Best Management Practice: Other Water Intensive Processes

Many water using processes beyond the previously covered best management practices (BMPs) are found at Federal facilities, including vehicle wash systems, maintenance services, cleaning/laundry services, single pass air conditioners, water softening systems, and others. Identify and analyze all water intensive processes for potential efficiency improvements.

This page outlines best management practices for other water intensive processes across:

Overview

Laundry facilities are often found at Federal facilities. The laundry facility may be a self-serve laundry where residents and personnel wash their own clothing, a commercial-type laundry service where residents drop off laundry to be washed or dry cleaned, or an industrial laundry facility where large volumes of Government-owned linens and uniforms are cleaned. Large amounts of water are regularly used in industrial laundries, making them highly suitable for a water efficiency program.

Evaporative coolers, also known as swamp coolers and desert coolers, work on the same principle as cooling towers. Air is cooled and humidified as it passes through porous pads that are kept moist by water dripped on their upper edges. Un-evaporated water trickles down through pads and collects in a pan for either discharge or recirculation. Since cooling relies on evaporation, these coolers work best in arid climates.

When water evaporates, it leaves behind scale and mineral deposits on the pads, reducing the volume of air flowing through the pads and compromising cooler performance. Bleed-off water serves to dilute the mineral concentration of pan water and reduces scale and dirt build-up on the pads. There are two types of bleed-off systems: once-through and recirculating. The once-through, or pumpless, type is simpler and less expensive than the recirculating, or pump, type but consumes more water and requires constant drainage.

In many areas of the country, additional water softening should not be necessary for most operations. When water softeners are required, look for systems that generate a minimal amount of waste brine per gallon of water softened.

The military maintains facilities for washing and rinsing aircraft and vehicles. These washrack facilities are an excellent candidate for water efficiency. There are five typical washrack groups based on the type of wastewater emitted:

  1. Aircraft rinsing
  2. Aircraft washrack platform
  3. Automotive vehicle washrack
  4. Tracked vehicle washrack
  5. Automotive vehicle maintenance

The amount of water used per item washed varies from approximately 100 to 3,000 gallons. Newer, commercially available washrack equipment usually includes some retrofit and recycling options that significantly reduces the amount of water used per item washed.

Get expert advice to help determine if water efficiency improvements of other water intensive processes are appropriate. New system designs and improved materials can significantly reduce water and energy requirements. However, since this may involve significant capital costs, first investigate every retrofit or operations and maintenance option. Your first resource should be local or headquarters engineers, but do not overlook input from experienced contractors or other Government agencies.

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Operation and Maintenance

To maintain water efficiency in operations and maintenance, Federal agencies should:

  • If practical, consider metering or otherwise measuring the amount of water used in other water intensive processes.

  • As with all water-using equipment, locate and repair leaks in plumbing connections.

  • If applicable, ensure procedures are in place to turn off the water supply when equipment is not in operation. Some equipment allows water to constantly run even when the equipment is turned off.

  • If applicable, check flow rates to ensure they are within manufacturer recommendations. For maximum water savings, the flow rate should be near the minimum allowed by the manufacturer.

  • To reduce water used by evaporative coolers, keep a tight rein on bleed-off water amounts. For most small coolers, bleed-off volumes should be less than a few gallons per hour for each 1,000 cubic feet per minute of air flow. Also replace worn or torn pads and inspect the recirculation pump and reservoir level controls periodically during warm months when the system is running.

  • For water softeners, set the controls to start softening and regeneration processes only when needed. Softeners with timers should be avoided.

  • For existing washing machines, encourage users to wash only full loads. If the water level is able to be set by the user, encourage using only as much water as needed for that load. Also consider separating laundry by the number of cycles needed.

  • Large commercial laundry equipment should be easily programmable to use no more water than required for the degree of soiling of the items being washed.

  • For washrack cleaning facilities that use detergents, use high quality detergents to shorten the length of time required to clean each vehicle or aircraft.

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Retrofit and Replacement Options

The following retrofit and replacement options help Federal agencies maintain water efficiency across facilities:

  • If applicable, replace water-cooled equipment with air-cooled equipment or the best available technology for achieving energy and water efficiency.

  • Avoid single-pass or pumpless coolers. Recirculation saves water and increases thermal efficiency.

  • New water softener models may come with water-efficient regeneration cycles.

  • For existing washrack cleaning facilities, there are several low-cost measures that can save significant amounts of water. Timers and automatic spray heads are useful in aircraft rinsing facilities, but not for washrack units since each vehicle or aircraft must be washed until sufficiently clean. Automatic shutoff nozzles are designed for facilities with manual rinsing. Since water is usually left on during the entire time a vehicle or aircraft is washed and rinsed, the automatic shutoff spray nozzle can save tens to hundreds of gallons per run. Low-flow and high-pressure hot water units can reduce the amount of water and solvents used by facilities for cleaning engine components. Pre-wash areas are recommended for tracked vehicle washracks with recycling systems to eliminate a majority of the coarse dirt so that it will not enter into and clog up the treatment system. Where feasible, include water reuse equipment on vehicle washing equipment. Also consider using self-closing valves on chamois wringers.

  • For washrack cleaning facilities, choose new rollover and conveyor equipment that uses less than 35 gallons per vehicle for automobiles and light trucks and less than 75 gallons per vehicle for bus and large truck washes.

  • The costliest but most highly effective way to reduce water usage at wash and rinse facilities is to implement a wastewater recycling system (see BMP #14). Where possible reuse reverse osmosis or nanofiltration reject water for vehicle washing in rollover and conveyor type systems.

  • Replace old commercial clothes washers (vertical axis) with high-efficiency washers (horizontal axis) that use significantly less energy, water, and detergent. Look for ENERGY STAR®-labeled washers with a water factor of 8.5 gallons of water used per cubic foot or less. Most full-sized ENERGY STAR-labeled washers use 18-25 gallons of water per load compared to the 40 gallons used by standard machines. These efficient washers have the potential to reduce combined utility costs by as much as 50%.

  • For large industrial or commercial type laundries, consider replacing old washers with tunnel washers or ozone laundering. Tunnel washers, also known as continuous batch washers, are heavy-duty, multi-tank systems for use in large industrial laundries. They are capable of handling up to 2,000 pounds of laundry per hour. Tunnel washers use counter current wash methods to maximize water efficiency. These are costly to install, but are capable of saving up to 70% of the volume of water used with a washer-extractor and require less operating and maintenance labor. Tunnel washers typically use two gallons of water or less per pound of laundry.

  • Technologies for reducing water use in laundry operations include ozone laundering. Ozone laundering is suited for light-to-moderately soiled laundry and uses no detergent, uses only cold water, and recycles water. Ozone-generating equipment is attached to the washer as a closed-loop system.

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Resources

The following resources provide guidance on water best management practices.

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Case Study

Sandia National Laboratories developed an extensive water efficiency program at its Microsystems and Engineering Sciences Application (MESA) complex following FEMP Best Management Practice #13PDF. The program saves the complex 80 million gallons of water annually.

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