Thomas Industries', Hopkinsville,Kentucky, operation recycles 12,000 gal of rinse water per shift while recovering nickel and brass. For three years the company has successfully recycled rinse waters from its nickel-brass plating facility. The company's goals are to exceed all environmental, health and safety regulations in order to support its reputation as a high-quality producer of a complete line of lighting products. These products include chandeliers, wall sconces, flush mounts, fluorescent, recess and outdoor lighting.
To ensure product quality, low production costs and on-time delivery, the company elected to operate its own finishing business. The installation of new paint lines and plating facilities has been completed. The treatment of rinse waters from these facilities has been of particular importance to Thomas Industries.
Of special concern was the plating operation, since the system handled heavy metals. The company chose Pollution Application Systems of Hillsborough, North Carolina, to provide the necessary equipment for recycling chemicals and rinse waters.
The system reduces total rinse water need. The reduction occurs through exponential dilution (extra counterflow rinses), so water use can be reduced up to 90 pct while actually improving the rinsing process. Once water needs are reduced, plating baths are recovered using standard atmospheric evaporation. Due to the low level of water needed, the amount of evaporation is reduced, minimizing plating bath contamination.
Lower water use has helped Thomas Industry reduce its energy requirements for converting water to steam and reduce impurities from incoming city water. The rinsing system did not require Thomas to re-arrange its existing tank layout.
Reducing rinse water needs in its cleaning and acid dip sections helped Thomas minimize capital expenditures and conserve floor space. The electrocoagulation technology allows the company to remove an additional 90 pct of heavy metals after conventional solids removal.
This brings the purity of the recovered water to parts per 10 million, compared to parts per million for conventional end-of-pipe treatment. The recovered water is reused in the rinse tank. It is low in all metals, including calcium, magnesium and iron. The water is also free of algae and bacteria.
The plating process at Thomas Industries is as follows:
- Buffing compound removal, hot, two stations
- Soak Cleaner, hot, two stations
- Electrocleaner, hot
- Rinse, two stations
- Acid clean
- Rinse, two stations
- Nickel plate, eight stations, atmospheric evaporation 140F
- Transfer tanks with spray rinse
- Rinse, three stations
- Brass strike (CN)
- Brass plate (CN), three stations, Atmospheric evaporator 105F
- Auxiliary heated tank for evaporation
- Rinse, six stations, all counterflow to auxiliary tank
- Oxidizer (antique finish)
- Rinse, three station counterflow
- DI rinse, spot prevention
- DI rinse, hot
- Dryer, two station
Because of the high recovery of nickel and brass, solid waste volume, after dewatering in a plate-and-frame filter press, has been reduced by 90 pct. The water removed from the sludge is returned to the electrocoagulation system.
Even though Thomas Industries uses cyanide plating solutions in the brass plating tanks, the return of all rinse water limits the need for cyanide destruction. The low volume of evaporation in the atmospheric evaporator, resulting from the exponential dilution concept, minimizes buildup of carbonate in the brass tank.
Now that the company has good, cost-effective control of its plating operation, the next step is to recover and recycle rinse water from its parts washer and paint pretreatment line. If this is successful, periodic disposal of alkaline cleaners, spent acids and filtration backwash from brass and nickel tanks will be all that is left to contend with.
Thomas Industries has attacked the problem of pollution control in a systematic manner. The equipment installed on the plating machine required approximately three weeks to install and another month of tweaking and adjustment to bring it to its present performance.