We call this solution CleanOxide 75. It is a 0.75% (7,500 mg/L) solution of pure chlorine dioxide in water when freshly made. Chlorine dioxide is unstable in water no matter how it is generated and once produced CleanOxide has a limited shelf-life. In practical terms, provided the solution is stored out of direct sunlight, it will remain effective for 30 to 45 days after which time it should be discarded.
To overcome this limitation, CleanOxide is supplied as a two-component system – CleanOxide Part A and CleanOxide Part B. These two liquids are simply mixed in a black plastic container left to stand for eight hours, agitated briefly and the solution of CleanOxide 75 is ready to use. CleanOxide Part A and CleanOxide Part B have a shelf life in excess of three years when handled and stored in the original unopened containers.
For professional users such as water treatment facilities, a more concentrated form of Part A designated as Part A (P) is available. This must first be mixed with water and then Part B added to form CleanOxide 75. CleanOxide 75 contains no free chlorine, no chlorates and negligible chlorite when diluted at the recommended rates. The only impurities are small amounts of sodium sulphate and sodium chloride formed as by-products when Part A and Part B are mixed. Sodium chlorite content is less than 75 mg/L in the concentrated product.
Sodium hypochlorite (also known as liquid chlorine) is an aqueous solution of sodium hypochlorite supplied commercially at various concentrations up to a maximum of about 15% available chlorine. Sodium hypochlorite also has a limited shelf- life and the concentration of available chlorine begins to drop as soon as it is produced. Since sodium hypochlorite cannot be made as required but must be shipped from the supplier, the available chlorine when delivered is typically considerably lower than when manufactured.
The table below highlights the many advantages of CleanOxide 75 over sodium hypochlorite for disinfection of water:
|CleanOxide 75||Sodium Hypochlorite|
|CleanOxide75 is a pure (99%) solution of chlorine dioxide in water(7500mg/L).||Sodium hypochlorite used for water disinfection contains10 to 15% (typically 12.5%) available chlorine.|
|CleanOxide75is dosed using Teflon-based standard dosing pumps. Residual levels are measured using membrane sensors or photometer.||Sodium hypochlorite is dosed using standard dosing pumps. Residual levels are measured using membrane sensors or photometers.|
|CleanOxide 75 is effective between pH 4 and 10; therefore pH adjustment is not normally required when using CleanOxide 75.||Efficacy of sodium hypochlorite is strongly pH dependent. Optimum disinfection is between pH 7 to 7.5. Water pH must be balanced for product to work efficiently.|
|CleanOxide 75 is highly selective against microorganisms and has residual activity for up to 72 hours.||Sodium hypochlorite is not selective and reacts with organic matter present in the water rapidly depleting the active constituent.|
|CleanOxide 75 can be produced on site, as and when required ensuring fresh product is always available.||Sodium hypochlorite can only be produced off-site. Degradation begins immediately and is influenced by temperature, storage conditions and storage time.|
|There are no chlorates present in CleanOxide 75.||Degradation of sodium hypochlorite begins as soon as it is produced. High storage temperatures increase chlorate levels. which can rapidly reach concentrations that make it unacceptable for use in drinking water.|
|CleanOxide 75 does not react with organic matter to form hazardous by-products.||Sodium hypochlorite reacts with organic matter naturally present in water to form chlorinated organic compounds including chloroform, trichloroacetic acid and Mutagen X – compounds linked to cancer.|
|CleanOxide 75 does not react with ammonia and amines.||Sodium hypochlorite reacts with ammonia and amines naturally present in water to form chloramines – compounds that give chlorinated water its distinctive chlorine taste and odour.|
|CleanOxide 75 is very effective at removing undesirable taste and odour caused by algae and phenols.||Sodium hypochlorite does not remove taste and odour problems caused by algae and phenols.|
|CleanOxide 75 does not react with organic matter present in water and cannot form chloroform or chloramines. CleanOxide 75 destroys chloroform and chloramines, if present.||Sodium hypochlorite contributes to taste and odour problems by reacting with organic matter to form chloroform and chloramines – compounds that give chlorinated water its typical chlorine taste and odour.|
|CleanOxide 75 is highly effective at removing biofilm and preventing the growth of biofilm in storage tanks and distribution pipes. If necessary, biofilm can be removed by shock dosing at 30mg/L for 8 hours without risk of damage to tanks or pipes because the product is not corrosive when dosed into water. Continuous dosing at 0.05 to 0.2 mg/L prevents re-growth of biofilm.||Sodium hypochlorite at normal dose levels does not control or remove biofilm in storage tanks or distribution systems. Shock dose can damage the material of the tanks/pipes because of its corrosive nature and still not control or remove biofilm.|
|There are no known examples of microorganisms becoming resistant to chlorine dioxide. The mode of action of chlorine dioxide is such that it is generally thought that microorganisms cannot develop resistance to this compound.||Some microorganisms including Cryptosporidium, Listeria and Legionella are known to develop resistance to sodium hypochlorite.|