Air and Pure Oxygen Activated Sludge
Treatment of a High-Strength Waste
L. G. KOEHRSEN, Report Department Head
E. G. ARCHULETA, Sanitary Engineer
Stanley Consultants, Inc.
Muscatine, Iowa 52761
INTRODUCTION
The wastewater treatment plant at Muscatine, Iowa, presently is receiving wastes from
both domestic and industrial sources; primary treatment is provided prior to discharge to
the Mississippi River. Specific larger industries contributing to the system include the
following: 1) H J. Heinz Company, a food processing operation; 2) Wolverine World Wide,
a leather tannery; 3) C.E. Richard and Sons, a meat packing plant; and 4) HON Industries,
manufacturers of office furniture.
The city's largest waste producing industry, Grain Processing Corporation (a wet
corn-milling operation), is not presently connected to the Muscatine sewerage system.
Operations at this plant consist of the manufacture of starch, syrup, animal feeds, alcohol,
and other corn-based products. The wastewater from this type of industry is typically rich in
carbohydrates and protein.
The city's existing primary plant has been in operation since 1965 with a design average
capacity of 8 mgd. Tannery wastewater is routed through equalization and clarification-
thickening pre-treatment facilities priot to conventional treatment with the balance of the
influent to the existing plant. Sludge handling includes vacuum filtration and landfill
disposal.
Early in 1970, the City came under order from the Iowa Water Quality Commission to
upgrade facilities to provide for secondary treatment of all wastewater. Grain Processing
Corporation was under similar order. There appeared to be a mutual advantage in
providing a single wastewater treatment facility; thus planning was initiated with the
objective of developing a combined municipal-industrial secondary wastewater treatment
plant which would provide the required 90 percent removal of BOD5.
WASTE CHARACTERIZATION
Design flows and loadings have been established following sampling and gaging of
wastewater streams, and based upon projections of future industrial activity. Figure 1
illustrates the expected 1995 flow conditions which have, in part, formed the basis for design
of secondary wastewater treatment facilities. As shown, the total design flow is 13.0mgd,of
which major industry accounts for approximately 45 percent.
Also shown in Figure 1 is a similar comparison of the BOD5 loads from the various
contributors. A somewhat different situation is apparent in this instance as approximately
86 percent of the total 96,400 pounds per day of BOD5 is contributed by industrial
operations. Grain Processing Corporation contributes the largest load with approximately
68,000 pounds per day or about 71 percent of the total. Tannery and food processing wastes
together account for approximately 15 percent of the total and 14 percent is included in the
domestic fraction.
A major concern in the design of treatment facilities is the extreme fluctuation in loads
resulting from industrial operations. Wastes from both tannery and corn processing
operations exhibit wide variations in BOD5 concentrations throughout a 24-hour period on
a day-to-day basis. Figure 2 illustrates the BOD5 of the combined municipal-industrial
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