36    A CASE HISTORY OF A DIE-CASTING WASTEWATER
TREATMENT SYSTEM
David B. Froula, Project Manager
Sam E. Shelby, Jr., Principal
The ADVENT Group, Inc.
Brentwood, Tennessee  37027
Robert L. Quintilliano, Environmental Manager
SPX Corporation
Muskegon, Michigan 49443
Murl Hoover, Plant Engineer
Contech Division
Dowagiac, Michigan 49047
INTRODUCTION
A die casting and finishing operation, located in southwest Michigan, was faced with increasing
wastewater treatment costs due to increasingly stringent wastewater discharge regulations. Over the
last 10 to 15 years, this facility made several attempts at water reuse and recovery by installing oil-
water separators and an ultrafiltration/reverse osmosis system. These systems were plagued by problems and never provided satisfactory treatment. In 1988, an arrangement was made with city officials
to truck pretreated wastewater to the local POTW. A physical/chemical/biological system was
installed to pretreat the wastewater in order to meet U.S. EPA categorical discharge limits. This
system was also unable to meet the discharge limits and wastewater pretreatment and trucking to the
City were suspended. Wastewater was then hauled to a commercial facility in Detroit for treatment
and disposal. A modified two-stage physical/chemical treatment approach followed by biological
polishing was conceived, investigated and implemented to achieve the categorical limits and decrease
wastewater treatment and disposal costs. This paper presents a case history of the wastewater treatment system development and operation.
RAW WASTE CHARACTERISTICS
A summary of previous raw waste characteristics, as reported from samples collected over several
years, is presented in Table I. The current wastewater flow rate ranges from 5,000 to 10,000 gpd. It
can be seen that the wastewater has up to 2,000 mg/L of oil and grease and 1,000 mg/L of TSS. BOD,
COD, and TOC, primarily from ethylene glycol, have also been measured at high concentrations.
Heavy metals of concern are zinc, and possibly lead and copper.
Results from a series of raw wastewater samples collected at the plant over an eight day period in
1989 are also summarized in Table I. These samples consist of 6 daily composite samples and a weekly
composite. These results indicate an average total oil and grease content of 764 mg/L, an average
soluble oil and grease level of 173 mg/L and, by difference, the sum of free and emulsified oil and
grease was 591 mg/L. These samples were collected after the raw waste collection and skimming
sump. Very little, if any, free floating oil and grease was observed, indicating that most of the raw
waste oil and grease was emulsified.
Raw waste TOC levels ranged from 6,279 mg/L to 10,875 mg/L, and averaged about 8,200 mg/L.
The daily composite raw waste pH levels varied between 5.65 and 8.88, and the weekly composite pH
was 7.19.
Heavy metals data indicate that zinc is present at significant levels. Daily total zinc values ranged
from 13.90 to 33.10 mg/L, and averaged 21.77 mg/L. Comparisons of the total and soluble zinc
analyses indicate that most of the zinc is in the soluble or dissolved form.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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