Abstract: The zero discharge spray system comprises a tank for collecting and storing inse water, a set of spray nozzles aligned within the tank, and a pump for both pumping used rinse water through the spray nozzles and/or to the plating bath as makeup for evaporation. A timer level control system maintains the plating bath level and the rinse tank level, and limits the nozzles spray time. The system also includes a fresh water spray for final rinse of plated parts. By using a controlled spray rinse system which reduces the amount of water added to the system so as not to exceed that lost by evaporation, no contaminated rinse water is discharged as waste.

Abstract: A process for treating industrial waste water containing hexavalent chromium (Cr.sup.+6) and other heavy metals is disclosed which comprises reduction of Cr.sup.+6 to trivalent chromium (Cr.sup.+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9 under conditions such that sludge production by the process of the invention is substantially less than that characteristic of prior art processes. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.