Agreed. But water treatment plants typically monitor output for the chems they are obligated to monitor.
From GE Systems:
“Because of the many technological developments in electronics and microprocessor technology over the last decade, there is a wide range of instrumentation available to monitor water treatment systems. The following sections address the systems available to monitor conductivity. pH, corrosion rate, turbidity, dissolved oxygen. sodium, fouling, biological activity, and halogens.”
These are only a few characteristics that can be auto-sensed.
Yes, but if a chemical...as in this case is not considered hazardous, then they won’t be monitoring for it.
Also note the excerpt you posted does not include ...chemicals.