Effective concentrate management from desalination applications

Concentrate from desalination plants contains high levels of salts, chemicals and contaminants, making it difficult to dispose of or reuse without further treatment. The key challenges include:

1. Environmental impact: Brine has a much higher salinity than seawater or feedwater, making disposal problematic. Releasing high-salinity brine into the environment, particularly in marine ecosystems, can alter local water chemistry, reduce oxygen levels and harm marine life. High salinity also limits the potential for reusing concentrate in agriculture, aquifer recharge or industrial processes without additional treatment, as most crops and industrial processes cannot tolerate such high salt levels.
2. Corrosive waste: The high salt content in brine accelerates the corrosion of pipelines, pumps and other infrastructure. This leads to more frequent repairs and replacements, driving up both capital and operational costs.

1. Toxicity of byproducts: Brine often carries residual chemicals from pretreatment processes, such as coagulants and antiscalants, as well as process byproducts such as heavy metals, making the brine more toxic than seawater.

1. Disposal costs: Conventional disposal methods, such as surface water discharge or deep-well injection, are becoming less feasible due to stricter environmental regulations. Alternatives such as deep-well injection or evaporation ponds are costly and can be limited by land availability or geological conditions. When suitable disposal sites are far away, transporting the concentrate adds logistical challenges and further increases costs. Finding cost-effective and sustainable disposal alternatives is now a top priority for industries.
2. Large volumes: Desalination processes, particularly reverse osmosis (RO), generate relatively large volumes of concentrate. Managing these volumes poses significant operational and logistical challenges.

Conventional solutions

Conventional solutions for managing concentrate in industrial water desalination involve several disposal techniques.

1. Surface water discharge: Disposing concentrate into water bodies such as bays, lakes or oceans is the most widely used method, especially for large seawater desalination plants. However, environmental concerns are leading to increased restrictions.
2. Sewer disposal: Some small desalination plants discharge concentrate into municipal wastewater systems. However, this approach is often limited by capacity and regulatory restrictions.
3. Deep-well injection: Common in medium to large desalination plants, this method injects concentrate into deep aquifers. However, it requires extensive permitting and geotechnical studies.
4. Evaporation ponds: Used in small to medium-sized plants, evaporation ponds are a feasible option in arid regions with high evaporation rates. However, they come with limitations due to land costs and environmental regulations.
5. Land application: In some cases, brine can be applied to land, such as for irrigation or percolation ponds. While this is a low-cost solution, its effectiveness depends heavily on the local climate and soil quality.
6. Blending with lower-salinity water: Blending the concentrate with lower-salinity water can dilute the brine before disposal.

As the need for better concentrate management and liquid waste reduction grows, new optimization processes and technologies are emerging.

1. RO recovery rate optimization: RO is the most widely used desalination technology, with recovery rates from 50% to 95%, depending on water chemistry and equipment. Maximizing recovery helps reduce liquid waste, but factors such as osmotic pressure, viscosity, chemical scaling, fouling and water quality requirements limit efficiency.

1. Selective membrane-based technologies (NF/ EDR): Improving water recovery by allowing non-essential constituents into the product water is a promising approach. Nanofiltration (NF) uses more permeable membranes than RO to target divalent salts, improving recovery. Electrodialysis reversal (EDR) employs an electric field to separate ions and achieve higher recovery rates, especially in scaling-prone waters.
2. Ultra-high-pressure RO (UHP-RO): UHP-RO membranes offer a high-efficiency solution for treating brine and achieving high water recovery, particularly in reduced liquid discharge (RLD) or zero liquid discharge (ZLD) applications. These membranes are rated for pressures of up to 1800 psig and can treat brines with total dissolved solids (TDS) concentrations as high as 130,000–150,000 mg/L. UHP‑RO is emerging as a potential alternative to thermal evaporators in some applications.
3. Optimized pretreatment unique separation process (OPUS): This membrane technology is specifically designed for high-fouling and scaling applications. By optimizing pretreatment before the RO membrane and operating at an elevated pH, OPUS effectively controls organic fouling and silica scaling.
4. Thermal-based technologies: These technologies, such as evaporators, are commonly used in ZLD systems and can manage TDS levels of up to 300,000 ppm. However, their efficiency drops and scaling increases beyond this point. Crystallizers, another key ZLD component, can manage TDS levels of up to 600,000 ppm or more but face challenges with corrosive salts and extreme pH levels.

As industries increasingly turn to desalination to address water scarcity, effective brine management becomes essential. From membrane-based solutions to thermal technologies such as ZLD, industries have many options to reduce their environmental impact. By adopting advanced brine management strategies, industries can meet regulatory requirements, support sustainability and lower costs.

At BBA, our experts are ready to guide you through the complexities of industrial water desalination and develop sustainable, tailored solutions. For more information about advanced brine management, reach out to us.

References

1. Voutchkov, N. (2014), State-of-the-Art of Concentrate Management for Desalination Plants, Techno Focus.
2. Greenlee, L. F., Lawler, D. F., Freeman, B. D., Marrot, B., and Moulin, P. (2009), Reverse osmosis desalination: Water sources, technology, and today's challenges, Water Research, 43(9), 2317-2348.
3. Pérez-González, A., Urtiaga, A.M., Ibáñez, R., and Ortiz, I. (2011), State of the art and review on the treatment technologies of water reverse osmosis concentrates, Water Research, 46, 267-283.
4. Cappelle, M., Davis, T., and Gilbert, E. (2014), Demonstration of Zero Discharge Desalination (ZDD). U.S. Department of the Interior Bureau of Reclamation.