Electrolytic water treatment for cooling towers
The Elgressy non-chemical treatment system for cooling towers combining electrolytic scale reduction and electro-chemical system for eradicating legionella is now available in the UK. Hundreds of these systems are installed around the world, and EWT Ltd has been set up in the UK to distribute them. The EST system for scale reduction can be incorporated into cooling towers in two ways. — in the make-up water circuit or in the main cooling-water circuit. Treating all the water is preferable as its hardness increases during the cooling cycle. Single units come in four sizes for flow rates from 5 to 20 m3/h. Greater flow rates can be accommodated by installing units side by side. The LPB disinfection system is connected in series with the EST to prevent precipitation of silicates and treat for legionella and other micro-organisms. The EST process works by producing OH- ions at the cathode that cause calcium-carbonate to peel off the walls of the tank. The cathodic reaction also causes metallic ions to precipitate and sink to the bottom. When required, a piston is actuated in the tank, which descends and scrapes the softened scale to the bottom. The outlet valve opens automatically, and the scale is evacuated. The process is not one of softening, but the precipitation and removal of calcium carbonate, thus preventing scale and corrosion. The LPB system is similar to the EST but contains a different anode made from metals that release inhibiting materials to the water. Even after having passed through the EST, some calcium carbonate and silica compounds remain in the water. The LPB system charges these salts, increasing their ability to dissolve in the water and prevent them settling. The combination of EST and LPB treats the water to prevent proliferation of legionella bacteria and other micro-organisms. Legionella cannot tolerate the high pH or survive a high concentration of magnesium hydroxide; both conditions exist in the EST/LPB system. In addition, the high current density raises the pH on the cathode surface to 13, destroying bacteria. Tel. 020 8806 0095
