NIC - Yes, I know exactly how much power it takes the local water treatment plant to filter out my weed killers. Exactly NONE. I live in a rural area, have a well and septic tank. A foot across three of my four property lines I have row crops, alternating between corn, soybeans, and wheat. Across the road I have mostly corn but about every 3rd or 4th year they plant beans. The gallon or so of herbicides I use every year is NOTHING compared to what my neighbors apply every year. If it's going to find it's way into my well it can come from my neighbors as easily as it can from my yard. And yes, I do have an R/O system.
I've worked in the potable water equipment industry most of my professional career, I understand what you're saying about polluting our water supply. We as a world population will become very "thirsty" long before we get "hungry".
I stopped fertilizing my yard 15 years ago because of the damage urban use of fertilizer was doing to the local ponds, streams, and lakes. A good friend and co-worker was an avid fisherman. I aerate my yard now every fall, and my yard is in MUCH better over-all shape turf-wise than it was when we bought this place 20 yrs ago. And the prior owners had Tru-Green or Chem-Lawn or whoever come in and spray four times a year.
Like I've tried to say in my posts about spraying weed killers, you have to spray accurately, if a little is good, a LOT is NOT better. You have to mind the details. We have some very noxious weeds in this area that will take over large areas if not controlled. I'm sure you've heard of KUDZU, the plant that is taking over the state of Georgia. Well, around here Wild Cucumber can do the same thing. I've seen wooded areas along roads & Interstates where several acres of trees have been killed by it growing over them. I have a couple small wooded areas just several hundred feet from my yard. I get several Wild Cucumber plants every year. Mowing will slow or stop them, but if they get under a bush, spraying works much better. I try to manage my yard responsibly.