What method of water purification would you teach someone who lived...

Boiling
Boiling is the most certain way of killing all microorganisms. 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. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be killed, even at high altitude. To be extra safe, let the water boil rapidly for one minute, especially at higher altitudes since water boils at a lower temperature (see page 68.)

Chemical Purification
There are two types of chemical treatment: those using iodine and those using chlorine. There are a variety of products on the market, so follow the directions on the bottle. Be advised that many of the tablets have an expiration date and become ineffective after that point. Also, once the bottle has been opened, the tablets must be used within a certain period. When in doubt, buy a new bottle. Remember that chemical purification methods may only be partially effective, depending on the water temperature.

General Chemical Treatment Procedures
The effectiveness of all chemical treatment of water is related to the temperature, pH level, and clarity of the water. Cloudy water often requires higher concentrations of chemical to disinfect.
If the water is cloudy or filled with large particles, strain it, using a cloth, before treatment. Large particles, if swallowed, may be purified only “on the outside.”
Add the chemical to the water and swish it around to aid in dissolving. Splash some of the water with the chemical onto the lid and the threads of the water bottle so that all water areas are treated.
The water should sit for at least 30 minutes after adding the chemical to allow purification to occur. If using tablets, let the water sit for 30 minutes after the tablet has dissolved.
The colder the water, the less effective the chemical is as a purifying agent. Research has shown that at 50° F (10° C), only 90 percent of Giardia cysts were inactivated after 30 minutes of exposure. If the water temperature is below 40° F (4° C), double the treatment time before drinking. It is best if water is at least 60° F (16° C) before treating. You can place the water in the sun to warm it before treating.
Chemically treated water can be made to taste better by pouring it back and forth between containers, after it has been adequately treated. Other methods include adding a pinch of salt per quart or adding flavorings (e.g., lemonade mix, etc.) after the chemical treatment period.
Iodine Treatment
Iodine is light sensitive and must always be stored in a dark bottle. It works best if the water is over 68° F (21° C). Iodine has been shown to be more effect than chlorine-based treatments in inactivating Giardia cysts. Be aware that some people are allergic to iodine and cannot use it as a form of water purification. Persons with thyroid problems or on lithum, women over fifty, and pregnant women should consult their physician prior to using iodine for purification. Also, some people who are allergic to shellfish are also allergic to iodine. If someone cannot use iodine, use either a chlorine-based product or a non-iodine-based filter, such as the PUR Hiker Microfilter, MSR WaterWorks, or the Katadyn Water Filter.

Generally, the procedure is as follows:

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 Fill the Polar Pure bottle with water and shake. The solution will be ready for use in one hour. Add the number of capfuls (per quart of water treated) listed on the bottle, based on the temperature of the iodine solution. The particle trap prevents crystals from getting into the water being treated. It is important to note that you are using the iodine solution to treat the water, not the iodine crystals. The concentration of iodine in a crystal is poisonous and can burn tissue or eyes. Let the treated water stand for 30 minutes before drinking. In order to destroy Giardia cysts, the drinking water must be at least 68° F (20° C). The water can be warmed in the sun before treating or hot water can be added. Refill the treatment bottle after use so that the solution will be ready one hour later. Crystals in the bottle make enough solution to treat about 2,000 quarts. Discard the bottle when empty.
Potable Aqua This is an iodine tablet product. Follow the manufacturer’s instructions for use.

Filtration
There are a number of devices on the market that filter out microorganisms. A water filter pumps water through a microscopic filter that is rated for a certain-size organism. The standard size rating is the micron (the period at the end of this sentence is about 600 microns). Depending on the micron rating of the filter, smaller organisms (like viruses) can pass through. Be cautious when selecting a filter. You should know what potential organisms you need to treat for. You don’t want to go to an area where a virus like hepatitis A is present in the water (a problem in some developing countries) with a filter that will handle only a larger organism like Giardia.

Common microorganisms and the filter size needed:
Organism Examples General Size Filter Type Particle Size Rating
Protozoa Giardia, Cryptosporidium 5 microns or larger Water filter 1.0–4.0 microns
Bacteria Cholera, E. coli, Salmonella 0.2–0.5 microns Microfilter 0.2–1.0 microns
Viruses Hepatitis A, rotavirus, Norwalk virus 0.004 microns Water purifier to 0.004 microns

There are two basic types of filters (descriptions of several popular models begin on the facing page).

Membrane Filters use thin sheets with precisely sized pores that prevent objects larger than the pore size from passing through. Pro: Relatively easy to clean. Con: Clog more quickly than depth filters. Example: PUR-Hiker.
Depth Filters use thick porous materials such as carbon or ceramic to trap particles as water flows through the material. Pro: Can be partially cleaned by backwashing. Activated carbon filters also remove a range of organic chemicals and heavy metals. Con: Rough treatment can crack the filter, rendering it useless. Examples: MSR WaterWorks II, Katadyn.
Note: There is a difference between a water filter and a water purifier. Filters do not filter out viruses, but there are water purifiers, like the PUR Scout, that pass the water through both a filter and an iodine compound that kills any smaller organisms that have passed through the filter. These purifiers kill all microorganisms down to 0.004 microns; however, the filter should not be used by people who are allergic to iodine.

Common Practices for Using a Water Filter
Filter the cleanest water you can find. Dirty water or water with large suspended particles will clog your filter more quickly.
Prefilter the water either through a prefilter on the pump or strain it through a bandanna.
If you must filter dirty water, let it stand overnight for particles to settle out.
Tricks of the Trail

Some water filters come as sealed cartridges, making it impossible to inspect the actual filter cartridge. If the filter takes a serious fall, it could crack internally. If the filter inside cracks, unfiltered water can flow through the crack. Treat your filter with care, and if it takes a significant impact, throw it away. Remember, any intake hose from a water filter has been submerged in unfiltered water. Treat this hose as “contaminated” and keep it in a separate plastic bag.

Boiling water requires heat, which may be from a kerosene stove or dried yak dung, but is often in the form of a wood fire. Burning wood = deforestation in many of these fragile mountainous areas. For this reason I encourage trekkers to enjoy hot drinks in the tea houses, but not ask for boiled water to fill their water bottles. Filters do not do an adequate job of disinfection, and so I see no point in spending money on them or taking up valuable backpack space carrying them. I recommend iodine as the treatment of choice, unless there are contraindications to its use.

My own preference is to use Betadine® (10% povidone-iodine) in a small dropper bottle, and a one liter nalgene bottle. I fill up the bottle from a stream, drop in 4 drops of Betadine®, screw on the lid, and put it in my pack. Half an hour later, it is ready to drink. With minimal planning ahead, I rarely need water faster than this. I like this system because I carry Betadine® in my first aid kit anyway, and I personally think the flavor is less noxious than some other forms of iodine. I don’t usually feel the need to add flavor crystals to my water, rather I joke that iodine is “the taste of safety.” A little goes a long way: 30 ml of Betadine® is enough to disinfect 150 liters of water, or drinking water for about 50 days of active trekking (I am presuming that some additional fluid intake exists from tea, soup, meals, etc.).

5 COMMENTS

aiddogs5 December 7, 2012 At 9:37 am

Distillation it can be done by anyone.
That will take the time to do it.
It can even be done from using green leave.
Without the use of boiling water.
This as been known for years why have they not been told.
rikenelson December 7, 2012 At 9:06 am

The first choice is to bring water treatment devices with you whenever you travel to a developing country. However, if you have forgotten to bring one, consider the following options to make safe drinking water:

Boiling: Vigorously boil water for 5 minutes. The flat taste of boiled water can be improved by pouring it back and forth from one CLEAN container to another. Also, a small pinch of salt can be added to each quart of water boiled;

Chlorination: Add 5-10 drops chlorine bleach per quart of clear water, thoroughly mixing it and allowed to stand for at least 30 minutes. The treated water should have a slight chlorine odour; if it doesn’t, the dosage should be repeated and the water should stand for 15 minutes more. If this treated water has too strong a chlorine taste, it can be made more drinkable by allowing the water to stand exposed to the air (should be a light cover over the top to prevent insects, etc. from falling into the water). Pouring it back and forth between two CLEAN containers will also help.
seikenfan922 December 7, 2012 At 8:35 am

okay… I’d just go with simple gravimetric filtration for most purposes and subsequent boiling of said water.
Helmut December 7, 2012 At 7:48 am

Boil the water for 5 minutes before drinking. Use charcoal to remove as many chemical impurities as possible. If wood is not readily available, leave out the charcoal, and use animal dung as fuel.

Where in a coutry that is poverty stricken by definition are people going to get the chemicals we take for granted for this purpose?
missourim43 December 7, 2012 At 7:39 am

Boiling
Boiling is the most certain way of killing all microorganisms. 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. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be killed, even at high altitude. To be extra safe, let the water boil rapidly for one minute, especially at higher altitudes since water boils at a lower temperature (see page 68.)

Chemical Purification
There are two types of chemical treatment: those using iodine and those using chlorine. There are a variety of products on the market, so follow the directions on the bottle. Be advised that many of the tablets have an expiration date and become ineffective after that point. Also, once the bottle has been opened, the tablets must be used within a certain period. When in doubt, buy a new bottle. Remember that chemical purification methods may only be partially effective, depending on the water temperature.

General Chemical Treatment Procedures
The effectiveness of all chemical treatment of water is related to the temperature, pH level, and clarity of the water. Cloudy water often requires higher concentrations of chemical to disinfect.
If the water is cloudy or filled with large particles, strain it, using a cloth, before treatment. Large particles, if swallowed, may be purified only “on the outside.”
Add the chemical to the water and swish it around to aid in dissolving. Splash some of the water with the chemical onto the lid and the threads of the water bottle so that all water areas are treated.
The water should sit for at least 30 minutes after adding the chemical to allow purification to occur. If using tablets, let the water sit for 30 minutes after the tablet has dissolved.
The colder the water, the less effective the chemical is as a purifying agent. Research has shown that at 50° F (10° C), only 90 percent of Giardia cysts were inactivated after 30 minutes of exposure. If the water temperature is below 40° F (4° C), double the treatment time before drinking. It is best if water is at least 60° F (16° C) before treating. You can place the water in the sun to warm it before treating.
Chemically treated water can be made to taste better by pouring it back and forth between containers, after it has been adequately treated. Other methods include adding a pinch of salt per quart or adding flavorings (e.g., lemonade mix, etc.) after the chemical treatment period.
Iodine Treatment
Iodine is light sensitive and must always be stored in a dark bottle. It works best if the water is over 68° F (21° C). Iodine has been shown to be more effect than chlorine-based treatments in inactivating Giardia cysts. Be aware that some people are allergic to iodine and cannot use it as a form of water purification. Persons with thyroid problems or on lithum, women over fifty, and pregnant women should consult their physician prior to using iodine for purification. Also, some people who are allergic to shellfish are also allergic to iodine. If someone cannot use iodine, use either a chlorine-based product or a non-iodine-based filter, such as the PUR Hiker Microfilter, MSR WaterWorks, or the Katadyn Water Filter.

Generally, the procedure is as follows:

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 Fill the Polar Pure bottle with water and shake. The solution will be ready for use in one hour. Add the number of capfuls (per quart of water treated) listed on the bottle, based on the temperature of the iodine solution. The particle trap prevents crystals from getting into the water being treated. It is important to note that you are using the iodine solution to treat the water, not the iodine crystals. The concentration of iodine in a crystal is poisonous and can burn tissue or eyes. Let the treated water stand for 30 minutes before drinking. In order to destroy Giardia cysts, the drinking water must be at least 68° F (20° C). The water can be warmed in the sun before treating or hot water can be added. Refill the treatment bottle after use so that the solution will be ready one hour later. Crystals in the bottle make enough solution to treat about 2,000 quarts. Discard the bottle when empty.
Potable Aqua This is an iodine tablet product. Follow the manufacturer’s instructions for use.

Filtration
There are a number of devices on the market that filter out microorganisms. A water filter pumps water through a microscopic filter that is rated for a certain-size organism. The standard size rating is the micron (the period at the end of this sentence is about 600 microns). Depending on the micron rating of the filter, smaller organisms (like viruses) can pass through. Be cautious when selecting a filter. You should know what potential organisms you need to treat for. You don’t want to go to an area where a virus like hepatitis A is present in the water (a problem in some developing countries) with a filter that will handle only a larger organism like Giardia.

Common microorganisms and the filter size needed:
Organism Examples General Size Filter Type Particle Size Rating
Protozoa Giardia, Cryptosporidium 5 microns or larger Water filter 1.0–4.0 microns
Bacteria Cholera, E. coli, Salmonella 0.2–0.5 microns Microfilter 0.2–1.0 microns
Viruses Hepatitis A, rotavirus, Norwalk virus 0.004 microns Water purifier to 0.004 microns

There are two basic types of filters (descriptions of several popular models begin on the facing page).

Membrane Filters use thin sheets with precisely sized pores that prevent objects larger than the pore size from passing through. Pro: Relatively easy to clean. Con: Clog more quickly than depth filters. Example: PUR-Hiker.
Depth Filters use thick porous materials such as carbon or ceramic to trap particles as water flows through the material. Pro: Can be partially cleaned by backwashing. Activated carbon filters also remove a range of organic chemicals and heavy metals. Con: Rough treatment can crack the filter, rendering it useless. Examples: MSR WaterWorks II, Katadyn.
Note: There is a difference between a water filter and a water purifier. Filters do not filter out viruses, but there are water purifiers, like the PUR Scout, that pass the water through both a filter and an iodine compound that kills any smaller organisms that have passed through the filter. These purifiers kill all microorganisms down to 0.004 microns; however, the filter should not be used by people who are allergic to iodine.

Common Practices for Using a Water Filter
Filter the cleanest water you can find. Dirty water or water with large suspended particles will clog your filter more quickly.
Prefilter the water either through a prefilter on the pump or strain it through a bandanna.
If you must filter dirty water, let it stand overnight for particles to settle out.
Tricks of the Trail

Some water filters come as sealed cartridges, making it impossible to inspect the actual filter cartridge. If the filter takes a serious fall, it could crack internally. If the filter inside cracks, unfiltered water can flow through the crack. Treat your filter with care, and if it takes a significant impact, throw it away. Remember, any intake hose from a water filter has been submerged in unfiltered water. Treat this hose as “contaminated” and keep it in a separate plastic bag.

Boiling water requires heat, which may be from a kerosene stove or dried yak dung, but is often in the form of a wood fire. Burning wood = deforestation in many of these fragile mountainous areas. For this reason I encourage trekkers to enjoy hot drinks in the tea houses, but not ask for boiled water to fill their water bottles. Filters do not do an adequate job of disinfection, and so I see no point in spending money on them or taking up valuable backpack space carrying them. I recommend iodine as the treatment of choice, unless there are contraindications to its use.

My own preference is to use Betadine® (10% povidone-iodine) in a small dropper bottle, and a one liter nalgene bottle. I fill up the bottle from a stream, drop in 4 drops of Betadine®, screw on the lid, and put it in my pack. Half an hour later, it is ready to drink. With minimal planning ahead, I rarely need water faster than this. I like this system because I carry Betadine® in my first aid kit anyway, and I personally think the flavor is less noxious than some other forms of iodine. I don’t usually feel the need to add flavor crystals to my water, rather I joke that iodine is “the taste of safety.” A little goes a long way: 30 ml of Betadine® is enough to disinfect 150 liters of water, or drinking water for about 50 days of active trekking (I am presuming that some additional fluid intake exists from tea, soup, meals, etc.).

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