As water evaporates from a cooling tower, dissolved minerals remain in the circulating water, increasing the concentration of total dissolved solids (TDS). Efficient, reliable operation requires coordinated control of water chemistry and microbiological conditions.
Scaling and Mineral Deposits
Salts such as calcium carbonate (CaCO₃) and calcium sulfate (CaSO₄) can precipitate on surfaces when their solubility limits are exceeded. Deposits on heat exchanger surfaces increase thermal resistance and reduce the overall heat transfer coefficient. Accumulation on fill and within water distribution systems can also impair cooling performance.
Corrosion and Metal Protection
Dissolved oxygen, chloride ions, unsuitable pH and high conductivity can accelerate corrosion, depending on materials and operating conditions. Chlorides can particularly increase the risk of pitting corrosion. Control measures include appropriate material selection, water chemistry monitoring and corrosion inhibitors where required.
Biofilm and Legionella Risk
Biofilm is a layer formed by microorganisms attached to surfaces and can support the persistence of bacteria such as Legionella. Temperatures of 25–45 °C are particularly favorable for Legionella growth. Inhaling fine water droplets containing the bacteria can cause Legionnaires’ disease.
Water Treatment and Monitoring
An effective program combines controlled blowdown, pH and conductivity monitoring, deposit removal, reduced stagnation and appropriate disinfection. Oxidizing or non-oxidizing biocides, their dosage and contact time should be selected according to water analyses, product labels and the site-specific water management plan. Regular measurements and records should be used to assess program effectiveness.