Section Two
INDUSTRIAL WASTE
B. ORGANIC CHEMICALS
17    BENCH-SCALE EVALUATION OF THE ACTIVATED
SLUDGE PROCESS FOR TREATMENT OF A
HIGH-STRENGTH CHEMICAL PLANT WASTEWATER
Young-Ha Cho, Doctoral Candidate
Ernst M. Davis, Professor
University of Texas, School of Public Health
Houston, Texas 77225
John F. Andrews, Professor
Department of Environmental Science and Engineering
Rice University
Houston, Texas 77225
INTRODUCTION
This paper describes an investigation to determine whether the activated sludge (AS) process could
be used for the treatment of wastewater at the Union Carbide Corporation (UCC) plant in Seadrift,
Texas. This plant presently utilizes a waste stabilization pond (WSP) system for treatment of the
wastewater. The treatment system consists of an in-plant primary WSP and two off-plant WSPs
(secondary and tertiary WSP), run in series. The total hydraulic detention time of the WSP system is
approximately 150 days.
Several laboratory-based treatability studies have been conducted to evaluate the performance of
the WSP system and the degradability of specific chemical compounds.',2,3 From an additional
study,4 it was determined that the WSP system was stressed and occasionally operating near the limit
of its treatment capacity. The existing primary WSP plays an important role in the overall treatment
system, because it not only functions as a pH and organic-strength equalization basin, but also serves
as a "preconditioning" basin by fermenting high strength organic wastes to volatile organic acids for
subsequent degradation in the secondary WSP.4 However, in view of pending RCRA legislation
concerning the "proposed organic toxicity characteristics limits" (40 CFR Part 261: Federal Register,
July, 1988), it is possible that the primary WSP will have to be abandoned in favor of alternative
treatment options. Therefore, the main purpose of this study was to perform activated sludge treatability evaluations for the development of an alternative to the existing primary WSP treatment system.
In addition, another purpose was to determine the degradability of bis(2-chloroethyl)ether (Chlorex
or CX) and benzene (BZ) in the activated sludge process. The presence of these two chemicals in the
wastewater of the plant prompted the question of whether they could be degraded in an activated
sludge system.
MATERIALS AND METHODS
Apparatus
Bench-scale, complete mixing, continuous flow activated sludge systems, as shown in Figure 1,
were used in this study. The reactor was a 4-L plexiglass unit with an aeration chamber (3 L) and a
clarifier (1 L) separated by an adjustable baffle, which provided continuous sludge recirculation.
Wastewater feed was pumped from feed tanks to the aeration chambers and the treated effluents
flowed by gravity from settling compartments to effluent collection bottles. The feed flow rates were
regulated to provide continuous flows and desired hydraulic retention times (HRT) by using variable-
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc.
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