There are many water filtering options, and basic chemicals for swimming pools can sterilize water, if you know what you’re doing.
You can also look into “lifeStraw” available at Amazon:
http://www.amazon.com/LifeStraw-LSPHF017-Personal-Water-Filter/dp/B006QF3TW4/ref=sr_1_1?s=outdoor-recreation&ie=UTF8&qid=1410723315&sr=1-1&keywords=lifestraw
For $25 you can filter 1000 liters of water. Any river or lake will do.
Thank you
Lifestraw does NOT remove viruses from water, though.
Just wondering....where did you find it for $25? Says $47 at your link....