Factors Affecting the Effluent Quality From Activated
Sludge Plants Treating Organic Chemicals Wastewater
W. WESLEY ECKENFELDER, Executive Director
JOHN A. ROTH, Director
ELIZABETH D. MCMULLEN, Research Associate
Center for Environmental Quality Management
Vanderbilt University
Nashville, Tennessee 37235
INTRODUCTION
The Organic Chemicals Industry is unique in that the multiplicity and the wide range of
products produced result in raw waste loads that vary markedly from plant to plant and also
exhibit a high variability within many plants. There are also wide differences in the
technology practices in producing competitive products. For example, several different
processes are used for the production of terephthalic ester, a basic chemical used in the
manufacture of polyesters. Best Practical Control Technology for this industry has
generally been based on the selection of the activated sludge process. The relatively low
soluble effluent BOD levels are technically attainable in most cases from this process under
summer operation. Variations in temperature, total dissolved solids, and product mix,
however, will result in variability in effluent quality with time. Effluent suspended solids in
total BOD are strongly dependent on the total dissolved solids content of the wastewater
and variation in temperature.
The characteristics of wastewaters from the organic chemicals industry, which
primarily influence wastewater treatment performance, are the influent wastewater
strength, the biodegradation rate coefficient k, the total dissolved solids and the wastewater
temperature. Process variables such as raw materials, technology, processing parameters,
age, product specification, and in-plant practices will also influence wastewater plant
performance. These factors were not examined in this study due to insufficient quantitative
data.
ACTIVATED SLUDGE MODEL
A kinetic model has recently been proposed to define performance of the activated
sludge process treating variable strength soluble organic wastewaters (I, 2).
VSe S
V So
k_l_ (1)
in which:
S„ = influent BOD
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