Ultralight Water Purification
Up until this year, I have always carried Micropur chlorine dioxide tablets for water purification in my emergency repair kit, in case my 16 oz First Need water purifier crapped out on a backpacking trip. I even got to use them for a few days during my 100 mile wilderness trip last summer when my purifier clogged and I ripped a hose.
But when I went hiking across Scotland this spring, I left my First Need and a British inline purifier I’d started using recently behind, making the switch to chlorine dioxide tablets as my primary water purification method. (On hindsight, I should have further filtered my water after exposing it to chlorine dioxide using an ultralight filter like the Aquamira Frontier Pro which can remove cyrpto [see comment stream below].)
I did this to reduce pack volume and weight. This is a pretty significant change in my hydration system and preferences, but one I’m a lot more comfortable with as my backpacking experience level has evolved.
Water Filter and Purification Limitations
When it comes to water filtration or purification, there are no absolutes. Each method has it’s pluses and minuses depending on water temperature, turbidity, and local industrial or biological contaminants.
- SteriPENS and chemical purifiers are less effective when your water has a lot of suspended solids.
- Chemical purifiers take longer to work in very cold water and chlorine dioxide takes a full 4 hours to kill a hardy protozoa named cryptosporidium.
- Boiling requires that you carry extra fuel, but works the best with snow.
- Iodine tablets don’t kill cryptosporidium.
- Filters that use activated carbon don’t remove viruses.
- Pump based filters and purifiers are heavy to carry and are prone to cross-contamination.
- Inline or gravity filters can be slow and require that you carry extra water, hosing and reservoirs.
- Most methods, except a First Need purifier, don’t remove industrial pollutants or fertilizers
REI has an excellent article on How to Choose a Backcountry Water Treatment System if you want more info on this topic.
Chemical Water Purification
Most of the places I hike in New England have clear, low turbidity water supplies (streams, lakes, and springs) but there are protozoa and bacteria in the water supply, requiring backcountry water treatment. Chlorine dioxide tablets are an excellent lightweight alternative here for 3 season backpacking. I use Katadyn Micropur tablets, but Portable Aqua Chlorine Dioxide Tablets are also available.
Each Micropur tablet comes in its own waterproof foil compartment, 10 tablets per sheet. You need one tablet per quart (liter) of water or about 5-6 a day: a package of 30 tablets weighs under 1 oz, which is absurdly light
The tablets will crumble if smashed, so I pack them carefully because it’s easier to add the tablet to a bottle of water than powder, though the powder is no less effective.
The foil wrapped tablet compartments can be difficult to open by hand or with your teeth, so I open them with the small pair of scissors on my Victorinox Swiss Army Classic knife. I can’t hike without these scissors – there are useful in so many ways.
Treatment Time and Effectiveness
Chlorine dioxide tablets take 30 minutes to kill a protozoa called giardia and bacteria but can take up to 4 hours (or longer) if your water is turbid with suspended particles or very cold. In such cases, boiling for a few minutes may be the only way to quickly purify it without a filter. Chlorine dioxide also kills a second common protozoa called cryptosporidium, but requires 4 hours of contact.
Cryptosporidium is widely distributed in the ecosystem and not waiting the 4 hours required to kill it is a risk. One way to mitigate this risk is to filter out cryptosporidium using a filter such as a 2 oz Aquamira Frontier Pro that is threaded to screw onto narrow necked plastic water bottles.
When using tablets, my routine runs like this: I try to drink 16-24 oz of water per hour in hot weather depending on my exertion level. That works out to about 1 quart (liter) every 2 hours. I carry a 1 quart recycled water bottle with a 2 or 3 quart platypus reservoir for camp or as a reserve if I need to carry more water between water sources.
If I’m only carrying a quart of water at a time, I finish the remaining water in my bottle when I come across a new water source, refill it, drop in a chlorine dioxide tablet, and make a mental note of the time. I carry my water bottle in an external mesh pocket on my backpack, where it will rapidly warm up if cold. This system works well because I’m not thirsty, waiting for water to purify, after a refill.
Some people complain that water treated with Chlorine dioxide tablets tastes bad. To tell you the truth, I can’t taste any difference between it and normal bottled water. That makes sense, because the concentration of chlorine in bottled water or municipal tap water is the same. Adding an activated carbon filter like the Frontier Pro will improve the taste and further protect you against micro-beasties that require a longer exposure time to chemical purification.
Disclosure: The author owns this product and purchased it using their own funds.
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