Chemical Disinfection for Emergency Water

Chemical Purification and Disinfection

Chemical purification and disinfection involves dissolving tablets into your filtered water and letting it set for a certain amount of time. As always and for good measure, make sure you filter the water AFTER you use chemical disinfectants. Once chemical disinfectants do what they do, you’re going to want to remove as many of the leftover critters as possible (chemical disinfectants kill microscopic invaders). The two most popular ways to chemically disinfect water are with iodine and chlorine tablets.

What are iodine tablets?

Iodine tablets are used to kill microorganisms. Each bottle costs in the neighborhood of $5 to $10 and contains 20 to 50 tablets. Depending on the manufacturer, each tablet contains 20mg of tetraglycine hydroperiodide. When introduced to water, the tetraglycine hydroperiodide liberates 8 mg of iodine per tablet. The iodine then targets microscopic organisms and penetrates the cellular wall destroying their ability to replicate and or survive.

The Upside: The bottles are cheap and somewhat effective. They’re easy to transport, light and will fit into just about any BOB.

The Downside: Iodine tablets won’t kill cryptosporidium. If you use iodine to purify your water, you may have to boil it anyway to kill cryptosporidium. (Feces being the main mechanism of transport for both giardia and cryptosporidium, it’s better to assume that your water has both.)

Some product lines swear up and down that their product doesn’t alter the taste of the water . . . much. Check the product reviews. Everyday people are more inclined to be honest than the companies who sell these products.

Warning: If you’re allergic to shellfish or iodine, you’re probably allergic to iodine tablets. If you use iodine tablets and have an allergy, you may encounter hives, rash, nausea, and headache. This is definitely one to ask your doctor about if you have any questions or concerns.

How to use Iodine Tablets:

  1. Read your package instructions carefully. They may be different from the generalized directions listed below.

  2. Keep them away from light. They typically come in either dark containers or individual foil wraps. If they’re exposed to light for too long, they lose their efficacy.

  3. Collect and filter your water.

  4. Add 2 tablets for every 1 quart. (4 quarts equals 1 gallon) Dissolve and stir or shake well.

  5. Let it sit for 30 minutes.

  6. If you find sediment at the bottom of your container, filter the water again. (I’m just gonna throw this in here and say you should filter it again anyway. Sediment and dead critter bodies, though microscopic, are still nasty.)

What are Chlorine Tablets?

Chlorine Dioxide is a common treatment for pool and potable water. The bottles of tablets range in price from $10 to $20 depending on quantity. They typically contain 6.4% sodium chlorite. When introduced to the water, the tablet dissolves and turns into gas. The gas is toxic to microorganisms (and people too in large enough quantities), penetrating cellular walls by oxidizing and reacting with the cell's amino acids. This interference kills the microorganisms.

The Upside: The bottles are lightweight and relatively inexpensive. 1 tablet purifies 1 quart of water, so you’ll use less of these tablets than with iodine. Chlorine tablets DO kill cryptosporidium (unlike iodine) if you use them as directed.

The Downside: It takes 4 hours minimum to completely purify water that contains cryptosporidium. If you’re in a hurry for a drink, this is not the solution for you.

Warning: Sodium Chlorite (the main ingredient in these tablets) is toxic in high doses, so make sure you’re following the directions carefully. (I repeat: filter, filter, filter.)

How to use Chlorine Tablets:

  1. Read your package instructions carefully. They may be different than the generalized directions listed below.

  2. 1 tablet per quart of water. 4 quarts is equal to 1 gallon so you’ll need 4 tablets for 1 gallon of water.

  3. Remove the tablets from the foil packing with a knife or scissors. (In other words, don’t touch them with your bare hands.)

  4. Dissolve in water, stir completely. Wait 4 hours before drinking the water.

  5. If you find any sediment at the bottom of your container, filter it again after the 4 hour wait. (Filter it anyway. I know, I sound like a broken record.)

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