Chlorine dioxide, a water-soluble gas, is an extremely effective and powerful biocide that has been used for many years exhibiting rapid kill over a wide range of organisms. It does not form chlorinated compounds in the presence of organics and is efficacious over a wide pH range. Unlike chlorine, chlorine dioxide does not “chlorinate.” It works through oxidation – penetrating bacteria cell walls and reacting with vital amino acids in the cytoplasm of the cell to inactivate the bacteria that produces the biofilm. It is also effective against Giardia Lambia and Cryptosporidium oocysts, which cause diseases such as cryptosporidiosis in public drinking water supplies. Chlorine dioxide does not react with organics leaving more available chemistry as a biocidal agent. This selectivity and its effectiveness start at much lower concentrations relative to chlorine, and its rate and mechanism of action minimizes the risk for general corrosion. Additionally, studies demonstrate the dramatic difference of chlorine dioxide vs. chlorine when each is added to a heavily polluted water source. While chlorine is readily consumed by the polluted water, chlorine dioxide is very selective.