Chlorine dioxide treatments like the Water Treatment Drops from Aquamira are one of the lightest and smallest water treatment methods, making this system perfect for an emergency water treatment method or weight-conscious hikers. We considered giving this treatment method a Best Buy award because it is so economical, but overall it is such a useful and simple method that we decided it was worthy of our Top Pick award for being light AND inexpensive.
Unlike iodine chemical treatment, chlorine dioxide is not harmful to ingest regularly and does eliminate Cryptosporidium, and unlike most pump filters, this method eliminates viruses. Besides the long incubation time, the primary downside to this approach is that it involves adding chemicals to your drinking water, which puts off some users. If you want to protect yourself against viruses but don't like the idea of chemicals in your water, check out the MSR Guardian, which is the only filter effective against those types of diseases, though it is much more cumbersome and expensive.
The Water Treatment Drops by Aquamira and MSR AquaTabs are inexpensive for a single package, which is helpful for the wallet at the outset. If you travel in the backcountry often, a long-lasting filter such as the MSR Miniworks EX or the Sawyer 4L Water Filtration System would be a better value, although they are not capable on as many pathogens. Another option and one that only costs $20 is the LifeStraw. It weighs just 2.7 ounces and allows you to hike without carrying as much water (as long as you are 100 percent confident you will come across water).