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.