I've used the biox drops in Sweden to treat water for a large group (16+) they seem to do the job as there were no outbreaks of dehli belly!! The downside is that they are a bit fiddly in comparison to chlorine dioxide tablets. But they are of course cheaper. The other downside is that you are transporting liquids and should they leak well its a pain, you can also split tablets and keep them in different locations so if you lose any, you still have some left, where if you lose one of the bottles or both then you are stuffed.
daryl