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This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane. A companion article, DRINKING WATER - EMERGENCY SOURCES,describes possible sources of drinking water that may be useful in emergency conditions.

Flood Response Checklist lists key actions you should take after building flooding to minimize mold damage, and includes some safety warnings. Before entering a building that has been affected by a disaster such as fire, earthquake, or flood, See BUILDING ENTRY PROCEDURE for some safety warnings for occupants, building owners, or volunteers who may find themselves indoors in a disaster area and without immediate assistance from rescue workers or other experts. For explanation of the types of contaminants found in water and how they are removed in residential water systems, see WATER TESTS, CONTAMINANTS, TREATMENT.

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How to Treat or Purify Water to Sanitize it For Drinking

Beware that most advice about purifying water, including the tips we have collected below, address biological contaminants in water, such as bacteria.

Health Warnings about Effective Drinking Water Purification

• Chemical contaminants: If your water supply has become contaminated by pesticides, heavy metals, or other chemicals, disinfecting the water will not correct those unsafe conditions.
• Protozoan contaminants: Chlorine and iodine are good disinfectants against bacterial contamination (probably among the most common water contaminants) but studies have shown that these are not effective against certain contaminants in water such as toxic chemicals, Cryptosporidia (Cryptosporidium parvum) , and Giardia.
• Filtration and boiling are additional steps that can address these microorganisms. Activated charcoal can remove some chemical contaminants but has limited life and capacity.

List of Principal Methods Used to Purify Drinking Water when Camping or in an Emergency

Each of the water purification methods listed below includes a link to more in-depth information.

• Boiling water to disinfect it: boil the water to make it suitable for drinking.
• Bleach for disinfecting drinking water: Use chlorine (bleach, sodium hypochlorite) to purify the water. (see warnings just above). Permanent well water chlorination systems are discussed at CHLORINATORS & CHARCOAL FILTERS.
• Chlorination of drinking water: where electrical power and water pressure are present and the equipment is already installed, a chlorinator or water chlorine injection treatment system, usually combined with a charcoal filter for water treatment may be functional. See CHLORINATORS & CHARCOAL FILTERS for details.
• Colloidal silver water filters: Silver ceramic water filters are discussed briefly at Water Filter Selection. Silver ceramic water filters are ceramic water filters which have been treated with colloidal silver - a step which increases filter effectiveness by killing bacteria in water passing through the system. Ceramic water filters (which can be effective if properly used) should not be confused with attempts to "purify" water by adding unreliably formulated colloidal silver products to drinking water. Wikipedia on colloidal silver is at our reference list below and from which we quote/paraphrase below.
  
  A ceramic water filtration system coated with silver particles was created by Ron Rivera of Potters for Peace and used in developing countries for water disinfection. - Wikipedia. An investigation into the effectiveness of this silver-coated ceramic water filter was completed in 2001. That study showed that the silver-treated ceramic filter removed 98-100% of the indicator bacteria present in the source water. The filter does not remove arsenic (and probably not other similar chemicals), and the filter is unreliable for removal of pesticides or VOCs.
• Colloidal silver as a water disinfectant: Electrolytically dissolved silver has been used as a water disinfecting agent including in drinking water supplies of the Russian Mir orbital space station and the International Space Station. The World Health Organization includes silver in a colloidal state produced by electrolysis of silver electrodes in water, and colloidal silver in water filters as two of a number of water disinfection methods specified to provide safe drinking water in developing countries.
  
  However, simply using colloidal silver as an addition to drinking water can be an unreliable and unsanitary "... water treatment method according to Quackwatch and its use can lead to argyria. Colloidal silver is a suspension of submicroscopic metallic silver particles in a colloidal base. Long-term use of silver preparations can lead to argyria, a condition in which silver salts deposit in the skin, eyes, and internal organs, and the skin turns ashen-gray. ... The official drug guidebooks (United States Pharmacopeia and National Formulary) have not listed colloidal silver products since 1975.
  
  

  In August 1999, the U.S. Food and Drug Administration (FDA) banned colloidal silver sellers from claiming any therapeutic or preventive value for the product, noting that colloidal silver was being marketed for numerous diseases without evidence of safety or effectiveness. The product now has the status of a dietary supplement in the US; it can be promoted with general "structure-function" claims, but cannot be marketed as preventing or treating any illness. Following this ruling, the FDA has issued numerous warnings to Internet sites which have continued to promote colloidal silver as an antibiotic or for other medical purposes. Original source, Wikipedia, includes citations in support of these statements.

  In 2002, the Australian Therapeutic Goods Administration (TGA) found that there were no legitimate medical uses for colloidal silver and no evidence to support its marketing claims. Given the associated safety risks, the TGA concluded that "efforts should be made to curb the illegal availability of colloidal silver products, which is a significant public health issue."[26]

• Giardia in Drinking Water - a review of the health hazards & typical equipment costs for portable and whole house water treatment to remove Giardia cysts from drinking water
• Iodine to disinfect drinking water: Use Iodine tablets or a liquid tincture of iodine to purify the water for emergency use (see warnings just above)
• Hydrogen peroxide to disinfect drinking water may be used (maybe) to purify water for emergency drinking use. [The concentration and exposure time data are still needed for this application.]
• Water purifying filters: Use a filter designed for water purification, particularly ceramic filters and silver-ceramic filters. See WATER FILTERS for a separate discussion of home water filters used for sediment, odors, etc.
• Use a water purifying pump such as models sold by camping equipment suppliers to purify the water - typically these pumps use a ceramic or other filter
• Use a water distiller such as a home or portable distillation unit (our photo just above/left shows a Sears® Kenmore home water distiller) (You'll need electrical power or a source of heat to distill water). This device processes about one gallon of water per cycle. We have been using this Sears Kenmore water distiller, model 5000 for more than fifteen years without a hitch. A disposable charcoal post-distillation filter is available for use in the drip spout of the unit - a potential source of contamination if it is not changed occasionally.
• Reverse osmosis to purify drinking water: use a Reverse osmosis water filtration system if water pressure is available or if a portable R.O. system is available. See REVERSE OSMOSIS WATER TREATMENT for details. RO treatment systems may work where there is no electrical power provided that you have water pressure, such as in some municipal water situations.
• UV Lights to purify drinking water - ultra violet light used for water sterilization - see UV -ULTRAVIOLET LIGHT TREATMENT
• Vinegar to wash vegetables is sometimes used as a vegetable wash and may be effective against some microorganisms in water - we have not yet found authoritative data on this application.
• Mixed oxidants electrochemically generated from brine have been used for water disinfection
• Halogenated resins have been used for water disinfection
• Home Made & Expedient Water Sterilization Methods: Matthew Stein describes a variety of home-made, expedient, and partly effective water filters and water treatment methods in When Technology Fails. With plastic and a few sticks you can build a solar water sterilizer (solar water disinfection or SODIS systems).
  
  Stein also explains that slow sand filters have been used for partially cleaning and treating water for a very long time. A crude home made charcoal filter will remove some odors, bad tastes, organic toxic chemicals, and radioactive fallout. Mr. Stein also describes sari water filters used in Bangladesh after flooding, but includes a critical warning that filtering water through cloth is by no means really safe.
  
  Our favorite of his suggestions is using a plant to form a water collector and filter system, an idea which reminds us of native Americans who knew how to obtain water from desert barrel cactus. We enjoyed this book and provide this purchase link for it.

Basic water purification procedures that can be used in an emergency are described just below. If community or private wells are back in operating and providing water, do not assume that the water is sanitary and ok to drink until responsible authorities have said so. Even then, local water pipes in a building may be unsanitary and additional cleaning or disinfection may be needed. See WELL CHLORINATION SHOCKING PROCEDURE and See WATER TESTS, CONTAMINANTS, TREATMENT for advice on using a private well for drinking water.

Links provided just below continue with details about various methods to disinfect or purify emergency drinking water.

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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
FLOODS & MOLD CLEAN/PREVENT A Guide to Dealing with Flood Damage & Mold Prevention &r Cleanup of Flooded Homes
  FIRST PRIORITIES When Responding to a Flooded Building
  BUILDING ENTRY PROCEDURE How to Enter a Building After a Building Flood
  DRINKING WATER - EMERGENCY PURIFICATION How to purify emergency drinking water, how to remove odors
    How to Purify Water
    Boiling Water for Drinking
    Iodine Tablets or Iodine Disinfectant
    Bleach as a Disinfectant for Drinking Water
    Vegetable Disinfection Washes
    Hydrogen Peroxide for Water Disinfection
    Vinegar & Other Disinfectants
    How Much Disinfectant to Use
    Wait Time & Water Temperature
    Filters for Drinking Water Purification
    Giardia in Drinking Water
  DRINKING WATER - EMERGENCY SOURCES Where to find drinking water in an emergency
  ELECTRICAL SAFETY for Flood Damage Inspectors
  FLOOD DAMAGE TO FOUNDATIONS
  FLOOD RESPONSE CHECKLIST Checklist of Key Steps to Minimize Mold Damage After a Building Flood
  INEFFECTIVE MOLD PRODUCTS Ineffective Mold Products and Procedures to Avoid in Mold Cleanup/Prevention
  FURTHER STEPS PREVENT MOLD Further Steps to Avoid Mold Damage After a Building Flood
  WHEN TO STOP LOOKING FOR MOLD after Flooding: When is a Mold Cleanup Job Complete?
  GENERAL MOLD PREVENTION Preventing Future Mold After a Flooded Building Cleanup
  FLOOD DAMAGE RFERENCES References on Mold Prevention and Flood Damage
  FLOOD VENTS How to Use Flood Vents for Structural Protection from Flooding - Flood Venting in Foundations and Enclosures Below Design Flood Elevation
  SEPTIC SYSTEMS & FLOODS What to Do after a Flood - Septic Flood Response, Safety, Health, Maintenance, Repair Advice
  SEWAGE CONTAMINATION IN BUILDINGS how to detect and respond to sewage backups
  SEWAGE PATHOGENS in SEPTIC SLUDGE what are the contaminants in sewage
  Wind Damage to Roofs how to assess and identify wind damage to roofs
PLUMBING TOPICS
WATER TREATMENT EQUIPMENT CHOICES
WELL CHLORINATION SHOCKING PROCEDURE

• Dr. Omar Amin, of the Tempe AZ Parasitology Center, corresponded with Sharon Ross (citation below), one of our readers asking about peroxide: "You can use hydrogen peroxide if you want to but we do not have a track record of percentage dilution". Dr. Amin has done research for the US military and for the CDC.
• Aquamira™ chlorine dioxide water purification kits - see www.aquamira.com/
  "Aquamira Water Treatment Drops were introduced to the Outdoor market in 1999 and have been a favorite of top outdoor guides and instructors ever since. Whether you are camping, traveling in a foreign country or faced with a disaster, our goal is to provide you with safe, pure and good tasting drinking water. Our complete line of water treatment products include leading edge purification and filtration technologies developed and tested in the lab and proven in the field. We offer systems and products that will provide water for a single individual or a village and almost anything in between."
• "Bacteria in Drinking Water" - "Chlorine," Karen Mancl, water quality specialist, Agricultural Engineering, Ohio State University Extension. Mancl explains factors affecting the effectiveness of chlorine in water as a means to destroy bacteria and other microorganisms. OSU reports as follows:

  Chlorine kills bacteria, including disease-causing organisms and the nuisance organism, iron bacteria. However, low levels of chlorine, normally used to disinfect water, are not an effective treatment for giardia cysts. A chlorine level of over 10 mg/1 must be maintained for at least 30 minutes to kill giardia cysts. -- http://ohioline.osu.edu/b795/index.html is the front page of this bulletin.

• Crystal Clear Supply provides portable ceramic water filter purifiers and portable reverse osmosis water treatment equipment - see http://www.crystalclearsupply.com/category_s/7.htm
• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06
• "Do Iodine Water Purification Tablets Provide an Effective Barrier against Cryptosporidium parvum?", Starke, Jeffrey A., Bowman, Dwight D., Labare, Michael, Fogarty, Elizabeth A., and others, Military Medicine, 25 October 2001 [possibly a later version of this article appeared in 2005 -DF]www.amsus.org/military medicine/milmed.htm
• "Drinking Water Safety in Emergencies", University of Minnesota extension, extension.umn.edu/info-u/nutrition/BJ646.html
• EPA: www.epa.gov/ogwdw/mdbp/pdf/alter/chapt_2.pdf provides an article on use of disinfectants for water treatment
• FDA Warning about drinking hydrogen peroxide: www.truthorfiction.com/rumors/h/hydrogen-peroxide.htm This article cites a 2003 entry in Journal of Food and Science on using Hy.Perox to sterilize vegetables, referring to E.coli - NOT to Giardia.
• Giardia exposure limits for drinking water: see www.mass.gov/dep/water/drinking/standards/giardia.htm is the current regulatory exposure limit (your minimum target for sterilization)
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com 11/06
• "Investigation of the Potters for Peace Colloidal Silver Impregnated Ceramic Filter - Report 1: Intrinsic Effectiveness", Daniele S. Lantagne, Alethia Environmental, Allston, MA, Submitted to Jubilee House Community, December 21, 2001, USAID Purchase Order Number: 524-0-00-01-00014-5362. Quoting from one of the conclusion in that study, p. 58:
  Based on the results of the microbiological challenges detailed above, the following conclusions are presented:
  1. Some small bacteria, which are potentially a human health concern, pass through the filter when tested in the laboratory at CIRA-UNAN.
  2. This summary of the historical data clearly shows that many different filter designs over the years remove 98-100 percent of the indicator bacteria present in the source water.
  3. Studies of filters that are two and seven years old indicate that the filters still effectively remove microbiological contaminants. This indicates that the colloidal silver does not ‘wear out’, and that with proper maintenance, there seems to be no need to reapply silver to the filter. Currently, the PFP recommendation is to reapply the colloidal silver once per year to the filter. This does not seem to be necessary based on the laboratory data. However, reapplication of colloidal silver provides a safety factor in the field that should not be removed without more extensive testing.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• Quackwatch comments on colloidal sliver: - This website offers authoritative references, government publications, studies, and more information about use of colloidal silver to treat drinking water.
  Colloidal silver is a suspension of submicroscopic metallic silver particles in a colloidal base. Long-term use of silver preparations can lead to argyria, a condition in which silver salts deposit in the skin, eyes, and internal organs, and the skin turns ashen-gray. Many cases of argyria occurred during the pre-antibiotic era when silver was a common ingredient in nosedrops. When the cause became apparent, doctors stopped recommending their use, and reputable manufacturers stopped producing them. The official drug guidebooks (United States Pharmacopeia and National Formulary) have not listed colloidal silver products since 1975.
• Sharon Ross is a New York City resident, a Riverkeeper member and a MENSA member, who for health reasons has collected references and treatment information about dealing with Giardia cyst contamination in drinking water.
  
• Katadyn™, a Swiss corporation provides water filters, desalinization equipment, and their Micropur chlorine dioxide water purification - see www.katadyn.com/usen/
  "Katadyn offers a wide variety of water filtration and purification products suitable for any need. This allows outdoor enthusiasts and travelers to take along products for making their own drinking water when preparing their trips."
• Patent: This patent application for UV light sterilization www.patentstorm.us/patents/6565803.html Lists good references on water purification for Giardia et als
• Princeton University - www.princeton.edu
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
• Wikipedia on history of use of hydrogen peroxide: Information on Hydrogen peroxide as a sterilant is in Wikipedia at en.wikipedia.org/wiki/Sterilization_(microbiology) HO2 has been used for a long time, including by vaporization for sterilizing freeze dryers.
• Wikipedia on use of colloidal silver 11/03/2009: (quoting / paraphrasing) - see http://en.wikipedia.org/wiki/Colloidal_silver
  True colloidal silver is a liquid suspension of microscopic particles of silver. The commercial alternative medicine product, also referred to as "colloidal silver", includes solutions that contain various concentrations of ionic silver compounds, silver colloids or silver compounds bound to proteins in water. Such products with concentrations of 30 parts per million (ppm) or less are typically manufactured using an electrolysis process, whereas those with higher concentrations of 50 ppm or more are usually silver compounds that have been bound with a protein. These solutions are currently marketed for internal and external use as an alternative medical remedy though there is no scientific evidence to support its effectiveness in vivo.[1] Excessive ingestion of colloidal silver can result in argyria, a condition in which the skin irreversibly turns blue or grey.
• 1-Bromo-3-chloro-5,5-dimethylhydantoin (C5H6BrClN2O2) is produced world-wide and is also used in cleaners and bathroom disinfectants and deodorizers. Here is an example MSDS for this product, provided by Leisure Time

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• Principles and Practice of Disinfection, Preservation and Sterilization (Hardcover)
  by A. D. Russell (Editor), W. B. Hugo (Editor), G. A. J. Ayliffe (Editor), Blackwell Science, 2004. ISBN-10: 1405101997, ISBN-13: 978-1405101998.
  "This superb book is the best of its kind available and one that will undoubtedly be useful, if not essential, to workers in a variety of industries. Thirty-one distinguished specialists deal comprehensively with the subject matter indicated by the title ... The book is produced with care, is very readable with useful selected references at the end of each chapter and an excellent index. It is an essential source book for everyone interested in this field. For pharmacy undergraduates, it will complement the excellent text on pharmaceutical microbiology by two of the present editors."
  The Pharmaceutical Journal: "This is an excellent book. It deals comprehensively and authoritatively with its subject with contributions from 31 distinguished specialists. There is a great deal to interest all those involved in hospital infection ... This book is exceptionally well laid out. There are well chosen references for each chapter and an excellent index. It is highly recommended." The Journal of Hospital Infection.: "The editors and authors must be congratulated for this excellent treatise on nonantibiotic antimicrobial measures in hospitals and industry ... The publication is highly recommended to hospital and research personnel, especially to clinical microbiologists, infection-control and environmental-safety specialists, pharmacists, and dieticians."
  New England Journal of Medicine: City Hospital, Birmingham, UK. Covers the many methods of the elimination or prevention of microbial growth. Provides an historical overview, descriptions of the types of antimicrobial agents, factors affecting efficacy, evaluation methods, and types of resistance. Features sterilization methods, and more. Previous edition: c1999. DNLM: Sterilization--methods.
• Handbook of Disinfectants and Antiseptics, Joseph M. Ascenzi (Editor), CRC, 1995, ISBN-10: 0824795245 ISBN-13: 978-0824795245 "The evaluation of chemical germicides predates the golden age of microbiology..." -
  This well-focused, up-to-date reference details the current medical uses of antiseptics and disinfectants -- particularly in the control of hospital-acquired infections -- presenting methods for evaluating products to obtain regulatory approval and examining chemical, physical, and microbiological properties as well as the toxicology of the most widely used commercial chemicals.
• When Technology Fails, Matthew Stein, Chelsea Green Publisher, 2008,493 pages. ISBN-10: 1933392452 ISBN-13: 978-1933392455, "... how to find and sterilize water in the face of utility failure, as well as practical information for dealing with water-quality issues even when the public tap water is still flowing". Mr. Stein's website is www.whentechfails.com/

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