If you are useing molten Salt Peter...there's nothing to discard or throw out or flush away anyway...no fumes, no hazards, it does no wear out or spoil or smell or need to be replaced because of frequent or even constantuse...so, no nothing, but a 'hot' temperature, molten-salt in an Iron or Stainless Steel immersion tank.
I do not see how the EPA would find anything to be interested in with that.
'OSHA', yeah...if you have employees...but then too, your Insurance Carrier, if you have employees, may care...also...