Biodegradation of mono- and poly aromatic hydrocarbons in a contaminated aquifer originating from a former Pintsch gas factory site : Laboratory and field investigations

Abstract

This PhD thesis “Biodegradation of mono- and polyaromatic hydrocarbons in a contaminated aquifer originating from a former Pintsch gas factory site” concerns the intrinsic and stimulated biological degradation of water-soluble tar components.

Research results: 1. Intrinsic biological degradation of water-soluble Pintsch gas tar components occurs under natural conditions in the most contaminated parts of the subsurface. Degradation products, so called metabolites were detected in and around the source zone, where pure phase tar is present. 2. Benzene appears to biodegrade relatively well compared to the other tar components when nitrate is available. This effect is even observed at relatively high concentrations of benzene in the upgradient part of the source zone. 3. From microcosms prepared in the laboratory containing pure phase tar, it was observed that the ones prepared with a combination of acceptor and substrate, a range of polycyclic aromatic hydrocarbons were degraded and or immobilized into so called “insoluble skins”. This is likely caused by growth of the microbial population on substrate. 4. From the newly detected carboxylated indene compounds we introduced a proposed pathway for biodegradation of indene through carboxylation. 5. When the subsurface contained by Pintsch gas tar is bio-stimulated by nitrate additions at field conditions, lag times for the microbial population to adapt can take up to a year until detectable results occur.

These results are useful in enhancing existing biological remediation solutions. Furthermore, the investigations point towards the importance of nitrate presence in aquifers in relation to biodegradation of aromatic hydrocarbons and possibly other contaminants.