Sulfate Removal

Measure and treat sulfates, with options for high- & low-TDS 

Many industrial processes produce or depend on sulfates, which are often regulated and require cost-effective management. We monitor and moderate sulfate levels in wastewater flows, in some cases without brine by-products and the expense of brine management.

Sulfate Challenges

Sulfates are widespread in many industries such as mining, oil & gas, fertilizer production, pulp & paper, and more. Although not generally very dangerous to humans, high sulfate levels are often regulated to protect the environment.


Sulfate challenges vary significantly. For example, one of the most important considerations in deciding how to manage a sulfate-laden wastewater flow is the total dissolved solids (TDS). Once our team completes a chemistry review, most of our clients’ sulfate removal needs can be addressed with one of a high- or low-TDS approach. We provide cost-effective solutions for both.

Photo of smoke rising from coal power plants that require FGD systems
Photo of a full-scale SaltMaker ChilledCrys Plant
A full-scale SaltMaker ChilledCrys Plant

Solutions for High TDS

High TDS sulfate-laden waters (TDS~80,000–200,000 mg/L) often predominantly contain sodium sulfate: SO42- ~60,000–120,000 mg/L. To treat them, you can take advantage of two unique properties of sodium sulfate:

  1. Low osmotic pressure: concentrate sodium sulfate solutions to over 200,000 mg/L with our XtremeRO 1800 ultra-high pressure reverse osmosis systems
  2. Steep solubility-temperature relationship: crystallize sodium sulfate decahydrate in our SaltMaker ChilledCrys, reducing TDS to 100,000 mg/L and enabling additional cycles with XtremeRO 1800.

Approaches for Low TDS

Low TDS waters (1,500–5,000 mg/L) can still often be saturated in calcium sulfate: SO4 ~1,800 mg/L. If sulfate and metals are your only treatment concern, then you may be able to avoid brine management costs. Sulfates can sometimes be targeted for removal, without needing to treat all of the dissolved mass contained within an entire flow, keeping costs low.To optimize your sulfate management costs, you should consider:

  • Avoiding the treatment of the entire flow—treating a portion and blending it is operationally less intensive and less costly, especially if the sulfate load varies seasonally.
  • Avoiding brine management—liquid brine can result in high post-processing expense, or large storage volumes and associated liabilities. Although if you have a pond to store brine, we can assist in minimizing the additional volume.


Photo of a full-scale, 2-module, Saltworks BrineRefine plant
Our BrineRefine system performs chemical treatment in a smart, automated way.
Photo of a ScaleSense real-time sensor analyzer for scaling ions
Our ScaleSense Real-Time Sensor

Our Sulfate Technology Options

Our offerings for sulfate solutions comprise one or more of the following industrialized product lines:

  • ScaleSense sulfate sensor: measure sulfates in real-time to enable precision blending, dosing, and performance-cost optimization on variable flows
  • Nanofiltration (NF): reject sulfates to a concentrated brine, while passing sodium, chloride, and in some cases silica, through to a permeate, which in some cases may then be released.
  • Reverse osmosis (RO): reject all TDS to a concentrated brine, generating freshwater permeate.
  • BrineRefine phys-chem precipitation: precipitate sulfates as a solid filter cake. The precipitation pathway changes project-by-project, so let’s get started on an assessment now.


Sulfate Solutions

The details of your project matter. For example, for seasonal sulfate challenges, chemical precipitation treatment may keep capital investment low, with the operating costs of chemicals being present only for a part of the year. On the other hand, if the challenge is year-round, and there is a low-cost disposal option for a sulfate-rich brine, sulfate-rejecting membrane solutions may make more sense.


We can help you to make informed choices with economic analysis provided for all of the possible options for your sulfate challenges.


Contact us to learn more about our solutions and options and how sulfates may be most economically treated using industrial water treatment technologies.

Photo of reverse osmosis vessels in a Saltworks XtremeRO plant

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A process flow diagram showing the cost-effective treatment and safe discharge of sulfates

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Photo of a ScaleSense real-time sensor/analyzer for scaling ions

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Photo comparison of FGD wastewater, one container is brown, murky and the second is clear and colorless water.

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Saltworks completed an off-site FlexEDR Selective pilot test to treat flue gas desulfurization (FGD) wastewater from a coal fired power plant in China. The objective was to reduce chlorides such that the FGD wastewater could be internally recycled and final treatment costs reduced notably.