PARENT SESSION
PW7 - Biotransformation / Metabolisms / Degradation
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P799) Using BOD & COD to Evaluate the Effects of Pump & Treat During Biodegradation.
Morris, Natascha*,1, Byl, Dr. Tom1,2, 1 Civil & Environmental Engineering Dept. , Tennessee State University, Nashville, Tennessee, USA2 U S Geological Survey, 640 Grassmere Park, Suite 100, Nashville, Tennessee, USA
ABSTRACT- Jet fuel spilled from underground pipelines, resulting in contamination of the karst aquifer at a south-central Kentucky airfield. Jet fuel is made up of many different aromatic rings, and branched alkanes with different biodegradation capabilities. The objective of this study was to evaluate biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in order to evaluate fuel-biodegradation capability as a response to pump-and-treat remediation in the regolith and karst aquifers. The BOD test is a measure of biologically oxidizable fuel because it measures the change in dissolved oxygen concentration as a function of aerobic-fuel biodegradation. The COD test measures fuel and inorganic components that are oxidizable by a strong chemical oxidizing agent (potassium dichromate) in an acid medium. The COD is usually greater than the BOD because more compounds, organic and inorganic, can be oxidized chemically than biologically. In other words, the COD is a measure of oxidizable fuel and reduced-inorganic chemicals, such as Fe2+, NH3, Mn2+, and S2-. The inorganic compounds contribute to the total COD in fuel-contaminated aquifers where bacteria have depleted the oxygen and the inorganic chemicals are produced through anaerobic metabolism. Seven wells were selected for this study, four wells with screens in the clay-rich regolith, and three wells with screens in the karst bedrock. The wells were also chosen because they were part of a bioslurping remediation program. Bioslurping is a modified pump-and treat program that is designed to draw air into the aquifer as it pumps water out. Water samples were collected from the wells prior to, during and after the bioslurping events. All the fuel-contaminated wells had no dissolved oxygen prior to bioslurping, and all had greater than background levels of Fe2+, NH3, and S2-. The COD due to these inorganic chemicals was calculated and subtracted from the total COD to get the fuel-COD. The BOD was also measured for these same wells. In conclusion, BOD and COD measurements appear to provide useful information with regard to biodegradation of fuels and bioslurping in the regolith and karst aquifers.
Key words: BOD, COD, Biodegradation, Pump & Treat