Modelling Bio-Enhanced TCE DNAPL Elimination in a Soil Column

Abstract

Trichloroethene (TCE), usually in the form of dense non-aqueous phase liquid (DNAPL), is a widely used degreasing ingredient causing profound soil and groundwater contamination. While bio-enhanced dechlorination of TCE to harmless Ethene is a promising technique for waste water treatment, the mechanism and related phenomenon have not been thoroughly understood, especially in groundwater. A comprehensive physical and biological based model is established here to describe the fate of TCE DNAPL resided in a soil column augmented with dechlorinators and flushed by groundwater rich in nutrients and electron donor substrate. The model considers the kinetic dissolution of TCE DNAPL, the sequential dechlorination of aqueous phase TCE, as well as the bioactivities, i.e., fermentation and mathenogenesis which directly influence the hydrogen level critical for the dechlorination rate. The toxic effect of chlorinated ethenes on bioactivity is also considered. The base case and more scenario cases simulations indicate that TCE dechlorination can greatly enhance the elimination of TCE DNAPL. For all the simulated cases with bioaugmentation, the half lives of TCE DNAPL removal are greatly reduced than that in the sterilized case. Different levels of bioaugmentation and different kinds of ED substrates can also influence the DNAPL removal rate to some extent. This model advances the understanding of bio-enhanced TCE DNAPL elimination and the reactive transport behavior of aqueous TCE, and provides a useful tool for related engineering design.