Section Six
INDUSTRIAL WASTES
A. HEAVY METALS
67    INDUSTRIAL WASTEWATER TREATMENT FOR REMOVAL
AND RECOVERY OF HEAVY METALS
Nicholas L. Clesceri, Professor/Department Co-Director*
Rene Cooper, Project Manager**
Dana L. Levy, Graduate Student and Project Engineer*,***
Mark Roberts, Graduate Student*
Stewart Wiley, Graduate Student*
♦Department of Environmental Engineering & Environmental Sciences
•♦Center for Manufacturing Productivity and Technology Transfer, Rensselaer
Polytechnic Institute, Troy, New York 12180
***C. T. Male Associates, P.C, Greenfield, Massachusetts 01302
INTRODUCTION AND PROBLEM STATEMENT
Typically, removal of heavy metals from industrial wastewater by precipitation yields sludge which
contains a mixture of metals. While this is intended to produce effluent water which is acceptable for
reuse or discharge, the sludge which will be produced may be subject to strict disposal requirements
(i.e., stabilization/solidification then burial in a secure landfill). This method of sludge management
is expensive because of the handling/disposal costs compounded by the lost value of the metals
contained in the sludge, could potentially cause environmental degradation as the landfill ages (and
thus has associated liability), and does not conserve resources.
The Harrison Radiator Division (HRD) of General Motors Corporation, located in Lockport, New
York, manufactures aluminum and brass heat-exchanger systems for vehicles. The manufacturing
process involves sheet-metal work, including soldering and brazing, and chromium conversion coating for corrosion resistance.
Three wastewater streams are generated: two contain zinc, lead, and oil & grease (as a result of
fluxes and solder); the third contains chromium in both the hexavalent and trivalent form (the
hexavalent form predominates and is present as the anionic chromate or dichromate radical). Currently, the three wastewater streams are collected by separate systems and conveyed separately to the
wastewater treatment plant, whereupon the chromium wastewater stream is treated with sulfur dioxide in order to reduce chromium to the trivalent form. Then, the three wastewater streams are blended
together, and the blended wastewater is treated by precipitation and sedimentation for removal of the
metals and oil & grease. This results in production of a sludge which is a listed hazardous waste,
therefore, this sludge must be stabilized/solidified and disposed of in a secure landfill. This current
situation is depicted schematically in Figure 1.
Harrison Radiator Division has identified a desire to minimize the production of hazardous waste,
and has enlisted the assistance of the Center for Manufacturing Productivity and Technology Transfer
(CMPTT) and the Department of Environmental Engineering and Environmental Sciences (EE & ES)
at Rensselaer Polytechnic Institute to aid in achieving this goal.
The sludge currently produced is a "listed hazardous waste" and therefore is subject to the strictest
regulations regarding reclamation and disposal. This incurs regulatory and economic prohibitions to
recycling and reclamation activities which would otherwise be technically feasible (the quantity of zinc
in the sludge is significant enough to be useful to a secondary zinc smelter). Due to the regulatory
restrictions imposed on activities for reclaiming materials from a sludge which has a "listed hazardous
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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