Problem I found with UV filters is that the bulbs are pretty friable, they're battery hungry, they're container specific (it's a pretty weak source of UV with penetration in the water column of a couple of centimetres, for sitting stationary in a stndard size 1l nalgene bottle say it wont purify the edges or the bottom without gentle slow aggitation). They really are meant for travellers for treating tap/bottled water of suspicious origin, not for outdoors water.
An osmosis filter is generally someting to remove dissolved chemicals like salt, generally found inlifeboats to give fresh water from sea water.
Of most use to most outdoor folk who're really worried about water would be either some form of purifitation tablet/liquid. Again the water has to be pretty good quality (not too much in particulate matter) mainly chlorine or (harder to get now as it has long term use drawbacks) iodine based. Pretty temperature dependant on purification times.
Some sort of chemical and particulate folter is best. These can either be in the form of a bottle/straw/gravity fed or fitted with a pump and use a mix of chemicals, sometimes with an end point charcoal filter and either ceramic or otherwise microfilter that takes out all the little bugs. You can get some quite high flow rates if you're going through a lot of water.
Remember most folk get sick when using some sort of purifier from treating the water inside their bottle but not realising that theres untreated water on the bottle lid/treads
You also get ion treatment best I give you a
LINK as there's a lot to explain.
For good reading on the subject and worth every outdoors person reading in MHO is "How To **** In The Woods" by Kathleen Meyer. Great section on water treatment and outdoor health in general. You'll pick it up for about a tenner.. If you've any specific questions let me know, there are also some camp based methods like millbank backs and all sorts of other Heath Robinson contraptions for water treatment but you have to ballance portability/price/water treated volume/effectiveness/and source water quality to see what you need. Or you could just boil it.
Cheers,
GB.