A closed-loop wash rack contains and treats wastewater generated from the washing of vehicles, construction equipment, and support equipment prior to reuse. The wastewater may contain fuel, oil, metals, and other contaminants. The specific equipment and process required to treat the wastewater will vary by site. Incorporating a recycling system to an existing wash rack will reduce water consumption and may eliminate the need for water discharge permits.

A typical process flow consists of the mechanical equipment (trucks, cars, etc.) stopping over a wash pad collection pit for washing. The collected wash water proceeds through a series of treatment processes discussed below.

In the first step of the process, free oil and dirt are separated from the wastewater. Sand and grit are removed as the wastewater passes through a "zig-zag" liquid-solid separator. Free oil is removed via a polypropylene coalescent pack with a high-density adsorption filter for removal of very fine oil droplets. Engineered flow baffling and an oil skimmer remove the floating oil and dirt.

The second process step removes fine particles and any remaining hydrocarbons. Water passes through a filtration system (i.e., a quad cartridge filter, an adsorbent media filter for filtration down to 5 to 20 microns, and a 30-pound carbon filter) for removal of trace contaminants.

The treated effluent is stored in a holding tank where it can be discharged to the sewer or reused for washing. The holding tank is made of a �" thick, corrosion-proof polyethylene tank. Integrated into the treatment system is a centrifugal pump with a surge tank; a switch to draw reclaimed water from the holding tank into a pressure washer; a level control valve for maintaining a proper treated water level; an overflow drain; and an ozone generator.

Closed-loop wash racks require dedicated maintenance, such as replacing or cleaning filters. Additionally, all of the closed-loop wash rack systems are available as fully assembled modular units that are simple to install.

The following table provides an example of closed-loop wash rack treatment efficiency as provided by vendors:

Table 1. Closed-Loop Wash Rack Treatment Efficiency

Note:   ppm = parts per million, ppb = parts per billion

Close-loop wash racks have been operating successfully at various locations in the United States, including the following locations:

• NAS Willow Grove, Pennsylvania
• Norfolk Naval Shipyard, Virginia
• NAS El Centro, California
• NSWC Indian Head, Maryland
• MCAGCC Twentynine Palms, California
• NAS Point Mugu, California

• Reduces the quantity and cost of water used to wash vehicles, and equipment.
• Reduces the quantity and cost of detergent used to wash vehicles, and equipment.
• Reduces wastewater loading on wastewater treatment plants.
  

• Extra space for settling tanks may be necessary for such situations as heavy soil loading from tracked vehicles.
• For areas that experience winter weather conditions, road salt may be an issue. Salt concentration build-ups may affect the effectiveness of the detergent and cause corrosion. Extra treatment effects may need to be added (e.g., evaporators and distillers) to handle and treat the salt.

• Gather facility specific information and data to identify the type of closed loop system that will meet your needs,
• Determine the cost to install and operate the system, and
• Determine the cost to maintain the system.

Other variables that can effect the costs associated with a closed-loop wash rack include:

• The cost of water,
• The cost to treat and dispose, and
• The cost of electricity.

The following economic analysis is based on information provided by vendors and the following assumptions:

• Existing facility has a wash rack and can accommodate an above ground water recovery system.
• Labor rate and length of time to wash vehicles remains unchanged.
• Minor maintenance to clean stainless steel double screen filter.
• Cost of water (includes treatment/discharge) at $0.01 per gallon.
• Cost to install one GFI dual outlet 15 amp outlet and plumb to existing equipment not included.
• Cost of electricity for one pump is not significant.
• 500 gallon above ground water recovery system with a single tank, � HP pump transfer station, 5 HP pumping motor, one particle accelerator, and a pump and motor enclosure. (This system is capable of recovering wash water from a maximum of 16 cars per hour using approximately 50 gallons of water per vehicle.)
• Facility washes 250 vehicles per month and each wash uses 50 gallons of water per wash.
• System provides 85% of the wash water required for each vehicle.
• System provides 70% of the detergent required for each vehicle.
• Cost of equipment based on GSA price.
• Cost of detergent is $400 per year.
• Closed loop system has a 15% drag out rate and requires 15% fresh rinse water to be added.
  

Table 2. Annual Operating Cost Comparison for Closed-Loop Wash Rack System

Economic Analysis Summary:

• Annual Savings for water recycling systems: $1,350
  
• Capital costs for equipment/process: $10,430
  
• Payback period for investment in equipment/process: 7.7 years

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N/S Corporation
235 West Florence Avenue
Inglewood, CA 90301
Phone: (800) 782-1582
FAX:  (310) 673-0276
Contact: Mr. Brent Feldman
Service: Drive-through vehicle wash equipment

Carbtrol Corporation
955 Connecticut Avenue, Suite 5202
Bridgeport, CT 06607
Phone: (800) 242-1150
FAX:  (203) 337-4353
E-mail:  info@carbtrol.com
URL:  http://www.carbtrol.com

RGF Environmental Systems, Inc.
3875 Fiscal Court
West Palm Beach, FL 33404
Phone: (800) 842-7771 or (561) 848-1826
FAX:  (888) 848-0047 or (561) 848-9454
URL:  http://www.rgf.com/

Blace Filtronics
2310 E. 2nd St.
Vancouver, WA 98661
Phone: (360) 750-7709
FAX:  (360) 750-7715
E-mail:  purecoat@teleport.com
Contact: Mr. Thomas Bewley

Washrack Recycle Treatment System Evaluation
Closed-Loop Wash Water Recycling System