Enhancing dairy wastewater treatment: evaluating the efficacy of chemical coagulation and photo-Fenton oxidation processes

This study investigated the effectiveness of chemical coagulation and photo-Fenton processes for dairy wastewater treatment (DWWT). The study was conducted in two batch phases. In the first phase, polyaluminum chloride (PAC) was used as a coagulant. In the second phase, the photo-Fenton process using two UV lamps (16 W and 55 W) was performed on the coagulation effluents. This combined approach was expected to improve overall removal efficiency, reduce chemical consumption, and minimize sludge generation. Consequently, various reagent concentrations were examined to determine optimal values. By employing the optimal coagulant concentration (PAC dosage of 75 mg/L), the removal efficiencies of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) reached 50.3%, 44.5%, 31.42%, and 43.16%, respectively. The optimal photo-Fenton conditions obtained in the 16-W reactor were time = 70 min, H2O2 = 600 mg/L, and Fe2+ = 130 mg/L, while in the 55-W reactor, they were time = 50 min, H2O2 = 400 mg/L, and Fe2+ = 110 mg/L. The results showed that the total removal efficiencies of COD, BOD, TKN, and TP under the optimal conditions of coagulation and photo-Fenton in the 16-W reactor were 93.03%, 87.17%, 83.95%, and 78.15%, respectively, whereas using a 55-W reactor, the overall removal efficiencies were 95.69%, 91.19%, 88.08%, and 75.5%, respectively. The results indicate that while this method is effective for DWWT, the 16-W reactor was more cost-effective, with only a slight performance difference compared to the 55-W reactor.