How does thermal remediation work?

Thermal Remediation works by transferring heat energy from specialized heater wells directly into the subsurface (soil and groundwater) through thermal conduction (TCH). As the subsurface temperature rises toward the boiling point of water, significant thermodynamic changes occur that make trapped contaminants much more mobile and easily removable.

The remediation process relies on several simultaneous mechanisms to eliminate non-aqueous phase liquids (NAPLs) and volatile organic compounds (VOCs):

• Exponential Vapor Pressure Increase: As the ground is heated from ambient temperatures to around 100°C (212°F), the vapor pressure of the contaminants typically increases by 10 to 30 fold (and over 40 fold for specific chemicals like TCE). This massive increase in pressure causes rapid, direct volatilization, forcing the contaminants to evaporate into a gas phase.

• Boiling Point Depression (Co-Boiling): Because the contaminants are mixed with ambient soil moisture and groundwater, they exhibit "heteroazeotropic" behavior, meaning the boiling point of the entire mixture drops. This allows complex contaminant mixtures to boil and vaporize at temperatures significantly lower than their individual pure boiling points.

• Steam Stripping and Sweep: When the subsurface moisture reaches its boiling point, interstitial steam is generated. This creates a massive "steam sweep" through the soil often resulting in hundreds of pore volume exchanges of steam. The physical bubbling, agitation, and buoyancy of the steam literally strip contaminant mass from the soil and groundwater, carrying the toxic vapors toward extraction points.

• Desorption and Increased Liquid Mobility: The elevated heat reduces soil adsorption coefficients, which causes contaminants to rapidly detach (desorb) from the soil matrix. Simultaneously, the heat drops the viscosity, liquid density, and interfacial tension of trapped NAPLs, making them highly mobile liquids that can be physically pumped out of the ground.

• In-Situ Destruction: The intense heat also destroys some contaminants directly in the ground. It accelerates natural breakdown processes through chemical reactions like hydrolysis and dehydrohalogenation.

Extraction and treatment once the heat has mobilized and vaporized the contaminants, a vacuum is applied to the subsurface using a network of Soil Vapor Extraction (SVE) and Multi-Phase Extraction (MPE) wells. These extraction wells act as the primary capture points, pulling the contaminated steam, volatilized off-gases, and highly mobile liquids out of the ground before they can escape.

Once extracted, the mixture enters an above-ground treatment facility. This system employs vapor liquid separators (knock-out tanks), heat exchangers, and chilling technology to isolate the liquid and vapor phases while cooling the off-gas to remove moisture. The resulting contaminant-laden vapor is purified via granular activated carbon (GAC) or condensed through a cryogenic C3 system, ensuring only clean air is released. Simultaneously, the liquid stream is processed through a dedicated water treatment system comprising weir tanks, filters, and liquid-phase carbon before the treated water is discharged to the sewer and concentrated contaminants are collected for disposal.