Highly purified water (HPW), high purity water or ultrapure water is necessary for various applications including dialysis, pharmaceutical and electronics rinse water. Highly purified water is a commonly used term to emphasize the fact that the water is treated to the highest levels of purity, including the removal of: organic and inorganic compounds; dissolved and particulate matter; volatile and nonvolatile, reactive and inert; hydrophilic and hydrophobic; and dissolved gases.
While each industry uses what it calls “highly purified water”, the quality standards vary, meaning that the highly purified water used by a pharmaceutical plant is different than that used in an electronics plant, semiconductor fabrication plant or a power station. For example, pharmaceutical facilities will use highly purified water as a cleaning agent as well as an ingredient in products, so they require water free of endotoxins, microbials and viruses. Electronics and semiconductor plants use highly purified water as a cleaning agent, so it is important that the water not contain dissolved contaminants that may precipitate or particles that may become lodged on the circuits and cause microchip failures. The power industry, on the other hand, uses highly purified water as a source to make steam to drive steam turbines.
A number of organizations and groups develop and publish standards associated with the production of highly purified water. Pharmaceutical plants follow water quality standards as developed by pharmacopeias, including the United States Pharmacopeia (USP), European Pharmacopeia (EP), British Pharmacopeia and Japanese Pharmacopeia. The most widely used requirements for highly purified water quality for electronics and semiconductor fabrication are documented by the American Society for Testing and Materials International (ASTM International) and Semiconductor Equipment and Materials International (SEMI).