Tap water is not pure and contains a cocktail of impurities - some of which are desirable for giving it a "good taste".
Indeed - but, as I said, most of those 'impurities' are (inorganic) 'minerals' and, to the best of my knowledge, very few living organisms (other than things like the 'deep sea' ones' I mentioned) can survive and thrive on just that.
I would speculate that some bacteria are good as living off small amounts of nutrients.
As I said, we have the Laws of Physics, as well s biological issues, to consdier and satisfy. The (not insignificant) mass of countless millions (or billions) of bacteria has to come from a corresponding 'not insignificant' mass of the nutrients that have 'consumed'. It's more a question of what
types of 'nutrients' a particular species of organism can make use of.
I suspect it's not so much the copper dissolved in the water, but copper pipes/tanks will have hostile surfaces that are harder for the bugs to colonise. I.e., if they can't form a nice habitat on the surfaces, it's going to be much harder for them to grow wildly rather than just get flushed away with water usage.
For what it's worth, I would personally doubt that. Very tiny amounts of 'dissolved copper' (primarily copper salts) are very toxic to microorganisms. I remember an illustration of this when I was at school. We looked at a drop of 'pond water' under a microscope, and saw countless little micro-things (I imagine larger than bacteria) 'buzzing around all of the place. We then touch the edge of the water drop with the end of a piece of copper wire, and all of those previously 'live' organisms instantly became motionless, ssumed dead.
I've tried to have a look, but all I can find are various sites stating that "legionella is the most common ..." But I suspect the main reason we hear mostly about it is because Legionnaires disease is fatal to a significant proportion of people who catch it, while other illnesses (including those due to other forms of legionella such as Pontiac Fever) aren't.
Unless we can discover something different, in terms of environmental/nutritional requirements, about Legionella, on has to assume that similar considerations apply to many (maybe most) other bacteria - and, despite what you say, there are plenty of other bacteria that can be transmitted by aerosol and which result in illnesses with a significant mortality.
One has to wonder whether we would ever had heard much about this had the 'initial' publicised outbreak not been in such a large population (of 'legionnaires'/veterans), a significant number of whom died.
Kind Regards, John
