I am thinking about buying the Katadyn Combi with some replacement filters. I like that is has a ceramic and carbon filter but what I don't know is will something like this only work well for clear spring water that needs to be filtered or will it work on pretty much any type of water? For example could I use this to filter brown river water that may have chemicals and other pollutants in it? Amazon.com: Katadyn Combi Water Microfilter: Sports & Outdoors If this filter can filter out 50k gallons of clear water how many gallons of crappy river water can it filter? What do you guys use for a water filter? Are there better filters that do a better job of filtering dirty water for about the same price? I like the fact that it is portable so I could use it for emergencies and camping, although I am open to more stationary units if they work better. The main thing is clean drinkable water in the event of a long term emergency. What about water polluted with radiation like from a bomb, is that another beast or will filters like this work? My main reason for getting one is for emergencies and survival if, God forbid, the need ever arises. Thanks for any help and advice you can offer.