Jeff Roberts (Ontario) will present “Advances in Enhanced Anaerobic Bioremediation of Recalcitrant Chemicals”, Phil Dennis (Ontario) will present “What Your Bugs are Trying to Tell You – Illuminating Subsurface Conditions by using Microbial Communities as Biosensors”, and Brent Pautler, Ph.D. (Ontario) will present “Advantages of Passive Sampling as a Decision-Making Tool and its Application to Contaminated Groundwater Upwelling”  at the virtual AquaConSoil.

Jeff’s co-presenters are Sandra Dworatzek and Phil Dennis (SiREM).

Phil’s co-presenters are Ximena Druar, Melody Vachon, Taylor Aris and Jennifer Wilkinson (SiREM)

Brent’ co-presenters are Jeff Roberts, Michael Healey (SiREM) and Jason Conder (Geosyntec Consultants).

Jeff is the Operations Manager at SiREM with extensive technical experience in the laboratory assessment and field implementation of soil, sediment and groundwater remediation technologies at sites containing contaminants including chlorinated solvents, petroleum hydrocarbons, emerging contaminants and other recalcitrant compounds. Over the past 18 years he has conducted and managed hundreds of bench-scale batch and column treatability studies and has technical experience in the growth, scale up and field implementation of several anaerobic microbial cultures for bioremediation remedies. Jeff has several years of passive sampling experience and was a lead member in the development of the SP3™ sampler.

Phil is a Principal Molecular Biologist with more than 20 years of experience focused environmental microbiology, molecular genetic testing, enhanced bioremediation and technology commercialization. He currently directs the molecular testing services, next generation sequencing and is the innovation lead for SiREM’s research and development program. He has also played a leading role in developing relationships with many universities and serves on the Board for University of Waterloo Center for Microbial Research.

Brent is the Chemistry Services Manager with a Ph.D. environmental analytical chemistry 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 Photonics business development.

AquaConSoil started in the 1980s in 1985. Since then, the conference was organized every two years. AquaConSoil welcomes delegates from all over and outside Europe, with representatives from science, policy and businesses / industry. In the first decades the symposium was called ConSoil and was strongly focused on contaminated soils. In the last decade, the scope broadened and since the Barcelona conference in 2013, the symposium is called AquaConSoil. The name change represents the necessary systems-thinking for sustainable use and management of soil, water and sediments. The broadened scope is also reflected in the topics of the conference. In addition to dealing with contaminated soil, water and land, topics are programmed on the link between the soil-sediment-water-system and social challenges and goals (e.g. the sustainable development goals of the UN); “land stewardship”; the use of ecosystem services; circular economy; digital opportunities; and the link with social, financial, legal and policy aspects.


Advances in Enhanced Anaerobic Bioremediation of Recalcitrant Chemicals
Jeff Roberts, Sandra Dworatzek and Phil Dennis SiREM, Guelph, Ontario

Bioaugmentation with dechlorinating cultures is an established remediation technology for the enhanced anaerobic bioremediation of chlorinated solvent contaminated sites.  Specific dechlorinating bacteria and functional genes are well known and able to dechlorinate chlorinated solvents.  Dehalococcodies (Dhc) can completely dechlorinate chlorinated ethenes to ethene, and Dehalobacter (Dhb) is involved in chloroform and 1,1,1-trichloroethane dechlorination.

There are other microorganisms that have significant roles in dechlorination but are less well known and tested for less frequently. Dehalogenimonas (Dhg), which can dechlorinate trans-DCE, chlorinated propanes and more recently has been reported to dechlorinate vinyl chloride (VC) to ethene. Geobacter species are capable of dechlorinating high concentrations of PCE and TCE and may play a role in DNAPL dissolution as well as participating in biogeochemical reduction processes at many sites in conjunction with sulfate reducing bacteria (SRB).  Cultures for anaerobic benzene, toluene and xylene (BTX) degradation are now becoming available and this widens the number of sites and contaminants for which bioaugmentation can be considered.

Recently, there has been 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 now renamed as Thermincola spp.).). ORM2 and Thermincola related microbes have been detected in almost every established benzene-degrading enrichment culture worldwide and are frequently present in benzene-contaminated groundwater.  Four field pilot applications (October 2019, November 2019, April 2020 and October 2020) are currently being monitored. These first-to-field projects 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.

Bioremediation for chlorinated solvents and BTX compounds has the potential to decrease remediation time frames and increase the range of sites to which bioremediation is applicable.  This presentation will discuss recent advancements in bioaugmentation cultures are provide case studies where bioremediation was the remedy of choice at chlorinated solvent and petroleum hydrocarbon sites.

What Your Bugs are Trying to Tell You – Illuminating Subsurface Conditions by using Microbial Communities as Biosensors

Philip Dennis, Ximena Druar, Melody Vachon, Taylor Aris and Jennifer Wilkinson

Specific microorganisms grow within set limits of temperature, pH, salinity, dissolved oxygen, nutrients, toxicity and other variables responding to their environment by increasing under ideal conditions or declining under adverse conditions. Therefore, the composition of microbial communities provides a window to view what microbes are experiencing in the subsurface. Our ability to use microorganisms as “biosensors” to better understand the subsurface environment is increasingly practical as cost-effective characterization of microbial communities becomes routine. Microbial community molecular characterization has been performed for decades using methods such as cloning combined with Sanger sequencing but these were expensive and time consuming. The advent of next generation sequencing (NGS) technologies has revolutionized our ability to routinely and characterize microbial communities at much lower cost.  The use of NGS is now routine to understand the capabilities of microbial communities, such as the ability to degrade specific contaminants.  A variation in the way we look at microbial composition data is to view microbes as biosensors that allow us to better understand the environments in which microbes live, this can be approached in several ways.

  1. Microbial diversity is easily determined by NGS and can be very informative of overall compatibility of conditions for microbial growth with lower diversity often signaling more challenging geochemistry or toxicity.
  2. The detection of high number of microbes with a particular metabolic strategy can help determine the dominant conditions in the subsurface (e.g., aerobic, nitrate, sulfate reducing etc.). Also due to the tenacity of living microbes, and the stability of microbial DNA in the subsurface, NGS also has the potential provide indications of previous transient conditions, such as infiltration of nutrients, aerobic groundwater or toxicity.
  3. Microorganisms are adept at finding niches, such as interfaces, where conditions are not reflected in “bulk” parameters. For example, the pH of groundwater samples, may not be indicative of the full range of pH conditions in an aquifer when solids are considered.
    In addition to measuring dominant community members, the sensitivity of NGS methods allows detection of microbes that may be present in relatively low numbers in micro-niches, while at the same time providing clues to the heterogeneity of the subsurface microbial environment.
  4. Detections of obligate degraders of particular compounds can be particularly useful including obligate degraders of hydrocarbons, chlorinated solvents and polycyclic aromatic hydrocarbons which can provide clues regarding the presence of particular compounds that are, or were, present at a site and that may not always be apparent in groundwater measurements due to low concentrations or partitioning into solids.

This presentation will review traditional site groundwater parameters from hydrocarbon, chlorinated solvent, and nitrogen compound contaminated sites in relation to microbial community profiles to better understand the additional insights NGS can provide regarding subsurface conditions such as contaminant presence, distribution, toxicity and the subsurface niches and the resultant increases in our understanding of the potential range of biodegradation pathways possible particularly for natural attenuation remedies. 

Advantages of Passive Sampling as a Decision-Making Tool and its Application to Contaminated Groundwater Upwelling

Brent G. Pautler, Jeff Roberts, Michael Healey, Jason Conder

Passive sampling devices (PSDs) present many advantages over conventional sampling methods for quantifying the availability of hydrophobic organic compounds (HOC) and inorganic compounds in sediment, soil, surface water and storm water in terms of cost and data quality. PSDs provide data to estimate contaminant bioavailability and toxicity to environmental receptors that are more accurate than conventional grab or mechanically extracted samples, as PSDs quantify freely dissolved contaminant concentrations (Cfree) as opposed to total mass including sorbed fractions. Measuring only bioavailable contaminants with PSDs provides a better measure of actual toxicity and mobility for environmental receptors and decreases toxicity overestimation compared to  conventional sampling methods (e.g., core collection, porewater extraction).

PSDs have been used in the laboratory and 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. PSDs can be deployed directly in-situ to capture the influence of groundwater flux, changes in field conditions and the heterogeneity of a site on the freely dissolved concentrations of the compounds of interest.

In a recent case study, PSDs were used to assess groundwater upwelling of parent and alkylated polycyclic aromatic hydrocarbons (PAH) concentrations in sediments and surface water at a site adjacent to a former wood preserving facility. The use of Cfree results indicated distinguishable groundwater discharge zones at the site, and that if corrective action were required for the sediments, it would be of limited spatial extent reducing remediation costs.  This case study, in addition to abundant laboratory data, illustrates how good site management practices and efficiencies can be realized by using passive sampling at contaminated sediment sites.

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