Water Use Backgrounder
The Big Picture
In the United States, approximately 340 billion gallons of fresh water are withdrawn every day from rivers, streams, and reservoirs to support residential, commercial, industrial, agricultural, and recreational activities. This accounts for about one-fourth of the nation’s total supply of renewable fresh water. Almost 65% of this water is discharged into rivers, streams and other water bodies after use and, in some cases, treatment.
Using large volumes of water increases maintenance and lifecycle costs for building operations and increases consumer costs for municipal supply and treatment facilities. Conversely, reductions in water use can lead to more stable municipal taxes and water rates. By handling reduced water volumes, water treatment facilities can delay expansion and maintain stable water prices.
Water efficiency measures in commercial buildings can easily reduce water usage by 30% or more, according to some estimates. In a typical 100,000-square-foot office building, low-flow fixtures coupled with sensors and automatic controls can save a minimum of one million gallons of water per year, based on 650 building occupants each using an average of 20 gallons per day. Non-potable water volumes can be used for landscape irrigation, toilet and urinal flushing, custodial purposes, and building systems. Utility savings, though dependent on local water costs, can save thousands of dollars per year, resulting in rapid payback on water conservation infrastructure.
Finally, landscape irrigation practices in the United States consume large quantities of precious potable water. Irrigation typically uses potable water, although water volumes of lower quality water (i.e., non-potable water) are equally effective for irrigating landscapes. High-efficiency irrigation systems can help reduce potable water use for irrigation. Sources of non-potable water volumes include captured rainwater from roof runoff, gray water from building systems (e.g., sinks and showers), and the municipal recycled water supply system.
Context
The Energy Policy Act of 1992 established water conservation standards for water closets, shower heads, faucets, and other uses to save the United States an estimated 6.5 billion gallons of water per day. Toilet flushing uses the most water in residential and commercial buildings, accounting for approximately 4.8 billion gallons per day. Older toilets use four to eight gallons of water per flush, while all new toilets must have a maximum flush volume of 1.6 gallons.
To meet increased demand, makers of bathroom fixtures began producing low-flow fixtures and alternative-system fixtures for installation everywhere from residential and commercial buildings to onboard cruise ships. Some of these include waterless urinals, dual-flush and composting toilets, low-flow toilets, sinks and showerheads, and sensors for operation of sinks and for flushing toilets.
While the Act is a good starting point, there are many other ways to exceed this standard and achieve even greater water savings. Other effective methods of reducing potable water use include reusing roof runoff volumes for non-potable applications, using industrial wastewater or gray water from bathroom sinks to flush toilets, collecting rainfall in onsite cisterns, and water-efficient landscape irrigation.
Commercial and industrial facilities that generate large amounts of wastewater can realize considerable savings by recycling gray water. Gray water consists of wastewater from lavatories, showers, washing machines, and other building activities that do not involve human waste or food processing. For example, carwashes and truck maintenance facilities generate large volumes of gray water that can be effectively treated and reused. These gray water volumes can be stored in cisterns. Also, storm water volumes can be collected from hardscape surfaces on the site, such as roofing, and used in the landscape irrigation system.
Low-flow fixtures, automatic controls, and dry fixtures such as composting toilets and waterless urinals can be used to reduce sewage volume generation.
Getting Down to Business
Here are some examples of how effective water management has paid off for companies and government agencies across the globe.
- Technology giant IBM has implemented an environmental policy that requires their offices and plants to monitor water usage and use less water wherever possible. One of their methods included reusing treated sanitary wastewater for irrigation at its Guadalajara plant.
- New York City invested $393 million in a 1.6 GPF toilet-rebate program that has reduced water demand and wastewater flow by 90.6 million gallons per day, equal to 7% of the city’s total water consumption. The rebate program accomplished a net present value savings of $605 million from a 20-year deferral of water supply and wastewater treatment expansion projects.
- Another successful water efficiency program was instituted in Santa Monica, Calif. , where a toilet replacement program achieved permanent reductions in water usage and wastewater flows of over 1.9 million gallons per day, representing a 15% reduction in average total water demand and a 20% reduction of average total wastewater flow. The cost of the rebate program was $5.4 million. The program had a net savings of $6 million in the year 2002 due to avoided costs of water imports and wastewater treatment.
- Gangi Brothers Packing Company, a tomato processing and canning plant in Santa Clara, Calif., implemented several successful water conservation practices at its cannery, including the monitoring of operations to control water use and to identify areas where water could be saved. In 1983 Gangi Brothers used approximately 148 billion gallons of water during the canning season. By 1989 water use at the facility had dropped to 56.8 billion gallons, resulting in a savings of 91.2 billion gallons per season. Combined estimated capital and operating costs for water conservation at Gangi Brothers are approximately $89,500 per year. The estimated savings from lower sewer and water costs is $130,000 per year, so the net savings resulting from the implementation of water conservation practices at the cannery is approximately $40,500 per year (1990 dollars).
- The Pacific Power and Light Company’s Wyodak Generating Station in Wyoming uses dry cooling to eliminate water losses from cooling-water blowdown, evaporation, and drift. The station was equipped with an air-cooled condenser—steam from the turbine is distributed through overhead pipes to finned carbon steel tubes leading to 69 circulating fans. The fans force some 45 million cubic feet per minute of air through 8 million square feet of finned-tube surface, condensing the steam. This system reduced water use from about 4,000 gallons per minute of replacement water for equivalent evaporative cooling to about 300 gallons per minute.
Key Players
- Landscape architects can design outdoor areas using native plants or plants that require very little water. Using plants that can be sustained by the area’s average rainfall (xeriscaping) eliminates the need for irrigation.
- State and local governments increasingly are offering incentives to help companies adopt water-saving techniques and technologies.
- Water utilities are offering help to companies to conserve water, including providing grants and loans to help industrial and commercial customers pay for water-saving technologies.
- Market-making water brokers are developing new kinds of business opportunities, such as competitive bidding, in which consumption levels are set by a supplier and customers bid for a chance to meet it by implementing any of a variety of cost-effective water-efficiency techniques.
The Upside
Lower water bills. Utility rates for potable water are expected to escalate in future years as a result of over-consumption and finite potable water resources. Implementing successful water-efficiency strategies can minimize the amount of potable water that a municipality must provide, thereby leading to more stable water rates.
Lower sewerage and water connection fees from municipal agencies. Facilities that use water efficiently can reduce costs through lower water use fees, lower sewage fees, energy and chemical use reductions, and lower capacity charges and limits.
Reality Check
Water-conserving fixtures that use less water than required by the Energy Policy Act of 1992 may have higher initial costs. For example, the first cost of composting toilets is significantly higher than conventional water closets and they may initially require additional maintenance attention. Some composting toilets also carry an ongoing energy cost to run fans and other system equipment. Nonetheless, significant operational savings are realized through eliminated potable water use and sewage generation.
Wastewater treatment systems and water recovery systems also involve an initial capital investment, in addition to maintenance required over the building’s lifetime. These costs must balance with the anticipated savings in water and sewer bills.
In addition, the characteristics of an existing building may dictate water reuse strategies. Implementing water efficiency measures into existing buildings may be limited due to space constraints or existing plumbing fixtures. In addition, the necessity and availability of wastewater reuse and treatment strategies is heavily influenced by the building’s location. In remote locations, it may be cost effective to use an onsite wastewater treatment system.
Finally, implementing water-saving features can be a hard sell with higher-ups because such measures may incorporate new or unfamiliar technologies. Educating local inspectors or governments may be a challenge, as well, as different systems may have different implications for building codes. Communication with government officials early on to get the plans approved and the systems installed on schedule.
Action Plan
Water use strategies depend on site location and site design. Here are some practical approaches to making effective water management work for your company.
- Reduce use. Currently, the most effective strategy to avoid escalating water costs is simply to use less potable water.
- Develop a water use inventory that includes all water-consuming fixtures, equipment, and seasonal conditions to identify significant potable water demands and determine methods to minimize or eliminate these demands.
- Specify water-conserving plumbing fixtures that exceed the fixture requirements stated in the Energy Policy Act of 1992. Consider ultra-high efficiency fixture and control technologies, including toilets, faucets, showers, dishwashers, clothes washers, and cooling towers. A variety of low-flow plumbing fixtures and appliances are currently available in the marketplace and can be installed in the same manner as conventional fixtures.
- Develop a wastewater inventory and determine areas where gray water can be used for functions that are conventionally served by potable water. These functions might include sinks, showers, toilets, landscape irrigation, industrial applications, and custodial applications. Also estimate demand for these applications and the availability of gray water generated on the site. Finally, determine the amount of wastewater that will require treatment and select the most suitable treatment strategy.
- Consider an onsite wastewater treatment system such as constructed wetlands, a mechanical recirculating sand filter, or an aerobic biological treatment reactor. Onsite wastewater treatment systems transform perceived “wastes” into resources that can be used on the building site. Reducing the treatment required at the local wastewater treatment plant minimizes public infrastructure, energy use, and chemical use.
- Consider installing a roof-water or groundwater collection system. Use metal, clay, or concrete-based roofing materials and take advantage of gravity flows whenever possible. However, roofs made of asphalt or lead-containing materials can contaminate collected rainwater and render it undesirable for reuse.
- Check with local health departments for guidelines regarding the collection of rainwater, since such collection is not federally regulated. If collected rainwater is to be used for potable or irrigation purposes, certain health codes may require back-flow prevention devices to avoid the risk of contaminating public drinking water supplies.
- Check with the local health department for regulations governing the use of a gray water system and the permits required. Each state has its own standards for gray water irrigation systems.
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- Rethink your landscaping plans by monitoring how much water you use. Can those plants be replaced with ones that require less water? Could the lawn be watered once a week instead of every day, or not at all?
- Stay current on new technologies. Investigate products or systems that can help lower or eliminate water consumption. Research the availability of waterless urinals, dual-flush toilets, composting toilets, manual or electronic sensors to activate sinks, and low-flow showerheads.
Leads
- Water and Wastewater Equipment Manufacturer Association
Works closely with industry and governmental groups to shape environmental laws and regulations. - National Onsite Wastewater Recycling Association, Inc.
Advances and promotes the onsite waste-water industry. - Facility Manager’s Guide to Water Management
A comprehensive guide to a broad spectrum of water-management issues, from plumbing fixtures to cooling towers to landscaping. - Water Reuse Association
Promotes water recycling through research, education, and loan programs. - Water Efficiency and Management in Commercial Buildings
Suggests a multitude of ways that commercial buildings can reduce water consumption. - Operation, Maintenance, and Management of Stormwater Management Systems
An overview of how to safely build and operate stormwater-management systems.
Bottom Line
As water use and allocation becomes a topic of growing concern around the world, companies will be required to better scrutinize the ways water is used in their operations. Fortunately, there is a great deal of information and experience for reducing water use in a cost-efficient manner. As a result, water-conserving businesses enjoy more than environmental benefits. They also enjoy the cost-saving efficiencies of a well-run operation.