There are many sulfate treatments available, with different advantages and disadvantages. Factors for consideration include capital and operational costs, solid vs. liquid brine reject for disposal, if the need is seasonal or year-round, and suitability for adverse operating conditions.
Flexible sulfate removal for high & low TDS waters
If you need to meet a sulfate discharge limit, we very likely have a solution for you. Every sulfate situation is different, so your sulfate challenge first deserves a dedicated review from our experts, to see how sulfates may be most economically treated using industrialized water treatment technologies.
Once a review is complete, most of our clients’ sulfate removal needs can be classified into high- and low- total dissolved solids (TDS) waters, described below. We have solutions for both, adjusted to your unique wastewater, including our new SulfateSelect solution family for low TDS wastewaters.
Solutions for High TDS
High TDS sulfate-laden waters (TDS~80,000–200,000 mg/L) often contain predominantly sodium sulfate: SO42- ~60,000–120,000 mg/L. To treat them, you can take advantage of two unique properties of sodium sulfate:
- Low osmotic pressure: concentrate sodium sulfate solutions to over 200,000 mg/L with our XtremeRO 1800 ultra-high pressure RO systems
- 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) are often saturated in calcium sulfate: SO4 ~1,800 mg/L. To optimize your costs, you should:
- Avoid treating the entire flow —treating a portion and blending is operationally less intensive and less costly, especially if the sulfate load varies seasonally.
- Avoid 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 help you to minimize its volume.
If sulfate and metals are your only treatment concern, then you may be able to avoid brine management costs with our SulfateSelect (patent pending) process.
SulfateSelect is our flexible solution family for sulfates, customizable for treating your water. It combines the two most accepted sulfate treatment technologies—membranes and precipitation—in one comprehensive package with integrated operation and control. It adds value by:
- Significantly limiting chemical costs, in some cases to only 10% of conventional approaches
- Employing reverse osmosis and nanofiltration while purging sulfates from the NF or RO brine, enabling blending and achieving zero liquid discharge (ZLD) without the hassle of a thermal evaporative crystallizer.
The result is a cost-effective process that does not generate a liquid brine by-product. After all, the best way to achieve ZLD is to avoid it all together.
SulfateSelect is comprised of 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 today.
SulfateSelect Related Resources
Real-time measurement provides prompt feedback for controls. A real-time sensor can help to optimize your process, reduce risk, and minimize operational and maintenance demand. Saltworks has developed a new real-time sensor—that is simple and robust—to operate in the high-TDS range.
With the growing importance of brine management, modernized chemical softening systems can enable economic ultra-high recovery reverse osmosis, minimizing RO brine volume, disposal costs, and reliability risks.