In the quest for pure water, even the most ideal techniques of primitive hydration collection can result in water that is contaminated with microbial pathogens. When the risk is just too great for drinking bottles of bacteria or vessels of viruses, treatment is necessary.
Though many forms of treatment exist today that can be used by backpackers to procure sterile water, one method is both ancient in its origin and reliable in nearly any environment. This was alluded to by our one and only @alexander.alexis in his perceptive reply to the primitive hydration post. For those of you who neglected to read the title of this post, the treatment technique we are discussing today is known as boiling.
The process of boiling water is one that we should all be intimately familiar with. It is not only used to purify what we drink, but is also used in cooking dry foods like rice and pasta. All it takes is some water, a heat source, something to contain the water while it boils, and a little patience.
This fire needs more fuel. Image modified from Source
Fuel the Fire
It does not matter what the source of heat is so long is it burns hotter than 100 degrees Celsius (the boiling temperature of water at sea level). Historically, humans have harnessed the power of fire by burning wood, peat, coal, oil, and other biological fuel sources.
A very cute concept. Image modified from Source
If you are hiking in a forest, wood and grass are both going to be a good bet - coal, peat, and oil generally need to be mined and they can only be found in certain places. There are also landscapes that are largely devoid of fuel sources (such as tundras, deserts, and alpine environments). When journeying through these areas, it is advisable to carry a condensed fuel source such as white gas, compressed butane propane blends, alcohol, or a solid fuel tablet.
There ain't much for burnin' in these parts.
Vouch the Vessel
In addition to a good heat source to boil the water, it is necessary to have some sort of vessel or container that can hold the water while it is heated and boiled. There are a wide variety of stainless steel, aluminum, and titanium cookware for the modern backpacker to replace the heavy iron pots of yesteryear.
Time to do the dishes. Image modified from Source
If you want to go more traditional, water can be boiled in a wooden vessel or a clay-lined pit by using a technique of transferring heat through stones. Simply cook the rocks in a fire for a bit and then transfer the stones to the vessel. The stones will locally heat and boil water, and with enough rocks the entire vessel can be boiled and made safe to drink.
In order to ensure that this method of water treatment effectively destroys all microbial threats, you must be patient. It is advisable to bring water to a full rolling boil for at least one minute in order to have confidence that all of the potentially harmful microbes have been killed. With the exception of some extremophiles, microorganisms generally cannot survive temperatures higher than 60 C.
This boil is rolling. Image modified from Source
Let It Chill
One of the biggest downfalls of the boiling method of water treatment is that the water is not immediately drinkable. This might be a good thing if you plan to cook or make a hot beverage with the water, but if the weather is warm and you just want a cool, refreshing drink, you will have to wait a considerable amount of time for the water to equilibrate with the ambient air temperature.
A seriously addictive drug. Image modified from Source
Boiling in Summary