Good start! Have you heard of BIOTA (blame it on the altitude) water bottles? It’s essentially a plastic that is made from corn oil, etc. and afer just three months in a ladfill, it decomposes! I actually took one of these bottles and placed earth into it added some water and within two weeks it appeared as if the bottle was melting. It shrunk 1/4 of its size!
As for the sterilization factor, how about coming up with a collapseable bottle with a top that was self sealing so that at any given time the bottle would be ready for refillage. Kinda like those water containers you use when camping.
Cheers!!! 