Reuse of car wash wastewater by chemical coagulation and membrane bioreactor treatment processes

• Ozonation after coagulation gave greater removal of contaminants than coagulation.
• MBR was very effective in reducing COD compared to ozonation after coagulation.
• The kinetics of MBR system is discussed using mass balance computations.
• MBR reduced all contaminant types and met the car wash water quality guidelines.

Car wash wastewater contains significant concentrations of contaminants such as nutrients, organics, particulate matter, sand, oil, grease, diesel detergents and so on. A range of treatment processes such as a membrane bioreactor (MBR), coagulation and ozonation were investigated to treat car wash wastewater. Ozonation was effective in removing the chemicals and suspended solids; the removal efficiency was greater than the coagulation process. Once the MBR system was acclimatised, 100% of suspended solids, 99.2% of COD, 97.3% of TOC and 41% of ammonia were removed. This study demonstrates that MBR is a potentially promising treatment system for recycling car wash wastewater which could be reused in the same car wash station.