How Effective is Chlorine Dioxide (ClO2)?

The interest in the use of chlorine dioxide as an alternative for or addition to chlorine for the disinfection of water has increased in the last decade. Chlorine dioxide is a very effective bacterial disinfectant and it is even more effective than chlorine for the disinfection of water that contains viruses. Chlorine dioxide has regained attention because it is effectively deactivates the chlorine-resistant pathogens Giardia and Cryptosporidium. Chlorine dioxide removes and prevents biofilm. 

Disinfection with chlorine dioxide does not cause odor nuisance. It destroys phenols, which can cause odor and taste problems. Chlorine dioxide is more effective for the removal of iron and manganese than chlorine, especially when these are found in complex substances.
The use of chlorine dioxide reduces the health risk of microbial pollutions in water and at the same time decreases the risk of chemical pollutions and by-products. Chlorine dioxide is a more effective disinfectant than chlorine, causing the required concentration to kill microorganisms to be much lower. The required contact time is also very low.

1. Bactericidal efficiency (unaffected by pH values). Contrary to chlorine, chlorine dioxide is effective at a pH of between 5 and 10. The efficiency increases at high pH values, while the active forms of chlorine are greatly influenced by pH. Under normal circumstances chlorine dioxide does not hydrolyze. This is why the oxidation potential is high and the disinfection capacity is not influenced by pH. Both temperature and alkalinity of the water do not influence the efficiency. At the concentrations required for disinfection, chlorine dioxide is not corrosive. Chlorine dioxide is more water-soluble than chlorine. In the last few years better and safer methods for chlorine dioxide production have been developed.
2. Superior in the destruction of spores, bacteria’s viruses & pathogen organisms.
3. Required lower contact time.
4. Does not react with NH3 or NH4+
5. Destroys THM precursors and increases coagulation. Chlorine dioxide can be used to reduce the amount of trihalomethanes (THM) and halogenated acidic acids, formed by the reaction of chlorine with organic matter in water. Before the water is chlorinated, chlorine dioxide is added. The amount of ammonium in the water decreases. The chlorine that is added afterwards, oxidizes chlorite into chlorine dioxide or chlorate. Ozone can also be used to oxidize chlorite ions into chlorate ions. By the use of chloramines, nitrification can take place in the distribution network. To regulate this, chlorine dioxide is added. By products control by chlorine dioxide can take place in combination with adequate disinfection, especially the reduction of bromine containing trihalomethanes (THM) and halogenated acidic acids that originate from the reaction of bromine containing water with natural organic matter. Chlorine dioxide itself combined with bromine does not form hypobromous acid or bromate, while chlorine and ozone do. Chlorine dioxide has excellent anti-microbiological qualities without the non-specific oxidation of ozone.
6. Destroys phenols and has no distinct smell.
7. Better at removing iron and magnesium compounds.
8. Prevents, Removes and Destroy Biofilm. Chlorine dioxide remains gaseous in solution. The chlorine dioxide molecule is powerful and has the ability to go through the entire system. Chlorine dioxide can penetrate the slime layers of bacteria, because chlorine dioxide easily dissolves, even in hydrocarbons and emulsions. Chlorine dioxide oxidizes the polysaccharide matrix that keeps the biofilm together. During this reaction chlorine dioxide is reduced to chlorite ions. These are divided up into pieces of bio film that remain steady. When the bio film starts to grow again, an acid environment is formed and the chlorite ions are transformed into chlorine dioxide. This chlorine dioxide removes the remaining bio film. A biofilm is a layer of microorganisms contained in a matrix (slime layer), which forms on surfaces in contact with water. Incorporation of pathogens in biofilms can protect the pathogens from concentrations of biocides that would otherwise kill or inhibit those organisms freely suspended in water. Biofilms provide a safe haven for organisms like Listeria, E. coli and legionella where they can reproduce to levels where contamination of products passing through that water becomes inevitable. It has been proven beyond doubt that chlorine dioxide removes biofilm from water systems and prevents it from forming when dosed at a continuous low level. Hypochlorite on the other hand has been proven to have little effect on biofilms.
9. Corrosive effects are minimal when compared to the corrosive effects of tap water. No corrosion associated with high chlorine concentrations. Reduces long term maintenance costs.
10. Environmental friendly.