America’s Authority in Membrane Treatment Membrane Desalination Power Usage Put in Perspective Scientists have known that the Earth’s distribution of cost for a seawater RO fresh water sources are available and natural hydrologic cycle continuously plant is shown below. considerable cost effective water desalinates water, using solar energy as conservation, efficiency improvements The energy cost portion of the total cost the water evaporates from the oceans and recycle and reuse are still possible. depends on the power/fuel pricing, type and lakes, leaving behind the salt and and degree of pretreatment, ocean But, let’s put seawater RO desalination mineral content. The resulting salinity, concentrate disposal, power requirements in perspective! freshwater vapors form clouds which regulatory requirements, land cost and produce rain and snow. This natural conveyance of seawater to and product Based on nationwide data from the cycle is the main reason why the oceans water from the desalination plant. Energy Information Administration, a are salty. This hydrological cycle typical refrigerator average annual continuously moves salt from land to The theoretical absolute minimum energy usage is 1,400-1,500 kwh. the oceans. amount of energy required by natural Using the average US water use per osmosis to desalinate average seawater Since the 4th century humans have house- hold of 100,000 gallons per is approximately 1 kilowatt-hour per tried to copy this natural cycle and have year, the energy requirement for cubic meter (kwh/m3) of water learned that “desalting” or supplying desalinated water to a produced, or 3.8 kilowatt-hours per “desalination” machines can be built house in the US will be less than an thousand gallons (kwh/kgal). The with an energy input to produce fresh old refrigerator, but the same as a actual SWRO energy requirement in water from brackish and seawater newer, more efficient refrigerator the 1970’s was 7.0 to 9.0 kwh/m3 sources. power use. (26-34 kwh/kgal). With recent Although there are many different types technological advancements and of desalination techniques, today the innovations in high efficiency pumps, least energy intensive method is a energy recovery systems and overall semi- permeable membrane process, higher efficiency plants, the actual referred to as Reverse Osmosis (RO). expected consumed energy has reduced Typical brackish water RO desalination to 2.5 to 3.5 kwh/ m3 (10-13 kwh/kgal). uses a fraction of the energy required As an example, the Perth desalination for seawater desalination (10%-30%). plant in Australia, which utilizes wind Therefore, this fact sheet will focus on power and advanced energy recovery seawater desalination utilizing RO The fuel required to fly a jumbo jet at systems uses an average of 3.5 kwh/ m3 technology. cruising altitude will be adequate to (13 kwh/kgal) of produced water. This provide seawater RO desalinated Energy is the largest variable cost for includes the total energy required from water to over 300,000 homes in the Seawater RO (SWRO) plants, varying ocean intake to customer. United States. from a third to more than a half the cost No one will argue that seawater RO of produce water. A typical desalination still consumes much higher energy than conventional fresh water treatment plants or water conservation. However, desalination facilities should not be considered as the primary option in locations where reliable Based on the data from the Office of Find ways of improving the Energy Markets and End Use, the desalination technology to average annual household energy further reduce the power requirements. power consumption is 11.0 MW. If the entire community is served by Find and expand other seawater desalinated water, the carbon- neutral energy annual power required for the sources such as wind, solar, nuclear and other innovative desalination plant to serve a house is methods. 1.0 MW, or an increase of less than 10%. In most cases, however, the Ease the process of existing traditional supply sources are co-locating desalination and power plants to take augmented with seawater and/ or advantage of the discarded brackish water desalinated waters, thermal energy, reduce the which further reduces the percent burden on the power grid and increase to typically less than 5%. make use of the lower off-peak power costs. Water agencies can also incorporate the value of the reliability and water quality advantages of membrane desalination when comparing traditional supplies (if available) to desalination. With recent concerns over the discovery of pharmaceuticals and personal care The California Desalination Task products in drinking water supplies, it Force estimates that if all the is only fair that such comparisons currently proposed seawater include values and advantages of desalination plants in California were membrane technologies. Additionally, This material has been prepared as an built, it would add 200 megawatts the value of seawater desalination, a educational tool by the American Membrane (mw) to the state’s peak load of new supply, which is under local Technology Association (AMTA). It is 52,000 mw, or less than 0.4%. control and is essentially independent designed for dissemination to the public to of climate changes and land use, should further the understanding of the contribution be carefully considered when that membrane water treatment technologies Opponents of seawater desalination comparing desalination to other can make toward improving the quality of typically only focus on the energy alternatives. water supplies in the US and throughout the consumption and the climate impacts world. associated with the increased power In summary, when traditional supply generation. Instead of opposing a sources are not feasible or available, For more information, please contact: technology that is helping many areas seawater desalination can be achieved throughout the world with water in an environmentally friendly American Membrane Technology crises, it would be more beneficial to all manner, without aggravating climate Association (AMTA) of us as a community to: change concerns. 2409 SE Dixie Highway Stuart, Florida 34996 Phone: (772) 463-0820 Fax: (772) 463-0860 Email: [email protected] or visit our website at: www.amtaorg.com (FS-7) April 2016 .