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Perchloroethylene (PCE)

What is Perchloroethylene?

Perchloroethylene (PCE), also known as tetrachloroethylene, is a chlorinated solvent widely used for dry cleaning, metal degreasing, and industrial cleaning applications. PCE is a colorless liquid with a mild, sweet odor and has been extensively used in commercial and industrial operations since the mid-1900s.

Because of its widespread use and historical handling practices, PCE is one of the most frequently detected groundwater contaminants at industrial facilities, dry cleaners, manufacturing plants, military installations, and hazardous waste sites.

Due to its widespread historical use and persistence in the subsurface, PCE remains one of the most commonly encountered 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 Tetrachloroethylene
Common Name Perchloroethylene (PCE)
Chemical Formula C₂Cl₄
CAS Number 127-18-4
Molecular Weight 165.83 g/mol
Density 1.62 g/cm³
Solubility in Water Approximately 150 mg/L at 25°C

PCE 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 PCE

Historically, PCE has been used for:

  • Dry cleaning operations
  • Vapor degreasing of metal parts
  • Precision cleaning of manufactured components
  • Automotive and aerospace applications
  • Chemical manufacturing processes

Although usage has declined in many industries, legacy contamination remains widespread.

Environmental Concerns

PCE 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.

PCE frequently undergoes biodegradation through a process known as reductive dechlorination, producing daughter products including:

  • Trichloroethylene (TCE)
  • 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 PCE contamination.

Behavior in Soil and Groundwater

PCE 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 PCE to groundwater for many years, requiring long-term management or active remediation.

Human Health Effects

Exposure to elevated concentrations of PCE may affect the:

  • Central nervous system
  • Liver
  • Kidneys
  • Respiratory system

Long-term exposure has also been associated with increased cancer risk. As a result, PCE is regulated by federal and state environmental agencies and is a common 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 PCE in drinking water of 5 µg/L.

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

Remediation Technologies for PCE

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 PCE 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.

Abiotic & Biotic Pathways for PCE and Break Breakdown Products

PCE PathwaysTersus Solutions for PCE Remediation

Tersus Environmental provides a range of technologies to support the remediation of PCE 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 PCE used for?
PCE has historically been used in dry cleaning, metal degreasing, precision cleaning, and other industrial cleaning applications.

Is PCE a DNAPL?
Yes. Perchloroethylene 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 and become a long-term source of contamination.

Can PCE biodegrade naturally?
Yes. Under anaerobic conditions, specialized microorganisms can degrade PCE through reductive dechlorination, producing daughter products such as TCE, cis-DCE, vinyl chloride, and ultimately ethene.

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

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