Pre-treatment of landfill leachate via coagulation-flocculation: Optimization of process parameters using response surface methodology (RSM)

Wastewater treatment is achieved mainly through the regeneration of resources and energy from wastewater, especially using pre-treatment technologies. In this study, coagulation pre-treatment of landfill leachate was performed using polymeric iron sulfate (PFS) as coagulation. Moreover, the whole experimental process was divided into two parts. In the first phase, the effects of PFS dosing, initial pH and PAM dosing on the removal of chemical oxygen demand (COD), total phosphorus (TP) and UV254 from the leachate were assessed using one factor one experiment (OFAT); In the second phase, the individual and interactive effects of parameters on COD %, TP%, and UV254% were evaluated using response surface methodology (RSM). Numerical multiple response optimization was conducted using RSM to maximize COD%. The COD%, TP%, and UV254% at optimum condition (PFS dose of 12.18 g/L, initial pH of 8.12, and PAM dosage of 11.29 mg/L) reached 62.30 %, 95.79 %, and 83.45 %, respectively. The 3D-EEM showed the effluent from the leachate after mixing. The chemical properties significantly changed, and the concentration of hard-to-degrade substances, such as humic acid, decreased. FTIR and ESM-EDX were used to delineate the intrinsic mechanism of contaminant removal, demonstrating that hydroxyl bonds are crucial in the extraction of leachate and the aggregation of folcs.