Strong Acidic Water

Functional Waters

Some commercial water ionizers allow you to add sodium chloride (NaCl) to the source water, which increases the conductivity of the water, resulting in functional waters called strong alkaline water (produced at the cathode) and strong acidic water (produced at the anode).1

Strong Acidic Water

Strong acidic water, known as electrolyzed oxidizing water (EOW) in the literature,2 is produced via electrolysis of a NaCl solution at the anode side.3 The resultant product is a solution of hypochlorous acid (HOCl) with a pH less than 2.7 and a positive ORP +1000 mV to +1600 mV.4 This anodic water contains oxidative characteristics due to a variety of chemical species (HOCl, O2, 1O2, etc.)5 The high oxidation-reduction potential (ORP) of EOW is an indicator of its bactericidal effects.  Hypochlorous acid is the primary agent in this water,6 but the other free radical species are also important to its powerful germicidal activity.7 Perhaps this is one of the reasons why EOW is an effective anti-microbial, even with only 20 ppm to 60 ppm of available chlorine (HOCl/OCl-), as opposed to conventional anti-microbials which may contain chlorine at over 200 ppm.  EOW is used for sterilization,8 disinfection,9 and sanitization.10

However, unlike other cleaners it is not a surfactant. Hypochlorous acid is also the main ingredient in bleach,11 although the pH of bleach is about 12, which favors the hypochlorite species.

Differences in pH

Although EOW is generally recognized as having an acidic  pH (less than 2.7), this is not always the case,12 nor does it need to be.13 pH is not as important as is the concentration of HOCl and other oxidizing species.14 There are many devices15 and studies which clearly demonstrate that neutral electrolyzed oxidizing water is just as effective.12-14,16 It may also be preferred as it stores longer.17

EOW History and Medical Approval

EOW was developed in Japan in the late 1980’s as disinfectant water.18 In 1996, the Japanese Ministry of Health, Labor, and Welfare approved EOW-producing machines as medical devices for “hand-washing upon surgery”.19 The following year they were approved for “antiseptic washing and disinfection of endoscopes”.20  However, its actual use in the medical field is not as well-known.21

Effectiveness and Benefits

EOW is effective in killing pathogens,22 bacteria,23 viruses,24 spores25 and other microorganisms.26 Interestingly, it is effective even at relatively low HOCl concentrations.27 EOW is also effective at reducing pesticides on vegetables.28 It also doesn’t appear to exert the same irritation as HOCl to skin29 and other mucous membranes.30


This has made EOW an attractive concept in the food industry,31 dental industry,32 and other industries in need of sterilizing capabilities.32  Electrolysis units for use on large scale are known as bleach generators.34 The use of these devices eliminates the need to ship and store toxic chlorine gas, as well as the weight penalty of shipping hypochlorous (bleach) solutions.

EPA Registration.

Companies have approached the EPA seeking registration, but this is generally difficult because of the design limitations of the machines. In order to receive certification the machines must be able to reliably produce the solutions in a consistent, repeatable manner, which is affected by source water, flow rate, scale build-up, etc.

Caution Regarding Use

If you choose to use EOW in place of conventional chemicals, you must first verify that the machine can produce water that would meet EPA standards, such as a certain HOCl concentration. Some machines have a simple “salt port” or a “saline solution” that is used to generate the HOCl. This can be an effective method; however, its effectiveness can drastically vary from effective to ineffective depending on a number of factors like flow rate, source water, cleanliness of the electrodes, calcium sulfite content in the filter, and even changes in relative elevations of the acid and alkaline hoses. These variables underscore the importance of verifying that the specific procedure used is adequate to produce effective EOW. One cannot simply assume that the EOW produced from these machines will always be effective, as this may result in negative health effects. Moreover, the lower the pH the stronger the chlorine content, but the less effective the killing power. Thus one cannot assume that a strong “chlorine” smell is indicative of an effective EOW solution.


The price for effective EOW-producing units ranges from $200.00 to about  $6,000.00.  The important thing is to verify that the machines can meet the EPA requirements as mentioned above, and that you have verification that your procedure on your source water is an effective method.


References: Click Here

  1. KUMON, K. (1997). What Is Functional Water? Artificial Organs 21, 2-4.
  2. Guentzel, J. L., Liang Lam, K., Callan, M. A., Emmons, S. A., & Dunham, V. L. (2008). Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water. Food Microbiology, 25(1), 36-41.
  3. Sharma, R. R., & Demirci, A. (2003). Treatment of< i> Escherichia coli</i> O157: H7 inoculated alfalfa seeds and sprouts with electrolyzed oxidizing water. International journal of food microbiology, 86(3), 231-237.
  4. Venkitanarayanan, K. S., Ezeike, G. O., Hung, Y. C., & Doyle, M. P. (1999). Efficacy of electrolyzed oxidizing water for inactivating Escherichia coli O157: H7, Salmonella enteritidis, and Listeria monocytogenes. Applied and Environmental Microbiology, 65(9), 4276-4279.
  5. Liao, L. B., Chen, W. M., & Xiao, X. M. (2007). The generation and inactivation mechanism of oxidation–reduction potential of electrolyzed oxidizing water. Journal of Food Engineering, 78(4), 1326-1332.
  6. Kim, C., Hung, Y. C., & Brackett, R. E. (2000). Efficacy of electrolyzed oxidizing (EO) and chemically modified water on different types of foodborne pathogens. International journal of food microbiology, 61(2), 199-207.
  7. Koseki, S., Yoshida, K., Isobe, S., & Itoh, K. (2001). Decontamination of lettuce using acidic electrolyzed water. Journal of Food Protection®, 64(5), 652-658.
  8. Yoshida, Kyoichiro, et al. "Sterilization effect and influence on food surface by acidic electrolyzed water treatment." JOURNAL-JAPANESE SOCIETY OF FOOD SCIENCE AND TECHNOLOGY 48.11 (2001): 827-834.
  9. Koide, S., Takeda, J. I., Shi, J., Shono, H., & Atungulu, G. G. (2009). Disinfection efficacy of slightly acidic electrolyzed water on fresh cut cabbage. Food Control, 20(3), 294-297.
  10. Issa-Zacharia, A., Kamitani, Y., Morita, K., & Iwasaki, K. (2010). Sanitization potency of slightly acidic electrolyzed water against pure cultures of< i> Escherichia coli</i> and< i> Staphylococcus aureus</i>, in comparison with that of other food sanitizers. Food Control, 21(5), 740-745.
  11. Winter, J., Ilbert, M., Graf, P. C. F., Özcelik, D., & Jakob, U. (2008). Bleach activates a redox-regulated chaperone by oxidative protein unfolding. Cell, 135(4), 691-701.
  12. Deza, M. A., Araujo, M., & Garrido, M. J. (2003). Inactivation of Escherichia coli O157: H7, Salmonella enteritidis and Listeria monocytogenes on the surface of tomatoes by neutral electrolyzed water. Letters in Applied Microbiology, 37(6), 482-487.
  13. Guentzel, J. L., Liang Lam, K., Callan, M. A., Emmons, S. A., & Dunham, V. L. (2008). Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water. Food Microbiology, 25(1), 36-41.
  14. Izumi, H. (1999). Electrolyzed Water as a Disinfectant for Fresh?cut Vegetables. Journal of Food Science, 64(3), 536-539.
  16. Cao, W., Zhu, Z. W., Shi, Z. X., Wang, C. Y., & Li, B. M. (2009). Efficiency of slightly acidic electrolyzed water for inactivation of< i> Salmonella enteritidis</i> and its contaminated shell eggs. International Journal of Food Microbiology, 130(2), 88-93.
  17. Cui, X., Shang, Y., Shi, Z., Xin, H., & Cao, W. (2009). Physicochemical properties and bactericidal efficiency of neutral and acidic electrolyzed water under different storage conditions. Journal of Food Engineering, 91(4), 582-586.
  18. Ohm's "basic knowledge of descriptive strongly acidic electrolyzed water" Water Study Group, November 1997. Page 5.
  19. Tsuchiya Katsura, Hotta Kuni-moto chemistry of acidic electrolyzed water , 21 - 30 pages (October 2), 2004, "" Takushoku University of Science and Technology report "9
  20. The Japan Association of Electrolyzed water. Overview 2010. (Language Japanese).
  21. While in Japan doing research, I asked a number of doctors if EOW was used for these purposes. None of them had ever used or seen it used.
  22. Koseki, S., Yoshida, K., Kamitani, Y., & Itoh, K. (2003). Influence of inoculation method, spot inoculation site, and inoculation size on the efficacy of acidic electrolyzed water against pathogens on lettuce. Journal of Food Protection®, 66(11), 2010-2016.
  23. Yang, H., Swem, B. L., & Li, Y. (2003). The Effect of pH on Inactivation of Pathogenic Bacteria on Fresh?cut Lettuce by Dipping Treatment with Electrolyzed Water. Journal of Food Science, 68(3), 1013-1017.
  24. Kasai, H., Ishikawa, A., Hori, Y., Watanabe, K. I., & Yoshimizu, M. (2000). Disinfectant effects of electrolyzed salt water on fish pathogenic bacteria and viruses. Nippon Suisan Gakkaishi, 66(6), 1020-1025.
  25. Park, Y. B., Guo, J. Y., Rahman, S. M. E., Ahn, J., & Oh, D. H. (2009). Synergistic effect of electrolyzed water and citric acid against Bacillus cereus cells and spores on cereal grains. Journal of food science, 74(4), M185-M189.
  26. Park, H., Hung, Y. C., & Brackett, R. E. (2002). Antimicrobial effect of electrolyzed water for inactivating< i> Campylobacter jejuni</i> during poultry washing. International Journal of Food Microbiology, 72(1), 77-83.
  27. Izumi, H. (1999). Electrolyzed Water as a Disinfectant for Fresh?cut Vegetables. Journal of Food Science, 64(3), 536-539.
  28. Hao, J., Liu, H., Chen, T., Zhou, Y., Su, Y. C., & Li, L. (2011). Reduction of Pesticide Residues on Fresh Vegetables with Electrolyzed Water Treatment. Journal of food science, 76(4), C520-C524.
  29. Deza, M. A., Araujo, M., & Garrido, M. J. (2003). Inactivation of Escherichia coli O157: H7, Salmonella enteritidis and Listeria monocytogenes on the surface of tomatoes by neutral electrolyzed water. Letters in Applied Microbiology, 37(6), 482-487.
  30. Lee, Jun Haeng, et al. "Efficacy of electrolyzed acid water in reprocessing patient?used flexible upper endoscopes: Comparison with 2% alkaline glutaraldehyde." Journal of gastroenterology and hepatology 19.8 (2004): 897-903.
  31. Huang, Y. R., Hung, Y. C., Hsu, S. Y., Huang, Y. W., & Hwang, D. F. (2008). Application of electrolyzed water in the food industry. Food Control, 19(4), 329-345.
  32. Lee, S., & Choi, B. (2006). Antibacterial effect of electrolyzed water on oral bacteria. JOURNAL OF MICROBIOLOGY-SEOUL-, 44(4), 417.
  33. AL-HAQ, Muhammad Imran, Junichi SUGIYAMA, and Seiichiro ISOBE. "Applications of electrolyzed water in agriculture & food industries." Food Science and Technology Research 11.2 (2005): 135-150.
  34. Inherently Safer Water Purification": Chemical & Engineering News 2007 87(06) p. 22–23

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