Water Purification

Purified water is water with all living micro-organisms removed.  This can be accomplished by either temperature or by chemical treatment.

In “Water – Part 4” we covered Water Filtration.  Will filtration alone make water safe to drink?  The answer is most of the time.  As we discussed ceramic filters cannot filter out viruses because viruses are too small.  Viruses like AIDS, Hepatitis, Norwalk, etc. are not found in rain water and are usually not found in our ponds, rivers, creeks and lakes.  During an emergency, with the lack of good sanitation and hygiene, the possibility of viruses finding their way into our water is definitely possible.

Purifying water by either Temperature Treatment or Chemical Treatment will kill all microbes and pathogens.  Temperature or Chemical Treatment will not remove sediment, heavy metals, or chemicals, so the water could be microbe free but still be cloudy or murky.  Additionally, chemical treatment can add a chemical taste to the water you treat.

My rule of thumb is if it is rain water, collected properly and then stored is a closed system, you can just filter the water to make it potable.  If you collect water from a lake, pond, river, creek, swimming pool or other open outside water source or if it is rain water that you have any questions about, then first treat it first with either heat or chemicals then filter it to remove suspended particles, odor, and/or bad taste.

 Temperature Treatment – According to the Wilderness Medical Society, water temperatures above 160° F (70° C) kill all pathogens within 30 minutes and above 185° F (85° C) within a few minutes. Bringing water to a boiling point 212° F (100° C) will ensure that all microorganisms have been killed. If you don’t have a heat source or the ability to boil water, bringing the water temperature up to 160° F (70° C) for 30 minutes is just as effective as bringing the water to a boil. Putting water in a clear 2 liter bottle and then placing it in a simple solar oven or in some direct sunlight on a corrugated metal roof on a hot day would work in a pinch. Just have a way of measuring the water temperature and keep it at 160° F for 30 minutes.

Chemical Treatment – The two main chemicals used to purify water are iodine and chlorine. There are a variety of commercial products available. Some products have expiration dates. Some products become less effect if exposed to light. The effectiveness of some products begins to diminish once the product is opened.

General Rules for cloudy water or water containing large particles:
1.  Let the water sit over night to allow sediment and particles to sink to the bottom.
2. Pre-filter the water using a cloth. Be careful not to stir up the settled sediment.
3.  Chemical treatments are less effective in water temperatures less than 60° F. Use extended treatment    times for water temperatures between 60° F and 40° F. Double the treatment time for water temperatures less than 40° F.
4.  Make sure the chemicals are thoroughly mixed with the water.
5.  Be sure to read and follow the manufactures instructions.

Iodine Treatment – Iodine is light sensitive and must be stored in a dark bottle. Iodine can also evaporate and must be stored in a tightly sealed bottle. Properly stored iodine has a long shelf life and a small bottle can treat several hundred gallons of water. Iodine does leave an after taste in the water that some people dislike. Also some people are allergic to iodine.

Liquid 2% Tincture of Iodine – Add 5 drops per quart when the water is clear. Add 10 drops per quart when the water is cloudy.

Polar Pure Iodine Crystals – This is my favorite Iodine treatment. Fill the Polar Pure bottle with water and shake. After one hour, add the number of capfuls of solution listed on the bottle. The built in particle trap prevents the crystals from getting out. Let the treated water sit for 30 minutes before drinking. Refill the Polar Pure bottle after use so that the solution will be ready for the next treatment. Crystals in the bottle can make enough solution to treat about 2,000 quarts of water.

Chlorine Treatment – There are many commercial chlorine treatments available. They include tablets and liquid mixes, mostly geared for the outdoors person away from home. Be sure to follow the manufacturer’s instructions when using these products.

Chlorine Bleach, 6% Sodium Hypochlorite – Chlorine bleach is an inexpensive and effective water purifier. The bleach should be unscented and the sodium hypochlorite concentration should be between 5% and 6%.

Dollar stores sometimes sell bleach with a 3% concentration. In that case you could just double the amount of bleach you add to the water.

The Clorox Company has stated that chlorine bleach begins to lose its potency after 6 months at the rate of 20% per year. You’ll need to rotate your bleach in storage at least every six months to insure its effectiveness for water purification.

The EPA recommends adding 2 drops of 6% chlorine bleach per quart or liter and adding 1/8 teaspoon per gallon to purify clear water. If the water is cloudy, double the amount of bleach. It is better to error on the side of too many drops than not enough drops. The only side effect of too many drops is the possibility of a slight chlorine taste. Based on these recommendations, here is a chart for common sized containers used for water storage:

1 quart – 2 drops of bleach
2 liters – 4 drops of bleach
1 gallon – 1/8 teaspoon of bleach
5 gallons – ½ teaspoon plus 8 drops of bleach
7 gallons – 1 teaspoon of bleach
55 gallons – ¼ cup of bleach

One gallon of 6% chlorine bleach will treat 6144 gallons of clear water and 3,072 gallons of cloudy water.

Calcium Hypochlorite – Calcium hypochlorite, most commonly known as “Pool Shock”, is a dry product that is 68% chlorine. It is widely use to treat water in swimming pools and hot-tubs and is more effective than chlorine bleach. Because of its powder form, it has a 10 year shelf life without any deterioration of the chlorine’s effectiveness as a water purifier. You can add calcium hypochlorite directly to water to purify it but it is highly concentrated, making it hard to measure the correct dose for small quantities of water. 1/8 teaspoon will treat 55 gallons of water. The easiest way to use it is to make a 5 percent to 6 percent chlorine bleach like mixture and use that as you would use bleach.

The EPA recommends using calcium hypochlorite as follows:
Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water. The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70% percent of its weight. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of the stock chlorine solution to each 12.5 gallons of water to be disinfected.

A 1 lb. package of calcium hypochlorite “pool shock” can treat almost 13,000 gallons of water.

Sodium Dichloro-s-Triazinetrione Hydrated – This is another type of swimming pool shock treatment. It dissolves very quickly and without any residue. 99% Sodium Dichloro-s-Triazinetrione provides 55.5% chlorine. You can use it the same way as calcium hypochlorite, but change the mother mix as follows: Use 1 1/3 to 1 ½ teaspoons of Sodium Dichloro-s-Triazinetrione for each 2 gallons of water for the mother mix. To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of the stock chlorine solution to each 12.5 gallons of water to be disinfected.

A 1 lb. package of calcium hypochlorite “pool shock” can treat almost 10,000 gallons of water.


Ed Rogers

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