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1-782-
FIVE-DAY BIOCHEMICAL OXYGEN DEMAND REMOVAL
FROM RENDERING PLANT WASTEWATER
Kurt R. Marston, Chief Engineer
Franklin E. Woodard, President
Woodard and Curran, Inc.
Gorham, Maine 04038
Pine State By-Products operates a rendering plant in South Portland, Maine. Fish, poultry,
red meat by-products and sludge from wastewater treatment are processed into high-protein
feed supplements and other products.
Pine State utilizes two rendering systems, a Carver-Greenfield continuous flow system and
an Albright-Nell batch type system. The Carver-Greenfield system is used to dehydrate fat
and bone, poultry parts, fish and sludge from dissolved air flotation treatment systems.
Fish are processed on a seasonal basis. The Albright-Nell system is used to dehydrate feathers.
A schematic diagram of Pine State's process and resulting waste streams is shown in Figure 1.
During a typical day (in the fish season) the Carver-Greenfield system would be started on
poultry (offal, feet, heads, etc.) at 6 p.m. and run at the rate of 30.000 lb/hr (raw material)
for 7 hours. It would then be switched to fat and bone and run at the rate of 23,000 lb/hr
for 2.5 hours. Then it would be switched to trash fish (except menhaden) and run at 50,000
lb/hr for 3 to 3.5 hours. Finally, it would be switched to menhaden and run for four to ten
hours, depending on supply. The dissolved air flotation sludge was mixed in with any of the
raw materials except menhaden.
The Albright-Nell system is typically started up at 4:00 each Monday afternoon and run
until the feather supply is exhausted on Saturday afternoon. The approximate processing
rate is 3000 lb of raw feathers per hour.
A major problem with respect to wastewater treatment is the significant variability in byproducts processed which results in variable wastewater characteristics. A positive factor is
that operation is reasonably stable within a given season. Typical seasonal variations in raw
materials processed and resulting wastewater characteristics are presented in Table I. Table
I shows that from November to May, when the quantity of fish to be processed is low, the
BOD5 and TSS average about 25,000 and 2900 pounds per day, respectively. During the
fishing season, from May to November, the BODs and TSS loads increase substantially (to
68,000 and 4800 pounds per day).
From 1965 to 1972 wastewater from Pine State was discharged directly to Portland
Harbor. During this time period Pine State received many complains about discoloration,
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Figure I. Process schematic.
Figure 2. Treatment system.
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