This operations manual provides information for water treatment operators about waterborne viral, bacterial, and parasitic pathogens. It describes each type of pathogen, how it enters the water supply, its diseases, and its treatment. The manual provides operational procedures for monitoring, sampling, and testing; treatment and disinfection practices for all types of pathogens; and control techniques, including cross-connection control, dead-end flushing, and hydrant flushing. Includes waterborne disease statistics.