Possible interactions between recirculated landfill leachate and the stabilized organic fraction of municipal solid waste

The stabilized organic fraction of municipal solid waste (SOFMSW) is a product of the mechanical/biological treatment (MBT) ofmixed municipal solid waste (MMSW). SOFMSW is considered a ‘grey’ compost and the presence of pollutants (particularly heavymetals) and residual glass and plastic normally prevents agricultural use, making landfills the typical final destination for SOFMSW.Recirculation of leachate in landfills can be a cost-effective management option, but the long-term sustainability of such a practicemust be verified. Column tests were carried out to examine the effect of SOFMSW on leachate recirculation. The results indicatethat organic matter may be biologically degraded and metals (copper and zinc) are effectively entrapped through a combination ofphysical (adsorption), biological (bacterial sulfate reduction), and chemical (precipitation of metal sulfides) processes, while otherchemicals (i.e. ammonia nitrogen and chloride) are essentially unaffected by filtration through SOFMSW.