Cheese wastewater treatment through combined Coagulation-Flocculation and Photo-Fenton-like advanced oxidation processes for reuse in irrigation: Effect of Operational Parameters and Phytotoxicity assessment

Abstract

Abstract The present study aims to investigate the efficiency of a combined cheese wastewater treatment approach involving coagulation with ferric chloride coupled with a Photo-Fenton-like oxidation process for potential reuse in irrigation. Laboratory-scale tests were conducted, examining the influence of various operational parameters on the treatment process. Specifically, the effects of initial wastewater pH, coagulant dosage, decantation time for the coagulation process, and initial pH, chemical oxygen demand (COD) concentration, Fe3+ and H2O2 dosages for Photo-Fenton-like oxidation were studied. Coagulation was found effective at natural pH of 6 and showed a highest removal efficiency in terms of COD (50.6%), biological oxygen demand BOD5 (42.1%), turbidity (99.3%), and least sludge volume generation (11.8% v/v) for an optimum coagulant dose of 400 mg Fe3+ L–1 and 8 hours of decantation time. Thereafter, the sequential treatment of cheese wastewater based on coagulation as a pre-treatment process and then Photo-Fenton-like oxidation (Fe3+/H2O2/UVA-300W), enhanced the removal of COD, BOD5 and total organic carbon (TOC) to 91.2%, 91.4% and 97.5%, respectively using the optimized conditions (pH = 3; [Fe3+] = 5.0×10− 4 mol L− 1; [H2O2] = 0.2 mol L− 1 and 24 hours of irradiation time). Furthermore, the phytotoxicity of treated cheese wastewater was evaluated by seed germination and root elongation tests using lentil seeds as bioindicators. The experimental results showed that the combined process allowed a significant phytotoxicity reduction. The obtained outcome was encouraging and supports the possible use of the treated cheese wastewater as an additional water source for agricultural irrigation, helping to reduce the existing deficit and conserve water resources.