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

Abstract

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 m³/m²d (hydraulic retention times of 15.95 and 7.97 h, respectively) and at COD loading rates below 14 kg COD/m³, 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.

Keywords:

• Landfill leachate treatment
• partially stabilized leachate
• biological aerated filter
• non recyclable wastes
• hydraulic load
• organic load
• COD removal.

Acknowledgments

We are grateful to Fomento de Construcciones y Contratas S.A. (FCC) for allowing the collection of leachate samples from the Alhendín landfill site. The study was partially funded by the Spanish Ministry of Science and Technology (Project FIT-050000-2002-74). The work was supported by a Fellowship funded by the Spanish Ministry of Science and Education.