The primary endusers of UPW include these industries: semiconductors, solar photovoltaics, pharmaceuticals, power generation (sub and super critical boilers), and specialty applications such as research laboratories. The "ultrapure water" term became more popular in the later 1970s and early 1980s as a way of describing the particular quality of water used in power, pharmaceutical, or semiconductor facilities. While each industry uses what it calls "ultrapure water", the quality standards vary, meaning that the UPW used by a pharmaceutical plant is different than that used in a semiconductor fab or a power station. The standards tie into the UPW use. For instance, semiconductor plants use UPW as a cleaning agent, so it is important that the water not contain dissolved contaminants that can precipitate or particles that may lodge on circuits and cause microchip failures. The power industry uses UPW as a source to make steam to drive steam turbines; pharmaceutical facilities will use UPW as a cleaning agent, as well as an ingredient in products, so they seek water free of endotoxins, microbials, and viruses. Today, ion exchange (IX) and electrodeionization (EDI) are the primary deionization technologies associated with UPW production, in most cases following reverse osmosis (RO). Depending on the required water quality, UPW treatment plants often also feature degasification, microfiltration, ultrafiltration, ultraviolet irradiation, and measurement instruments (e.g., total organic carbon [TOC], resistivity/conductivity, particles, pH, and specialty measurements for specific ions). Early on, softened water produced by technologies like zeolite softening or cold lime softening was a precursor to modern UPW treatment. From there, the term "deionized" water was the next advancement as synthetic IX resins were invented in 1935 and then became commercialized in the 1940s. The earliest "deionized" water systems relied on IX treatment to produce "high-purity" as determined by resistivity or conductivity measurements. After commercial RO membranes emerged in the 1960s, then RO use with IX treatment eventually became common. EDI was commercialized in the 1980s and this technology has now become commonly associated with UPW treatment. Ultrapure water is used extensively in the semiconductor industry; this industry requires the highest grade of UPW quality. The consumption of electronic-grade or molecular-grade water by the semiconductor industry can be compared to the water consumption of a small city; a single factory can utilize ultrapure water (UPW) at a rate of 2 MGD, or ~5500 m3/day.