Disinfection

Disinfection is accomplished by eliminating pathogenic organisms through filtration, chemical addition, UV radiation or ozonation. In many cases a combination of processes are used together. Possible pathogens include viruses, bacteria, including Escherichia coli, Campylobacter and Shigella, and protozoa, including Giardia lamblia and other cryptosporidia. Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage - often called a contact tank or clear well to allow the disinfecting action to complete. In most developed countries, public water supplies are also required to maintain a residual disinfection agent throughout the distribution system, where water may remain for days before reaching the consumer.