Elizabeth Edwards is a Professor in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto. Dr. Edwards is internationally known for her work on anaerobic bioremediation and is currently co-investigator with SiREM on a Genome Canada project focusing on the application of anaerobic BTEX degradation pathways.

What is it about BTEX contamination in aquifers that make it such a challenge?

EE. The group of compounds referred to as BTEX represent the most water soluble of the petroleum hydrocarbons like gasoline or crude oil, so they sorb less and migrate further with groundwater flow. Benzene is a particular challenge as it is by far the most toxic of the BTEX compounds (a proven human carcinogen) and is more recalcitrant under anaerobic conditions.

What are the advantages and disadvantages of anaerobic versus aerobic processes for BTEX contamination?

EE. Aerobic processes are very good for BTEX. These compounds are great substrates for all kinds of aerobic microbes. Because of this, any oxygen present rapidly gets consumed. Then you either must re-oxygenate somehow or rely on anaerobic processes. Adding oxygen in sufficient quantities is difficult or impossible at many sites, and thus anaerobic processes are desirable.

Our theme in this issue is treatability testing, can you explain how these studies are important for your research?

EE. Treatability studies are particularly useful at 1) determining if microbes capable of degrading your compounds of interest are present in samples from the site and thus likely active at the site and 2) for comparing relative impacts of aerobic or anaerobic conditions and amendments of different kinds on degradation rates and extent. A microcosm enables a closed mass balance, and thus a better handle on the processes within. And when you do have activity in a microcosm, it is the perfect start for a subsequent enrichment process. Eventually a stable enrichment culture is obtained for further in-depth study.

You were recently awarded the Killam Prize for your work in bioremediation of chlorinated solvents, do you see potential for bioaugmentation of BTEX as it is used currently for PCE and TCE?

EE. I have been working on anaerobic BTEX degradation, for 30 years. This process is reliable and very effective, particularly for toluene and xylenes and the process is comparable in rate to TCE dechlorination. However, benzene is a different story. While there is plenty of energy in the benzene molecule to fuel anaerobic microbial degradation, you have to break the aromatic and symmetrical structure of benzene to unlock and breakdown the molecule. As a result, benzene biodegradation in the absence of oxygen is very much slower than toluene. And this is a major drag, because benzene is way more toxic. However, I am confident that once we understand how microbes do this, that we will be able to speed up the reaction, or at least create the conditions to promote the reaction consistently in situ.