We sometimes get a slimy residue around parts of the inside of the drinking water filter housing from the rainwater tank, on the upstream side of the filter. It takes months to accumulate to a point where you can find it.
It just occurred to me that there are probably UV LEDs available now for water sterilization, so I went Googling. I only found two.
One expensive American device specifically for this purpose, and a very cheap Polish unit intended for aquariums.
I'm considering the American unit because it's designed specifically for drinking water. The Polish aquarium unit may not be made of food-grade plastics etc., but tropical fish can be fairly sensitive things, and the water is recirculated, so you would expect the materials of construction to be suitable for contact with potable water. The other possible disadvantage of the aquarium device is that the water is recirculated, so it may take many passes to fully sterilize, whereas the US device is designed for a single pass.
I'm just curious to know if anyone else has considered something like this or seen something similar.