Desalination removes salt and other dissolved minerals from water, making it suitable for human consumption or industrial use. This technology is becoming increasingly relevant in the United States as communities face growing pressure on traditional freshwater supplies. Prolonged drought conditions, population growth in arid regions, and the depletion of groundwater aquifers have contributed to a greater need for alternative water sources. Desalination offers a method to tap into vast reserves of saline water, enhancing water security and resilience across the nation.
Current Inventory and Production Scale
Determining the exact number of desalination plants in the US is complex because the total count depends heavily on how a “plant” is defined and the capacity threshold used. Surveys focused strictly on municipal facilities producing at least 25,000 gallons per day (GPD) identified 324 plants built between 1971 and 2010, with an additional 86 new facilities constructed between 2010 and 2017. This suggests approximately 410 public-facing plants that treat water for community use.
A much larger figure emerges when including industrial facilities, power plants, and smaller-scale operations. Estimates suggest nearly 2,000 desalination facilities larger than 300,000 GPD were operating across the country as of the mid-2000s. These plants treat water for their own operational needs or for specialized industrial processes, rather than public drinking water. The total combined production capacity of the municipal and industrial plants was estimated to be 1,600 million gallons per day (MGD) in 2005.
The municipal plants alone had a combined capacity of around 402 MGD in 2010. This production scale represents a very small fraction of the total freshwater consumed in the US. The nation’s largest seawater desalination plant, the Claude “Bud” Lewis Carlsbad facility in California, produces 50 million gallons of potable water per day, providing about ten percent of the water for the San Diego region. An average of 50 to 75 significant projects are initiated each year in the US.
Geographic Distribution and State Concentration
The majority of US desalination capacity is concentrated in a few specific states that need non-traditional water sources. The highest density of municipal desalination plants is found in Florida, California, and Texas. These three states account for a significant percentage of the brackish groundwater desalination facilities nationwide.
Florida is the leading state in the number of municipal desalination plants, largely due to its geography and geology. The state had 148 municipal facilities as of 2010, many of which tap into the brackish groundwater of the Floridan aquifer system. This concentration is driven by population growth and the threat of saltwater intrusion into coastal aquifers.
Texas and California also feature high concentrations of desalination infrastructure, driven by arid climates and persistent drought. Texas had 53 municipal desalination facilities as of a recent survey, with a total capacity of 157 MGD. California, despite having fewer total plants than Florida, is home to the largest seawater desalination facility in North America, reflecting its dense coastal population and reliance on imported water supplies.
Primary Water Sources and Technology Used
The US desalination landscape is centered on treating brackish water, not ocean water, which is a key distinction from many global desalination efforts. More than 80 percent of municipal desalination plants in the US treat inland groundwater that is salty but contains significantly less dissolved mineral content than seawater. Treating brackish water is less energy intensive and therefore less expensive than treating full-strength seawater.
The technology most commonly employed for both brackish and seawater desalination is Reverse Osmosis (RO). This membrane-based process uses high-pressure pumps to force water through semi-permeable membranes that block salt molecules and other impurities. The RO process is highly effective and is used in more than two-thirds of desalination facilities across the country.
Seawater desalination facilities, though fewer in number, are often larger and more visible, located primarily in coastal areas of California and Florida. The increased salinity of ocean water requires higher operating pressures in the RO system, which translates to greater energy use. A third, growing category involves water reuse and recycling, where municipal wastewater is treated using similar membrane technologies to achieve potable standards.
Limiting Factors to Expansion
Despite the increasing need for reliable water sources, the expansion of desalination in the US is limited by significant cost and environmental challenges. Desalination is an expensive process compared to traditional water sources, largely because of the high energy requirements. The electricity needed to power the high-pressure pumps in Reverse Osmosis systems often accounts for one-third to one-half of a plant’s total operating cost.
The most significant environmental challenge is the management of the concentrated brine, which is the super-salty waste product remaining after the freshwater is extracted. For coastal plants, this brine is typically released back into the ocean, but careful regulation is required to prevent localized ecological harm from the increased salinity. Inland brackish water plants face greater difficulty, as they must find suitable methods to dispose of the concentrate without contaminating soil or freshwater sources. Regulatory hurdles also slow the process, with new projects often requiring years to secure the necessary environmental and operational permits.