OCEAN WATER DESALINATION

Ocean Water Desalination involves removing the salt from water to make it drinkable. There are several ways to do it, and it is not a new idea at all. Sailors have been using solar evaporation to separate salt from sea water for at least several thousand years. Most of the world’s 1,500 or so desalination plants use distillation as the process, and there are also flash evaporation and electrodialysis methods. All these methods are very expensive, so historically desalination has only been used where other alternatives are also very expensive, such as desert cities. However, an exploding world demand for potable water has led to a lot of research and development in this field and a new, cheaper process has been developed that involves heating sea water and forcing it through membranes to remove the salt from the water. The process is even cheaper if the desalination plant can be located next to an electrical power plant that is already heating sea water to use for cooling the electrical generating units. Even so, it is still more expensive than other alternatives, but it is indeed becoming more competitive and could become a viable alternative to Edwards water. There is also a lot of interest in using local, brackish groundwaters as a source for desalination instead of ocean water. Such waters typically have only one-tenth the salinity of sea water, so desalination can be accomplished more easily and transportation is less of an issue.

In April 2000 the Texas Water Development Board approved a $59,000 grant to the Lavaca-Navadid River Authority to determine if building a $400 million plant on Matagorda Bay at Point Comfort would be economically and environmentally feasible. There is a power plant at this location that could supply the heated sea water for the membrane process. The study was released two months later and the cost rose to $755 million, but this included the cost of transmission facilities to San Antonio. The study estimated that a 50-50 mix of desalinated water and water treated by other conventional methods could be delivered to San Antonio users for about $2.80 per thousand gallons, compared to a current cost of $1.36 per thousand gallons. A similar plant being constructed in Tampa, Florida will raise customer’s water bills by about $7.50 a month. (1), (2)

A major advantage of desalination of ocean water is that water is always available even in the most severe droughts. The main environmental concerns of this project are increased salinity levels in Matagorda Bay and the fate of plankton and tiny sea creatures in the water removed for the process. Supporters say it won’t raise the salinity level appreciably and that organisms can be vacuumed out and replaced into the ocean. No one knows yet how this project would be funded