Landfill leachate treatment using a combined method of coagulation, flocculation, advanced oxidation, and extended aeration

Background: Modifying and enhancing treatment methods is essential to meet effluent standards for treating landfill leachate. This study investigated the treatment of municipal solid waste leachate (MSWL) using coagulation, flocculation, advanced oxidation, and extended aeration processes. Methods: The effects of different coagulant doses and pH values on coagulation processes were compared. The treatment procedure was analyzed to determine the impact of varying concentrations of potassium persulfate (K2S2O8) and hydrogen peroxide (H2O2) on the results after coagulation with FeCl3. The extended aeration process’s biological stages were studied using a sludge retention time (SRT) of 23 days and the effects of hydraulic retention time (HRT) of 18 and 36 hours. Results: The experimental results show that in the pH range of 5–8, the lower the pH value, the higher the treatment efficiency. The addition of 0.8 g L^1− FeCl3 can achieve a 57% removal of chemical oxygen demand (COD). The addition of 2.5 g L^1− K2S2O8 and 1.5 g L^1− H2O2 with UV-C (15 W) for 70 minutes at pH 7 can effectively remove 86% of COD. Activated sludge extended aeration can attain an 88% removal of COD under optimal operating conditions (HRT = 36 hours, SRT = 23 days, and aeration = 36 hours). The studied hybrid process with the efficiency of 99%, 98%, 95%, 87%, and 83% removal of COD, biochemical oxygen demand (BOD), total suspended solids (TSS), turbidity, and total Kjeldahl nitrogen (TKN), respectively, is suitable for leachate treatment. Conclusion: This study showed that flocculation-coagulation followed by the advanced oxidation process (AOP) and extended aeration can be an efficient and promising treatment method for MSWL.