Water Industry News

Midland Texas examines desalination options

Colin Guy
Staff Writer
Midland Reporter-Telegram
The development of a desalination plant in Midland could provide residents with a virtually inexhaustible supply of water and make the region more attractive to developers concerned about the availability of water resources, according to city officials.

Kay Snyder, director of utilities, and Stuart Purvis, assistant director of utilities, presented the City Council during its briefing session Tuesday with information about the status of desalination technology and how it could potentially benefit the city.

Purvis informed the City Council desalination, the removal of salt from brackish water, is not anything new, but recent advances in the field have made it a much more attractive option for use in West Texas.

"There are two major ways to do it," Purvis said. "Either heating (water) up and condensing it, or using a membrane."

Thermal desalination is very expensive, Purvis said, and does not completely purify the water. While the salt is removed, he said, other impurities will recondense. Because of the expense and inefficiency of thermal desalination the technology is not used in the U.S., Purvis said.

"(Membranes are) apparently where all the money and research is going," Purvis said. "There's been a lot of increases in the life of membranes and how well they work."

Purvis said there are two types of membrane processes, voltage driven and reverse osmosis, but it is the latter he believes has more potential. He said reverse osmosis can remove salts, as well as viruses and other contaminants, such as herbicides and pesticides. Purvis said the filtration method works by forcing water through the membranes with driving pressures ranging from 50 to 500 pounds per square inch. He said larger concentrations of salt require more pressure.

"Another real positive aspect of this, it's an incremental expenditure," Purvis said.

Purvis said if the city were to develop the city-owned T-Bar Well Field -- considered a potential source for the city's future water requirements by city officials -- it would require an investment of $115 million, including right-of-way acquisitions, before the first 1,000 gallons could be pumped. By contrast, he said, city officials can decide the level of financial commitment they wish to make to a reverse osmosis system. In order to increase the amount of water treated, he said, a new membrane can be added as needed. He estimated an initial plant that could treat 1 million gallons-per-day would cost approximately $2 million.

"I'd like to see a test," District 4 City Councilman Berry Simpson said.

At-large City Councilman Bill Dingus agreed, adding he would like to see a pilot project initiated that is "as small as we can make it."

Purvis said there are truck-mounted reverse osmosis treatment systems available that could be acquired in order to try out the system without making a large investment.

"I think this is important for the long term," Dingus said. "If you can demonstrate that Midland has an inexhaustible supply of water, that will really change the business (environment.)"

According to Snyder there are more than 2.5 billion acre feet of brackish water throughout the state of Texas that could be treated with a reverse osmosis system. Purvis added the availability of brackish water is not limited to the coastal regions and there are "significant reserves" available in West Texas the city could draw from.

City Manager Rick Menchaca suggested the City Council weigh the information provided by Snyder and Purvis so the subject can be discussed in depth during the next City Council retreat. He also indicated it may be possible to garner support from Odessa and Andrews to cooperate on a regional desalination plant.

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