (TKN, TP and organic matter), heavy metals (Cu, Pb and Zn) and pH in landfill leachate were simulated using a reactor with high water input. It was indicated that high content of organic components in landfilled refuse is a key risk factor to cause abrupt collapse and accidental explosion in the landfill because they have impact not only on the settlement, but also on the release of methane and other gases. Elevated temperatures coincided with maximum generation of methane and other gases, thus increasing the risk of accidental explosion. Leachate quality was closely related with the release of COD(Cr) and BOD5 and heavy metals such as Cu, Pb and Zn, as well as organic pollutants, there was less release of TKN and TP. The mass balance analysis for the reactor showed that 36% of organic carbon reduction in the refuse during the simulations was discharged into leachate as soluble organic carbon, and 3% was converted to methane and carbon dioxide as gas production. Mixing of refuse with soil and sand particles, the so-called drill-a-hole method and recycling leachate were measures suggested in order to mitigate and avoid potential accidents.