Section 6.    PLATING WASTES
RECYCLING UNDILUTED DRAGOUT
FROM TOXIC PLATING SOLUTIONS
Ernest R. Ramirez, Manager
Ramirez Associates
Far Hills, New Jersey 07931
Franz D. Koch, Manager
BMT Corporation
Greenwich, Connecticut 06830
More than half of the inorganic chemicals listed as harmful to humans in the Drinking
Water Standards are heavy metals. This condition places a burden on the electroplating
industry as one of the dominating sources of metallic ions. These metals are always used
in their ionic state and often are chelated or complexed. This, however, makes precipitation of the metallic ions more difficult. Approximately half of the drinking water used in
the United States comes from surface waters; therefore, there is a high probability that
heavy metal ions could find their way to potable waters, if care is not exercised in their
disposal.
It has also been observed that many of the heavy metals interfere with the biological
degradation processes, be they aerobic (activated sludge) or anaerobic treatments. For
these reasons and others it is clear that rinsing waters in plating operations are a potential
source of drinking water contamination if proper steps are not taken to remove these heavy
metals before the rinse waters are allowed to leave the plating premises.
The problem is especially acute because platers are often short of capital and have difficulties in acquiring expensive equipment and in supporting the cost of chemicals needed to
carry out the wastewater treatment. In response to this condition, the EPA has provided
small platers (less than 10,000 gallons per day of wastewater) with less stringent discharge
permit standards. While this act is understandable, it does not reduce the risk of having
heavy metals and toxic chemicals contaminate surface and ground sources of water ultimately used as drinking water.
NEW CONCEPT IN RECOVERING PLATING DRAGOUT
Tradition and conventional practices have demanded that removal of plating dragout
can only be accomplished by the use of successive flowing rinses in series. In recent years
countercurrent rinses have gained prominence as a means of conserving water and as a
means of reducing the cost of treating wastewater. The EPA ruling of special privileges to
platers with wastewater volumes less than 10,000 gallons per day has also encouraged
the use of counterflow rinses.
Some platers have instituted spray rinses and even fog rinses as an act of water conservation. In spite of these improvements and changes, the need to treat large volumes of wastewater in plating plants persists. While literature from time to time refers to immiscible
rinses as a solution to the toxic and cost factors or rinse wastewaters for platers, no clear
cut product has dominated this technology. In this regard, a small company in Connecticut
is presently marketing a waterless rinse which has appealed to several electroplating companies in the New York City area. The new concept of recovering, recycling or containing
an electroplating dragout solution introduces a new dimension in electroplating science and
in electroplating wastewater treatment.
173