Membrane processes for the reuse of car washing wastewater

This study investigates alternative treatments of car wash effluents. The car wash wastewater was treated by settling, filtration, and membrane filtration processes. During settling, total solid concentration decreased rapidly within the first two hours and then remained constant. Chemical oxygen demand (COD) and conductivity were decreased by 10% and 4%, respectively. After settling, wastewater was filtered throughout a 100 μm filter. It was found that filtration had a negligible effect on COD removal. Finally, wastewater was filtered by four ultrafiltration membranes of varying molecular weight cutoff (MWCO) (1, 5, 10 and 50 kDa) and one nanofiltration membrane (NF270, MWCO = 200–400 Da). The permeate COD concentrations varied between 64.5 ± 3.2 and 85.5 ± 4.3 mg L −1 depending on UF pore size. When the NF270 nanofiltration membrane was used, the permeate COD concentration was 8.1 ± 0.4 mg L −1 corresponding to 97% removal. FeCl 3 precipitation and activated carbon adsorption techniques were also applied to the retentate and 60–76% COD removals were obtained for activated carbon adsorption and FeCl 3 precipitation, respectively.