Posts Tagged ‘bleach’

Identifying and eradicating biofilm (with HOCL)

November 12, 2018

Steps to eliminate an age-old hazard from the health care environment

June 6, 2018

John Scherberger, FAHE, CHESP

Biofilms serve as protective coatings for microbes to shield them from unfavorable environments.

Biofilms are complex colonies of microorganisms that serve as protective coatings for microbes to shield them from unfavorable environments such as heat, ultraviolet light, cold, disinfectant chemicals and antibacterial drugs used in health care.

The components of biofilm greatly heighten bacteria’s resistance to antibiotics, thus enhancing the longevity and potential harm caused by bacteria.


It often appears as slime and discoloring that can be seen in sink and floor drains, buildup around leaking faucets and faucet sprayers, unused toilets and floor mop sinks, hoppers found in soiled utility rooms in hospitals and janitors’ closets in commercial buildings. But biofilm is not always easily seen because it is found in many out-of-the-way locations such as air handlers, air conditioning evaporation trays, water cooling towers, and water coolers, features and fountains.

When biofilm is seen and (most often) not seen, bacteria are present and must be treated and approached with caution and concern.

Biofilm and health

Biofilm has existed as long as bacteria have been on the planet. But it wasn’t until the early 1970s that scientists began to understand the major impact biofilm had on human health; and scientists only began to understand the complexity of biofilms in the 1980s and 1990s.

It is not just an annoyance or another nuisance to be casually addressed by environmental services (ES) or facilities departments. It is an ever-present threat to health and the environment.


For instance, recent studies and investigations have shown that biofilm has been a major contributing factor in harm caused by improper or incomplete processing of medical devices and implants such as catheters, prosthetic joints and heart valves. Despite standardized processes thought to be effective at sterilizing medical instruments, biofilm is so pervasive and robust that numerous serious patient outcomes have resulted.

Failure to properly reprocess medical instruments to eradicate and remove biofilm during reprocessing of instruments like endoscopes prior to surgical procedures has resulted in infections such as carbapenem-resistant Enterobacteriaceae (CRE) being transferred to patients. As a result, the Centers for Disease Control and Prevention (CDC) established new procedures to ensure biofilm eradication is addressed when endoscopes are processed.

A hospital must be addressed in a universal manner because one area can have an impact upon another — even on other floors or nonintegrated departments. Too often, ES departments are not called upon to address issues found in nonclinical areas of hospitals.

For example, one area not typically addressed by the ES department in its constant pursuit of hygienic patient environments is food service facilities and locations. Biofilm is not only a constant concern as a source of food spoilage, but also food contact and preparation surface contact because, once food contact surfaces become contaminated with biofilm, it is much more difficult to eradicate the exopolysaccharides and bacterial cells of the bacteria.

Eradication and removal

Bacteria communicate and collaborate via chemical interactions for survival. To eradicate and remove bacteria and biofilm from the health care environment, a multidisciplinary and multimodal approach is essential. No one department can succeed and no one department has all the answers.

Biofilm is dangerous to immunocompromised patients. Therefore, removal and eradication must be concentrated and strategically approached.

Multidisciplinary teams must identify potential sites for targeting, which may include hot and cold water supply lines, idle faucets, drains, bathrooms, floors, moist/damp areas, soiled utility rooms, soiled laundry shafts, ice machine drains and dispensing chutes, water fountains, boiler rooms, air vents and many other areas.

Health facilities professionals who are responsible for the hospital environment must recognize that biofilm is not always seen by casual visual inspection and presents a real danger. These disciplines must also recognize that appropriate personal protective equipment (PPE) always should be used when addressing the removal of biofilm as the nature/virulence of a biofilm always must be considered suspect.

Facilities professionals tasked with locating, eradicating and removing biofilm also should be trained and educated regarding why they should look for it, what to look for and how to eradicate and remove biofilm once located.

Often, those responsible for carrying out biofilm removal are just told to “do it” or “get it done” without any specific directions or knowledge. Left to one’s own inventiveness or lack thereof, results are often minimal or even disastrous.

For example, thinking that pouring bleach or a bleach solution down a drain or on a surface will terminate the issue is shortsighted. Biofilm is produced to protect bacteria from harsh environments and disinfectants such as bleach, and antibiotics fall into the definition of a harsh environment.

ES professionals also should recognize that bleach does not clean; rather it is an oxidizer and disinfectant. Hypochlorous acid (HOCl) is an Environmental Protection Agency (EPA)-registered, hospital-grade disinfectant that is as effective as bleach (if not more) in the biofilm-abolition process and is much safer for the environment, metals, staff and PPE. The odor is not noxious and thus safer for all concerned, particularly if removing biofilm from a closed and fresh-air-deprived environment.

Additionally, hospitals are subject to EPA regulations regarding discharge of residual chlorine into wastewater. If an incorrect solution is applied, the possibility exists of exceeding the maximum residual chlorine level into the waste stream.

HOCl is considered a safe alternative to bleach for its disinfecting ability and is safer for personnel to use. However, ES professionals must have a complete understanding of both bleach and HOCl reactivity. With both solutions, there is still the potential for danger if ammonia is present. Both solutions, when mixed with ammonia, are hazardous. Neither HOCl nor sodium hypochlorite should ever be introduced directly into any drain without first flushing the drain with clean water. If ammonia in any form is present, doing so may result in chloramine gas being released, which may cause respiratory distress or death.

Disruption and eradication

Biofilm in the health care environment — as opposed to being present on implants or other implements introduced into a body — must be disrupted through mechanical or physical action.

Once a multidisciplinary and multimodal team has been identified and trained, how the process is implemented is vital. The following actions may be used or adapted by ES professionals:

  • If possible, determine the type or identity of the biofilm to be removed to know the best process to implement.
  • Discuss what chemical/disinfectant is to be used and how it is to be applied.
  • The decision to manually scrub with a brush and a bucket of cleaner/disinfectant is usually one of the first to be considered and dismissed. But, just as in medicine, the guiding principle for removal and eradication of biofilm should be to use the most appropriate and efficient method without disrupting or causing harm to surrounding areas.
  • Scrubbing or high-pressure spraying is most often the choice, but must be appropriate to the environment and conditions personnel may encounter. Methods and chemicals will be dictated by accessibility, electrical considerations, the patient care environment and restricted areas such as pharmacies, intensive care units or research labs.
  • Steam is also one of the most useful multimodal interventions that can be used in combating biofilm. Two types of steam generators are normally available for health care ES: low-pressure/high temperature electric powered, usually with a self-contained steam chamber that uses manual effort in combination with mechanical action (brushes or microfiber cloths) designed for small spaces; and high-pressure/high-temperature generators that are fully electric or a combination of electric/gas units connected to water supply sources via hoses. These units rely on high-pressure water nozzles to disrupt and remove biofilm. The high temperature of both types of generators dislocates and kills the cells, and the manual or mechanical pressure physically removes the biofilm and most biofilm molecules from surfaces. Again, the environment in which the biofilm is located must be considered.
  • The physical removal of the biofilm must be followed by removing any remaining contaminated water from floor, metal or other surfaces lest any bacteria remaining be allowed to repopulate the contact surfaces.
  • The previous step should be followed by a clean-water rinse followed by an application of a properly diluted solution of a germicidal agent such as HOCl.

Proper and appropriate PPE must be used and documented. Implementation of the buddy system — especially in closed and potentially dangerous environments — must be followed.

ES professionals must use safe and effective cleaners and disinfectants for cleaning and disinfecting brushes, wipers, buckets, scrapers, mops, steam generators, wet vacuum cleaners and attachments, and clothing/footwear that may have been contaminated. Proper hand washing after completion of the assigned tasks must be followed as well.

Training required

Proper processing of clinical and aesthetic surfaces (cleaning and disinfecting with proper tools that trap and remove bacteria and unseen biofilm) is an essential step toward the goal of a healthy, hygienic patient care environment. Biofilm will never be completely eradicated from the health care environment, but every reasonable effort to prevent its presence and proliferation must be taken.

Formal training of ES and facilities staff regarding the virulence and ubiquitous nature of biofilm must be a priority.

The Association for the Healthcare Environment’s Certified Healthcare Environmental Services Professional, Certified Healthcare Environmental Services Technician and Certified Surgical Cleaning Technician programs are excellent first steps in addressing the importance of proper processes and techniques to address biofilm.

John Scherberger, FAHE, CHESP, is president and founder of Healthcare Risk Mitigation, Spartanburg, S.C. He can be contacted via email at

How bleach kills germs

August 27, 2013

Bleach has been killing germs for more than 200 years but it was only since 2008 that U.S. scientists figured out how the cleaner does its dirty work.

It seems that hypochlorous acid, the active ingredient in bleach, attacks proteins in bacteria, causing them to clump up much like an egg that has been boiled, a team at the University of Michigan reported in the journal Cell on Thursday.

The discovery, which may better explain how humans fight off infections, came quite by accident.

“As so often happens in science, we did not set out to address this question,” Ursula Jakob, who led the team, said in a statement.

The researchers had been studying a bacterial protein called heat shock protein 33, which is a kind of molecular chaperon that becomes active when cells are in distress, for example from the high temperature of a fever.

In this case, the source of the distress was hypochlorous acid or hypochlorite.

Jakob’s team figured out that bleach and high temperatures have very similar effects on proteins.

When they exposed the bacteria to bleach, the heat shock protein became active in an attempt to protect other proteins in the bacteria from losing their chemical structure, forming clumps that would eventually die off.

“Many of the proteins that hypochlorite attacks are essential for bacterial growth, so inactivating those proteins likely kills the bacteria,” Marianne Ilbert, a postdoctoral fellow in Jakob’s lab, said in a statement.

The researchers said the human immune system produces hypochlorous acid in response to infection but the substance does not kill only the bacterial invaders. It kills human cells too, which may explain how tissue is destroyed in chronic inflammation.

“Hypochlorous acid is an important part of host defense,” Jakob said. “It’s not just something we use on our countertops.”

This post has been posted in 2008. Mentioned Journal article available upon request.

Chlorine – A Great Disinfectant!

December 16, 2010

There are distinct differences between a Sodium Hypochlorite solution, a Calcium Hypochlorite solution and an onsite generated Hypochlorous Acid solution.

Sodium Hypochlorite Solution (NAOCL)

Sodium Hypochlorite solution often called bleach usually containing LYE is manufactured at a factory, stored, shipped to distribution centers, stored again and then sold.

Calcium Hypochlorite Solution (CAOCL)

Dry Calcium Hypochlorite tablets produce a “FRESH” Hypochlorite solution when mixed with water. In tests done, a solution produced with the proper Calcium Hypochlorite tablet, can maintain “Free Available Chlorine” or Hypochlorous Acid the
active disinfectant in this Calcium Hypochlorite solution, for ONLY about 4 hrs, then it starts rapidly degrading.

Hypochlorous Acid Solution (HOCL)

Until now, HOCl has simply been thought of as a transient byproduct in the ubiquitous chlorine chemical family. However, HOCl generated by ECA technology carries with it fewer negative hydroxides than the previous HOCl formed via disassociation from sodium hypochlorite. Because of this, ECA-generated HOCl behaves uniquely and must be considered separately from chlorine. HOCl as a stand-alone chemical, separate from chlorine, has not been available in the market until now. This breakthrough results in a need for a paradigm shift in biocidal approaches. HOCl is an “old”, well appreciated chemical but is now “new” availabie as onsite generated solution.

1. Free available Chlorine content

For a chlorine solution to be a good disinfectant it must meet the Chlorine Demand. The chlorine demand is the amount of Free Available Chlorine (FAC) often called Hypochlorous Acid (HOCl), needed to disinfect or oxidize organic matter before a FAC residual is reached. If the chlorine demand is not met then complete disinfection has not been obtained. One of the best signs that the Chlorine Demand has not been met is the strong chlorine odor.

If a chlorine solution is does not contain enough HOCl to satisfy the chlorine demand of the surface or product to be disinfected, chloramines will form as chlorine and nitrogen-based materials combine. Examples of nitrogen-based materials are proteins and blood. Chloramines are responsible for the obnoxious odor sometimes associated with chlorine disinfection. The obnoxious, pungent, eye-stinging smell of chloramines, mistakenly identified as free chlorine, indicates that the chlorine/water mix is not effective. There is not enough HOCl to satisfy the chlorine demand

2. Chlorine Efficacy determined by pH

Chlorine in water splits into two forms, Hypochlorous Acid (HOCl) and Hypochlorite Ion (OCl-). At the high pH the chlorine provided by bleach contains a maxiimum of Hypochlorite Ion. The chlorine produced by onsite Electrolyses in an Aquaox System contains a maximum concentration of Hypochlorous Acid (HOCl).

How much of each is present in a chlorine solution is totally dependent upon the pH of the solution. As pH rises, less Hypochlorous Acid and more Hypochlorite Ion is in the solution. As the pH rises, less germ killing power is available. According to a University of Illinois study, HOCl is 120 times more effective as a sanitizer than the -OCl ion. The ideal pH of a disinfecting chlorine solution is a pH of 6-7.

Most FRESH Calcium Hypochlorite solutions have a pH of between 7 and 8.  ALL (fresh or old) Sodium Hypochlorite solutions, (“bleach”) have a pH of 10.25+ producing NO HOCl at all! These solutions produce only the OCl- ion, a very poor disinfectant which is from 80 to 120 times less effective as a disinfectant than HOCl, providing that there is any chlorine left in the stock solution.

3. Contact time

The amount of time that chlorine is present during treatment is called the contact time. Contact times are calculated to determine the amount of time that a disinfectant must be present in the system to achieve a specific kill of microorganisms, for a given disinfectant concentration. A long contact time  means that disinfection alone will not be sufficient treatment and additional methods will be necessary to eliminate the microorganisms.  The contact time is directly related to the chemicals’ efficiency of eliminating bacteria and viruses from the water. HOCl requires by far the shortest contact time to achieve a 99% kill of E. coli (Reynolds, 1996).

4. Shelf-life and added lye

Finally, just as champagne or carbonated water “go flat” on sitting as the bubbly carbon dioxide gas escapes into the air, chlorine escapes from a Hypochlorite solution thus weakening its germ killing value. In order to slow this escape, bleach manufacturers add Sodium Hydroxide (lye) to their product causing the pH to rise dramatically. Lye burns animal and plant tissues; it saponifies (converts) fats in poultry and meat products. Hypochlorous Acid dispensed from Aquaox Systems contains NO LYE!

According to all the technical literature, depending on storage conditions; ALL Hypochlorite solutions will lose half of their potency in less than thirty days. Light, temperature and age are the biggest factors.  The biggest misconception is that liquid household bleach (Sodium Hypochlorite) does not loose potency until you make a Sodium Hypochlorite solution; “liquid household bleach” is already a Sodium Hypochlorite solution, that starts degrading soon after manufacture, so a “bleach” bottle bought at a retail store or chemical supply house is, NOT a FRESH Hypochlorite solution. It is a Hypochlorite solution with an unknown chlorine content, so when we make a solution all we are doing is diluting an already weak Hypochlorite solution even more. All literature recommends that if you are using “chlorine bleach”, daily tests should be conducted by a laboratory to assure its potency.

Why Use onsite produced Hypochlorous Acid solutions instead of Calcium or Sodium Hypochlorite solutions?

1. Onsite electrolyses of a brine solution in Aquaox Systems produce a maximum of Hypochlorous Acid whereas pH can be accurately set and controlled anywhere between 3-7.

2. At an pH of ~5 the Hypochlorous Acid solution consist almost solely of Free Available Chlorine and maximum disinfection is achieved.

3. Hypochlorous Acid requires the shortest contact time to eradicate a microorganism.

4. As Hypochlorous Acid is produced onsite, there is no need of mixing and dilution of Hypochlorite solutions with unknown chlorine content. Shelf life is no issue, as Hypochlorous Acid solutions are produced on demand. Therefore no addition of Lye is required, as shelf life became more or less irrelevant.


George Clifford White, Handbook of Chlorination and Alternative Disinfectants. Third Edition, Van Nostrand Reinhold, New York, 1999.

George R. Dychdala. Chlorine and Chlorine Compounds. In: Block SS, ed. Disinfection, Sterilization, and Preservation, 5th ed. Philadelphia Lippincott Williams & Wilkins, 2001.

EPA Regulations with regard to Onsite production, Usage, Storage and Transport of Onsite produced Hypochlorous Acid (HOCL).

May 10, 2010

M. van Schaik


There is a lot of confusion whether Electrolyzed Water is allowed to be used as a disinfectant or sanitizer. EPA, FDA, USDA and local authorities have approved or allowed usage of Electrolyzed Water in many applications. Having said so, a few applications need more data about the efficacy of Electrolyzed Water and methods how disinfection or sanitation is guaranteed. Other applications may have a limitation on the HOCL concentration.  The following article explain what is and what is not allowed by the US Environment Protection Agency.

EPA Regulation with regard to Onsite PRODUCTION of pesticides with AQUAOX Devices

Under Section 3 of the Pesticide Regulations under the Federal Insecticide Fungicide and Rodenticide Act, as amended (FIFRA), the EPA regulates pesticides, which are registered and sold in interstate commerce to control various forms of vermin.

Under these regulations (Subpart Z –Devices Part 152.500  ‘Requirement for devices”) Pesticide Devices are not required to be registered, but must have an approved label which meet the Section 3 Regulations, Part 162.10, and have a registered establishment in which they are produced. Under Section 7 of the FIFRA each owner of a pesticide device must produce to the EPA enforcement program a report of products produced each and every year and to whom they are sold in a standard report form.

Devices which everyone has heard about are electrically generated, ozonators for use in treating drinking water, chlorinators which derive Free Available Chlorine from the electrolysis of water and sale, copper/silver cathodes which by electrically activity cause release of silver and cupper ions into drinking water in hotels and hospitals, invisible noise mechanisms which mediate insects and rodents in small areas.  In each case the device is unique and based upon the data which the device originator has in hand or can reference to EPA has a product which is efficacious and safe when used as directed.

Devices are subject to labelling and misbranding requirements under FIFRA section 2(p) and 2(q); registration and reporting requirements under FIFRA section 7; recording keeping requirements under FIFRA section 8; inspection requirements under FIFRA section 9; import and expert restrictions under FIFRA section 17; and child resistant packaging requirements imposed pursuant to FIFRA section 25 (c)(3).

AQUAOX devices hava an EPA establishment number and we report pursuant to Section 7 of the Act.  Basically our device, using electric current 230 volt, produces Hypochlorous Acid (HOCL) on demand on site, which kills bacteria, mold, mildew, viruses and surface filling algae.  The device uses sodium chloride (table salt) in a liquid format in water and an electric charge to generate on demand HOCL-solution. HOCL (200ppm Free Available Chlorine) does the killing of the life forms.  When the electric has been turned off the device produces no HOCL-solution and has no residual in it.  Our device meets all the Section 3 labelling requirements and we pay close attention to all the FIFRA requirements so as to be fully compliant No product is produced from our device for storage or later use per regulations.

Electrolyzed water is approved under 21 CFR 173.315 for direct contact with processed foods. Electrolyzed water is approved for several indirect food contract applications under 21 CFR 172.892, 21 CFR 175.105, 21 CFR 176.170 and 21 CFR 177.2800. It is an approved sanitizer that meets 21 CFR 178.1010. The EPA has also given approval (40 CFR 180.1054) for washing raw foods that are to be consumed without processing.

40 CFR 180.940. HOCL when used as ingredient in an antimicrobial pesticide formulation may be applied to: Food-contact surfaces in public eating places, dairy-processing equipment, and food-processing equipment and utensils. When ready for use, the end-use concentration of all Hypochlorous Acid chemicals in the solution is not to exceed 200 ppm determined as Free Available Chlorine

AQUAOX device does not require a hazardous use permit whereas chlorine in bottles must be permitted for filling, transportation or storage.

In case of doubt or for clarification AQUAOX LLC should be consulted. We are unable to anticipate all conditions under which the product may be used, and users are advised to carry out an assessment of workplace risk and carry out their own tests to determine Safety and Suitability for the process and conditions of use.

EPA regulation with regard to the USAGE and STORAGE of Neutral Electrolyzed Water generated on-site from an AQUAOX device

Under the FIFRA, EPA does not regulate water or sodium chloride (table salt) as a pesticide when used in an AQUAOX device that generates a pesticidal solution (HOCL).

The 0.2% HOCL-solution generated by the AQUAOX device is not regulated by the EPA as a pesticide as long as the solution itself is used on-site (i.e. where it is generated). If however, the solution is packaged, distributed or sold for use other than the site at which it was generated, then the product is subject to registration as a pesticide under FIFRA.

Accordingly, applying the solution on-site in e.g. 1 gallon containers would not be subject to registration, but distributing and selling the product for use other than at the site of generation would be subject to registration. Finally, the AQUAOX Device is considered to be a pesticide device and is subject to the requirements specified in 40 CFR 152.500.

As long as the HOCL-solution is applied on-site, no EPA requirements under FIFRA apply other than those specified above. EPA recommends, however, that the operator of pesticide devices provide labels for plastic containers with HOCL-solutions, so that workers and others will know what is in the containers and what precautions and directions should be followed handling and using the solution.

Thus, temporary storage of the HOCL-solution is allowed, as long as HOCL-solution is used on-site.

Finally, the operator of the AQUAOX device should check as to state and local regulatory requirements that may apply to the AQUAOX device and the generated solution.

EPA regulation with regard to TRANSPORT of Neutral Electrolyzed Water generated on-site from an AQUAOX device.

Under FIFRA, EPA does not provide a clear rule and this need to be further investigated. Most probably EPA will NOT permit transport as onsite produced HOCL-solutions are strictly intended to be used on-site.

AQUAOX’ interpretation of the FIFRA is that transport of HOCL-solution within the on-site location is permitted, as long as HOCL-solution is used on-site.  Thus, transport of HOCL-solution in e.g. 1 gallon container to another department, building or place within the operator’s organization, company and/or location is permitted, as long HOCL-solution is used within the operator’s organization, company and/or location.

Accordingly, storage in trucks should be permitted, as long HOCL is used within the operator’s organization, company and/or location. In AQUAOX’ opinion Onsite generated HOCL is permitted to be transported over the public road to another location to be used within the operator’s organization, company and/or location is. However, FIFRA is very unclear about this particularly kind of transport. Likewise the EPA, AQUAOX recommends to provide labels and a MSDS of HOCL on all containers or trucks filled with HOCL.

On top of this AQUAOX advices to have a FUNCTIONAL and WORKING AQUAOX device on each truck, to be used for onsite generation of HOCL, if a user is going to transport HOCL to a client for executing a service such as e.g. fogging a premises or spraying a surface.

EPA regulation on on-site generated pesticides BOTTLED, PACKAGED, STORAGED and DISTRIBUTED (SOLD).

If the onsite produced HOCL is bottled, packaged, stored, distributed and sold, the HOCL-solution is subject to registration as a pesticide. Thus, if HOCL is bottled, packed and sold as a liquid, the user of AQUAOX’ Device MUST register HOCL as a pesticide to obtain a registration number for HOCL.

The registration of the onsite generated HOCL MUST be in the operator’s name and the operator will be exclusively responsible for the produced pesticide.


AQUAOX is NOT involved in bottling, packaging and distributing pesticides. AQUAOX manufactures, distribute and sell AQUAOX devices which are regulated by the EPA as onsite pesticide devices.

AQUAOX does not permit their distributors to register HOCL (onsite generated pesticide) as a pesticide.

AQUAOX does not advocate, nor promote users (owners/ final users of the AQUAOX Device) to register HOCL as pesticide. AQUAOX rejects all liability, if users do not comply with the FIFRA regulations for onsite pesticide devices. AQUAOX does not advocate or promote the usage of HOCL otherwise than used onsite.

For more information, visit


February 25, 2010

When bacterial cells are exposed to a sanitizers or disinfectant, various physical structures within the cell may sustain irreversible damage. The permanent loss of a bacterial cell’s capability to reproduce is commonly referred to microbial death. In the presence of germicides, some bacteria, may only be partially damaged. A surface which is swabbed immediately after sanitization can often provide false or negative results, indicating that effective sanitization had occurred. However, depending on the degree, partially inactivated bacteria have the capacity to “heal” or regenerate within 18 to 24 hours and become viable. Such an “apparently” clean and bacteria free surface will show the presence of high levels of bacterial contamination the following day and if left unchecked, can contaminate food products which may come into contact with the surface during the normal course of food processing.
The effectiveness of a specific germicide is a function of several factors, including the number and type of microorganisms which are present on the surface being sanitized.
Some of the factors requiring consideration are whether they are the easy to kill bacteria in their vegetative state or whether they are present on the surface as highly resistant spores. A major consideration that also needs to be addressed is whether other materials such as blood, feces or organic matter are are present within the bacterial environment. These contaminants reflecting an unclean surface, can rapidly inactivate some germicides, such as hypochlorites, rendering them ineffective for their intended use.
In general however, germicides exert their effect by either attacking a specific part of the bacterial cell, or causing damage to some of its components. Germicides can fall into three classifications, based on the their method ot bacterial attack.

Germicides such as sodium hypochlorite of peroxyacetic acid (PAA), are strong oxidizing agents and can cause total destruction of the cells membrane, resulting in vital bacterial components leaking out into their surrounding environment. This process results in a true microbial death.

Some germicides, such as the quaternary ammonium compounds (quats), have the capacity to attach themselves onto specific sites on the bacterial cell membrane. They do this by virtue of the fact that the quats carry a positive electrical charge in solution and are attracted to the negatively charged portions of the bacterial membrane. The end result is that quats block the uptake of nutrients into the cell and prevent the excretion of waste products which accumulate within their structure.
In effect, the cell is both starved and internally poisoned from the accumulated wastes.

Biocides, such as phenolics, which exert their activity in this manner actually enter the cell and chemically react with certain key enzymes which support either cell growth or metabolic activities which supplies the bacteria with the energy needed for growth and multiplication. If inactivation is incomplete the injured bacteria can regenerate several hours later and recontaminate the surface.


It is presumed that viral infectivity is supressed, due to the denaturing and break down of the viral protein necessary for infection, though a reaction of that protein with two types of active oxygen present in the Water:
1.Electrolyzed Hypochlorous Acid (HOCL)
2.Hydroxyl radicals (OH)
It is widely believed that the bactericidal effect of Electrolyzed Water (HOCL-solution) against various strains of bacteria is due to the combined action of hydrogen ion concentration, oxidation-reduction-potential (ORP-reactions) and dissolved chlorine (HOCL).
First, ORP-reactions at the cell membrane damage the outer and inner membrane and inactivate the microbes defense mechanism. Then HOCL can penetrate the cell and oxidize it.

Hypochlorous Acid (HOCl, which is electrically neutral) and Hypochlorite Ions (OCl, electrically negative) will form Free Available Chlorine  (FAC) when bound together. This results in disinfection. Both substances have very distinctive behavior.

The cell wall of pathogenic microorganisms is negatively charged by nature. As such, the negatively charged Hypochlorite Ion (OCL-) can only penetrate it by the neutral Hypochlorous Acid (HOCL), rather than.

HOCL itself can penetrate slime layers, cell walls and protective layers of microorganisms and effectively kills pathogens as a result. With the aid of ORP-reaction, HOCL can even easier penetrate cell membranes. The microorganisms will either die or suffer from reproductive failures.

According to Dr. Cloete, the advantages of onsite generated HOCL has been confirmed, wherein the biocidal activity of HOCL generated onsite, is 300 times more active than Sodium Hypochlorite at the same concentration of free available chlorine. Additionally, a concentration of 2% HOCL achieved same results than 0,05% Gluterhaldehyde. Similarly, it has been shown that a 5% solution of Sodium Hypochlorite (only to be used as disinfectant) has equal results than 0.03% HOCL (which can be used as disinfectant and as sporicidal agent).

Thus, Electrolyzed Water (HOCL-Solutions) have been conclusively shown to exceed chemically derived equivalents both in low dosage effectiveness as well as physico-chemical purity.

Michel van Schaik,


January 27, 2010


Chlorine is one of the most commonly used disinfectants for water disinfection. Chlorine can be applied for the deactivation of most microorganisms and it is relatively cheap. Chlorine is commercially available as gaseous Chlorine (CL2) and as Sodium Hypochlorite liquid or powder (NaOCL).

Both gaseous Chlorine (CL2) and Sodium Hypochlorite (NaOCL) have very limited disinfecting properties. It is the formation of chlorine by-products such as Hypochlorous Acid (HOCL), Hypochlorite Ion (OCL-), Hydrochloric Acid (HCL) and Oxygen (O) that inhibit disinfecting properties.

Gaseous Chlorine

Gaseous Chlorine (CL2) is commercially available and mostly used in disinfecting mains water.
When gaseous Chlorine (CL2) added to water (H2O) the following hydrolysis reaction takes place:

Cl2 + H2O = H+ + Cl- + HOCl

Sodium Hypochlorite

Sodium Hypochlorite is produced adding gaseous Chlorine (CL2) to caustic soda (NaOH). When this is done, Sodium Hypochlorite (NaOCL), water (H2O) and salt (NaCl) are produced according to the following reaction:

Cl2 + 2NaOH + → NaOCl + NaCl + H2O

Chlorine reacts with sodium hydroxide to Sodium Hypochlorite (NaOCl). Sodium Hypochlorite is known as Bleach. Bleach (NaOCL) cannot be combined with acids. When NaOCL comes in contact with acids the hypochlorite becomes instable, causing poisonous gaseous Chlorine (CL2) to escape.

Hypochlorous Acid and Hypochlorite Ion formation

Hypochlorous Acid (HOCL) and Hypochlorite Ion (OCL-) are the by-products of Sodium Hypochlorite (NaOCL) in water (H2O). NaOCL reacts with water (H2O) to Hypochlorous Acid (HOCl) and Hypochlorite Ions (OCl-).

NaOCl + H2O → HOCl + NaOH-

Hypochlorous Acid formation

Hypochlorous Acid (HOCL) is the by-product of gaseous Chlorine (CL2) in Water. Gaseous Chlorine (CL2) reacts with water to Hypochlorous Acid (HOCL).

Cl2 + H2O -> HOCl + H+ + Cl-

Oxygen formation

Depending on the pH value, Hypochlorous Acid (HOCL) expires to Hypochlorite Ions (OCL-).
Cl2 + 2H2O -> HOCl + H3O + Cl-
HOCl + H2O -> H3O+ + OCl-

This falls apart to Chlorine and Oxygen atoms:

OCl- -> Cl- + O

The efficacy of disinfection is determined by the pH.

Disinfection will take place optimally when the pH is between 5 and 7, as then a maximum of HOCL is present.
HOCL reacts faster than OCl- ; HOCL is 80-100% more effective than OCL-. HOCL does not evaporate and does not cause severe corrosion like CL2. CL2 exposed in air can be very explosive and evaporation should be avoided. For this reason, the ideal pH is between 6 and 7, as no CL2 is present.

The level of HOCL will decrease when the pH value is higher than 5. The level of HOCL will decrease when the pH value is lower than 5. With a pH value of 6.5 the level of HOCL is more than 90%, whereas the concentration of OCL- is less than 10%.

Free Available Chlorine

Free Available Chlorine (FAC) is chlorine that is present in the form of Hypochlorous Acid, hypochlorite ions or as dissolved elemental chlorine. FAC includes all chlorine species that are not combined with ammonia (or other nitrogenous compounds) to form chloramines. It is ‘free’ in the sense that it has not yet reacted with anything, and ‘available’ in the sense that it can and will react if needed.

A pH value of 6 to 7 is the most effective and the safest pH-range, due to absence of chlorine gas. Therefore when Free Available Chlorine is mentioned, it is assumed that Free Available Chlorine solely consists of HOCL and OCL-

Free Available Chlorine compounds with regard to pH .Hypochlorous Acid (red) and Hypochlorite Ion (green)

Superiority of Hypochlorous Acid compared to Hypochlorite Ion

Hypochlorous Acid (HOCl, which is electrically neutral) and Hypochlorite Ions (OCl-, electrically negative) will form Free Available Chlorine (FAC) when bound together. This results in disinfection. Both substances have very distinctive behavior.

The cell wall of pathogenic microorganisms is negatively charged by nature. As such, the cell wall only penetrated by the neutral Hypochlorous Acid (HOCL), not by negatively charged Hypochlorite Ion (OCL-).
HOCL can penetrate slime layers, cell walls and protective layers of microorganisms and effectively kills pathogens as a result. The microorganisms will either die or suffer from reproductive failures.

The pH neutral Hypochlorous Acid (HOCL) can penetrate cell walls of pathogenic microorganisms whereas the negatively charged Hypochlorite Ion (OCL-) cannot penetrate cell walls.

Besides the neutrality of HOCL, it is a much more reactive and is a much stronger disinfectant than OCL-, as HOCL is split into hydrochloric acid (HCl) and atom air Oxygen (O). Oxygen is a very powerful disinfectant.

Neutral Electrolyzed water (HOCL) guarantees optimal disinfecting

The disinfecting properties of Chlorine in water are based on the formation and oxidizing power of Oxygen and HOCL. These conditions occur when the pH is between 6 and 7.

Neutral Electrolyzed Water (NEW) produced onsite from a AQUAOX System has a pH of 6.5. At this pH more than 90% of the free available chlorine is HOCL, less than 10% OCL- and no CL2 are formed. The strength of Free Available Chlorine (FAC) in NEW is pre-set to 300+ppm. To make a solution with 300+ppm FAC from commercially available bleach (NaOCL), it is diluted in water (H2O).

The problem with diluting bleach in water is twofold:

1) The volume to dilute bleach is very small. Small differences in the volume of bleach added to water causes significant differences in terms of pH and Free Available Chlorine (FAC).
2) The fact that water has naturally different pH levels, causes that addition of the same volume of bleach still result in a different pH. Although at each dilution 300+ppm FAC can be measured, the pH of the mixture and consequently the amount of active compounds HOCL and OCL- may vary considerably.

Therefore, disinfecting properties using bleach vary whereas the disinfecting properties of NEW are kept stable. As a result NEW may exceed the disinfecting properties of bleach by 300 times.


When producing HOCL by acidifying NaOCL, relatively high prices and possibility of side reactions limit the use of weak organic acids; use of cheaper inorganic acids provokes gaseous chlorine discharge and a raise of toxicity level. Because of it, the method above is only used for water treatment, where residual chlorine concentration values do not exceed 0.5-5mg/l.

Dilution of gaseous chlorine in water to produce HOCL according to equation demands special safety measures and is only used for disinfecting large volumes of water, where active chlorine concentration is below 10-15mg/l. Nowadays all the companies that manufacture gaseous chlorine stopped gaseous chlorine production and started NaOCL manufacture exclusively because of safety considerations.

Neutral Electrolyzed Water onsite produced by AQUAOX Systems is a unique method of non-reagent synthesis of HOCL. We would like to point out once more that the unique quality of the AQUAOX System is the possibility of directed pH regulation in the 6.0-7.0 ranges, while working with solutions of any mineralization, whereas electrolyses of sodium chloride solutions have identical biocidal activity if pH and FAC concentration are equal.

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