I agree with previous posts on iodine tablets & filters.  Additionally, when I was in Madagascar with the Peace Corps, every little store or stand in almost every town/village sold a product called Sur'Eau, which was a sodium hypochlorite solution (diluted bleach) that disinfects water making it safe for human consumption. Peace Corps supplied us with the product and our Health Volunteers helped promote the use of this product throughout the country.  It was still recommended to filter the water first, but on a number of occassions, I simply used a drop or two of this product in my 1.5 liter bottle! ... View more