Continuous Feed Centrifuge Replaces Flotation
for Removal of Excess Activated Sludge
from a Pharmaceutical Wastewater Treatment Plant
MARK R. STUMPF, Manager
Waste Control Department
WILLIAM H. HARPER, Process Development Engineer
Abbott Laboratories
North Chicago, Illinois
ABBOTT'S APPROACH TO POLLUTION CONTROL
Abbott Laboratories is a major pharmaceutical manufacturer with a number of
manufacturing plants in the United States; the plant at North Chicago being by far the
largest. This plant occupies some 56 acres and is located about one-half mile west of Lake
Michigan. At this plant we employ approximately 6,000 people and conduct extensive
manufacturing and research operations.
Two of the antibiotics produced here by fermentation are erythromycin and penicillin.
Fine chemicals produced by reaction and synthesis include sedatives, diuretics, antihypertensives, anti-coagulants, anti-convulsants, laxatives and anti-dandruff preparations.
We also manufacture intravenous and irrigation solutions and equipment, vitamin and
cough preparations, as well as animal feed and health products.
At our North Chicago plant we use a systems approach to prevent water pollution. Our
objective is to minimize the total pollution which results from production operations,
natural occurrences, and accidental spillage. To do this we conduct many different types of
treatment operations. Included among these are the recovery and recycle type of treatment
operations, cleanup of spent water, control of accidental spillage, and the operation of a
wastewater treatment plant.
Among our treatment systems, we consider the recovery group to be the most
important; more than three-fourths of our potential waste streams, expressed on a BOD
basis, are processed through recovery systems. Unfortunately, not everything can be
recovered and some wastes must be sewered.
Sanitary wastes are sent to the North Shore Sanitary District plant at North Chicago.
Sewered processed wastes are sent to the unique Abbott activated sludge wastewater
treatment plant which was developed and designed specifically for this concentrated
industrial waste stream. This plant has a hydraulic and biochemical oxygen demand (BOD)
loading capacity of 1,000,000 gallons per day and 30.000 pounds of BOD applied per day at
an average performance level of 94 percent BOD removal, with a range of 85 to 98 percent.
The BOD concentration of the sewered process waste stream averages 3000 mg/1 and
consists of residual sugars, starches, vegetable oils, and trace minerals not consumed in the
fermentation facilities as well as organic chemicals and hydrocarbons from the manufacture
of fine chemicals. This particular waste combination causes a highly filamentous activated
sludge which is difficult to remove and thicken by conventional methods.
WASTE SLUDGE, THE END PRODUCT
One of the end products of the biochemical reactions when stabilizing biochemical
oxygen demand (BOD) in an activated sludge plant is cellular matter which, under
equilibrium operation, is usually thought of as excess or waste sludge. In the presence of
excess food, the microorganisms in a normal wastewater treatment plant will multiply
rapidly. This increase in microbial population, or creation of more sludge, is the synthesis
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