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What is Brackish Water and How Do You Treat It?

Posted by John Woodard on April 22, 2021

Access to safe drinking water is one of the great challenges of modern times. According to the World Health Organization (WHO), 1 in 3 people worldwide don’t have access to safe drinking water, and a global population expected to reach 8 billion by 2023 will further exacerbate the problem. Water comprises 71 percent of earth’s surface, but only three percent is fresh water, and only about one percent is suitable for drinking. Evidently, there is no shortage of salt water on our planet, and a solution to the global water crisis may lie in the treatment of slightly salty brackish water. Brackish water has salinity levels between fresh water and seawater and is considerably easier to desalinate than the latter. Below you will learn about brackish water, how it is treated, and how it may provide a solution to the world’s growing demand for drinking water.  

What is brackish water?

Brackish water is water with salinity levels between fresh water and seawater. Salinity refers to the concentration of dissolved salts in a body of water, so brackish water is saltier than fresh water, but less salty than seawater. Brackish water has a salt concentration of 1,000 – 10,000 parts per million (PPM). In contrast, fresh water has a salt concentration of less than 1,000 PPM and seawater has a salt concentration of 30,000 – 40,000 PPM. Also, the total dissolved solids (TDS) level of brackish water far exceeds that of drinking water. The Environmental Protection Agency’s guideline for drinking water is less than 500 PPM, while brackish water is between 3,000 and 10,000 PPM.

The easiest way to visualize brackish water is to picture where a river meets an ocean. The transition of fresh river water to salty seawater creates brackish water. These areas are called estuaries and are home to a wide array of plants and animals that have adapted to brackish water, such as mangrove trees and oysters.

Learn More: What is TDS in Water & Why Should You Measure It?



Where is brackish water found?

Brackish water is found in estuaries, in lakes, in man-made pools and streams, and even underground in aquifers. Brackish water sources are present across the globe, and estuaries are the most common. For example, as the Thames River in London meets the North Sea, as the Hudson River in New York City meets the New York Bay, and as the Amazon River in Brazil meets the Atlantic Ocean, estuaries are formed. Also, the Caspian Sea (which despite the name is the world’s largest lake) contains brackish water because of an ancient ocean that once existed between Europe and Asia. Similar brackish lakes are found around the world, with five in India alone!

Man-made sources of brackish water include intentionally flooded marshlands for prawn farming and ensuing pools and streams from the construction of dikes, which are walls built to control the flow of water from rivers and seas.

Lastly, brackish groundwater exists underground in deep fossil aquifers. Groundwater can be brackish as the result of ancient seas, due to saltwater intrusion in coastal areas, or if water absorbs an excess of minerals, such as sodium and chloride, as it percolates into the ground. In fact, about 75 percent of all the groundwater in New Mexico is brackish. Private well water can even be brackish it draws from a brackish groundwater source. In this case, the water needs to be treated before it can be used.

Learn More: What is Groundwater Contamination and How Do You Treat It?

How do you treat brackish water?

Brackish water is treated through desalination. Desalination is a process that removes dissolved mineral salts from saline water and converts it into fresh, drinkable water. Reverse osmosis and distillation are the primary desalination technologies used to treat brackish water. Seawater can also be desalinated through reverse osmosis and distillation, but due to a higher salt content, not as efficiently as brackish water.

1.      Reverse osmosis

Reverse osmosis is the leading desalination technology globally. A reverse osmosis system applies pressure to saline water and forces it through a semipermeable membrane. The membrane’s small pores block the passage of dissolved salts and other contaminants but allow water to flow through, converting brackish water into fresh water. One of the largest reverse osmosis desalination plants is in Israel and it can produce about 165 million gallons of fresh water each day.

Learn More: What is a Reverse Osmosis System and How Does It Work? | Do I Need a Whole House Reverse Osmosis System?


2.      Distillation

Distillation is a desalination method that mimics evaporation in the atmosphere. Brackish water is heated until it evaporates into steam. Salts and minerals cannot evaporate as water can, so once the water condenses and resumes its liquid form, it is transformed into fresh water.

There are two primary distillation methods used to desalinate brackish water: multistage flash distillation and solar distillation. Multistage flash distillation is used in large-scale operations, while solar distillation is used in small-scale operations and in small communities.

·Multistage flash distillation

In multistage flash distillation, brackish water is passed through multiple chambers where it is heated and compressed under high pressure. In each successive chamber, the pressure is reduced, causing the water to rapidly boil. The vapor produced in each chamber is then condensed and collected as fresh water. Saudi Arabia is home to one of the largest multistage flash distillation systems, and it produces about 200 million gallons of fresh water each day.

·Solar distillation

In solar distillation, a pool of brackish water is covered by a transparent glass or plastic dome. Sunlight streams through the covering, evaporating the water and condensing it on the cover. The condensation, which is fresh water, then flows from the cover into a collecting trough.

Learn More: What is a Water Distiller and How Does It Work? | What is Distilled Water and Is It Safe to Drink?


What is brackish water used for?

Brackish water is used in both its natural, saline state and once desalinated. In its natural state, brackish water is used primarily as a cooling agent in the thermoelectric power industry, oil and gas industries, and in the mining industry. Also, brackish water can be used for irrigation in a practice known as saline agriculture. Certain crops, such as cabbage and oats, are salt tolerant crops that can be grown on salt-affected land and irrigated with brackish water. Saline agriculture is most common in the Middle East where it improves food security and reduces stress on scarce fresh water supplies.

Once desalinated, brackish water can be used as drinking water for humans and livestock. As freshwater scarcity intensifies, especially in arid, developing regions of the world, the treatment of brackish water provides an avenue to meet the mounting water needs of an increasing population. The presence of brackish water sources worldwide is one of the reasons it could ameliorate water scarcity, but as with every natural resource, brackish water resources must be used responsibly if they are to provide a long-term solution.

Can you drink brackish water?

No, you cannot drink brackish water because of its salty character. If you drink salty water, your kidneys will overproduce urine in order to expel the excess salt from your body, leading to dehydration. However, when desalinated and treated, brackish water is safe to drink.

How to make brackish water for an aquarium

If you’re an aquarium enthusiast, you may want to try your hand at setting up a brackish water fish tank. Certain interesting fish species, such as the spotted green pufferfish, thrive in a brackish water environment.

To set up a brackish water aquarium, you will need the following:

    • Water
    • An aquarium
    • A bucket
    • A high-quality marine salt mix or aquarium salt
    • A hydrometer to measure the salinity of the water.
    • An aquarium heater since brackish water fish prefer warmer temperatures.
  1. Fill a bucket with fresh water, leaving a little space at the top to account for the salt you will add at a later step. Then, use an aquarium heater to raise the water’s temperature. 77 degrees Fahrenheit is a good temperature to aim for, as it is warm enough for brackish water fish and is also the temperature most commercial hydrometers are calibrated to.
  2. Slowly add the appropriate amount of salt for the volume of water in your bucket. Generally, you will need ten grams of marine salt per liter of water. Stir the salt and water and let the mixture sit about twenty minutes or until all the salt dissolves.
  3. Measure the water with a hydrometer. A hydrometer gauges the salinity of water by determining its specific gravity (SG). Brackish water in an aquarium should range from 1.002 SG to 1.022 SG at a temperature of 77 degrees Fahrenheit.
  4. Once the water is ready, slowly add it to your aquarium and frequently measure the specific gravity with your hydrometer to ensure you maintain the ideal levels for your brackish water fish.

Learn More: Why You Should Use Reverse Osmosis for Your Aquarium 



What fish can live in brackish water?

Below are ten noteworthy fish species that can live in a brackish water aquarium.

    1. Spotted Green Pufferfish
    2. Figure 8 Pufferfish
    3. Betta mahachaiensis (wild betta fish)
    4. Dragon Goby
    5. Molly Fish
    6. Reed Fish
    7. Waspfish
    8. Green Scat
    9. Archer Fish
    10. Columbian Shark


If you have further questions about brackish water or any other water-related concerns, please don’t hesitate to contact us.

Comments 1-10 of 1

Am looking for supplier(s) of brackish water for a San Francisco Bay resident – any help – or info – you may have ?

William B Romkes on September 26, 2022
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