goodwater

WP 6 examines the physico-chemical conditions limiting biotic reductive dechlorination of TCE in/near a TCE DNAPL zone, which influence the location of the organisms relative to the DNAPL-phase. Data show that the rate of PCE dissolution from DNAPL is at least 5 times higher in biotic compared to abiotic systems due to an increased concentration gradient resulting from the bioconversion of PCE. In contrast, TCE biodegradation in a DNAPL zone was not demonstrated before. Higher solubility of TCE results probably in toxic concentrations for dechlorination near the DNAPL. In this WP, we will examine the hypothesis that the degrading consortium is active until the distance where the flux by diffusion is identical to the degradation rate which decreases with increasing TCE concentrations. The flux by diffusion will depend on the distance and the pore structure around the DNAPL. Results will be interpreted via modelling. The chemical factors will address the effects of pH and redox on reductive dechlorination in the source zone. Dechlorination results into acidification and can inhibit dechlorination. Moreover, acidifi-cation results into increasing dissolution of Fe(III)-oxides and Fe(III) can act as a competitive electron acceptor and as such affect dechlorination. We will examine the hypothesis that TCE reductive dechlorination in the field is affected by the aquifer’s buffer capacity and Fe-oxide concentration. The main work will be performed by fellow 6 (SV: E. Smolders, K.U.Leuven). Exchange of personnel (2 months) is anticipated with HMGU regarding mathematical modelling (fellow 11, HMGU) and with fellow 12 (VITO), fellow 13 (K.U.Leuven), and fellow 14 (UGent), which carry out more applied research regarding VOCL DNAPL source remediation, VC de-chlorination and bioaugmentation strategies for treatment of VOCL-contaminated sites.