Multi-barrier treatment of mature landfill leachate: Effect of Fenton oxidation and air stripping on activated sludge process and cost analysis

A multi-barrier approach including advanced oxidation by Fenton (FO), air stripping (AS) and biological activated sludge (B-AS) processes was investigated as possible treatment of mature landfill leachate (MLL) in an urban wastewater treatment plant (UWTP). Three different conditions were compared to the control line (B-AS treatment of simulated urban wastewater (SWW)): MLL pre-treated with FO process and diluted to 17% with SWW; MLL pre-treated with AS and diluted to 17% with SWW; MLL pre-treated with FO, AS and diluted to 17% with SWW. Preliminary tests aimed to investigate the best operating conditions of FO for MLL (pH = 3, t = 120 min, H2O2/Fe2+ = 1, H2O2= Fe2+ = 3500 mg/L) were carried out with regard to COD removal (82%) and biodegradability (BOD5/COD = 0.32). FO and AS were very efficient to remove COD (82%) and NH3 (92%) respectively, before pre-treated MLL was mixed to SWW. The multi-barrier treatment (FO + AS + B-AS) was very efficient to remove COD (85%) and NH3 (79%). Furthermore, the absence of one of the two pre-treatments, FO or AS, adversely affected the biological process, by reducing COD (47%) and NH3 (14%) removal efficiency, respectively. The management cost analysis showed that the investigated multi barrier system is economically feasible only at low dilution ratio between FO-AS pre-treated MLL and real urban wastewater (<3% under the investigated conditions).