From article, "There’s plenty of water along the Long Path, but as with almost anywhere, you’ve got to assume it is contaminated. To filter water, I carried a Sawyer Products squeeze filter, which consists of a 32 oz bag you fill in a stream, and then a filter with nozzle which you screw onto the bag and through which you squeeze out the water. I found the bag was easier to fill in a briskly running stream, but otherwise this filter worked well for me, and it weighs only a few ounces."
Doing the above when near major cities is not advisable to say the least. Yeah, you may filter out pathogenic micro organisms, but what about all the chemical and heavy metal pollution..
A carbon filter, or something else besides sawyer squeeze, is necessary for that.