ORGANIC REMOVAL EFFICIENCIES OF SECONDARY AND
TERTIARY TREATMENT AS EFFECTED BY COMBINED
TREATMENT OF A HIGH-STRENGTH FATTY ACID WASTEWATER
Foppe B. DeWalle, Assistant Professor
Edward S. K. Chian, Associate Professor
Department of Civil Engineering
University of Illinois
Urbana, Illinois 61801
INTRODUCTION
An extensive study was made for the combined treatment of a municipal sewage and
a high-strength wastewater with a COD of 49,300 mg/1 and a free volatile fatty acid concentration of 16,190 mg/1.   The waste stream representing a landfill leachate was added
to a plug-flow activated sludge unit at a stepwise-increasing volume ratio of 0.5, 1, 2, 3
and 4%, respectively.   The various influent and effluent parameters were measured at
each of the waste additions in both the test and the control unit to quantify possible
changes resulting from the combined treatment.   The effluent of the test and control
activated sludge unit was also used to evaluate removal efficiencies of tertiary treatment
processes such as membrane ultrafiltration and reverse osmosis, coagulation, activated
carbon adsorption and ozonation.
COMBINED TREATMENT OF INDUSTRIAL WASTE
Several studies have pointed out advantages of combined treatment of an industrial
waste and municipal sewage as compared to separate treatment of the two waste streams.
The significant savings in capital and operating costs is often mentioned as its largest
advantage [1].   Longdon [2] further pointed out that combined treatment reduced the
foaming and bulking of a municipal activated sludge plant receiving yeast wastes.   In fact,
many industrial wastes such as those from meat packing plants, cotton mills, metal industries [3], pharmaceutical industries [4], citrus processing plants [5], dying industry [6]
and papermills [7] are amenable to combined treatment.
In several instances, however, it was necessary either to modify existing treatment
plants or to adapt the treatment plant operation to the specific waste.   Poon [8], for
example, showed that combined treatment was successful when not more than one part
of a high-strength nylon waste was added to seven parts of municipal sewage.   Brosig et
al. |9] indicated that 90% BOD removal was only realized at hydraulic retention times
as high as 9 hr.   Often treatment plants have to be converted to accept the industrial
waste.   A conventional municipal activated sludge plant was converted to a contact stabilization plant in order to treat a nitrogen-deficient corn products waste [10].   Pilot plant
investigators of the conventional, Kraus and contact stabilization process resulted in the
selection of the latter process for combined treatment of municipal wastewater and weak
effluents of four paper mills [7].   It was further noted that nutrient addition and chlori-
nation of the return sludge were required.
Previous studies at the University of Illinois showed that a plug-flow activated sludge
unit treating municipal sewage could effectively degrade a pretreated industrial wastewater
from a chemical industry at a waste-to-sewage ratio of as high as 2.5 to 1.   Although the
effluent COD values showed substantial increase as compared to the control unit, neither
the effluent BOD nor the settleability of the sludge showed any change when the F/M
ratio of the unit remained constant.   The COD removal in the activated carbon columns
treating the effluent of the combined activated sludge unit was also not affected by the
waste additions [12].   The present study used the same activated sludge units but evaluated a landfill leachate waste stream of a substantially higher strength and of a less biodegradable nature than the industrial wastes.   Using a similar solid waste leachate stream
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