Performance of coagulation-flocculation followed by ultra-violet/ultrasound activated persulfate/hydrogen peroxide for landfill leachate treatment

Abstract

The advanced oxidation processes (AOPs) were assessed for enhancing the treatment of stabilized landfill leachate previously pretreated using coagulation-flocculation (C-F).The primary treatment by C-F using 20 g.L−1 of FeCl3 (optimal coagulant dosage) has removed 71% of chemical oxidation demand (COD) and 95% of turbidity. Thereafter, secondary treatment was applied using different system combinations of two inorganic oxidants (potassium persulfate, K2S2O8 (PS) (1500 mg. L−1) and hydrogen peroxide, H2O2 (1327 mg. L−1)) that were used simultaneously or separately with UV-A and/or ultrasonic (US) irradiations.The obtained results indicated that the oxidation systems with the presence of H2O2 were more efficient than other systems. Indeed, the H2O2-PS-US-UV-A system reached the highest COD removal of 89%, while PS-based combinations were the less efficient (PS alone 19%, PS-UV-A 22%, PS-US 32%, and PS-US-UV-A 35%).Hence, the sequential process including C-F as pretreatment followed by the application of the H2O2-PS-US-UV-A system has proven high efficiency for COD removal, absorbance at 254 nm, and color number of 97%, 97%, and 99%, respectively.The sequential application of AOPs after preliminary treatment using coagulation-flocculation is a promising alternative to reducing the high organic load of stabilized leachate and that could be largely applied to other types of effluents.