I've just been diving down the Chlorine Dioxide Solution rabbit hole.
It's quite the rabbit hole, I'm just ordering some Sodium Chlorite & Hydro Chloric Acid. It seems good for sanitising water & treating a range of bacteria, viral & fungal infections (topically & internally).
I have a small 1500L poly tank of rain water seperated from my main water tank. I bought & filled this before my main tank got contaminated with town water. I'll be treating this water with the CDS.
Water security is pretty important.