Combination of Coagulation and VUV+H2O2 for the Treatment of Color and Organic Matter in Treated Effluent Wastewater from a Sugar Factory

Abstract

The removal of color and organic matter in treated effluent wastewater from a sugar factory by coagulation, combined with advanced oxidation processes (AOPs), including UV, UV+ hydrogen peroxide (UV+H2O2), vacuum UV (VUV), and VUV+H2O2, was investigated in this study. The effect of pH and a dose of coagulants (aluminum sulfate (alum), polyaluminium chloride (PACl), ferric chloride (FeCl3), and ferric sulfate (Fe2(SO4)3)), as a pretreatment step prior to AOPs, was analyzed. The optimum pH and coagulant dose for coagulation was pH 6 and 600 mg/L, respectively. The iron-based coagulants generally provided the better removal efficiency than the aluminium-based coagulants. Among four coagulants, FeCl3 was chosen for use in the pretreatment step since it provided the best performance for dissolved organic carbon (DOC) removal, UV transmission improvement, and cost-effectiveness. The removal efficiency and degradation rate of color, UV absorbance at 254 nm (UV254), and DOC increased along with the H2O2 dosage. The reduction of UV254 indicated a less aromatic portion of DOC after AOPs. The ratio of DOC:H2O2 at 1:3 yielded the highest DOC removal of 70 ± 0.42 and 73 ± 0.19% in 60 min by UV+H2O2 and VUV+H2O2, respectively. For energy efficiency, VUV+H2O2 (DOC:H2O2 =1:3) provided the lowest electrical energy per order (EEO) (26 kWh/m3). After coagulation, DOC combined with VUV+H2O2 was reduced to the appropriate level for reuse (4 mg/L). The findings from this research demonstrate the promise of coagulation coupled with the VUV+H2O2 process as a technology for water reuse application in the sugar industry.