Friday, October 5, 2012

Survival techniques: The Collection and Purification of Drinking Water

In a crisis, our health, safety and wellness may require us to have basic survival skills. The UK Health Radio's "Health Kicks Show" features regular monthly guides to how you can be prepared:

water purification in a disaster

The Collection and Purification of Drinking Water

Rules of survival dictate that shelter and water are the top two priorities in any survival situation whether you are lost in the wilderness or because a natural disaster destroyed your community or city's infrastructure. Shelter can be subjective and in some cases, a person's clothes constitute shelter. Therefore, water is your main priority when you find yourself stranded or lost in the wilderness or in any situation where your water source is suspected of being contaminated with bacteria, pathogens and parasites.

Water Sources

Fresh surface water is any body of water on the earth's surface that is not considered seawater. Sources of fresh surface water include lakes, ponds, rivers and streams. These sources of water must be filtered and purified before they are safe to consume. Ninety seven percent of the water found on the earth's surface is saltwater.

Ground water is any water that originates from beneath the surface such as aquifers, natural springs and underground rivers and lakes. In years past people living in the countryside usually obtained their drinking water from natural springs or hand dug uncapped/open wells. In today's world there are very few if any places on the earths surface that humankind or animals have not tread.

Animals and humans along with insects and naturally occurring bacteria can and will contaminate any water source if they have access to it. Surface water is usually contaminated by ground runoff that contains, pesticides, herbicides, animal and human waste, poorly designed well/spring houses, and poor sanitation measures at the point of collection. Even though the water has been filtered through layers of earth and rocks groundwater can be contaminated at the point of use. To be safe, and if you have the means, you should filter and purify any ground water source if it is to be used for drinking water.

Alternative Water Sources

These sources can be found in various setting to include urban and rural areas. Alternative sources include swimming pools, hot tubs, public fountains, backyard water features, rain barrels used to collect water from roof runoff and cisterns that are filled from rainfall. These sources must be filtered and purified before they are safe to drink.

Waterborne Dangers

Bacteria and parasites that can be present in a water source include Coliform Bacteria, which is not a single strain of bacteria but a group that includes E. coli.  These types of bacteria may not affect all individuals the same depending on their immunity and the strain of bacteria. Cryptosporidium is a parasite that causes cryptosporidiosis and Giardia is another parasite that can be found in water. These are just a few that can be found in virtually any untreated water source, also you will find cholera, typhoid and hepatitis present in many untreated water sources.

 Collection Filtration and Purification

Coffee filters, sand, gravel or clean cotton cloths will remove debris, insects, certain waterborne cysts that contain bacteria and sediment from water. You can obtain sand/silt and gravel from riverbanks, lakeshores and small streams. Once filtered the water can be boiled or chemically treated. Charcoal will remove insects, odour, sediment, debris, pesticides, herbicides, fuels, waterborne cysts and most solvents from the water.

You can make a filtering device from an empty and clean food storage can or large plastic bottle by placing one or several holes in the bottom and layering the filtering medium in the can/bottle. If you must filter into a small opening such as a canteen or water bottle just put one hole in the bottom to better control the flow into a smaller opening. Fill the can or bottle with the activated charcoal/cloth/sand/coffee filters and gravel. You can make your own charcoal by burning hardwoods though, not as effective as commercially purchased activated charcoal, it is nonetheless quite effective at filtering out contaminates.

Note: Activated charcoal is processed in such a way as to increase the naturally porous nature of the charcoal. Typically, activated charcoal used for water filtration is made from coconut husks.

Pour the contaminated water over the filtering medium and allow it to flow into a vessel for boiling or a canteen/container for chemical purification. If you do not have charcoal and have no means to make any, place a coffee filter, clean cotton cloth, sand and gravel in the can. You must always attempt to filter your water before boiling or chemically treating. Sediment, insects and debris in the water will reduce the effectiveness of boiling and chemical treatments.

Purifying Water by Boiling

Filter the water as described in to a suitable vessel. Water must boil rapidly for at least one minute. If you know or suspect your elevation is a mile/1.6km or more above sea level boil for a minimum of three minutes. Boiling will reduce your water volume so keep this in mind if you have a limited water source. To help conserve your boiled water use clean cotton cloths to collect the steam from the boiling water by placing a cloth over the container while boiling to collect steam/evaporated water. Only purified/distilled water evaporates from boiling water.

Tip: You can desalinate saltwater by placing a clean cotton cloth over a boiling vessel of seawater to collect steam. Steam or evaporated water is purified and safe to consume. Once the cloth has absorbed the evaporated water simply, squeeze the cloth into a suitable container for storage. This method is only to be used in emergencies and is not to be considered a substitute for equipment specially designed to make saltwater safe to drink.

Question: Why must you boil water longer at higher altitudes? Air pressure is less at higher altitudes, which means that water will boil at a lower temperature, so water at a rolling/rapid boil at higher elevations is not the same temperature as a rapid boil at sea level. Once you are at about 7,000 feet (1.3 miles or 2 Kilometres) above sea level, for example, water boils at approximately 198ᵒF/ 92.2ᵒC versus 212 Degrees or 100 degrees respectively at sea level. It is important that water reaches and holds its temperature for a certain period to ensure all bacteria, pathogens and parasites are destroyed. A one-minute rapid boil at 212ᵒF/ 100ᵒC destroys all contaminates. To achieve the same effect at 198 or 92.2 degrees respectively the water must maintain its temperature for a minimum of three minutes.

Tip: For every 500 feet/152.5 meters above sea level, the boiling point of water is reduced by one degree.

Purify Water Using 2% Liquid Iodine (Tincture of Iodine)

Ensure the iodine has its own removable, built in dropper, or purchase one separately. When chemically treating water you will need two water containers. One container is used to collect the contaminated water, and once collected the water must be filtered into a clean canteen or container by using the previously described methods. The container used to dip contaminated water will have contaminates around the drink line.  Never drink from the container that was used to collect contaminated water unless the container has been submerged between one and three minutes in boiling water.

The ratio is based on a one-quart/litre container. You will add five drops of iodine per one-quart/litre of water. Once added seal and shake the container well. You must wait 30 minutes before drinking to allow the iodine to work. If the water temperature is below 68ᵒF/20ᵒC or if the water is cloudy after filtering add five additional drops of iodine to the container and allow 60 minutes before drinking. Do not exceed 10 drops of iodine per one-quart/litre of water.

Note: Some manufactures of iodine tablets state in their directions that to purify the drink line, canteen cap and surrounding cap threads you place the recommended number of tablets in the container, seal, shake well, then loosen the cap and tilt the container until water flushes over the cap threads/drink line and fills the cap. You must then allow a minimum of 30 minutes before drinking. Use your own best judgment when determining the safest way to purify the drink line/outer surfaces of your water container.

Purify Water Using Common Household Bleach That Contains 5% Percent Chlorine

Sodium hypochlorite (liquid chlorine) is common household bleach. It typically has as an active ingredient of between 5 and 6% chlorine. Read the active ingredient carefully to ensure the bleach has adequate chlorine content. You must use regular unscented bleach with no other additives. One gallon of bleach can treat up to 3,800 gallons of water. Bleach that has been exposed to extreme temperature variations becomes less effective. Bleach has a shelf life of between four and six months. However, most bleach manufactures produce household bleach with chlorine content between 5.25 and 7%, this allows for some deterioration of the chlorine.

When using bleach to purify water ensure you have a medicine dropper just for the bleach. Never mix iodine and bleach, and more importantly, never mix the two to purify water. The water must be filtered as described earlier and use the two-container method when collecting contaminated water. The ratio is two drops of bleach per one-quart/litre of water. Shake the container well and allow 30 minutes before drinking. If the water is cold or extremely cloudy after filtering, add two more drops for a total of four drops per quart/litre and wait an additional 30 minutes before drinking. Never exceed four drops per quart/litre. The water will have a slight chlorine smell to it, if it has been properly treated. Use vitamin C tablets (ascorbic acid) to enhance the flavour of chemically treated water. Add flavour enhancers after the water has set for the recommended time after treating.


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