Most public water systems treat water so that by the time it reaches your tap, the chlorine level is around 0.5 to 1.0 ppm. This is sufficient for a water system that is in regular use, since the constant on and off, flushes the system ensuring low levels of chlorine are still present. If you were to collect this water and measure chlorine levels as little as 24 hours later, you would likely find < (less then) 0.5 ppm, not really enough to have significant biocidal properties. Water to be stored for any significant period of time, should be hyper-chlorinated to 10-12ppm.

As to solar (UV) disinfection of water check out this web site:

Solar Water Disinfection

But keep in mind it works best in the middle latitudes.


Pete