'Our Drinking Water Will Come From...Where?'
Bottled water isn't the answer for everyone. Fast-growing localities are tapping everything from seawater to wastewater.
Casting its eye to the Pacific Ocean, the San Diego County Water Authority thought it saw the solution to its drinking water woes. If a plant could be built to remove salt from the bright blue waters just beyond the county's beaches, the utility's 3 million customers would have a reliable, local source of drinkable water.
That was 10 years ago, when Southern California was suffering through half a decade of drought. But the plan came to naught: Experts at the time calculated that desalinated seawater would cost as much as $6 for a thousand gallons, and the county turned to other strategies.
Now, the dearth of drinkable water is back, and the problem is bigger and more widespread than ever. In Southern California, a day of reckoning is approaching as federal-state agreements cut back the amount of water cities have been drawing for decades from the overtaxed Colorado River. San Diego now depends on imported water from the Colorado and Northern California rivers for 90 percent of its needs, and regional water supply officials have no choice but to find new supplies closer to home.
Beyond California, governments in the rapidly growing Sun Belt already foresee an inability to keep delivering water as promised over the next few decades. In other parts of the country--including the Northeast--prolonged dry spells during the past decade have forced municipal agencies to impose restrictions on watering lawns and washing cars to conserve enough water for drinking and cooking.
To stretch existing supplies, water utilities around the country have come up with long-term conservation strategies. Some offer financial assistance to help customers install low-flow showers and toilets and practice water-saving landscaping. Some cities have also begun installing duplicate reclaimed water systems that can pump treated sewage effluent to water golf courses and parks and supply factory machinery.
Those efforts have paid off, but in many metropolitan regions, it's not enough. "Even with conservation, even with reclamation, we still were falling short," says Pinellas County Commissioner Robert B. Stewart, of the situation in his part of Florida. To overcome that shortfall, his area is doing what San Diego had hoped to do 10 years ago: The Tampa Bay regional water supplier is getting ready to operate a $110 million project that will turn salty bay water into 25 million gallons of potable drinking water a day.
Tampa Bay is not the only region to take a serious look at making a major investment in turning undrinkable water--seawater, brackish water or "previously used" water--into the potable stuff. Technological improvements over the last decade are making these approaches feasible. Desalinization costs, for instance, have been cut in half. Nonetheless, the investment of millions of dollars in alternative sources of water is not always an easy--or politically popular--step to take.
LIMITS ON POSSIBILITIES
When water supplies run short, communities drill deeper wells or dam streams to store reserves. But groundwater tables have fallen as consumption has grown, and dams, reservoirs and pipelines have already been built at the most productive sites for capturing surface waters.
Some urban areas have turned to imports--bringing in water from distant rivers and lakes. But this has increasingly raised environmental issues and stirred formidable political resistance from rural communities. Just this September, for instance, the North Central Texas water planning board balked at damming the Sulphur River to form a 72,000-acre reservoir to supply water to the Dallas-Fort Worth metropolitan area.
Even in rainy Florida, cities are bumping up against resource limits. Around Tampa Bay, pumping groundwater to supply 2 million people in Tampa, St. Petersburg and three rapidly developing counties has lowered water tables and begun drying up wetlands that are critical to the bay's ecological health. To preserve the region's hydrological system, the Southwest Florida Water Management District, a state- chartered agency, has ordered Tampa Bay Water to start cutting in half the water it draws from 11 of the utility's dozen wellfields.
HONING THE TECHNIQUE
Desalinization technology--running salty water through membranes, removing salt through electrodialysis, filtration and reverse osmosis- -has been proven to work in North Africa and the Middle East. Some 130 nations currently produce 6 billion gallons a day of high-quality water by removing salt.
In the United States, communities and businesses now run more than 1,200 desalting plants that tap groundwater made brackish by salt. All totaled, these efforts are capable of processing 300 million gallons per day. Most of the efforts are in modest-sized communities. On North Carolina's Outer Banks, for instance, Dare County runs three reverse- osmosis facilities that produce public drinking water from salty wellfields, and 24 Texas towns rely on desalinated groundwater for municipal water supplies.
Until recently, however, converting seawater hasn't been a practical solution for populous metropolitan areas. The Florida Keys Aqueduct Authority mothballed a seawater desalinization plant in 1988, and Santa Barbara soured on a seawater plant it built in the late 1980s after two partners dropped out and desalinated seawater ended up costing more than $4.50 for a thousand gallons.
In the past decade, however, companies that manufacture reverse- osmosis systems have made impressive strides toward perfecting the technology. Membranes are now stronger and more durable, reducing maintenance costs. They also remove impurities more efficiently, using less electric power to push pressurized water through filters. Plants are being built closer to existing electric power generating stations, which shaves construction costs: Water processing plants can use existing power plant cooling water intakes to draw seawater in. What's more, salty residues that the desalinization process produces can be mixed with the powerplant discharge to dilute concentrations that might harm marine life.
Technical improvements arrived just in time to help the three-county Tampa Bay region deal with its vexing long-term supply problem. Pressure from the Southwest Florida water district to cut groundwater pumping that was draining wetlands and lakes forced Hillsborough, Pinellas and Pasco Counties, along with Tampa, St. Petersburg and New Port Richey, to negotiate an end to local rivalries over the region's dwindling water reserves. "We had to find new water resources, and we had very limited options to choose from," says Pinellas County's Stewart.
The jurisdictions formed Tampa Bay Water in 1998 to develop, treat and pipe water for all their local drinking water systems. In addition to traditional means of assuring supply--constructing a new canal, treatment plant and reservoir--Tampa Bay Water signed a contract with a subsidiary of Connecticut-based Poseidon Resources Corp. to build a 30,000-square-foot desalinization plant that could provide 25 million gallons of drinkable water a day.
The Southwest Florida water district is reimbursing Tampa Bay Water for 90 percent of the plant's capital cost, effectively cutting the utility's cost for desalinated water to $1.58 per thousand gallons. The project is nearing completion next to Tampa Bay Electric's Big Bend generation station. Beginning early next year, it will take in 44 million gallons from the 1.4 billion gallons that the power plant withdraws from the bay every day, and return 19 million gallons of doubly concentrated salty water, mixed with powerplant discharges in a 70-to-1 ratio, to the bay.
Some residents objected that the residue would harm the bay's marine life, but courts last year dismissed a legal challenge to a state permit for the discharges. Ken Heard, water resource director for the utility, says the agency will commit $1 million a year to monitor discharge impacts in the bay.
Even as Tampa Bay Water gets ready to open its new plant (and construct a second one), other facilities are about to be built in various parts of the country. The Texas Water Development Board this fall was working with regional water officials on plans for a demonstration desalinization plant along the state's Gulf of Mexico coastline. The water will probably be more costly than Tampa Bay's. Gulf water, says Hari Krishna, a board engineer who's analyzing desalination prospects, carries a higher salt concentration than Tampa's bay water. Even so, he expects it to sell for between $2 and $3 per thousand gallons, putting it in the same range as city water now available in Texas.
In Southern California, as the Colorado River cutbacks take hold, the cooperative Metropolitan Water District, which currently imports water from the Colorado dams and from Northern California for 26 cities and water agencies, is offering a $250 per acre-foot subsidy to encourage cities and counties to replace that water with local resources. The MWD staff has been reviewing proposals for seawater plants drafted by five local agencies--San Diego County, the Los Angeles Department of Water and Power, and the water districts serving Orange County, Long Beach and Carson. In combination, the proposed plants could produce 120 million gallons a day. "Any of these facilities would have a regional benefit by adding to overall supply reliability," says MWD board Chairman Phillip J. Pace.
This fall, the MWD board was considering tripling its target for desalinated seawater from 50,000 to 150,000 acre-feet a year. The San Diego County authority is working on plans for a major facility at an existing power station in Carlsbad that would be capable of producing 50 million gallons a day. Ken Weinberg, water resources director for the San Diego County authority, figures the cost will be roughly $800 per acre-foot or $2.45 per thousand gallons, plus another $100 per acre-foot for a pipeline to pump the water to elevations as much as a thousand feet above sea level to the county's distribution system. MWD's $250 subsidy for each acre-foot cuts that cost to $650. That's still well above the $431 per-acre-foot charge for imported Colorado River water. Seawater desalinization, Anatole Falagan, MWD's assistant water resource management director, points out, "is at the edge of being cost competitive with other new sources" that Southern California will have available.
INLAND WATER WAYS
Inland communities are adopting similar desalinization techniques to turn brackish groundwater into drinking water. Since the briny groundwater is generally less salty than ocean or bay waters, processing that water is cheaper.
Brackish groundwater already provides significant supplies to a number of water-short communities. In Texas, more than a hundred desalinization plants now produce 40 million gallons of usable water per day for electric generators, semiconductor manufacturing, and soft drink and instant coffee processing. Small Texas towns rely on desalted groundwater for 23 million gallons daily for municipal water, and larger cities are also tapping into brackish groundwater to supplement drinking water supplies. El Paso is working with Fort Bliss, the U.S. Army base, on a 29 million gallons per day groundwater desalinization project that will supply one-fourth of the city's water, and Wichita Falls is building a 15 million gallons a day plant. In Virginia, the utility serving Jamestown and James County is building a 5 million gallon per day groundwater desalinization plant.
At present, desalinization looks attractive for inland communities where pumping has depleted fresh groundwater, leaving remnants that carry high salt concentrations. In some coastal areas, moreover, the rapid extraction of fresh groundwater has been sucking seawater into below-ground aquifers. As that trend continues, "my guess is that areas that are 50 to 100 miles from the shoreline will be the next wave of utilities looking into using brackish water," says Ben Movahed, president of the American Membrane Technology Association.
Some salty groundwater carries too many other pollutants to be suitable for drinking water. Florida's brackish water, for instance, is often threaded with natural organic contaminants. Even so, Tampa Bay Water plans to withdraw brackish water from 15 or so wells north of St. Petersburg and convert 5 million gallons a day to drinking water. At present, the Southern California MWD funds 13 groundwater desalting plants that produce 25,000 acre-feet of drinking water a year. Local water agencies convert another 18,000 acre-feet a year from saline groundwater, and nine more facilities are scheduled to come on line in the region.
THE WASTEWATER REMEDY
Communities threatened by scarcity are exploiting another substantial resource they've previously neglected--the effluent discharged every day from sewage treatment plants.
Recycling wastewater doesn't create new water supplies, since it comes from fresh water that has already been used--flushed down toilets, drained out of sinks and bathtubs or discharged by industrial equipment. Normally, sewage treatment plant effluent is released into rivers, lakes or bays. In the past decade, however, a number of major metropolitan areas have begun treating it to reuse to irrigate golf courses, parks and roadside vegetation. The benefits are two-fold: environmental impacts caused by discharging effluent in natural waters are reduced, and recycling wastewater conserves municipal drinking water that otherwise would be used outdoors.
Reclaimed wastewater is a dependable supply, since sewage is treated every day. It is not, however, free or even cheap. Federal and state standards require advanced treatment of effluent intended for recycling. There are complications as well. Home water softeners, for instance, increase salt concentrations that can make wastewater unfit for irrigating crops.
On the cost side, sewage treatment plants generally have been built on low-lying lands along rivers and bays, and pumping effluent uphill for reuse can be expensive. Since recycled water is used only for limited purposes--mostly industrial cooling and irrigation, not for gardening, swimming pools or household water--it must be handled separately and delivered to customers through dedicated pipes. In St. Petersburg, for instance, the city supplies wastewater to golf courses, parks and commercial complexes, and has built 290 miles of pipes to extend the system into residential areas. But a homeowner has to pick up the $300 to $500 charge for connecting a yard sprinkling system to reclaimed water lines. "It's difficult for folks to have to pay through the nose just for recycled water," says Hillsborough County Commissioner Ronda Storms.
Tampa's city water agency is building a $28 million system to extend pipelines carrying treated effluent to residences and businesses. More than 4,000 customers have signed up, and officials figure they'll save 2 million gallons of potable water a day by using recycled water to water the grass during the dry season. In Hillsborough County's separate system, "we're using the maximum amount of reclaimed water that we have available, and we have a waiting list," says T. Barton Weiss, the county's water resources administrator. Weiss points out that persuading industrial customers to substitute recycled for fresh water makes the most sense, since their use stays the same year-round instead of peaking during the summer season.
In Texas, El Paso, San Antonio and Austin have expanded reclaimed water systems. Near Los Angeles, the Irvine Ranch Water District supplies treated wastewater for flushing toilets and air conditioning in some office complexes.
One of desalinization's attractions is that it provides drinking water. Technically, the same is true of reclaimed water. Highly treated wastewater is recycled into municipal drinking water in Singapore, but the U.S. public so far has wrinkled its nose at the concept of "toilet to tap" recycling.
People indirectly drink treated wastewater all the time, of course. Sometimes it's from rivers that are downstream from treatment-plant discharges. In some areas, local agencies pump treated wastewater into the ground to replenish falling water tables or form barriers to keep ocean water from invading potable aquifers. To eliminate discharges from several sewage plants, a regional wastewater agency in Northern Virginia operates an advanced wastewater reclamation plant that pipes 32 million gallons a day into the Occoquan Reservoir, the water supply for about a million residents.
Sometimes, public resistance forces a utility to cease and desist. San Diego's water authority, for instance, found public reaction such that it had to back away from a proposal to pipe purified wastewater into a San Diego city reservoir.
For the most part, as long as the tap turns on, most American consumers still prefer not to think too much about where the water they drink is coming from. Public water managers, however, have no choice but to find additional supplies. "You need to do everything and as much of everything as you can," Weinberg says. "The more diverse you are, the better position you're in to make sure you're reliable."
We invite you to discuss and comment on this article using social media.