Treatment of Cheese Wastewater by Coagulation-Flocculation Coupled with Heterogeneous Photocatalysis Using a New Synthesized TiO2 Anatase: Treatment Efficiency and Phytotoxicity evaluation

The main objective of this research was to evaluate the treatment efficiency of cheese wastewater containing organic pollutants by combining coagulation-flocculation with ferric chloride (FeCl3) and heterogeneous photocatalysis in which a new synthesized TiO2 was used under UV-A (600 W) irradiation. Coagulation-flocculation experiments showed that the removal of turbidity, chemical oxygen demand (COD), and biological oxygen demand (BOD5) were 98.83, 49.23, and 40.58%, respectively, at a coagulant dose of 0.4 Fe3+ g L−1. Thereafter, the application of TiO2-based photocatalysis process to the pretreated cheese wastewater improved the COD reduction from 3179.26 mg O2 L−1 to 437.47 mg O2 L−1 with a removal percentage of 86.24%, using the optimized conditions given by pH (4); TiO2 (0.5gL−1), and 16 h for irradiation time. Finally, cheese wastewater samples were examined for their phytotoxicity, before and after treatments, through seed germination/root elongation tests using tomato, cucumber, and alfalfa seeds. The experimental results showed a significant decrease in toxicity of the treated cheese wastewater using the combined process. These findings are encouraging and support the possible use of treated cheese wastewater as an additional freshwater source for irrigation.