California Turns Seaward to Slake Thirst for Water : Drought: Despite their costliness, small desalination plants have opened and larger ones are planned.

Faced with growing populations and a devastating five-year drought, communities up and down the coast of California are gearing up for the desalting of seawater to augment their dwindling water supplies.

Desalination is a proven and effective technology that has been widely used in the Middle East and the Caribbean, but desalination of seawater has never been used in the continental United States because of its high cost compared to other sources of water.

That situation is rapidly changing, however. The first seawater desalination plant in the United States was opened by the U.S. Navy on San Nicolas Island last October and a second is scheduled to open on Santa Catalina Island in late April. Santa Barbara has contracted for a larger desalination plant that would supply a third of its water needs by 1992.

Marin County operated a pilot desalination plant for three months last year and residents are expected to vote this fall on whether to construct a permanent facility to treat bay water.

The Metropolitan Water District, which supplies water to much of Southern California, expects to have a 5-million-gallon-per-day pilot desalination plant on line within three to four years and to begin construction of a full-scale, 100-million-gallon-per-day plant in San Diego a year later.

Last week, officials of the MWD, the Los Angeles Department of Water and Power, Southern California Edison and the San Diego County Water Authority said they are exploring a plan to build a huge desalination plant in northern Mexico.

“If the drought continues, we’ll be seeing these plants all along the coast,” said environmental engineer Ted Kuepper of the Naval Civil Engineering Laboratory in Port Hueneme.

Desalination technology now produces 3.5 billion gallons of fresh water per day worldwide. That total is but a drop in the bucket compared to the world’s total fresh water use, but is enough to produce 100 gallons a day for each of 35 million people, more than the population of California.

Experts say that desalination could supply all the fresh water that Southern California needs, as long as consumers are willing to pay two to 10 times current prices.

No good worldwide estimates are available, but at least 900 desalting plants are operating in the Middle East, most of them relatively large. The United States has more than 1,000 plants that desalinate brackish ground water, the majority of them small. The bulk of those are used to provide highly purified water for industrial uses, but many also provide drinking water, especially in Florida where brackish ground water must be treated before use.

Most of the technology used for desalinating water was developed in the U.S. national laboratories in the 1950s and 1960s. Desalination has been refined to improve efficiency and lower costs, but the underlying techniques would be readily recognizable to an engineer from the Eisenhower era.

The research was funded primarily by the Atomic Energy Commission, which was looking for uses for what it expected to be cheap energy produced by nuclear power plants, and by the Department of Interior, which foresaw water shortages in the West.

“Somewhere along the way, the Department of Interior lost interest, partly because the California Water Project (which brings water to Southern California from the North) was under way and it was thought that it would relieve the water shortage,” said chemical engineer David Eissenberg of the Oak Ridge National Laboratory in Tennessee. Cheap atomic energy also proved to be an illusion. “The funds dried up and nothing much has happened since then,” Eissenberg said.

But the fact that the technology is old, experts say, also means that it has been tested and found effective. Its primary limitation is its cost--both the high capital investment for building complicated plants and the operating costs.

Existing desalination plants use one of two primary technologies: distillation or reverse osmosis. In distillation, water is heated until it turns into steam, leaving salt and other contaminants behind in remaining liquid water. When the steam is condensed, it becomes very pure water.

In reverse osmosis, the seawater is passed through a thin plastic membrane with pores so small they allow water molecules through but block salts, viruses, bacteria and other contaminants.

While about 65% of all desalinated water worldwide is produced by distillation, virtually all the U.S. plants are based on reverse osmosis, including those on San Nicolas and Santa Catalina and the plant to be built in Santa Barbara. The primary costs are for the production and maintenance of the sophisticated plastic membranes that do the filtering in osmosis and for powering the pumps that provide the high pressures necessary to force water through the filters.

The cost and effectiveness of reverse osmosis depends on the source of the water. For brackish ground water, which typically has about 10% the salt content of seawater, the pumps operate at the relatively low pressure of 100 to 200 pounds per square inch, and the cost can be on the order of $250 per acre-foot (325,000 gallons, or more than enough to provide water for two families for a year). By comparison, the cost of imported water in Southern California is about $230 per acre-foot.

The Orange County Water District operates a 15-million-gallons-per-day reverse osmosis plant in Fountain Valley that cleans waste water from sewage treatment plants. The water is injected into the ground to provide a barrier between underground reservoirs in the county and ocean water. That barrier prevents seawater from contaminating the reservoirs.

Much of the water injected into the ground flows inland and is pumped out again for use in the water system. Orange County plans six other desalination facilities that will bring the reclaimed water total to 75 million gallons per day, according to William R. Mills of the water district. All will treat waste water, not salt water.

For desalinating seawater, pumps must operate at pressures of 1,000 pounds per square inch or more and the cost can be four times as great as that of desalting brackish water, according to Randy Truby of Fluid Systems Corp., a membrane manufacturer in San Diego. Nonetheless, reverse osmosis plants often are desirable because they can be constructed in small modules that are rapidly assembled.

On San Nicolas, for example, the Navy installed a 12,000-gallon-per-day modular unit similar to those used by the Marines to purify water in the field, according to Lt. Cmdr. Gene Okamoto of Point Mugu. The unit was modified at Port Hueneme to provide around-the-clock operation. A second module of the same size will be installed later this year.

The San Nicolas units produce fresh water at a cost of $1,625 per acre-foot, Okamoto said. That is expensive, but it is substantially cheaper than the cost of barging water to the island, the only viable alternative. The two units will provide all the water needs for the 60 enlisted personnel and 165 civilians who track missiles from the Pacific Missile Test Center at Point Mugu.

Speed of construction was also a factor in choosing reverse osmosis for the installations at Santa Catalina and Santa Barbara. The 132,000-gallon-per-day unit on Catalina will service a new condominium development as well as provide about a quarter of the island’s total water. The unit will be built by Hamilton Cove Associates, which is building the condominiums, but it will be owned and run by Southern California Edison, which operates all utilities on the island.

Like the water on San Nicolas, Catalina’s is expected to cost about $1,625 per acre-foot. In this case, however, residents already are paying $2,600 per acre-foot for water from wells and catchment basins, so the new source will be cheaper.

Speed is especially important to Santa Barbara, where water resources have literally evaporated. After the permit process is completed within the next month or so, construction of the plant by Ionics Inc. of Watertown, Mass., is expected to take no more than 15 months. Water from the plant is predicted to cost about $1,900 per acre-foot and will increase the average Santa Barbara water bill, now about $20 per month, by 50%.

Other communities that have been exploring the possibility of using reverse osmosis to desalt seawater include San Luis Obispo, Monterey, San Diego, Morro Bay, Ventura and Oxnard.

For large quantities of water at a lower price, however, it almost certainly will be necessary to build distillation plants, probably in conjunction with an electric power plant. In this way, the heat remaining in steam after it has been used to generate electricity could be used to heat seawater for distillation, thereby lowering the cost of energy substantially. Engineers rate the efficiency of distillation plants according to the number of gallons of fresh water that can be produced from every 1,000 British thermal units (BTUs) of energy used.

The so-called multistage flash distillation plants in the Middle East use a variety of tricks developed in U.S. laboratories--including recapturing the heat given off when steam condenses and carrying out part of the evaporation at lowered pressures--to produce about eight or nine pounds of water per 1,000 BTUs.

The efficiency of such plants can be boosted to as much as 13 pounds of water per 1,000 BTUs, but the Saudis and other nations rich in natural gas have not seen the need to pursue high efficiencies.

“The Saudis are very conservative in design and operation,” said Oak Ridge’s Eissenberg. “They’re not interested in improving the design, but in replicating a proven design.”

Furthermore, despite the refinements that have been developed for systems like the Saudis’, that technology “is essentially obsolete, in my opinion,” said R. Philip Hammond, who oversaw development of the technology at Los Alamos and Oak Ridge and who now serves as a consultant to the Metropolitan Water District.

He believes that it will be supplanted by a distillation technique called multiple-effect distillation, or MED, which has been refined at Oak Ridge and by an Israeli company, Israel Desalination Engineering, Inc. About 3.5% of desalinated water in the world is produced by MED.

MED uses a much more efficient technology than flash distillation to recapture heat when steam is condensed, allowing as many as 15 pounds of water to be produced from each pound of steam. Furthermore, the heat transfer tubes are simpler in the flash system, reducing capital investment.

Perhaps most important, the process can work well with steam that has a temperature of only 160 degrees Fahrenheit, the temperature at which steam normally exits a generator at an electric power plant, according to Dan Mishkal, president of Ambient Technologies Inc. in North Miami Beach, the U.S. subsidiary of Israel Desalination Engineering. Hence, water production does not reduce electricity production at a power plant, as is the case with flash distillation, and less expensive materials can be used because less corrosion occurs at lower temperatures.

The Metropolitan Water District is proposing to build an 80-million to 100-million-gallon-per-day MED plant based on a refinement of Israel Desalination’s design. The new plant most likely would be added to San Diego Gas & Electric’s Encina or South Bay generating facilities when obsolete boilers in those installations are converted to gas turbines in the next few years. The Los Angeles Department of Water and Power and Southern California Edison will participate in the project.

Before that plant is built, however, the group will build a 5-million-gallon-per-day pilot plant to test the technology. That plant could be built within as little as three years. The water district’s board “has been very supportive and wants us to move ahead and get something on line,” said Gary Snider of the district.

The cost of water from the pilot plant is expected to be about $1,000 per acre-foot, but Hammond predicted that the water cost from the full-sized facility would be less than $500 per acre-foot.

The MWD-led group also is investigating the possibility of building the large plant on the Pacific Coast of Baja California south of Tijuana in conjunction with a power plant that would be built at the site. The advantage of the Baja site is that there might be fewer environmental problems, Snider said.

Despite the high costs, at least initially, some experts see desalination as the wave of the future.

William Andrews, president of Reliable Water Co. in Boston, cites the Cayman Islands in the Caribbean, where virtually all the water comes from seawater desalination. “They can afford it with no problem, which indicates that one could do it in California,” he said. “Their water bills are a lot less than my heating bills here in Boston.”

DESALINATION PROCESS If a large, new seawater desalination plant is built in Southern California, it will most likely use a technology different from that used in existing plants, such as those in the Middle East. But the distillation processes in both technologies involve the same concept: Using steam to heat cold seawater and produce fresh water condensation. Here is a general look at how the desalination process works: 1-- Cold seawater is pumped into a pipe within a pipe. 2-- Steam is pumped into the outer pipe. 3-- The steam’s contact with the cold-water pipe produces condensation. 4-- The condensation is freshwater, which is collected and sent to the city’s water supply. 5-- The seawater is converted into steam and continues to the next cycle where it heats more cold seawater and produces more freshwater. ADVANTAGES OF THE NEW TECHNOLOGY: The conventional process used by plants in the Middle East is called flash distillation. The technology that probably would be used in Southern California is called multiple-effect distillation. The main difference in the two systems is in the process used to capture and recycle the heat produced, which serves as the energy force in the process. In the multiple-effect distillation process, the heat transfer procedure is nearly twice as efficient as in conventional distillation, so much less energy is used to produce the same amount of water.