It would probably be a lot cheaper and cost effective to buy Israeli desalinization technology.
How much does it cost to build a desalination plant?
It depends on several factors including source water, location, treatment process, and the size of the plant. Building a brackish water desalination plant usually costs less than that of a seawater desalination plant because brackish water is generally cleaner and contains less total dissolved salts (see Question 2, above). In 2007, $87 million was spent to build the Kay Bailey Hutchison brackish groundwater desalination plant in Texas. Design capacity of the KBH plant is 27.5 million gallons per day (MGD). The 2010 biennial report on seawater desalination projected that it will cost approximately $32 million to build a 2.5 MGD seawater desalination plant, and approximately $658 million to build a 100 MGD seawater desalination plant in Texas.
Additional information on the cost of desalination plants in Texas is available at Cost of Desalination in Texas
http://www.twdb.texas.gov/innovativewater/desal/faq.asp#title-07