Document Type : Original Article
Authors
1
Department of Water Sciences, Sho. C., Islamic Azad University, Shoushtar, Iran
2
Research Center for Water Science and Environmental, Department of Water Sciences, Sho.C., Islamic Azad University, Shoushtar, Iran
3
Department of Water Sciences, Water Science and Environmental Research Center, Sho. C., Islamic Azad University, Shoushtar, Iran.
4
Department of Water Sciences, Water Science and Environmental Research Center, Sho. C., Islamic Azad University, Shoushtar, Iran
5
Department of Environmental Health Engineering, Behbahan Faculty of Medical Sciences, Behbahan
10.22034/nawee.2026.584375.1226
Abstract
This study examines the treatment of gray water containing high concentrations of detergents through an integrated process combining a Sequential Batch Reactor (SBR) with UV/H₂O₂ advanced chemical oxidation. The raw gray water was characterized by relatively high pollutant levels, including 600 mg/L chemical oxygen demand (COD), 200 mg/L biological oxygen demand (BOD), 4 mg/L total phosphorus (TP), and 15 mg/L total Kjeldahl nitrogen (TKN). Biological treatment in the SBR significantly improved water quality, reducing BOD₅ to 40 mg/L and COD to 162 mg/L. The use of activated carbon, however, was found to have only a minor effect on overall treatment performance. To further enhance treatment efficiency, chemical oxidation conditions were optimized, with the best results achieved at an H₂O₂ dose of 12 mg/L and a reaction time of 3 hours under UV irradiation. Under these conditions, the combined system achieved high removal efficiencies of 90.6% for COD, 85% for BOD, 82.5% for TP, and 65% for TKN. In addition to pollutant removal, applying chemical oxidation as a pre-treatment step improved the biodegradability of organic compounds by 6%, indicating better suitability for subsequent biological treatment. The study also found that incorporating an anaerobic unit before the aeration stage enhanced phosphorus removal. However, increasing the anaerobic retention time beyond two hours did not provide any significant additional benefit. Overall, the integrated SBR and UV/H₂O₂ process proved effective for reducing pollutant loads and improving the biodegradability of gray water.
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