Backcountry streams may look crystal-pure, but they often harbor microorganisms that can make you sick. Whether you’re surviving a plane crash or out in the wilderness deliberately, you need water purification. There are a lot of water purification methods available. Today we’ll talk briefly about them, and see some examples.
What’s the problem with the water?
A lot of microscopic creatures can live in water that looks clear to the naked eye, and most water in the wilds harbor at least some. If you drink untreated water, you will ingest them. Some of these organisms can colonize your intestines and cause a lot of misery. There are three general classes of them.
Protozoa are the largest of the lot, at 4-20 microns in size (one micron is 1/1000 of a millimeter). They show up in water just about everywhere.
Bacteria are smaller, at 0.3 to 2 microns. Like protozoa, you can find them in just about every body of water
Viruses are smaller still, at 0.02 to 0.1 microns. Harmful ones mostly only occur near human presence. Viruses aren’t a threat in the wilderness, but would be a threat for urban survival situations.
Water Purification vs. Water Filtration
A water purifier can eliminate or incapacitate all three threats: protozoa, bacteria, and viruses. A water filter can remove protozoa and bacteria, but typically not viruses. Which you need really depends on where you’ll be. In the backwoods, a filter will suffice.
Water Purifiers
These products kill or incapacitate viruses, protozoa and bacteria
Chemical treatments
Pros: Small and compact, kills everything (eventually)
Cons: Takes 35 minutes to 5 hours standing time (depending on the tablets) to be effective on protozoa. Some types of tablets add objectionable tastes to the water.
Ultraviolet (UV) Treatment
These use UV light to inactivate the bacteria, viruses, and protozoa. The creatures aren’t removed, but they’re rendered unable to reproduce and colonize your gut, and therefore unable to make you sick.
Pros: Very effective, quick (90 seconds). Takes care of viruses, so it’s useful for emergency preparation and international travel.
Cons: Requires batteries (some recharge via USB instead). You could break it if you drop it.
Water Filters
Backpacking water filters feature a filter medium with pores that are 0.2 microns or smaller. Consequently, they will filter out bacteria and protozoa, but not viruses. You can drink the water from a filter right away, which is a huge advantage over chemicals. You can find many models of filter, but they all fall into one of three categories.
Pump filters
Pump filters use a pump to draw water from the stream or other source and force it through the filter. Periodically you will need to clean them to restore flow. Eventually you’ll need to replace the filter element. They tend to be heavy but they’re great for larger groups.
Gravity Filters
Gravity filters use the force of gravity to draw water from a dirty water reservoir, through the filter, and into a clean water container. You clean them by reversing the flow. They aren’t super fast, but you can do something else while the filter runs. They’re also great for larger groups.
Squeeze Filters
These filters consist of a filter element that attaches to a flexible container full of dirty water. As you squeeze the container, water is forced through the filter and out the other end, where you can collect it.
These filters are best for small groups (1-3 people), but they are very light and compact, and last a long time with proper care.
As you can see, there are a lot of options for water purification. Hopefully this helps you make sense of it all, and makes it easier to choose the one that’s right for you. Thanks for reading!
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