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.

Chemical Properties

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 (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.

In Situ Chemical Reduction (ISCR)

ISCR technologies utilize reactive materials such as zero-valent iron to chemically reduce chlorinated solvents and accelerate contaminant destruction.

Enhanced Anaerobic Bioremediation

Bioaugmentation cultures containing specialized dechlorinating microorganisms can be added to accelerate biological degradation where native microbial populations are insufficient.

Thermal and Physical Treatment

Source areas containing DNAPL may require thermal remediation, soil vapor extraction, excavation, or other aggressive source treatment technologies prior to or in combination with biological treatment.

Tersus 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:

• EDS-ER™ — emulsified vegetable oil substrate for Enhanced Reductive Dechlorination.

• EDS-Activator™ — supplemental alcohol-based electron donor to accelerate anaerobic biodegradation.

• EDS-ME™ — alcohol co-substrate for enhanced biological activity.

• Bioaugmentation cultures containing specialized dechlorinating microorganisms.

• mZVI™ — micron-scale sulfidated zero-valent iron for In Situ Chemical Reduction applications.

• ZVI-ironGel™ — injectable colloidal iron technology for treatment of chlorinated solvents.

• BioBoost™ GeoChem — geochemical amendment designed to support reducing conditions and enhance biological treatment.

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.

Related Contaminants

• Trichloroethylene (TCE)

• cis-1,2-Dichloroethylene (cis-DCE)

• Vinyl Chloride (VC)

• Carbon Tetrachloride

• Chloroform

• 1,1,1-Trichloroethane (TCA)

• 1,1-Dichloroethylene (1,1-DCE)