The time during which newly installed or cleaned heat transfer surfaces remain free of fouling deposits thick enough to diminish heat transfer coefficients or energy efficiency is often called the “induction period,” a term disguising lack of knowledge of the microfouling events actually occurring. Using novel flow cells to conduct water of fresh, brackish, and oceanic quality, natural and treated with antifouling chemicals, over test surfaces of different clean and coated metals, it has been observed that the initial pattern of fouling deposits is remarkably similar in all circumstances. Rapid adsorption of protein-dominated films is followed by attachment of rodlike bacteria, bacterial exudation, colonization by a second wave of prosthecate microorganisms, additional secretion, and growth of debris-trapping filamentous appendages. Although inappropriate to extrapolate the noted rates of these processes to in-plant heat exchangers at present, this sequence of microfouling events seems universal enough to characterize the induction period of all water-side biofouling phenomena.

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