As I read up on it, I think solar heat generated is a prime disinfectant, along with the UV. The fact they recommend placing water bottles on corrugated rooftops is what leads me to this conclusion.
Not perfect, but much better than nothing I guess. If needs be, I'd do it and feel good about it.
I have a daughter. I tell her, "911 is what you dial after you're raped. 1911 is what you should have before they try."