Chemical treatment is a treatment to inject chemical in steam boiler. Injection chemical is performed to make hardness in drum or header soluble, so blowdown rate can be maintained. Another purpose of chemical treatment is prevention of crust formation and corrosion. Sulfuric acid or polyphosphate is the most commonly used to control the formation of calcium carbonate crust. The additions of material containing chromate, phosphate or other mixtures are also often used to control corrosion.
If water is left alone for a long time, microorganisms will grow such as bacteria, fungi, algae and protozoa. These microorganisms will continue to grow cause problems in the form of biological fouling which reduce heat transfer in feedwater and inhibit water flow rate. Microorganisms also make problem in cooling tower, so control of microorganism should be done on the cooling tower.
There are many chemical processing to control microorganism but a mixture containing copper are not recommended. Mixtures containing chlorine or bromine are effective blends for controlling microorganism but excessive use can damage the cooling tower of building materials. For the maintenance of free residual chlorine must be maintained at the highest limit of 1 ppm.