The Use of Multiple Lines of Evidence to Substantiate Anaerobic BTEX Degradation in Groundwater

Abstract

Aromatic compounds are nowadays still of major environmental concern. These compounds have been proven to be biodegradable under both aerobic and anaerobic conditions. Under anaerobic conditions several biodegradation pathways are proposed, but the bacteria and specific genes involved remain largely unknown. The detection of the actual biological degradation potential and expected kinetics of degradation in the field are therefore a challenge. Usually, a combination of different lines of evidence is used to determine and predict the biodegradation of BTEX under anaerobic conditions in the field. These include compound-specific monitoring of pollutants and intermediates in groundwater, laboratory degradation tests, stable isotope probing and application of BACTRAPs and/or microcosms. Each of these methods provides part but indirect evidence for the actual in situ biodegradation kinetics. Molecular monitoring of biodegradation of aromatic compounds in the field is not commonly used but can provide important additional evidence, especially when directed to target RNA.

Molecular analysis of functional genes involved, in combination with other lines of evidence, can be used to directly and accurately determine the degradation potential. The protocol described in this chapter allows for the accurate assessment of the BTEX biodegradation potential on-site following four steps:

• 1) Groundwater sampling using conventional, dialysis or microcosm sampling

• 2) Groundwater characterisation

• 3) Sampling protocol for molecular analyses

• 4) Molecular analyses of functional genes