Benzene

What is Benzene?

Benzene is a naturally occurring and industrially produced aromatic hydrocarbon widely used in the manufacture of plastics, resins, synthetic fibers, detergents, dyes, pharmaceuticals, and other chemical products. Benzene is also a major component of gasoline, crude oil, and many petroleum fuels.

Because of its widespread use and occurrence in petroleum products, benzene is one of the most frequently detected groundwater contaminants at petroleum release sites, refineries, fuel terminals, pipelines, bulk storage facilities, and former manufactured gas plant (MGP) sites.

Due to its mobility in groundwater and well-established health risks, benzene is often the primary risk driver at petroleum-contaminated sites and is closely scrutinized by regulators during site investigation and remediation.

Chemical Properties

 Benzene is lighter than water and is classified as a Light Non-Aqueous Phase Liquid (LNAPL). When released as part of gasoline or other petroleum products, benzene may dissolve into groundwater and migrate beyond the free-product source area.

Common Sources of Benzene

Benzene may be present due to:

• Petroleum releases from underground storage tanks (USTs)
• Gasoline spills and leaks
• Petroleum pipelines
• Fuel terminals and bulk storage facilities
• Refineries and petrochemical facilities
• Former manufactured gas plant (MGP) sites
• Industrial solvent usage

Benzene is commonly found alongside other petroleum hydrocarbons, including toluene, ethylbenzene, and xylenes (BTEX compounds).

Environmental Concerns

Benzene is one of the most important petroleum contaminants because of its mobility, persistence, and toxicity.

Unlike many chlorinated solvents, benzene does not undergo reductive dechlorination. Instead, biodegradation typically occurs through aerobic biodegradation or, under certain conditions, anaerobic biodegradation involving nitrate, sulfate, or methanogenic processes.

Although benzene can naturally degrade under favorable conditions, concentrations may persist for many years where oxygen and other electron acceptors are limited.

Because benzene is relatively soluble compared to many petroleum hydrocarbons, it often becomes the leading edge contaminant within groundwater plumes.

Behavior in Soil and Groundwater

Benzene contamination may exist as:

• Free-phase petroleum product (LNAPL)
• Dissolved contamination in groundwater
• Sorbed contamination attached to soil particles
• Vapor-phase contamination within the vadose zone

Benzene readily partitions from groundwater into soil gas and can contribute to vapor intrusion concerns where contamination is located beneath or near occupied buildings.

Because of its mobility and relatively slow natural attenuation under some site conditions, benzene is often a key contaminant used to evaluate plume stability and remediation progress.

Human Health Effects

Exposure to elevated concentrations of benzene may affect the:

• Bone marrow
• Blood-forming tissues
• Immune system
• Central nervous system

Long-term exposure has been associated with blood disorders and increased cancer risk. Benzene is classified as a known human carcinogen and is one of the most heavily regulated petroleum contaminants.

Because of its toxicity, benzene frequently drives remedial objectives and site closure decisions.

Regulatory Standards

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

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

Remediation Technologies for Benzene

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

Common treatment approaches include:

• Enhanced Aerobic Bioremediation: Aerobic biodegradation is often one of the most effective mechanisms for benzene destruction and may be enhanced through oxygen delivery technologies.
• Enhanced Anaerobic Bioremediation: Under appropriate conditions, benzene may also biodegrade through iron-reducing, sulfate-reducing, or methanogenic pathways.
• Chemical Oxidation: Oxidants such as persulfate, hydrogen peroxide, ozone, or permanganate may be used to destroy benzene in soil and groundwater.
• Air Sparging and Soil Vapor Extraction (SVE): These technologies are commonly used to remove volatile petroleum hydrocarbons from the subsurface.
• Surfactant-Enhanced Aquifer Remediation (SEAR):  Recovery of LNAPL and treatment of source areas are often critical components of successful remediation.

Tersus Solutions for Benzene Remediation

Tersus Environmental provides a range of technologies to support the remediation of benzene and other petroleum hydrocarbons in soil and groundwater.

Commonly utilized products include:

Aerobic Bioremediation

• TersOx™ Powder – oxygen-releasing compound designed to promote aerobic biodegradation of petroleum hydrocarbons.
• TersOx™ Nutrients-QR – nutrient amendment formulated to support aerobic microbial activity and enhance petroleum hydrocarbon degradation.

Bioaugmentation Cultures

• TersOx™ Microbe PH – a specialized microbial consortium designed to enhance biodegradation of petroleum hydrocarbons in soil and groundwater.

Anaerobic Bioremediation

• Nutrisulfate® BioBoost™ – sulfate-releasing amendment formulated to stimulate anaerobic biodegradation and support sulfate-reducing conditions.
• Nutrisulfate® Liquid – soluble sulfate amendment used to promote anaerobic biodegradation of petroleum hydrocarbons.
• TersOx™ Nutrients-QR – nutrient amendment that can be used to support microbial activity under a variety of remediation conditions.

Surfactants

• TASK™ Anionic Surfactant Blend – site-tailored surfactant system used in surfactant-enhanced aquifer remediation (SEAR) applications and source area treatment projects.

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 benzene commonly used for?
Benzene is used in the production of plastics, synthetic fibers, resins, detergents, dyes, pharmaceuticals, and numerous industrial chemicals. It is also a component of gasoline and crude oil.

Is benzene an LNAPL?
Pure benzene has a density less than water and is classified as a Light Non-Aqueous Phase Liquid (LNAPL). However, benzene is typically encountered as a dissolved constituent of petroleum products rather than as a separate free-phase chemical.

Can benzene biodegrade naturally?
Yes. Benzene can biodegrade under both aerobic and anaerobic conditions, although degradation rates depend on site-specific geochemical conditions and microbial populations.

How is benzene removed from groundwater?
Common remediation approaches include enhanced aerobic bioremediation, enhanced anaerobic bioremediation, chemical oxidation, air sparging, soil vapor extraction, and source area treatment.

Related Contaminants

• Toluene
• Ethylbenzene
• Xylenes (BTEX)
• Naphthalene
• MTBE
• Ethylene Dibromide (EDB)
• 1,2-Dichloroethane (1,2-DCA)