es9905389_si_001.pdf (239.58 kB)
Relationship between PCB Desorption Equilibrium, Kinetics, and Availability during Land Biotreatment
journal contribution
posted on 2000-05-06, 00:00 authored by Upal Ghosh, A. Scott Weber, James N. Jensen, John R. SmithThe purpose of this research was to study the changes in
polychlorinated biphenyl (PCB) availability as measured
by desorption equilibrium and kinetics from industrial lagoon
sediments collected at different times during a 24-month
period of pilot-scale land biotreatment. During biotreatment,
reductions of the lower chlorinated PCB congeners in
the industrial lagoon sediments were observed. On the basis
of past work on soils and sediments, it was originally
hypothesized that these reductions in PCB concentration
would result in reduced PCB availability. To evaluate this
hypothesis, equilibrium partitioning studies and desorption
kinetic studies were conducted with the industrial
lagoon sediments (containing 0.91% oil and grease) as a
function of biotreatment duration. Contrary to initial
expectations, equilibrium aqueous total PCB concentrations
increased with PCB loss during land biotreatment. This
behavior was attributed to the association of PCBs with a
waste oil phase in the lagoon sediment and an oil
phase loss rate greater than the PCB loss rate during the
biodegradation study. Maximum PCB desorption rates
for the lagoon sediments also changed with biotreatment.
A two-phase desorption behavior characterized by fast
and slow desorbing fractions were observed. The estimated
fast pool fraction for each PCB homologue decreased
with biotreatment time, suggesting preferential removal of
the PCBs from the fast pool during the bioremediation
process. Although PCB availability based on estimated fast
pool fraction decreased with biotreatment, availability
based on aqueous equilibrium measurements increased
with biotreatment over the 24 months of study.