Hope you don't have well water and a leach bed because if that's the case then a dog pooping in the river is a drop in a puddle basically. If you have well water there is a very high chance that you have drank the same water that you or your neighbor flushed down the drain after taking a massive dump. Gets even better though if you have a sewer hookup and city water. They collect all the toilet water and filter it really good for solids and chemically treat it and it gets pumped right back to you again. I mean that's the basics of it. I over simplified.