Car Wash Water Reclaim Systems
The decision to reclaim water in a car wash is usually based on economics, environmental or regulatory issues. The Clean Water Act legislates that car washes capture their wastewater and governs the disposal of this waste.
Also, the US Environmental Protection Agency has banned the construction of new drains connected to motor vehicle disposal wells. Once this ban is enacted, more car washes will be forced to look into reclaim systems.
Some chemicals found in the waste stream of carwashes include: benzene, which is used in gasoline and detergents, and trichloroethylene, which is used in some grease removers and other compounds.
Most reclaim systems provide some combination of the following methods: settling tanks, oxidation, filtration, flocculation and ozone.
Car wash reclaim systems usually will provide wash quality water within a range of 30 to 125 gallons per minute (gpm) with a particulate rating of 5 microns.
Gallon flow requirements in a typical facility can be accommodated using a combination of equipment. For example, odor control and color removal of reclaimed water can be accomplished by high-concentration ozone treatment of water held in holding tanks or pits.
When designing, installing and operating reclaim systems for your customers' car washes, first determine two things: whether to use an open or closed-loop system and whether there is access to a sewer.
Typical applications can be operated in a closed-loop environment by following a general rule: The amount of fresh water added to the wash system does not exceed water loss seen through evaporation or other methods of carry-off.
The amount of water lost will vary with different types of car wash applications. The addition of fresh water to compensate for carry-off and evaporation loss will always be accomplished as the final rinse pass of the wash application. The final rinse adds back the lost water. The final rinse pass should always be high pressure and low volume for the purpose of rinsing off any residual reclaimed water used in the wash process.
In the event sewer access is available at a particular car wash site, water treatment equipment can offer car wash operators greater flexibility when selecting which functions in the wash process will use reclaim vs. fresh water. The decision probably will be based on the cost of sewer utilization fees and associated tap or wastewater capacity fees.
Water Reuse Strategies
Self-Service Car Washes:
This is the most demanding process to address due the uncontrolled use of water in the typical self-service application. Successful operation requires some wash equipment modification.
The first requirement for this application is to change the wand nozzle from 5 gpm-tips to 2.5-gpm tips. The quality and efficiency of the wash will not be impacted, but the volume of water used in the wash process will be significantly reduced.
The second requirement will be to install a bypass circuit for the fresh-water rinse function to drop the water pressure from a standard 1,000 pounds per square inch (psi) to approximately 600 psi. Vehicle rinsing will still be efficient, but customers will be discouraged from rinsing only with fresh water, which is prevalent in a self-service environment.
Water for all wash functions in this application, with the exception of fresh water rinse, can be generated by reclaim equipment. A closed-loop system can be installed due to the high amount of vehicle carry-off and evaporation found in this application. That's because the carry-off in the self-service application is greatly impacted by the absence of automated air-drying equipment.
In-Bay Automatic High-Pressure Car Washes:
The typical in-bay automatic will use reclaim water for all wash functions except the last pass of fresh water. Here a pass is defined as one movement of the car wash equipment.
Normally, reclaimed water will be used during the first pass of rinse and changed over to fresh water just before the pass is completed. This early purging is the means to clear any reclaim water from the existing lines prior to the final fresh-water rinse pass.
One modification used in closed-loop environments is to make the undercarriage wash a standard feature – instead of an optional service – to ensure a high amount of vehicle carry-off.
Many in-bay automatics also offer spot-free rinse, either as a standard, or as an option, usually using deionized water. Water treated by reverse osmosis also can be used during this process and reclaim systems can handle the reject water produced by this method.
Tunnel Wash Applications:
The typical tunnel application, depending on size and volume, will use either a single or double reclaim unit system.
In a double-unit system, one unit is dedicated to reusing wash water while the second unit is dedicated to rinse water. The car wash conveyor will contain a dam, which will separate the two types of water.
The wash-side unit will provide treated water for prepguns, cool down, presoak, tire blaster and high-pressure wash. The other unit will provide high-pressure rinse with a final application of fresh water to spray off any remaining reclaim rinse water.
The typical tunnel application operating in a closed-loop environment sometimes will use a tank level control system, which consists of a float sensor on the wash side of the tunnel. This level control system is the mechanism used to transfer water carried over the conveyor dam from wash to rinse. The water transfer is accomplished by interconnection of the reclaim equipment.
Short-length tunnels more often will use a single reclaim unit. Here, one unit will provide all water for the washing equipment up to the last high-pressure, low-volume fresh water rinse.
Industrial Washing Applications:
Industrial applications are like fingerprints. Every situation is unique, requiring different equipment. In some cases, site-specific applications and equipment modification may be required.
Reclaim systems can be manufactured for new or pre-existing locations. Companies usually can supply drawings and information, including systems guidelines and estimated cost-savings to provide to your customers.
Industrial applications needing reclaim systems for vehicle washing include transportation, agriculture, rental companies and heavy-duty construction equipment.
Bob Koo is president of Con-Serv Manufacturing Inc. in Lakeland, FL.