The Flue Gas Method of
Treating Chrome Plating Waste
James W. Canan, Senior Engineer
Brown-Lipe-Chapin Division
General Motors Corporation
Elyria, Ohio
The discharge of rinse waters from electroplating plants has long
been a source of polution of streams and sanitary sewers. Due to the
very nature of rinsing, which is basically controlled dilution, the
concentrations of the contaminating chemicals have been low, but
nevertheless troublesome for the proper biological maintenance of our
streams and rivers. The low concentration of contaminating chemicals
creates a severe economic problem in achieving their effective removal.
One chemical commonly found in the waste effluent from electroplating plants is chromium, especially and particularly the hexavalent
ion of chrome. Chromic acid is used in plating plants for several
purposes. In addition to plating solutions, anodizing, chormating, and
paint pretreatment solutions are also common contributors of hexavalent chrome to the waste water. Although the concentrated solutions
may be disposed of infrequently, the rinses following these concentrated
baths are continually being discharged to either rivers or sanitary sewers.
Many states have laws and regulations which limit the concentrations of this particular chemical that may be discharged into natural
waterways. A concentration often cited is 2.0 ppm maximum. Another reason for requiring low concentrations of chromium, in addition
to its harmful chemical and biological effects, is the strong color
imparted to streams by even relatively low concentrations of chromium.
Considerable effort and monies have been expended by private
industry, universities, municipalities, and state agencies to develop
methods for removal of the chromic acid from industrial waste effluents.
A continuous effort is being maintained by these same agencies to
further improve current methods both from an efficiency as well as a
cost standpoint. It is felt that the method to be proposed here will
provide a substantial cost reduction to any plant currently employing
the precipitation method of removing chromium from its waste.
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