G'day Dave,

You probably could, but it's unnecessary for small containers & jerry cans.
This treatment is designed for larger water tanks that are unable to be cleaned out easily by other means or able to be flushed or rinsed out without hassle, such as in-built or under-vehicle tanks.
I can't see any reason why you couldn't, if it's something you would like to use.

G'day Laura, 

It doesnt, no.  This product is only designed to create a sterile tank environment so fresh water to be stored for longer.

Vinegar and Citric Acid are recommended for descaling, but the watertank needs to be isolated to prevent any risk of corrosion.

You can call BioMagic directly for further information on descaling, they have over 22 years of caravan expirence & love helping out with advice.