Water Efficiency Guide for Laboratories Editor’s note: This three-part article is one of a series of Best Practice Guides for laboratories, produced by Laboratories for the 21st Century (“Labs21”), a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy. Geared toward architects, engineers, and facility managers, these guides provide information about technologies and practices to use in designing, constructing, and operating safe, sustainable high-performance laboratories. For more information about these free resources, see: www.Labs21century.gov/toolkit/bp_guide.htm. The Labs21 website also provides full information about the agency’s upcoming annual conference, to be held in San Antonio Oct. 17-19. The first article, which was published in April, covered cooling towers and lab process equipment. The second part, which appears here, discusses lab-specific best practices and reviews alternative water sources.    The final installment will be published in July, reviewing alternative water sources, summarizing design considerations, and providing a complete reference and resource list. Water efficiency is an important consideration not only for special process equipment (see April, page 8) but in other lab equipment, as well. This includes equipment used in laboratory water treatment, sterilization, photographic, x-ray, and vacuum systems.    U.S. Department of Energy Energy Efficiency and Renewable Energy Federal Energy Management Program www.eere.energy.gov. Water-treatment equipment In their day-to-day operations, many laboratories require high-quality water or water free from mineral and organic contaminants. There are five basic levels of separation processes: particle filtration, microfiltration, ultrafiltration, nanofiltration, and hyperfiltration. A filtration spectrum (see www.gewater.com/lib/index.jsp) illustrates the separation process and size range for common types of materials. Typically, as finer and finer particles are removed, energy use and water waste increase. Therefore, facility managers will want to choose a filtration process that matches their requirements. For example, reverse osmosis (RO) water should be used only in processes that require very pure water. Because RO produces the purest water, it usually requires the most energy and materials and results in the most waste. Two streams exit the RO system: the concentrate stream and filtered, purified water. The concentrate is rejected water containing a high level of dissolved minerals. The concentrate is then typically sent to a drain, or a portion of it is recycled back to the feed stream to increase the system’s overall water recovery. Although the concentrate is high in dissolved minerals, it can be reused in nonpotable applications (e.g., in bathroom commodes).    As with cooling tower blow-down, water quality should be monitored to avoid fouling other systems. The recovery rate (i.e., the ratio of the filtered purified water to the volume of feed water) is typically 50 to 75% for a conventional RO system operating on city feed water. To make a water purification system more efficient: • Evaluate the laboratory’s requirements for high-quality water, including the total volume and the rate at which it will be needed, so that the system can be properly designed and sized. • Determine the quality of water required in each application; use the lowest appropriate level of quality to guide the system design (FEMP 2004; full references to all notations in this article will be provided in the July issue). • Evaluate the quality of the water supply for a period of time before the system is designed. This evaluation allows designers to accurately characterize the quality of the water supply and helps them determine the best method for attaining the quality level required. For example, city water contains a wide range of impurities. EPA suggests a limit of 500 mg/L for total dissolved solids (TDS) (see also www.epa. gov/safewater/). Note that the TDS of one public water supply has ranged from 33 to 477 mg/L over the course of a year (New York City Dept. of Environment 2003). • Consider using one of the proprietary systems for improving system efficiency; some claim recovery rates up to 95%. Disinfection/sterilization systems Two types of systems are used for disinfection in laboratories: sterilizers and autoclaves. Sterilizers use water to produce and cool steam and to cool wastewater before discharge. Some units also use water to draw a vacuum to expedite the drying process. Water use in sterilizers ranges from 1 to 3 gpm. Autoclaves use ethylene oxide as the sterilizing medium rather than steam. Water is used to remove the spent ethylene oxide and, like sterilizers, some units use water to draw a vacuum to expedite drying. Their water usage ranges from 0.5 to 2 gpm.   Both autoclaves and sterilizers can consume large amounts of water, depending on the size, age, and use rate of the unit. Often, these units are operating 24 hr per day, averaging about 16 hr in idle mode (Van Gelder 2004). Because older units typically have no option for flow control, they can waste a lot of water. Laboratories and medical facilities often have a large number of these units. To make autoclaves and sterilizers more efficient: • Purchase new equipment only if it is designed to recirculate water or allows the flow to be turned off when the unit is not in use, or both. • Adjust flow rates to the minimum ones recommended by the manufacturer, and review and readjust them periodically. • Install a small expansion tank instead of using water to cool steam for discharge to the sewer. Check with the manufacturer to make sure this will not interfere with the unit’s normal operation. • Shut off units that are not in use, or install an automatic shut-off feature if it does not interfere with the unit’s normal operation. n Use high-quality steam for improved efficiency (New Mexico Office of the State Engineer 1999). • Use uncontaminated, noncontact steam condensate and cooling water as make-up for nonpotable uses, such as in cooling towers and boilers (Vickers 2001). • Consider purchasing a water conservation retrofit kit; many are now available for older units. They reduce water use by either controlling the flow of tempering water or by replacing the venturi mechanism for drawing a vacuum. Tempering kits sense the discharge water temperature and allow tempering water to flow only as needed. This can save about 2,900 gal/day when equipment is in idle mode. Venturi kits replace the venturi with a vacuum pump, saving approximately 90 gal per cycle (Van Gelder 2004). Fig. 1. Nonpotable water collection and reuse. Source: Labs21. Click here to enlarge. Photographic and x-ray equipment Photographic and x-ray machines typically use a series of tanks and dryers to develop and process film. A typical x-ray film-processing machine requires a water flow of about 2 gpm. However, many processors use flow rates that are higher than necessary to ensure acceptable quality, sometimes as much as 3 to 4 gpm. Tap water is often used once for developing purposes and then allowed to drain into the sewer system. Newer machines use less water in the process and allow less of the silver used in developing to be discharged as waste. To eliminate water use in photographic departments, some facilities have moved to digital x-rays and photography, and computerized printing. This change also eliminates the need for chemicals used in photographic processing. To use less water in photographic and x-ray processing: • Adjust the film processor flow to the minimum acceptable rate. This may require installing a control valve and a flow meter in the supply line. Post minimum acceptable flow rates near the processors. • Recycle rinse bath effluent as make-up for the developer/fixer solution. A silver recovery unit can also be helpful in recovering metal for later use. • Install a pressure-reducing device on equipment that does not require high pressure. • If the processor has a solenoid or an automatic shut-off valve for times when the unit is not in use, check it regularly to ensure that it is working properly (New Mexico Office of the State Engineer 1999). A malfunctioning valve can let water flow when the system is in standby mode. • Consider using one of the proprietary water efficiency devices for x-ray and photo processing. Some reuse water, and in emergencies, they can run equipment on only 15 gal (see also www.caxray.com/products_water_save_plus.html). • Replace older equipment with newer, more efficient models. Look for models with a squeegee that removes excess chemicals from the film. This can reduce chemical carryover by 95% and reduce the amount of water needed in the wash cycle (Vickers 2001).    Vacuum systems Wet chemical laboratories often employ faucet-based aspirators to create a venturi-type siphon, used as a vacuum source. These systems can apply a vacuum to laboratory filtration systems for extended periods of time. A better approach would be to install a laboratory vacuum system or to employ small electric vacuum pumps to create the pressure differentials necessary for vacuum applications. Dishwashers Laboratory dishwasher systems use deionized or RO water to deliver water of different qualities in the rinse cycles. They are designed to remove chemical build-up on glassware, pipettes, and other types of equipment. Newer dishwashers use less water than older models. With newer models, the operator can also match the number of rinse cycles to the desired task. Fewer cycles should be selected whenever possible, if that will not affect the quality of the product.   To reduce the amount of water used by dishwashers: • Run dishwashers only when they are full. • Use newer, cleaner rinsing detergents. • Reduce the number of rinse cycles whenever possible. For more information • On water-efficient laboratories: Stephanie Tanner, National Renewable Energy Laboratory, 202-646-5218, stephanie_tanner@nrel.gov. • On Laboratories for the 21st Century: Dan Amon, PE, U.S. Environmental Protection Agency, 202-564-7509, amon.dan@epa.gov, or Will Lintner, U.S. Dept. of Energy, Federal Energy Management Program, 202-586-3120, william.lintneer@ee.doe.gov.  Vivariums Vivariums use equipment and practices specific to animal care, such as automatic animal watering systems. These can consume large volumes of water because of the need for constant flows and frequent flushing cycles. If it is properly sterilized, this water can be recirculated in the watering system rather than discharged to drains. Where this water cannot be recycled for drinking because of purity concerns, if it is sterilized, it is still likely to be acceptable for other purposes, such as cooling water make-up, or for cleaning cage racks and washing down animal rooms. It is also possible to reduce the amount of water used for some process equipment (e.g., cage washers and sterilizers) in laboratory vivariums. For example, small cages are typically cleaned in a tunnel washer; laboratories could reuse the final rinse water from one cage-washing cycle in earlier rinses in the next washing cycle, by making use of a counter-current flow system (see April, page 10). Stephanie Tanner at the National Renewable Energy Laboratory, Golden, Colo., was the principal author of this document. The author thanks Bill Hoffman, City of Austin water department, for information on rainwater harvesting and A/C condensate recovery, and James Kohl, URS Corp., for initial research. Roy Sieber of Eastern Research Group and Otto Van Geet, PE, Nancy Carslile, AIA, and Sheila Hayter, PE, all of NREL, provided helpful comments and peer reviews. Paula Pitchford and Susan Szepanski of NREL provided editing and the graphic design of the original Best Practices Guide. U.S. Department of Energy Energy Efficiency and Renewable Energy Federal Energy Management Program. www.eere.energy.gov Laboratories for the 21st Century U.S. Environmental Protection Agency Office of Administration and Resources Management www.labs21century.gov