Potable aqua drinking water purification tablets (C) Daniel FriedmanIodine or Lugol's Solution for Water Disinfection
How to Use Iodine Tablets or Liquid Iodine to Purify or Sterilize Drinking Water

  • IODINE for WATER DISINFECTION - CONTENTS: How to treat, purify, or sterilize drinking water in an emergency using iodine tablets or liquid iodine disinfectant. Effectiveness of germicidal iodine tablets for drinking water. Review of Potable Aqua® water purification tablets. Using emergency drinking water germicidal tablets to "make questionable water bacteriologically suitable to drink". Iodine effectiveness against Giardia lamblia
  • POST a QUESTION or READ FAQs about using iodine or iodine tablets to purify drinking water
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Iodine or iodine tablets to purify drinking water:

Here we explain how to use iodine tablets or liquid iodine as a drinking water disinfectant, and we cite the limitations of this method. This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane.

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Guide to Using Iodine, Bleach or Hydrogen Peroxide to Purify Drinking Water

Using Iodine Tablets or Iodine Disinfectant for Water Purification

Katadyne Micropur chlorine dioxide kit Iodine and bleach (chlorine or sodium hypochlorite) are the two common ways to sterilize water chemically to address bacterial contaminants. Iodine tablets have been shown to be effective against Giardia muris but iodine tablets are not effective against Cryptosporidium species.

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How to use water purification tablets: Paraphrasing the Potable Aqua® instructions: Two tablets are added to a quart of water (or to 1 liter of water) to be treated. The water plus tablets is left in a loosely-capped bottle or similar container, loose enough to allow some leakage. Allow this combination to stand for five minutes, then shake the container to moisten the threads on the container and its cap. Then tighten the cap and allow the water plus tablets to sit for 30 minutes before drinking.

Effectiveness of iodine-based water purification tablets: According to the manufacturer, these germicidal tablets used for "water purification" make questionable water bacteriologically suitable to drink, and the treatment is effective against Giardia Lamblia when used as directed. The product is intended for use when hiking or traveling. Potable Aqua® germicidal tablets have not been shown to inactivate Cryptosporidium cysts.

Watch out: Cryptosporidium cysts might survive a typical chlorine disinfection process (such as at a municipal water treatment plant).

For this reason some municipalities where Cryptosporidium cysts are a concern add a water treatment step using chlorine dioxide. Others may use a combination of UV light and chlorine in the water treatment procedure. This treatment is also available to hikers, travelers, and for emergency water supply use.

Aquamira™ and Katadyn™ (Micropur) provide portable or field-use water treatment kits using chlorine dioxide.

Katadyn® water purification tablets are sold as Micropur MP1. Quoting from Katadyn's product literature:

The Only EPA Registered Purification Tablets on the Market! And the only disinfection system effective against viruses, bacteria, cryptosporidium, and Giardia. No unpleasant taste. - Article number: 8014996

See FILTERS for DRINKING WATER PURIFICATION for some alternative approaches to water purification that can handle cryptosporidium cysts.

Guide to Using Tinctures of Iodine to Disinfect Drinking Water

Also see Wait Time & Water Temperature When Adding a Disinfectant - Before Drinking the Water where we provide more details about how to use iodine as a disinfectant.

[OPINION] In an emergency if you have nothing else, no way to boil water, no ceramic filter, but you have iodine, use it. But beware that iodine is not fully effective as a water sterilization method and be sure to see the allergic reaction warnings just above.

Using Lugol's Solution for Water Disinfection?

Reader question: I looked at the article about water sterilization from the link that you sent me and I saw no mention of Lugol's iodine as a sterilizing agent. Am I missing an article? I did see the post about using chlorine to kill Giardia cysts (GIARDIA in DRINKING WATER) where you cite:

"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. -- is the front page of this bulletin.

Is that 10 parts of chlorine to one part of Water? Is that the dilution of chlorine that one woul buy in a container of Chlorox? Thanks - G.B. / S.R. 5/30/2013


Watch out: The Manci citation specifies 10 milligrams of chlorine per liter of water: That is nowhere near a 10:1 ratio. Confusion about proper dilutions of disinfectants can lead to dangerous drinking water.

Furthermore, even with proper levels of chlorine disinfectant in water and proper contact time and proper water pH adjustment, disinfecting water does not remove other contaminants. See WATER DISINFECTION LIMITATIONS.

Lugol's Solution or Lugol's Iodine I2KI

Indeed chlorine (bleach), iodine, and permanganate all have been widely used in water treatment and disinfection systems. We have written about iodine as a water disinfectant and I've used various formulations including Lugol's iodine in the lab as a stain, but I've not written not specifically iodine mixed with potassium iodide - Lugol's solution - as a water disinfectant. (Synonymns I2KI (iodine-potassium iodide); Markodine, Strong solution (Systemic); and Aqueous Iodine Solution BCP).

I've read that while there is a historic use as a water disinfectant including following Chernobyl (where it had a second purpose) the mix can also be toxic if drunk or ingested at concentrations of 2% & above. The Wikipedia article adds "The lethal dose of free iodine for an adult human of 2 to 3 grams (2000-3000 mg) free iodine represents 40 to 60 mL (less than 2 fluid ounces) of 5% Lugol's solution. I'll add these notes to our iodine discussion found at along with some useful citations [27][28][29][30][31][32] about iodine as a disinfectant in articles citing the preparation and use of Lugol's solution.

Because there can be health problems from unsupervised consumpation of iodine, and lacking expert sources that argue otherwise, I am not competent to recommend regular use of Lugol's solution as a general purpose water disinfectant in any of the forms discussed. Here is what Backer & Hollowell say about using iodine (but not specifically Lugol's solution) to disinfect water:

Iodine is an effective, simple, and cost-efficient means of water disinfection for people who vacation, travel, or work in areas where municipal water treatment is not reliable. However, there is considerable controversy about the maximum safe iodine dose and duration of use when iodine is ingested in excess of the recommended daily dietary amount. The major health effect of concern with excess iodine ingestion is thyroid disorders, primarily hypothyroidism with or without iodine-induced goiter.

A review of the human trials on the safety of iodine ingestion indicates that neither the maximum recommended dietary dose (2 mg/day) nor the maximum recommended duration of use (3 weeks) has a firm basis. Rather than a clear threshold response level or a linear and temporal dose-response relationship between iodine intake and thyroid function, there appears to be marked individual sensitivity, often resulting from unmasking of underlying thyroid disease. The use of iodine for water disinfection requires a risk-benefit decision based on iodine's benefit as a disinfectant and the changes it induces in thyroid physiology.

By using appropriate disinfection techniques and monitoring thyroid function, most people can use iodine for water treatment over a prolonged period of time. Backer [29]


Continue reading at SOLAR WATER DISINFECTION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see VEGETABLE DISINFECTION where we include a discussion of use of iodine-based disinfectants for vegetable wash.

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