How it works: A chemical used in many public water supplies, chlorine dioxide breaks down cell walls to kill pathogens
Pros: Like iodine, it’s cheap and easy to carry, with no taste—or just a vague chlorine taste. Chlorine dioxide can also improve the taste of water by breaking down odor-causing bacteria.
Cons: Wait time. Chlorine dioxide can work in 15 minutes, or it can take up to four hours if your water is murky or extremely cold. And, organic matter needs to be removed separately.