Long-term emissions from mechanically biologically treated waste: Influence on leachate quality

Long-term emissions from municipal solid waste landfills can be reduced by mechanical-biological treatment (MBT) of waste prior to disposal. The pretreatment accelerates waste degradation resulting in a reduction of the landfill’s polluting potential. This study reports on the applicability and efficiency of MBT in Durban, South Africa. Waste treatment in passively aerated open windrows, using the Dome Aeration Technology (DAT), was identified as an appropriate technology due to low construc-tion and operational resource requirements. Three self-aerated windrows were set up at the Bisasar Road Landfill in order to study the efficiency of the process for different composting timeframes (8 and 20 weeks). The ’post-landfilled ‘ behaviour of the pretreated material was analysed in anaerobic lysimeters. The effect of different degrees of degradation was studied in relation to waste composition and rate of irrigation. The lysimeter tests demonstrated that the initial acidic inhibition that is characteristic of waste with high organic content can be eliminated through pretreatment. Notwithstanding the rapid onset of methanogenesis, high COD concentrations of non-degradable organics in the leachate remain after 200 d of testing. Despite the high COD levels, a clear benefit of waste pretreatment is the low concentration of ammoniacal nitrogen after only 8 weeks of composting. The results of this research can be used to define a framework for sustainable waste disposal, particularly in relation to the subtropical climatic conditions experienced in Durban, resource availability and waste composition