Sulphate Removal From Water

Sulphate is widely distributed in nature and may be present in natural waters at a range of concentrations. High sulphate concentrations can be present in groundwater, and is common in mining/industrial wastewaters where sulphuric acid is used. Sulphate can cause:

  • Taste and health issues when present above 250 mg/L in drinking water
  • Scaling or corrosion issues which can damage equipment in water treatment, mining, or industrial processes
  • Environmental issues when discharged to rivers or lakes, or when injecting into an aquifer

Sulphate discharge limits vary between countries, when being discharged to the environment, with most countries opting for a limit in the range of 250-1000 mg/L.

DESALX® Technology For Sulphate Removal

Our DESALX® technology is well suited for large-scale, low OPEX sulphate removal from water, and has zero liquid discharge (ZLD) capabilities.

DESALX® consists of two CIF® (continuous ionic filtration) modules in series, first removing multivalent cations such as calcium and magnesium, followed by multivalent anions such as sulphate. CIF® provides a combination of physical filtration and continuous counter-current ion exchange, allowing a higher tolerance for suspended solids and more efficient adsorption and desorption than batch ion exchange.

Each CIF® module in DESALX® is made up of four columns, each designed for a specific function – ionic filtration, resin cleaning, resin regeneration and resin washing. Ion exchange resin is cycled between columns roughly hourly using an air lift pump allowing continuous operation and regeneration of the system. Since the resin is moving around the system there is a higher tolerance to precipitates formed during desorption, allowing less expensive lime and sulphuric acid to be used for regeneration.

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Example Layout of DESALX® Technology

Monovalent ions such as sodium and chloride aren’t removed by DESALX®, which avoids creating a saline brine. As a result, DESALX® produces a gypsum based brine, which an be paired with existing lime precipitation systems on site to produce gypsum solids for a true zero liquid discharge (ZLD) solution. If lime precipitation isn’t available, DESALX® can be used with a high density sludge (HDS) clarifier to achieve ZLD.

DESALX® provides the following advantages:

  1. Ultra low OPEX, typically $0.5-0.8 USD/m3 for ZLD flowsheets
  2. Membrane free, with no scaling/fouling issues
  3. No pre-treatment required
  4. Continuous movement of fixed bed resins to remove suspended solids
  5. Only removes multivalent cations and anions, producing a gypsum based brine instead of a saline brine to remove the need for expensive evaporation ponds or evaporators
  6. Uses sulphuric acid and lime instead of more expensive hydrochloric acid and caustic to regenerate resins
  7. Minimal power requirements
  8. Synergises with RO by removing scale forming ions and allowing higher RO recovery
  9. Fully automatic system that adjusts for feed water quality and flowrate

When treating water with sulphate concentrations above 3000 mg/L, Clean TeQ Water can provide a flowsheet which integrates lime softening with DESALX® to achieve very low sulphate concentrations in the product water.

DESALX® Case Studies For Sulphate Removal

Gold Mine, Australia

gold mine

Clean TeQ Water installed an 80m3/h (2MLD) water treatment plant that uses arsenic/antimony precipitation, followed by DESALX® to achieve the water quality required for aquifer reinjection. DESALX® reduces the hardness and sulphate concentrations in the water and acts as a pre-treatment for the RO on site to reduce operating expenditures when water is required to be reused. Water recovery is in excess of 90% and the system is fully automated in order to achieve a consistent water quality across the required range of flowrates.

SpeciesUnitFeed WaterProduct Water
pH4.56.0-9.0
Total Dissolved Solidsppm7,4005,848
Calciumppm30085
Magnesiumppm32196
Sulphateppm1515700
Iron (soluble)ppm50.1

Antimony Ore Roasting Plant, Oman

Oman clean 1 2

Clean TeQ Water provided a 0.5MLD plant in Oman which uses DESALX® to remove hardness and sulphate before water continues to RO. The plant produces industrial quality water which is reused as process water, as part of a zero liquid brine water treatment solution.

SpeciesUnitFeed WaterProduct Water
Calciumppm77949.41
Sulphateppm1,871.00134.14
Total TDSppm2,650280
Cations (meq/L)38.883.35
Anions (meq/L)38.964.95
Gypsum Waste (kg/h) 28

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