Data 1: Plating Shop
discharged water at a rate of 30 GPM to the local sewer. The separation
technique was a clarifier sized for a flow of 100 GPM. To ensure
compliance with silver and nickel, over 20 point source ion exchange
and reverse osmosis treatment systems were employed. All concentrated
dumps were batch treated. The local authority always provided
a three day notice prior to pulling a compliance sample. Data 2: Plating Shop purchased a 40 GPM microfiltration system with an installed spare membrane rack. The solution included (6) tanks for collection of concentrated wastes, (4) large equalization tanks for acid/alkaline, cyanide, hexavalent chrome and electroless nickel. New reaction tanks, mixers, controllers and metering pumps were installed. The pretreatment was based on the classic hydroxide precipitation. The design retention time was greater than 30 minutes (cyanide - 60 minutes). A PLC and touchscreen were provided to control the operation. 18 of the point source treatment devices were shutdown. The local authority no longer provides a notice prior to pulling a compliance sample.
Data 3: Plating Shop found isolated segregation issues with silver on two different plating lines. The primary issue was rinsing parts in the wrong tank. To maintain a buffer, Plating Shop changed from hydroxide chemistry to thio-red chemistry. A thio-red controller was installed. As before, the local authority provides no notice prior to pulling a compliance sample.
| Component | Limits | Data1 Clarifier Hydroxide |
Data2 MF Hydroxide |
Data3 MF Thio-red |
| Copper | < 1.5 ppm | 0.443 ppm | 0.34 ppm | 0.04 ppm |
| Nickel | < 1.7 ppm | 0.558 ppm | 0.29 ppm | 0.19 ppm |
| Silver | < 0.23 ppm | 0.170 ppm | 0.14 ppm | 0.04 ppm |
| Zinc | < 2.0 ppm | 0.225 ppm | 0.04 ppm | 0.04 ppm |