Efficiency of a biological aerated filter for the treatment of leachate produced at a landfill receiving non-recyclable waste

The feasibility of a biological aerated filter for the treatment of a partially stabilized leachate from a landfill receiving non-recyclable wastes was assessed in laboratory-scale experiments. Maximum COD, BOD5 and TSS removal efficiencies achievable by the biofilter as well as the optimal hydraulic and organic loading rates were determined by laboratory-scale tests in batch and continuous mode. Experiments in batch mode which lasted for 7 days showed that COD and BOD5 removal efficiencies were stabilized after the second day of operation and kept at around 56-60% and 83-97%, respectively, for the rest of the period studied. The remaining fraction (approximately 40% of the COD) was found to be composed of recalcitrant or not easily biodegradable compounds. The COD and BOD5 removal efficiencies decreased with increasing hydraulic loading rates. The plant worked under optimal conditions at hydraulic loading rates of 0.71 and 1.41 m(3)/m(2)d (hydraulic retention times of 15.95 and 7.97 h, respectively) and at COD loading rates below 14 kg COD/m(3), where COD removal efficiencies were around 60%. TSS removal efficiencies were not significantly influenced by the hydraulic loading rate. The results obtained demonstrated the feasibility of a biological aerated filter for the removal of the biodegradable fraction of the organic matter contained in the leachate. However, a physicochemical process was found to be necessary as pre- or post-treatment for the removal of the recalcitrant fraction.