ALGAL CONTRIBUTION TO BOD REDUCTION
IN AN INDUSTRIAL WASTE STABILIZATION POND
E. M. Davis, Associate Professor
Department of Environmental Science
University of Texas at Houston
Houston, Texas 77025
J. D. Martin, Production Manager
V. D. Dutcher, Department Head
J. K. Petros, Environmental Engineer
Union Carbide Corporation
Seadrift, Texas 77983
INTRODUCTION
Waste stabilization ponds have proven themselves to be effective technology for years
in municipal wastewater treatment and relatively recently in industrial waste treatment
application .   Facultative and polishing pond usage, properly applied, can yield reductions
in BOD and COD concentrations equivalent to those achieved by various modifications
of the basic activated sludge process.   In ponds of this nature, oxidation of waste loads is
achieved principally by the creation of an aerobic environment, attributable principally to
photosynthetic oxygen production.  And those algal populations which effect that production were the subject of this research.   Located on the coast of Texas near 28 N latitude, the treatment units at Union Carbide's Seadrift, Texas facility include 40 in-plant
acres (16.2 ha) of anaerobic ponds and a 140-ac (56.6-ha) pond located out of the production area.   Following those, the facultative pond, which is the subject of data presented
herein, covers a 291-ac (117.8-ha) area, has an average depth of 3.3 ft (1 m), and with a
5-mgd (18.9 x 103 m3/day) flow contains 312.9 million gal (1.18 x 106 m3) resulting in
a 62.5-day detention time.   Flow rates are undoubtedly variable. The 5-mgd flow does
occur and was chosen to use in developing some of the results which will follow.   It is
intended therefore that those data may be applicable in relating the potential usefulness
of phytoplankton communities to wastewater treatment requirements at different locations.   A more detailed description of the pond system was presented by Martin et al. [ 1 ].
LOADING CHARACTERISTICS AND PLANKTON POPULATIONS
As stated in the abstract, the entire pond system has been shown to achieve a BOD
reduction of more than 99%.   Untreated anaerobic pond influents average near or above
3000 mg/1 BOD.   Monthly averages for 24-hr composited samples are presented in Table
I for TOC, BOD, COD and solids concentrations.   The maximum BOD loading rate of
44.8 lb/ac/day (49.7 kg/ha/day) occurred in January, 1976 and the lowest rate was
11.0 lb/ac/day (12.21 kg/ha/day).   By some standards those rates may appear low for
maximum efficiency, but it is suspected that the change to the facultative environment
further reduces any refractory compounds.   Furthermore, the effluent BOD values are
obtained from unfiltered samples.   An idea of the efficiency of that facultative pond can
be developed by comparing any influent value and a value representing the second month
following, which allows for the 62.5-day detention time.
The phytoplankton populations which have been quantified in the pond effluent may
not represent the exact structure throughout the pond but are believed to be representative.
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