Water purification

From WildernessWiki.org

Clean, drinkable water is essential in all outdoor situations, from a two-hour hike to long-term wilderness survival. Since it is not always possible to carry a sufficient supply of water, It may be necessary to take water from streams and lakes, or to collect rain or evaporated water. Any water collected in the outdoors could be contminated with bacteria, parasites, and particulate matter, so all such water should be purified before it is used for drinking or cooking. Because of the multiple forms of contamination, it is usually best to both filter and sterilize your water.

1 Signs of bad water
2 Purification methods
3 Waterborne diseases
4 References

Signs of bad water

Even with purification, some water sources are obviously contaminated and should be avoided except as an absolute last resort. There are a number of signs for recognizing water that is unfit to drink.

The absence of flora at the waterside.
An overwhelming amount of green algae on the water's surface.
Powdery deposits at the waterside, an indication of possible chemical pollution.

Purification methods

Boiling

The most basic method of water purification, boiling water will kill most pathogens. Bringing water to a full boil will kill, destroy, or inactivate nearly all sources of organic water borne disease. However, some microbes form protective cysts and ten minutes of a full boil is necessary to kill these much more rare organisms, and guarantee water to be perfectly free of harmful microbes. The boiling point of water decreases at higher elevations, so extra boiling time is required to be sure all organisms have been killed.

Unfortunately, boiling water only deals with organic contamination, and does nothing to remove particulate matter.

Purification tablets

Water purification tablets use chemicals to kill microorganisms and to counter other contaminants in the water. The purification process usually involves dropping one or two tablets into a quart of water and waiting for at least half an hour. More time should be allowed for purification of cold water.

Purification tablets are often sold in small bottles sized for hikers and campers. Unfortunately, the effectiveness of the tablets begins to decline after the bottle is opened, so it is necessary to be aware of the expiration date on the label and to only use fresh tablets.

Another downside of water purification tablets is that they can leave a chemical taste in the water. The flavour can be improved by adding flavoured drink mix to the water after purification is complete.

Because of their convenience and small size, it is a good idea to add a few tablets to a personal survival kit.

Filters

Most places that sell camping and outdoor gear offer water purification filters. These systems are effective and easy to use by hand, purifying the water by pumping it through a fine membrane to strain out the bacteria, or through cemical and carbon filters.

Basic (non-chemical) filters are fine enough to strain out bacteria, but often leave viruses, so disinfection by chemicals may be required after filtration. Water filtration systems should be properly cared for according to their instructions; it may be necessary to clean or replace the filters. Anyone using a purification filter should also carry purification tablets, in case the system malfunctions.

Waterborne diseases

Disease	Cause	Symptoms
Amebic Dysentery	infected sewage contamination in drinking water	diarrhea with blood and/or pus, colon infection
Giardiasis	parasitic Giardia from infected urine or feces in water	diarrhea, abdominal cramps, nausea
Hookworms	parasitic larvae entering body via drinking water or the skin	anemia and lethargy, pneumonia if in blood
Leptospirosis	bacterium infecting animal urine or body parts	fever, chills, headache, muscle pain (flu-like symptoms)
Schistosomiasis	freshwater parasitic worm, or parasites in freshwater snails	itching, asthma, urinary tract irritation, liver enlargement