The reason I mentioned the two I did is that Chip Rawlings spent considerable time working for a government agency (USFS? - I'm too lazy to go look it up) taking water samples, and Ryan Jordan is a scientist (or engineer) who specializes in water science of one sort or another (again, too lazy to go find specifics.) Other than those, I don't trust audthors, either (and, without Rawlings, would not have recommended St. Colin - though it was Fletcher who memorably defined giardiasis as "the feeling that the bottom was falling out of your world, and vice versa.")

The best advice I ever got on water treatment was a phone converstation with the ranger who was responsible for water quality monitoring at Isle Royale - he was knowledgeable, and I was smart enought to sit back and listen.