Chlorine dioxide is an oxidizing biocide capable of reacting with a wide range of organic substances including many of the constituents of bacterial cells.
The primary mechanism for the inactivation of bacteria with ClO2 is disruption of the protein synthesis pathway to the cell.
The low levels of chlorine dioxide used in drinking water inactivate bacteria due to oxidation, disrupting several different cell processes. In general, it has been shown that levels of chlorine dioxide at 0.5 ppm produce an effective disinfection.
While chlorine is inexpensive and commonly used in a variety of industrial settings, chlorine dioxide has been described to be more effective than chlorine against biofilms.
Chlorine dioxide has different reaction pathways involving natural organic matter than free chlorine, the formation of disinfection by-products (DBPs) like organ halogens is typically much lower in concentration than when using free chlorine, however, chlorite is a known by-product of chlorine dioxide generation, and it also influences bacterial levels since it has bacteriostatic properties.
As one of the promising disinfectants, chlorine dioxide has become widespread as it offers some unique advantages, including its easy operation and maintenance, requirement for a smaller dosage, less reaction time to yield, same disinfection effect as Cl2, and effectiveness over a wide pH range on killing bacteria or deactivating virus.
In addition to its biocidal efficiency, it was reported that chlorine dioxide has a biofilm-removing effect, which may be noticeable at a concentration of 0.5 ppm ClO2, and that it significantly reduces biofilm formation at a concentration of 100 ppm ClO2. It has been shown that chlorine dioxide is capable to control biofilm under a variety of conditions and remove biofilm in very difficult to treat cooling towers.