All this talk about filters and chemicals. UV is the only practical method as it takes care of all the baddies. Boiling is also good, but time consuming.
Of course you must pre-filter if the water is turbid when using UV, but who is not going to do that anyway. If you don't pre-filter turbid water, you plug up your pump filter. If you don't filter before using chemicals, you slow the process and also the water will be yucky to drink.