How to Conserve Water and Use It Effectively
How to Conserve Water and Use It Effectively
Government Web site
Source: U.S. Environmental Protection Agency. "How to Conserve Water and Use It Effectively." 〈http://www.epa.gov/ow/you/chap3.html〉 (accessed January 17, 2006).
About the Organization: The U.S. Environmental Protection Agency (EPA) is a federal agency that was established by the U.S. Congress in 1970. The EPA develops and enforces environmental regulations; performs research; funds state and local environmental partnerships and programs; promotes environmental education; and publishes information and guidelines for the public.
The EPA—whose assignment is to regulate and reduce air, water, noise pollution, and pollutions concerning pesticides, radiation, and various other toxic materials—offers a number of water-related Internet sites in order to increase public awareness with the issues and problems relating to water quality throughout the United States. One such EPA site that emphasizes water concerns is called "Cleaner Water Through Conservation." By providing important conservation information about water, the EPA encourages involvement in water quality issues by individuals, conservation and environmental groups, and other interested parties. An especially important chapter within the site is called "How to Conserve Water and Use It Effectively," which outlines practices for industrial and commercial users, specifically discussing a number of conservation and water use efficiency practices—from both an engineering and behavioral standpoint—available within that sector.
HOW TO CONSERVE WATER AND USE IT EFFECTIVELY
Practices for Industrial/Commercial Users Industrial/commercial users can apply a number of conservation and water use efficiency practices. Some of these practices can also be applied by users in the other water use categories.
Engineering Practices Water Reuse and Recycling Water reuse is the use of wastewater or reclaimed water from one application such as municipal wastewater treatment for another application such as landscape watering. The reused water must be used for a beneficial purpose and in accordance with applicable rules (such as local ordinances governing water reuse). Some potential applications for the reuse of wastewater or reclaimed water include other industrial uses, landscape irrigation, agricultural irrigation, aesthetic uses such as fountains, and fire protection (USEPA, 1992). Factors that should be considered in an industrial water reuse program include (Brown and Caldwell, 1990):
- Identification of water reuse opportunities
- Determination of the minimum water quality needed for the given use
- Identification of wastewater sources that satisfy the water quality requirements
- Determination of how the water can be transported to the new use
The reuse of wastewater or reclaimed water is beneficial because it reduces the demands on available surface and ground waters (Strauss, 1991). Perhaps the greatest benefit of establishing water reuse programs is their contribution in delaying or eliminating the need to expand potable water supply and treatment facilities (USEPA, 1992). Water recycling is the reuse of water for the same application for which it was originally used. Recycled water might require treatment before it can be used again. Factors that should be considered in a water recycling program include (Brown and Caldwell, 1990):
- Identification of water reuse opportunities
- Evaluation of the minimum water quality needed for a particular use
- Evaluation of water quality degradation resulting from the use
- Determination of the treatment steps, if any, that might be required to prepare the water for recycling
Cooling Water Recirculation The use of water for cooling in industrial applications represents one of the largest water uses in the United States. Water is typically used to cool heat-generating equipment or to condense gases in a thermodynamic cycle. The most water-intensive cooling method used in industrial applications is once-through cooling, in which water contacts and lowers the temperature of a heat source and then is discharged.
Recycling water with a recirculating cooling system can greatly reduce water use by using the same water to perform several cooling operations. The water savings are sufficiently substantial to result in overall cost savings to the industry. Three cooling water conservation approaches that can be used to reduce water use are evaporative cooling, ozonation, and air heat exchange (Brown and Caldwell, 1990).
In industrial/commercial evaporative cooling systems, water loses heat when a portion of it is evaporated. Water is lost from evaporative cooling towers as the result of evaporation, drift, and blowdown. (Blowdown is a process in which some of the poor-quality recirculating water is discharged from the tower in order to reduce the total dissolved solids.) Water savings associated with the use of evaporative cooling towers can be increased by reducing blowdown or water discharges from cooling towers.
The use of ozone to treat cooling water (ozonation) can result in a five-fold reduction in blowdown when compared to traditional chemical treatments and should be considered as an option for increasing water savings in a cooling tower (Brown and Caldwell, 1990).
Air heat exchange works on the same principle as a car's radiator. In an air heat exchanger, a fan blows air past finned tubes carrying the recirculating cooling water. Air heat exchangers involve no water loss, but they can be relatively expensive when compared with cooling towers (Brown and Caldwell, 1990).
The Pacific Power and Light Company's Wyodak Generating Station in Wyoming decided to use dry cooling to eliminate water losses from cooling-water blowdown, evaporation, and drift. The station was equipped with the first air-cooled condenser in the western hemisphere. Steam from the turbine is distributed through overhead pipes to finned carbon steel tubes. These are grouped in rectangular bundles and installed in A-frame modules above 69 circulating fans. The fans force some 45 million cubic feet per minute (ft3/min) of air through 8 million square feet of finned-tube surface, condensing the steam (Strauss, 1991).
The payback comes from the water savings. Compared to about 4,000 gallons per minute (gal/min) of makeup (replacement water) for equivalent evaporative cooling, the technique reduces the station's water requirement to about 300 gal/min (Strauss, 1991).
Rinsing Another common use of water by industry is the application of deionized water for removing contaminants from products and equipment. Deionized water contains no ions (such as salts), which tend to corrode or deposit onto metals. Historically, industries have used deionized water excessively to provide maximum assurance against contaminated products. The use of deionized water can be reduced without affecting production quality by eliminating some plenum flushes (a rinsing procedure that discharges deionized water from the rim of a flowing bath to remove contaminants from the sides and bottom of the bath), converting from a continuous-flow to an intermittent-flow system, and improving control of the use of deionized water (Brown and Caldwell, 1990).
Deionized water can be recycled after its first use, but the treatment for recycling can include many of the processes required to produce deionized water from municipal water. The reuse of once-used deionized water for a different application should also be considered by industry, where applicable, because deionized water is often more pure after its initial use than municipal water (Brown and Caldwell, 1990).
Landscape Irrigation Another way that industrial/commercial facilities can reduce water use is through the implementation of efficient landscape irrigation practices. There are several general ways that water can be more efficiently used for landscape irrigation, including the design of landscapes for low maintenance and low water requirements (refer to the previous section on xeriscape landscaping), the use of water-efficient irrigation equipment such as drip systems or deep root systems, the proper maintenance of irrigation equipment to ensure that it is working properly, the distribution of irrigation equipment to make sure that water is dispensed evenly over areas where it is needed, and the scheduling of irrigation to ensure maximum water use (Brown and Caldwell, 1990). For additional information on efficient water use for irrigation, refer to the practices for residential users and agricultural users in this chapter.
Behavioral Practices Behavioral practices involve modifying water use habits to achieve more efficient use of water, thus reducing overall water consumption by an industrial/commercial facility. Changes in behavior can save water without modifying the existing equipment at a facility.
Monitoring the amount of water used by an industrial/ commercial facility can provide baseline information on quantities of overall company water use, the seasonal and hourly patterns of water use, and the quantities and quality of water use in individual processes. Baseline information on water use can be used to set company goals and to develop specific water use efficiency measures. Monitoring can make employees more aware of water use rates and makes it easier to measure the results of conservation efforts. The use of meters on individual pieces of water-using equipment can provide direct information on the efficiency of water use. Records of meter readings can be used to identify changes in water use rates and possible problems in a system (Brown and Caldwell, 1990).
Many of the practices described in the section for residential users can also be applied by commercial users. These include low-flow fixtures, water-efficient landscaping, and water reuse and recycling (e.g., using recycled wash water for pre-rinse).
Scientists working for the EPA are very concerned with improving water quality throughout the United States. Although water quality has improved in most regions of the country since 1970 (the year that the EPA was created), there are always problems associated with maintaining a safe supply of water for humans, along with other living animals and plants. When the quality of water becomes degraded in a particular area, the cause is often diffuse, or non-point source (NPS), pollution. NPS pollution is the type of pollution that results when no specific source of pollution is identified from widespread activities. Examples of non-point pollution include urban run-off of substances such as grease, oil, and road salt and agricultural run-off of materials such as fertilizers and pesticides. Other NPS examples include acid rain (such as toxic airborne particles), changes in the natural flow of water in streams and rivers (such as dams), and failures of disposal systems (such as septic systems).
When such NPS water pollution happens, hydrological EPA scientists have proven that the application of a water conservation program along with a pollutant source reduction program is a good way to control pollution. An example of a pollutant source reduction program includes the use of an appropriate system of pesticide and nutrient management.
Along with the use of such pollutant source reduction programs, the quality of water can be further enhanced by the conservation of water. When conservation programs are instituted, the quantity of water is increased—which directly leads to an improvement in the quality of the water. Reductions in the use of water lead to such improvements as the renewal of dried-up wetlands, minimization of agricultural runoff, and the general renovations of environmental habitats.
As of the beginning of 2005, over forty U.S. states use some program based on water conservation and more than 80 percent of U.S. water utility customers use some type of water conservation measure such as water restriction/water pressure reduction plans, zoning ordinances, and pricing policies based on usage or other means. One such resource program provided by the EPA is "A Guide to Cleaner Water Through Conserving Water," which provides information to protect water quality. Such topics included within the program are effects from excessive water use from non-point source pollution, overall trends in water usage, and examples of various environmental programs.
Of particular interest to this discussion is the section on various technical conservation methods that help to reduce water use and, as a result, protect the quality of water in the United States. In this section, EPA writers have described many different water-use practices based on updates in plumbing, fixtures, and operating procedures, along with ways that are scientifically proven to more efficiently use water. Part of this discussion involves how agricultural, industrial, residential, and system operator users are able to conserve water.
Since many U.S. citizens work in industrial and commercial areas, it is of particular interest to note the various ways that company officials can conserve water. Water provided for industrial use includes such purposes as cooling, diluting, fabricating, processing, transporting, and processing a product, along with including water into the production of a product and using water as a sanitary device within an industrial facility.
Information provided by the EPA with regard to ways to conserve water in the industrial/commercial sector of the U.S. economy is important to the overall health of water in the country. In 2000, the U.S. Geological Survey (USGS) estimated that the use of water for industries in the United States totaled about 19.7 billion gallons (74.6 billion liters) each working day. This amount was about 11 percent more than in 1995. Surface water was used for about 82 percent of those industrial uses while ground water was used for the other 18 percent. In nearly both cases (92 percent for surface water and 99 percent for ground water), fresh water was used most often.
The states of Louisiana, Indiana, and Texas together used 38 percent of all water for industrial purposes. Louisiana consumed the most industrial water of any state, primarily for its chemical and paper industries. Other U.S. states with high consumption of industrial water are Michigan, Ohio, Pennsylvania, West Virginia, Tennessee, Alabama, Georgia, and Washington.
It is important, for many reasons, that the EPA continue to supply information related to the efficient use of water through conservational means to residential, industrial, and agricultural consumers. The EPA possesses the expertise and knowledge to deal with the problems and issues that occur from a small town to a particular section of the country and beyond the physical boundaries of the United States. With such valuable information provided by the EPA, consumers are better equipped to deal with pollution and better informed on the wise use of water.
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―――――――"Cleaner Water Through Conservation." 〈http://www.epa.gov/ow/you/intro.html〉 (accessed January 17, 2006).