Not to threadjack here, but I am curious about this as well. The UV pens seem ideal to me because of weight and durability reasons. When it is said the water needs to be clear to be effective, is that the sense that it will take longer to purify sediment laden water, or it simply will not do it?

I have mainly done day hikes, and all of my extended excursions involved a vehicle, so packing water is the only thing I am familiar with at this point.