Treatment of real refinery wastewater was investigated based on alternative ferrous-assisted ultraviolet/persulfate (UV/PS/Fe2+) homogeneous processes. An effective circulating photo-reactor, equipped with an only 6 W, UV lamp was employed. The effects of operating parameters, including PS salt and ferrous sulfate salt (to supply ferrous ion) dosages, solution pH, reaction time, temperature, and applying ultrasound (US) waves were studied. The criteria in degradation process were the chemical oxygen demand (COD) and the total organic carbon (TOC). The optimum operating conditions were found at PS concentration of 302.9 mg L–1, ferrous sulfate salt concentration of 20.3 mg L–1 and pH of 4.8, under which the COD, turbidity, and TOC of the wastewater were reduced respectively to 66.6%, 76.9%, and 39.2% after 60 min. Increasing temperature from 25°C to 50°C and applying US caused significant enhancements in these criteria. From results, the efficiency of investigated processes was appeared in the order of UV/PS/Fe2+/US > UV/PS/Fe2+/heat > UV/PS/Fe2+ > UV/PS > UV. An overall first-order rate of COD removal was detected for the UV/PS/Fe2+ process and accordingly, the electrical energy consumption for one order of magnitude COD removal, under optimum conditions, was 10.56 kWh m–3 as well as total operating cost of only $1.82 m–3.
