Cooling towers are used to cool down hot condenser water taken from chillers of air conditioning systems. The cooling effect of cooling towers are attributed to evaporation of water when it is blown through by air from fans.
After some time of circulating through cooling towers, water becomes more and more concentrated with dissolved salts in water. The concentrated water has to be drained off and fresh new water added into system to make it less saline.
However, when fresh water is added, it will not have any passivation chemicals to protect piping and component condenser parts from corrosion. So chemicals are added to protect piping and machinery.
For cooling tower water, chemical used serve 2 basic functions - a corrosion inhibitor and a biocide.
The corrosion inhibitor is for preventing corrosion in piping and related parts. The biocide is to prevent growth of algae, bacteria and other micro organisms.
Every water treatment chemical company has its own formula and special concortions. A typical corrosion inhibitor may contain about 1 - 10% Potassium Hydroxide or similar alkali. This is then further diluted when mixed with water in cooling tower. Being an alkali, it will neutralize any acids found in water that can cause corrosion to occur.
The cooling tower is installed outdoors. With ample warmth from chiller, fresh air and sunlight, water it contains is a very ideal medium for growth of micro organism.