Oxidation Reduction Potential (ORP or Redox Potential) measures an aqueous system’s capacity to either release or accept electrons from chemical reactions. When a system tends to accept electrons, it is an oxidizing system. When it tends to release electrons, it is a reducing system. A system’s reduction potential may change upon introduction of a new species or when the concentration of an existing species changes.

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  ORP values are used much like pH values to determine water quality. Just as pH values indicate a system’s relative state for receiving or donating hydrogen ions, ORP values characterize a system’s relative state for gaining or losing electrons. ORP values are affected by all oxidizing and reducing agents, not just acids and bases that influence pH measurement.

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  From a water treatment perspective, ORP measurements are used often to control disinfection with chlorine or chlorine dioxide in cooling towers, swimming pools, potable water supplies, and other water analysis applications. For example, studies have shown that the life span of bacteria in water is strongly dependent on the ORP value. In wastewater, ORP measurement is used frequently to control treatment processes that employ biological treatment solutions for removing contaminants.