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.