I recently purchased some 55 gallon blue barrels for rainwater harvesting. Upon closer inspection of the barrels, I noticed they previously housed food grade sodium hypochlorite which was used to wash produce. I was searching for food grade barrels but wasn't expecting bleach. Because I will be watering plants and fruit tress with the rainwater, I don't want the water chlorinated which would kill the bacteria I'm trying to promote in the soil. These barrels are empty but I was advised to rinse them when I initially purchased them.
Can I assume that just rinsing with water won't completely get rid of the bleach and that the residual bleach which may be on the walls of the barrel will not decompose or neutralize by itself?
If I were to wash the barrels with water and Hydrogen Peroxide, will this suffice to remove the chlorine?