I think I would use the "Aqua- pouch" by survival resorces.

http://www.bepreparedtosurvive.com/WaterPurificationProducts.htm

you get a filter and sterilizer and a carry bag in one Item.
_________________________
Some people try to turn back their odometers.
Not me, I want people to know "why" I look this way
I've traveled a long way and some of the roads weren't paved