Abstract: Activities at a former Chemistry Triangle in Bitterfeld, Germany,
resulted in contamination of groundwater with a mixture of trichloroethylene
(TCE) and monochlorobenzene (MCB). The objective of this study was to develop a
barrier system, which includes an ORC (oxygen release compounds) and GAC
(granular activated carbon) layer for adsorption of MCB and bioregeneration of
GAC, a Fe^0 layer for chemical reductive dechlorination of
TCE and other chlorinated hydrocarbon in situ. A laboratory-scale column
experiment was conducted to evaluate the feasibility of this proposed system.
This experiment was performed using a series of continuous flow Teflon columns
including an ORC column, a GAC column, and a Fe^0 column.
Simulated MCB and TCE contaminated groundwater was pumped upflow into this
system at a flow rate of 1.1 ml/min. Results showed that 17%–50% of TCE and
28%-50% of MCB were dissipated in ORC column. Chloride ion, however, was not
released, which suggest the dechlorination do not happen in ORC column. In GAC
column, the adsorption of contaminants on activated carbon and their induced
degradation by adapted microorganisms attached to the carbon surface were
observed. Due to competitive exchange processes, TCE can be desorbed by MCB in
GAC column and further degraded in iron column. The completely dechlorination
rate of TCE was 0.16-0.18 cm^{-1}, 1–4 magnitudes more than
the formation rate of three dichloroethene isomers. Cis-DCE is the main
chlorinated product, which can be cumulated in the system, not only depending
on the formation rate and its decaying rate, but also the initial concentration
of TCE.
