Section Seven
INDUSTRIAL WASTES
C. METAL PROCESSING WASTES
66    CO-PRECIPITATION OF HEAVY METALS WITH
CHROMIUM IN BRASS MILL WASTEWATER
Michael J. Pardus, Chief Chemist
Cerro Metal Products
Bellefonte, Pennsylvania 16823
Raymond W. Regan, Associate Professor
Department of Civil Engineering
The Pennsylvania State University
University Park, Pennsylvania 16802
INTRODUCTION
Many industries are being faced with the need to improve their waste management procedures,
specifically when hazardous and toxic wastes (HTW) are involved.' The ultimate incentive for an
industry is the development and application of a comprehensive management strategy that complies
with environmental regulatory requirements, maintains or improves product quality and reduces
overall costs. The subject of the presentation concerns the achievement of this ideal at a brass wire
operation of an integrated brass and bronze mill (Cerro Metal Products, Bellefonte, Pa.). Indications
of the tradeoffs related to operational changes associated with materials substitution are also
outlined.
The primary source of the information to be presented is after Pardus.2 A paper on related topics
was presented by Pardus.3
STATEMENT OF PROBLEM
The standard production process for metal forming at the wire mill involved heat treatment,
chemical removal of surface oxides, and a drawing step. During the heat treatment step, cuprous
oxides formed on the wire surface. Removal of the oxide required oxidation from the cuprous to
cupric state. Historically, chromic acid had been used for the oxidation step. The inability to rejuvenate chromic acid pickling solutions and a relatively short working life imposed an economic penalty
on manufacturing. Additionally, concern over control of hexavalent chromium during wastewater
treatment had resulted in a Cerro policy to substitute its use with a stabilized hydrogen peroxide/
sulfuric acid solution. The impact of the proposed material substitution on the wastewater treatment
system was not known.
OBJECTIVES
This study was initiated to investigate the impact of the proposed materials changes on the removal
of heavy metals, primarily copper and zinc, from wire mill wastewaters. Observed trends under a
variety of test conditions were used to predict any difficulties in meeting federal discharge requirements. The impact of co-precipitation of these metals with residual chromium and its effect on full
scale treatment of process wastewaters were examined. Effects on the volumes of process wastes
generated and associated cost factors were also considered. The following were explored in detail: 1)
bench scale evaluation of the impact of chromic acid and peroxide pickling on the removal of metals
from process wastewaters; 2) comparison of bench scale results to the full scale operation of the
pretreatment system during operation with each type of pickling solution; 3) observation of the
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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