19    DESIGN FOR THE REMOVAL OF ORGANIC PRIORITY
POLLUTANTS IN AN INDUSTRIAL WASTEWATER
TREATMENT PLANT
Gerald J. O'Brien, Senior Engineering Associate
E. I. Du Pont de Nemours & Company
Wilmington, Delaware   19898
INTRODUCTION
The federal EPA has issued guidelines which limit the discharge concentrations of 57 organic
priority pollutants from the organic chemicals, plastics, and synthetic fibers (OCPSF) industries to
parts per billion levels. The OCPSF guidelines for 36 of these compounds will be incorporated into the
Chambers Works (CW) site's NJDEPS permit in June 1991. A knowledge of the factors influencing
the removal of each pollutant in the wastewater is necessary to design new WWTP facilities or to
retrofit existing WWTP's for removal of these compounds and to set source reduction goals where the
limits cannot be met by a WWTP. This paper will discuss the design of a second-stage for an existing,
20 k gal/min WWTP in order to optimize the removal of those compounds which currently exceed the
OSPSF limits. A model was obtained which was based upon an experimental study of the mechanisms
for pollutant removal. The model was combined with data from the existing single-stage WWTP to
obtain scaleup factors for each problem compound.
LITERATURE SURVEY
A previous paper1 showed that the removal of priority pollutants could be enhanced by increased
temperature, sludge age, powdered activated carbon (PAC) addition, and by the addition of a second
aeration stage. An empirical relationship was used to predict the performance of the second stage
from pilot plant and full-scale data. However, it did not allow an assessment of the magnitude of the
effect of each parameter upon the removal of each problem pollutant, and the data were limited by
the large number of effluent concentrations which were below detection limits. A quantitative assessment of the removal under different operating conditions was required to determine the maximum
allowable influent concentrations which would not exceed the OCPSF discharge limits.
Most modeling efforts have focused on conventional pollutants such as five-day biological oxygen
demand (BOD) and chemical oxygen demand (COD). More recent studies have addressed specific
priority pollutants in the activated sludge process, but consensus has not been reached on a model
acceptable for design purposes. Few models address the "PACT" process, which incorporates PAC
into the activated sludge process, and those which do primarily focus on the conventional pollutants.
Garcia-Orozeo, et al.2 compared the removal of 4,6-dinitro-ortho-cresol in a synthetic wastewater for
the activated sludge and PACT processes, but the model requires experiments at several sludge ages to
evaluate the coefficients. A comprehensive study of both the activated sludge and PACT processes
was done by Weber and Jones3 for seven of the OCPSF compounds, but the PACT process was not
modeled, and a synthetic feed was used.
MODEL
The model used in this study was a modified form of the equation formulated by earlier investigators for activated sludge systems.4"6 The aeration tank was considered to be a perfectly mixed reactor,
which assumed that the concentration in the aeration tank was uniform and identical to the effluent
concentration. Lithium chloride tracer studies in the WWTP aeration tank validated this assumption.
The effluent and influent concentrations can be related through a material balance.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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