how can some water be harmful even after treatment

Question

anonymous · Answer

The treatment itself can be harmful. Too much fluorine and chlorine come to mind. Although small amounts of fluorine is obviously good for you. On the other hand, a lack of natural minerals can have long term negative effects in a human if distilled water was ALL the human drank. Natural water has magnesium, potassium, calcium in small amounts and obviously these are essential for us.

That is all I can think of. Is this really an engineering problem? :) Seems more like a biology class.

anonymous · Answer

chlorine as a disinfectant forms HAAs and THMs, ozone forms bromate as by-products, chloramine forms dichloroamine and trichloroamine, chlorine dioxide forms chlorites and chlorates. and so on.  these by-products are harmful to human health.