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Pollution Prevention and Control Technologies for Plating Operations
Section 3 - Chemical Recovery
3.3 VACUUM EVAPORATORS
3.3.8 Residuals Generation
Vacuum evaporators used for the recovery of plating chemicals create three streams: (1) the concentrate, which is reused in the plating bath; (2) the distillate, which is reused in the rinse system; and (3) cooling water, which is recycled using a cooling tower, reused as rinse water or discharged to the sewer. Cooling water requirements were previously described in Exhibit 3-145and 3-17.
Only two respondents indicated that they generate any residual wastes other than the three streams mentioned. PS 143 indicated that they generate approximately 30 gal/mth of sludge, which they mix with their other F006 sludge and sent to off-site recycle. This sludge is generated from the treatment of the distillate (cyanide oxidation, precipitation, filter press and sludge dryer), which they do not send to the rinse tanks. PS 298 reported that carbonates collect at the bottom of the evaporation chamber forcing periodic removal. They remove approximately 100 lbs/mth of this material and treat it on-site.