Water Efficiency May 2012 : Page 36
“We must make infrastructure choices and change our use behavior,” he says. “We have to match supply to use.” But Carpenter proposes an optional solution to the dual-distribution system. “There used to be a separate purple pipe system [for recycled wa-ter]. Those pipes are made of PVC—an oil-based product. A separate system involves economic, environmental, and social aspects; it monetizes ele-ments of reuse.” Increasingly, he says, utilities consider separate systems as a way to deploy supply, which cause disruption of the environment and commerce. “Why not put [recycled water] in the aquifer?” ponders Carpenter. “Wastewater is a more reliable source than river water, even in a drought.” Acknowledging what he calls the “yuck factor,” Carpenter says using recycled wastewater is no different from breathing the same air molecules others have exhaled or using a fork in a restaurant that was previously used by other diners. “We all live downstream from something; the pristine spring doesn’t exist anymore,” he says. But the technology to treat water to whatever level is required to keep people safe does exist, and several communities have embraced it. Carpenter mentions a full potable reuse project in Big Springs, TX, that conveys wastewater to a water treat-ment plant where effluent is treated to drinking water standards. JOJO WOULDN’T LEAVE HIS HOME IN TUCSON NOW One community incorporating recycled wastewater in their program is the desert city of Tucson, AZ. As explained by John Kmiec, environ-mental and regulatory compliance supervisor for Tucson Water, the region’s water table was going down, due to agriculture and urban growth. Tucson features one of the region’s largest groundwater utilities, drawing its available water from two aquifer basins because no surface water to pull from is available. In an area that sees only 10 inches of rain annually, concern about pumping groundwater led to the realization that a removable water supply was needed. The Central 36 WATER EFFICIENCY WWW.WATEREFFICIENCY.NET GLOBAL WATER Public education can Arizona Project of 1968 encourage diverted water from public conservation. the Colorado River to the state, but it didn’t resolve the problem entirely. “It doesn’t matter how much it rains in Tucson now,” says Kmiec. “It matters how much it snows in Colorado.” In 1984, a reclaimed water program was launched. Raw wastewater was delivered to the Pima County treatment plant, then returned to Tucson Water for tertiary treatment—polishing, as Kmiec describes it—in one of two ways: pres-sure fi ltration or soil aquifer treatment. Th e purpose of the reclamation system was to get users off the potable groundwater supply, Kmiec explains. Currently, Tucson Water diverts 16,000 acre-feet of water to 1,000 custom-ers—primarily golf courses, parks and schools, although 700 single-family residences also use the system. “We learned that traditional turf areas like parks and golf courses give the biggest bang for the buck,” he says. Economic factors in neighborhoods already conserving make the addition of a dual system for reclaimed water impractical. “People don’t want to tear up the streets for a second pipe and pay protection for backfl ow, especially in neighborhoods where the HOA has GLOBAL WATER banned grass, so there’s no need to ir-rigate,” says Kmiec. By diversifying their portfolio with guidance from Carollo Engineers, Tucson Water assures its customers of a reliable source of water. “Recharge from the Colorado River is climate-dependent,” he explains. “Re-charge from reuse is climate-independent.” MANAGING THROUGH MEASUREMENT Tuscon’s solution is a system more cities will have to consider, Carpenter
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