The main goal of this study was to assess the potential enhancement of the naturally occurring biodegradation processes in groundwater contaminated with trichloroethene (TCE) and tetrachloroethene (PCE). Groundwater samples were taken from the monitoring wells along the groundwater flow path (from the contamination source – the former metal and ammunition factory to the receptor – the waterworks) and analyzed for the presence of chlorinated solvents. Based on these results, the hydrogeochemical characteristic of groundwater related to the Quaternary sediments (mainly gravels and sands with low total organic carbon content) was described and additionally the compound specific carbon stable isotope composition of the chlorinated ethenes was analysed.
A batch laboratory experiment was performed and the microcosms were prepared with contaminated groundwater from the studied aquifer amended with different organic substrates (molasses, lactate, yeast extract, butyrate) or EHC-L® as electron donors in order to stimulate reductive dehalogenation of TCE and PCE. Some microcosms were inoculated with allochtonic microorganisms from either an enrichment culture containing Dehalococcoides ribotype strain BTF08, or a mixed culture containing methanogenic and dehalogenation microorganisms. Dehalogenation was monitored by measuring the concentrations of chlorinated ethenes and products of their decay over time. Specific taxa of the dechlorinating microbial community of groundwater were investigated using molecular biological methods by means of taxon specific PCR. The results obtained provided information about contamination behaviour and conditions under which microbial reductive dehalogenation of PCE and TCE is the most efficient in the studied Quaternary aquifer.