A novel method for disinfection and sterilization of air and objects using electrified mist

Student: Helena He
Table: MED1221
Experimentation location: School, Home
Regulated Research (Form 1c): No
Project continuation (Form 7): No

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Abstract:

A novel method of disinfection and sterilization is proposed. It uses charged ozone water mist to disinfect the air by absorbing and killing airborne bacteria or viruses. When the mist is sprayed on objects or human skin with different polarities of static electricity, it can quickly and effectively kill microorganisms and viruses on the surfaces of the object and the skin under the dual action of ozone and continuous micro-discharge. A functional prototype has been designed and produced. Moreover, several experiments were performed to verify the efficiency of this method.

In the first 30 minutes of using the prototype, the gaseous ozone concentration in the indoor air increased, then gradually stabilized. This is because a very small amount of ozone leaks from the prototype. However, this escaped ozone will decompose into oxygen, so it will gradually reach an equilibrium. Note that the ozone value was always below 80 ppb during the 12 hours test. According to the regulations of the International Ozone Association, at a concentration of 100 ppm, people can work for 10 hours. Therefore, the use of this prototype for indoor disinfection is safe.
Air pollutant monitoring experiment shows that the concentration of various pollutants gradually decreases with time (using the prototype). Within 120 minutes, the concentration of PM10 dropped from 35ug/L to 8ug/L, HCHO dropped from 25mg/M3 to 15mg/M3, TVOC dropped from 150mg/M3 to 90mg/M3, and CO dropped from 10 ppm to 6 ppm. This shows that the dust reduction effect of the aerosol and the ability to absorb airborne pollutants are effective. This is related to the static electricity charged by the aerosol particles. Studies21 show that if suspended particles have 50 elementary charges, the collision frequency between suspended particles and water droplets will increase by 30 times. The novel method features a negatively charged mist, in which the water droplets also attract airborne particles, thus having the same effect.

The experiments also show that the ozone concentration in the water can rapidly increase to 0.6 mg/L within 5 minutes and maintain a concentration of 0.9 to 1.1mg/L for at least 5 hours. On the other hand, if the conventional bubbling method is used to dissolve ozone, a pool of no less than 4-5 meters in height is required, and its efficiency is only about 20%. If the jet method (Venturi method) or turbopump technology is used, the equipment structure is complicated, the cost is high, and there is considerable noise. Similarly, if electrolysis is used, special materials are required22. The novel prototype design can ensure that ozone water of sufficient concentration can be quickly produced without the need for large and complex equipment or expensive materials.

According to the test results of the commissioning unit (China National Research Institute of Food and Fermentation Industries), the charged ozone water mist can effectively kill bacteria in 3 minutes. The greatest sterilization rate was 98.2%, the lowest rate was 83.7%, and the average rate is 91.2%. According to the U.S. Environmental Protection Agency (EPA) and the Safety and Health Administration (OSHA)23, only when CT ≥1.6, can microorganisms be effectively killed in water (where C is the concentration of ozone (mg/L), and T is the action time (min)). From the experiment, the ozone concentration reaches only 0.3mg/L when the prototype is turned on for 3 minutes, and the CT value is only 0.9. Thus, the key factor is likely the continuous micro-discharge between the charged water mist particles and the palm of the hand, continuously shocking the microorganisms.

According to the test results of the commissioning unit (Beijing International Medical Inspection and Certification Technology Co., Ltd.), after spraying for 5, 10, 15, and 20 minutes, the average inactivation rate of the H1N1 [flu] virus was 95%. 99%. 99.9% and 99.95%, respectively. Research24 shows when the ozone concentration is 17.82 mg/L for 4 minutes and 4.86 mg/L for 10 minutes, both of which can inactivate the virus tested. Another study25 shows that when the ozone concentration is higher than 60.3mg/m3, the membrane of the coronavirus can be completely eliminated when the usage time exceeds 15 minutes. In the prototype, the ozone concentration is only 1.0 mg/L, but it can still completely inactivate the N1H1 virus in approximately 20 minutes because of the effect of the charged mist. The next step of this study is to study the effect of the mist on microorganisms and viruses in the air, especially the efficiency of the inactivation of respiratory viruses that affect humans.

Bibliography/Citations:

 

  1. WHO. Responding to community spread of COVID-19 Interim guidance 7 March 2020. WHO  file:///C:/Users/USER-PC/Downloads/WHO-COVID-19-Community_Transmission-2020.1-eng.pdf) (Accessed on 12/03/2020)2020.
  2. Deng SQ, Peng HJ. Characteristics of and Public Health Responses to the Coronavirus Disease 2019 Outbreak in China. J Clin Med. Feb 20 2020;9(2).
  3. Ong SWX, Tan YK, Chia PY, et al. Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient. JAMA. Mar 4 2020.
  4. EPA. United States Environmental Protection Agency. EPA’s Registered Antimicrobial Products for Use Against Novel Coronavirus SARS-CoV-2, the Cause of COVID-19. 03/03/2020. https://www.epa.gov/pesticide-registration/list-n-disinfectants-use-against-sars-cov-2 (Accessed 8/03/2020). 2020.
  5. Hudson JB, Sharma M, Petric M. Inactivation of Norovirus by ozone gas in conditions relevant to healthcare. J Hosp Infect. May 2007;66(1):40-45.
  6. Roy D, Wong PK, Engelbrecht RS, Chian ES. Mechanism of enteroviral inactivation by ozone. Appl Environ Microbiol. Mar 1981;41(3):718-723. 
  7. Murray BK, Ohmine S, Tomer DP, et al. Virion disruption by ozone-mediated reactive oxygen species. J Virol Methods. Oct 2008;153(1):74-77. 
  8. Lin YC, Wu SC. Effects of ozone exposure on inactivation of intra- and extracellular enterovirus 71. Antiviral Res. Jul 2006;70(3):147-153. 
  9. Kekez MM, Sattar SA. A new ozone-based method for virus inactivation: preliminary study. Phys Med Biol. Nov 1997;42(11):2027-2039.
  10. OSAHA. Occupational Safety and Health Administration. Occupational Safety and Health Standards. Toxic and Hazardous Substances. 1910.1000 TABLE Z-1  Limits for Air Contaminants. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TABLEZ1 (Accessed 8/03/2020). 2020.
  11. Hulsheger.H. Potel. J, Niemann. E.G., Electric field effects on bacteria and yeast cells, Radiat. Environ. Biophys. 1983, 22, 149-162.
  12. Gottschalk C, Libra JA, Saupe A. Ozonation of Water and Waste Water: A Practical Guide to Understanding Ozone and its Application: ohn Wiley & Sons; 2008. 
  13. Cardis D, Tapp C, DeBrum M, Rice RG. Ozone in the Laundry Industry-Practical Experiences in the United Kingdom. Ozone: Sci. Eng. 2007;29:85-89. 
  14. Shin GA, Sobsey MD. Reduction of Norwalk virus, poliovirus 1, and bacteriophage MS2 by ozone disinfection of water. Appl Environ Microbiol. Jul 2003;69(7):3975-3978. 
  15. Kim JG, Yousef AE, Dave S. Application of ozone for enhancing the microbiological safety and quality of foods: a review. J Food Prot. Sep 1999;62(9):1071-1087. 
  16. Naito S, Takahara H. Ozone Contribution in Food Industry in Japan. Ozone Sci. Eng. 2006;28:425– 429. 
  17. Wolf C, von Gunten U, Kohn T. Kinetics of Inactivation of Waterborne Enteric Viruses by Ozone. Environ Sci Technol. Feb 20 2018;52(4):2170-2177.
  18. Maslennikov OV, Kontorshikova CN, Gribkova IA. Ozone therapy in Practice. Health Manual, Ministry Health Service of The Russian Federation The State Medical Academy Of Nizhny Novgorod, Russia. 
  19. Standard Practices for Determining Microbial Colony Counts from Waters Analyzed by Plating Methods,ASTM D5465 - 16(2020) 
  20. Christian Napoli,Vincenzo Marcotrigiano and Maria Teresa Montagna,Air sampling procedures to evaluate microbial contamination: a comparison between active and passive methods in operating theatres,BMC Public Health. 2012; 12: 594.
  21. China Patent:CN104707732A, Device and method for eliminating fog and haze by charged particles
  22. China patent:CN201580040683.6, Ozone water and method for producing same
  23. Chinese National Standard CJJ122-2017, Technical Specification for Swimming Pool Water Supply and Drainage Engineering
  24. Zhang Jiamin, Zheng Congyi, et al. Ozone water inactivation effect on SARS virus, Chinese Journal of Disinfection Science, 2004, 01
  25. Feng Zuncheng, Zhao Kesheng, Zhang Xidong, Xu Wanqun, Hong Bo et al., Study on the killing effect of ozone on IBV coronavirus on the surface of objects, Journal of Ocean University of China, 2004(6),p125-128.

 


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Research Plan:

 

1. Principles

I envision an aerosol capable of the disinfection of the air, objects, and [potentially] body. The mist is produced using an ultrasonic mister. In order to have any effect on bacteria and germs, this mist has several features, which include: 

  1. The water particles in the mist carry high-voltage static electricity, which facilitates the absorption of airborne pollutants, dust, viruses, or germs.
  2. There is dissolved ozone in the mist particles, which can quickly kill the adsorbed viruses or germs.
  3. As the water particles evaporate, the dissolved ozone completely decomposes into oxygen, which can increase the oxygen concentration in the air without generating ozone harmful to the human body. Furthermore, the mist can increase the air humidity similar to other humidifiers. 
  4. If two mists with different polarities of static electricity are used, they will attract each other and produce a continuous micro-discharge in the air. Similar to thunderstorms, there will be a large number of negative ions generated, which will enhance the efficiency of the disinfection process.
  5. Upon spraying this mist on objects or the skin with the opposite polarity, the water particles will rapidly release charges and deposit on the surface of the object or skin, forming a water film. Continuous discharge and high concentration of ozone in the water film can then kill viruses or germs on the surfaces.
  6. This mist can be safely used for the disinfection of the face, hands, and respiratory tract. but this needs IRB approval. 


The above assumptions are based on a few concepts. First, pulsed electric field sterilization technology similar to food processing utilize a similar method11. The charged mist particles can discharge in the air, on the surface of objects or human skin with electric field strength (10-50kV/cm), pulse width (0-100μs), and pulse frequency (0-2000Hz). This will destroy the microbial cell membranes and membrane protein structures via electric pulse. Second, ozonated water is widely used to reduce viral infectivity through lipid peroxidation and damage to lipid envelope and protein shell12-17. Ozonated water can not only be used for wound disinfection or oral disinfection, but it is especially effective against viruses such as Epstein-Barr virus, papillomavirus, and HIV18.

 

2. Prototype

I plan to purchase an [corona] ozone generator, ultrasonic mister, high-voltage generator modules, a standard humidifier (for a base), and other components. I will also need ozone detectors (gaseous and aqueous), general-purpose electric meters, and other equipment. I will then assemble two prototypes that produce charged mists with different polarities. I will design the prototype according to Figure 1, a schematic diagram of the device. In the figure, “1” is a water tank with an ultrasonic mister. “2” is the mister itself. “3” is a seal that prevents gaseous ozone from escaping. “4” is the corona ozone generator. “5” is the pipe that intakes undissolved (gaseous) ozone from the water reservoir (“recycling” undissolved ozone). “6” is the ozone outlet pipe (into the water reservoir). “7” is a high-voltage electrostatic generator used to negatively charge the water. “8” is the negative high voltage output wire of the electrostatic generator. “9” is the positive high voltage output wire of the electrostatic generator. “10” is a conductive component in the water tank of the atomizer which is connected to the negative high voltage output electrode of the electrostatic generator through a wire.

Figure 2 is a photo of the prototype that I constructed. The cylindrical humidifier in the middle of the photo is the component that produces the mist via an ultrasonic mister. To the left of the humidifier are the ozone generator and air pump. To the right of the atomizer is a high-voltage electrostatic generator. The generator’s [negative] high-voltage output electrode is connected to the water reservoir through a wire. The black conductive film on the surface of the generator will positively charge objects via contact (i.e., When the conductive film is touched by hand, the human body will be charged with positive high voltage static electricity).


Fig. 1. Schematic Diagram of the Prototype

Fig. 1. Schematic Diagram of the Prototype

Fig. 2. Photo of the Prototype

Fig. 2. Photo of the Prototype

3. How the Prototype Works

  1. The ozone generator passes ozone-containing air into the pure/distilled water in the water reservoir. At the same time, the undissolved ozone and air above the water are extracted and sent back to the ozone generator. This cycle repeatedly circulates and replenishes air regularly to gradually increase the ozone concentration in the water. 
  2. The humidifier is specially designed to prevent the ozone above the water tank from being emitted into the surrounding air with the mist. This ensures that the ozone concentration in the air is within a safe range. 
  3. The mister uses a high-frequency oscillation (1.7-2.4MHz) to generate a large amount of water mist. There will then be a fan that blows the mist out of the humidifier.
  4. A high-voltage generator module is used to transform the low voltage from the battery into a positive and negative DC high voltage (from 3kV to 15kV).
  5. The negative high-voltage output end of the high-voltage module is in contact with the ozonated water in the water reservoir. Thus, the mist particles blown out of the water tank all carry a negative electrostatic charge of no less than 3kV.
  6. The positive high-voltage output end of the high-voltage module is in contact with the ozonated water in another water reservoir (in a different humidifier). The mist particles blown out of the water tank all carry a positive electrostatic charge of no less than 3kV, thereby obtaining two differently charged mists.
  7. When the two charged mists (with no less than +/-8kV electrostatic charge) come into contact, the small discharges will eliminate any germs in the ambient air.
  8. Objects can be disinfected via contact with positive static electricity not less than 3kV, and then by applying the mist (negative static electricity) to kill bacteria or viruses on the surface of the object. This process also applies to cleansing human skin. 

4. Experimental Procedure

Before using the prototype, I used an ozone detector (Gravity: I2C Ozone Sensor and Arduino Romeo V1.3 analog circuit) to monitor the ozone concentration in a 5 by 5 by 3 m3 room (room temperature 25oC, humidity 55%). After turning on the prototype for 10, 20, 30, 60 minutes, and 12 hours respectively, detect and record the indoor ozone concentration (control value). I tested other air quality-related parameters (PM2.5, PM10, TVOC, HCHO, CO, and CO2) using an HTO-132 Air Quality Detector (Hytop Innovation and Technology Co., Ltd) to monitor these parameters in a 5 by 5 by 3 m3 room. I recorded the values at times 10, 20, 30, 60, and 120 minutes. 

To test the ozone levels in the water, I turned on the device for 1, 1.5, 2.5, 4, 6, 8, 10, 15, 20, and 300 minutes respectively, then used a test tube to take out 15ml of ozonated water from the water tank. Then, I would add an ozone test reagent and let it stand for 2 minutes. Subsequently, I would compare the color of the water sample card comparison to determine the ozone concentration in the water.

To test the efficiency of my prototype on bacteria on the surface of the hand, I commissioned a professional facility (China National Research Institute of Food and Fermentation Industries CO., LTD.) to conduct the tests using my prototype. 15 volunteers participated in the test. The test used the conventional method of detecting the total number of colonies of bacteria: the left and right hands of the volunteers are sampled, diluted, cultured, and observed to obtain the difference between the total number of colonies in the two hands. Before sampling, the volunteers repeatedly rubbed their hands on a dirty cloth, and then rubbed their hands for 2 minutes to ensure that the number of bacteria on either hand were in roughly equal concentrations. The left hand was sprayed with an ordinary humidifier and then sampled using a sterile cotton swab. The right hand was sprayed with a charged water mist from the prototype for 3 minutes before sampling. Before spraying, the volunteer needs to place his/her left hand on the black conductive film of the high-voltage electrostatic generator (see Figure 2) to let the volunteers have a positive electrostatic charge on their right hands. When the negatively charged ozone water mist is sprayed on the right palm, a continuous micro-discharge is generated between the water mist particles and the palm. 

To test the efficacy of the mist on the flu virus(H1N1), I commissioned a professional organization to perform the following tests using my prototype: H1N1 virus was placed on a 10mm by 10mm stainless steel slide; the slide was then connected to the positive and high voltage (+8KV) output electrode of the high voltage electrostatic generator, and negative high voltage (-8KV) static electricity was sprayed on the surface of the slide. The virus inactivation rate was measured when the time was 5, 10, 15, and 20 minutes, respectively. (Each inactivation rate data is the average of three tests.)

 

 

Questions and Answers

1. What was the major objective of your project and what was your plan to achieve it? 

The main objective of my project is to develop a new, safe method of disinfection and sterilization of bacteria and viruses using only pure water and ozone. The device should be small in size, low in cost, and easy to use. This method can effectively kill germs and viruses carried on the surface of the human body or on objects, and can possibly be used to disinfect the respiratory tract, although this requires IRB approval. It can also be used for disinfection and purification of ambient air. I planned to achieve this objective by first gaining a thorough understanding of how I could design and build a prototype using already existing parts. Then, I purchased the needed materials and used trial-and-error to create a functional prototype. Finally, I also bought the needed testing equipment (ozone sensor and ORP sensor) to ensure that there were safe levels of ozone in the environment and water.

       a. Was that goal the result of any specific situation, experience, or problem you encountered?  

Yes, this project was inspired by the COVID-19 virus, which has caused a large-scale global outbreak and has become a major public health problem. I wanted to create a remedy to the illness (and other similar respiratory infections) that revolved around engineering rather than biology (vaccines). I also wanted to make this solution not tailored to a specific respiratory disease, such as in the case of vaccines and medication. However, when beginning the project, I realized that my idea would also be able to disinfect bacteria and viruses from surfaces, which would also help in the pandemic situation.

       b. Were you trying to solve a problem, answer a question, or test a hypothesis?

 

I was aiming to solve the problem regarding a safe and efficient method of disinfecting bacteria and viruses from surfaces and human skin. 

 

2. What were the major tasks you had to perform in order to complete your project?

I first designed the prototype and reason through how it would function. Second, I found the appropriate materials and equipment to build the prototype without any professional help or machinery. Additionally, I developed plans of how to test whether my design worked as intended (experimental plans) and successfully perform the experiments in a controlled environment. Finally, I analyzed the results of the experiments and searched for (and still am) improvements to the design. 

       a. For teams, describe what each member worked on.

n/a

3. What is new or novel about your project?

My project revolves around finding a method for disinfection and sterilization of bacteria on human skin and other surfaces without the use of any drugs, heavy/complicated machinery, or non-natural chemicals. I took a new approach to the issue--I looked for a solution through engineering (creating a device). The design only requires a source of air and pure/distilled water. Furthermore, my design adopts a new method to quickly and efficiently produce high-concentration ozonated water using a “recycling” technique. The ozonated water particles in the mist are also charged with static electricity, which aids in absorbing dust particles in the air as well as in killing bacteria/viruses. My project also has the potential of disinfecting the respiratory tract (throat/nasal cavities), although this is theoretical and needs approval. 

       a. Is there some aspect of your project's objective, or how you achieved it that you haven't done before?
Yes (stated above).

       b. Is your project's objective, or the way you implemented it, different from anything you have seen?
Yes (stated above).

       c. If you believe your work to be unique in some way, what research have you done to confirm that it is?

There have been uses of very large water reservoirs to fully dissolved ozone in water, but they require large amounts of space and machinery in order to do so. I have not yet seen any implementation of an ozone “cycle” system. Furthermore, there haven’t been many studies on the use of a charged mist directly on human skin; moreover, the disinfectants used in electrostatically charged mists are not used for disinfecting both the human skin as well as inanimate objects/surfaces. 
 

4. What was the most challenging part of completing your project?

The most challenging part of the project was designing and building the prototype. In this process, I faced several problems, especially how to prevent ozone from escaping and entering the air from the mist and how to ensure that the ambient ozone concentration does not exceed the safety standard.

      a. What problems did you encounter, and how did you overcome them?

One of the problems I encountered was regarding the humidifier; simply put, if the humidifier is completely sealed to prevent ozone from leaking out, the internal pressure of the water reservoir will be lower than atmospheric pressure, causing the mist to spray abnormally. To counter this problem, I realized that instead of completely sealing the humidifier, I could simply use ozone-absorbing materials to block the passage of gaseous ozone out of the device. However, this solution has yet to be fully tested. I have also considered piping the opening of the humidifier to the outside atmosphere (blocking ozone entry) and allowing the humidifier to spray the mist normally. 

      b. What did you learn from overcoming these problems?

Through this process, I learned to be more observant of potential issues that may occur. Furthermore, I have learned to find more creative solutions to the problems at hand and addressing the potential solutions to find any other issues that may arise. Essentially, I learned to be more careful in assuming that one solution will always work. 

5. If you were going to do this project again, are there any things you would you do differently the next time?

First, I would apply for an IRB and then cooperate with universities or other research units to conduct clinical comparison experiments on the charged mist treatment of respiratory viruses, in hopes of finding an effective method to kill the COVID-19 virus, prevent infection, and assist in the treatment of infected patients. I would also focus on addressing all the potential issues of the design of the device prior to building it (I had discovered several issues while/after building). 

6. Did working on this project give you any ideas for other projects? 

Yes, I will try to use this method to conduct research on respiratory tract administration. In this project, the medicine will be dissolved in purified water, and the medicine is delivered to the designated part of the respiratory tract through a mist. This goal is achieved by changing the polarity of the human body and the mist.

7. How did COVID-19 affect the completion of your project?

For me, COVID-19 had little impact on the project. I ordered parts online, built prototypes in my basement, and was able to perform most of the experiments. The experiments on microorganisms and viruses were commissioned by professional organizations, and I only needed to send the prototypes to them.