Solar driven homogeneous sodium hypochlorite/iron process in treatment of petroleum refinery wastewater for reusing

This study reports the performance of a new homogenous solar/sodium hypochlorite/iron process in treatment of petroleum refinery wastewater for the aim of water reusing. A pilot-scale solar photo-reactor with capability of automatic rotating against the sun's surface was employed. Experiments were conducted by following the chemical oxygen demand (COD) and the total organic carbon (TOC) criteria at different times. The optimal operating conditions of 548 mg/L of sodium hypochlorite, 48 mg/L of ferrous salt and pH 3 were found under which COD and TOC removal of, respectively, 78.6% and 69.3% were corresponding after 180 min treatment. The COD removal could easily reach to 88.5% by multiple feeding of the reagents. A significant improvement in the biodegradability was also achieved by raising the BOD5/COD ratio from 0.36 to 0.69. The GC/MS headspace analysis indicated a high degradation level of the most hydrocarbons. Meanwhile, the COD removal was appeared with a pseudo first order kinetic in term of accumulated UV energy. Comparing the performance with the alternative processes including solar Fenton as well as the cost estimates revealed the high preference of the employed process.