Scale
When makeup water contains high concentrations of inorganic salts, mineral scale
can form insulating deposits on heat exchange equipment. When deposition of these
salts is heavy, heat transfer and water flow may be severely restricted. The resulting
rise in condensing temperature will cause a reduction in refrigeration capacity and an
increase in energy consumption.

corrosion
Often the chemicals used to control bacteria, scaling and biofilm, contribute to
chemically induced corrosion.

Micro-Biological Growth Fouling

Normal conditions for all cooling water systems act as an ideal environment for microbiological growth.

Typically Bacteria (Aerobic & An-Aerobic) , Fungi & Algae are expected to grow in Open Cooling Tower Systems. And different types (Anaerobic) of Bacteria may grow in Closed Cooling Water Systems. Therefore, water left un-attended for even short periods of time may enhance the growth of microbiological growth which may lay down bio-films.
Biofilm
The cooling water system creates a number of ecological niches for colonization by
microorganisms. Biological deposits on metal surfaces are powerful heat insulators.
Bio-films have 6 times more insulating capacity than scale and can also contribute to
corrosion.