It goes into the same formation where the water came from. If there was frac water in our water supply you would know it. The chlorides and hardness would be easily noticed. We aren't allowed to frac into frac into formations known to have 'clean' water. Remember that water down there is already contaminated with whatever rock formation it's in. A lot of our water we drink is well water which is shallow, or spring water already naturally filtered.
Liberty: Too big to fail