About Brackish Water Treatment Systems

Brackish Water or Well Water is water that is more salty than potable fresh drinking water, in other words is has a higher salinity concentration levels, but not as much as sea water. The word originally deviate from the Dutch root of “Brak” meaning "salty".
Brackish water condition commonly occurs when fresh water meets sea water. In fact, the most extensive brackish water habitats worldwide are where a river meets the sea.
The term “brack” or Brackish was first used to describe bodies of waters that had been mixed with seawater in the 1500s, Brackish Water was not as salty as seawater, yet very distasteful, and was described as harmful water due to its characteristics and to unique microorganisms that caused human illness .

Brackish water usually contains from 0.5 to 30 grams of salt per liter (500 to 30,000 ppm or mg/L), however, the brackish water salinity concentrations may vary considerably over space and time.
In general Brackish Water is a term for water that contains a significant concentration of dissolved salts (Na Cl). The concentration is usually expressed in parts per million (PPM) or milligram per liter (mg/L) of salt. Brackish Water that is saline contains significant amounts (referred to as "concentrations") of dissolved salts
The salinity concentration is the amount of salt in the water by weight, as expressed in "parts per million" (PPM). For example if water has a concentration of 5,000 ppm of dissolved salts, then one percent (5,000 divided by 1,000,000) of the weight of the water comes from dissolved salts.

The salinity concentration level used by US Geological Survey classifies brackish water in three categories.

1- Slightly saline water contains around 1,000 to 3,000 ppm.
2- Moderately saline water contains roughly 3,000 to 10,000 ppm.
3- Highly saline water has around 10,000 to 35,000 ppm of salt.

Brackish Water can be found in wells, boreholes, mangrove swamps, inland lakes and seas. The Caspian Sea which is very famous for the great sturgeons fish (source of the best caviar in the world) is the largest brackish lake in the world with a salinity level of 1.2%, (12,000 PPM) about one third that of normal seawater. The Baltic Sea is another example of brackish water, the Baltic Sea has the least Saline concentrations in the world with a salt concentration of 0.5% (5000 PPM) compared to the Red Sea and the Persian Gulf both with a salt concentration of about 4.5% (45,000 PPM)

What is Brackish Water?

Brackish water is water that has more salinity than fresh water but less than seawater. It typically measures between 0.5 and 30 parts per thousand (ppt) dissolved salts — compared to the ocean's average salinity of around 35 ppt. Brackish water is commonly found in surface waters near river mouths, estuaries, and coastal areas where freshwater and saltwater mix. Inland brackish sources include certain lakes, aquifers, and water wells with elevated total dissolved solids (TDS).

Natural ecosystems such as mangrove forests thrive in brackish environments and are closely associated with estuarine and coastal brackish water zones. For water treatment purposes, brackish water (typically 1,000–10,000 mg/L TDS) requires desalination or reverse osmosis treatment to produce potable drinking water or process-grade water suitable for industrial, agricultural, or municipal use.

Brackish water is found in coastal lagoons, estuaries, and inland aquifers across many coastal areas of the world. It is defined by salinity between 0.5 and 30 parts per thousand — above freshwater but significantly below the average salinity of seawater. Brackish surface waters and groundwater sources support unique ecosystems — including mangrove forests — and serve as critical water supply sources for communities and industries in arid and semi-arid regions.

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Frequently Asked Questions

Brackish Water Treatment:

Most Brackish Water can be treated with a Reverse Osmosis Water Purification System, however, desalinating brackish water occurs at lower pressure compared to seawater desalination, resulting in more economical process, less energy consumption and more cost efficient.

Standard Reverse Osmosis Systems

Treat water with a salinity concentration of up to 5,000 PPM

Brackish Water Reverse Osmosis

Treat water with a salinity concentration of up to 10,000 PPM

Seawater Reverse Osmosis Systems

Treat water with a salinity concentration of up to 50,000 PPM

All Reverse Osmosis Systems require sufficient pre-treatment to ensure proper production, operation and to preserve its operational life. Pre-treatment process is engineered depending on feed water quality, water conditions and flow rates required.

Under sized pre-treatment process may cause a system overload, increasing the plant’s internal parts damage and usage, requiring more service and maintenance which will interrupt normal operations more often, and this will reduce productivity and increase cost.

Under sized pre-treatment will also increase scaling, fouling and plugging of the membrane elements which is the most expensive part of the reverse osmosis process.

The kind of pre-treatment system that is used greatly depends on feed water quality. Consequentially, sufficient feed water pre-treatment is dependent on:
· The source of the feed water
· The composition of the feed water
· The function of the feed water
We always require an exact water analysis report before we commence the manufacturing process of a reverse osmosis project in order to design and build a complete and a correct Reverse Osmosis system with its pre-treatment, fully equipped and fully automated specifically designed and engineered for the specifications, conditions and the requirements of the project.

What is brackish water and how does it differ from seawater?

Brackish water has a salinity between freshwater and seawater – typically 1,000–10,000 ppm TDS vs 35,000 ppm for seawater. Sources include inland wells, estuaries, coastal aquifers affected by saltwater intrusion, and some surface water bodies. Lower operating pressure (150–400 psi vs 800–1,000 psi for seawater) makes brackish water desalination more energy-efficient and economical.

What flow rates do AMPAC USA brackish water RO systems handle?

AMPAC USA brackish water RO systems range from 1,000 GPD compact units for small communities and agricultural users up to 1 million GPD for municipal desalination projects. Systems are modular and can be paralleled for high output. Recovery rates of 70–85% are typical for brackish sources – higher than seawater systems due to lower osmotic pressure.

What pre-treatment does brackish water RO require?

Pre-treatment for brackish water typically includes:

Multimedia filtration – removes suspended solids and turbidity
Antiscalant dosing – prevents carbonate, sulfate, and silica scaling at higher recovery rates
Cartridge filters (5 micron) – final particle guard before high-pressure pump
pH adjustment – optimizes carbonate equilibrium and membrane rejection

AMPAC USA performs a Langelier Saturation Index (LSI) calculation from your water analysis to design the correct antiscalant program.

Can brackish water be treated to drinking water standards?

Yes. AMPAC USA brackish water RO systems routinely produce permeate at 50–200 ppm TDS from source water at 2,000–8,000 ppm – well within EPA drinking water standards. For potable applications, post-treatment includes pH neutralization, UV disinfection, and chlorination for residual protection in distribution.