More environmentally friendly vehicle washes: water reclamation

The weight of vehicle wash activities in urban water management is evaluated in Brazil. The treatment of wash wastewater from a typical car wash station by flocculation-column flotation plus sand filtration and chlorination has been fully studied, and reclaimed water criteria are discussed. A quantitative microbial risk assessment (QMRA) was performed with a dose-response model, and an Escherichia coli limit of 200 UFC.100 mL−1 in the reclaimed water was suggested as acceptable microbiological risk. A mass balance was applied for the assessment of the concentration of critical constituents as a function of water cycles, and the results revealed that the chloride and TDS concentrations in reclaimed water stabilised below 350 and 900 mg L−1, respectively. The cost-benefit analysis performed for six different Brazilian scenarios showed that water reclamation is highly competitive and that the payback period might be as short as one year, depending on water prices and daily wash demand. It is believed that the implementation of the present technology in Brazil and elsewhere is dependent mainly on state policies such as those pertaining to the involvement of larger players (for example, large Brazilian petro station companies) and creating and supporting an early niche market.