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 March, covered cooling towers and lab process equipment. The second part, which appeared in June , discussed lab-specific best practices This final installment reviews alternative water sources, summarizes design considerations, and provides a complete reference and resource list.    This exterior view of the Nidus Center for Scientific Enterprise in St. Louis shows the cisterns that store rainwater used to irrigate the grounds of this research facility. Photo: Steve Hall, Hedrich Blessing. Click here to enlarge. Alternative water sources Large facilities, such as laboratory buildings, are good candidates for alternative, or unconventional, water sources because they usually use a large amount of nonpotable water. This section describes some ways that facilities can greatly increase their total water supply without adding capacity from the public system or well. The two most useful water sources for laboratory buildings are air- conditioning condensate recovery and rainwater harvesting. Both can provide fairly steady sources of relatively pure water; they are limited primarily by the cost of capturing the water. Another source is reclaimed effluent from wastewater treatment plants. Utilities often supply this kind of water at reduced prices. Condensate recovery In many places in the U.S., mechanical space conditioning generates significant quantities of condensate, as warm humid air is cooled and dried for temperature and humidity control. The condensate from air conditioners, dehumidifiers, and refrigeration units can provide facilities with a steady supply of relatively pure water for many processes. Laboratories are excellent sites for this technology because they typically require dehumidification of a large amount of 100% outside air. The potential for condensate recovery depends on many factors, such as ambient temperature, humidity, load factor, equipment, and size. However, because this technique is relatively new, there are no established formulas for calculating the exact amount that can be collected from a given system.   Fig. 1. Nonpotable water collection and reuse. Source: Labs21. Click here to enlarge. Condensate water is relatively free of inerals and other solids. In most cases, it is similar in quality to distilled water. This makes it an excellent source for cooling tower or boiler make-up and RO feed water, for example. Another advantage of using condensate for cooling tower make-up is that there is usually a good seasonal correlation between condensate supply and cooling tower demand. Additional savings could result from reduced chemical usage and lower membrane maintenance costs. Fig. 1 illustrates how water from several sources, including AC condensate, can be piped into one storage tank for reuse in nonpotable water applications. Condensate should not be considered potable because it can contain dissolved contaminants and bacteria. However, because biocide is added to cooling towers, condensate is an excellent option for cooling tower make-up. For laboratories that are not medical or bacteriological research facilities, condensate should be safe to use for drip-type irrigation. However, medical and other facilities could use disinfected condensate in spray-type irrigation. Normal chlorine feed equipment, ozone, or ultraviolet disinfection should be effective. It is best to use condensate in a process that provides an additional level of biological treatment (Hoffman). Predicting water recovery from condensate The cities of San Antonio and Austin, Texas, developed some rules of thumb that can be used anywhere for condensate recovery systems that are working well in their particular climates. By observing installed systems, they found that from 0.1 to 0.3 gal of condensate could be collected for every ton-hour of operation of their cooling equipment. A ton-hour is the amount of cooling capacity of a one-ton air-conditioning system operating for one hour. They also found that the 0.1 to 0.3 conversion factors (CF) were largely associated with levels of ambient humidity. For example, they could assume 0.1 gal would be produced at a humidity of <70%, 0.2 gal would be produced at >80%, and 0.3 gal at >90%. The load factor is the ratio of average load during a period to the peak load and is expressed as a percentage: Gal of condensate = (load factor %) (CF) (cooling equipment tonnage). Source: Wilcut and Lillibridge 2004 Rainwater harvesting Rainwater is another excellent source of nonpotable water. It can be used in many of the applications in which condensate recovery water is used. Typically, however, rainwater contains fewer impurities than potable water from a public drinking water supply. The only cost is the capital cost of equipment to collect and store the water (which can be significant). Storm water from other impervious surfaces besides rooftops can also be collected. However, because storm water is not as high in quality as rooftop rainwater, it is best to use storm water only for irrigation. Rainwater systems typically consist of six elements: the roof or catchment area; gutters, downspouts, or roof drains; leaf screens and roof washers that remove debris and contaminants; cisterns or storage tanks; a conveyance system; and a treatment system. Leaf screens are effective in removing large debris from the system. The storage tank or cistern is the most costly element. It can be either above or below ground, but close to supply and demand points to minimize piping needs. It should have a tight-fitting lid to prevent evaporation and to keep out mosquitoes, animals, and sunlight (which allows algae to grow). Laboratories considering the use of rainwater should check with local or state governments about possible restrictions. Many states, particularly those in the West, restrict rainwater use. The restrictions have to do with water rights laws, which are complex and vary according to the jurisdiction. Some allow facilities to detain water for irrigation and other uses that return the water back to the system, but they do not allow water to be retained permanently on a site. Rainwater and condensate recovery systems can be expensive to install as retrofits. Storage capacity in particular is expensive. However, properly sizing the system to match demand to supply could greatly reduce costs. The real value of these systems comes from the high quality of water they provide. Calculating rainwater collection potential To determine the amount of rainwater that can be collected at a site, first determine the collection area, average rainfall, and collection efficiency. The collection area is the total square footage of the roof or catchment area. The average rainfall for a site can be obtained from National Weather Service data. Because of seasonal variations, rainwater should be considered in terms of variable monthly supply and demand for supplemental uses. To develop a collection range, use average rainfall as a maximum and half the average rainfall as a minimum, to represent drought conditions. The conversion factor is as follows: 1 in. of precipitation on 1 ft2 of collection area yields 0.6233 gal. Rainwater volume (gal) = collection area (ft2) 3 collection efficiency (%) 3 avg. rainfall (in.) 3 0.6233 (gal/in.).   The collection efficiency depends on such factors as roof material, diversion amount, and design retention. The smoother, cleaner, and more impervious the roof surface, the more high-quality water can be collected.    Pitched metal roofs lose negligible amounts of water; concrete or asphalt roofs lose an average of about 10%; and built-up tar and gravel roofs lose as much as 15%. Flat roofs can retain as much as half an inch. Some water is lost to spillover in drains and gutters; some cisterns become full during periods of heavy rain, and some water can be lost to overflow. So many installers assume efficiencies between 75% and 90% (Texas Water Board 1997). A laboratory complex in Washington, D.C., provides a hypothetical example of rainwater harvesting. The site receives an average of 43 in. of precipitation each year. The complex has a roof area of 54,000 ft2. With a collection efficiency of only 75%, the facility could capture about 1,085,477 gal of rainwater annually. The site would save on both water and sewer fees if water normally drains to the sewer. Using a pricing rate similar to those in the condensate recovery example, this system would save $5,970 per year in water costs. Reclaimed wastewater Reclaimed wastewater is an option in limited circumstances, when a laboratory has access to municipal wastewater that has been treated to a secondary disinfection level or when treated wastewater can be generated cost effectively on site. Reclaimed wastewater might be used for some nonpotable applications, such as cooling tower make-up. An example is the Nicholas C. Metropolis Modeling and Simulation Center at Los Alamos National Laboratory (LANL) in New Mexico. The center uses treated wastewater from the LANL complex for cooling tower applications. The EPA regulates wastewater discharge but does not regulate water reuse applications or quality. There are uniform national requirements only for biological oxygen demand, total suspended solids, and pH. The National Pollutant Discharge Elimination System (NPDES) regulates all other contaminants by region and body of water. The Austin condensate recovery project: lessons learned The Texas Dept. of Transportation’s Research and Technology Center (RTC) is a 53,376-ft2 highway materials and testing laboratory in Austin. Austin’s climate features long hot summers (2907 cooling degree days) and mild winters (1737 heating degree days). The relative humidity averages 74 to 79%, depending on the season; fall is the most humid. Average annual precipitation is 32 in., according to Austin Energy. To use water more efficiently, the RTC installed a condensate recovery system in September 2002. The system was designed to recover condensate from five rooftop air-handling units. The site engineer calculated annual water recovery of 321,227 gal, with a peak flow of 218 gal/hr (gph). A measurement taken in September 2002 showed a flow rate of 199 gph. The system is designed to collect all the condensate and discharge it to the basin of the cooling tower. After two years of operation, no major impacts on the tower have been noted. The RTC system was designed to capture water in three tanks holding up to 20 gal each. The tanks were sized to reduce the cycling time of the condensate pumps. The system was installed as a retrofit at a cost of $12,774. Annual savings from the project were estimated at $2,254, which includes water and sewer fees, for a payback of six years, according to Carl Nix, RTC engineer. Here are some lessons learned from the project: • Use a polymer tank to prevent corrosion. RTC used a steel tank because it costs less, but then corrosion became a problem. AC condensate is fairly pure and thus fairly aggressive. • Hard-wire the condensate pumps to prevent nuisance tripping. The RTC pumps were connected to weather-protected ground fault interrupter receptacles to save money. But exposure to water made them trip fairly often, causing the tanks to overflow onto the roof. • When recovered condensate is used for cooling tower make-up, the system can operate at full flow because the quantity of make-up needed usually exceeds the amount of condensate recovery. • Check to see if adjustments are needed to the water treatment chemistry to compensate for higher levels of bioactive compounds and pH. Source: Austin, Texas, RTC condensate recovery project site engineer. Design considerations One of the most important ways to begin using water more efficiently is to create a water balance. A water balance shows the sources and uses of water on a site. It can be very detailed or cover only major uses; it can show usage at the whole site or in certain buildings or operations. The objective is to show where and how water is being used, what the sources are, and how much water is being disposed of. In new facilities, a balance can help designers plan equipment layouts and identify opportunities for greater efficiency. In existing facilities, it can help laboratory managers identify leaks, other losses, and possible misuses. Although it is not possible to account for every drop, well-managed facilities can usually account for 85 to 95% of the water they purchase. The first step is to document all major water-using equipment and processes at the site and usage amounts. The water quality required for each use can also be included, as well as information about the local climate, such as monthly averages for evapotranspiration rate, relative humidity, temperature, and precipitation. The second step is to determine whether known purchases equal known usage. If these two are in balance, the next step is to look for opportunities for greater efficiency in each major usage category and determine whether water from one process can be used elsewhere cost effectively. If purchases and usage do not balance, however, more investigation is needed. Often, the chief culprit is a lack of information. A thorough review can help laboratory managers fill in any missing information and discover the source of the imbalance. To find the source of an imbalance in water purchases vs. water usage: • Check grounds and facilities for obvious water or steam leaks in piping, distribution, chilled water or irrigation systems, and other equipment. • Check the main water meter at night and again in the morning to see if there is a large amount of unexplained usage that indicates a leak in the system. • Review recent utility bills (about two years’ worth) to understand trends in water use over time. • Complete a detailed survey of staff and equipment to identify or verify the principal water users and water-using equipment. • Ask researchers and facility staff how their equipment is being used, if actual usage is higher than original estimates. Fig. 2. The diagrams show how water efficiency measures at an Intel plant in Rio Rancho, N.M., have changed the way in which water flows through the facility (UPW = ultra-pure water; FAB = fabrication plant; AWN = acid waste neutralization facility). Source: New Mexico Office of the State Engineer 1999; reprinted with permission. Click here to enlarge. Fig. 2 shows a water balance for a icroprocessor plant near Albuquerque, N.M. By rethinking the water quality needs of certain applications, plant staff were able to use water discharges from one process for a number of others. For example, reject water from ultrapure water systems can be used to irrigate the grounds. Ultrapure water discharged from fabrication processes is clean enough for use in cooling towers and exhaust scrubbers. The company also implemented a number of efficiency measures within the plant to make better use of water. The plant has been able to maintain water use at about 4 million gal/day despite an increase in production of 70% (New Mexico Office of the State Engineer 1999). Design planning Laboratory designers will want to consider water uses and sources early in the design process. The following list shows where each topic discussed in this guide should be addressed in the design process. During the schematic design phase: • Identify appropriate alternative water sources. • Locate collection or storage areas. • For multibuilding campuses, design the building layout to reduce the size of the distribution system. • Include a process or cooling loop for all equipment. • Include a vacuum system. • Include condensate and chilled water return systems. During the design development phase • Identify any processes that can use water from other processes or that can supply water to processes. • Meter all major water-using processes. • Select equipment with water-saving features. Conclusion Because laboratories need more water to meet process and cooling loads, among other requirements, they usually use much more water per ft2 than conventional commercial buildings do. However, this greater usage also provides laboratories with significant opportunities to reduce their total water use by making cost-effective improvements wherever possible. Many government agencies and organizations—such as the U.S. Dept. of Energy’s Federal Energy Management Program, the Environmental Protection Agency, and the American Water Works Assn.—have published guidelines and recommendations on water efficiency for industrial, commercial, and laboratory buildings. These water efficiency guidelines can help you use less water today to ensure that the nation will have safe, secure supplies tomorrow. Stephanie Tanner at the National Renewable Energy Laboratory, Washington, D.C., 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. 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.  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 References References • American Water Works Assn. (AWWA). 1993. “Helping Businesses Manage Water Use: A Guide for Water Utilities.” Denver: AWWA. • Electric Power Research Institute (EPRI) and California Energy Commission (CEC). 2002. “Comparison of Alternate Cooling Technologies for California Power Plants: Economic, Environmental, and Other Tradeoffs.” Palo Alto, CA: EPRI; Sacramento, CA: CEC. Available at http://www.energy.ca.gov/reports/2002-07-09%5F500-02-079F.PDF. Accessed August 2004. • Federal Energy Management Program. June 2004. “Saving Energy, Water and Money with Efficient Water Treatment Technologies, A FEMP Technology Focus.” DOE/EE-0294. Washington, DC: U.S. Dept. of Energy. • Hoffman, Bill. Coordinator—Commercial Industrial Programs, City of Austin, TX, water department. • Krupnick, Stu. July 2000. “Realizing Chillers’ Capabilities in Laboratories.” Process Cooling and Equipment, a supplement to Process Heating Magazine. Available online at http://tinyurl.com/ n7q36. Accessed August 2004. • New Mexico Office of the State Engineer. July 1999. “A Water Conservation Guide for Commercial, Institutional and Industrial Users.” Albuquerque, NM: Office of the State Engineer. Available online at www.ose.state.nm.us/water-info/conservation/pdf-manuals/cii-users-guide.pdf n7q36 Accessed August 2004. • New York City Dept. of Environmental Protection. 2003. “New York City Drinking Water Supply and Quality Report.” Available online at www.nyc.gov/html/dep/ html/wsstate.html. Accessed August 2004. • Puckorius, Paul. November 2002. “Water Conservation Via Optimizing Water Use.” Process Cooling and Equipment, a supplement to Process Heating Magazine. Available online at http://tinyurl.com/ hxnm3. Accessed August 2004. • Tanner, Stephanie, Eva Urbatsch, and Anna Hoenmanns. 2003. “Water Efficiency Plan.” Internal Publication. Golden, CO: National Renewable Energy Laboratory. • Texas Water Development Board. 1997. “Texas Guide to Rainwater Harvesting, Second Edition.” Austin: Texas Water Development Board. • Van Gelder, Roger E. 2004. “Field Evaluation of Three Models of Water Conservation Kits for Sterilizer Trap Cooling at University of Washington.” Presented at the 2004 Water Sources Conference & Exposition, January 11–14, Austin, TX. • Vickers, Amy. 2001. Handbook of Water Use and Conservation. Amherst, MA: Water Plow Press. • Wilcut, Eddie, and Brian Lillibridge. 2004. “Condensate 101—Calculations and Applications.” Presented at the 2004 Water Sources Conference & Exposition, January 11-14, Austin, TX. Additional resources • Federal Energy Management Program. “Best Management Practices for Water Conservation at Federal Facilities.” Washington, DC: U.S. Dept. of Energy. Available online at www.eere.energy.gov/ femp/technologies/water_fedrequire.cfm. Accessed August 2004. • North Carolina Dept. of Environment and Natural Resources’ Div. of Pollution Prevention and Environmental Assistance, “Water Efficiency: Water Management Options.” Available online at www.p2pays.org/ref/04/03101.pdf. Accessed September 2004. • U.S. Dept. of Defense. “Military Handbook 1165: Water Conservation.” Washington, DC: DoD, 7 April 1997. Available online at https://energy.navy.mil/ publications/water/mil_hdbk_1165.pdf. Accessed August 2004.