New desalters in Irvine and Tustin have specific purposes. The former will treat water contaminated with high levels of organics and with the solvent trichloroethylene, the resulting product water going to irrigation.

The latter facility, due to begin operation this fall, is designed to remove nitrates.

In Riverside, Calif., local groundwater did not meet drinking standards due to high concentrations of nitrates from decades of farm runoff. Additionally, the polluted water was escaping into tributaries on the Santa Ana River, which contributed to Orange County's water supply problems.

To combat those problems and help bring the area's water resources back to a useful condition, the Santa Ana Watershed Project Authority (SAWPA) opened a desalination plant in 1990 in the Riverside Area. The $13 million Arlington desalter uses RO on brackish water to produce 6 mgd.

Another slightly larger plant is planned for a nearby basin.

In Los Angeles, the Metropolitan Water District (MWD) has constructed a 2,000 gpd pilot plant to demonstrate the viability of vertical-tube evaporation technology and collocation of a desalination facility with a rehabilitated power plant. The plant would provide sea water intakes, out-falls and low-cost steam. Testing began in September, according to MWD Engineer David Dean.

If the technology and collocation prove out, he says, the goal by 2010 is a 50 mgd to 100 mgd distillation plant using ocean water.

REDUCING DEPENDENCE

The San Diego County Water Authority (SDCWA) serves an area that depends on imported water for 90 percent of its needs. Those sources are becoming more unreliable because of legal issues, environmental concerns and drought. To reduce that dependence, the authority and the city are launching a project that would put reclaimed wastewater through an RO plant and transport it to a 90,000-acre-foot reservoir where it would be blended with imported water and runoff, go though conventional treatment and become available for potable reuse. Scheduled to begin operation by 2001, the project is the first in California providing potable reuse via surface reservoir. Adding the RO element, says SDCWA Water Resources Supervisor Ken Weinberg, provides a level of treatment that ensures protection of public health because it will remove bacteria and protozoa as well as salts.

The estimated cost of the plant, which will be owned and operated by the city and should provide 20 mgd of potable water and another 10 mgd for irrigation, is $68 million with another $40 million to $50 million for the pipeline to the reservoir. Still, the total is comparable to the cost of importing the water the area needs, Weinberg says.

FLORIDA'S EXPERIENCE

On the other side of the country, Florida, like California, claims a burgeoning population and, while far from arid, has few rivers and large areas of brackish water.

It boasts far more desalination plants than any other state; ranging from 40,000-gallon facilities at resorts and mobile home parks to a 9.5 mgd plant in Dunedin, a 14 mgd plant in Cape Coral and a 12 mgd facility in Fort Myers.

In fact, one of the country's first RO plants for ocean water was built in Key West in 1980. It operated for 18 months, went on standby status and is now mothballed, according to Arlen Higley of the Florida Keys Aqueduct Authority. Key West pumps its water from Dade County via a 36-inch-diameter, 130-mile-long pipe, and the RO plant is strictly for use as an emergency backup in case of damage to that pipeline, which is attached to the Keys' many bridges. (The plant did run for one week after Hurricane Andrew disrupted water supplies.)

Higley says the plant is too expensive to run on a daily basis, costing $4 per 1,000 gallons. Water can be pumped south, he says, for $1.50 per 1,000 gallons.

"In an emergency, we bite the bullet," Higley says. "You can live without electricity, but you can't live without water."

The plant, comprised of six "trains" or modules that can run individually or in combination, is designed to produce 3 mgd of treated water from saltwater wells. Brine, with its collected salts, is pumped back into the sea.

DISPOSAL OF BY-PRODUCTS

In fact, disposal of by-products is beginning to eclipse cost as the No. 1 desalination issue in Florida and elsewhere. Little Jupiter, Fla., played David to the U.S. Environmental Protection Agency's (EPA) Goliath in battling discharge regulations that were threatening its RO plant.

In the late '80s, Jupiter realized that its fresh water supply was all but used up. It began planning for the installation of a desalination plant, which went on line in 1990.

Then, the shrimp died.

EPA regulations require toxicity testing before desalination plant concentrates can be discharged into any receiving waters. The tests involve tiny shrimp that are subjected to concentrates resulting from the process. If more than 50 percent of the shrimp die, EPA gets nervous.

In Jupiter's case, the the tests indicated unacceptable toxicity levels. The town, however, did not believe that its discharge was the culprit. Still, the state pressured the facility to construct deep-injection wells for discharge of its concentrate (at a cost of up to $6 million).

"The town just said 'no'," says John Potts, a Florida environmental consultant and first vice-president of the ADA. "Of the 120 or so desalination plants in the state, Jupiter was the first one to be told that its discharge was toxic, so the town started conducting its own tests."

Jupiter discovered that a factor called major ion toxicity was responsible for the shrimp deaths. In essence, the major salts in the concentrate - sodium, calcium, chloride, potassium - were present in different ratios than they would be in seawater.

That, the town found, caused the toxic reaction.

Unfortunately, Potts says, the regulations were written before anyone knew about major ion toxicity and, therefore, do not recognize it as a factor. Still, in a show of good sportsmanship, the state Department of Environmental Protection agrees that the phenomenon exists and has not shut down the Jupiter plant.

That is good news for the Southwest Florida Management District, which is considering building a $50 million desalination facility in the Tampa area that is expected to improve supplies, reduce damage to wetlands (from overpumping the current wellfields), provide high-quality and cost-effective water and possible hasten permitting through collocation with an existing power plant. The facility would draw water from the gulf and use RO technology.

That plant, like others, has elicited a mixed reaction, Potts says. "I have been surprised to have been contacted by representatives of environmental groups supporting the plant," he says. "They view it as more desireable than importing water from other areas of the state and depleting those areas. They see it as the lesser of two evils."

Still, desalting concentrates are classified by the U.S. Environmental Protection Agency as an industrial waste, Potts says.

That means that disposal is subject to stringent regulations, and that, he says, inhibits application of the technology. Consequently, ADA has been pushing to change the EPA designation.

The designation of desalination discharges spawns most of the opposition to the plants. "Most of it is due to the fact that the discharge is classified as industrial waste," Potts says. He calls the designation "the most serious hindrance to the technology," arguing that unless the concentrate can be disposed of, the technology cannot be used.

"The regulations," he says, "are out of date and inappropriately being applied."