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Here we discuss the types of water purification filters that can be used to sterilize water for drinking purposes. 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.

The good news is that there are types of water filters and water filtration systems that can treat water containing various microbes including bacteria, Giardia, and Cryptosporidium cysts, as we discuss just below.

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Guide to Use of Filters for Drinking Water Purification

The best procedure if you don't know much about the water condition is to filter it before and after it is treated with bleach, chlorine, iodine, or other sterilization methods.

Ceramic water purifying filters for Water Purification Treatment

Purifying filters use materials such as ceramic filters which have extremely fine pores to filter out harmful bacteria and protozoa.

Portable ceramic water filters all include a pump, usually a manual or hand pump, which forces water through a very fine ceramic filter cartridge, delivering a clean, if slow stream of potable drinking water. Some portable ceramic water filters include a container into which water is poured, then pumped out. Other ceramic water filter systems such as a model we used during weeks of rafting down the Colorado River, are intended to deliver a larger quantity of potable water: these models can be inserted into a larger container of water. The hand pump draws water out of the container, through the filter, and then delivers it out of a spout or tube into a clean container for drinking or other uses.

Examples of portable ceramic water filters include the Katadyn® ceramic water filter, Hiker Pro Micro Filter (also from Katadyn), and ExsStream ceramic water filter.

In the event that the municipal water supply system is working after a hurricane, flood, or other disaster, companies like Katadyn also produce water filters that can be attached to a faucet and are operated by system water pressure.

Doulton® is a company in the U.K. with branches in the U.S. that produces a wide range of ceramic water filtration equipment including point of use filters (POU filters) and filters that can operate by gravity rather than requiring a pump. A gravity operated ceramic water filter would be an effective means of sanitizing water from a rooftop water cistern.

Small portable water filters are produced by Pure Water 2Go®, and MSR MiniWorks® Water Filter. Small and larger capacity portable ceramic water filters are available from many sources including camping equipment suppliers and water treatment equipment suppliers such as Crystal Clear Supply.

Charcoal Filters for Water Purification

Charcoal water filters are often used as a step in water treatment systems, combined with a chlorination system. A standalone charcoal filter for portable temporary water purification risks becoming contaminated with bacteria. See WATER FILTERS for details of that device.

Magnetic Water Purifiers?

Magnetic water filters and purifiers: are junk science and are not a reliable means of assuring safe drinking water.

Paper or Polypropylene Water Filter Cartridges - Emergency Use Suggestions

Paper or Polypropylene Cartridge type water filters (shown at page top): Our page top photo of Sears Kenmore® water filter cartridges shows how not to try to "purify" drinking water. This propylene filter cartridge is designed for use in a residential water filter canister to remove sediment, silt, rust, or iron particles - see WATER FILTERS for details of that device. In fact, Sears® includes a notice on the package "Warning: do not use [cartridge water filters of this type] where water is microbiologically unsafe or with water of unknown quality".

Paper, charcoal, or other water filter cartridges can be used in an emergency, however, to pre-filter water that is to be further treated with a disinfectant. If the emergency water supply is cloudy, visibly muddy or dirty with sediment, filtering the water through any filter that happens to be on hand will reduce the debris in the water and improve the ability of the next water disinfection step to operate more quickly and reliably. Beginning at DRINKING WATER - EMERGENCY PURIFICATION we list various water disinfection and treatment options.

Reverse Osmosis for Water Purification in an Emergency

Reverse osmosis also removes most contaminants from water; however in an emergency where public water supplies and/or electrical power are not provided, we do not assume that a home or building reverse osmosis system will be functional. If, however, the building has water pressure, a RO system will work just fine since normally these systems use only water pressure to operate the filter system.

Locate the RO system in the building and follow the water piping leaving that device so that you are sure to take drinking water only from fixtures that are supplied with treated water. Even in this case, if the building water piping downstream from the RO system has been flooded it will be unsanitary and is likely to need disinfection before water taken through that piping can safely be consumed.

See REVERSE OSMOSIS WATER TREATMENT for photographs of what RO equipment looks like and other details about that water treatment method.

Portable reverse osmosis water treatment equipment is available from companies such as Crystal Clear Supply.

Silver Ceramic Water Purifiers

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.

Sink Cartridge Type Water Filters as Water Purifiers in an Emergency

Sink cartridge water filters: We would not rely on the smaller store-bought filter cartridges that are simply attached to the tip of a kitchen sink faucet without clear documentation about just what that filter cartridge can remove from water, and how many of gallons of water it can process before it is exhausted. It would be unsafe to continue to "purify" water through an exhausted cartridge like filter. In contrast, ceramic water filters have a very high gallon capacity and most models can simply be cleaned and re-used.

Guide to UV Lights for Emergency Water Purification

UV Lights for water purification: UV Lights are not filters. UV lights for drinking water treatment are installed in some properties as a means to kill bacteria in a water supply. We do not anticipate that UV light systems will be working in a disaster area, and we are doubtful that one can rely on this process for emergency drinking water purification: even if a UV light system is working, it will at kill bacteria and similar pathogens only.

A UV light water treatment system will not remove chemical contaminants in a water supply. See see UV -ULTRAVIOLET LIGHT TREATMENT for details of residential type UV light water treatment systems as well as a discussion of when such systems are useful and appropriate.

UV Light & Giardia: UV light does not kill cysts, according to Dr. Amin. Websites that advertise use of UV light to kill giardia may be misleading. UV light will kill Giardia trophozoites but the real concern for drinking water is the cysts, since it is the cysts from stool that appear there. Other treatment methods may be needed if Giardia is present in the water supply.

UV light for water disinfection where Giardia is present has, however, been successfully used in combination with chlorination as an approach to killing Giardia in 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

• 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
• 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
• Dr. Omar Amin, of the Tempe AZ Parasitology Center, corresponded with 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.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• 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."
  
• 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."
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
• Wilderness Medical Society has advice about boiling water for consumption
• Princeton University - www.princeton.edu
• "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
• "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] http://www.amsus.org/military medicine/milmed.htm
• "Drinking Water Safety in Emergencies", University of Minnesota extension, extension.umn.edu/info-u/nutrition/BJ646.html
• 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.
• www.epa.gov/ogwdw/mdbp/pdf/alter/chapt_2.pdf provides an article on use of disinfectants for water treatmen
• This patent application for UV light sterilization www.patentstorm.us/patents/6565803.html Lists good references on water purification for Giardia et als
• 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)
• 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.

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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