On-site carwash wastewater treatment and reuse: a systematic review

The carwash is a common municipal service and important water consumer in municipal activities. Carwash wastewater (CW) has unique quality characteristics due to the car washing process; therefore, various processes are required for its treatment. The aim of this systematic review was to identify and introduce an on-site CW treatment method between the investigated processes. For this purpose, the related articles were obtained from four databases by keyword identification and a search protocol definition. Results show that CW quality is affected by type of vehicles washed, seasons, carwash location, washing method, and detergent dose and also detergent type. Membrane process was the most common treatment process for CW treatment. In addition, the other processes such as chemical coagulation, electrocoagulation, electrooxidation, and membrane bioreactor were commonly used for this purpose. High efficiency for carwash wastewater treatments were reported for most pollutant such as turbidity (more than 90%), oil content (more than 75%), and COD (70-95%) in studies. Furthermore, low water recovery rates, rapid and severe fouling, sludge production, energy consumption, and adverse change in effluent such as decrease in pH andincrease-dissolved solids were the main limitations of CW treatment processes. Therefore, short treatment time, optimal efficiency, operation condition, and high water recovery ratio are critical aspects of on-site treatment and reuse of CW.

Automated summary

The carwash wastewater has unique quality characteristics and requires various treatment processes. The membrane process is the most commonly used method, followed by chemical coagulation, electrocoagulation, electrooxidation, and membrane bioreactor. The treatment efficiency for pollutants such as turbidity, oil content, and COD is reported to be high. However, there are limitations such as low water recovery rates, rapid fouling, sludge production, energy consumption, and changes in effluent quality. Therefore, short treatment time, optimal efficiency, operation condition, and high water recovery ratio are critical aspects of on-site treatment and reuse of carwash wastewater.