75    EVALUATION OF A PROPOSED TREATMENT PROCESS TO
REDUCE HEAVY METALS TOXICITY IN
CONTAMINATED SOILS AND ELECTRIC ARC
FURNACE DUST
Roger E. Mayfield, Senior Project Manager
Golder Associates Inc., Atlanta, Georgia 30341
INTRODUCTION
Regulations established under the Resource Conservation and Recovery Act (RCRA) provide
requirements for the identification, management and ultimate disposal of hazardous waste materials.
The requirements of 40 CFR 261 establish criteria for classification of hazardous waste.
The Toxicity Characteristic Leaching Procedure (TCLP) is a laboratory procedure that is used to
estimate the potential teachability, and thus mobility, of certain toxic organic and inorganic constituents in waste materials. The RCRA regulations (40 CFR 261.24) provide maximum limits for these
constituents in terms of concentration in the simulated leachate produced in the TCLP. test. If, for a
given waste, the TCLP leachate exceeds the specified limit for any of the regulated constituents, it is
classified as hazardous under RCRA and is subject to the associated restrictions regarding handling,
transport and disposal. The costs for transport and disposal of RCRA hazardous wastes are significantly higher than for non-hazardous wastes.
A process is proposed for treating granular solid waste materials to reduce TCLP heavy metals
toxicity. The concept is to expose the waste to acidic conditions in a slurry causing leachable heavy
metals to become solubilized and thus removed from the solid waste. After separation, the liquid
fraction of the slurry would be treated using hydroxide precipitation or other water treatment technology to remove the heavy metals from solution.
If hydroxide precipitation is used, the proposed process would yield two solid waste materials: (1)
the treated solid waste and, (2) the hydroxide sludge resulting from treatment of the slurry water. The
hydroxide sludge may be hazardous according to the TCLP test.
For the proposed process to be feasible, the following goals must be achieved:
1. The process must remove a sufficient amount of leachable heavy metals from the
original waste material to make it non-hazardous by the TCLP test criteria.
2. The economics of implementing the treatment process and disposing of the waste materials (treated waste, now non-hazardous, and hydroxide sludge, possibly hazardous)
must be favorable when compared to the cost of disposing of the non-treated (hazardous) waste.
A series of screening tests have been performed to determine the basic feasibility of the proposed
process with two waste materials. The results of these tests are summarized herein. The waste materials which were utilized in the treatability tests are as follows:
Electric Arc Furnace (EAF) Dust: EAF dust is a waste material generated by the ferrous and non-
ferrous metals industries. EAF dust produced by the steel industry is composed of a variety of
inorganic materials with a significant fraction being oxides of iron, zinc, lead and lesser quantities of
other metals. EAF dust is often hazardous per the RCRA TCLP test for heavy metals. The EAF dust
samples utilized in the treatability test were obtained from an abandoned stockpile of about 60,000
tons located on a site which is undergoing environmental remediation. Groundwater contamination
due to the presence of the EAF dust stockpile has been identified at the site (elevated levels of
cadmium).
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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