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Ultraviolet Water Purification 101

Ultraviolet Water Purification 101

Ultraviolet Water Purification Systems are a popular choice for backpackers because they’re easy to use, fast, lightweight, and don’t leave any aftertaste in your water like chemical treatments. They are not subject to freezing which destroys most water filters and can be used in below-freezing temperatures to purify cold water. Plus they protect you against viruses because they are purifiers and not filters.  But like all backcountry water treatment solutions, ultraviolet water purification has its PROS and CONS, and is not suitable in all circumstances.

ModelBatteriesLiters Treated / Batteries or ChargeWeight w/ Batteries
Katadyn Classic 3AA (4)Lithium: 1506.3 oz.
Katadyn UltraUSB-onlyFull Charge: 504.9 oz.
Katadyn Opti AdventurerCR123 (2)CR123: 503.8 oz.
Katadyn AquaAAA (4)Alkaline: 50
Rechargeable: 100
6.2 oz
Katadyn Ultralight UVUSB Rechargeable: 20Full Charge: 202.6

What kind of contaminants occur in backcountry water?

Backcountry water can contain two different types of contaminants that can make your ill: biological organisms and mineral or chemical contaminants, including agricultural or industrial runoff. Not all sources or regions suffer from both, so it’s best to do some research about water quality and the need to treat your water before hiking or backpacking in a new area. Contacting the National Park Service, US Forest Service, or state authority that administers the land is usually a good place to start. Local guiding services and hiking clubs are also useful sources of information.

What kinds of contaminants is an Ultraviolet Water Purifier effective against?

Ultraviolet Water Purification protects you against many microscopic biological contaminants, including:

  • Viruses, including Hepatitis, Norovirus, and COVID-19.
  • Bacteria, including Campylobacter, E. Coli, Salmonella, and Shigella.
  • Protozoa, including Giardia and Cryptosporidium can cause severe diarrhea. Giardia, often called beaver-fever, is the most common form of non-bacterial diarrhea in North America. There are over 1 million cases of Giardia reported in the United States each year with the highest rate of occurrence in New England and Alaska, according to the CDC.
The SteriPEN Adventurer Opti Ultraviolet Water Purifier
The Katadym Adventurer Opti Ultraviolet Water Purifier

What about mineral or chemical contaminants and industrial pollution?

Ultraviolet Water Purifiers do not neutralize or remove mineral or chemical contamination from agriculture and industry, including herbicides, pesticides, and fertilizers. There isn’t any good way to remove these contaminants from natural water sources using a portable device, including pump filters. Boiling and distilling water is one method although it’s very fuel intensive. Your best bet is to consume bottled water or avoid areas where these contaminants are present.

How do Ultraviolet Water Purifiers Work?

UV Water Purifiers are ultraviolet lights that you immerse in a bottle of water. Rather than removing biological contaminants including viruses, bacteria, and protozoa, they kill their DNA so they can’t reproduce if you ingest them. If they can’t reproduce, they can’t make you sick by overwhelming your digestive or immune system. It’s a subtle but important difference.

What water bottles are Ultraviolet Water Purifiers compatible with?

UV Purifiers (including Katadyn’s and Steripen Brand Purifiers) work with a wide variety of bottles and containers, but be sure to read the directions that come with your unit or contact the company if you have any questions. While they do work with hydration reservoirs it’s important that you not try to purify more than one liter of water at a time, since most hydration reservoirs are larger than one liter. It’s also important to separate the tube from the reservoir at the time of treatment, otherwise, water can flow back into the tube, avoiding treatment. When in doubt, your best bet is to use an Ultralight Water Purifier with a wide-mouth half-liter or one-liter bottle from Nalgene, which is sure to work. You can also use a cooking pot or even a plastic bag as a container.

Does a UV Purifier treat water left on the bottle threads?

When you fill a bottle in a pond or stream, some of the water is bound to adhere to the bottle cap threads, and this water will not be purified. Dry the bottle threads with a towel before drinking. Even then, there’s still a risk that microscopic organisms will remain. Most people have a strong enough immune system that they can resist a small dose of organisms if any are present. The same can’t be said if you were to ingest a full liter of contaminated water. If you have a compromised immune system or it’s still a matter of concern, you can use a container that does not have bottle threads like a cookpot instead and pour the purified water into a water bottle to avoid the issue entirely.

How much water can you purify with an Ultraviolet Water Purifier?

The number of liters you can purify varies by model, as shown in the table below. While the battery life is generally good, it’s worthwhile to carry backup batteries or a USB recharger in case your unit runs out of power during a trip. For units that require AA batteries, I recommend using Lithium batteries because they will not freeze.

Neutralizes biological organismsDoes not work with all bottles or reservoirs
Very fastBattery dependent
Non-mechanical, no pumpingDoes not remove chemical or mineral contaminents
Effective in cold or freezing weatherNot effective with cloudy or murky water
Does not affect tasteDoes not neutralize larger organisms, i.e. worm eggs

Can an Ultralight Water Purifier neutralize tapeworm eggs?

Most of the UV Water Purifiers listed above have not been tested against worms eggs. I would suggest you play it safe and use a filter instead.

Can you only use a Katadyn Ultraviolet Water Purifier to purify clear water?

A UV Water Purifier should only be used to treat clear, non-murky water, without floating sediment. Use a pre-filter to clarify water if it is murky or let it sit and settle out.

What about reddish, highly tannic water?

If the water has a high-tannin concentration, Ultraviolet Water Purification will not be effective. 

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