There's a reason you don't drink out of the toilet. It's gross. Even if you got a super toilet that only flushed diamond rain water, it'd still be disgusting. But that's the thing. The only thing keeping you from drinking cleansed pisswater is you.
According to NPR, proposals to reuse sewage and turn it into drinking water have been shot down numerous times over the years. And it's not that the water didn't meet standards for cleanliness. It would have been fine. Rather, they never got off the ground simply because the idea sounded so nasty.
And don't get me wrong. We've done it, too. It just has everything to do with a phenomenon called psychological contagion. Remember the episode of Seinfeld when Jerry accidentally knocks his girlfriend's toothbrush into the toilet? And, after brushing her teeth with it, she forever after had a "taint"? Same deal. The dirtiness of the toilet attached itself to her mouth. So too does the dirtiness of our poop to the water that was cleansed of it. We still think it's dirty.
So how do you fix it? More psychology. Scientists found that after making people think about the purified water in an underwater aquifer, they were more apt to drink it. Which is kinda crazy. Just think. You could make me drink actual poo water if you made me think it was mountain fresh, but telling me truly clean water originated in a sewer would make me cringe.
Moreover, actually putting that thinking into practice would be expensive. Running the water through some kind of underground spring just to make you think it's clean could make it dirty all over again. So then it has to be cleaned again, making the process cost maybe three times as much as it already does. And you'd probably have to pay more for it, too.
Bottom line: Just be glad you have water to drink at all. [NPR]