Biogas recovery from fresh landfill leachates by using a coupled air stripping-up follow anaerobic sludge blanket (UASB) process

Abstract

The present study focuses on fresh leachates treatment using anaerobic digestion. To overcome the unsuitable raw characteristics, appropriate pretreatment conditions were identified based on Batch tests. A subsequently optimized pretreatment-anaerobic two stages UASB coupled treatment was studied. The performance of the overall coupled treatment was assessed by monitoring volatile fatty acids (VFA), COD and ammonium removal, and biogas performance. Results showed that combining acidity correction to short aeration gives a synergetic effect and allowed appropriate anaerobic start-up conditions. Under continuous aerobic pretreatment-UASB digestion, significant removal of NH+4 (75.87%), COD (19.14%), and VFA (20.3%) were achieved during the aeration step resulting in the total abatement of 88.66%, 83.6% and 70.39% for NH+4, COD, and VFA, respectively. The process allowed good biogas performance up to 2,470 mL biogas/L and 123 mL CH4/gCOD removed, with gradual improvement from the first to the second UASB reactor. Inlet COD and VFA feeding rate seemed to be the main key parameters with 45.37 g COD/L.d and 18.43 g VFA/L.d as a critical threshold. Therefore, the anaerobic digestion of high COD leachates is highly feasible and the aerobic–anaerobic coupled treatment is a promising technical scenario that deserves further studies.