Ethanol addition as a strategy for start-up and acclimation of an AnSBBR for the treatment of landfill leachate

•COD removal efficiency over 70%, was obtained for landfill leachate in the AnSBBR.•Ethanol was used to activate, maintain and help biomass to acclimate to leachate.•Very low inhibition verified even with free ammonia concentration over 500 mgN L−1.

This study evaluated the ethanol addition as a strategy for start-up and acclimation of a pilot scale (1300 L) anaerobic sequencing batch biofilm reactor (AnSBBR) for the treatment of municipal landfill leachate with seasonal biodegradability variations. The treatment was carried out at ambient temperature (23.8 ± 2.1 °C) in the landfill area. In a first attempt, the leachate collected directly from landfill showed to be predominantly recalcitrant to anaerobic treatment and the acclimation was not possible. In a second attempt, adding ethanol to leachate, the reactor was successfully acclimated. After acclimation, without ethanol addition, the CODTotal influent ranged from 4970 to 13040 mg L−1 and the removal efficiencies ranged from 12.1% to 70.7%. A final test was carried out increasing the ammonia and free-ammonia concentration from 2486 mgN L−1 and 184 mgN L−1 to 4519 mgN L−1 and 634 mgN L−1, respectively, with no expressive inhibition verified. The start-up strategy was found to be feasible, providing the acclimation of the biomass in the AnSBBR, and maintaining the biomass active even when the leachate was recalcitrant.