The municipalities and private companies that treat water must handle this resource with the utmost care – all while balancing the need to operate as efficiency as possible while complying with regulatory requirements. Municipal water treatment processes include the following steps:
Intake Screening: Initial screens keep large debris (logs and tree limbs) from entering the treatment process. Secondary screens remove smaller items like fish/marine life and vegetation.
Taste, Odor Control & Disinfection: The quality of incoming water into treatment facilities varies by storms or man-made interaction, so seasonal (or continuous) taste & odor issues are treated via metering pumps dosing potassium or sodium permanganate downstream from the intake pumps. Sodium hypochlorite is often injected to control aquatic growth, to reduce odor and to eliminate micro-organisms that could cause illness if consumed.
pH Adjustment: Drinking water should have a neutral (7) pH. Specific volumes of acids are administered to alkaline feed-water (pH higher than 7) to lower pH, while similar volumes of caustics are dosed to acidic feed-water (pH lower than 7) to raise its alkalinity. pH adjustment is a constant balance: Injecting too much hydrochloric acid to lower pH will require additional doses of soda ash (sodium carbonate) later in the process.
Coagulant Feed: Millions (or billions) of miniscule particles that are too small to be filtered (finer than 1 micrometer), remain in motion due to negative electrostatic charges that cause them to repel one another. Positively charged coagulant chemicals (like alum, ferric chloride, ferric sulfate, or polyaluminum chloride) are used to bring tiny colloidal particles together to form flocs, or heavier aggregates, that become easier to filter.
Flocculation & Clarification: Neutralized particles coming together form flocs that settle as sludge on the bottom of the clarifier.
Filtration & Well Storage: Water must be filtered to remove remaining particles, and filtered water is retained in clear wells long enough to allow sufficient contact time for disinfectants and also to provide back wash water for filters.
Fluoridation: About two-thirds of municipal treatment plants add fluoride as part of their process. Municipalities dose this chemical at an average concentration of about 1 part per million (1 ppm) or 1 milligram per liter.
Post Chlorination: Sodium hypochlorite is often injected towards the end of the treatment process to prevent equipment corrosion.
Distribution: By leveraging metering pumps at numerous stages of the process, drinking water is treated in a consistent and reliable manner, making it available for distribution to every home and business in the community.