- Nikole Stone and Steffen Griepke
Thermal remediation is not a well understood technology, despite being a robust method that has been used to treat some of the world’s most heavily contaminated sites for the last two decades. In this blog post, thermal experts Nikole Stone and Steffen Griepke will explain the basics of thermal remediation, what thermal technologies are available, what compounds can be treated, how it is applied to a contaminated site, and what role our stakeholders play in ensuring a successful project outcome.
Want to learn even more? Register for next week’s webinar, Thermal 101: What Is Thermal Remediation and How Does It Work? This blog post will give you a head start, but during the webinar Nikole and Steffen will provide real-life examples and answer your questions about thermal remediation.
Thermal remediation consists of the application of energy, in various forms, to heat a contaminated source zone and drive off or degrade subsurface constituents. Target treatment temperatures of the subsurface vary depending on the type of constituents being treated and the thermal technology in use, but most commonly a thermal remedy involves heating the subsurface to the boiling point of water (100°C). During heating, the constituents of concern (COCs) are volatilized in the subsurface and extracted via an above-grade vapor and liquid extraction system that is designed to extract and treat the site COCs. Primary forms of vapor treatment include thermal oxidation and granular activated carbon. Liquids are typically treated using a combination of bulk-phase separation to remove free product from the liquid stream, and granular activated carbon or air stripping processes to remove dissolved COCs.
Thermal Conduction Heating (TCH)
TCH consists of applying electricity to heater elements installed in wells within the treatment area, which allows heat to dissipate conductively through the soil. This technology allows for a wide range of temperature control and flexibility within the treatment zone. TCH heaters can operate anywhere from ambient up to approximately 650 to 800°C (1,200 to 1,500°F), giving the flexibility to run at a lower temperature to enhance bio degradation or abiotic processes, or heat the treatment zone to temperatures well above boiling to remove hard-to-treat contaminants.
Electrical Resistance Heating (ERH)
ERH consists of applying electricity to electrodes that are installed in a grid-like pattern in the subsurface, and allowing the electricity to pass through the soil from one electrode to another below grade. The process of passing electricity between electrodes causes the soil to heat, due to the electrical resistance in the subsurface. ERH allows for similar flexibility and control of temperature as TCH; however, ERH requires water to be present to effectively transfer electricity in the subsurface, so ERH maxes out at the boiling point of water. Even so, this treatment temperature is applicable for the large majority of thermal projects.
Steam Enhanced Extraction (SEE)
SEE involves the direct injection of steam into the subsurface via screened wells that will allow the subsurface to heat to a maximum temperature of the boiling point of water. This method is best suited for sites with permeable geologies amenable to steam flushing, and is often used in combination with TCH and ERH.
Thermal remediation technologies can be used to treat a wide variety of chemicals. TerraTherm, a Cascade Company most commonly treats sites contaminated with volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs); however, we have also treated sites contaminated with total petroleum hydrocarbons (TPH), manufactured gas plant (MGP) coal tar, dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), mercury, etc. Because of the robust nature of thermal, a large range of contaminants—with different boiling points, molecular weights, and solubilities—can be targeted by these technologies.
Thermal can be used to treat virtually all geologies.
ERH and TCH are better suited for low permeable geologies like clays, tills, silts, and silty sands, while SEE is better suited for the permeable geologies like sands, and gravels. For bedrock systems, ERH and TCH will often be a good choice for the high porosity saturated rocks, while TCH is the better technology in more competent rock systems.
Each technology has its sweet spot geology, and sometimes a combination of thermal technologies is required to treat a site. We’ve completed projects with combinations of ERH and SEE, TCH and SEE, and TCH and ERH.
Thermal remediation is a powerful option for many contaminated sites. Hopefully, you now have a better understanding of if it’s a fit for your upcoming projects.
To learn more about thermal remediation and how it may apply to your site, register for next week’s webinar, Thermal 101: What Is Thermal Remediation and How Does It Work?
Sr. Project Engineer, TerraTherm
Nikole Stone has been a member of the TerraTherm, a Cascade Company engineering team since 2014. During her time with Cascade and legacy TerraTherm, Nikole has held the roles of Chemical Engineer I, Project Engineer and Senior Project Engineer. Nikole holds a B.S. in Chemical Engineering and has more than seven years of experience working on thermal projects. Her professional experience includes designing thermal systems, managing operational data from the field, technical writing, field sampling, and coordinating engineering and field efforts during the design, implementation, and operations phases of thermal projects. Nikole was also integral in launching the Cascade Diverse Workforce Initiative (CDWI) in 2018 and currently serves as Co-Chair on the CDWI Council.
Technology Director, TerraTherm
Steffen Griepke is the Technology Director at TerraTherm, a Cascade Company. In this role, he helps clients determine if a thermal remedy would work on their project site and, if so, which thermal technology or combination of technologies would be the most cost-effective. He then leads the design of the remedy and guides its implementation, operation, and continued optimization through project completion.
Steffen has spent nearly 20 years working with thermal technologies and has been involved in more than 75 successful projects. They have included sites from former dry cleaners, chemical manufacturing plants, chemical storage facilities, MGP sites, brownfields, military installations, and tank areas. He has utilized all three of the major thermal technologies: electrical resistance heating (ERH), thermal conduction heating (TCH), and steam enhanced extraction (SEE). As an internationally-recognized in situ thermal remediations (ISTR) expert, Steffen also supports his clients in their communication with oversight agencies and regulators.
Steffen’s experience in designing, operating, and using real-time data for optimizing thermal projects makes him an excellent partner for clients with complex sites or recalcitrant compounds.