84    1988 GUIDELINE COMPLIANCE FOR MAJOR GRAY IRON
FOUNDRY
Lloyd W. Curry, Project Engineer
Crawford, Murphy & Tilly, Inc.
Springfield, Illinois 62702
Carey French, Environmental Engineer
Caterpillar Inc.
Mapleton, Illinois 61547-9799
INTRODUCTION
This paper describes the actions taken by Caterpillar's gray iron foundry, located at Mapleton,
Illinois, to comply with stringent discharge regulations imposed by United States Environmental
Protection Agency (USEPA) on the Metal Molding and Casting Industry. The Mapleton foundry's
only categorically regulated wastewater stream is from wet dust collection scrubbers. The process
envisioned by the USEPA was recirculation of water to the scrubbers, with a 3% blowdown to control
dissolved solids build-up.
Two pilot plants were operated to study the technical feasibility of two possible treatment
methods:
(a) A 5 gallon per minute (GPM) recirculation system with treatment of the blowdown to
achieve National Pollution Discharge Elimination System (NPDES) discharge
requirements.
(b) A once-through system with treatment to achieve NPDES discharge requirements.
The pilot plant studies indicated that the recirculation system was both difficult to operate and did
not consistently produce an effluent that met discharge limitations. Conversely, the once-through
system consistently met discharge requirements.
A full-scale once-through treatment system, based on the pilot plant study, has been constructed
and is in start-up. This paper outlines the more significant aspects of the study and construction
phases of this project.
REGULATORY BACKGROUND
On October 30, 1985, USEPA promulgated Rules and Regulations for the Metal Molding and
Casting Industry, limiting the discharge of certain pollutants to navigable waterways and publicly-
owned treatment plants. This action was in response to requirements of the Clean Water Act Amendments of 1977, and a settlement agreement to a suit brought by citizen groups.
For the Mapleton Foundry, the only categorically regulated wastewater stream is the discharge from
the dust collection scrubber system. Currently, the once-through water usage is approximately 2
million gallons per day (MGD). For the Mapleton foundry, the regulation's "normalized" dust collector water flow is 3 GPM per 1000 standard cubic feet per minute (SCFM) of air flow.
Although the guidelines were developed for an assumed blowdown of 3% of a "normalized" water
recirculation rate, the regulations limit the mass (weight) of pollutants that may be discharged, but do
not limit the water discharge volume. The regulated pollutants are: phenol, copper, lead, zinc,
suspended solids, oil and grease, and pH. The maximum daily and monthly average limits, as stated in
the regulations, are given in Table I. Table I mass values are given in terms of pounds of pollutant per
billion cubic feet of dust collector air flow. Table I concentration values are given in terms of
milligrams per liter (mg/L), for a normalized water flow of 3 GPM per 1000 SCFM of air with a 3%
blowdown.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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