Check out the Livesaver walter filtration system or do some online research about it. The US military has been using these for a couple of years now, they are a little pricey, about $150, but are well worth it. You can literally use water from a mud puddle and have clean drinking water in a minute. The filter lasts a long time and they are simple to use, not a bunch of pieces, pumps, hoses, etc. They are worth a look if you are considering the investment in a walter filter system IMHO.
LBR