Glossary of Terms - Q
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quartz jacket - A clear, pure fused quartz tube used to protect the high intensity ultraviolet lamps in ultraviolet systems. It usually retards less than 10 percent of the ultraviolet radiation dose.
quartz sleeve - See quartz jacket.
quaternary ammonium - An organic chemical group of cationic surface active compounds that tend to take up and hold on to surfaces of other substances; the group consists of ammonium (NH4+) compounds in which one or more of the hydrogen atoms attached to the nitrogen are substituted by organic radicals. Quaternary ammonium compounds are strong bases, and their salts (formed by reaction with acids) provide the exchange sites on certain anion exchange resins.
Quaternary ammonium salts in which the "active" ingredient is sufficiently high in activity and concentration can be used in water treatment as micro-biocides (microbe killers) and surfactants. Cationic quaternary ammonium compounds adsorb the cell membranes of the microbes and react chemically with the negative charges carried by the cell walls to inactivate and kill the microorganism.