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- Jun 16, 2003
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I keep reading misinformation about purifying water.
In another thread, we were directed to a nice site BUT it had bad information on water purification -- information known to be wrong since 100,000's got sick in Milwaukee in 1993 when chlorine was relied upon to purify the water in the municipal system. That's a few years ago, and yet . . . .
I just got a magazine in which the editors state that a filter with 3.0 micorn absolute filtering will give you "clean and safe drinking water" (a claim the manufacturer of the filter does not make).
Currently produced books get it wrong more often than right.
Here is a try at getting it right in summary fashion. Comment as your experience, knowledge, and willingness dictates. Feedback is a gift.
Making Water Safer - GERMS.
Water contains bacteria, viruses, and parasites. Some of them can make you sick. Let's call those critters “germs" for simplicity. Some germs are usually easily handled by your body's natural defenses. Some cause sickness fairly quickly and can put you flat on your back for days = Not Good. Some are easy to kill and some hard to kill. Water in nature should always be presumed to contain some germs.
Anything you can do to make water safer is well worth doing. Don't let the inability to make things perfect keep you from making things better. If the choice is between drinking questionable water and dehydration, drink the questionable water.
1) Running water is safer than standing water.
2) Clear water is safer than cloudy or dirty water.
3) Let cloudy water stand ("settle") so that particles collect towards the bottom of the container. Pour or scoop off the clearer water towards the top and, if possible, treat it using one or more of the six methods below.
4) Filter.
Almost any filtering of water reduces the particles in the water and, by doing so, improves taste and reduces the risk of illness. Again, reduction of risk is good even when elimination of all risk is not possible.
 Using the right commercial water filter can remove all germs except viruses if the filter is used properly. However, dangerous viruses are rare in North America and are easily killed by any water-treatment chemical on the market. (Recently, Sawyer has offered an EPA-approved filter with a
.02 micron specification that also removes viruses. Extensive field experience is lacking at this point.)
 Water can be filtered through layers of clean sand, grass, and charcoal contained in cloth (such as a sock or trousers leg), bark, aluminum foil, or some other container. A tripod lashed together in the field can support a series of more-or-less horizontal pieces of cloth, each with sand/vegetation/charcoal, through which water can be filtered. Take your time.
 A paper coffee filter can filter water.
 Water can be naturally filtered if obtained from a well dug ten feet or more away from a body of water (but it will likely by muddy and need settling and further filtration).
 Even filtration in several layers of cloth alone helps reduce risks.
 Following up filtering with boiling or chemicals sold to disinfect water improves the results.
5) Boil. Bringing water to a rolling boil will kill all germs. If you are careful -- careful -- water can be boiled over coals or a low fire in a container made of aluminum foil. It can also be boiled in a hole in a rock or log, in a container of bark, or in any other container that will stand boiling heat (212F) by carefully dropping rocks heated in a fire into the water until it boils. (Heat rocks that are already dry. Water in wet rocks may cause the rock to "explode," and the flying shards of rock can injure.) At altitudes above one mile, as in the mountains of the western U.S.A., water boils at lower temperatures, so boil for one minute to be safe.
6) Chemicals. Chemicals are sold for the specific purpose of disinfecting water. Directions should be followed carefully. Settling and filtering the water before using the chemicals increases the safety. Effectiveness of chemicals in killing germs depends on several factors that vary with your situation: amount used, time of exposure of water to the chemicals, temperature of the water, clarity of the water, ph of the water, minerals dissolved in the water, organic materials in the water. Because you cannot measure all of these variables, assume the worst in applying the directions on the container.
 Chlorine can kill most (but not all) germs. Chlorine will not kill the parasite cryptosporidium and is slow to kill another, Giardia. Both are common.
 Iodine can also kill most germs but is not reliable on Cryptosporidium and Giardia, especially as water temperature drops. It also presents some extra problems. Some people are allergic to iodine. They may know this as an allergy to shellfish (which contain iodine). If they disinfect water with iodine, they can become extremely sick. Iodine can also be dangerous for small children, those with thyroid problems, people who take lithium, women over 50, pregnant women, and people with kidney or liver problems. So always check the container to be sure what chemical you are using and check the circumstances of those who will be drinking the water.
 Chlorine dioxide is more effective than iodine or other chlorine products, but be sure to follow directions. In some circumstances, treatment for as long as four hours is recommended. (Aqua Mira is one brand.)
 Potassium permanganate is less effective than iodine or chlorine in disinfecting water but is better than nothing.
7) Solar Radiation and heating (SODIS). Water in a clear container (glass bottle, clear zip-lok bag, or clear plastic bottle [PETE - Type 1 plastic is the best container for SODIS]) when exposed to strong sunlight for eight hours is effectively disinfected. The container should be no more than five inches thick (in diameter in the case of a cylinder). The time required for disinfection varies according to the intensity of the sunlight and air temperature. Get the water as hot as possible. If the sun is hazy or clouds block some of the sunlight, treat for two days if you can wait that long. Water must be clear enough to allow reading newspaper-sized print thorugh the water. Filter as necessary and shake the filled container after filtering before placing in sunlight for treatment.
8) Distillation. Water vapor condensed on a clean surface and collected in a clean container is usually disinfected. This is accomplished by solar stills and steam collected in a cloth, as described for gathering potable water from salt water.
9) Electrical devices are sold (example "SteriPen") which disinfect water. They work but are expensive, delicate, and do not operate below freezing. Protect them from impact and freezing, have spare batteries, and use strictly according to directions.
In another thread, we were directed to a nice site BUT it had bad information on water purification -- information known to be wrong since 100,000's got sick in Milwaukee in 1993 when chlorine was relied upon to purify the water in the municipal system. That's a few years ago, and yet . . . .
I just got a magazine in which the editors state that a filter with 3.0 micorn absolute filtering will give you "clean and safe drinking water" (a claim the manufacturer of the filter does not make).
Currently produced books get it wrong more often than right.
Here is a try at getting it right in summary fashion. Comment as your experience, knowledge, and willingness dictates. Feedback is a gift.
Making Water Safer - GERMS.
Water contains bacteria, viruses, and parasites. Some of them can make you sick. Let's call those critters “germs" for simplicity. Some germs are usually easily handled by your body's natural defenses. Some cause sickness fairly quickly and can put you flat on your back for days = Not Good. Some are easy to kill and some hard to kill. Water in nature should always be presumed to contain some germs.
Anything you can do to make water safer is well worth doing. Don't let the inability to make things perfect keep you from making things better. If the choice is between drinking questionable water and dehydration, drink the questionable water.
1) Running water is safer than standing water.
2) Clear water is safer than cloudy or dirty water.
3) Let cloudy water stand ("settle") so that particles collect towards the bottom of the container. Pour or scoop off the clearer water towards the top and, if possible, treat it using one or more of the six methods below.
4) Filter.
Almost any filtering of water reduces the particles in the water and, by doing so, improves taste and reduces the risk of illness. Again, reduction of risk is good even when elimination of all risk is not possible.
 Using the right commercial water filter can remove all germs except viruses if the filter is used properly. However, dangerous viruses are rare in North America and are easily killed by any water-treatment chemical on the market. (Recently, Sawyer has offered an EPA-approved filter with a
.02 micron specification that also removes viruses. Extensive field experience is lacking at this point.)
 Water can be filtered through layers of clean sand, grass, and charcoal contained in cloth (such as a sock or trousers leg), bark, aluminum foil, or some other container. A tripod lashed together in the field can support a series of more-or-less horizontal pieces of cloth, each with sand/vegetation/charcoal, through which water can be filtered. Take your time.
 A paper coffee filter can filter water.
 Water can be naturally filtered if obtained from a well dug ten feet or more away from a body of water (but it will likely by muddy and need settling and further filtration).
 Even filtration in several layers of cloth alone helps reduce risks.
 Following up filtering with boiling or chemicals sold to disinfect water improves the results.
5) Boil. Bringing water to a rolling boil will kill all germs. If you are careful -- careful -- water can be boiled over coals or a low fire in a container made of aluminum foil. It can also be boiled in a hole in a rock or log, in a container of bark, or in any other container that will stand boiling heat (212F) by carefully dropping rocks heated in a fire into the water until it boils. (Heat rocks that are already dry. Water in wet rocks may cause the rock to "explode," and the flying shards of rock can injure.) At altitudes above one mile, as in the mountains of the western U.S.A., water boils at lower temperatures, so boil for one minute to be safe.
6) Chemicals. Chemicals are sold for the specific purpose of disinfecting water. Directions should be followed carefully. Settling and filtering the water before using the chemicals increases the safety. Effectiveness of chemicals in killing germs depends on several factors that vary with your situation: amount used, time of exposure of water to the chemicals, temperature of the water, clarity of the water, ph of the water, minerals dissolved in the water, organic materials in the water. Because you cannot measure all of these variables, assume the worst in applying the directions on the container.
 Chlorine can kill most (but not all) germs. Chlorine will not kill the parasite cryptosporidium and is slow to kill another, Giardia. Both are common.
 Iodine can also kill most germs but is not reliable on Cryptosporidium and Giardia, especially as water temperature drops. It also presents some extra problems. Some people are allergic to iodine. They may know this as an allergy to shellfish (which contain iodine). If they disinfect water with iodine, they can become extremely sick. Iodine can also be dangerous for small children, those with thyroid problems, people who take lithium, women over 50, pregnant women, and people with kidney or liver problems. So always check the container to be sure what chemical you are using and check the circumstances of those who will be drinking the water.
 Chlorine dioxide is more effective than iodine or other chlorine products, but be sure to follow directions. In some circumstances, treatment for as long as four hours is recommended. (Aqua Mira is one brand.)
 Potassium permanganate is less effective than iodine or chlorine in disinfecting water but is better than nothing.
7) Solar Radiation and heating (SODIS). Water in a clear container (glass bottle, clear zip-lok bag, or clear plastic bottle [PETE - Type 1 plastic is the best container for SODIS]) when exposed to strong sunlight for eight hours is effectively disinfected. The container should be no more than five inches thick (in diameter in the case of a cylinder). The time required for disinfection varies according to the intensity of the sunlight and air temperature. Get the water as hot as possible. If the sun is hazy or clouds block some of the sunlight, treat for two days if you can wait that long. Water must be clear enough to allow reading newspaper-sized print thorugh the water. Filter as necessary and shake the filled container after filtering before placing in sunlight for treatment.
8) Distillation. Water vapor condensed on a clean surface and collected in a clean container is usually disinfected. This is accomplished by solar stills and steam collected in a cloth, as described for gathering potable water from salt water.
9) Electrical devices are sold (example "SteriPen") which disinfect water. They work but are expensive, delicate, and do not operate below freezing. Protect them from impact and freezing, have spare batteries, and use strictly according to directions.
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That tells me SODIS is overlooked.