I have used the following:
Tincture of iodine........brilliantly effective but has a slight taste, and shouldn't be used for long periods (your body has a limit as to how much iodine it should ingest in a lifetime).
Puritabs..........very good, but not 100% effective apparently (I've never had a problem).
Portable hand-pumped ceramic water filter with charcoal......you can drink camel pee after 30 seconds of pumping this little pump. It is brilliant, but hard work, and the ceramic cartdriges are expensive and fragile.
Due to overdosing on the first, I now stick to the latter 2 methods......and in all my years of travelling, all over the world, I have never had the trots or any upset stomach. You need the kit, and you need discipline.
"A poxy, feral, Brit architect who drinks bad beer and supports the wrong rugby team." Tony Weaver
"Mike for President" Freeflyd