Study of DNAPL source zone biodegradation in column experiments (THESIS VERSION)

Abstract

In order to investigate the applicability of bioremediation of tetrachloroethylene (PCE) near source zones, we carried out a set of column experiments involving biodegradation of PCE by a dechlorinating microbial assemblage and analyzed these with a numerical model. In three different setups in eight columns, biodegradation of dissolved, residual, and pooled PCE was investigated. Biodegradation in columns with dissolved PCE proceeded completely to ethene, with concentrations tested up to 0.6 mM. In columns with residual PCE, cDCE was the main degradation product and we determined that dissolution was five times enhanced in the presence of active dechlorination, which is comparable to bioenhancement factors found in the literature. Mobilization of residual NAPL due to biodegradation was also observed. These experiments were simulated by a model for which biodegradation and dissolution parameters were optimized. Modelling of the column experiments yielded information about the relevance and interplay of biodegradation and dissolution processes. The most important observation was that a better fit with the experimental results was obtained when PCE solubility and/or dissolution rate constant were included in the model.