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Could Drinking Seawater Be Good For Us?

How Desalination Could Solve California's Drought and America's Water Needs

Could Drinking Seawater Be Good For Us?

It might sound crazy, in the middle of a drought, to suggest that California can have a water-independent future. But I’ve come to believe that this is possible.

My studies and those by others, as well as the experiences of nations such as Singapore, Australia, Israel, and many European countries, show that water reclamation, water recycling, and reuse—which currently accounts for under 10 percent of the water Americans use in most regions—could reduce up to 30-50 percent of the country’s water use. This is important for a number of reasons.

Water and energy are inextricably linked, and there is an urgent need to reduce the energy cost of water delivery nationwide, which accounts for a significant portion of energy usage in many communities. In California, for example, 19 percent of the electrical energy and 30 percent of the natural gas we consume is water-related. America’s water infrastructure is also aging, and requires costly upkeep and retrofitting. Meanwhile, agricultural sustainability in the Western U.S.—and throughout the country—is threatened by population growth, increased demand for crop production (for both food and biofuels), shrinking freshwater resources, increased soil, groundwater, and surface water salinity, increased security concerns, and diminishing fossil fuel resources.

But there is one water resource we’re underutilizing: seawater. Reverse osmosis (RO), the leading technology for seawater desalination (as well as for brackish and river water), is both simple and scalable.

RO membrane technology separates and removes dissolved salts and impurities from water through the use of a semi-permeable membrane. In the RO process, high-salinity water is forced by pressure through a membrane that rejects salt ions; high-purity water is filtrated out. This process has been around for a half century: The first viable membranes for water desalting were developed in the early 1960s at the School of Engineering at UCLA, which then commissioned the world’s first reverse osmosis plant for brackish water desalination in the Fresno County city of Coalinga. It is estimated that, in 2011, the capacity of desalination plants around the world (either in production or under construction) amounted to about 80 million cubic meters/day with over 17,000 desalination plants in 150 countries. The global desalination market is estimated at approximately $18 billion, but that figure could rise to as high as $30 billion within a few years.

Critics contend that reverse osmosis desalination requires large amounts of energy. But so do our home refrigerators, air conditioners, and washing machines. The real issue is the cost of water desalination relative to other available sources. For example, bottled water costs range from $1 to $3 per liter in the U.S., depending on the brand and location of purchase. In comparison, seawater desalination costs can be as high as about $0.45 per 100 liters and about $1.50-$2.00 per 1,000 liters for large-scale production. Of course, the above cost does not include conveyance of the water to the customer.

Over the years, intensive research and development efforts have been devoted to lowering the energy cost of reverse osmosis seawater desalination with tremendous success. Since about 1990, energy costs have decreased by nearly 75 percent for large-capacity plants. In principle it is possible to lower the energy costs of reverse osmosis desalination even further, although this could very well be at the expense of higher capital cost.

There are a number of impediments to lowering costs further. As water permeates through the reverse osmosis membranes, various solutes such as organics (e.g., pesticides and humic materials, which affect acidity and alkalinity), inorganics (e.g., calcium carbonate, calcium sulfate—essentially dry wall material—as well as silica), particulate matter, and bacteria concentrate near the membrane surface. As these materials concentrate, more energy is needed to pump the water through the membrane; cleaning and replacing membranes also adds to the cost of the process. Advances in membrane materials, process optimization, and control could further reduce the cost of water desalination. Engineers are also experimenting with lowering the costs through developing membranes that will lower desalination plants’ footprints, creative financing for larger plants, as well as possibly deploying smaller, remotely monitored and operated plants closer to the point of need. Smaller plants could potentially benefit from the use of renewable energy resources like solar and wind power.

We are in a world of new water challenges and new water opportunities. New and non-traditional water resources (seawater, groundwater) and wastewater reclamation opportunities exist, but are mostly underutilized.

Over the next few years, it seems likely that the cost of desalination water production will be reduced by 20 to 40 percent. Around the world, many large desalination plants have been in operation for decades, and thousands of smaller plants are being built.

Seawater is a large water resource that is not subject to droughts. In that sense, it provides a large reservoir that—in proportion to surface water—is “limitless.” Seawater desalination could provide the necessary buffer the state needs to make up for water shortages now and in the future.



Yoram Cohen is professor of chemical and biomolecular engineering at UCLA and director of the UCLA Water Technology Research Center.
Primary Editor: Sarah Rothbard. Secondary Editor: Joe Mathews.
*Photo courtesy of Christina Kekka.
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  • Concerned Citizen

    Are you kidding me?

    What kind of comparison is bottled water use to desal? Of course bottled water uses more energy. How about comparing the cost to the water we get from the tap (which is perfectly fine by the way). My guess is that the cost per glass is pennies on the dollar compared to desal.

    Where is conservation in this conversation? We currently use 70% of our water on outdoor uses, mostly for thirsty lawns. That adds up to about 55 gallons a day, well above most other countries. We can do much, much better.

    Sure, we could build desalination plants all up and down the coast with large energy plants to support them. We could do a great job destroying our beach-loving tourist industry at the same time…

    Or, we can make simple changes to our landscape and cut our water use to reflect the dry climate we live in.

  • Nick Lyons

    Combining desal with solar and/or wind energy makes a lot of sense. Create clean water when the sun shines or the wind blows. The intermittent nature of wind and solar, which requires some kind of storage or backup to meet electricity demand, becomes a non-issue, since water storage is typically part of existing water delivery systems.

    Ultimately, for large-scale desal, 4th gen nuclear, with its very high temperature operation, becomes a perfect match for flash distillation desal, using the power plant’s waste heat to good purpose.

  • Kioren Moss

    It would have been far more
    useful if Mr. Cohen had calculated the cost of seawater desalination in the
    unit of acre feet instead of liters.
    Such plants are measured in acre feet, and so should cost calculations
    be. We had to build a spreadsheet to
    determine that his “$2 per liter” means approximately $2,500 per acre
    foot. We knew that but were checking whether
    he did. Current costs of using well
    water are in the range of $200 per acre foot, and residential users typically pay
    $1,200 per acre foot. Metropolitan Water
    costs about $1,200 per acre foot to wholesalers.

    Finally, we conclude that the
    cost to desalinate seawater is far more than the more obvious choice of
    recycling treated sewage discharge water.
    It is easy to see why: Seawater is some 35,000 total dissolved solids
    per million (TDS/M) and treated sewage plant discharge is about 400 TDS/M. The present level of discharge treatment is
    sufficient for irrigation of most crops; it is already cleaner than most well
    water. Yet it cannot legally be pumped
    back into the water table unless the TDS/M are reduced further. The cost to use reverse osmosis is much
    smaller for the 400 TDS water than for seawater. Mr. Cohen should focus on recycling treated
    sewage water. It is far more easily
    achieved.

  • Ivan A Gargurevich

    I am a graduate of the UCLA Chemical Engineering Department where I earned a doctoral degree. I have met Dr. Cohen then. I am disappointed that Dr. Cohen does not compare the cost of desalination with the cost of potable water today. My recollection is that desalination water is about 15-20 times more expensive or so. To mention bottle water is even a worst idea , studies by the Environmental Working Group ( or http://www.ewg.org/research/ewg-bottled-water-scorecard-2011) show that the quality of bottled water is not monitored and most are not any cleaner than water form your kitchen sink…My understanding also is that desalination can only achieve a 50% recovery, so what to do with the brine? In this respect, although more energy intensive, evaporation would achieve much greater water recovery form sea water, would this be in the long run a better alternative although costly (energy) ? He also does not mention what it would take (in terms of time) to build enough desalination plants in California to make some significant impact, my guess is that the time would be considerable. If the drought in California is a long term cycle, unless more feasible alternatives are found we are in for a true disaster. The economic fate of California may be truly jeopardize….My understanding is that archaeologists think that the end of Mayan civilization in the Americas was due to a prolonged drought in that part of the World, are we going to meet the same fate in California ?