A successful biological in situ remediation of PCE contaminated aquifers requires suitable redox conditions as well as molecular hydrogen used by dehalogenating bacteria as the electron donor. Injecting an easily biodegradable auxiliary substrate allows to control both factors. The present study describes the procedural steps for a successful stimulation of biological PCE-degradation in a primary oxygen-containing aquifer. A microcosm study (level I) showed the bacterial potential of the site and the suitability of molasses as an auxiliary substrate. Using hydrogeological and geochemical field data, the amount of molasses was estimated and its zone of influence was modelled (level II). In a field test, molasses was periodically injected (170 days) accompanied by geochemical and molecular biological analysis (level III). Following the injection of molasses, methanogenic conditions as well as a significant increase of Dehalococcoides was observed. In situ biodegradation of PCE to ethene was verified by compound-specific carbon isotope analysis.
- Isotope analysis