The basic purpose of operating landfills as bioreactors is to enhance the waste degradation and to stabilise the waste in shorter time period as compared to conventional dry tomb landfills. This paper presents an overview of bioreactor landfills in terms of various factors affecting stabilisation of municipal solid waste. Moisture is considered to play a critical role in the biodegradation of the waste. Leachate recirculation and/or water addition is used to optimise the moisture content in the bioreactor landfills. In addition to moisture, other environmental factors that significantly influence the rate of degradation of waste in the landfills are pH, temperature, nutrients/activated sludge addition, buffer/alkalinity addition, level of toxins/inhibitors, particle size, oxidation–reduction potential, aerobic/anaerobic conditions, nature of recirculated leachate, volume/frequency of recirculated leachate and composition/compaction density of waste. All the above stated parameters are discussed in the paper. The review could be of help to better understand and control these parameters to increase rate of decomposition of waste in the landfills and ultimately to optimise the various parameters for successful operation of bioreactor landfills.
Keywords: municipal solid waste, MSW, bioreactor landfills, leachate recirculation, biodegradation, stabilisation, moisture content, decomposition rate