I once stayed in a jungle lodge in Ecuador that used ozone to keep drinking water safe. They had a 55-gallon drum and an ozone generator hooked up to a solar panel. Whenever the sun was out, ozone was bubbling through the water. This worked great at keeping anything biological out of the water. The raw water we used though was completely free of chemicals (fertilizers, herbicides and pesticides). I live in an urban area and if the water ever goes out, my surface sources are all suspect. Even rainwater coming off of a roof is suspect of arsenic and a few other nastys. I don’t think ozone or UV does anything for chemical contamination, which is why I’m leaning toward the filtering route. Another option would be to dig a well, but I don’t think the city would allow that.
Thoughts?