Mechanical biological pretreatment processes are increasingly being employed as a means of diverting bio-degradable municipal waste from landfill to comply with the EU Landfill Directive. This will have major implications for the nature of the waste that is disposed of to landfills and hence for the way in which the landfills should be managed. The long-term behaviour of mechanically biologically treated (MBT) waste will be different from that of unprocessed municipal solid waste since the pretreatment process may change its physical, chemical and biological properties. To investigate the impact of the level of pretreatment, large-scale laboratory experiments were carried out on MBT wastes treated to typical UK and German standards. Gas generating potential, leachate quality, settlement characteristics and hydraulic properties of MBT wastes were determined and compared. The research has demonstrated the benefits of pretreatment in substantially reduc-ing the gas generating potential, releasing low levels of total organic carbon and ammoniacal nitrogen and, reducing the long-term settlements due to creep and biodegradation. Data from both MBT wastes followed the same general trend of decreasing hydraulic conductivity and drainable porosity with increasing stress and waste density.
Biogas, hydraulic conductivity, landfi ll, leachate, municipal solid waste,porosity, pretreatment
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