Purifier vs common water filter

There are two different classification standards for water treatment devices.

The first classification is a water filter, to meet this standard a water treatment device must remove at least 99.99% of pathogenic bacteria. This is known in the water filter industry as a log 4 reduction.

The second classification is a water purifier, to meet this standard a water treatment device must remove at least 99.9999% of pathogenic bacteria (log 6 reduction). In addition the water purifier must be capable of reducing viruses by at least 99.999% (log 5 reduction).

How To Make Your Own Water Filter

Jerry and I have talked about the need to have a good water filter handy in case we have to get drinking water from the creek. I looked at some on Lehman’s, like the Berkley shown above, but they run around $270!!

I was very excited to find in the comments section of their product page a link that somebody had left telling how to make your own home made Berkey water filter out of two 5 gallon buckets with lids, a pair of Berkey filter elements, and a food grade spigot. You can usually find food grade buckets and lids in the bakery department of your grocery store for free, and you can get the filters and spigot at Lehman’s for a little over $100. Read the whole ingenious step-by-step on how to make your own water filter for less HERE.

How to Purify or Sterilize Drinking Water

for Emergency Use

After a Flood, Fire, or Earthquake Disaster

http://www.inspectapedia.com/water/Drinking_Water_Purification.htm

This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane.

For explanation of the types of contaminants found in water and how they are removed in residential water systems, see WATER TESTS, CONTAMINANTS, TREATMENT. See WATER TREATMENT EQUIPMENT CHOICES for details on other water treatment options. See Filters for Drinking Water Purification for a discussion of portable and emergency water filters that are designed to purify drinking water, including portable ceramic water filters, silver ceramic filters, magnetic (bogus) water purifiers, paper and polypropylene water filters, etc.

See DRINKING WATER PURIFICATION for a discussion of various methods used to purify emergency drinking water. 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.

© Copyright 2011 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

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. Also see the U.S. Army field manual FM 21-10 Chapter 2: Individual Preventive Medicine Procedures where preferred and alternative methods of emergency drinking water purification are discussed:
  • Iodine Tablets: per quart, one tablet in clear water, two in cloudy or cold water
  • Chlorine Ampules (U.S. Army issue): Fill your canteen with cleanest water available. Mix one ampule of chlorine with one-half canteen cup of water, stir the mixture with a clean device until contents are dissolved.
    Take care not to cut your hands when breaking open the glass ampule. Pour one-half plastic canteen capful or one NBC canteen capful of the above solution into your canteen of water. Place the cap on your canteen and shake. Slightly loosen the cap and tip the canteen over to allow leakage around threads. Tighten cap and wait 30 minutes before drinking.
  • Tincture of Iodine: Fill canteen with cleanest water available. Add 5 drops of 2 percent Tincture of Iodine per canteen/quart. If water is cold or cloudy, add 10 drops. Mix thoroughly by shaking canteen. Slightly loosen the cap and tip canteen over to allow leakage around threads. Tighten cap and wait 30 minutes before drinking.
    Very cloudy or cold water may require prolonged contact time. Let stand several hours or overnight if possible. Details about using iodine to purify drinking water are at Iodine to disinfect drinking water
  • Household Bleach / Common Bleach: Fill canteen with cleanest water possible. Read label on bleach bottle to determine amount of available chlorine. Liquid chlorine laundry bleach usually has 4 to 6 percent available chlorine.
    
  • Drops of Bleach to Be Added to a One Quart Canteen For Emergency Drinking Water
    Available Chlorine	Clear Water	Cold or Cloudy Water
    1%	10	20
    4—6%	2	4
    7--10%	1	2

    
    Place cap on canteen and shake. Slightly loosen the cap and tip canteen over to allow leakage around threads. Tighten cap and wait 30 minutes before drinking. Details about using bleach to purify drinking water are found at 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. We provide more details about using disinfectants to purify drinking water at How Much Disinfectant to Use.
  • If the source water is fdrom a raw water supply such as a stream or pond, the treated water product should have a 5 ppm residual chlorine level after 30 minutes. Under certain conditions, the local medical authority may direct a higher residual of 10 ppm. A chlorine colorimetric test kit is used to test the chlorine level.
  • When chlorine or iodine is not available, boil water for 5 to 10 minutes. In an emergency, even boiling water for 15 seconds will help. Boiled water must be protected from recontamination. Details about boiling water for drinking water purification are at Boiling water to disinfect it: boil the water to make it suitable for drinking.
• 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
  Ceramic Filters & Water Purification
  Colloidal Silver Water Purification
  Iodine Tablets or Iodine Disinfectant
  Bleach as a Disinfectant for Drinking Water
  UV WATER DISINFECTION, PORTABLE
  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 - don't get electrocuted in a flooded building
  FLOOD DAMAGE TO FOUNDATIONS - assessment, prevention, repair
  FLOOD RESPONSE CHECKLIST - Checklist of Key Steps to Minimize Mold Damage After a Building Flood
  FLOOD DAMAGE RFERENCES - Further Steps to Avoid Mold Damage After a Building Flood
  FLOOD VENTS & FLOOD PORTS - How to Use Flood Vents for Structural Protection from Flooding - Flood Venting in Foundations and Enclosures Below Design Flood Elevation
  FLOOD-CAUSED MOLD, PREVENTION - Further Steps to Avoid Mold Damage After a Building Flood
  INEFFECTIVE MOLD PRODUCTS - Checklist of Key Steps to Minimize Mold Damage After a Building Flood
  Mold in Fiberglass Insulation - risk of hidden mold reservoirs in fiberglass building insulation
  Mold on Fiberboard Insulating Sheathing - how to remove wet fiberboard insulation from flooded buildings
  MOLD, FURTHER STEPS to PREVENT - Further Steps to Avoid Mold Damage After a Building Flood
  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
  WHEN TO STOP LOOKING FOR MOLD - after Flooding: When is a Mold Cleanup Job Complete?
  Wind Damage to Roofs - how to assess and identify wind damage to roofs
PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
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
• U.S. Army Field Manual 21-10, Field Hygiene and Sanitation, 1988, web search 07/02/2010, original source: http://www.enlisted.info/field-manuals/fm-21-10-field-hygiene-and-sanitation.shtml
  The purpose of this manual is to assist individual soldiers, unit commanders, leaders and field sanitation teams in preventing disease and environmental injuries. The manual provides information on preventive medicine measures (PMM) to the individual soldier as well as essential information for the unit commander, unit leaders, and the unit field sanitation team on applying unit level PMM.
  • FM 21-10 Chapter 1: Introduction to the Medical Threat
  • FM 21-10 Chapter 2: Individual Preventive Medicine Procedures
  • FM 21-10 Chapter 3: Leaders Preventive Medicine Procedures
  • FM 21-10 Chatper 4: Unit Field Sanitation Team
  • FM 21-10 Appendix A
  • FM 21-10 References
  • FM 21-10 Index
• 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 07/24/2010: (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

• 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/

• "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.

• CHLORINE IN DRINKING WATER - Does Chlorine in Drinking Water Harm the Septic Tank? - Septic Tank Cleaning Advice
• CHLORINE IN SEPTIC WASTEWATER - Septic Tank Maintenance: Chlorine in Septic Systems - Septic Tank Maintenance Advice
• Drinking Water testing, contamination, correction - all topics
• Drinking Water Testing Advice for home buyers home owners home inspectors
• Choices of Water Tests & Fees: A Summary of Types of Water Tests, Degrees of Comprehensive Water Testing, Details of Water Test Parameters
• Cheating on water tests: Testing Water for Real Estate Transactions - make sure your water test is valid
• Drinking Water Contamination and Pollution How to Detect, Test, Correct, and Prevent Well Water Contamination - US EPA - Groundwater
• Interpreting Drinking Water Test Results what the results mean and what to do about them
• Correcting Unsatisfactory Water what to do, when to do it, treatment alternatives, equipment, filters, etc.
• Water Treatment for Contamination, Hardness, Odors, Sediment, Etc: choices of systems, recommendations
• Drinking Water Contaminant Levels - Maximum Allowed
• How to Reduce Lead Contamination in Drinking Water: how to test & correction lead in drinking water
• Lead Contamination from Water Supply Lines/Entry Mains, Lead Testing & Correcting Contamination from - Lead Pipe Problems/Advice
• Ohio State University article on the concentration of chlorine necessary to act as an effective disinfectant, and the effects of the water's pH and temperature: See http://ohioline.osu.edu/b795/b795_7.html for details.
• Extreme Lead Poisoning Symptoms Suggested by Feb 2006 NY Times Article on Kosovo Roma Camps
• When and How to Shock or Chlorinate a Well - Procedure for Shocking a Well to (temporarily or maybe longer) "Correct" Bacterial Contamination
• Water Requirements, Home & Outdoor Living
• Water Supply & Drain Piping, Wells, Pumps, Water Supply Equipment

Water Supply & Drain Piping, Wells, Pumps, Water Supply Equipment

• Water pressure tanks - how to diagnose the need for air, how to add air, stop water pump short cycling to avoid damage - water storage water pressure tank safety.
• Diagnosing Clogged Drains: Is it a blocked drain or the septic system? - A First Step for Homeowners
• Water Requirements, Home & Outdoor Living
• Drinking Water Contamination, Testing, Well Sanitation, Water Tests
• Drinking Water Supply, Contamination Levels, Water Testing Procedures
• Water Supply & Drain Piping, Wells, Pumps, Water Supply Equipment

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

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

  The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

• 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
• 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.
• 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.
• U.S. Army Field Manual 21-10, Field Hygiene and Sanitation, 1988, web search 07/02/2010, original source: http://www.enlisted.info/field-manuals/fm-21-10-field-hygiene-and-sanitation.shtml
  The purpose of this manual is to assist individual soldiers, unit commanders, leaders and field sanitation teams in preventing disease and environmental injuries. The manual provides information on preventive medicine measures (PMM) to the individual soldier as well as essential information for the unit commander, unit leaders, and the unit field sanitation team on applying unit level PMM.
  • FM 21-10 Chapter 1: Introduction to the Medical Threat
  • FM 21-10 Chapter 2: Individual Preventive Medicine Procedures
  • FM 21-10 Chapter 3: Leaders Preventive Medicine Procedures
  • FM 21-10 Chapter 4: Unit Field Sanitation Team
  • FM 21-10 Appendix A
  • FM 21-10 References
  • FM 21-10 Index
• 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/

 Potable Rainwater: Filtration and Purification

http://www.harvesth2o.com/filtration_purification.shtml

by Doug Pushard

When I was growing up, I remember drinking out of a rain barrel with a ladle. My great aunt would yell out the door, “Remember not to drink off the top!” That was then and now is now.

A lot has changed in 4 decades. There are a lot more pollutants, and we are more aware of the risks. We now know that E. coli and other harmful bacteria can be passed along in untreated contaminated water. A report by Peter H. Gleick estimates that if no action is taken to address unmet basic human needs for water, as many as 135 million people will die from water-related diseases by 2020.

Rainwater harvesting is viewed by many, including the EPA, as a partial solution to the problems posed by water scarcity: droughts and desertification, erosion from runoff, over-reliance on depleted aquifers, and the costs of new irrigation, diversion, and water treatment facilities.

Harvested rainwater in the U.S. is used mostly for irrigation; however, there is a growing interest in using rainwater for drinking and other indoor uses. Over 50% of household water is used indoors; bringing rain indoors could save the expense and environmental costs of treating and transporting water.

Can rainwater be made safe to drink? Yes. How safe? As safe as your well or tap water. How do you make it safe for indoor use? By filtering and purifying it.

Contaminants in water may include algae, air pollution, bird excrement, and leaves, sand, and dust. Local wells have dealt with these problems for decades. Installation of filtration and purification equipment can remove these contaminants at home as well.

First, take measures to keep foreign matter out of the incoming rainwater. First flush devices, gutter screens and other screening mechanisms keep the rainwater as clean as possible before it enters the conveyance system. Using screens and filters will greatly reduce maintenance and lengthen the life of the pump and filtration/purification system.

Even the best screening systems will allow unwanted particulates into the cistern. To keep sediment where it belongs, at the bottom of your tank, screen incoming rainwater, give the remaining sediment time to settle, avoid disturbing it, and don’t pull water from the bottom of the tank. Use a floating filter, which extracts water from the middle of the tank, leaving sediment undisturbed.

Next is filtration, which removes debris from the water. Disinfection or purification follows, which kills contaminants and removes harmful substances that may be present.

To determine what type of system you need, test the rainwater at a reliable laboratory. Without testing, you could spend a lot of money on equipment that will not give you safe water.

Filtration is included in every system, even simple irrigation systems. Examples of filtration systems include: screen filters, paper filters, and carbon or charcoal filters.

Almost all systems use multiple filters. For example, after gutter screens and/or a first flush device, a system often includes two in-line filters of increasing fineness, a carbon filter and a UV light. Each of these are described below to assist you in evaluating what might be the right alternative for your planned water use and required water quality.

In starting to evaluate filter options, it is imperative to know exactly what the filter system you select will actually remove from the water. National Sanitation Foundation/American National Standards Institutions (NSF/ANSI) standards are the best, most stringent in the industry. Almost all water-filtration products are certified under NSF Standard 61 for Drinking Water System Components (see Related Topics). But the critical standards for contaminant removal are Standard 42, “Drinking Water Treatment Units – Aesthetic Effects,” and Standard 53, “Drinking Water Treatment Units – Health Effects."

Standard 42 covers specific aesthetic contaminants (chlorine taste and odor, and visible particulates). Standard 53 covers health-related contaminants, such as Cryptosporidium, Giardia, lead, and volatile organic chemicals that may be present in drinking water. Systems that meet both of these standards are available, but expensive. Fortunately, the NSF website (see Related Topics) provides an easy way to search for units made by a specific manufacturer or that remove a specific contaminant.

Filters and Disinfection

Filters are measured in microns. One micron is about 1/25,000th of an inch. For comparison, sand is about 100 – 1,000 microns, a human hair is about 100 microns, a particle of dust is about 1 micron and a virus can be smaller than .01 micron.

The first filters in a system are cartridge filters. They range widely in what they are capable of removing and are used in a series (e.g., a 20 micron followed immediately by a 5 micron filter).

Filters are rated by the smallest size of particle they are capable of filtering. The smaller the micron size the better the filter. However, the finer the filter, the higher its cost and the slower its process. Filters have to be changed regularly, as an old, used filter is an excellent environment for microorganisms and potentially harmful pathogens.

For wells and rainwater systems a larger (e.g., a 50 micron) filter or equivalent screen (e.g., 300 mesh) should be used first to eliminate sand and large particles. This screen should be easily accessible and cleaned quarterly. Next is a 20 or 10 micron filter, followed immediately by a 10 or 5 micron filter. These are cleaned less frequently, but at least annually.

Filters will not eliminate all substances in the water. To create drinking quality water, filtration is always followed by disinfection. The EPA requires surface and ground water to be disinfected before it is consumed. Consequently, public water systems add disinfectants to destroy microorganisms that can cause disease in people and animals.

This is also necessary for rainwater, as the natural environment contains many microorganisms. Most are not harmful to us. Some, however, such as Giardia lamblia, can be deadly. These need to be eliminated from water before it is consumed.

Kinds of disinfection include chlorinization, ozonization, ultraviolet (UV) light, and membrane filtration. In evaluating disinfection methods, be aware that some actually create unhealthy byproducts that need to be treated.

The effectiveness of disinfection is judged by looking for an indicator organism that, if present, indicates other more harmful pathogens may be present. In getting a water test, this indicator organism is Total Coliform Bacteria that, if present, indicates other pathogens may be present as well.

Chlorine has been used as a disinfectant in public water systems for most of the past century. The introduction of chlorine to disinfect water has virtually eliminated waterborne diseases such as cholera, typhoid, dysentery and hepatitis, saving thousands of lives. However, it is often maligned due to suspected side effects.

For disinfection purposes, 2.3 fluid ounces of household bleach must be added per 1,000 gallons of water. Chlorine dosage rate will vary depending on quantity of water to be treated, pH and temperature.

A major downside of chlorine is that it is very reactive and easily combines with naturally occurring organic material to create harmful trihalomethanes (THMs) like chloroform. Chloroform is formed when chlorine reacts with either humic and/or fulvic acids, which are commonly found in water.

Because chlorine is reactive, it quickly dissipates. Keeping the dosage rate correct is critical when using this method of disinfection. THMs should be tested for in the water source if you are going to use Chlorine.

To reduce the possibility of harmful byproducts with the use of Chlorine, do the following:

• Remove the byproducts after they have been created. This is costly, typically meaning other purification systems must be employed (e.g., Reverse Osmosis or other purifcation systems) or
• The concentration of particulates/organics in the water before it is treated. This is accomplished by using filters to remove these substances from the water prior to chlorine treatment.

The Chlorine smell and taste can be removed with an activated carbon filter, often referred to as a charcoal filter. Granulated activated carbon filters are sometimes made from coconut shells and can be considered a “green” solution. Carbon block filters are compressed activated carbon, fused with a binding substance into a solid block.

Ultraviolet Light

An alternative for disinfecting water is Ultraviolet (UV) light. UV lights have been used for nearly a century in Europe and are now common in the US. With UV lights, the water must always pass through a filtration system first. If no filter is used, pathogens and bacteria will cast shadows in the flowing water, thereby allowing live organisms to pass through unharmed.

UV light works by penetrating an organism’s cell walls and disrupting the cell’s genetic makeup, making it impossible to reproduce and rendering it harmless. Often it is claimed that it kills the microorganism, but it doesn’t - it just makes them unable to reproduce and thus harmless. UV lights do not change the chemical composition of the water and leave behind no by-products.

For UV to be effective the right light dose must be used to a specific unit of water and the water must be clear of suspended solids and other particulates. Most UV units are usually insensitive to temperature and pH differences in the water, but manufacturers’ fine print should be read and followed.

There are several issues with UV lights should be taken into consideration:

• Replace the bulb at the manufacturer’s specified intervals – generally after 9,000 hours, or about every 12 months;
• UV light is not visible to the human eye, so it may appear to be lit and in fact is not working;
• The glass enclosure around the light needs to be cleaned occasionally for the UV light to be effective;
• If no backup light is installed the water needs to be shut off upstream of the bulb prior to replacing the unit. Generally it is prudent to disinfect the water downstream after the system has been shut down for any reason.

Correct UV treatment is effective in reducing harmful pathogens from the water. It is generally recommended that home units include alarms to notify the user when a bulb needs to be serviced or the unit is not working. Purchase a unit that has an automatic bulb cleaner, to reduce maintenance requirements. Two units should be installed, so when one unit needs servicing the second unit can be turned on so there is no disruption in disinfecting the drinking water.

UV light manufacturers rate their systems to a given dosage at a given flow rate (e.g., 10 gallons per minute). When installing a UV light, make sure the flow rate of the UV unit is matched to your flow rate of water (i.e., the pump flow rate). If the pump rate is greater than that of the UV light, install a pressure regulator or flow restrictor.

To properly treat the rainwater, it must contain particulates no larger than 50 microns and contain no tannins, sulfur or sulfur-related bacteria, have less than 0.3 parts per million of iron, and less than 0.005 parts per million of manganese. Knowing whether these are in the water and need to be treated is a great reason to test your water before installing a system. If any of the above is present in the water, the filters must deal with these elements before the water is treated by a UV light. Most of these will not be present in rainwater, but could result from local air pollution or contamination of the conveyance system. Don’t assume anything until your water has been lab tested.

The UV light unit is typically installed after all filtration and the resulting water is clean, bug-free and ready to use. Entry-level units will handle about 10 gallons per minute. The price of the unit will increase as options and flow rates increase.

Membrane Filtration

Membrane filtration is another alternative. Membrane filtration involves pushing water through a layer of material. Pressure-driven membrane technologies include microfiltration, ultrafiltration, nanofiltration and reverse osmosis. It is one of the few technologies capable of removing pharmaceuticals, and creates no byproducts.

Membrane technologies are more costly than other alternatives, but prices are rapidly declining. Most water purification experts expect membrane technology to become the prevalent technology in smaller systems over time as their price drops.

Choosing the right membrane technology is not straightforward, as the technology is changing and there are no real standards. Make sure you know what you need and match it to the type of system you are evaluating. Again, it is critical to test your water to know what you need before evaluating options.

Microfiltration (MF) is a membrane separation process using a pore size of .03 to 10 microns. Although this does not sound like a big range, when it comes to water purification, it is. The smaller the pore size, the more the system will remove. Microfiltration membranes are good for the removal of sand, silt, clay, algae, cysts and some bacteria.

Ultrafiltration (UF) is a membrane separation process using a pore size of approximately .002 to .1 microns. UF will remove all materials removed by an MF system, plus some viruses.

Nanofiltration membranes (NF) have an approximate pore size of only .001 microns. These small pore sizes require much more power to push water through the membrane and generate more waste than either MF or UF filtration systems. These systems eliminate virtually all cysts, bacteria, viruses, and other materials, including minerals. Consequently, the resulting water has a low pH that can be corrosive and needs to be remineralized, commonly using limestone, to raise the pH. Due to the greater power requirements, NF has yet to become mainstream.

Reverse Osmosis (RO) is the most widely used membrane technology today. These systems remove particles as fine as .001 microns, are compact, simple to operate and have been in use for over a decade. RO systems remove radium, natural organics, pesticides, cysts, bacteria and viruses. To ensure contaminant reduction, seek out units certified by NSF for contaminant reduction and not just safety. RO systems produce waste water that needs to be processed; however, the newer units are becoming “greener,” producing less, but still significant, waste. These units vary greatly in their efficiency, so make sure to ask about waste and efficiency when shopping for an RO system.

RO waste water contains a high concentration of the contaminants removed from the water, so dealing with this waste must be planned for when installing an RO system. Options for dealing with this water include plumbing through a greywater system to the irrigation system or directly to the septic system.

RO systems come in small under-the-counter units or whole-house systems. Prices will vary greatly for these units and only NSF-certified units should be considered. Under-the-counter units generally include a sediment filter, a carbon filter, the RO membrane and another carbon filter, and will generally cost under $1,000. A whole-house unit contains all the same components, but is capable of handling much larger water flow rates, and generally includes a calcite or equivalent filter to reduce the pH of the water, and a large storage tank (e.g., 20 – 50 gallons). The cost of a whole-house unit can run upwards of $8,000, depending on size of the house and family.

Regardless of system size, maintenance needs to be performed regularly. The most frequent maintenance is changing cartridges. Filters are used to protect the RO membrane from particle fouling. As these filters trap particles from the water supply, a reduction in pressure occurs. Many RO units include a low-pressure switch that prevents the RO from running if the pressure drops too low. Check the allowable pressure drop across the cartridge and compare this to the incoming feed pressure. If it is lower than manufacturer recommendations, the filters need to be replaced.

Distrillation

The last commonly available purification technology is distillation. Distillation separates the water from the impurities through heating and then collecting the condensation. It is very energy intensive and loses about 5-10% of the water due to evaporation. Distillation removes almost all substances from the water with the exception of volatile organic chemicals (VOCs) that evaporate easily. To this end, some distillation systems are also equipped with carbon filters to remove the VOCs.

Distillation works slowly to reduce energy requirements and, like RO systems, will store the purified water in a tank for later use. In addition to using a lot of electricity to operate, distillation systems generate heat.

Distillation units producing 5 -12 gallons of water a day will typically cost about $1,500 - $2,000. Cost will increase as capacity increases and as options are added. High-end automatic home units with larger storage capacity may cost upwards of $4,000. New solar distillers give you the option of reducing the electrical requirements.

Standard Practice for Household Use

A common practice in off the grid homes is to filter all the incoming rainwater and then store it in a small pressure tank. From the pressure tank the outgoing water is split into two separate paths - one path for potable and the other for non-potable water. A purification process is added to produce potable water. The major advantage of this approach is that it requires a much smaller unit and costs less, since it treats less water than a whole-house unit. But the disadvantage is that it requires a dual plumbing system – one to supply filtered but non-potable water to the toilets, clothes washer, irrigation faucets, etc., and one to supply potable water to the faucets.

An apparently low-cost, entry-level system is a countertop or pitcher type unit for potable water. However, when measured on gallons of water processed between changing filters, these units tend to be much more expensive in the long run. For example, a typical faucet unit available at most large hardware stores needs its filter changed every 100 gallons. For a family, this would be more than once a month and each filter costs about $30. This could cost nearly $500 a year, just for filters!

Before investing in filtration or purification equipment, invest in removing particulates before they enter into the system by installing gutter screens, leaf screens and roof washers. Removing materials before they enter the system is far easier and less expensive than dealing with them afterwards.

There is no perfect solution for disinfecting water, as all solutions have some environmental cost. Some require substantial energy, some create harmful by-products and some waste water. To save money, test your water (have you heard that before?) and get the right unit to solve your specific problem. Generally, the smaller the capacity the less expensive the unit will be overall, so get only what you need.

Lastly, remember that as the owner of a water system, it is your responsibility to maintain it. When you pay for utility-purified and -delivered water, maintenance is included in your bill. But when you own your water system, it is your responsibility to maintain it on a regular basis.

Rainwater can be safely used outdoors and indoors if the correct steps are taken to handle, store and clean it. Although not yet common in the US, indoor use of rainwater is practiced worldwide. As population growth continues, water rates increase and the desire to be “more green” and self-reliant increases, rainwater use will become more common here in the United States.

 How to Choose a Water Filter or Purifier, Part 1

http://www.rei.com/expertadvice/articles/water+filter+howto.html

Is it possible to drink straight from backcountry streams and never become ill? Yes.

Is it possible to drive down a large city's main boulevard, ignore a few red lights and never have a fender-bender? Yes.

Is either practice worth the accompanying risks? In our opinion, no.

Here's a brief overview to help clean up the confusion surrounding which type of water-treatment system is right for you.

1. Remember the difference between a filter and a purifier. While both remove bacteria from water particles using a mechanical process of pumping then forcing water through a filtering device, only purifiers can render viruses inactive using either an additional chemical or electrostatic process.
2. Waterborne viruses are believed to be less common in North American wilderness waters. But if you're traveling outside of the United States or Canada, you may want to opt for the more involved, and hence perhaps more expensive, purifying system.
3. When comparing filters and purifiers, look for an absolute—not nomimal—pore size of 0.2 microns. This industry wide benchmark indicates the system's smallest filtering capability. No bacteria larger than 0.2 microns can get through. Though a larger pore size of 0.3 or 0.4 may suffice in most situations, why take chances with your health?
4. Depending on its function, a water-treatment system can have numerous parts, some of which will need to be maintained or replaced on a regular basis. If your travel plans include many nights away from a reliable water source, you will not only have to pack the filter but the back-up and replacement parts that go with it.
5. And finally, to get the cleanest water possible be sure to clean and dry your filtering system regularly. When in the outdoors, try to collect still, clear water. Whenever possible, boil the water before treating it. Then, just as if you were seasoning a skillet, let the first few streams of water pass before you begin collecting your treated water.

The Murky Truth About Clear Water

Free-flowing mountain streams, for all their beauty and clarity, are not always the fountains of purity we imagine them to be. Backcountry water sources — crystal-clear rivers, lakes and streams — sometimes harbor microscopic pathogens (disease-causing agents) that are tough to pronounce, difficult to spell and, for many people, awful to ingest.

Giardia lamblia. Cryptosporidium. Campylobacter jejuni. Hepatitis A. All are members of an invisible fluvial zoo that may be present in pristine-looking backcountry water.

How do they get there? When water becomes tainted by animal or human feces. What impact could such microbes have? They can leave you reeling with diarrhea, abdominal cramps, nausea, weight loss and fatigue. How long might these symptoms last? Between 4 and 6 weeks. Maybe longer. Ugh.

More details on waterborne pests, and techniques you can use to defeat them, are explained in our Water Treatment clinic. In this presentation our goal is to provide guidance on the water-treatment strategy favored by most wilderness travelers — using a water filter or purifier.

Explaining Water Filters and Purifiers

Portable water filters and purifiers both operate on the same mechanical principle. Using a hand pump and intake hose, both slurp up "raw" water from a lake or stream and force it through an internal element (a filtering "medium"). This medium traps suspended elements — from fine sediment to invisible microorganisms — before dispensing clean water into a container of your choice.

What's the Difference?

Some definitions:

• Water filter— A microbiological device that removes bacteria (e.g., Campylobacter jejuni) and protozoan cysts (Giardia lamblia, cryptosporidium) from contaminated water.
• Water purifier— A microbiological device that removes bacteria, protozoan cysts and viruses (e.g., hepatitis A) from contaminated water.

Viruses are infinitesimal organisms too tiny to be trapped by a filter. Devices identified as "purifiers" usually cause water to interact with iodine (often in the form of iodine resins), which can render viruses inactive. Another purifier uses a positive electrostatic charge in its filter medium to capture viruses.

Viruses:

• may exist in water wherever there is a reasonable chance of human fecal contamination;
• are believed to be less prevalent in North American wilderness water sources than protozoan cysts or bacteria, but may be a greater threat in less developed countries.

Over time, filters have proven that they reliably protect wilderness travelers from the most common waterborne pathogens found in the North American backcountry: giardia and cryptosporidium. Still, purifiers and their antiviral feature offer an elevated level of security.

To fully disinfect suspect water using a water filter, the Centers for Disease Control and Prevention recommends 1) mechanically filtering the water, 2) treating it with a halogen (chlorine or an iodine solution), 3) letting it sit 15 to 60 minutes, 4) then drinking. For more details on this process, and a discussion of what pathogens may be found in backcountry water, refer to our Water Treatment clinic.

The difference between water filters and purifiers can seem arcane. In a separate discussion, we examine some of the more technical points.

How to Choose Water Filters or Purifiers, Part 2

What Really Matters

In an ideal world, a water filter or purifier will be:

• Simple to use
• Easy to pump
• Capable of sustaining a steady, generous flow
• Effective against waterborne pathogens
• Slow to clog, easy to clean
• Long-lasting

How can you tell if a filter or purifier delivers in these areas? Look for clues in the specification chart that accompanies each product description.

Understanding Specification Charts

Here's how to interpret the information:

Filter medium— This is the cartridge that actually traps pathogens (plus silt and other debris). The composition of the medium contributes greatly to the quality (and cost) of a device. Medium materials include:

• Ceramic: This is an effective, high-quality earthen material that can be cleaned many times before it needs a replacement. A ceramic cartridge captures most particles within .005 of an inch of its surface, so it's easy to brush away clogged pores and expose new ones. Cartridges themselves are fragile and require careful handling. Ceramic elements are the longest-lasting mediums and make a good choice for frequent backcountry visitors.
• Ceramic with a carbon core: This additional layer helps filter out the taste of halogens (chlorine and iodine) plus some organic chemicals, herbicides and pesticides.
• Fiberglass (or glass fiber): As effective as ceramic in straining out pathogens, but not as long-lasting.
• Structured matrix, or labyrinth: A dense, honeycombed material that effectively captures pathogens.
• Iodine resin: A chemical layer integrated with a purifier's filtering medium that deactivates viruses, though it does not actually remove them.

Field cleanable— A desirable feature. This means you may open the filter to brush or scrub the filter medium and increase water flow. Clogging should not cause you alarm; it shows the filter or purifier is working. Ceramic filter media can usually accept dozens of cleanings. Some models can be cleaned through backwashing (feeding clean water through the filter in reverse) but you need ample clean water in order to do so.

Longevity: How long will a filter or purifier last? Ceramic filters that can accept cleaning will last the longest, but the life of any filter depends on the clarity of wateryou pump through it. If possible, seek out clear water in still pools. You're likely to find less sediment in such water than in rushing water. Use a prefilter if your device includes one. Manufacturers sometimes include an estimate of the number of liters a filter or purifier is expected to treat effectively.

Pump force— The higher the number, the harder it is to pump. The Katadyn Pocket Filter, for example, has a pump force number of 16.5. While this is one of the longest-lasting filters available, it really gives users a workout as they pump.

A few additional considerations not listed in spec charts include:

Effectiveness— All of the filters and purifiers in REI's product mix will knock out larger microorganisms such as giardia and cryptosporidia. So what do you get for choosing a more expensive filter? Usually a longer-lasting filter medium, cleanability features and maybe a more efficient pump handle. Which filter is right for you? Here's a basic guide:

• If you're a recreational backpacker, someone who takes 1 or 2 overnight trips per year, an inexpensive filter will serve you well. Still, be careful about what type of water you send through it. Make it as clear as possible and the filter will last longer.
• If you visit the wilderness regularly, seek out a field-cleanable model designed to provide years of service.
• People who explore terrain closer to urban areas, at lower elevations and who travel outside the United States and Canada are candidates for a purifier.

Pore size— A familiar benchmark for determining a filter's effectiveness is to establish that it is a "point-2 (0.2-micron) filter." The number refers to the size of the pores (openings) in a filter medium. It's not a bad gauge, since the smallest bacteria measure 0.2 microns, yet some microbiologists will tell you it is a simplistic standard. Factors such as maximum flow rate, minimum wall thickness and adsorptive capacity can influence such a conclusion. Arguments can be made to show that a 0.3- or 0.4-micron filter can be as effective at trapping the particles as a 0.2-micron filter.

Tip: Look for "absolute" pore size (the largest and least effective holes) when evaluating filters, not "nominal" pore size.

Adsorption— When filter media block particles while clean water streams through, the process is known as "sieving." When particles stick to the media in the manner of a magnet, this is "adsorption." Activated carbon, found in some filters and purifiers, is especially effective at adsorption.

Other Considerations

Replacement cartridges are available for all of the filters and purifiers REI carries. They cost roughly one-half of the original unit's cost.

Some models attach directly to specific water bottles,which is a nice touch. It can prevent a heartbreaking spill in the field.

If you're visiting places where turbid water is a factor (say, the desert southwest), a cleanable ceramic filter should be tops on your list. The same goes if you'll be filtering for a group.

Avoid filtering water in area where animal or human activity is obvious.

Try and filter water from still, clear water sources. Many microorganisms tend to sink to the bottom of still water; a turbulent stream keeps them suspended.

Rather than filter directly from the stream or lake, put water in a pot and filter from that. This gives you a chance to examine exactly how the water looks before you send it through your filter. This helps prevent clogging. If the water is cloudy, let it sit in the pot for an hour or so, then skim the clearest water off the top.

Don't save the first few streams of output from your filter. They don't taste as fresh.

When you clean your filter, recognize you are handling a potentially contaminated object. Don't handle food or put your hands to your mouth after cleaning your filter.

Follow manufacturer instructions for cleaning and storage.At home, consider pumping a weak bleach-and-water solution through the filter to sterilize it. If you can disassemble your unit, allow it to dry out completely before storing it.

Explain Water Purification

http://www.livestrong.com/article/139476-explain-water-purification/

Water Purification Process

by Cathy Ellis

http://www.natureskills.com/water_purification_process.html