INFLUENCE OF HIGHER ORGANIC LOADING RATES ON THE EFFICIENCY OF AN ANAEROBIC HYBRID DIGESTER WHILE TREATING LANDFILL LEACHATE

An anaerobic hybrid laboratory-scale digester was used to evaluate the treatment efficiency when using high strength landfill leachate at or ganic loading rates (OLR) of more than 20 kg COD m(3).d(-1). The diges ter was operated at mesophilic temperatures and the hydraulic retentio n kept constant at 1,0 d. It was found that the digester can be used s uccessfully to treat landfill leachate at higher OLRs and should be ab le to withstand loading shocks within specific values. The data showed that at an OLR of > 24 kg COD.m(3).d(-1), a total COD removal of 88% can be obtained with a CH4, yield of 0,237 m(3).kg(-1) COD removed. At an OLR of 26,05 kg COD.m(-3).d(-1) the hybrid digester could reduce t he COD of the leachate by 95% and more than 80% at a loading rate of 2 9,0 kg COD m(3).d(-1) . The methane content of the biogas varied betwe en 64% and 74%. Total methane yields per COD removed ranged between 0, 215 and 0,230 m(3).kg(-1) COD at OLRs of 26,05 and 29,0 kg m(-3).d(-1) respectively. The poor propionic acid removal of 68% at COD concentra tions of 29,0 kg COD m(-3).d(-1) appeared to be an indication of diges ter overloading and impending digester failure.