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Desalination involves removing salt and other dissolved solids from water that is otherwise not suitable for the intended use. This process can be used to turn saline water into fresh water for drinking and other purposes.

Reverse osmosis, one of the most common desalination processes, uses high pressure to propel water through a membrane that separates out salt and other minerals.

Desalination can be used for both brackish water and seawater.

Brackish water is less salty than seawater (it contains between 1,000 and 10,000 milligrams of salt and other dissolved solids per liter of water). Brackish desalination in Texas usually draws from salty aquifers, where water is found underground, but sometimes also pulls from certain salty rivers like portions of the Brazos River. Desalinating water from rivers and bays could become more common in Texas in the future.

Although there are a number of small brackish water desalination plants in Texas, some of which are locally-important supply sources, this is not yet a major source of water supply in the state.

Seawater desalination is rarer, more expensive and more energy-intensive than brackish desalination. (Seawater typically contains more than 35,000 milligrams of salt and other dissolved solids per liter of water.)

As of May 2018, Corpus Christi has begun officially planning to construct the first seawater desalination plant in Texas to be used for drinking water.

Desalination in Texas

El Paso’s brackish water desalination plant is the largest in Texas and can produce up to 27.5 million gallons of water per day (mgd), though on average it produces only 4.2 mgd. For context, in 2013 El Paso used an average of 99.8 mgd.

The majority of desalination plants in Texas produce less than 1 mgd. Larger-volume plants are uncommon because of the high expenses involved.

Desalination report card
This strategy is promising on some fronts, but there are some real concerns.

Different impacts exist depending on the water’s source and where brine is disposed; for example, there are many concerns associated with desalinating coastal waters. Less problematic alternatives may include locating desal plants further offshore, or using brackish groundwater instead of surface water. In general, extreme caution and care need to be taken in locating and designing desalination plants to make sure they do not harm rivers, bays, aquifers and wildlife.

True costs
When compared to other strategies, it’s hard to see the benefit of this one.

There are different true cost considerations depending on how salty the source water is and how much of it is being desalinated. With current technology, there is often a notably high price tag attached to desalination. This is due in large part to its energy needs and the costs of appropriately disposing of brine.

Long-term viability
This strategy is promising on some fronts, but there are some real concerns.

Desalination has intensive energy needs, which pose numerous long-term viability issues, including increased carbon emissions. However, it can be a lifeline for communities impacted by serious drought or with no other viable options.

Desalination grade breakdown
Environmental impacts
  • Desalination allows communities to diversify their water supply mix, which lessens the need to withdraw fresh water from rivers and aquifers and leaves more water for wildlife.
  • Pulling water from a coastal bay or estuary can suck up and kill large numbers of juvenile shrimp, crabs and other fish, as well as their eggs. It can also capture the less-salty water needed to dilute saltier ocean water, disrupting the critical salinity balance that helps make estuaries one of the most life-filled ecosystems in the world. (Locating this process farther offshore may minimize those impacts.)
  • Brine, which is the salt and other minerals removed from the water during desalination, must be disposed of.
  • When it is disposed into bays, it can artificially elevate salinity levels and stress or kill aquatic wildlife. (Carefully located disposal into the open ocean may minimize those impacts.)
  • When disposed of into fresh surface water, it increases the water’s salinity, as well as its levels of other chemicals. This can have serious water quality consequences for aquatic life and downstream water users.
  • Brine can be injected underground, but unless done carefully, it can contaminate freshwater aquifers.
  • Water often moves between adjacent aquifers. Because of this connectivity, pumping brackish groundwater for desalination could impact aquifers in ways that we don’t yet entirely understand.
  • Desalination plants, because of their high energy usage, cause additional air pollution and emissions.
There are really two major issues here. One is the [brine] discharge, and the other is the [brackish water] intake.
True costs

1 Desalination costs vary depending on the volume of water being desalinated and how much salt and other minerals are in the water. In addition to construction costs, maintenance and operations costs include intensive energy production and regularly cleaning membranes. These costs are passed on to residents through higher water rates.

2 If energy becomes more expensive and associated carbon emissions become more regulated, both of which are expected to happen, this will drive desalination costs higher.

3 When desalination plants pull water out of bays and estuaries, this may disrupt nurseries for economically-vital commercial fish species. It may also harm oyster reefs, which act as important storm surge barriers for coastal communities. Likewise, if brine is disposed of into sensitive habitats, this could have similar impacts.

Long-term viability

1 Desalination is an energy-intensive supply option, which ultimately requires fresh water for energy production. This means that even though it frees up new water sources, this strategy isn’t without continuing long-term water needs.

2 Carbon emissions from electrical energy generation are a global concern for many reasons, including their impacts on health, quality of life and the economy. Whether this concern applies to a particular desalination plant depends on its source of energy generation.

3 Droughts are predicted to become more frequent and intense in Texas, which threatens freshwater availability across the state. On a small scale and as a part of a larger portfolio of water supply solutions, desalination can be a much-needed supplement to other supply sources during dry times when there is not enough fresh water to support communities and the environment.

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