The International Ozone Association (IOA) publishes a journal called Ozone Science & Engineering. This is a publication issues 6 times per year with great info on many ozone applications.
Ozone: Science & Engineering (OS&E), Vol. 42, Issue 5 is now available online. This new issue contains articles about a variety of ozone applications including a molecular modeling study examining potential mechanisms of ozone to inactivate SarsCov1 COVID virus, sterilization of medical devices, pesticide residue removal, ozone in food storage, contaminant oxidation, textile treatment, and cyanotoxin oxidation.
Ozone gas can be dissolved into liquid with simple bubble diffusers, similar to what is commonly used in the bottom of a fish aquarium for aeration. This is a simple and cost-effective method to dissolve ozone gas into liquid. As ozone is partially soluble into liquid the ozone gas will transfer into liquid immediately at the interface between the ozone gas bubble surface and the surrounding water.
Diffusers implement a gas permeable membrane that will disperse the gas stream into many smaller ozone gas bubbles in the water. As these ozone gas bubbles naturally rise to the surface of the water that ozone will transfer into the water due to contact between the liquid and gas bubble.
Easy to setup
Low energy – does not require water pumps or elevated water pressures
Simple, reliable operation long-term
Generally the least efficient method of dissolving ozone into liquid
Diffusers can become plugged and may require periodic replacement
Difficult to use in pressurized water flows
Ozone gas is partially soluble into liquid. However, using proper methods and equipment high mass transfer efficiencies can be realized with any method of dissolving ozone into water. Review the tips below for success using an ozone gas bubble diffuser in your ozone application.
Fundamentals of ozone solubility:
Lower temperatures increase the solubility rate of ozone gas into liquid
Higher pressures increase the solubility rate of ozone gas into liquid
Higher ozone gas concentrations increase the solubility rate of ozone gas into liquid
Design considerations for your bubble diffuser and column:
Diffuser micron ratings – smaller is better!
Ozone gas bubble diffusers will be rated in micron size, or resulting bubble size the diffuser will create. The membrane that splits the gas stream into small bubbles will have pore sizes, smaller pores will result in smaller bubbles. This pore size or bubble size is normally referred to in a micron rating.
Micron = micrometer. Equal to 0.001 millimeter, or about 0.000039 inch
Smaller bubbles create more surface area of the gas the ozone is flowing in. Greater surface area will increase the ability of ozone gas to transfer into the liquid. See the example below:
The image above shows the same gas volume (1 ft3) shown in one bubble, 8 identical bubbles, and 512 (8 tall x 8 wide x 8 deep) identical bubbles.
One 1 cubic foot sphere = 4.8 ft2 surface area
Eight 0.125 cubic foot spheres = 1 cubic foot = 1.2 ft2 each = 9.66 ft2 total surface area
Eighty 0.0125 cubic foot spheres = 1 cubic foot = 0.26 ft2 each = 20.8 ft2 total surface area
512 0.001953 cubic foot spheres = 1 cubic foot = 0.07567 each = 38.7 ft2 total surface area
A bubble size ¼ the size (4.8 / 4 = 1.2) results in 8x more bubbles and double the overall surface area.
Relating this to your ozone gas flow. A 25 micron diffeser will create bubble sizes ¼ the size of a diffuser rated for 100 micron therefore creating more than 2x the surface area of gas contacting the water at the same flow-rate of gas flowing into water.
Smaller really is better!
Tank design – skinny is better!
Gas bubbles will naturally rise to the surface of water due to buoyancy. Therefore, the taller your tank, column or ozone tank is the longer your gas bubble will remain in the water increasing the opportunity for the gas to transfer into the liquid.
Taller tanks will also increase the water
pressure at the bottom of the tank where the ozone gas diffuser will likely be placed. Greater water pressure will increase the natural solubility of ozone gas into liquid. For example:
11.33 feet of water = 5 PSI
5 PSI = 34% increase in ozone solubility vs 0 PSI
Increasing your water column by 11.33 feet will increase your solubility of ozone, or your mas potential ppm of ozone in water by 34%.
1 ppm becomes 1.34 ppm with no other changes.
A great example of separate columns is shown in the image and dimensions below. Both columns are 3 liters in volume, with a change in diameter from 2” to 4” the height is increased from 12” to 58”
If you have the opportunity when desiring your tank or reactor, choose the smallest diameter possible.
Skinny really is better!
Counter Current Flow
Ozone contacting basins can be designed with counter-current flow, where the water flows counter-current to the gas bubbles. While gas bubbles will naturally rise to the surface of the liquid due to buoyancy liquid can be forced into the path of the gas bubble to create additional turbulence. The diagram below shows a simple contactor basin design using baffles to create counter-current and con-current flows of ozone gas to liquid
This same technique can be applied to any column in flowing water using piping water flowing down a column that ozone gas is rising within. Consider this simple technique when designing your tank or piping system
Ozone dosage =the amount of ozone applied to the water
Dissolved ozone =the amount of ozone measured in the water
Ozone dosage into water does not equal dissolved ozone in water. Ozone is generated as gas and must be dissolved into water in many applications. As ozone is only partially soluble in water mechanical mixing equipment is necessary to dissolve ozone into water efficiently. There are no systems that will achieve 100% mass transfer of ozone gas into water, therefore the dissolved ozone levels will always be lower than the applied ozone, or ozone dosage rate.
Final measured dissolved ozone levels in water will be affected by water quality contamination, water temperature, and the efficiency of your mechanical mixing equipment used to dissolve ozone into water.
To achieve a specific, targeted dissolved ozone level the oxidizable compounds in the water must be overcome along with any other ozone scavenging conditions, also keep in mind the ozone half-life may come into play depending upon the duration of time used to achieve your target dissolved ozone level.
The quantity of ozone you attempt to put into the water will always exceed the amount of ozone actually absorbed into the solution.
Due to the low solubility rate of ozone gas into a liquid and due to system inefficiencies, a portion of the ozone off-gases without being absorbed into the water. This off-gassed ozone must then be vented outside or destroyed with an ozone destruct unit.
The ratio of ozone gas dosage to the final dissolved level is commonly referred to as the mass transfer rate. This refers to the amount of ozone gas that was measured as dissolved vs the ozone dosage rate. This is commonly referred to as a percentage. Such as a 90% mass transfer rate of ozone would indicate that 90% of the ozone dosage, 1ppm for example, would result in 0.9 ppm of ozone measured in water.
Different methods of ozone injection will achieve different dissolved ozone levels into water due to different efficiencies and mass transfer of ozone into water. A few examples of these options are shown in the images below:
There has been a great deal of interest recently in the use of ozone to purify ethanol products to achieve a higher grade of ethanol or alcohol products. We have performed a great deal of bench-testing and pilot testing with companies to assist and achieve these goals. We have found that ozone is very effective at reducing certain undesirable compounds from ethanol along with improving the color and odor of the ethanol.
We thought it might be helpful to assist with promoting this application and the original research that brought this application to light. Right here in Iowa, at the University of Iowa research was done on the purification of Ethanol. See link below and summary for details:
Purification and Quality Enhancement of Fuel Ethanol to Produce Industrial Alcohols with Ozonation and Activated Carbon
The total ethanol production capacity in the US just passed 6 billion gals/year. The production process of ethanol from corn includes corn milling, cooking, enzymatic starch conversion, fermentation and distillation.Food-grade alcohol production requires more care and undergoes costly additional purification to remove volatile organic impurities. These impurities could be of health concern and/or impart unpleasant tastes and odors to beverage alcohol. Multiple distillation steps are usually employed. The additional purification of ethanol to obtain food-grade alcohol adds at least $0.30 per gallon in processing costs. In this research, we tested a novel approach to purify fuel grade ethanol to pharmaceutical and beverage grade. The cost of the proposed treatment process is expected to be less than $0.01 per gallon. We have shown that ozone can oxidize a number of undesirable compounds in ethanol. Furthermore, it was demonstrated that adsorption ongranular activated carbon can remove many of the ozonolysis byproducts. All chemical and sensory analyses were completed using solid phase microextraction (SPME) to extract volatile organic compounds from ethanol samples and a multidimensional GC-MS-Olfactometry system to identify impurities and the impact of odorous compounds. To date, we confirmed a significant reduction of some impurities with ozone alone.Ozone and granular activated carbon are very effective in purifying fuel ethanol. Also, we designed a pure ozone generating setup. This setup can provide further purification efficiency on this research. This technology will help the corn milling and ethanol industry and provide an opportunity for improving the long-term sustainability of corn growing and processing.
If you have any questions on this application, or would like help performing your own testing, please let us know. We would be glad to help.
Researchers at Yale School of Medicine and collaborators have successfully used ozone to disinfect the respirator masks used by healthcare workers to protect against respiratory diseases such as coronavirus disease 2019 (COVID-19).
The development could be used to address a shortage in the availability of this critical piece of personal protective equipment, caused by the COVID-19 crisis.
The authors say that, to their knowledge, their study is the first to report successful disinfection of the masks with ozone and the first to identify the conditions necessary to do so, without damaging mask function.
A preprint version of the paper is available on the server medRxiv*, while the article undergoes peer review.
Supplies of the masks are dwindling
Supplies of the NIOSH-certified N95 filtering facepiece respirators (commonly shortened to“N95 respirators”) have dwindled with the increasing strain placed on healthcare systems due to the COVID-19 pandemic.
This had prompted front-line medical workers to resort to reusing the respirators and experimenting with their own methods of disinfection, which some researchers have described as generally ineffective and damaging to filter performance.
What does the CDC say?
The Centers for Disease Control (CDC) has recognized that the reuse of personal protective equipment such as N95 respirators may be necessary to protect healthcare personnel and to lower the risk of transmitting infection in the workplace.
However, the organization says four essential points must be addressed when considering potential ways to achieve this. The method must be effective at killing the organisms being targeted; must not degrade the function of the equipment; must not introduce new risks to healthcare workers and must be practical in the setting of emergency pandemics such as COVID-19, where resources may be too limited to ensure adequate supplies of the equipment.
Some organizations have described potential protocols, including disinfection with dry heat or using vaporized hydrogen peroxide (VHP) and UV-C light.
Ozone is an appealing option
However, Manning and colleagues were interested in the possibility of disinfecting the respirators with ozone as an alternative for healthcare personnel who may not have access to VHP or other disinfection devices.
The team says that not only is ozone attractive as a potential disinfector because it is a strong oxidant that can deactivate viruses, but it can be generated from air, can quickly be destroyed, and does not leave any residue.
Now, the researchers have tested using ozone to kill Pseudomonas aeruginosa on three types of N95 respirators, namely the 3M 1860, 3M 1870, and 3M 8000.
They point out that P. aeruginosais a bacterium that the CDC has previously referred to as more difficult to kill than viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The ozone disinfector the team used
The device comprised an airtight chamber than could generate ozone from ambient air at a concentration of 500 parts per million (ppm). This ozone UV analyzer could accurately determine ozone levels in the chamber and an ozone destruction unit.
The team reports that exposing the respirator to ozone at a concentration of 400ppm at a humidity of 80% over two hours successfully killed bacteria on all three types of respirators.
Furthermore, exposure to ozone at this concentration with a relative humidity of 75-90% at room temperature did not degrade the filtration capability of the 1860 and 1870 type respirators for up to 10 cycles of two-hour treatments.
A practical way to decontaminate the respirators
Manning and colleagues advise that ozone disinfection using the small devices could serve as an effective way to decontaminate N95 respirators, especially in rural areas and in cases where healthcare workers and institutions have no access to large-scale disinfection facilities.
How much ozone do I need to destroy pathogens? The question is similar to asking “how much heat do I need to cook an egg?” This question is more easily answered when put in terms of time and temperature. Five minutes in boiling water can produce a softboiled egg. Ten minutes in boiling water will produce a hardboiled egg. The ozone question can be answered in a similar way: About three seconds of exposure in 0.5 ppm ozonated water can destroy 99% of E.coli bacteria. Six seconds of exposure in 0.5 ppm ozonated water can destroy 99.99%. Time and ozone concentration are the two main factors needed to how much ozone is needed.
If the ozone concentration is lower, it takes longer to destroy the bacteria. In a similar way, it takes longer to cook meat when the temperature is lower. A higher temperature cooks faster, but can also have undesirable side effects. Higher concentrations of ozone destroy pathogens more quickly, but also can have undesirable side effects. When cooking a piece of meat, the goal is to reach a particular internal temperature. In the disinfection industry, the goal is a particular Contact Time or CT value. The CT value is often given in units of mg/min -1 which is equivalent to ppm x time in minutes.
The CT disinfection value is a number that tells you when a particular type of pathogen has been “cooked” or inactivated to the desired level. The numbers come from a CT value chart. For example, the chart here gives a set of CT values for inactivating cryptosporidium. The CT value needed to inactivate 99% (2 Log) of the cryptosporidium at 15 degrees Celsius is 12. If my ozone concentration in the water is 2ppm, then I need to maintain that level of ozone in the water for 6 minutes. Ozone concentration (2ppm) x Time (6 min) = 12.
Another chart gives the CT values for inactivating 99% of a variety of different pathogens at 5 degrees Celsius with four different kinds of disinfectants. E.coli bacteria have a very low CT value of 0.02 with ozone. A 0.5 ppm concentration of ozone requires only 0.04 minutes (2.4 seconds) of contact time to inactivate 99% of E.coli. Chlorine is also an oxidant, but it is not as strong an oxidant as ozone. The chart shows the CT values of three different forms of chlorine. All of them have a higher CT value and therefore require a higher concentration or a longer contact time for the same level of disinfection.
When you start looking at CT charts, you will notice that water temperature has a significant impact on CT values. In cold water, ozone does not react as quickly as it does in warmer water. Keep in mind, however, that the ozone level in warmer water declines more quickly as it oxidizes things. As the ozonated water moves through a pipe or reaction chamber, it may begin at 4 ppm, and end at 2 ppm. (see charts at end of post)
Temperature is not the only factor to consider. Minerals or other organic compounds in the water will be oxidized by the ozone and reduce the concentration. Contact time may also vary depending on water demand. A CT value table provides a solid starting point, but all the other factors that affect ozone and limit contact of ozone with a particular organism must be considered when determining how much ozone will be needed.
A five gallon bucket and a stopwatch will give a fairly good measurement of your water flow in gallons per minute. Ozonated water flowing at 5 gallons per minute through a 10 gallon tank will provide about 2 minutes of contact time. Dissolved ozone test kits are a low cost method of measuring the ozone levels in water. Dissolved ozone sensors that provide a continuous digital reading of dissolved ozone levels are much more expensive. Measuring the Oxidation Reduction Potential (ORP) is a cheaper option, but does not give a direct ppm measurement. However, some sampling with a test kit can provide a fairly accurate correlation chart (see blog post) of ORP and dissolved ozone levels in your water.
Related blog posts and links to products. https://www.oxidationtech.com/blog/measure-ozone-in-water-with-orp/ https://www.oxidationtech.com/blog/e-coli-o157h7-reduction-with-ozone/ https://www.oxidationtech.com/av88-ozone.html
Dissolved ozone test kits https://www.oxidationtech.com/products/ozone-monitors/dissolved-meters/k-7404.html https://www.oxidationtech.com/products/ozone-monitors/dissolved-meters/i-2022.html https://www.oxidationtech.com/products/ozone-monitors/dissolved-meters/i-2019.html
Another great paper has been released for the use of ozone in the medical industry. See below, or click link HERE for original paper.
Wearable and Flexible Ozone Generating System for Treatment of Infected Dermal Wounds
Wound-associated infections are a significant and rising health concern throughout the world owing to aging population, prevalence of diabetes, and obesity. In addition, the rapid increase of life-threatening antibiotic resistant infections has resulted in challenging wound complications with limited choices of effective therapeutics. Recently, topical ozone therapy has shown to be a promising alternative approach for treatment of non-healing and infected wounds by providing strong antibacterial properties while stimulating the local tissue repair and regeneration. However, utilization of ozone as a treatment for infected wounds has been challenging thus far due to the need for large equipment usable only in contained, clinical settings. This work reports on the development of a portable topical ozone therapy system comprised of a flexible and disposable semipermeable dressing connected to a portable and reusable ozone-generating unit via a flexible tube. The dressing consists of a multilayered structure with gradient porosities to achieve uniform ozone distribution. The effective bactericidal properties of the ozone delivery platform were confirmed with two of the most commonly pathogenic bacteria found in wound infections, Pseudomonas aeruginosa and Staphylococcus epidermidis. Furthermore, cytotoxicity tests with human fibroblasts cells indicated no adverse effects on human cells.
Skin and soft tissue infections (SSTIs) are a major health and financial burden for millions of people worldwide. In 2016, SSTIs comprised 3.5% of all emergency room visits (Niska et al., 2016). Furthermore, the average cost of a hospital visit resulting from an SSTI is about $8,000 (SSTI, 2018). These numbers are only expected to rise in the years to come due to the aging population and the increasing prevalence of diabetes associate non-healing wounds and bedsores. To complicate the issue even further, many of these infections can be caused by bacteria that are resistant to common forms of treatment. Infections caused by drug-resistance bacteria have become a significant problem and now affecting over 2 million people in the US each year (Centers for Disease Control and Prevention, 2018). For instance, methicillin-resistant Staphylococcus aurous (MRSA), has been noted to kill more Americans every year than HIV/AIDS, emphysema, or homicide (Federal Bureau of Investigation, 2017; CDC, 2018; Kourtis et al., 2019; Lei et al., 2019). This alarming decrease in antibiotic efficacy has been brought on by a number of factors, but a primary culprit is the commonality of antibiotics usage in society today, especially for inappropriate or unnecessary indications (Ventola, 2015). Simultaneously, major drug companies have reduced the number of antibiotics they are developing. This is mainly due to a significantly reduced return on investment for antibiotic research and development compared to the drugs for chronic conditions such as diabetes, heart disease, and cancer (Ventola, 2015).
Recently, there has been increased effort toward the development of alternative (non-antibiotic) materials and treatments for bacterial infections (Kowalski et al., 1998; Laroussi et al., 2000; Fridman et al., 2005; Fontes et al., 2012; Guan et al., 2013; Korshed et al., 2016). For example, metallic nanoparticles of noble metals such as silver have shown to exhibit antimicrobial properties for a wide range of bacteria and utilized in various advanced wound dressings (Maneerung et al., 2008; Rujitanaroj et al., 2008). Despite having effective antimicrobial activity, many studies have also shown that silver nanoparticles are cytotoxic, and cause damage to cellular components such as DNA and cellular membrane (Korshed et al., 2016). Other materials include polyvinyl-pyrrolidone, a non-ionic synthetic polymer, which allows for gradual release of free iodine with antimicrobial effects. Yet, povidone-iodine and its different complex forms have also been shown to delay wound healing by inhibiting fibroblast aggregation and leukocyte migration (Álvarez-Paino et al., 2017). Free radical and ionized gasses generated by cold atmospheric plasma (CAP) have also shown to be an effective alternative therapeutic tools, providing both antimicrobial properties and help promoting wound healing, and tissue regeneration (through activation of growth factors and stimulation of angiogenesis) (Laroussi et al., 2000; Fridman et al., 2005). Although a promising approach, only a few devices and systems using CAP for wound treatment have been adopted by the patients or their caregivers. One major impediment of their widespread adoption is the system cost and complexity. These devices (e.g., Microplaster from Adtech Ltd) use plasma gun/torch that require high voltages, carrier gas (typically argon) and need to be operated by trained personnel in an outpatient setting. Similarly, smart wound dressings have been developed to help increase wound healing through delivery and sensing of factors such as oxygen, as well as drug delivery and providing optimal wound healing conditions (Gupta et al., 2010; Mostafalu et al., 2015; Ziaie et al., 2018).
Antibiotic resistant infections are a growing public health concern. A promising alternative to antibiotic therapy is utilizing the antimicrobial properties of topical ozone treatments. Developing a portable system designed to apply ozone to a targeted area will increase the options patients have in fighting infections that may otherwise be difficult to treat. In this work, we developed an ozone-releasing wound dressing consist of a disposable gas permeable hydrophobic patch with a reusable and portable ozone-generating unit. The patch incorporated a hydrophobic and highly ozone permeable outer layer and an inner dispersion layer for increased gas distribution uniformity. The antimicrobial effects of the system were tested against common antibiotic resistant strains of bacteria. The results indicated complete elimination of P. aeruginosa and significant reduction in the number of S. epidermidis colonies after 6 h of exposure. These tests also showed a high level of biocompatibility (low cytotoxicity) with human fibroblast cells during the same duration ozone treatment. The described patch is a promising tool in the management of chronic infected wounds.