When I read threads like this, I just shake my head, turn on the stove, and bring the pot to a boil. I need to carry a bit more fuel, but boiling takes care of all the pathogens. I am beginning to suspect that it isn't really necessary to bring the water to a boil (milk is pasteurized at 165 degrees F). I also don't bother at all if I am isolated and well enough upstream. Boiling works for me because the highest and best use of water is to prepare a nice cup of tea.....