Contaminants & Site Conditions
FAQ Topics
- Doing Business
- Contaminants & Site Conditions
- Remediation
- Performance Monitoring
These FAQs address common questions based on the contaminants and conditions present at a site. Topics include chlorinated solvents, petroleum hydrocarbons, BTEX, metals, PFAS, groundwater chemistry, geologic conditions, and other factors that may affect treatment options.
If you already have a remediation approach in mind, see the Remediation FAQs above. For project-specific recommendations based on your site conditions, contact our team or complete Request a Site Evaluation form.
Topics
Contaminants
Tersus offers several treatment approaches for BTEX and other petroleum hydrocarbons, depending on whether aerobic or anaerobic conditions are preferred and whether chemical oxidation is appropriate.
Commonly utilized products include:
Anaerobic Bioremediation
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Nutrisulfate® BioBoost™ – sulfate-releasing amendment formulated to stimulate anaerobic biodegradation and support sulfate-reducing conditions.
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Nutrisulfate® Liquid – soluble sulfate amendment used to promote anaerobic biodegradation of petroleum hydrocarbons.
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TersOx™ Nutrients-QR – nutrient amendment that can support microbial activity under a variety of remediation conditions.
Aerobic Bioremediation
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TersOx™ Powder – oxygen-releasing compound designed to promote aerobic biodegradation of petroleum hydrocarbons.
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TersOx™ Nutrients-QR – nutrient amendment formulated to support aerobic microbial activity and enhance petroleum hydrocarbon degradation.
In Situ Chemical Oxidation (ISCO)
Tersus also offers oxidants with different reaction mechanisms and persistence characteristics that may be appropriate depending on contaminant concentrations, site conditions, and treatment objectives.
The appropriate approach depends on contaminant concentrations, dissolved oxygen, available electron acceptors, groundwater geochemistry, permeability, and the treatment objectives for the site.
Tersus offers several technologies for chlorinated solvents such as PCE, TCE, cis-DCE, and vinyl chloride.
Commonly utilized products include:
Electron Donors
- EDS-ER™ – emulsified vegetable oil substrate for Enhanced Reductive Dechlorination.
- EDS-ME™ – alcohol co-substrate for enhanced biological activity.
- EDS-QR™ – a high-purity, quick-release soluble electron donor that rapidly establishes anaerobic conditions for fast-track bioremediation projects.
Activators & Alkaline Reagents
- EDS-Activator™ – a proprietary remediation catalyst that accelerates fatty acid release, enhances hydrogen generation, and supports efficient reductive dechlorination as part of the EDS-Advanced™ platform.
Bioaugmentation Cultures
- Specialized microbial cultures may be added to accelerate reductive dechlorination where native dechlorinating populations are limited.
Geochemical and Abiotic Amendments
- BioBoost™ GeoChem – geochemical amendment designed to support reducing conditions and enhance biological treatment.
- mZVI™ – micron-scale sulfidated zero-valent iron for In Situ Chemical Reduction applications.
- ZVI-IronGel™ – injectable colloidal iron technology for treatment of chlorinated solvents.
Bioaugmentation cultures may also be incorporated where the required dechlorinating microorganisms are absent or present at insufficient concentrations.
Where dissolved oxygen is limited or depleted, petroleum hydrocarbons can be treated using enhanced anaerobic oxidative bioremediation.
This approach stimulates naturally occurring microorganisms by supplying alternative electron acceptors, such as sulfate or nitrate, to support contaminant biodegradation under oxygen-limited conditions. As biodegradation proceeds, naturally occurring electron acceptors can become depleted, so supplemental amendment may be needed to sustain microbial activity.
For petroleum hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX), sulfate is often used because it can distribute effectively through the subsurface and support long-term anaerobic biodegradation. Tersus products such as Nutrisulfate® Liquid and Nutrisulfate® BioBoost™ supply sulfate for this application.
The appropriate amendment and dosage depend on contaminant concentrations, existing sulfate or nitrate levels, groundwater geochemistry, microbial activity, and the treatment objectives for the site.
PFAS treatment generally requires a different approach than conventional bioremediation because these compounds are highly persistent and are not readily degraded under typical subsurface conditions.
Tersus can help evaluate sorption and immobilization approaches, including activated-carbon-based materials, where reducing PFAS mobility or dissolved concentrations is an appropriate treatment objective.
The suitability of any approach depends on the specific PFAS compounds present, concentrations, groundwater chemistry, hydrogeology, treatment goals, and whether the objective is containment, mass removal, or destruction.
Treatment of metals depends strongly on oxidation state, groundwater chemistry, and the desired treatment mechanism.
For some metals, treatment may involve changing redox conditions to convert the contaminant to a less mobile or less toxic form. Other approaches may rely on precipitation, adsorption, or incorporation into stable mineral phases.
For example, reducing conditions may be used to convert hexavalent chromium [Cr(VI)] to less mobile trivalent chromium [Cr(III)]. Arsenic treatment requires careful evaluation because changes in redox conditions can either immobilize or mobilize arsenic depending on site chemistry.
Tersus can evaluate site geochemistry and identify amendment approaches appropriate for the specific metal and treatment objective.
Site Conditions
Low pH can limit microbial activity and reduce the effectiveness of biological treatment. For many bioremediation processes, a pH range of approximately 6 to 8.5 is generally favorable. Electron donor fermentation can also lower pH further through the production of carbon dioxide and volatile fatty acids.
For sites with groundwater pH below about 6.0, Tersus recommends evaluating the amount of alkalinity needed before selecting a pH-adjustment amendment. An acidity titration using both groundwater and soil slurry is preferred because much of the site's buffering capacity can be associated with the aquifer solids. Tersus can assist with this evaluation and may recommend laboratory titration testing.
Depending on the results, pH adjustment may involve commercially available magnesium hydroxide or calcium carbonate products. Tersus generally recommends that pH-adjustment chemistry be supplied and injected separately from emulsified vegetable oil rather than pre-blended, because high salt concentrations can affect emulsion stability and some magnesium hydroxide formulations may increase the potential for well clogging.
Naturally occurring sulfate can sometimes provide part of the electron-acceptor demand needed for anaerobic petroleum hydrocarbon biodegradation.
Before adding additional sulfate, the existing concentration, groundwater flow, contaminant loading, sulfate-reduction activity, and treatment objectives should be evaluated.
In some cases, existing sulfate may reduce the amount of supplemental amendment required. In others, additional sulfate may still be beneficial to maintain treatment conditions throughout the target zone.
Monitoring sulfate and sulfide concentrations can help determine whether sulfate reduction is occurring and whether additional amendment is warranted.
Low-permeability formations can limit amendment distribution and contact with contaminants, so amendment selection should consider both chemistry and delivery.
Smaller-particle or soluble amendments may be easier to distribute than highly viscous or coarse materials. In some applications, longer-lasting amendments can reduce the need for frequent reinjection where access to the formation is limited.
Injection pressure, spacing, injection volume, fracture potential, formation heterogeneity, and groundwater flow should all be considered when developing the application approach.
In low-permeability settings, delivery strategy is often just as important as amendment selection.
Very high contaminant concentrations may indicate that significant source mass remains in the subsurface, including residual or mobile nonaqueous-phase liquid (NAPL). In those situations, treating only the dissolved plume can leave the remedy working against continued contaminant loading from the source.
Where significant recoverable NAPL is present, source-mass reduction should be considered before relying on plume treatment alone. For suitable sites, Surfactant-Enhanced Aquifer Remediation (SEAR) can be used under hydraulic control to reduce the interfacial forces trapping NAPL, mobilize contaminant mass, and recover it from the subsurface.
Once source mass has been substantially reduced, the project can transition to an appropriate dissolved-phase or polishing technology such as aerobic or anaerobic bioremediation, in situ chemical oxidation, in situ chemical reduction, or sorption and biodegradation.
The appropriate sequence depends on contaminant phase and mass, recoverability, groundwater chemistry, formation properties, treatment objectives, and the ability to hydraulically control mobilized contaminants.
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