Water and Wastewater Terms Beginning R

A B C D E F G H I J K L M N O P Q R S T U V W Y Z

reduction (re-DUCK-shun)

A chemical reaction that results in the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic conditions (no dissolved oxygen present), sulfur compounds are reduced to odor-producing hydrogen sulfide (H₂S) and other compounds. In the treatment of metal finishing wastewaters, hexavalent chromium (Cr⁶⁺) is reduced to the trivalent form (Cr³⁺). The opposite of oxidation.