17    TREATMENT OF AN ORGANICALLY CONTAMINATED
SOIL IN ACTIVATED SLUDGE SEQUENCING BATCH
REACTORS
James P. Carmichael, Engineer
Dames & Moore
Cincinnati, Ohio 45203
Janet Rickabaugh, Research Associate
Dept. of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
INTRODUCTION
Background
The contamination of soil and ground water at a hazardous waste facility presents serious, far-
reaching environmental health problems. Demonstration of acute and chronic compound toxicity to
human and nonhuman population, coupled with compound persistence to physical, chemical, and
biological action makes the task of developing innovative treatment alternatives even more important
to the engineering and scientific community. A key parameter to selecting a treatment technology is
cost-effectiveness. Currently, the biological treatment process is regarded as one of the least expensive
technologies available. Advances in genetic research, process techniques, and innovative modifications to conventional biological processes have contributed to the success of biodegradation as a
viable treatment alternative.
The Biodegradation Task Force, Safety of Chemicals Committee in Brussels defines biodegradation
as "the molecular degradation of an organic substance resulting from the complex action of living
organisms."1 This direct interaction between microorganisms and simple and complex organic material will eventually result in the production of carbon dioxide and water. Biodegradation is considered
by many to be the single most important characteristic in predicting the fate and life of an organic
compound in the environment, which is essential to anticipating treatability.2,3 It is generally accepted
that an organic compound considered non-biodegradable will eventually biodegrade given sufficient
time and proper environmental conditions.
Soils have been found to contain a diverse population of microorganisms with considerable metabolic capabilities for degrading natural and zenobiotic (foreign) organics. Scientists have developed
categorical groupings to identify various classes of microorganisms based on the ability to function
under different environmental conditions and methods of acquiring nutrients. Some of the more
common classifications seen in the literature are: oligotrophs (active at low concentrations of organic
carbon); eutrophs (active at high concentrations of organic carbon); heterotrophs (obtains carbon
nutrients directly from a substrate); autotrophs (fixes carbon from carbon dioxide); and methylo-
trophs (oxidizes methane for nourishment).1,4 These same organism groups are largely responsible for
biological degradation in conventional wastewater treatment plans.
In assessing the biodegradability of a compound, two research avenues may be followed. The first
involves pure culture studies under defined, controlled environmental conditions. This technique
permits studies to be performed on a purely molecular level, thus providing a more detailed understanding of metabolic pathways, enzymatic reaction, and degradation by-products. In reality though,
pure culture environments rarely exist. The artificial nutrient conditions under which the pure cultures
are isolated provide limited data on predicting biodegradability of complex waste streams. This brings
up the second approach: conducting environmental or laboratory studies that more closely simulate
actual environmental conditions. This type of study will generally use a more diverse population of
microorganisms cooperatively working together to degrade pollutants and result in more useful
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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