The concrete will negatively ...
Published by Court Brooks
The concrete will negatively affect the water quality over time. A two-part epoxy or similar coating would benefit the overall quality if you can void the tank and fully dry it before application.
Although I'm intrigued by the document Abubacker Siddick posted, if you want to keep it simply you could use a basic, low flow swimming pool pump and filter, which could help with circulation so that the chlorine doesn't concentrate at the bottom.