LOCAL GOVERNMENTS TAKE ACTION
Although local governments can’t control the construction of new federal water projects to quench their cities’ insatiable thirsts, they can control how much water is used at the local level. Plumbing and building codes play an important role in governing water use. Local jurisdictions adopt the Uniform Plumbing Code or International Plumbing Code as local ordinances or laws and are free to adapt to local conditions. Such adaptations include permitting waterless urinals or allowing non-potable water to be used for sewage conveyance in buildings. Plumbing standards, established through consensus-based processes, focus on the water efficiency of specific plumbing fixtures, such as toilets, urinals, showerheads and faucets. Building officials also can foster water efficiency through adoption of ordinances that favor or require green-building programs, such as the Washington, D.C.-based U.S. Green Building Council’s LEED program. LEED offers five waterefficiency credits: two for reducing potable-water use for irrigation, one for reducing potable-water use for sewage conveyance and two for reducing potable-water use inside a building.
RECLAIMED WATER Purple is the standard color adopted by the international utility industry for pipe that distributes municipally treated, reclaimed or recycled water. Many communities are using reclaimed water to irrigate food crops, parks, schools, golf courses, street medians and business-park landscaping. It’s also used for cooling buildings, industrial processes and paper manufacturing. The San Jose, Calif.-based South Bay Water Recycling, or SBWR, program has been serving Silicon Valley communities for more than 10 years. It has helped conserve more than 23 billion gallons (87 billion L) of drinking water, or enough to supply more than 100,000 households for one year. During the summer months, an average of 15 million gallons (57 million L) of recycled water are produced and distributed to more than 550 customers per day. The system consists of more than 100 miles (161 km) of pipeline, five pump stations and 10 million gallons (38 million L) of storage in reservoirs.
The Santa Clara Water District—one of several agencies involved with the SBWR—has identified that 10 percent of the total water supply for the county must come from recycled water. Another reclaimed water program in California, the Orange County Groundwater Replenishment System, helps meet several important goals for participating jurisdictions. The reclaimed water helps replenish the groundwater basin and protect it from seawater intrusion. It also decreases Orange County’s reliance on imported water from northern California and the Colorado River. Built at an estimated capital cost of $485 million, the project began producing 72,000 acre feet of water per year in January 2008. (One acre foot of water is 326,000 gallons [1.2 million L].) It takes highly treated sewer water from the Orange County Sanitation District and treats it to beyond drinking-water standards, using advanced microfiltration.
During the process, treated sewer water passes through fibers that work as microscopic filters. Each fiber filters particles up to 0.2 microns in size, or about 1/300th the size of human hair. Bacteria, protozoa and some viruses remain outside the filter while clean water passes through. The low-energy microfiltration pretreats the water before it passes through reverseosmosis membranes. Approximately half of the treated water is stored in percolation basins to help replenish the groundwater. The other half is injected into the local seawater intrusion barrier to create a dam of pressurized pure water that prevents saltwater from contaminating Orange County’s existing groundwater.
California is not the only state tackling its watersupply future. Florida, Hawaii and Texas, among others, have started to develop large-scale seawater, or brackish, water-desalination plants to provide a source of potable water. The largest inland desalination plant recently opened in El Paso, Texas. The $87 million facility produces 27.5 million gallons (104 million L) of drinking water per day drawing brackish groundwater. Brackish water has more salinity than freshwater, but not as much as seawater. With the new plant, El Paso’s drinking-water production grew by 25 percent and is expected to supply the area with water for the next 50 years. To further develop desalination technologies, the University of Texas at El Paso recently opened the Center for Inland Desalination Systems. The most notable development in U.S. desalination was the recent approval of a 50-million-gallon- (189-million-L-) per-day facility in Carlsbad, Calif. With construction expected to start this year, the plant will produce high-quality drinking water and serve 300,000 residents annually.
Nine San Diego public agencies from throughout the county have signed 30-year water-purchase agreements. Using an efficient ultra-filtration membrane, the Carlsbad plant will use less energy to produce drinking water for one household than the equivalent energy consumed by that household’s refrigerator. Just up the California coast, the 50 mgd Huntington Beach Desalination Plant is co-located with a power plant to take advantage of intake and discharge infrastructure. Water from the plant will cost $2.70 to $2.90 per 1,000 gallons (3785 L). Although higher than the cost of imported water, it provides a cost-effective, long-term, stable supply of water to the community. Every gallon of water that is conserved or reclaimed after use means one less gallon that must be captured, stored, shipped and treated. Desalination and other water-treatment technologies help redefine the concept of potable water while giving local governments the ability to address the challenges of population growth and climate change. In this era of water-supply uncertainty, it’s important to remember to think globally, drink locally.
SCOTT FLORIDA writes about architecture and sustainability from Oakland, Calif.