Swimming pool and drinking water purification?

I have a friend that sells a 2 part system. It is Citric Acid and Sodium Chlorite. But when you mix them together you get chlorine dioxide. This is a powerful and safe water purifier. I don't know how much you would need for a pool, but you should give them a shout. I am sure Dr. Ron Neer, the owner, could tell you. Anyhow. I will include a link.