I assume that when you have found a treatment to be effective, it means that you, or your party, did not suffer any ill effects.

If that is the case , I would have to state that no treatment works just fine, because I have drunk untreated water for many years, with no discernible ill effect. I have been lucky, and a lot of my drinking was in the early days, with much less traffic in the back country, and I was drinking from isolated springs and the upper reaches of watersheds.

I have heard of a study which concluded that most cases of giardia, etc. were the result of poor peersonal hygiene, rather than contaminated water.

Older and wiser (?) now, I am more cautious....