Case Study: Joe’s Plating
Zero Discharge: Case Study of Copper Removal
Rinse Water Treatment, Recycling and Reuse
A specialty metal plater in Santa Barbara, California faced continual scrutiny from the city sanitation district over rinse water discharge. The city discharge regulations, published violators exposure, and fines caused the other five metal platers to leave the city jurisdiction. Worried about violating heavy metal and cyanide discharge limits, Joe’s Plating decided to remove the cyanide and heavy metals and recycle the rinse water and eliminate discharging to the city sewer. EC was installed to especially reduce copper which usually measured at 4 ppm. Use of the EC unit satisfied copper reductions to less than 0.02 ppm.
The rinse water clean up options included reverse osmosis, ion exchange, evaporation, and Electrocoagulation (EC). The reject water from the reverse osmosis concentrated the heavy metals, creating a worse problem for heavy metal water discharge. Ion exchange required continual maintenance of the exchange resin. The maintenance cost to regenerate the resin was estimated to be 50% of the capital cost for the system each year or $0.14 per gallon. The ion exchange capital cost was about the same as the EC capital cost. Evaporation produces a heavy metal ion powder and required about $0.15 per gallon evaporated for energy. The evaporator capital cost was about three times that of the ion exchange or EC capital cost. EC converts the metal ions to an oxide from. The oxides are separated from the water by settling tanks and filtration. The clarified and filtered water is reusable in the metal rinsing process. The EC operating cost is less than $0.01 per gallon.
EC will oxidize heavy metals, treat arsenic, cyanide, and cleaners. The unit is very easy to operate and maintain, and can replace chemical treatment, 85% of polymer use, reduce sludge volume 85%, and provide a D.I. quality rinse water free of mineral hardness and contaminants.In September 2001 Joe’s Plating installed a 3-gpm EC system followed by 2 cone-bottom decant tanks and filtration for removal of heavy metals and cyanide. The overflow water from the rinse tank is collected in a storage tank. The rinse water is processed through the 3-gpm EC unit, decanted to separate the bulk of the solids, and the clear water is filtered, sent to a second holding tank then sent back to the rinse water tank. The plating shop water use has been reduced from 800 gallons per day to 60 gallons per week, which includes one toilet. The operating cost is about $0.002 per gallon treated. Thanks to EC this shop was permitted for Zero Discharge.