Establishing a treatment process for practical and economic disposal of car wash wastewater has become an urgent environmental concern. Photo-Fenton’s process as one of the advanced oxidation processes is a potentially useful oxidation process in treating such wastewater. Lab-scale experiments with UV source, coupled with Fenton’s reagent, showed that hydrocarbon oil is degradable through such a process. The feasibility of photo-Fenton’s process to treat wastewater from a car wash is investigated in the present study. A factorial design based on the response surface methodology was applied to optimize the photo-Fenton oxidation process conditions using chemical oxygen demand (COD) reduction as the target parameter to optimize. The reagent (Fe2+ and H2O2 concentration) and pH are used as the controlling factors to be optimized. Maximal COD reduction (91.7%) was achieved when wastewater samples were treated at pH 3.5 in the presence of hydrogen peroxide and iron in amounts of 403.9 and 48.4？mg/L, respectively. 1. Introduction Car washing leads to disposal of large amounts of oily polluted water which results in potentially high levels of nutrients, metals, and hydrocarbons flowing into storm drains. The composition of pollutants found in car wash wastewater varies according to the way of washing, mechanical car washing or artificial high-pressure water washing, and the size and type of vehicle (e.g., small car, truck, commercial van, etc.). In some cases, car wash wastewater may also contain heavy metals [1–3]. Considering the large volume of wastewater generated from the car washing process, wastewater treatment coupled with recycling may possibly be an essential water quality measure. For instance, in the US, commercial car wash facilities either recycle or treat their wash water prior to discharge to the sanitary sewer system, so most storm water impacts from car washing are from residential car wash systems that discharge polluted wash water into the storm drain system [1]. Some countries, for example, Switzerland, Germany, and The Netherlands, no longer allow outdoor car washing away from car washing stations [4]. In Egypt, as well as in many countries worldwide, car wash activities within petrol stations and outdoor car washing are among those activities that pose an environmental threat to the main freshwater source, the river Nile, which is already subjected to untreated wastewater [5]. Consequently, there is a growing need for research particularly on the application of innovative technologies in the treatment of such kind of wastewater. The
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