Water scarcity has encouraged all Australians to reduce water use. The car wash industry and government bodies have been working together to reduce the use of potable water for washing cars. Many types of water recycling systems are in use in car washes, with few previous studies around their performance. More information was needed to guide the appropriate selection, installation and maintenance of these systems, and to ensure that quality standards were maintained to protect public health and safety and to encourage take up of these systems.
ACWA embarked on this research project to evaluate recycling systems for the vehicle cleaning industry in April 2008. This project examined the performance of water recycling technologies at a range of sites across Australia; evaluating the source water, the quality of the water produced and the management practices that surrounded the recycling systems. The project provided car wash owners with tools for assessing and operating their recycle systems and a framework for car wash water recycling risk management.
A comprehensive risk assessment, using the principles of hazard analysis and critical control point (HACCP) was conducted on thirteen different configurations of recycled water treatment systems specifically designed for car washing that are currently available on the market. This was done in order to identify knowledge gaps and areas where information would need to be collected in an on site monitoring program.
This was followed by an initial screening site assessment, which was aimed at validating some of the assumptions made and conclusions drawn in the HACCP analysis. 32 sites were randomly selected, ensuring that there was adequate representation from each of the 11 system types involved, urban localities and regional localities. Samples were collected of both source water and final effluent and analysed for a range of parameters. A questionnaire was also completed by the on-site car wash staff during the sampling event to gauge the operation and maintenance practices in relation to the water recycling system.
Once the hazards and risk levels were qualitatively determined, preventative or control measures were proposed to reduce the risks, and critical control points were identified. Critical control points were allocated based mainly on the potential ability to automatically control the water quality at that point, the level of risk associated with that step and the fact that subsequent process steps would not guarantee the removal of the hazard or reduce it to an acceptable level.
The content within the highest risks found were mainly associated with the presence of pathogens in the treated water, which could result from treatment systems failing to adequately remove pathogens, or from the provision of suitable conditions for opportunistic pathogens to multiply. Critical control points were identified at the source and treated water and at various stages throughout the treatment process depending on the process, usually at the treatment unit that is intended to remove pathogens.
The following items were identified as areas where validation during the initial screening site assessment was recommended:
- source water quality (turbidity, nutrients, total petroleum hydrocarbons, oil and grease, pesticides,
- herbicides, anionic and non-ionic surfactants, heavy metals, and indicator microorganisms);
- level of training received by car wash operators;
- level of maintenance on recycled water treatment systems;
- effectiveness of disinfection processes if used;
- retention time and temperature of water in holding tanks;
- likelihood of process unit failure;
- final effluent quality (turbidity, oil and grease, anionic and non-ionic surfactants, and indicator microorganisms); and
- likelihood of cross contamination through incorrectly installed plumbing fixtures.
This information was compiled in the “Guidelines for Water Recycling in the Commercial Car Washing Industry” (best practice guidelines). The guidelines are designed to inform car wash owners about the risks associated with on-site recycling of car wash water and assist them configuration for their application. With more information available to car wash owners and system manufacturers, and more diligence around risk management in car wash water recycling, the best practice guidelines should assist in covering the management of public and employee health risks associated with on-site recycling of car wash water, through a risk management approach.