The problem in many contexts is that sanitation and water are connected. Having sanitation downstream does not help water quality if there is none upstream. Then there are floods that spread the microbes even farther. Consider today's editorial in the NYTimes on the huge costs of lack of sanitation and resulting poor water quality
Some part of responsibility for clean water is properly for the government to assume in such a context, Shanta. Water utilities should recover costs, but they probably need to be set up by a public (community, city, district) authority to be efficient and effective.