The Role of Pretreatment in the Removal
of Organics From Industrial Wastewater
JIM M. ELLER, Manager
Engineering Science, Inc.
Houston, Texas 77058
EARNEST F. GLOYNA, Dean
College of Engineering
University of Texas
Austin, Texas 78712
INTRODUCTION
Pretreatment is usually required to remove suspended matter, but the removal of
soluble organics during pretreatment should not be overlooked. The objective of this paper
is to establish the importance of lime pretreatment for removal of organics. Specifically,
case histories are provided to illustrate the role of pretreatment for the removal of 1)
insoluble hydrocarbons, 2) soluble and insoluble hydrocarbons plus inorganic particulates,
3) soluble hydrocarbons and co-precipitated hydrocarbons, and 4) organic particulates and
precipitated inorganics. The scope of this paper is to include discussion on: 1)
neutralization, 2) coagulation, 3) flocculation, and 4) gravity separation.
The design of industrial wastewater treatment plants, usually entails three major
efforts: 1) a detailed wastewater characterization; 2) evaluation of appropriate treatment
processes; and 3) designing an efficient facility that may be operated easily and one in which
expansion and process changes can be made with minimum difficulty. As industrial
operations continue to grow in complexity it is necessary to evaluate a greater variety of
treatment alternatives. In these evaluations of alternative processes, it is highly probably
that traditional biological treatment by itself will not always provide the most feasible
answer. Indeed, complex industrial wastes usually require pretreatment before secondary
biological or tertiary treatment is even possible (1).
EXAMPLE WASTE SOURCE
Three case histories have been chosen to depict the potential of lime coagulation and
sedimentation for pretreatment of industrial wastewaters. Table I presents some of the
common elements of these three wastes. These examples include studies of waste derived
from a projected regional treatment system, a typical large oil refinery with associated
petrochemical facilities, and and a synthetic fibers plant (2).
The regional treatment system derived wastewaters from nine industrial and one
municipal source. The largest single contributor was a chemical installation utilizing
approximately 2,500 batch processes simultaneously. The pH of the commingled waste
varied between 2.1 and 9.4 with a mean of 3.0 ±0.8. The COD, BOD5 and TSS, respectively,
were 602 ± 147 mg/1, 250 ± 86 mg/1, and 46 ± 16 mg/1. Initial wastewater characterization
and bench-scale studies indicated that biological treatment would be effective, if
pretreatment could maintain the characteristics of the commingled wastestreams within
reasonable limits. These preliminary data led to construction and operation of a 50 gpm
pilot unit. Primary treatment consisted of equalization, two-stage lime neutralization and
clarification. As the pH was increased to 7, large amounts of organic materials could be
observed coming out of solution.
The wastes from the large integrated refinery-petrochemical plant are fairly typical of
this type of facility. Roughly 10 percent of the wastewater emitted from the complex
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