Citizens of El Paso, Texas, who live in the northern tier of the Chihuahuan Desert, one of four deserts that make up the Great American Desert, are moving rapidly to expand the building of desalination plants to provide drinking water for survival, as well as water for crop irrigation, industry, and home use. This is not only being done in El Paso, but throughout Texas, breaking free from the debilitating “free market” and fiscal conservatism ideology that holds the state captive, reports the Texas Tribune on April 13.
El Paso is a city of 679,000, in an area so arid that it is susceptible to dust storms that plant a layer of dust on windshields, clothing, skin, and in nostrils. Ground and surface water supplies are dwindling. In 2007, a partnership between the El Paso Water authority, and the nearby Fort Bliss military base brought to completion what is today called the Kay Bailey Hutchison Desalination Plant. It produced 27.5 million gallons of pure water per day, making it, at that time, the world’s largest inland desalination facility. The city now seeks to expand the plant’s capacity to 33.5 million gallons per day, which, with a city consumption of 105 million gallons per day, would mean desalination supplying 32% of the city’s water provision.
El Paso’s desalination plant uses the reverse osmosis (RO) process on brackish water—water that has a lower salt concentration than seawater, but higher than freshwater. (There are two other processes of desalination, that employ heating the water, and distillation.) Such brackish water is usually found in transitional zones, where freshwater meets saltwater, such as estuaries and coastal lagoons. Under RO desalination, the salty water is transported to the plant, where it is first filtered through strainers to remove sand particles. Then, it is transported through cartridge filters, which remove very fine-grained sediment. Finally, it is pumped at very high pressure through RO membrane units, each with 72 vessels: clean potable water is forced through to one side of the membrane, leaving behind salt and bacteria. The latter is transported 22 miles to deep well injection sites, where it is injected into a fractured rock formation.
