69    THE VARIABILITY OF FERROUS FOUNDRY WASTE
LEACHING CHARACTERISTICS AND COMPARISON
TO LANDFILL UNSATURATED ZONE LEACHATE
QUALITY
Richard C. Krueger, Engineer
RMT, Inc.
Madison, Wisconsin 53703
Robert K. Ham, Professor
William C. Boyle, Professor
Department of Civil and Environmental Engineering
University of Wisconsin
Madison, WI 53706
BACKGROUND INFORMATION
Foundries produce castings by pouring molten metal into molds. The exterior shapes of the molds
are made of molding sands and the interior cavities of core sands or cores. Previous studies1'2 have
estimated that from 65% to 99% of all foundry wastes disposed originate as molding and core sands.
Molding sand is a mixture of silica sand, clay, carbon, and water. Core sand is composed of silica
sand with a small amount of chemical binder. Binders are required to bond the sand grains together
after curing. Typical binders include vegetable and petroleum oils, sodium silicate, ground corn flour
and oil, ground hardwood cellulose, and synthetic binders (e.g., phenol formaldehyde, phenol isocya-
nate, alkyd isocyanate).
Molding sands and a small amount of core sands are recycled through the mold-making process
several times before they are eventually discarded. These recycled sands are collectively known as
"system sand." The typical waste composition has been reported1 as: system sand 65-99%, core sand
and core butts 2-19%, slag 0-16%, cleaning and grinding 0.5-9%, and dust collector wastes 0-11%.
The wastes are generally hauled to a landfill. Although most of the waste is inert, certain components of the waste have the potential of being leached from the landfill and entering subsurface soils
and groundwater. Previous studies have analyzed water samples collected from pressure/vacuum
lysimeters within the unsaturated waste at foundry mono-landfills.2 This study and others3'4 have
indicated large chemical concentration variations from leachate samples taken from the same lysime-
ter over time, between different lysimeters at the same foundry mono-landfill, and between laboratory leachates derived from different wastes taken from the same foundry. The causes for these
concentration variations are unknown; however, microenvironments due to the unmixed nature of the
foundry waste and the variability of the weather are possible causes.
This present study involves detailed leach testing of wastes from one ferrous foundry (Foundry D2).
The study includes a components of variance analysis to estimate the variances associated with sample
handling and laboratory analytical procedures, as well as several other statistical methods to estimate
the mean concentrations and variations about the means of 10 chemical parameters. It then compares
the previously obtained landfill leachate results to the laboratory batch leaching test results from
wastes from this foundry by means of probability plots.
METHODS
The waste composition for the ferrous foundry tested in this study has been estimated as:2 system
sand 52%, core sand and core butts 23%, slag 13%, cleaning and grinding 6%, dust collectors 4%,
and other sources 2%. System sand was chosen as one waste source to sample because it comprises the
largest percentage of all the landfilled waste at this foundry. Core butts were chosen because they
comprise a large percentage of wastes and were thought to be the most heterogeneous waste source.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea. Michigan 48118.
Printed in U.S.A.
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