DEMONSTRATION OF A MUTANT BACTERIAL ADDITIVE FOR
ENHANCEMENT OF OPERATIONAL STABILITY IN OXYGEN
ACTIVATED SLUDGE
George T. Thibault, Vice President
Polybac Corporation
Whippany, New Jersey 07981
Kenneth D. Tracy, Vice President
Environmental Dynamics, Inc.
Greensboro, North Carolina 27407
INTRODUCTION
Problems are frequently encountered in the operation of wastewater treatment facilities
despite the fact they may be well-designed. This is particularly the case in the treatment of
petrochemical wastewaters because of variable loadings of insoluble, emulsified, and soluble
hydrocarbons. This paper concerns itself with the solution of operational problems in a new
UNOXR oxygen activated sludge system treating such a wastewater (Figure 1). Specifically,
the wastewater is generated in the production of the following major products: olefins,
simple and complex alcohols, organic acids, and synthetic rubbers.   Table I shows the
average design parameters for the treatment system.
API SEPARATORS (2 - PARALLEL)
DISS0LVE0 AIR FLOTATION (2 - PARALLEL)
EQUALIZATION  4 4 4  ALCOHOL SEWER
TRICKLING FILTERS (2 - SERIES)
OXYGEN ACTIVATED SLUDGE (2 - PARALLEL)
Figure 1.   Flow scheme.
Several severe operational problems surfaced during the first few months following startup. Influent BOD5, TOD, and TSS levels routinely exceeded the design conditions. Shock
loadings of alcohols and insoluble and emulsified oils produced foaming and solids-stabilized
emulsions. These emulsions periodically accumulated on the clarifier surface as a thick blanket and eventually washed over the effluent weirs resulting in a deterioration of effluent
quality. Attempts to resolve this solid-liquid separation problem with antifoams and inorganic and organic coagulants were largely unsuccessful and were also expensive. Another
approach involved increasing the solids residence time (SRT) of the system from 7 days to
the design value of 10 days in an effort to improve the degradation of insoluble and emulsified hydrocarbons. This approach led to failure of the clarifiers by pushing the applied solids
flux beyond its limiting value, thought to be 30 lbs/ft2-day.
Earlier work by the same company [ 1 ] had demonstrated that it was possible to improve
hydrocarbon degradation rates and solid-liquid separation in refinery activated sludge cultures
by inoculation with a mutant bacterial additive, PHENOBAC^ Mutant Bacterial Hydrocarbon
Degrader. The product is a freeze-dried formulation of a number of pre-selected, adapted
mutant microorganisms. Each microbe in the formulation is selected for its capability to
degrade a specific class of hydrocarbon compounds. The remainder of this paper details the
solution of the aforementioned problems in the UNOX system by biomass augmentation
with PHENOBAC.
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