Document text
STJTJIOXAC
Electrochemically Generated Oxidant Disinfection
in the Use of Individual Water Purification Devices
Technical Information Paper #31-003-0306
PURPOSE
This information paper provides an in-depth review of on-site electrochemically generated
oxidants (EGO) as a disinfectant in potable water supplies. This paper is intended to assist the
reader in evaluating the disinfection capabilities of Individual Water Purification Devices
(IWPDs) using EGO to kill or inactivate disease-causing bacteria, viruses, and protozoan cysts.
REFERENCES
Appendix A contains a list of references.
INTRODUCTION
Background
Understanding the disinfection capabilities of EGO to kill or inactivate disease-causing
microorganisms is important in protecting Soldiers, who are considering using this technology,
from acute health threats posed by these microorganisms. Soldiers deployed beyond traditional
field drinking water supplies must have access to microbiologically safe water. Using IWPDs is
one way to provide microbiologically safe water in these situations. These IWPDs must protect
the Soldier from acute microbial health threats. The U.S. Environmental Protection Agency
(EPA) Guide Standard and Protocol for Testing Microbiological Water Purifiers (reference 1)
provides performance standards by which an IWPD using EGO can be evaluated. The
performance standards are a minimum 6-log reduction/inactivation of bacteria, 4-log
reduction/inactivation of viruses, and 3-log reduction/inactivation of protozoan cysts (typically
Giardia or Cryptosporidium). EGO-using IWPDs meeting these standards are considered
effective against disease causing bacteria, viruses, and protozoan cysts. Some IWPD
manufacturers test their devices using this protocol. This is the best way to evaluate the IWPDs
disinfection capabilities. In the absence of that testing data, this infonnation paper can be used to
gain an understanding of EGO disinfection capabilities and help detennine if an IWPD using
EGO technology could successfully meet the EPA Guide’s minimum performance standards.
General
Electrochemically generated oxidant technology is well established. The technology dates back
to the 1930’s when it was primarily used for the disinfection of swimming pools (reference 2).
Additionally, it is also extensively used in the wastewater and drinking water industries and has
more recently been utilized in the food and agricultural industry (reference 3). Currently, there is
only one Commercial-Off-The-Shelf (COTS) IWPD product using EGO technology.
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1. REPORT DATE
MAR 2006
2. REPORT TYPE
technical
4. TITLE AND SUBTITLE
Electrochemically Generated Oxidant Disinfection in the Use of
Individual Water Purification Devices
6. AUTHOR(S)
Steven Clarke; William Bettin
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
U.S. Army Center for Health Promotion and Preventive Medicine
(USACHPPM),5158 Blackhawk Road, APG,MD, 21010
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
3. DATES COVERED
00-10-2005 to 00-03-2006
5a. CONTRACT NUMBER
5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
5d. PROIECT NUMBER
31-003-0306
5e. TASK NUMBER
5f. WORK UNIT NUMBER
8. PERFORMING ORGANIZATION
REPORT NUMBER
TIP 31-003-0306
10. SPONSOR/MONITOR'S ACRONYM(S)
11. SPONSOR/MONITOR'S REPORT
NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release; distribution unlimited
13. SUPPLEMENTARY NOTES
14. ABSTRACT
Soldiers deployed beyond traditional field drinking water supplies must have access to microbiologically
safe water. Using Individual Water Purification Devices (IWPDs) is one way to provide microbiologically
safe water in these situations. Such IWPDs must protect the Soldier from acute microbial health threats.
Understanding the disinfection capabilities of electrochemically generated oxidants (EGO) to kill or
inactivate disease-causing microorganisms is important in protecting Soldiers, who are considering using
this technology, from acute health threats posed by these microorganisms. This information paper provides
an in-depth review of on-site EGO as a disinfectant in potable water supplies. This paper is intended to
assist the reader in evaluating the disinfection capabilities of IWPDs using EGO to kill or inactivate
disease-causing bacteria, viruses, and protozoan cysts.
15. SUBIECT TERMS
water; drinking water; water treatment; purification; electrolytic disinfection; disinfection; chlorine;
military; IWP (individual water purifier); pathogen removal
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a. REPORT
unclassified
b. ABSTRACT
unclassified
c. THIS PAGE
unclassified
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18. NUMBER
ABSTRACT
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TIP #31-003-0306
ELECTROCHEMICALLY GENERATED OXIDANT CHEMISTRY
Electrochemically Generated Oxidant Production
In the simplest sense, EGO is formed by passing an electric current through a brine (NaCl)
solution to produce oxidants to be used for disinfection. A reaction cell (also called an
electrolytic cell) is where oxidant production occurs. In this cell, filled with a brine solution, are
two electrodes (an anode and a cathode). When a voltage is applied between the electrodes,
oxidant is produced. There are two basic types of EGO generators (reference 4). The most
frequently employed is a two-cell EGO generator in which the anode and cathode are separated
by a cationic membrane. A schematic of a two-cell EGO generator is shown in Figure 1. This
type of EGO generator produces two solutions, one a low pH, high oxidant concentration
solution from the cell containing the anode and a high pH, low oxidant solution from the cell
containing the cathode. The second type of EGO generator contains both the anode and cathode
in a single reaction cell without a cationic membrane. The current COTS IWPD device uses the
single cell EGO generator technology. The oxidant concentration is a function of the voltage
applied between the electrodes and the salt (brine) concentration and quality. Higher currents
and voltage will produce a stronger oxidant solution and food grade salt is preferred to optimize
oxidant generation (references 2 and 5). There are several different EGO generator
manufacturers and their reaction cells and operation requirements all differ. However, in general
a wide range of salt solution and voltages are capable of producing adequate oxidants.
Figure 1. Schematic of a Two-Cell EGO Generator.
Source: Reference 4.
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Oxidant Composition
The primary oxidant fonned using EGO technology is chlorine in the fonn of hypochlorous acid,
HOC1. It has been suggested that oxidants other than chlorine are produced by this technology
such as ozone, chlorine dioxide, hydrogen peroxide, and hydroxyl radicals (reference 6).
However, it has been clearly demonstrated in several studies that chlorine is the primary oxidant
produced and other oxidants have not been measured at detectable levels (references 7-9).
DISINFECTION CAPABILITIES
General
Because the primary oxidant formed is chlorine, disinfection capabilities are similar, if not
identical, to traditional chlorine solutions (i.e., solutions made from sodium hypochlorite,
calcium hypochlorite, and chlorine gas). In the majority of research conducted on EGO
disinfection effectiveness, the impacts of pH, turbidity, and temperature on disinfection
effectiveness are similar to chlorine solutions. The disinfection capabilities of chlorine and the
environmental effects on chlorine are well documented in the U.S. Army Center for Health
Promotion and Preventive Medicine’s (USACHPPM) Chlorine Disinfection Technical
Information Paper and are summarized in Table 1 (reference 10). Because chlorine is the
primary oxidant produced in EGO technology, this reference will provide the reader with a
general understanding of the disinfection effectiveness of the EGO solutions. However, there are
also studies suggesting that EGO technology produces a more effective disinfectant than typical
chlorine solutions under the same conditions. The following discussion provides information
from studies indicating EGO is more effective than typical chlorine solutions.
Disinfection Effectiveness Compared to Chlorine Solutions
Several studies were conducted comparing the disinfection effectiveness of EGO solutions to
typical chlorine solutions. Results were variable. In all cases EGO solutions were as effective or
more effective than a chlorine solution as a biocide. One study showed a sodium hypochlorite
solution was less effective than EGO when tested at the same chlorine concentration and water
quality characteristics (reference 12). This study showed that a sodium hypochlorite solution
needed 2-3 times greater CTs (disinfectant concentration times contact time) to achieve the same
log inactivations as an EGO solution for various bacteria. The CT is the product of disinfectant
concentration (C in mg/L) and contact time (T in min). The CT product is a useful way for
comparing alternative disinfectants and the resistance of various pathogens (reference 21).
Another study showed an EGO solution provided a 3-log Cryptosporidium reduction with CTs of
75 mg-min/L, while a chlorine solution under the same conditions showed no Cryptosporidium
reduction with a CT of 225 mg-min/L (reference 13). In contrast, other studies showed EGO
solutions to be similar in disinfection effectiveness as chlorine. One study showed that chlorine
solutions matched to the properties of EGO solutions were generally as effective as the EGO
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Table 1. Chlorine Disinfection Capabilities (reference 10)
Parameter
Chlorine Disinfection
General Disinfection
Capability
Cysts most resistant. Achieving cyst inactivation will
ensure adequate bacteria and virus inactivation.
Disinfection capability generally follows:
Bacteria > Viruses > Giardia > Cryptosporidium
Bacteria
Effective at reasonable CT values for IWPD use.
Viruses
Effective at reasonable CT values for IWPD use. Use
EPA SWTR CT table for recommended CT values
(reference 11).
Giardia Cysts
Effective at reasonable CT values for IWPD use. Use
EPA SWTR CT tables for recommended CT values
(reference 11).
Cryptosporidium Oocysts
Ineffective, even at high CT values. Not practical for
IWPD use.
Effect of Temperature
Colder water temperatures require higher CT values. Use
a two-fold increase in CT for every 10° C decrease. Use
longer contact time instead of higher dosages to achieve
higher CT values.
Effect of pH
Disinfection efficiency increases with decreasing pH.
Recommend pH less than 8.0 to ensure presence of
hypochlorous acid (HOC1)
Effect of Turbidity
Higher turbidity generally reduces disinfection capability.
Higher dosages may be necessary to ensure the presence
of free chlorine after oxidation of organic matter.
Health Effects
Chlorine, THMs and HAAs have potential health concerns
at elevated levels. IWPD manufacturer-recommended
dosages are not likely to cause adverse health effects for
healthy adults.
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solutions in inactivating various pathogenic bacteria (reference 14). Another study showed
similar inactivation results of pathogenic bacteria between chlorine solutions and EGO solutions
(reference 15). There is also contrasting research between the EGO solutions. In disinfection
studies, the general assumption is that greater CTs result in greater disinfection efficacy (i.e.,
greater log inactivation). However, available research shows EGO solutions with lower chlorine
concentrations (i.e., lower CTs) have resulted in greater log inactivations than EGO solutions
with higher chlorine concentrations (i.e., higher CTs) (references 12 and 13). Available research
indicates variability in effectiveness of EGO solutions compared to chlorine solutions as well as
variability in the effectiveness of similar EGO solutions. Therefore, it is difficult to predict the
disinfection effectiveness of EGO solutions.
Cryptosporidium Oocyst Disinfection
Some manufacturers and vendors market EGO technology’s ability to inactivate
Cryptosporidium as a significant advantage over using typical chlorine solutions. It is well
established that chlorine, as it is used in drinking water treatment, is not effective at inactivating
Cryptosporidium oocysts (reference 10). As previously discussed, some research has shown that
EGO technology can inactivate Cryptosporidium oocysts more effectively (i.e., at lower CTs)
than chlorine solutions. However, due to contrasting research, the variable and unpredictable
disinfection effectiveness of EGO technology suggests that EGO technology should not be relied
upon to consistently provide adequate Cryptosporidium inactivation. Using EGO technology as
an IWPD should be considered to be as effective as chlorine and, therefore, can be effective
against bacteria, viruses, and Giardia cysts. Based on available research, EGO technology has
the potential to be effective against Cryptosporidium oocysts, but because of the disinfection
variability shown by the research, EGO technology should not be considered consistently
effective against Cryptosporidium.
Explanation for Variable Disinfection Effectiveness
Currently, there are no proven explanations for the variable and unpredictable disinfection
effectiveness of EGO technology. The most common hypothesis by authors of studies showing
EGO technology’s variability and unpredictability is that oxidants other than chlorine (e.g.,
ozone, chlorine dioxide, etc.) are generated at variable concentrations and are short-lived
(references 12, 13, and 16). However, it has been thoroughly demonstrated in other studies that
there is no appreciable formation of oxidants other than chlorine (references 7-9).
EGO SOLUTION TOXICITY
Because the primary oxidant generated by EGO technology is chlorine, toxicity concerns are
similar to those for typical chlorine solutions. When added to water, the chlorine in the EGO
solution reacts with natural organic matter to primarily form trihalomethane (THM) and
haloacetic acid (HAA) disinfection by-products (DBPs). Ingestion of chlorine and its
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halogenated by-products, including THMs and HAAs, can result in adverse health effects when
consumed in large enough quantities for long periods of time. The EPA regulates chlorine, total
trihalomethanes (TTHMs) and (the sum of) five HAAs (HAA5) in drinking water systems that
use chlorine for disinfection. The EPA established a maximum residual disinfectant level of
4.0 mg/L for chlorine and maximum contaminant levels of 0.80 and 0.60 mg/L for TTHM and
HAA5 compounds, respectively (reference 17). Potential health effects from ingestion of water
containing free chlorine above 4.0 mg/L include eye, nose and throat irritation, stomach
discomfort, nausea and vomiting. Evidence from animal and human studies suggests that
chlorine and hypochlorite solutions themselves probably do not contribute to the development of
cancer or any toxic effects (reference 18). Potential health effects from ingestion of water with
elevated levels of TTHMs over a long period of time include liver, kidney or central nervous
system problems, as well as the increased risk of cancer. Some studies also show an association
between high levels of TTHMs and an increased risk of early term miscarriage (references 17-
19). Potential health effects from ingestion of water with elevated levels of HAA5 compounds
over a long period of time include the increased risk of cancer (reference 19). Generally, short
tenn exposure to elevated levels THMs and HAAs for healthy adults does not result in adverse
health effects (reference 20). For IWPD use, the risk of illness and death resulting from
exposure to pathogens in drinking water is very much greater than the risks from chlorine and its
DBPs (reference 20). However, manufacturer recommended EGO dosages should be followed
to minimize the potential for DBP fonnation and exposure.
CONCLUSIONS
The use of EGO technology results in the production of primarily a chlorine disinfectant. For
this reason an EGO solution, in general, has the same disinfection effectiveness and experiences
the same impact of environmental effects on disinfection effectiveness as typical chlorine
solutions. Research shows the disinfection effectiveness of EGO solutions to be variable and
unpredictable. In general, the disinfection effectiveness of EGO solutions is as effective, or can
be more effective, than typical chlorine solutions. Using EGO technology as an IWPD should
be considered to be as effective as chlorine and, therefore, can be effective against bacteria,
viruses, and Giardia cysts. Based on available research EGO technology has the potential to
be effective against Cryptosporidium oocysts, but because of the disinfection variability shown
by the research, EGO technology should not be considered consistently effective against
Cryptosporidium. Generally, short tenn exposure to elevated levels of THMs and HAAs for
healthy adults does not result in adverse health effects. For IWPD use, the risk of illness and
death resulting from exposure to pathogens in drinking water is very much greater than the risks
from exposure to chlorine and its DBPs. However, manufacturer recommended EGO dosages
should be followed to minimize the potential for DBP formation and exposure. Table 2 provides
a summary of the disinfection capabilities of EGO Solutions.
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Table 2. Summary of Disinfection Capabilities of EGO Solutions.
Parameter
EGO Solutions
General
As effective or can be more effective than chlorine.
Disinfection capability generally follows:
Bacteria > Viruses > Giardia > Cryptosporidium
Bacteria
Effective
Viruses
Effective
Giardia Cysts
Like chlorine, consider providing additional contact time
beyond IWPD manufacturer recommended CTs.
Cryptosporidium Oocysts
Effectiveness is variable and unpredictable. Considered not
consistently effective...
Effect of Temperature
Like chlorine, colder temperatures can reduce effectiveness.
Higher CTs will ensure for colder temperatures increases
effectiveness.
Effect of pH
Like chlorine, higher pH decreases effectiveness. pH less
than 8.0 ensures presence of the most effective chlorine
species, hypochlorous acid (HOC1).
Effect of Turbidity
Like chlorine, higher turbidity reduces effectiveness. Higher
dosages may be necessary to ensure effectiveness.
PREPARED BY: Steven H. Clarke, Environmental Engineer
DATED: March 2006
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APPENDIX A
REFERENCES
1. U.S. Environmental Protection Agency (EPA), Registration Division Office of Pesticide
Program, Criteria and Standards Division Office of Drinking Water, 1987. Guide Standard and
Protocol for Testing Microbiological Water Purifiers. Washington, D.C.
2. White, G.C., 1999. Handbook of Chlorination and Alternative Disinfectants, Fourth
Edition. John Wiley & Sons, New York, NY.
3. Len, S., et. ah, 2002. Effects of Storage Conditions and pH on Chlorine Loss in
Electrolyzed Oxidizing (EO) Water. Journal of Agricultural and Food Chemistry, 50(1),
209-212.
4. Morita, C., et. ah, 2000. Disinfection potential of electrolyzed solutions containing sodium
chloride at low concentrations. Journal ofVirological Methods, 85, 163-174.
5. U.S. Army Belvoir Research, Development and Engineering Center, 1994. Design,
Fabrication, and Testing of a Laboratory Test Electrolytic Water Disinfection Unit (EWDU):
Addendum Number 2 Results of Reinfection Studies. (Report Number LATA/MX-94/0009).
Prepared by Bradford, W.L. and Baker, F.A., Los Alamos Technical Associates, Inc.
6. Reiff, F.M., 1988. Drinking-Water Improvement in the Americas with Mixed Oxidant
Gases Generated On-Site for Disinfection (MOGGOD). Pan American Health Organization
Bulletin, 22(4), 394-415.
7. Gordon, G., Bolden, R., and Emmert, G., 2002. Measuring Oxidant Species in Electrolyzed
Salt Brine Solutions. Journal of American Water Works Association (AWWA), 94(10), 111-120.
8. Stan, S.D., Woods, J.S., and Daeschel, M.A., 2005. Investigation of the Presence of OH
Radicals in Electrolyzed NaCl Solution by Electron Spin Resonance Spectroscopy. Journal of
Agricultural and Food Chemistry, 53(12), 4901-4905.
9. Stan, S.D. and Daeschel, M.A., 2005. 5,5-Dimethyl-2-pyrrolidone-A-oxyl Fonnation in
Electron Spin Resonance Studies of Electrolyzed NaCl Solution Using 5, 5 -Dimethyl- 1-
pyrrolinc-X-oxide as a Spin Trapping Agent. Journal of Agricultural and Food Chemistry,
53(12), 4906-4910.
10. U.S. Army Center for Health Promotion and Preventive Medicine, 2005. Technical
Information Paper: Chlorine Disinfection in the use of Individual Water Purification Devices,
Aberdeen Proving Ground.
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1 1 . EPA, 1991. Guidance Manual for Compliance with the Filtration and Disinfection
Requirements for Public Water Systems using Surface Water Sources. (Contract No.
68-01-6989). Prepared by Malcolm Pimie, Inc., and HDR Engineering, Inc.
12. Venczel, L.V., Likirdopulos, C.A., Robinson, C.E., and Sobsey, M.D., 2004. Inactivation
of Enteric Microbes in Water by Electro-chemical Oxidant from Brine (NaCl) and Free Chlorine.
Water Science and Technology, 50(1), 141-146.
13. Sobsey, M.D., et. ah, 2000. Inactivation of Cryptosporidium parvum Oocysts and other
Waterborne Microbes by Oxidants Generated Electrochemically from Sodium Chloride from
Portable Pen and Bench Scale Systems. Proceedings from the AWWA Water Quality Technology
Conference.
14. Kim C., Hung Y., and 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, 199-207.
15. Venkitanarayanan K.S., Ezeike G.O., Hung Y., and Doyle M.P., 1999. Efficacy of EO
Water for Inactivating Escherichia coli 0157:H7, Salmonella enteritidis, and Listeria
monocytogenes . Applied and Environmental Microbiology, 65(9), 4276-4279.
16. Venczel L.V., Arrowood M., Hurd M., and Sobsey M.D., 1997. Inactivation of
Cryptosporidium parvum Oocysts and Clostridium perfringens Spores by a Mixed-Oxidant
Disinfectant and by Free Chlorine. Applied and Environmental Microbiology, 63(4), 1598-1601.
17. Title 40, Code of Federal Regulations, Part 141, National Primary Drinking Water
Regulations, 2004.
18. Waller, K., Swan, SH, Hopkins, B., Windham, G., Fenster, L., Schafer, C., Neutra, R.,
1998. A Prospective Study of Spontaneous Abortion: Relation to Amount and Source of
Drinking Water Consumed in Early Pregnancy. Epidemiology 9(2): 126- 133.
19. Federal Register, 2003. National Primary Drinking Water Regulations: Long-Term 2
Enhanced Surface Water Treatment Rule; Proposed Rule. 68(154), 47640-47795.
20. World Health Organization (WHO), Environmental Health Criteria 216, 2000.
Disinfectants and Disinfectant By-products. ISBN 92 4 157216 7. WHO Library
Cataloguing-in-Publication Data.
21. Crittenden, J.C. et ah, 2005. Water Treatment: Principles and Design Second Edition. John
Wiley & Sons, Inc. Hoboken, NJ.
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