I do concur with most of the ...

I do concur with most of the Oxygen use items. oxides, ozone, micro and nowadays nano bubbles. All will improve but not complete the task you requested. In order to stop this or any pathogen is to stop inviting them in.  Not a joke. The first rule in all drinking water never use any kind of chlorine. It has a narrow ph range relative to your pathogen. When you kill the beneficial microbes that use the legionella as their food source you allow/invite them to populate your tank. ( You are killing all of your chickens so the wolves will have to find a new food source. You! Rule #2 DNA microbes will reduce organic into less complex form. But only RNA microbes have the genetic code to reduce all organic compounds into their elemental /nutritional state.  Since  the waste/waste water is centralized (huge mistake, just ask Texas, Florida, and Puerto Rico) then your microbial purification systems must be at the central processing. They can then be recycled back into the potable drinking water, agricultural use, or put into rivers to ocean and will continue cleaning the environment until their 12 week active life work span has concluded. They also generate collectable electrons/electricity. Waste not want not!