In the manufacturing of certain mirrors, a strong copper solution at low ph is used to apply a thin coating to the glass surface. After adhesion, the excess is washed off and collected as wastewater. The wastewater at this facility is treated using 4 chemicals: caustic to raise the pH to 8.5, DTC (dithiocarbamate) as a metal precipitant, an organic based coagulant, and an anionic flocculant. The facility was in and out of compliance with residual copper in their effluent due to the fine pin flock carryover.
By pH adjusting to 8.0 and the use of Floccin-A, the treatment is simplified, easier to control with limited operator attention, makes a drier sludge, flock that settles faster, and maintains compliance with the effluent copper levels. In addition, the usage of the DTC relieves the facility from the liability of the use of this product, a regulated biocide with adverse effects to the downstream POTW if discharged.