Chloride and Sulphate in Water: What They Mean and How RO Treats Them
Quick answer: how are chloride and sulphate removed from water?
Reverse osmosis can reduce chloride and sulphate because both are dissolved ions, but treatment performance depends on membrane type, pressure, recovery, feed composition and system condition. Their concentrations should be measured directly rather than inferred from TDS alone.
Why chloride matters
Chloride contributes to salinity and can increase corrosion risk for some metals and operating conditions. High chloride also increases the dissolved-solids load that an RO system must reject.
Why sulphate matters
Sulphate contributes to dissolved solids and can participate in mineral scaling with ions such as calcium, barium or strontium when concentrations and recovery create supersaturation.
What should be checked before RO design?
- Chloride concentration
- Sulphate concentration
- Hardness and alkalinity
- Barium and strontium where relevant
- Silica
- pH and temperature
- Target recovery
Frequently asked questions
Does a water softener remove chloride?
No. A standard sodium-cycle softener exchanges hardness ions but does not remove chloride.
Does a water softener remove sulphate?
Not in a standard hardness-softening configuration.
Can RO reduce both chloride and sulphate?
Yes, RO can reduce both, but actual rejection and safe recovery depend on the membrane and feed-water chemistry.
See ABHIRO’s RO Salt Rejection Guide, Silica Scaling Guide and Knowledge Centre.
