When chlorine dioxide is fed as a disinfectant or oxidizing agent it reacts with natural organic matter (NOM) and forms a disinfection byproduct called Chlorite. Chlorite is a harmful substance and is regulated by the EPA to 1.0 mg/L or 1 part per million (ppm). Feeding Ferrous Sulfate (Fe2+) will reduce chlorite to chloride in reaction times as short at 5-15 seconds.
In addition to the reduction of chlorite, the formation of ferric hydroxide aids in the coagulation process and has proven to reduce the primary coagulant dose rate.
The reaction with chlorite is fast and 1 ppm of chlorite is consumed by 3.1 ppm of ferrous as Fe from Ferrous Sulfate.