You should have a Sawyer Mini water filter in your emergency supplies.
As a life-long camping gadget freak, the Sawyer Mini may be one of the best tools I've seen yet. Weighing in at only 2oz the Mini will filter 100,000 gallons of water with only minimal maintenance. No awful to use UV lights, no crazy big pump. Just squeeze a bag of water through the filter into your waterbottle.
The base kit comes with one 16oz reusable squeeze pouch. You'll likely want to get a few larger bags, I like the 64oz for fairly easy filling in a river or lake, and also being a decent size of water to process in one quick sitting. If you have running or gravity fed water that needs filtration, you can also splice the Mini in.
The Mini has a .1 micron filter, and Sawyer claims "this filter was tested to 10 million parts of bacteria and one million parts of protozoa without a single breakthrough — the highest testing level for filtration." The water doesn't taste like chemicals. I remember a boy scout Sierra backpacking trip and iodine purification tablets galore. Gah!
For under $20 no emergency survival kit should be without one of these filters.
Sawyer Products Mini Water Filtration System via Amazon
Image via Amazon