Treatment of high salinity wastewater using CWPO process for reuse

Abstract A high salinity wastewater from epoxy resin was treated with the catalytic wet peroxide oxidation (CWPO) process, so that it can be reused as the chlor-alkali process feedstock. Both bench and pilot scale trials were conducted out in this research. The effect of oxidant (hydrogen peroxide) and catalyst (ferrous sulfate) dosages, and their dosing methods, pH value, temperature, and reaction time on TOC removal by the CWPO process were evaluated through bench experiment. The obtained optimal reaction conditions for the CWPO process were as following: H2O2 dosage = 0.735 M, Fe2+ dosage = 0.027 M, temperature = 90ºC, pH = 3.0–3.5, and reaction time = 200 min. Multiple additions of oxidant and catalyst significantly enhanced TOC removal compared to adding the same total dosage in one step. In a pilot trail, 735 moles of H2O2 and 27 moles of Fe2+ were continuously added to a 1000 L wastewater over 3 hours while the pH and temperature of the reaction solution were automatically controlled at 3.3 ± 0.5 and 90 ± 2℃, respectively, the wastewater TOC values were reduced to less than 150 mg/L from 2500–2700 mg/L, which satisfies the influent TOC limit (200 mg/L) of the diaphragm electrolytic cell. In addition, both the iron ion and sulfate ion concentrations in the pilot effluent were less than their influent limits of the diaphragm electrolytic cell, thus the treated wastewater had been successfully applied in a chlor-alkali plant for production chlorine and caustic soda.