Bacteria, fungi, algae, and protozoa are the microorganismclasses of concern in cooling water systems. To control thegrowth of these organisms, programs employing oxidizingmicrobicides, nonoxidizing microbicides, andbiodispersants are often used. This technical committeereport discusses specific technologies used to control theseclasses of microorganisms. This report provides owners,engineers, contractors, and operators with specificinformation on the types of organisms found in coolingsystems, a list of common chemistries used for their control,and methods that are typically employed to monitorsystems. Its intent is not to serve as a guide to set up amicrobiological control program, but to assist users inunderstanding the components of in-place programs anddiscuss the treatment program typically used to avoidmisapplication. While this report includes a list of commontechnologies used to treat biofouling, it is not meant to beexhaustive.