I didn't see any mention of this in the sunlight bun. It's an old standard. Kids have done it as school science projects for decades. Also, I had a UV component to my under the sink water filter over 20 years ago for this very purpose. In a pinch, you could just get a big MASON jar and let it set outside in the sun for several hours.

Of course with water, you have to also consider other impurities that could also be in the water, like heavy metals, fluoride added by your city government, pesticides, etc.

https://modernsurvivalblog.com/health/how-to-purify-water-with-sunlight/