Cooling towers can be a critical process in many industrial production facilities, and an industrial cooling tower can be the perfect media for biological growth if not properly treated. Typical pH is 7-9 and temperatures may have a wide range.

Dissolved gases, improper pH control or formation of differential aeration cells under deposits cause corrosion to be undoubtedly the single most significant factor leading to the premature deterioration of HVAC equipment and piping. In its most insidious form, pitting, is only revealed when the equipment fails. Failures of this type can be catastrophic, leading to costly downtime for repairs and equipment replacement, personal discomfort and even total plant shutdown.

In a cooling tower, the water trickles down a large surface area in order to air-cool the water. The natural evaporation provides the cooling necessary to reuse the water. As water evaporates, minerals and contaminants in the water concentrate. These minerals and contaminants will eventually reach a concentration where they will cause problems and interfere with the performance of both the tower and the cooling system, itself. Fouling and corrosion of the cooling tower can impact treatment, and impact heat transfer losses causing decrease in efficiency and increased power consumption. Biofouling can also destroy cooling towers if they are made of lumber. Corrosion can occur on metal parts.

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.

BIOLOGICAL GROWTHS

Apart from their well known role in promoting corrosion, through the formation of acid metabolic products or through the mechanism of concentration cells associated with deposits of all kinds, the uncontrolled multiplication of bacteria, algae and fungi, results in bio-film formation on heat exchange surfaces and has now been recognized as an important contributor to impaired heat transfer efficiency in cooling water systems.

In fact, it has been unequivocally demonstrated that because of the unique surface characteristics of bio-films, their hydrodynamic and insulating properties far exceed those of an equivalent thickness of scale or corrosion deposits.

Of particular concern are the slime and spore formers which are difficult to control because of the protection afforded by the polysaccharide sheaths that they secrete and the organisms that metabolize either cellulose or lignin, resulting in structural weakness and eventual collapse of wooden tanks or towers.