Health Effects of Chlorite, Chlorate and Chlorine Dioxide:

Exposure to chlorine dioxide and chlorite in excess of EPA1,EPA2-regulated maximum levels can have effects on the nervous system in infants, small children, and unborn fetuses. Chlorite and chlorate have been shown to effect red blood cells in animal studies, but similar results did not appear in the highest doses tested on humans (36 micrograms per kilogram of body weight).

According to the EPA, long term exposure to large amounts may lead to anemia. There is currently no evidence of human carcinogenicity.

Water Treatment for Chlorite, Chlorate and Chlorine Dioxide According to the Canadian Committee on Drinking Water, "some residential-scale treatment devices using a granular activated carbon filter may remove chlorite," although they have not yet certified any filters for that use. There is no recommended treatment for chlorate.

Chlorine Dioxide:

Water disinfection with chlorine dioxide is a very efficient and gentle way of fighting legionella bacteria and all kinds of micro-organisms in water such as viruses, parasites and fungus spores.

Chlorine dioxide kills micro-organisms in the water by an irreversible oxidative destruction of the transport proteins in the living cells. Chlorine dioxide has a much more powerful disinfecting action against all kinds of germs and contaminants such as viruses, bacteria, fungi and algae than most other biocides. The oxidation potential is higher than with chlorine and fewer chemicals are required. Further more, germs that are resistant to biocides can be killed completely with chlorine dioxide.

Chlorine dioxide is generated from sodium chlorite and hydrochloric acid. When the two components are mixed, the oxidising disinfectant chlorine dioxide is formed in a chemical reaction along with the harmless by-products salt and water.

Advantages:

(i) Removes biofilm effectively.

(ii) Effective against bacteria in biofilm and free bacteria floating in the water.

(iii) Effective to bacteria and biofilm in dead-legs without water flow.

(iv) Very long residual effect in the system. The ClO2 stay in the water for days.

(v) Does not affect smell and taste of the water.

(vi) Not sensitive to pH-value of the water.

(vii) Low life cycle cost.

Chlorine dioxide is an effective and popular water treatment solution. Dissolved into water, it creates a powerful, yet selective oxidant, biocide, and disinfectant used for both treating drinking water and commercial treatment applications.

To understand the potential, we asked our experts to answer the 12 most frequently asked questions they get on the topic of chlorine dioxide:

1. Why is chlorine dioxide used in water treatment?

Chlorine dioxide (ClO2) is used in water treatment because it is an effective oxidant, biocide, and disinfectant at relatively low concentrations. It also has minimal reactivity with organic matter and minimal by products are formed during the treatment process.

Chlorine dioxide can kill bacteria, viruses, and other microbes in water that will help prevent the spread of waterborne diseases without hydrolyzing. Chlorine dioxide will stay as a dissolved gas in a solution, is around ten times more soluble than chlorine, and can be removed by aeration. This potency, combined with safety, makes it an appealing option for water treatment use.

2. When is chlorine dioxide the preferred choice for disinfection?

ClO2 is a disinfectant, best utilized in systems with surface germs and biofilms. Chlorine dioxide removes biofilms and inactivates germs by destroying cell walls. Furthermore, the oxidation and disinfection capabilities of ClO2 are independent of the pH of the water across a wide range. ClO2 can be used effectively in water with a pH 6 to 9.

3. Is chlorine dioxide safe for water treatment?

Chlorine dioxide is a safe form of water treatment. It is used in various applications, including the treatment of drinking water for human consumption.

The Environmental Protection Agency (EPA) set the maximum allowed concentration of chlorine dioxide in drinking water at no more than 0.8 parts per million (ppm). The Occupational Safety and Health Administration (OSHA), an agency of the United States Department of Labor, has an 8-hour exposure limit of 0.1 ppm in air (0.3 mg/m3) for people in contact with chlorine dioxide.

The EU DWGL 98/83 sets the limit for chlorine dioxide application as low as 0.2 ppm. Due to this low addition ratio, the DBP levels are 0.2 ppm for chlorite and 0.25 ppm for chlorate being on a very lower level.

4. What is the difference between ClO2 and chlorine?

Chlorine dioxide (ClO2) is a compound, composed of a chlorine atom and two oxygen atoms. Chlorine and chlorine dioxide are both oxidizing agents, meaning they remove electrons from other compounds during chemical reactions. But whereas chlorine has the capacity to take in two electrons, chlorine dioxide has the capacity to absorb five in highly acidic environments. In a neutral ambient, as in swimming pools and drinking water, ClO2 takes only one electron.

In addition, chlorine dioxide does not react with many organic compounds, meaning it does not create chlorinated organics, which can be environmentally dangerous.

5. Is ClO2 corrosive?

When used at the concentrations required for disinfection without accumulation e.g., in loops, chlorine dioxide is minimally corrosive. Chlorine dioxide is approximately ten times more soluble in water than chlorine and safe methods for chlorine dioxide production have been developed, meaning the corrosive effects of using chlorine dioxide for treatment are minimal.

6. Can ClO2 contribute to reducing biofilms in pipelines?

ClO2 removes biofilms and keeps them under control. Through this, it helps to reduce steel corrosion in an indirect way.

7. How reactive and efficient is ClO2?

Chlorine dioxide is known as an effective water treatment method because of its oxidation capacity at low levels. The predominant effect is the enrichment of dissolved gaseous chlorine dioxide at boundary where microorganisms find their ideal conditions for survival.

The high efficiency of chlorine dioxide at low concentrations versus other disinfectants can be seen when comparing its c x t - numbers with other chlorine species.

8. Is ClO2 toxic and can it be stored safely?

Chlorine dioxide cannot be stored as a gas because at concentrations over 10%, or under pressure, there is a risk of explosion by self-decomposition.

If stored for extended periods of time, chlorine dioxide will mainly form the intermediate by product chlorite, finally ending in chlorate. A dissociation into chlorine and oxygen only occurs in the gas phase. For these reasons, chlorine dioxide is stored as a solution at concentrations of around 0.3 % ClO2 (3 g/L) and kept away from light and heat. Under these conditions, chlorine dioxide is stable and soluble.

10. Which are the most common applications using ClO2 for water disinfection?

The most common applications of CIO2 in water treatment are in Poultry and Hatchery, Agriculture, Aquaculture, Meat Processing , Dairy Farm, Food and Beverage Processing ,potable water, swimming pools & water parks, cooling towers, utility water and wastewater.

11. How efficient is ClO2 compared with Chlorine, Hypochlorite's, and Ozone?

ClO2 is a relatively mild oxidant with a low ORP value in comparison to hypochlorous acid. It oxidizes to generate chlorinated DBP, including THM, as chlorine and hypochlorites do.

In addition, it has an excellent residual effect in purified water whereas ozone is depleted by self-decomposition. Once ozone has vanished, the regrowth of germs accelerates, which doesn't happen with chlorine dioxide.

12. How do I solve the chlorate issues of ClO2 application?

When ClO2 interacts with water ingredients and decomposes in feedstock solutions, chlorate is generated. The chlorate formation can be minimized by accurate selection of the generation process (batch or inline) and design of the system - the size of the generator, size of the dosing system, and size of the batch tank.

Chlorine dioxide has been proven as a powerful disinfectant and oxidizing agent that works at lower residual levels than other common disinfectants. With a low reactivity to organic compounds, CLO2 also minimizes chlorinated organics in the treatment process, meaning it may be the optimum choice for cooling tower treatment.

Chlorine Dioxide (CAs No 10049-04-4) is an approved and allowed substance for human and animal consumption according to EU, USEPA, WHO standards, and many national drinking water regulations.