Woundn’t you need something like chlorine tablets or very small amounts of bleach to preserve the water for a long time?
Better than Bleach: Use Calcium Hypochlorite to Disinfect Water
http://survivaltopics.com/better-than-bleach-use-calcium-hypochlorite-to-disinfect-water/
There are also several excellent water filter systems Katadyn, Berkey and I have heard good things about Sawyer especially price wise.
I have a small portable Katadyn as well as a Berkey filters which I installed in a DIY bucket filter system.
http://www.survivalistdaily.com/how-to-make-a-berkey-water-filter/