@ehBeth,
This is standard stuff in water treatment plants, conventional steam plants snd and in nuclear power plants where the chief source of distributed radioactivity is ordiary corrosion products (metals) dissolved in the circulating water, which becone irradiated while passing through the reactor..
In nuclear plants the primary coolant is highly purified distilled water with near zero dissolved solids and extremely low levels of chlorine, circulating in stainless steel clad pipes and circulating through the reactor fuel elements clad with corrosion resistant zircon alloy. As an extra precaution the water is doped with free hydrogen to absorb any loose oxygen atoms thsat msay be present. Finally the water is circulated through an Ion exchanger which continuously removes any chlorine or metallic ions that may be present.
In conventional powerplants and water treatment plants, phosphates are used to maintain an alkaline ph which supports a thin but stable oxide layer on the inner pipe material, effectively inhibiting further corrosion. This is a ubiquitous technology that dates back at least sixty years. It is very hard to conceive how any competent operators of the Flint municipal water treatment system could have decided that suspending the use of this simple but relaible system, even for a day, was a good idea.
In all of these plants continuous monitoring for chlorine concentrations is a universal norm. High concentrations of Cl defeat all of the above defenses, and contolling chloride concentrations is fundamental to safe operations even without the factor of human consumption.. It is equally hard to rationalize knowingly tolerating these high levels in the source water without using any of the readily available corrective measures.