“It seemed logical that since South Africa is a water scarce country, the issue of water consumption and conservation should be among the first to be considered,” Duvenage says. “At Avis, we wash over 2500 vehicles a day. In 2007, in first examining our water usage at our main high volume vehicle cleaning facilities, we realised that by installing intensive water-recycling technology, we could reduce the amount of water used by over 90%, from over 200 to about 20 litres per wash. The ‘final rinse arch,’ in the car wash process required clean water, whereas recycled water could be used during the ‘pre-soak’ and ‘shampoo’ stages, which, is where most of the water is needed,” The clean water supply during the final rinse arch keep the system topped up and supplied with fresh water.
The used “grey” water per wash is diverted into soak-pits to remove sediment, where after it is passed through a high pressure centrifugal force to remove fine particles and cleans the water to well below 4000 ppm, a very good standard for this process.
One would think that 90% recycling should be sufficient, but not so at Avis. The next step was a plan to harvest rainwater from the rooftops of adjacent buildings to replace the municipal water supply in the final rinse arch of the car wash process. Bulk underground reservoirs were installed to capture the rainwater run-off and a valve system was introduced to the wash bay machines to automatically shut off the municipal supply and replace it with harvested rainwater, thereby making the main Avis depots water-neutral during the rainy season.
Source: Green Times