I agree that Pool Shock (calcium hypochlorite) is a good way to go. It is highly concentrated and one pound goes a long way. The downside is, it can be dangerous if not handled properly. The granules also need to be isolated from food and other gear because of it's corrosive nature. Here's a handy link which you are probably aware of, but others might not be...
using calcium hypochlorite to disinfect water
Thanks for the link. I hadn’t thought about it until last week when I ordered 100 packets from ebay for my husband to use in his drip lines. He had been getting a solution in 55 gallon barrels that cost an arm and a leg and I suggested using the pool shock and it works great, is easier to handle and is much cheaper.