MICROBIAL BEHAVIOR IN HYPERSALINE WASTES:
EFFECTS ON BOD AND DEGRADABILITY
E. M. Davis, Associate Professor
J. R. Bishop, Research Assistant
R. K. Guthrie, Professor
School of Public Health
The University of Texas at Houston
Houston, Texas 77025
INTRODUCTION
Questions have been raised in recent years about the erratic results which can be
obtained in laboratories when analyzing hypersaline wastes for biochemical oxygen
demand.   Verbal reports have indicated that if salt wastes are diluted with the standard
sewage seeded BOD dilution water, the results will be significantly higher than if
dilution water of the same salinity as that of the waste were used in the test.   One
important and obvious question immediately arises from this problem.   Which BOD
value should then be used for designing waste treatment plants?   Earlier works have
provided some preliminary answers to the question.   Kissick and Manchen [ 1 ] analyzed
two fractions of sewage in a salt water carrier and found the soluble portion to have
been metabolized at the same rate by sewage seed organisms, whereas the insoluble portion produced different degradation rates.   Manchen [2] also demonstrated that only
the degradation of suspended organic material was inhibited by elevated salt concentrations and the dissolved fraction of the BOD remained unaffected.   Davis and Petros [3]
reported that even bacteria species which are extremely tolerant of hypersaline environments react in BOD testing differently, depending on the concentration of salt in the
medium.    Kincannon and Gaudy [4,5]  found that reduced salinities may stimulate
microbial activity, resulting in increased BOD values, and in elevated salt wastes, the
organic waste materials may persist because cellular constituents present from lytic
activity may be a preferred nutrient source by other microbes over the original organic
compound.   Quantification of microbial behavior on a mass cell content basis and
identification of the bacteria which remain in hypersaline waste testing for BOD remained and was the basis for this investigation.   Additionally, an industrial waste containing
a readily degradable ethylamine complex in solution with 3.7% salt was subjected to
different standard treatment processes to determine its degradability properties.
MATERIALS AND METHODS
A glucose-glutamic acid standard solution was used for initial bacterial screening and
is described in Standard Methods [6].   BOD acclimation procedures and the dilution
bottle method used in this research investigation are also described in that publication.
In addition, a 600 mg/l sodium acetate solution was chosen for BOD testing due to its
relatively high degradability.  Manometric BODs were run using a Hach Chem. Co. BOD
apparatus.   It was chosen for accessability of sampling bacterial populations throughout
the 5-day test period.   Bacterial genera were identified by use of schemes outlined in
Diagnostic Microbiology (Mosby Co., 1974).   Continuous feed activated sludge treatment
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