Bacteria need at least three things to thrive: proper food, proper environment, proper temperature.
It seems to me if you can't remove it's micronutrients from the water and if you operate at its "thrive" temperature then you need to attack its environment while sitting stagnant. There has been several articles I have read where hospitals have used and other research done that have proven that some metals, copper in particular, kills nasties of several sorts. Here's a link if you don't believe me - copper kills bacteria and viruses
Wouldn't it be good to make the area of containment that could hold water stagnant and at the warned temperature from copper or inbed a copper mesh in a dark holding tank? Maybe someone could do a lab test on this specific bacteria. Anyways, after this thread I'm holding my breath in all solar showers..... If you use it I guess I will make millions from intellectual property rights! lol Not!
edited P.S.- Now that I think about it, as a child we had a room humidifier that blew air through a revolving wet mesh made of woven copper. Perhaps there was their secret legionella killer and they didn't even know it. I know you may think, "it can't be that simple but, can't it sometimes?"