Sandra Dworatzek, (ON) will present “Advances in Anaerobic Benzene Bioremediation: Microbes, Mechanisms and Biotechnologies” at the Alaska Forum on the Environment at the Dena’ina Center in Anchorage, Alaska on February 11, 2020.

Sandra’s co-authors are Jennifer Webb (SiREM); Elizabeth Edwards, Nancy Bawa, Shen Guo, Courtney Toth (University of Toronto); Kris Bradshaw, Rachel Peters (Federated Co-operative Ltd.); and Krista Stevenson (Imperial Oil).

Sandra is a Principal at SiREM, with more than 17 years of experience focused on oversight of laboratory treatability studies and the development and scaleup of new bioaugmentation cultures.

The Alaska Forum on the Environment is a statewide gathering of environmental professionals from government agencies, non-profit and for-profit businesses, community leaders, Alaskan youth, conservationists, biologists, and community elders. The Forum provides an opportunity for State, local, Federal, military, private, and Native leaders and professionals to come together and discuss the latest projects, processes, and issues that affect native Alaskans.


Benzene, toluene, ethylbenzene and xylene (BTEX) are widespread groundwater pollutants. Groundwater contamination with benzene is of particular concern due to its persistence in anoxic environments and confirmed carcinogenicity. Intrinsic anaerobic processes impact the fate of BTEX as well as other hydrocarbons at petroleum contaminated sites. Recent research has shown that anaerobic bioremediation processes represent viable options for plume control and site cleanup for BTEX. Benzene, the most toxic of these compounds, is also the most challenging for bioremediation, because the requisite microorganisms are relatively difficult and slow growing and reaction mechanisms are not well understood. Thanks to molecular genomics, the microorganisms responsible for benzene transformation have been identified and bioaugmentation cultures are now being grown in volumes sufficient for field application.

This presentation highlights significant milestones in characterizing anaerobic benzene biodegradation and their applications to developing better groundwater bioremediation solutions. It has recently been documented that anaerobic benzene biodegradation is catalyzed by a very narrow subset of microorganisms. Two such microbes reside in a methanogenic consortium (DGG-B; harbors Deltaproteobacteria ORM2) and a nitrate-reducing consortium (NRBC; harbors Peptococcaceae sp. Pepto-Ben). ORM2 and Pepto-Ben-like microbes have been detected in almost every established benzene-degrading enrichment culture worldwide and are frequently present in benzene-contaminated groundwater. In nature, however, their concentrations are often several orders of magnitude too low to contribute to active benzene biodegradation. Indeed, this emphasizes that effective anaerobic benzene bioremediation technologies should aim to enrich or augment ORM2 and Pepto-Ben-like microbes in situ.
Results from laboratory treatability studies demonstrated enhanced benzene biodegradation rates with DGG-B bioaugmentation and provided information to aid in field pilot-test design. One field pilot-test performed in November 2019 at a site in Saskatchewan  included three injection points, two of which received up to 10 liters of the DGG-B culture. A third injection point  received killed culture, which will serve as a control to rule out if dead cells, or media components, can promote benzene degradation. It is anticipated that benzene degradation rates will be accelerated in situ through bioaugmentation as observed in corresponding treatability studies. This first-to-field project will establish clear guidelines and approaches for using these novel bioaugmentation cultures, including a better understanding of dosing requirements, timeframes for obtaining results and ranges of conditions over which the cultures are effective. As with chlorinated solvents, bioaugmentation for BTEX compounds has the potential to decrease remediation time frames and increase the range of sites to which bioremediation is applicable providing a much-needed, cost-effective alternative for BTEX h3>More Information

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