48    RESPIROMETRY AS A TOOL TO ASSESS EFFECTS
OF ENVIRONMENTAL VARIABLES IN
BIOREMEDIATION RESEARCH AND FIELD TESTING
John R. Haines, Microbiologist
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Cincinnati, Ohio 45268
Edith L. Holder, Research Associate
University of Cincinnati
Department of Civil and Environmental Engineering
Cincinnati, Ohio 45221
Albert D. Venosa, Microbiologist
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Cincinnati, Ohio 45268
INTRODUCTION
The grounding of the Exxon Valdez focused attention on the use of bioremediation as an alternative cleanup tool. Biological treatment processes can convert petroleum to relatively innocuous products such as biomass, C02, and water. Although treatment rates may be slow and not all
components are completely degradable, microbial degradation has been shown to reduce the
quantity of polluting oil and the overt toxicity of petroleum components.1"3 The biodegradation
of oil has been studied and reviewed extensively, and the effects of environmental factors on petroleum degradation have been detailed.4-7 Although the interactions of different environmental
factors have seldom been examined quantitatively, several broad generalizations can be made regarding the factors that affect the rate and extent of petroleum biodegradation. First, degradation
is often slower at lower temperatures.18-9 Second, nitrogen, phosphorus, and iron are frequently
necessary to enhance degradation.7-I0~12 Molecular oxygen is usually required to support hydrocarbon degradation. Finally, hydrocarbon-degrading bacteria are quite common in the environment. Oligotrophic lake water amended with hexadecane showed maximal oxygen uptake with
added N and P, demonstrating that hydrocarbon degraders are present even in relatively pristine
waters.13 Similarly, a survey of hydrocarbon degradation over four seasons showed no effect of
temperature on hydrocarbon degradation in previously polluted areas of fresh water lakes, but
did in cleaner areas.14 These and other studies have shown the relative ubiquity of hydrocarbon-
degrading bacteria.
Assessment of biodegradability in the laboratory can be carried out by several methods. One
can incubate test compounds under various conditions and analyze for disappearance of the compound. Increases in cell mass or number in response to the presence of a compound may also be
assessed. Standard biochemical oxygen demand methods may also be used to measure
biodegradability of a compound. Use of respirometry has proved useful for measurement of
degradability of a variety of compounds under aerobic conditions.15"21 Respirometers have been
used to measure degradability of oil, volatile organic compounds, low solubility organics, phenolic compounds, and toxic compounds. Measuring oxygen uptake and carbon dioxide production
can provide the researcher with both degradability and kinetic information with regard to single
compounds or complex mixtures. Modern respirometers can provide data on oxygen uptake on a
virtually instantaneous basis and C02 production frequently.
51st Purdue Industrial Waste Conference Proceedings, 1996. Ann Arbor Press, Inc., Chelsea. Michigan 48118.
Printed in U.S.A.
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