text: It is very tightly controlled these days - it used to be that you could neutralize the acids with bases and put them down the drain (not any more).\n\nChemical machining by its nature dissolves large quantities of metals into acids.  These days an elaborate system is setup to precipitate all the metals out of solution down to the parts per million level, and then any waste acid that can't be recovered is sent to an incinerator.  Nothing is allowed down the drain, and the EPA is watching what comes down the drain very closely - the will sue you if you dispose of any heavy metals down the drain.