Well, I've not piped up yet. I work for the Water Pollution Control dept of a small (160k population) city. Fortunately, I'm in industrial pretreatment and SID (State indirect discharge) permit enforcement. Indirect discharge means it goes into the sewer. That's mostly to protect the wastewater treatment plant's ability to meet it's discharge limitations in it's permit. Aka, protect the river.
Basically, this is one of the ugliest topics out there. Most local govts don't like making rules they can't enforce. But they are required to make this law. The only reason you pro detailers aren't required to fill out manifest for each car you detail and where and how you collected the water is because no one would ever see the paperwork and no one wants to make the form or store them when they come in.
Water pollution is generally not the kind that makes it into the headlines, since it's so easily quantified. Scary unmeasurable enviro stuff is the headline makers. But really, water pollution is where most of the problem is.
You guys, no, you don't make a dent. However, we do regulate several places here that wash garbage trucks. We watch them closely. They know me by name.
You guys who collect and discharge to the sanitary sewer. Thanks. It's better to let the microbes at the WWTP do the work than to force the struggling city greenspaces fight to neutralize your chemicals.
That said, me, a private citizen. I have no laws concerning my use of detailing chemicals. Heck, there isn't even a law about what I can and can't do with used motor oil or anti-freeze, and both are considered hazardous waste. The official word is they "cannot be poured down drains" but there is no law.
Sorry for the long ramble, and posting in the pro area. But I read this for knowledge and try to just lurk, but I felt I might pipe in.