Desalination R&D:
The New Federal Program

James E. Mielke
Specialist in Marine and Earth Sciences
Resources, Science, and Industry Division

February 18, 1999

RS20069

Background

The oceans account for approximately 97.4% of the world's water. Another 2% is locked up in ice caps and glaciers. Subtracting saline ground water and inland saline seas from the remainder, less than 0.5 % of the Earth's water is directly suitable for human consumption, agricultural or industrial uses. In recent years, desalination has increasingly been used throughout the world to produce potable water from brackish groundwater and seawater, to improve the quality of fresh water for drinking and industrial use, and to treat industrial wastewater prior to discharge or reuse. Technologies that were originally developed to desalinate water are now widely applied in this country to remove contaminates other than salt from freshwater supplies.

Currently, there are approximately 4,000 desalination plants in 120 countries worldwide with a combined capacity of over 3,500 million gallons per day (mgd). About 60% of this capacity is in the Middle East. There are nearly 800 desalting plants in the United States with a combined capacity of over 224 mgd. Many of these are for industrial use. However, coastal cities in Florida have had to rely on desalination of brackish water for several years since salt water intrusion of underground aquifers resulted from over-withdrawal. There are desalination plants in 46 states and desalinated water represents about 1.4% of the 16,000 mgd of water consumed in the country for domestic and industrial purposes.

The use of desalination technologies for treating fresh, brackish, and contaminated water supplies will continue to increase because of increasing shortage of use able surface and ground water in many parts of the United States, but large-scale seawater desalination will probably not be cost-effective, except as a last resort, for some time to come. However, this point may have been reached in southern California where several coastal communities have moved toward desalting seawater to supplement freshwater supplies.

Of the many available desalination technologies, two membrane processes - reverse osmosis and electrodialysis - are most widely used in the United States. Such widespread use would not have been possible without the advances due largely to federally sponsored research and development. Federal funding for most desalination research was discontinued in 1982. This research program, which began in 1953, was primarily responsible for the development of reverse osmosis, and for many advances and improvements in distillation technologies. During this 30-year period, the Federal government spent over $1 billion (in 1999 dollars) on desalination research, development, and demonstration projects. The United States still holds a technological advantage in some, but not all, areas of desalination. U.S. industry invests an estimated $5 million to $10 million annually in desalination research and development.

Legislative History

The federal government has had a long involvement in desalination research, development, and demonstration, at times involving considerable interplay between the executive and legislative branches. Federal funding of research and development for converting saline and brackish water into usable water began with the passage of the Saline Water Act of 1952 (66 Stat. 328). This was, in retrospect, surprisingly farsighted in providing research and development stimulus at a time when few land-based water supply problems were identified. Authorization was extended to include construction of demonstration plants (72 Stat. 1705). Subsequently, these authorities were merged and consolidated in 1967 by the Saline Water Conversion Act, which was in turn repealed and superseded by the Saline Water Conversion Act of 1971 (§5 Stat. 159). In 1974, the Office of Water Research and Technology (OWRT) was formed in the Department of the Interior through consolidation of the former Office of Saline Water (OSW) and the Office of Water Resources Research (OWRR). The OSW had been created in the mid-1950s to carry out the program of saline water research and OWRR had been created to carry out the functions of the Water Resources Research Act of 1964, which provided for a series of programs to stimulate water resources management and utilization, including the establishment of water resources research institutes at land-grant colleges and State universities.

The western drought of 1976-77 stimulated renewed interest in the application of science and technology to water resources problems. Consequently, in the 95th Congress, additional legislation affecting the desalination program was enacted. First, the Water Research and Conservation Act of 1977 (P.L. 95-84) was passed, authorizing a $40 million appropriation for the construction of four desalting demonstration plants as cooperative efforts with local entities. Second, Title II of P.L. 95-467 (the Water Research and Development Act of 1978) expanded and redirected the Saline Water Program and authorized funding for FY 1979 and FY 1980. In addition, P.L. 95-467 raised the number of demonstration plants to five and authorized additional funds for that purpose.

The 96th Congress passed P.L. 96-457, which amended both the Water Research and Development Act of 1978 and P.L. 95-84. P.L. 96-457 removed the limitation on the number of cooperative demonstration plants that could be constructed and increased the Federal portion of the cost-sharing arrangement. Three cities (Alamagordo, New Mexico, Virginia Beach, Virginia, and Grand Isle, Louisiana) had been selected as sites for demonstration plants when the Reagan Administration terminated the program.

The Office of Water Research and Technology was abolished at the end of FY 1982 and the desalination program was transferred to the Bureau of Reclamation. At that time, funds were not allocated for the continued operation of the two remaining federal saline water conversion research and test facilities at Wrightsville Beach, North Carolina and Roswell, New Mexico (others operated in the 1960s and 1970s had been located at Freeport, Texas; San Diego, California; and Webster, South Dakota). Funding for these facilities, along with matching funds for the 54 water research institutes established at land-grant colleges and research grant funding, was being provided under the Water Research and Development Act of 1978. These authorities, along with maintaining a clearinghouse of data and technical literature on water research, were funded at about $33 million annually through FY 1982.

The Administration's budget request for FY 1983 and FY 1984 contained no funds for the water research program authorized by the 1978 Water Research and Development Act. Congress, however, provided funding through appropriation acts to maintain a reduced water research program and help support the State water research institutes. The Office of Water Policy within the Department of the Interior was designated to administer these funds. Following the Department of the Interior's termination of the Office of Water Policy, the residual of the desalting research program was placed within the U.S. Geological Survey.

Desalination research as an integral part of basic water research rather than a separate program was newly authorized by the Water Resources Research Act of 1984 (P.L. 98-242), following override of the Presidential veto. This Act repealed the 1978 Act and authorized appropriations for FY 1985-1989. P.L. 98-242 also provided for the disposition of the two remaining federal desalination research and test facilities. These were turned over to the local communities. The Roswell facility had been used primarily for testing membrane systems for use in desalting brackish water and the Wrightsville Beach facility had been used primarily for testing seawater desalting systems. Subsequent reauthorizations continued federal desalination R&D through FY 1997 under the Water Treatment Technology Program conducted by the Bureau of Reclamation.

Desalination Technologies

There are essentially five basic techniques to desalt water: distillation, reverse osmosis, electrodialysis, ion exchange, and freezing processes. Distillation and freezing remove fresh water from saline leaving behind a more concentrated brine. Reverse osmosis and electrodialysis are processes in which membranes are used to separate salts from fresh water. Ion exchange involves passing saline water over resins which exchange more desirable ions for less desirable dissolved ions.

Distillation involves boiling the saline water at atmospheric or reduced pressure and condensing the vapor as fresh water, leaving behind a more concentrated brine solution. Even though distillation chambers are run in series to conserve energy (i.e. the incoming water to one unit is preheated by using it to cool the vapor in another unit), the energy consumption of distillation methods is still relatively high compared to other methods. Because distillation involves vaporizing water from the salty feed water, the energy required for distillation (and, consequently, costs) does not increase appreciably with increasing salinity. Thus, distillation plants have commonly been used for desalting seawater although membrane systems are competing in this area. Solar distillation has also been developed, but even though the energy source is free, the conversion rate (and amount of water produced) is fairly low.

Reverse osmosis is a membrane process that relies on the tendency for fresh water to diffuse through a semipermeable membrane into a salt solution, thereby diluting the more saline water. The fresh water migrates through the membrane as though there were pressure on it, and the effective driving force is called osmotic pressure. By applying pressure to saline water on one side of a semipermeable membrane, fresh water can be driven through in the direction opposite to the osmotic flow. This process is called reverse osmosis. Although energy intensive, one of the major advantages of reverse osmosis is lower energy consumption than distillation, particularly for brackish water, although reverse osmosis is used to desalt seawater.

Electrodialysis depends on the ability of electrically charged ions in saline water to migrate to positive or negative poles in an electrolytic cell. Two different types of ion-selective membranes are used - one which allows passage of positive ions and one which allows negative ions to pass between the electrodes of the cell. When an electric current is applied to drive the ions, fresh water is left between the membranes. The amount of electricity required for electrodialysis, and therefore its cost, increases with increasing salinity of feed water. Thus, electrodialysis is less economically competitive for desalting seawater.

Ion exchange resins substitute hydrogen and hydroxide ions for salt ions. For example, cation exchange resins are commonly used in home water softeners to remove calcium and magnesium from "hard" water. A number of municipalities use ion exchange for water softening, and industries requiring extremely pure water commonly use ion exchange resins as a final treatment following reverse osmosis or electrodialysis. The primary cost associated with ion exchange is in regenerating or replacing the resins. The higher the concentration of dissolved salts in the water, the more often the resins will need to be renewed. In general, ion exchange is rarely used for salt removal on a large scale.

Freezing processes involve three basic steps: partial freezing of the feed water in which ice crystals of fresh water form an ice-brine slurry, separating the ice crystals from the brine, and melting the ice. Freezing has some inherent advantages over distillation in that less energy is required and there is a minimum of corrosion and scale formation problems because of the low temperatures involved. Freezing processes have the potential to concentrate waste streams to higher concentration than other processes, and the energy requirements are comparable to reverse osmosis. While the feasibility of freeze desalination has been demonstrated, further research and development remains before the technology will be widely available.

Desalination Costs

The cost of a desalting plant is determined by a number of technical and economic factors. The major cost categories are capital costs and operating and maintenance costs. Capital costs are determined by the process type; plant capacity; feed water type and salinity; pretreatment required; product salinity desired; and site-related costs for land, plant, and brine disposal. Operating and maintenance costs include labor, energy, supplies, and general administrative expenses. The economic characteristics of a desalting plant are usually expressed in two ways: the capital cost per unit of installed capacity, such as dollars per gallon-day; and the total annual product water costs, such as dollars per thousand gallons of annual production. The product water costs are determined by the ratio of the total annual costs to the annual water production. Since annual costs (including fixed costs) are incurred at some minimum level even when no water is produced, the product water cost is sensitive to the level of output and can increase significantly if the output drops. High water costs often result from excessive "down time" for maintenance, occasionally from shortages in suitable feed water, and from fluctuation in product demand; all of which decreases annual output.

Dual purpose plants can affect the economics of desalination. For example, in a dual purpose electric power/desalination plant, waste heat from electric power production can be used for distilling seawater in the desalting plant, or steam pressure from power production for desalination by reverse osmosis.

Water costs of existing desalination plants vary widely, and frequently are not completely comparable because of differences in the cost-determining factors mentioned above. There are also economies of scale favoring larger plants, which are particularly significant for plants with capacities smaller than 3 million gallons per day. In general, the cost of desalting seawater is about 3 to 5 times the comparable cost of desalting brackish water. Brackish water can be desalted most economically on a large scale by reverse osmosis or electrodialysis at costs of about $1.50 to $2.50 per 1,000 gallons. Seawater desalination on a large scale by reverse osmosis or distillation costs about $4 to $6 per 1,000 gallons (under optimum operating conditions) and can increase to as much as $10 per 1,000 gallons if equipment isn't operated efficiently. For comparison, publicly supplied water in metropolitan areas of the United States typically costs around $ 1.25 to $1 .50 per 1,000 gallons for treatment and delivery (not counting sewage-related costs).

The New Program

The Water Desalination Research and Development Program was authorized by Congress under the Water Desalination Act of 1996 (P.L. 104-298). The Act authorized program funding of $5 million per year for research and studies for six years, beginning with FY 1997. In addition, $25 million was authorized over six years for demonstration and development. For FY 1998, $3.7 million was appropriated for the desalination R&D program. The conference allowance for the Energy and Water Appropriations Bill for FY 999 included $2.5 million for the Desalination Research and Development Program in the Bureau of Reclamation.

The primary goal of the Desalination R&D Program is to develop more cost-effective and technologically efficient means to desalinate water. The two primary thrusts are: 1) perform research on desalination technologies and related issues to push the state-of-the-art forward (research and studies); and 2) conduct development and demonstration activities to test technological advancements, to confirm economics, and to gain public acceptance (development projects). Initially, research will be conducted through grants and contracts with non-federal entities and through federal laboratories. The federal share of the cost of a research, study, or demonstration project shall not exceed 50% of the total cost of the project or study and not exceed 25% unless the Secretary of the Interior determines that the project is not feasible without the increased federal contribution. Within the first three years of the program, the Bureau of Reclamation is to submit to Congress a report recommending demonstration and development projects to evaluate research findings further.

Currently, the Bureau of Reclamation is also responsible for the operation of a large desalting plant at Yuma, AZ, , through a treaty agreement with Mexico to remove the excess salinity from the Colorado River water before it discharges into Mexico. This excess salinity is acquired after Colorado River water passes through irrigation systems in the American West. A test facility at the Yuma plant is available and employed for further developing desalination technology.