Biofouling can destroy cooling towers if they are made of lumber. Corrosion can occur on metal parts. More seriously, such contaminants can be harmful to humans coming in contact like operational and maintenance personnel. The most notable example has been the outbreaks of Legionnaires' disease, affecting people in hotels, hospitals, office buildings, and other locations, who have come into contact with cooled air from an air conditioning system contaminated from cooling tower water of the air conditioning plant. Algae are the typical Biological species found that could cause corrosion and Biofouling.

Algae can be branched or straight

Algae can be curled or in small free floating clusters with a slime coating