Water Resources Research Center, University of Minnesota
Newsletter or Bulletin
Widespread use and improper disposal of chlorinated organic materials have resulted
in contamination of soils and groundwater throughout the nation. This
research focused on development of remedial technology to rehabilitate contaminated
soil and groundwater. Biological treatment was chosen because it is
environmentally sound and less costly than methods involving physical-chemical
processes. Pentachlorophenol (PCP) was used as a model compound. A mixed microbial
culture capable of utilizing PCP as a source of carbon and energy was developed from municipal wastewater treatment plant sludge. The culture was grown in a continuous flow chemostat reactor and used as the inoculum in batch
and continuous flow experiments.
PCP removal from contaminated groundwater and synthetic media was studied in
batch tests. Complete removal and stoichiometric release of chloride ions was
observed. The effects of different size sand particles on PCP biodegradation
were tested to determine the rates of removal. Short and long sand columns
also were tested to determine the rates of PCP removal under saturated and
unsaturated flow conditions. The presence of sand particles enhanced biodegradation;
small size sand particles (<25 pn) had the greatest effect. The presence
of sand particles shortened the lag phase observed when the culture was
inoculated into medium containing high concentrations (-100 mg/L) of PCP. Sand
columns operated in unsaturated flow conditions removed PCP more effectively
than saturated flow columns. The greater effectiveness of unsaturated flow
conditions appears to be due to greater availability of molecular oxygen as well as a difference in flow pattern. Enhanced adsorption of microbial cells
on sand and flow of water along grain surfaces resulted in better contact between
active microorganisms and PCP under unsaturated flow conditions.
Maier, Walter J..
On-site Biodegradation of Organic Pollutants in Contaminated Soils and Groundwater.
Water Resources Research Center, University of Minnesota.
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