An On-Site Cooling Tower Treated by Stand-Alone Low-Concentration Dissolved Ozone

We report on an on-site 500 RT cooling tower ozone treatment process, in which chemicals other than ozone itself were completely eliminated. Ozone in an amount leading to less than 0.1 ppm of dissolved ozone was continuously introduced via side-stream injection into the circulating water returning from the chiller. The ozonated water was initially made to flow from the distributor to the filler in order to eliminate the growth of algae, and then to the chiller to reduce the corrosion and the fouling in the water. Positive ions such as Ca⁺² and Mg⁺² in the circulating water were precipitated by chelating them with carboxylic acids formed by the oxidation of organic compounds. We observed that using an ozone dosage of 0.1 ppm resulted in a colony-forming unit (CFU) less than 2 × 10³ /mL. With that well-controlled CFU, corrosion controlling and scale reducing were achieved as well.