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, 56 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.

Use of Treated Effluent
APS is one of the largest users of treated effluent in the United States for use in power generation. This significantly reduces the amount of surface and groundwater required in our generation activities. As shown in the chart below, in 2006 over 56 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.

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 new 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.

APS has also been able to reduce water use in power plant generation over the past two years as a result of higher capacity factors (leading to better resource efficiency) at our coal plants, and the addition of several new, more efficient natural-gas generation units.

Other Water Conservation Efforts
APS also incorporates water conservation and use ideas into facility building and maintenance as part of our participation in the LEED program.