Waste Control and Treatment by a
Corn and Soybean Processor
R. V. WILLENBRINK, Chemical Engineer
A. E. Staley Manufacturing Company
Decatur, Illinois
INTRODUCTION
The A. E. Staley Mfg. Co., which began in 1906, has spread to 137 buildings spanning 400 acres and turns out 600 different products in its major plant
located at Decatur, 111., a city of 85,000 to 90,000 population. Staley's is a
producer of numerous com starches, syrups, dextrins, dextrose hydrate, chemicals,
grocery, and feed products.
Water usage is in the order of 12 to 13 MG per operating day; 4 to 5 MG used
as process water, and 8 to 9 MG used as cooling water. Lake Decatur is the water
source. There are two sewer systems within the plant. The sanitary sewer system
handles process wastes and discharges to the Decatur Sanitary District (DSD) system. The clearwater sewer system collects and returns cooling waters back to Lake
Decatur.
All waste material discharged from the Staley plant is treated by the Decatur
Sanitary District. The Decatur Sanitary District plant is two plants in one. The
old plant consists of Imhoff tanks followed by trickling filters with clarification,
and an oxidation pond. The newer plant is essentially contact-stabilization with
each operation carried out in separate multipass aeration tanks. Stabilized sludge
and primary effluent are added step-wise to the contact tank. Digester supernatant is returned to the contact tank. The combined treatment capacity is
220,000 to 230,000 PE per day.
As is the case in most municipal-industry treatment combinations, industry
expansion and subsequent waste increases can eventually exceed treatment capacity. This was the case with Staley's and the city of Decatur until in 1965
Staley plant losses were 128, 000 PE/day (Figure 1). A good portion of the cost of
any DSD expansions historically were borne by Staley's since we were the major
waste load contributor. Due to increasing losses we were faced with a need for
further increases in treatment capacity.
Staley operates its own activated sludge treatment plant to treat the high
strength, low volume process waste streams. The system was developed and installed in 1953 and consisted of one aeration basin and a clarifier which originally
were Dorr thickeners. The aeration basin was divided into a sludge reaeration
section and aeration section. In 1957 a second aeration-reaeration basin was
added. In 1959 another existing Dorr thickener was put into operation as a surge
basin for handling of filtrates. In 1963 the surge basin was converted to an
aeration-reaeration basin (Figure 2).
Excess sludge disposal was employed twice prior to 1963, once using a
vacuum filter system and once using a nozzle centrifuge. Both operations were
unsatisfactory and abandoned. After sludge disposal was abandoned a portion of
excess sludge was sent to the reaeration sections of the aeration basins, with the
remainder lost to the sewer directly or as a consequence of bulking.
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