The Collection And Purification Of Drinking Water

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Collect & Purify Water

According to the United States Geological Society (USGS), 70 percent of the earth’s surface is covered in water. Of that 70 percent, roughly 97 percent is seawater (saltwater). This means that only three percent of the earth’s surface water is considered fresh water (USGS, 2013).

Saltwater cannot be consumed unless the water is desalinated and the process is complicated and costly to do on a large scale. Therefore, the world’s population for the most part must rely on the three percent of fresh water on the earth’s surface for their drinking water.

Just because water is called fresh water does not mean it can be consumed before it is properly filtered and purified. Any surface water source is called fresh water if it is not seawater.

Ground water is also considered a source of drinking water and people do use wells and natural springs as a drinking water source. Generally, ground water sources such as private wells do not need to be purified before consumption and usually do not require inspection or verification of purity. However, anyone that has a well should test their water periodically and ensure it is properly capped so contaminates cannot enter the well from the top.

Typically, cities and towns collect drinking water from man-made reservoirs, rivers and lakes. Once the water is collected, it is processed though a water treatment plant. The processing plant will filter and then purify the water usually using chemicals such as sodium hypochlorite (liquid chlorine) and then pipe it to residents connected to the system.

The average person needs to consume at least two quarts/liters of water daily just to sustain life. Coffee, teas, certain fruit juices, sports drinks, and even some foods all contribute to daily fluid intake during a normal day. In hot weather where a person sweats heavily, the fluid intake must increase significantly to prevent dehydration, which is fatal if not treated. The average person cannot go longer than 72 hours without adequate fluid intake.

Water must be a priority in every situation and if you find yourself lost or stranded in a wilderness environment you must have the knowledge and materials to collect, filter and then purify a surface water source to survive. In a survival situation where you are physically active and the weather is warm, you may need one gallon/four liters or more of clean drinking water daily to prevent dehydration.

Surface Water Sources

Sources in a wilderness environment include streams, rivers, lakes, ponds and cisterns filled from rainfall/ground runoff. Surface water sources in an urban environment can include public and private swimming pools, hot tubs, water fountains, and public lakes and ponds typically found in city parks.

Bacteria Pathogens and Parasites in Water

Surface water is contaminated by animal and human feces, animal carcasses, insect and waterfowl.

Coliform is a group of bacteria, which contain the E. coli strain, which to some people can be deadly. The bacteria live in the intestinal tracts of animals and infected humans. The bacteria can also be found naturally in the soil and in certain plant life

Giardia Lamblia is a protozoan (single cell) that is parasitic in nature and it lives in the intestines of animals and humans. Humans are exposed to the parasite by consuming contaminated water sources.

Cryptosporidium parvum is a protozoan parasite that causes cryptosporidiosis and it is found in surface water as well. The parasite lives in the intestines of animals and typically ground runoff into rivers, streams and lakes carries the animals fecal matter, which is contaminated with the parasite.

The above mentioned are just a few of the contaminates that can be found in surface water sources, and to make the water safe to drink it must be filtered and then purified either through boiling or chemical purification. You have to assume that any surface water source in the wilderness or otherwise is contaminated and to safeguard your health you must properly treat the water before consumption.

Water Filtration

First, you must keep in mind that typical filtration devices do not destroy contaminates, they can only remove certain ones. Filtration mediums include activated charcoal, traditional hardwood charcoal, sand, gravel, coffee filters, cheesecloth and pieces of cloth. In a survival situation, you can use whatever material is available, such as charcoal from your fire, sand, gravel and pieces of clothing.

Water Filter

The illustration depicted is a two-liter plastic soda bottle with the bottom portion removed. Use the cap end to filter the water into a container for boiling or chemical treatment. Layer the filter mediums with the densest at the bottom. The less dense materials will remove the larger particles from the water such as insects and debris. As the water flows through the finer material, smaller and smaller organisms are removed. If you where to reverse the order of materials, the finer material would become clogged with the larger debris and possibly not remove some contaminates.

It is important that you filter the water before treatment to remove waterborne cysts. Cysts can be described as micro sized seedpods that harbor bacteria inside them. Because of the nature of the cysts, they may protect the bacteria from boiling or chemical treatment, but they can be removed from the water through filtration.

Water Purification by Boiling

Filter First

Air pressure has an effect on water temperature and higher elevations have less air pressure, which results in a lower boiling point of water. At one mile above sea level, water boils at 200ᵒF/93.3ᵒC whereas at sea level water boils at 212ᵒF/100ᵒC. Lower boiling points of water means it has to boil longer to destroy all waterborne contaminates. At 212ᵒF, water must rapid boil for at least one minute. If you know or suspect your elevation is 500 feet or more above sea level rapid boil for three minutes.

Boiling for longer than the recommended times will not increase the purity of the water. Boiling for longer periods may result in loss of water through evaporation. You can boil your water source dry of you allow it to boil too long.

Bacteria, pathogens and parasites begin to be destroyed at between 145-165ᵒF (62.7-73.8ᵒC). For all contaminates to be destroyed you would have to maintain this temperature range for at least one hour. If you have a container that cannot be placed over direct heat, you can essentially pasteurize the water using these temperature ranges.

Place the water container close enough to the heat source for the water to be heated and yet does not destroy the container. As a reference because you probably will not have any way to measure the water temperature, hot water from your tap usually ranges from 120-130ᵒF.

Common Household Bleach for Water Purification

Filter First

Household bleach contains sodium hypochlorite (liquid chlorine), which can be used to purify drinking water. The bleach must contain between 5.24 and 6.0 percent of sodium hypochlorite as its active ingredient. The bleach must not contain any additives.


Filter the water from the collection container into a clean container before adding the bleach. The collection container will have contaminates on the exterior, in particular around the drink line which means it is unsafe to drink from the collection container until it has been properly disinfected. The ratio is eight drops of bleach per one gallon of water. To convert to quarts divide by four, which means you would add two drops per quart/liter of water. After you have added the drops, seal and shake well and wait at a minimum 30 minutes before consuming the water.

If the water looks cloudy, even after filtration double the drops and the wait time. If an eyedropper is not available, you can use a clean narrow strip of paper dipped in the bleach. Dip the strip and allow the bleach to form drops on the end. You can also use other material but practice with the materials before you have to purify a water source so you are confident you can perform the task.

If you only have one container you can sanitize the drink line by treating the water and then loosening the cap and tipping the container to allow the treated water to flow over the threads or lip of the container as well as the cap.

Using Two Percent Liquid Iodine (Tincture of Iodine)

The iodine container will usually have a dropper attached or a “drip stick”, which allows drops to form on the end. Use the previously described methods of filtration and collection before adding five drops of the iodine to a quart/liter of water. Multiply the five drops by four to treat water by the gallon and simply convert up if treating larger volumes of water. You must wait 30 minutes after treatment before consuming. You can double the drops and double the wait time if the water you are treating is extremely cold or contains high amounts of sediment even after filtration.

Before consuming iodine, treated water consult with a medical professional if you know or suspect you have thyroid issues, are nursing or are pregnant. No one should consume water treated with iodine for longer than 14 days at a time. The information provided is for informational purposes only and should not be considered medical advice.

Water Purification Tablets

Follow the label directions carefully because they vary depending on the type of tablets and manufacturer. Certain tablets are designed for specific bacteria and pathogens in some cases, so make sure you read carefully and know what to expect when using the tablets. In some cases, you will have to wait up to four hours after treatment before consuming the water.


USGS. (2013, March). Retrieved from


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