Portable filters! The life straw is an option, and there are other brands out there. I think the best is something like a berkey. It's a gravity fed, ceramic filter design hat can be used over and over with no special replacement parts. You simply scrub the ceramic and start using again. The only thing I am certain of is getting an intestinal bug while in an emergency is not a good thing, so have a backup for your backup when it comes to water. I was lucky and found a guy that sold me his berkey filter cheap, well 100. bucks isn't cheap, but is a lot less than new. There are other ceramic drip filters out there that are less expensive.