Main

Outreach Program

Contact Us

Definitions & FAQ

Definitions & Frequently Asked Questions

General Questions

1. What is desalination?
2. Why is SAWS looking at ocean desalination?
3. How common is it?
4. How does SAWS intend to keep my community involved and informed throughout this process?
5. Is SAWS working with River Authorities and/or Groundwater Conservation Districts?
6. What is the anticipated yield of SAWS’ ocean desalination project?
7. Would the project be funded entirely by SAWS ratepayers?

Technical Questions

8. What is the difference between brackish water, ocean or sea water, and brine/concentrate?
9. Is it cheaper to desalinate bay water as opposed to ocean water?
10. How would SAWS dispose of brine (or concentrate)?
11. What are some of the other potentially beneficial uses of the concentrate other than disposal?
12. Would SAWS be drilling wells along the pipeline?
13. How far out into the ocean will the intake structure be? How about the concentrate disposal?
14. How far inland are ocean desalination reverse osmosis (RO) plants usually located?
15. What are some of the advantages of Reverse Osmosis membranes?

General Questions

1. What is desalination?
   Desalination is the process of removing dissolved salts from water. The two most common desalination technologies are thermal and membrane technologies. The thermal process involves heating saline water to produce water vapor, which is then condensed and collected as fresh water. Membrane processes rely on permeable membranes to separate salts from water. Membrane processes can be pressure-driven (reverse osmosis or RO, the most common method used in desalination), or voltage-driven (electro-dialysis).



2. Why is SAWS looking at ocean desalination?
   SAWS recently completed a review and revision of its 50-year water management plan. The plan identifies the need for additional supplies in the future, about 75,600 acre-feet between 2035 and 2060. The additional supply is intended to supplement and diversify SAWS' existing water inventory, which currently consists of Edwards Aquifer groundwater, Trinity Aquifer groundwater, Carrizo Aquifer groundwater, Canyon Lake surface water, recycled water, and water stored in the SAWS aquifer storage and recovery (ASR) site.



3. How common is it?
   Desalination of water is a common practice. In recent years, about 38 public water supply systems in Texas used desalination facilities to treat brackish groundwater. The largest facilities are in Abilene, Sherman, Brownsville, and Fort Stockton. The City of El Paso and Fort Bliss Army post has opened what is reported to be the world's largest inland brackish groundwater desalination plant. More recently, SAWS is currently moving forward with design and construction of a brackish groundwater desalination facility in southern Bexar County. Other states utilizing brackish groundwater for a portion of their drinking water include Alaska, Alabama, California, Colorado, Florida, Iowa, Illinois, North Dakota, New Jersey, Ohio, South Carolina, and Virginia.


Currently, there are no ocean water desalination plants operating in Texas; however, some cities (Brownsville, South Padre Island) are beginning to develop programs. There are some facilities operating in other states, such as Florida and California. Several other countries also rely on desalination to treat ocean water for drinking. The Middle East and the Caribbean rely heavily on the process.


4. How does SAWS intend to keep my community involved and informed throughout this process?
   SAWS Ocean Desalination Outreach team has met with key stakeholders in more than 30 counties in southeast Texas. Going forward, the team will hold meetings to update various stakeholders, including elected officials, groundwater conservation districts, regional planning groups, environmental entities, and concerned citizens.



5. Is SAWS working with River Authorities and/or Groundwater Conservation Districts?
   Early outreach efforts focused on elected officials in the region. SAWS is now moving forward with communications with groundwater conservation districts, river authorities, regional planning groups, groundwater management areas and other interested groups in the area.



6. What is the anticipated yield of SAWS' ocean desalination project?
   At this time, SAWS does not have an anticipated project yield. While SAWS Water Management Plan Update shows an annual water supply need of 75,600 acre-feet in 2035 – 2060, the actual project yield would be developed at a later date. The project yield would be determined by SAWS anticipated supply needs as well as the water needs for other communities that may want to participate in this project.



7. Would the project be funded entirely by SAWS ratepayers?
   SAWS would likely pursue financial assistance when available, such as a Texas Water Development Board loan or grant. This would supplement contributions from SAWS ratepayers via the Water Supply Fee as well as any other participating entities. There is potential for the development of a regional project in which other participating entities could share the costs associated with the project.

Technical Questions

8. What is the difference between brackish water, ocean or seawater, and brine/concentrate?
   The primary difference between the types of water mentioned above is in the amount of total dissolved solids (TDS) they contain. Brackish water typically contains TDS in concentrations ranging from 1,000 milligrams per liter (mg/l) to 10,000 mg/l. Saline water or saltwater has more than 10,000 mg/l TDS. And, brine is very salty water (TDS greater than 35,000 mg/l). Seawater typically is very salty (TDS >35,000 mg/l).



9. Is it cheaper to desalinate bay water as opposed to ocean water?
   As a function of salinity, the higher the TDS, the more expensive it is to treat. In a reverse osmosis system, the greater the TDS concentration of the water, the higher the pressure needed for the pumps to push water through the membranes, which results in higher energy costs.



10. How would SAWS dispose of brine (or concentrate)?
    Concentrate management (or brine disposal) can become one of the most important factors in determining the feasibility of a plant. Concentrate produced during seawater desalination can be disposed through deep well injection on land or returned to the ocean in a controlled process that avoids impact to the environment or marine life. For concentrates produced in inland facilities, other options exist, such as disposal to surface water bodies, evaporation ponds, or wastewater treatment plants.



11. What are some of the other potentially beneficial uses of the concentrate other than disposal?
    Concentrate can be diluted for irrigation, wetland, livestock, and industrial applications. However, dilution is only appropriate for brackish groundwater concentrates, which have a much lower TDS than ocean water.



12. Would SAWS drill wells along the pipeline?
    No, SAWS would not drill wells along a pipeline.



13. How far out into the ocean would the intake structure be? How about the concentrate disposal?
    The placement of intake and disposal structures is unknown at this time. The placement of each structure would be determined during the various project studies.



14. How far inland are ocean desalination reverse osmosis (RO) plants usually located?
    The majority of ocean desalination RO plants are located less than a mile from the coast. Raw water intake and concentrate disposal infrastructure have a high cost per mile, so it is most cost effective for the RO plant to be close to the source water. Rising sea levels and the tidal range also have to be taken into account when deciding on a site for an ocean desalination RO plant.



15. What are some of the advantages of reverse osmosis membranes?
    Advantages include lower energy requirements, short start-up and shut-down time, lower maintenance requirement, operational flexibility, and no atmospheric pollution.