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Water is a precious resource in the Southwest, and APS' facilities strive to minimize water usage through a variety of water-conservation activities and through use of treated effluent as a water source. In fact, 60 percent of all water used by APS is treated effluent as discussed in the section below. APS' major use of water is in electricity generation.
Our SunCor affiliate also has numerous water conservation efforts in place, which are discussed in the Subsidiary section of this report.
One of our major water conservation methods is to use treated effluent for our water source in power generation at our Redhawk and Palo Verde power plants. APS is one of the largest users of treated effluent for power generationin the United States. This significantly reduces the amount of potable surface and groundwater required in our generation activities. As shown in the chart below, in 2007 over 60 percent of our total power plant water came from treated effluent. At the Palo Verde Nuclear Generating Station and our Redhawk natural gas-powered facility, we use treated effluent purchased from seven cities in the Phoenix metropolitan area for cooling. A 35-mile pipeline carries treated waste water from a City of Phoenix sewage treatment facility to Palo Verde, where we use an advanced waste-water treatment process capable of preparing 90 million gallons of water each day for use at both Palo Verde and Redhawk.
Each year, Palo Verde's water reclamation facility processes about 20 billion gallons of treated effluent for power plant use, preserving enough potable water for about 75,000 homes.
The above chart is based on a total water use of 35,465 million gallons (111,907 acre-feet) in 2007.
Another way in which APS conserves water is through careful water chemistry and treatment. This allows for a high level of water recycling in our electricity-generation process. We reuse our water supplies as much as possible to avoid wasting water, however, some water must be discharged (this is called "blowdown water") to control the salinity of the water used in the power plant processes.
Water use was also an important consideration in the design of our newest power plants, and APS strived to incorporate water conservation measures in these new plants, resulting in power plants that utilize less water per MWh generated. The type of cooling system used in new plants is critical to the amount of water used, and APS is committed to using dry or hybrid cooling in new power plants whenever feasible.
APS has also been able to reduce water use in power plant generation over the past several years. However, in 2007, the water use increased slightly, primarily due to operational issues at our Four Corners Power Plant. Two factors increased the water use at this plant. One was the increased removal of SO2 by the air pollution control equipment. This equipment required more water to function properly. In addition, there were mechanical problems at Unit 5 that caused this unit to produce less power than normal. The result is the overall water use at the plant increased because proportion of power produced by the older units 1, 2 and 3 increased. These units are not as efficient as the newer units 4 and 5. The problems at unit 5 have been corrected.
APS also incorporates water conservation and use ideas into facility building and maintenance as part of our participation in the LEED program, and practices other water conservation measures at our office facilities, such as the use of waterless urinals in our corporate headquarters building, and the replacement of grass with desert landscaping at some other facilities.
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