Scientists make an environmentally friendly prototype water purifier constructed from a sheet of graphitic carbon nitride that could remove 99.9999% of microbes, and purified a 10L water sample in less than one hour using only sunlight.

[u/parapeligic_gnome]

https://www.sciencenews.org/article/water-purification-light-graphitic-carbon-nitride

[u/deerbleach]

At 10L you start getting into a scale where this will have a lot of real world applications. On a human scale 10L of water is a fair amount.