we have a tank in our project that will store rainwater. because our landscape theoretically doesn't require irrigation, it seems this cistern would only serve the purpose of SSc6.1

I understand storing and slowly releasing rainwater isn't the same as treating it - but im wondering if there is any kind of tried and true simple (cheaper) method of treating from the cistern? (ex: filters, etc?).

if so, anyone have product info I could have our civil engineer reference?