APPLICATION OF COMBINED CHEMICAL COAGULATION AND ELECTRO-COAGULATION PROCESS FOR CARWASH WASTEWATER TREATMENT

摘要

The composition of the wastewater generated from washing vehicles is complex since it may contain detergents used in the washing process, high levels of oils, grease, gasoline residues, metals, organic matter and particles, such as dust, carbon and salt, and, therefore, its treatment is difficult but also necessary for protection of the environment. The purpose of this work was to investigate the feasibility of treating carwash wastewater by combined chemical coagulation (using polyaluminum chloride (PAC1) as coagulant) and electro-coagulation process (using aluminum electrodes) to achieve the required standards. The influence of the operating variables, such as coagulant dose, electrical potential and reaction time, on the removal efficiencies of major pollutants was determined. The rate of removal of pollutants linearly increased with increasing doses of PAC1 and applied voltage. COD, BOD_5, TSS and MBAS removal rates of 96.87, 94.0, 98.43 and 98.62 % were obtained by adding 100 mg L~(-1) PAC1 and applying a voltage of 40. Also, an increase in applied voltage from 10 to 40 V causes an increase in energy consumption from 0.01 to 0.069 kWh L~(-1), and from 0.014 to 0.095 kWh L~(-1) for 25 and 100 mg L~(-1) of PACl, respectively. The experiments demonstrated the effectiveness of chemical and electrochemical techniques for the treatment of carwash wastewaters. Consequently, combined processes are inferred to be superior to electro-coagulation alone, for the removal of both organic and inorganic compounds from carwash wastewater.