Introduction
One of the most readily available but least used alternative water sources in the world is brackish water which is characterized by a TDS of between 1,000 and 10,000 mg/L. With growing population and climate change putting an increasing strain on fresh water, treatment of brackish water has gained high priority on the list of conflicts over the Middle East, South Asia and coastal regions throughout the world. With increasing demand for clean water and advanced water purification technologies, many industries now rely on professional water treatment solutions for sustainable water management.
Is it possible to purify brackish water? Yes and no, it can be cut to less than 300 mg/L TDS with the appropriate technology, which completely meets the requirements of drinking water standards set by WHO.
For a complete foundation on what brackish water is, read our Pillar Guide: Brackish Water Explained | Sources & Treatment Methods 2026
The reason why Brackish Water needs Treatment?
Common municipal treatment, e.g. coagulation, sand filtration and chlorination, can handle most biological contamination and suspended solids, but not dissolved ionic salts. Brackish water contains a lot of sodium (Na + ), chloride (Cl – ) and sulfate (SO 2 2 ), calcium (Ca 2 +), magnesium (Mg 2 +) and in most underground water sources, there are heavy metals, which include iron, manganese, arsenic and fluoride. These need membrane-based, electrochemical, or thermal treatment technologies are done away with.
| Contaminant Type | Conventional Treatment | Specialized Treatment Required |
| Suspended solids / turbidity | Yes | Sediment filtration |
| Bacteria and viruses | Yes | Disinfection |
| Chlorine and organics | Yes | Activated carbon |
| Dissolved salts (Na⁺, Cl⁻) | No | RO / EDR / Distillation |
| Sulfate (SO₄²⁻) | No | RO / Nanofiltration |
| Hardness (Ca²⁺, Mg²⁺) | Partial | Ion exchange / RO |
| Heavy metals (Fe, Mn, As) | Partial | RO / Specialized media |
| TDS reduction | No | RO / EDR / Thermal |
Overview of Treatment procedures of Brackish Water
| Treatment Method | TDS Removal | Operating Principle | Best TDS Range | Energy Use | Scale |
| Brackish Water RO (BWRO) | 95 – 99% | Pressure-driven membrane | 1,000 – 10,000 mg/L | Low-Medium | All scales |
| Electrodialysis Reversal (EDR) | 80 – 95% | Electrochemical ion migration | 1,000 – 5,000 mg/L | Medium | Medium-Large |
| Capacitive Deionization (CDI) | 60 – 90% | Electrostatic ion adsorption | 500 – 3,000 mg/L | Low | Small-Medium |
| Multi-Stage Flash (MSF) | > 99% | Thermal evaporation | Any | Very High | Large industrial |
| Multi-Effect Distillation (MED) | > 99% | Thermal evaporation | Any | High | Large industrial |
| Forward Osmosis (FO) | 85 – 98% | Osmotic pressure differential | Any | Low | Pilot/emerging |
| Ion Exchange (IX) | 60 – 85% | Chemical ion substitution | 500 – 3,000 mg/L | Low | Small-Medium |
| Nanofiltration (NF) | 50 – 70% | Pressure-driven membrane | 1,000 – 5,000 mg/L | Medium | Medium |
Method 1 – Brackish Water Reverse Osmosis (BWRO)
How does RO treat brackish water?
The global gold standard of brackish water treatment is BWRO – the most deployed, least expensive and best-technically proven brackish water treatment technology of any scale.
How it works: Hydraulic pressure of 250 to 400 psi is applied across a polyamide thin-film composite (TFC) membrane with 0.0001 micron pore size. Water molecules are filtered and dissolved ions are rejected. Feed water is divided to permeate (6080% of feed, TDS lowered 9599) and brine concentrate directed to separate disposal.
| Parameter | Specification |
| Feed Water TDS Range | 1,000 – 10,000 mg/L |
| Operating Pressure | 250 – 400 psi (17 – 28 bar) |
| Membrane Type | Polyamide thin-film composite (TFC) |
| Salt Rejection Rate | 95 – 99% |
| Water Recovery Rate | 60 – 80% |
| Product Water TDS | 50 – 300 mg/L |
| Energy Consumption | 0.5 – 1.5 kWh/m³ |
| Membrane Lifespan | 3 – 7 years |
| Operating Temperature | 5 – 45°C |
Method 2 – Electrodialysis Reversal (EDR)
EDR operates on direct electric current with ion-selective membranes to remove dissolved cations and anions out of the feed stream into a concentrate stream – no high-pressure pumping is needed.
Mechanism: The stacking between electrodes is alternating cation and anion exchange membranes. Na +, Ca +, Mg + are pushed to the cathode and Cl -, SO 4 -, HCO 3 – are pushed to the anode by applied DC current, eliminating them in the product stream. Periodic reversal of polarity inhibits membrane scaling and biofouling.
| Parameter | Specification |
| Feed Water TDS Range | 500 – 5,000 mg/L |
| Salt Removal Efficiency | 80 – 95% |
| Energy Consumption | 0.5 – 2.5 kWh/kg salt removed |
| Water Recovery Rate | 80 – 94% |
| Feed Turbidity Tolerance | Up to 5 NTU (higher than RO) |
| Membrane Lifespan | 7 – 10 years |
Method 3 – Capacitive Deionization (CDI)
CDI isolates dissolved ions through the electrostatic adsorption of the ions onto the high-surface-area carbon electrodes at extremely low voltage – and is therefore used in off-grid and solar-driven systems.
Mechanism: DC (1.2 to 1.6V) across porous carbon electrodes causes cations to be drawn to the negative electrode and anions to the positive electrode, filtering salts through passing water. Once the electrodes become saturated, voltage is reversed, and a small volume of concentrate is flushed, and the process is repeated.
| Parameter | Specification |
| Feed Water TDS Range | 200 – 3,000 mg/L |
| Salt Removal Efficiency | 60 – 90% |
| Operating Voltage | 1.2 – 1.6V DC |
| Energy Consumption | 0.1 – 0.5 kWh/m³ |
| Water Recovery Rate | 70 – 85% |
| Electrode Lifespan | 3 – 5 years |
Method 4 – Multi-Stage Flash Distillation (MSF)
MSF is a thermal desalination system that recycles distillate water to produce ultra-pure distillate by continuously boiling heated sea water into steam in 15-25 increasingly low pressure stages – commonly used in UAE, Saudi Arabia and Kuwait.
Mechanism: Feed water is heated to 90 to 120 C, and the feed water passes through a series of flash stages with decreasing pressure resulting in instant partial evaporation. The condensate that forms on cooler tubes is pure distillate. The left-over saline water flows through it all.
| Parameter | Specification |
| Product Water TDS | < 10 mg/L |
| Top Brine Temperature | 90 – 120°C |
| Energy Consumption | 10 – 16 kWh/m³ |
| Plant Capacity | 5,000 – 75,000 m³/day per unit |
Method 5 -Multi-Effect Distillation (MED)
Instead of using latent heat of evaporation through just 1 to 2 effects at a single temperature and pressure, MED takes advantage of the latent heat of evaporation by recrystallizing at 8 to 16 effects with lower temperatures and pressure.
| Parameter | MED | MSF |
| Energy Consumption | 5 – 9 kWh/m³ | 10 – 16 kWh/m³ |
| GOR (kg distillate/kg steam) | 8 – 16 | 8 – 10 |
| Top Operating Temperature | 60 – 70°C | 90 – 120°C |
| Scaling Risk | Lower | Higher |
| Capital Cost | Moderate | High |
Method 6 Forward Osmosis (FO).
FO uses natural osmotic pressure difference between high-concentration draw solution and brackish feed water to drive water across a semi-permeable membrane – no applied hydraulic pressure is needed.
| Parameter | Specification |
| Operating Pressure | Near-zero (osmotically driven) |
| Salt Rejection | 85 – 98% |
| Energy Consumption | 0.25 – 0.84 kWh/m³ (membrane step only) |
| Current Status | Pilot and semi-commercial scale |
Method 7 — Ion Exchange (IX)
In ion exchange resins, the feed water uses specific ions, which are replaced by less harmful ions on charged polymer beads. Not feasible as a standalone TDS reduction technology in high-salinity brackish water – but very much effective as a specific, regulated contaminant removal technology.
| IX Application | Ion Targeted | Effectiveness |
| Water softening | Ca²⁺, Mg²⁺ | High |
| Nitrate removal | NO₃⁻ | High |
| Fluoride removal | F⁻ | High |
| Arsenic removal | As³⁺/As⁵⁺ | High (with Fe-based media) |
| Full TDS reduction | All ions | Not practical for BW |
Method 8 — Nanofiltration (NF)
NF membranes (0.001 micron pore size, 200-1,000 Dalton MWCO) reject divalent ions (Ca 2+, Mg 2+, SO 4 2- ) at 85-98% and pass a portion of monovalent ions (Na +, Cl -), operating at lower operating pressure than full RO.
| Parameter | Nanofiltration | Brackish Water RO |
| Operating Pressure | 75 – 250 psi | 250 – 400 psi |
| Divalent ion rejection | 85 – 98% | 95 – 99% |
| Monovalent ion rejection | 20 – 50% | 85 – 95% |
| TDS Reduction | 50 – 70% | 95 – 99% |
| Water Recovery | 75 – 90% | 60 – 80% |
Treatment of Brackish Water in UAE.
UAE possesses practically no perennial surface water and less than 20 m 3 per capita renewable freshwater each year – some of the lowest in the world. Average TDS in brackish groundwater in Abu Dhabi, Al Ain, Sharjah and Ras Al Khaimah is 2,000-8,000 mg/L and this is a large source of untapped water.
The main reasons why brackish water should be treated in the UAE?
- Its supply should be diversified other than energy-intensive seawater desalination.
- Increasing industrial process water demand in manufacturing, food processing and pharmaceuticals.
- Irrigation in oasis farming areas.
- Mandates on sustainability and carbon footprint.
UAE potable drinking water standards (ESMA): TDS less than 600 mg/L, sodium less than 200 mg/L, chloride less than 250 mg/L, sulfate less than 250 mg/L, turbidity less than 1 NTU, pH 6.5-8.5, none of the coliforms detected.
The Way to Choose the Appropriate Treatment Method
| Selection Factor | Recommended Technology |
| TDS 1,000 – 10,000 mg/L, potable water | BWRO (single pass) |
| TDS 1,000 – 3,000 mg/L, maximum recovery | EDR |
| TDS < 2,000 mg/L, off-grid solar | CDI or Solar BWRO |
| TDS > 5,000 mg/L, ultra-high purity | Two-pass BWRO |
| Hardness and sulfate removal only | Nanofiltration |
| Large industrial with co-generation steam | MED or MSF |
| Selective ion removal (nitrate, fluoride) | Ion Exchange + BWRO |
Conclusion
Brackish water treatment is a solution to fresh water shortage on a global scale – pioneered by BWRO, enabled by EDR, CDI, thermal distillation and new FO technologies. To choose the appropriate method, it is necessary to evaluate in a systematic way feed water TDS, product quality goals, energy availability, system size and budget. BWRO is the best option in most of the applications, however, knowing the entire range of technology is bound to get the right solution in all scenarios.
Brackish Water Explained | Pillar Guide
FAQs
Is it possible to cleanse brackish water to be used as drinking water?
Yes. BWRO can be used to filter up to 10,000mg/L of TDS to less than 300 mg/L, which is completely safe drinking water as per the WHO drinking water standards.
Which is the best way of treating brackish water?
BWRO — with 95-99% removal of TDS, proven reliability, modular scalability and the most economical energy in the entire 1,000-10,000 mg/L TDS.
What is the treatment of brackish water by RO?
The pressure of 250-400 psi causes water molecules to pass through a 0.0001 micron TFC membrane and reject dissolved salt ions leaving low-TFS permeate and a concentrated brine reject stream.
