Fish poop in your drinking water.
At some point, you poop in your drinking water. OK, maybe not you. But someone. At some point.
I'm pretty sure they filter it between that point and when you drink it. Most of the time.
They do filter it, but not at all completely. There is what is called an "acceptable level". This is actually a practice in just about every food and drink industry. There is an acceptable amount of feces in burgers at Burger King.
I was in the lab where I work and saw some test results left out on a table. Businesses with their own source of water (well water) have to have the water tested periodically for the amount of fecal matter in it. Many other unfiltered things are not tested for. The place in question failed.
That was sarcasm. I forgot the smiley. Luckily, most of the water I work with (I work in the water industry) is well, not surface. Very little in the way of organic contaminants. Most of what I deal with is removal of unwanted minerals (iron and manganese are the two most common), with the occasional aerator to strip off some volatile that crept in to the aquifer (mostly from industry, benzene, tricholoroethylene, all kinds of other -enes). The wells I see are pretty deep -- most in the 500-1000' range -- that the only way organics get in is via contamination at the time of drilling. Of course, they treat the well with a super high concentration of chlorine to kill off any bugs, then flush, then put it into production once it passes the bacteria tests. It'll have some kind of chemical filtration or sequesterant to remove the majority of the material, then a polishing filter to clean up taste, odor, and color before sending it out to customers. I see all kinds of things that are in the water, and I still drink it.
Surface is a whole other ball of wax. Lots of interesting things floating around in there.
