Arroyo is the director of Innovative Water Technologies with the Texas Water Development Board.
The native of Costa Rica said he has been working in the area of desalination for the past decade and he outlined the benefits of using a reverse osmosis system to remove the chlorides and suspended solids from ground and surface water.
Technological advancements in reserve osmosis equipment have made it more reliable and the cost of operating it cheaper, Arroyo said.
Today, the technology is widespread throughout Texas with 45 systems in operation treating 120 million gallons of water a day.
El Paso has the largest desalination system in the state, Arroyo said, and that city pumps its concentrated salt water from the plant into an injection well.
Some industrial operations that use reverse osmosis to remove the salt from water do not even have a disposal problem. Often the operations are able to recycle the water back into their systems.
Arroyo said oil and gas businesses have found uses for the heavier brine left over from a reverse osmosis plant.
The engineer said about 400,000 acre-feet of desalinated water are expected to be added to Texas water systems in the coming years.
That increase will be important, Arroyo said. Over the next 50 years, existing water supplies in Texas are expected to decline by 10 percent.
Arroyo pointed out 10 reasons for increased desalination in Texas.
1. There are 3.7 million acre-feet of brackish water in Texas. “That’s a lot of water,” Arroyo said.
2. Desalination creates a new source of water where existing supplies are already claimed.
3. Brackish water is available throughout most of Texas.
4. Brackish water offers communities and industry a chance to diversify its water sources.
5. Desalination is fairly easy to implement.
6. Desalination is a robust technology.
7. Scalability, meaning it is easy to expand desalination systems when needed.
8. Desalination can be accomplished on a local or regional level.
9. Reuse multiplier, meaning that even treated wastewater can be filtered to a “very high standard.”
10. Challenges to opportunities, which mean many communities are looking at using desalination in future water plans.
One resident at the meeting asked why the city was proposing the construction of a 3 mgd reverse osmosis system instead of a 1 mgd plant.
Engineer Bill Norris of NorrisLeal Engineering Water in Austin had already answered that question.
Norris said at the beginning of the meeting that cost-of-scale makes it cheaper to treat 2-3 mgd of water than to treat 1 mgd.
Arroyo then explained that there are a number of ways for a city to obtain assistance in funding deslination projects.
He said his agency, the TWCB, could provide some funds and the federal government also assists in funding water projects.
Judy Adams, operator of the Southmost Texas Regional Water Project in Brownsville, explained that about 26 percent of the water that city uses comes from brackish groundwater supplies and the rest comes from surface water sources.
Until 2000, that city used primarily water taken from the Rio Grande.
Today, Brownsville runs a 7.5 mgd plant 24 hours a day, seven days a week.
Kevin Spencer of R.W. Harden & Associates in Austin described the water in the Jasper aquifer, where plans call for Beeville to get water for the reverse osmosis plant, as “slightly brackish.”
That aquifer was the primary source of Beeville’s water until the current surface water system was built by the Beeville Water Supply District.
Today, Spencer said, there is no competition for water from that aquifer. Most of the smaller wells in Bee County take water from the Evangeline (Goliad) aquifer. Spencer described the Goliad as the “local aquifer.”
Although the Bee Groundwater Conservation District has control of that aquifer outside of the city, it would not have control of the use of that water from a well drilled on city property.
Spencer said the choice of the Jasper aquifer for the city’s project would be good “because the city would have complete control of it.”
Gary Kent is a reporter at the Bee-Picayune and can be reached at 358-2550, ext. 120, or at reporter@mySouTex.com.