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Chlorine Dioxide - A Technical View

What is Chlorine Dioxide?

Like ozone and chlorine, chlorine dioxide is an oxidizing biocide and not a metabolic toxin. This means that chlorine dioxide oxidizes microorganisms by the disruption of the transport of nutrients across the cell wall, not by disruption of a metabolic process.

How does it work?

Of the oxidizing biocides, chlorine dioxide is the most selective oxidant. Both ozone and chlorine are much more reactive than chlorine dioxide, and they will be consumed by most organic compounds. Chlorine dioxide however, reacts only with reduced sulphur compounds, secondary and tertiary amines, and some other highly reduced and reactive organics. This allows much lower dosages of chlorine dioxide to achieve a more stable residual than either chlorine or ozone. Chlorine dioxide, generated properly (all chlorine dioxide is not created equal), can be effectively used in much higher organic loading than either ozone or chlorine because of its selectivity.

How effective is it?

The affectivity of chlorine dioxide as a gas or when dissolved in water is at least as high as chlorine, though at lower concentrations. But there are more and important advantages.

  • Chlorine dioxide is clearly superior to chlorine in the oxidation of spores and fungus on an equal residual base.
  • Chlorine dioxide can be used as a gas like ozone but not chlorine, without the destructive oxidizing side effects of ozone.
  • The required contact time for ClO2 is lower;
  • Chlorine dioxide has better solubility in water;
  • No corrosion associated with high chlorine concentrations. Reduces long term maintenance costs;
  • Chlorine dioxide does not react with NH3 or NH4+;
  • It oxidizes THM precursors and increases coagulation;
  • ClO2 oxidizes phenols and has no distinct smell;
  • It is better at removing iron and magnesia compounds than chlorine, especially complex bounds;

When used in its gaseous form, ClO2 provides all the benefits of ClO2 dissolved in water with the clear advantage that there is no water to contend with and it can infiltrate areas that water based ClO2 can not reach or be used in given that appropriate air movement is provided. The water dissolved ClO2 does, however, deliver a much higher concentration of ClO2 where the solution is applied.

In the past producing ClO2 gas required large and expensive machinery, but with the introduction of OdorXit ClO2 Dry Media design, no machinery, electric, supervising manpower, or water supply is required. The packets once exposed to water or humid air produce low but effective levels of ClO2 gas.

There are two basic modes of operation for the packets based on the amount of water/water vapor the packet has access to. The fast mode can be implemented with as little as 10 drips of water applied directly to the tyvek packet or the packet can be placed in a flat bottom cup with just 1/8 of an inch of water. The slow mode requires as little as 40% relative humidity to produce low levels of ClO2 for as long as 30 days. Higher levels of relative humility (approaching 100% RH will increase the ClO2 production and shorten the life of the packet to as little as 15 or 20 days while still producing safe levels of ClO2.

The Fast Release mode, the packet produces enough gas per hour to raise ClO2 levels high enough to require that people and pets be removed from the area being treated (usually 24 hours or less).

The Slow Release mode produces much smaller amounts of gas per hour for 20 to 30 days. Used as advised, ClO2 levels never exceed .01 ppm which is considerably below levels that are considered an irritant or dangerous.

In its gaseous state, ClO2 works very well even at extremely low concentrations. We have seen evidence that suggest that the Slow Release mode of the product actually does better at oxidizing mold and mold spores and fungus than the Fast Release mode.

General Background Information On Chlorine Dioxide

Chlorine dioxide is effective at low concentrations across a wide range of pH (roughly 4 to 9), and, because it is a gas in its natural state, dissipates upon exposure to sunlight As a consequence, it is known widely as one of the most effective inhibitors of algae, yeast, mold, and fungi. However, because transporting the gas is prohibited in all but frozen forms, pure chlorine dioxide has heretofore been limited to use in large concerns that employ chemical generators, such as pulp mills (controlling slime) and municipal water systems (water purification applications).

Similarly, in cleaning and anti microbial knockdown applications, pure chlorine dioxide has previously been unavailable, and only with "stabilized" solutions or acidified sodium chlorite, which are corrosive and produce significant chemical residues, could any of the advantages of chlorine dioxide be realized.

Dry Media Chlorine Dioxide (dmClO2™)

The OdorXit ClO2 package design created a truly portable ClO2 delivery system called “Dry Media Chlorine Dioxide (dmClO2™)”.   dmClO2™ is easy to use for many types of small- and medium- sized applications and requires no electricity to generate a pure solution of ClO2.  Dry media chlorine dioxide significantly expands opportunities for the safe use of chlorine dioxide while reducing associated costs in many applications.

In some uses, dry media chlorine dioxide can eliminate the need for chlorine dioxide generators, multiple chemical requirements, and greatly reduce shipping and storage costs while increasing ease of use and safety considerations.  The simplicity and inherent safety of the dmClO2™ may also reduce requirements for costly technical personnel.

The Dry Media design products are simple, efficient delivery systems based on portable engineered pouches ideal for multiple point-of-use applications of ClO2.  These portable pouches are small enough to be easily stored but capable of generating up to several thousand gallons of sanitizing and disinfecting solutions and gasses.

Most commercial disinfectants are manufactured in solution containing large volumes of water resulting in costly transportation, storage and end-use costs.  The dry-media chlorine dioxide (dmClO2™) technology only requires moisture activation to produce a ready-to-use liquid solution of ClO2 or to produce low concentrations of ClO2 gas in the air.  Active solutions of ClO2 can be used in multiple industrial and institutional applications ranging from potable water disinfections to surface sanitation.

dmClO2 Generation Mechanism

The dmClO2 device combines the utilization of membrane technology with a custom made heat-sealing procedure resulting in a defined space called the Membrane Micro Reactor (M2R™), where the reaction takes place. Within the M2R™, the conversion of sodium chlorite to chlorine dioxide is governed by the

  • transport phenomenon of water and/or moisture into the M2R™
  • dissolution rate of the ClO2 precursors
  • reaction kinetics of ClO2 generation
  • controlled release of ClO2 gas or ClO2 in solution.

The design of the M2R™ provides a defined physical space having a favorable environment for an efficient conversion of sodium chlorite to chorine dioxide. This conversion results in an economical process for the production of chlorine dioxide with minimum amounts of un-reacted species and undesired by-products.

Other devices currently available rely on the mixture of un-separated reactants in one device or the mixture of solutions of the reactants. In either case, the conversion and therefore the cost effectiveness is not economically attractive; these methods yield ClO2 with a high level of by-products.

Avoiding THMs with Chlorine Dioxide

One of the major advantages in using ClO2 is that it does not form chlorinated organic byproducts.  ClO2 is structurally different than chlorine and reacts with organic matter through different pathways.  Chlorine chlorinates organic matter, forming chlorinated byproducts.

Many chlorinated organic compounds have been found to be carcinogenic, such as trihalomethanes (THMs). Alternatively, ClO2 reacts with organic matter through an oxidation-reduction reaction.  ClO2 oxidizes the organic matter and is itself reduced to the chlorite ion, and eventually to the chloride ion.  Thus, disinfection with ClO2 does not result in carcinogenic compounds.
Recently, studies linking THMs to health problems have caused concern over the presence of THMs in drinking water.  As Total THM (TTHM) regulations become stricter, it is anticipated that more water treatment facilities will turn to ClO2 to lower THM levels in treated water.

The Development Of MRSA And Its Increasing Resistance To Antibiotics

Staphylococcus aurous (SA)-Antibiotic Resistance (General): Throughout history, Staphylococcus aurous (SA) has been a dangerous pathogen once it has successfully breached the normal defense system. The first effective antibiotic against SA, penicillin, became available in the 1940s. Soon after, SA evolved resistance to penicillin, and by the late 1950s, 50 percent of all SA strains were resistant. Today, fewer than 10 percent of SA infections can be cured with penicillin.

The next weapons against SA, methicillin and cephalosporin, became available in the 1960s and 1970s. By the late 1970s, some strains of SA had evolved resistance to these drugs. Today, as many as 50 percent of SA strains isolated from U.S. hospitals are resistant to methicillin. (Source: National Institutes of Health)

New MRSA Bacteria Oxidizer Registered by EPA

Main Category: MRSA / Drug Resistance News

Article Date: 04 Sep 2005 - 10:00 PDT The EPA (Environmental Protection Agency) has recently registered a new product for preventing and eliminating methicillin-resistant Staphylococcus aurous (MRSA), which causes potentially deadly infections commonly known as "staph" infections. The MRSA "super bug" is typically contracted in hospitals, in other healthcare environments, and in health clubs and locker rooms.

The EPA has registered chlorine dioxide dissolved in water for use as a disinfectant on hard, non-porous surfaces and instruments, including those used within hospitals and other medical settings. As a no-wipe, no-rinse spray, hydrated chlorine dioxide can also be used on hard, non-porous surfaces in health clubs, spas, public places and swimming facilities as a treatment against MRSA. The EPA has also registered hydrated chlorine dioxide as a disinfectant for vancomycin-resistant Enterococcus faecalis, athlete's foot, Mycobacterium bovis (TB) and other pathogens that spread in many environments.

Though this product was not OdorXit ClO2 Dry Media, OdorXit ClO2 Dry Media has been registered with the EPA as well and uses the same ClO2 technology plus the gas version of the technology.

MRSA is usually spread by direct physical contact with those already infected or through indirect contact by touching objects (towels, clothes, sports equipment, etc.) that infected skin has contaminated. Consequently, any heavily trafficked area can be a source of infection.

According to a report by the BBC News, "Staphylococcus aurous is the leading cause of human infections in the skin and soft tissues, bones and joints, abscesses and normal heart valves. It flourishes in the hospital setting, producing bloodstream and surgical wound infections, including MRSA." (news.bbc.co.uk/1/hi/health/4671585.stm)

How OdorXit ClO2 Oxidizes MRSA And Other Deadly Pathogens

Chlorine dioxide is an ideal biocide because of its ability to oxidize viruses, bacteria, fungi, and algae at low saturation levels (parts per million) in a manner that does not allow pathogens to build resistance to the compound. The gas generating form of the product can easily and safely be used in locker rooms, inside lockers, bathrooms, equipment storage rooms, bins, and carry bags. 

Prior to OdorXit ClO2, healthcare and health club environments were limited to using substances like bleach and quaternary ammonium compounds that can leave residue and require higher concentrations than does chlorine dioxide to achieve the same efficacy.
Chlorine dioxide can be produced as a pure gas where it can oxidize materials on all surfaces and materials or dissolved in water and sprayed, mopped, or sponged onto surfaces that require cleaning.

After application of the liquid product, the solution is left on target surfaces and does not require rinsing. Due to the comparatively low application concentrations required to oxidize pathogens, hydrated ClO2 is compatible with most materials. Gaseous ClO2 requires not rinsing or cleanup of any kind since there is not residual build up.

Odor Management

Air quality is equally as important as water quality and has received considerable attention in the last few years by consumers as well as regulatory and governmental agencies. The market is literally flooded with deodorizers, which basically "mask" the odor with some sort of fragrance.

Odors can be caused by a number of factors and often are associated with bacterial presence and action, food processing, smoke, and industrial processes. The list of chemical substances causing odor is very extensive but most odor-causing compounds are derived from sulfur and nitrogen compounds such as amines, cyanides, hydrogen sulfide, mercaptan's, aldehydes and phenols.

Odor problems are not only affected by the source of the pollutant but also by environmental conditions such as humidity, temperature and air movement. Ventilation systems play a key role in the control of odors in confined spaces such as buildings, storage rooms, processing areas, homes and residences.

The most effective methods of eliminating odor-causing compounds are air scrubbing and chemical destruction. Air scrubbers are normally used in industrial settings and in processes which involve a continuous release of air-borne pollutants. Air scrubbing involves sophisticated and well-engineered systems requiring substantial capital, maintenance and training. 

One of the key properties of ClO2 is its ability to selectively oxidize chemical compounds. In addition, ClO2 has the ability to inhibit and oxidize bacteria, viruses, and protozoa. The combination of selective oxidation and bacterial inhibition make ClO2 a powerful tool to control odors in confined spaces. The OdorXit ClO2 Dry Media design controls odor-causing bacteria, mold, mildew, and chemical odors. This product is based on the generation of ClO2 gas and is capable of generating a controlled concentration of ClO2 in the air based on specific ratios of relative humidity and temperature.

The OdorXit ClO2 Dry Media products are designed to produce specific concentrations of ClO2 in a given air volume while meeting the current OSHA permissible exposure limit (PEL) of 0.1 ppm as an 8-hour time-weighted average. Choosing the proper sized product is key to the safe and affective use in a well defined closed space.

History of Chlorine Dioxide

The chemistry of chlorine dioxide (ClO2) has been known since the early 1800’s, when it was discovered by Sir Humphrey Davy.

ClO2 proceeded to gain recognition as a disinfectant and an oxidant, and in the 1950’s, ClO2 attained widespread commercial use as a bleaching agent in the pulp and paper industry. In 1967, the USEPA registered the ClO2 dissolved in water form as a disinfectant and sanitizer. Subsequently, in the 1970’s, the use of ClO2 as a disinfectant for drinking water was developed.
In 1988, the USEPA registered ClO2 gas as a sterilant. 

Recently growing concern about Trihalomethanes (THMs), a carcinogenic disinfection byproduct, has caused researchers to focus on ClO2 as an alternative drinking water disinfectant over other chlorine based products..

While chlorine, hypo chlorite, and other chlorine-related disinfectants produce carcinogenic chlorinated organic byproducts, ClO2 does not.

Today, ClO2 is used in 700-900 US drinking water facilities, mainly for taste and odor control as well as to meet increasingly strict THM regulations.
Chlorine dioxide is perhaps the most versatile oxidizer in terms of its capacity to oxidize most pathogenic microorganisms.

While ClO2 has chlorine in its name, ClO2 reaction chemistry is radically different from that of chlorine. Chlorine dioxide is a stable free radical and functions via an oxidative rather than a chlorinating reaction.

Chemistry of Chlorine Dioxide

Chlorine dioxide’s oxidative power allows it to disrupt the cell membranes of microorganisms, so that nutrients cannot be transported into the cell.  Many commonly used disinfectants are not effective against the cell membrane and instead interrupt the metabolism of the microorganism.

Over time, the microorganisms can develop resistance to disinfectants.  With ClO2, however, the microorganism does not have a chance to develop resistance because it is oxidized upon contact with ClO2.

Some oxidizers can be too powerful in their oxidation.  ClO2 is unique because, although it is highly oxidative, it is also highly selective.

This means that ClO2 does not react with whatever material is present; it selectively oxidizes certain microorganisms and is not wasted on benign matter.  Due to its oxidizing power, ClO2 has excellent capability to penetrate bio films where certain bacteria such as Legionella hide and cannot be oxidized by most disinfectants including chlorine.

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