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Trichloroethylene (TCE)

What is Trichloroethylene?

Trichloroethylene (TCE) is a chlorinated solvent that has been widely used for metal degreasing, industrial cleaning, and manufacturing processes. TCE is a colorless, nonflammable liquid with a mildly sweet odor and was extensively utilized throughout the aerospace, automotive, electronics, defense, and metal fabrication industries.

Due to its widespread historical use and persistence in the subsurface, TCE is one of the most commonly encountered groundwater contaminants at remediation sites throughout North America. It is frequently identified during environmental site assessments, groundwater investigations, corrective action programs, and vapor intrusion evaluations.

Chemical Properties

Property Value
Chemical Name Trichloroethylene
Common Name Trichloroethylene (TCE)
Chemical Formula C₂HCl₃
CAS Number 79-01-6
Molecular Weight 131.39 g/mol
Density 1.46 g/cm³
Solubility in Water Approximately 1,100 mg/L at 25°C

TCE is denser than water and is classified as a Dense Non-Aqueous Phase Liquid (DNAPL). When released to the environment, it can migrate downward through soil and groundwater until it encounters a low-permeability layer, where it may accumulate and serve as a long-term source of groundwater contamination.

Common Uses of TCE

Historically, TCE has been used for:

  • Vapor degreasing of metal parts
  • Aerospace manufacturing and maintenance
  • Automotive manufacturing
  • Electronics and semiconductor production
  • Industrial cleaning operations
  • Chemical manufacturing processes

Although industrial use has declined significantly, legacy contamination remains widespread.

Environmental Concerns

TCE is persistent in the subsurface and can remain in soil and groundwater for decades if left untreated. As a DNAPL, even relatively small releases can create extensive groundwater plumes.

Under anaerobic conditions, TCE may undergo biodegradation through reductive dechlorination, producing daughter products including:

  • cis-1,2-Dichloroethylene (cis-DCE)
  • Vinyl Chloride (VC)
  • Ethene (the desired non-toxic end product)

Incomplete degradation can result in the accumulation of vinyl chloride, which is often more toxic than the original TCE contamination.

TCE is also a common vapor intrusion concern because volatile vapors can migrate from contaminated groundwater and soil into overlying buildings.

Behavior in Soil and Groundwater

TCE contamination is often complex because the contaminant can exist in multiple forms simultaneously:

  • Residual DNAPL trapped within soil pores
  • Dissolved contamination in groundwater
  • Sorbed contamination attached to soil particles
  • Vapor-phase contamination within the vadose zone

These multiple contaminant reservoirs can continue to release dissolved TCE to groundwater for many years, requiring long-term management or active remediation.

Human Health Effects

Exposure to elevated concentrations of TCE may affect the:

  • Central nervous system
  • Liver
  • Kidneys
  • Immune system

Long-term exposure has been associated with increased cancer risk and other adverse health effects. As a result, TCE is heavily regulated by federal and state environmental agencies and is often a primary driver for site investigation and remediation.

Regulatory Standards

Regulatory criteria vary by jurisdiction; however, the United States Environmental Protection Agency has established a Maximum Contaminant Level (MCL) for TCE in drinking water of 5 µg/L.

Many states have additional groundwater, soil, vapor intrusion, and risk-based screening criteria.

Because of vapor intrusion concerns, indoor air and soil gas screening levels for TCE are often particularly stringent.

Remediation Technologies for TCE

Several remediation technologies may be applied depending on site conditions, contaminant concentrations, geology, and cleanup objectives.

Common treatment approaches include:

  • Enhanced Reductive Dechlorination (ERD): ERD stimulates naturally occurring microorganisms that convert TCE through a sequence of dechlorination reactions ultimately producing harmless ethene. Electron donor substrates such as emulsified vegetable oil are commonly used to support this process.
  • Enhanced Anaerobic Bioremediation: Bioaugmentation cultures containing specialized dechlorinating microorganisms may be added to accelerate biological degradation where native microbial populations are insufficient.
  • In Situ Chemical Reduction (ISCR): ISCR technologies utilize reactive materials such as zero-valent iron to chemically reduce chlorinated solvents and accelerate contaminant destruction.
  • Source Area Treatment: Source areas containing DNAPL may require aggressive treatment approaches such as surfactant-enhanced aquifer remediation (SEAR), thermal remediation, excavation, or other source removal technologies.

Tersus Solutions for TCE Remediation

Tersus Environmental provides a range of technologies to support the remediation of TCE and other chlorinated solvents in soil and groundwater.

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.

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.

Surfactants & Solvents

  • EDS-Substrate Shuttle™ – a targeted substrate delivery amendment designed to improve distribution of remediation amendments in low-permeability formations and areas impacted by residual DNAPL.
  • TASK™ Anionic Surfactant Blend – a site-tailored surfactant system used in surfactant-enhanced aquifer remediation (SEAR) applications to improve recovery of DNAPL source areas containing chlorinated solvents.

Tersus also provides site characterization, contaminant flux measurement, compound-specific isotope analysis (CSIA), microbial diagnostic testing, and remedial design support to help optimize treatment performance.

Frequently Asked Questions

What is TCE used for?
TCE has historically been used for metal degreasing, industrial cleaning, aerospace manufacturing, electronics production, and other industrial applications.

Is TCE a DNAPL?
Yes. Trichloroethylene is denser than water and is classified as a Dense Non-Aqueous Phase Liquid (DNAPL).

Can TCE biodegrade naturally?
Yes. Under anaerobic conditions, specialized microorganisms can degrade TCE through reductive dechlorination, ultimately producing ethene.

How is TCE removed from groundwater?
Common remediation approaches include enhanced reductive dechlorination, bioaugmentation, in situ chemical reduction, source removal, and surfactant-enhanced aquifer remediation.

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