Slime-encapsulating bacterial growths can become very adhesive, especially under heat transfer conditions. Suspended matter flowing in the water phase (corrosion products, hardness salts, mud, sand, silt, clay, etc.) becomes entrapped on the slime web. This problem of "biofilm fouling" is often not readily evident; quantitative analysis of a deposit sample may show microbial organic matter to be a comparatively minor portion of a deposit, in terms of weight. The real significance is realized only when voluminous masses are taken into account. This may be accomplished visually. It would be impossible to determine the real problem without examining the deposit or the source from which it was removed. Although a deposit may contain only 20 percent microbial matter by weight, 90 percent of the volume of the deposition may be microbial. This will, of course, affect heat transfer.

Iron bacteria produce ferric hydroxide deposits many times the size of the bacteria themselves. Uninhibited diatomic algal growth can result in silica fouling of industrial water systems. Filiform organisms accumulate oil and dissolved hydrocarbons and emit noxious, corrosive gases as wastes. Petrochemical and refining plants must be particularly wary of these organisms.

Microbiological matter may lead to physical problems in the system, culminating in loss of efficiency, heat transfer and production. The accumulation of biomatter in internal sections of industrial towers can seriously reduce tower efficiency. Industrial by evaporation depends upon maximum exposure of the industrial water to air. 

Any contamination of the fill or splash-plate areas of the tower will increase water droplet size, and thereby reduce the effective surface area. If a tower cannot achieve the temperature drop for which it was designed, reduced heat transfer will almost certainly have ramifications at other stages.