When I lived in Turkey, they once warned us that they started drawing water from a contaminated, untreated river three weeks after they did it. The rationale was that if they told people immediately, everyone would blame their new illnesses on the water. If no one knew, no one would blame the water, and the opposition party wouldn't have a chance to use it against them.
I drank it for weeks, and i was cool. Don't let "E. Coli" scare you too much -- not all forms are hazardous.