In the MIT-Zuid feasibility study, the application of the ion selective desalination technique for cooling water softening has been investigated. To soften the cooling tower water, ion exchange membranes are used with a specific preference for rapid removal of the multivalent ions such as Calcium and Magnesium. An example of tap water softening has been added. After 1 passage along the membranes over a period of 4 seconds, the Calcium and Magnesium is reduced by 90%. Chloride and hydrogen carbonate are also removed. The yield of the soft water produced is 98%. Only 2% water is lost in the concentrated wastewater with mainly Calcium, Magnesium, Chloride and HydrogenCarbonate. This creates a strong competitive advantage with the current 2 softening techniques.
- Ion exchange resins completely remove Calcium and Magnesium, making the water corrosive. Corrosion inhibitors must be added to the cooling water. The resins must be regenerated very regularly with a large excess of table salt (25 tons of sodium chloride per year).
- Another common technique is to add anti-scalent polymers to the cooling water. These water-soluble polymers complex Calcium and Magnesium, making the water softer. The degree of thickening of the cooling water is thus limited, so that the cooling water must be flushed earlier.
The unique properties of the applied innovation may be disruptive to current softening techniques for cooling water treatment. In the described process no chemicals are used, only electricity, more water savings, and more importantly, at a lower cost.