Innovative Carwash Wastewater Treatment and Reuse Through Nature-Based Solutions

Vehicle washing facilities (VWFs) consume substantial tap water and produce wastewater with harmful compounds. This study examines Nature-based Solutions (NbS) for treating and recycling vehicle wash wastewater. Conducted at a VWF in Girona, Spain, the project tested three pilot systems: Vertical Flow Treatment Wetland (VFTW), Horizontal Flow Treatment Wetland (HFTW), and Infiltration-Percolation (IP) filter. Over two years, 32 quality parameters, including physicochemical and microbiological indicators, were monitored. VFTW and IP systems were the most effective, reducing turbidity below 5 NTU, COD to under 20 mg/L, and E. coli below 10 CFU/100 mL, meeting Spanish reuse standards. Pre-treatment was critical for managing oils, fats, and hydrocarbons, preventing clogging in the HFTW and IP systems. A final chlorination step ensured residual disinfectant, particularly for controlling Legionella, allowing the treated water to be safely used in the pre-wash and initial wash stages. The systems achieved up to 60% water reuse, reducing the need for potable water, minimizing pollutants, and cutting operational costs, contributing to a more sustainable approach in vehicle washing operation.