Actually I know a lot about this. If you use reverse osmosis to purify the water than there is nothing to worry about. An RO filtrations system will give you absolute pure water, based on how good the system is. There is no way other than RO to get the water that pure. It doesn't matter where you take the water from to get pure water as long as it hasn't been contaminated with petroleum products or something like NBC. If you use a *complete* RO system on sewage than your water will be better than anything you are drinking in bottle right now.(most bottled water is RO purified, read the label to find out) This is how they make microchips, they use RO to purify water to nothing but H2O and then build the chips in the pure H2O to avoid any contaminants in the air.
Bottom line: soon all water will be RO filtered and who cares where it came from once it is pure.