Sandra Dworatzek (Ontario) will present “Applications of Anaerobic Benzene Bioremediation: Microbes, Mechanisms and Biotechnologies” and Brent Pautler, Ph.D. will present “Advantages of Passive Sampling as a Decision-Making Tool” at the Virtual RPIC 2021 Federal Contaminated Sites National Workshop on 15-18 November 2021.

Sandra’s co-presenters are Sandra Dworatzek & Jennifer Webb (SiREM), Elizabeth Edwards, Ph.D., O.C., Nancy Bawa, Shen Guo & Courtney Toth, Ph.D., (University of Toronto),  Kris Bradshaw & Rachel Peters (Federated Co-operatives Ltd) and Krista Stevenson (Imperial Oil).

Brent’s co-presenters are Sandra Dworatzek, Jeff Roberts, & Michael Healey (SiREM).

Sandra is a Principal Scientist with more than 25 years of experience in bioremediation of chlorinated solvents, petroleum hydrocarbons, emerging contaminants and other recalcitrant compounds. She has specific technical experience in the design of laboratory treatability studies, the scale up of growth of aerobic and anaerobic microbial cultures for bioaugmentation laboratory and field pilot tests, and evaluation of aerobic and anaerobic bioremediation, zero valent iron and chemical oxidation technologies in the laboratory. She currently provides senior technical oversight of laboratory treatability studies and the development and scaleup of new bioaugmentation cultures, including novel cultures for BTEX compounds under anaerobic conditions and aerobic 1,4-dioxane bioremediation. Sandra currently is the industry lead on a Genome Canada funded project for the commercialization of anaerobic BTEX degrading cultures.

Brent is SiREM’s Chemistry Services Manager and received his Ph.D. in environmental analytical chemistry in 2013 where he gained advanced technical experience in spectroscopy, chromatography, mass spectrometry, passive sampling, and chemistry informatics. Throughout his career, he has worked with scientists, engineers, and consultants, applying his chemistry and information technology expertise to help them solve unique problems in the laboratory and the field. His role includes managing and advancing SiREM’s passive sampling portfolio, analytical testing services while supporting Compound Specific Isotope Analysis (CSIA) business development.

The Real Property Institute of Canada (RPIC) workshop offers a wide variety of sessions on key topics affecting contaminated sites. Topics discussed at this inaugural workshop will be relevant to government and industry leaders. It is the goal of the RPIC to develop and foster a high professional standard of real property management within the Federal Public Sector, and to provide a forum for information exchange and continuous improvement.


Advances in Anaerobic Benzene Bioremediation: Microbes, Mechanisms, and Biotechnologies

 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 remediation in groundwater.

Advantages of Passive Sampling as a Decision-Making Tool

Passive sampling devices (PSDs) present numerous advantages over conventional sample collection methods for quantifying hydrophobic organic compound (HOC) availability in sediment, soil, surface water and storm water.  PSDs can provide superior convenience, cost and data quality compared to conventional grab or mechanically extracted samples. A major advantage of PSDs is their property of quantifying only the freely dissolved, bioavailable, fraction while not measuring the sorbed, or non-bioavailable fraction. Measuring only bioavailable contaminants with PSDs provides a better measure of actual toxicity and mobility for environmental receptors and a lower tendency towards toxicity overestimation than conventional sampling methods.

This presentation will highlight examples where PSDs have been used in the laboratory and in the field for decision making in site investigation and remediation, including techniques and advancements that simplify and improve ease of sampling, increase data quality and lower costs. We will demonstrate how a combination of an in-situ application of peepers as PSD to analyze sediment porewater mobility of heavy metals and ex-situ testing with polyethylene PSDs for polychlorinated biphenyl (PCB) and organochlorine pesticide (OCP) porewater concentrations was applied to site investigation. A second ­in-situ application will highlight the use of polyethylene-based PSDs to evaluate depth profiles of PCB porewater concentrations in sediment up to two feet below the sediment surface. A third laboratory case study will highlight the use of PSDs to evaluate the effectiveness of different levels of activated carbon to immobilize PCBs. The study reduced the remedial budget significantly by avoiding the addition of excess activated carbon amendment. The application of PSDs for ­in-situ field monitoring pre- and post-remedy at the site were then used to evaluate remedy performance in the field.

More Information

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For consultation regarding SiREM’s bioaugmentation cultures for BTEX remediation, contact Sandra (
For consultation on SiREM’s Passive Sampling Services, contact Brent (
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