How to Improve FGD Economics with Chloride Removal using Selective EDR

Learn how to keep up with tightening FGD wastewater regulations using the latest innovations in water treatment. 

Key Takeaways:

• As regulations on FGD wastewater tighten, additional treatment is required. Often, this is chemically intense, and high cost. The best means to lower treatment costs is to reduce the volume of wastewater generated, usually by increasing internal recycle.
• Internal recycle of FGD wastewater is limited by high chloride concentrations that inhibit sulfur dioxide absorption and can cause corrosion issues as chlorides are cycled up – this can be solved by the solution below:
• Chlorides can be selectively removed from FGD wastewater by industrially available electrodialysis reversal (EDR) with monovalent selective membranes (mEDR). mEDR selectively transports chlorides under an electric field through monovalent anion exchange membranes while blocking sulfates. This reduces the chloride load to enable internal FGD recycle while producing a non-scaling brine of sodium/calcium chloride at greater than 90% recovery (or 10% brine waste volume).
• 100% recycle of the low chloride treated water will not be possible due to cycling up of organics not removed by mEDR, however even partial recycle will reduce the cost of expensive FGD wastewater treatment infrastructure.
• Highly robust monovalent ion exchange membranes with >98% selectivity should be used, such as Saltworks’ Ionflux, which prevent scaling by blocking almost all sulfates and can be cleaned with strong oxidants such as bleach.
• mEDR can be integrated into existing FGD wastewater treatment trains, and eliminates the need for costly soda ash softening while producing a brine concentration almost equivalent to evaporators.
• Although chlorides can be removed to less than 200 mg/L, reducing them to between 1,200 and 1,500 mg/L is more economical. Lower chloride levels can be attained at the expense of higher capital and higher energy due to reduced membrane flux below 1,200 – 1,500 mg/L Cl.

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Taxonomy

• Treatment
• Treatment Methods
• Desalination
• Electrodialysis
• Process Engineering
• water treatment
• Desalination