Know How

Hydration and Nutrition : Water Filtration and Purification

Sarthak Madan

Last updated: 05-11-2018

Bikat's HYDRATION AND NUTRITION series provide information about techniques for backcountry hydration and cooking. This is the first article in the series.

Hydration is one of the most important requirements during long periods of exertion in the outdoors. Unfortunately, water sources in the backcountry are often contaminated and unsuitable for human consumption. Apart from debris, sedimentation and wildlife excrement, water can also contain protozoa, viruses, and bacteria. 

Here we will discuss how to collect, filter and purify water in the backcountry.



  • Flowing Water: The best option is to collect water from a flowing stream or waterfall. Since the water is continuously flowing it doesn’t allow sedimentation, the growth of algae or accumulation of microorganisms. In addition, mosquitos don’t lay eggs in flowing water.
  • Clear Water: If flowing water isn’t available, look for lakes or pools without a lot of sediment. Clear water will not clog your filters. Avoid collection from the shore, where microorganisms accumulate in high concentration. Gather from the surface.
  • Avoid collecting water near meadows or pastures which are used as animal grazing grounds.
  • Avoid collecting water from locations that show high human activity.
  • Don’t assume snow is a source of clean water. Bacteria can live in snow and ice for months.
  • Use a pre-filter during collection (like a clean bandana or a piece of cotton fabric), to remove sediment that might clog your filters.


Hydration and Nutrition : Water Filtration and Purification



Water filters remove sediment, bacteria, and protozoa by physically filtering out the elements through small pores. You might want to wish to use a pre-filter, like a cotton cloth, to remove sediment as it may clog the pores of the filter. Filtration does not remove viruses, dissolved solids, and chemicals, though some filters may reduce the amount of chlorine.

  • Suction or squeeze filters like Lifestraw - some work by squeezing an attached reservoir will others work by suction through a bite valve. The disadvantage is that water can be purified only the source.
  • Filtering bottles like Lifestraw Go, Sawyer and Bobble - similar to suction or squeeze filters but incorporated into a bottle, which allows filtration beyond the source as well.
  • Gravity filtration - This involves filling a reservoir with water and hanging the reservoir at a high place. The reservoir is connected to a pipe with an inline filter. This is suitable for large groups, although it is time-consuming.
  • Pump filtration - These devices consist of an intake source that is dropped into the water source and an outlet that you attach to a reservoir or bottle, and then work the pump to extract water, which is filtered inline. The advantage of this method is that water can be drawn from very shallow pools. However, it requires time and effort and is heavier than other options.


Hydration and Nutrition : Water Filtration and Purification



Purification is the removal of viruses from water. In addition to filtration, you will also need to purify water from sources you suspect to contaminated with viruses, like those infested by mosquitos.

The following options are used for purification

  • UV Light - You can use a pen-style UV light purifier. Place it in the water source, turn it on and stir for a minute. UV light kills all viruses.
  • Chemical Treatment - Chemical treatments are typically iodine or chlorine based, available as powder, pill or drops, and effective against all protozoa, bacteria, and viruses. Add the appropriate amount to the water and wait for 30 minutes.
  • Boiling - This is the simplest method. Boiling kills the entire spectrum of biological pathogens. Boil water for a minute at low altitudes, and three minutes at altitudes above 3000 m. However, this should not be used as your primary purification method since you will require a lot of extra fuel. Use it as a backup.


Hydration and Nutrition : Water Filtration and Purification

Sarthak Madan

I work with Bikat Adventures as an expedition leader and technical content writer. Sometimes, I fly. Read more

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