Laboratory treatability studies are often one of the first logical steps when considering In Situ Thermal Remediation (ISTR) at a given site. In relation to the full-scale source remediation, treatability studies can be a wise and relatively low cost investment in a proof of concept. You might begin with a lab study if you have a unique mix of target compounds in the treatment area, or a challenging geological matrix. Or perhaps certain stakeholders need some extra “convincing” that ISTR will work at your site. A study performed on actual site materials can quantitatively demonstrate the effectiveness of various thermal techniques (TCH, SEE, or ERH). The results provide an objective proof of concept as to whether thermal will be effective for your specific mixture of contaminants, subsurface conditions, or other unique challenges.
For over a dozen years, TerraTherm has fine-tuned our treatability study procedures to maximize the amount of useful information obtained in the lab setting. We can help tailor your treatability study to address site-specific concerns, oversee its execution, and interpret the results. Our team will also use the study results as the basis of a full-scale conceptual design. The data also provide important engineering design information about potential corrosion of treatment system components or possible composition of off-gas and condensate streams. Liquid condensate (containing condensed steam/water vapor as well as condensed vaporized contaminants) can be collected, measured and characterized (e.g. observe any layering, color changes, odors, etc.). Knowing that condensate will be produced and its composition are important to consider during project design.
The general process of a thermal treatability study:
- Collect one or more samples of highly contaminated test material and send them to the treatability laboratory for testing.
- The treatability laboratory homogenizes the materials under refrigerated conditions to minimize volatile organic compound losses, and proceeds with the untreated material characterization to get a sense of the starting concentrations of the test materials.
- A representative aliquot of material is placed in a thermal treatment reactor or column, and placed in an oven or muffle furnace for heating and/or steam injection. If ERH is being evaluated as an option, resistivity testing is performed.
- After thermal treatment, the material is re-tested for the same parameters, and contaminant concentrations of untreated materials versus treated materials are compared to evaluate the effectiveness of the various treatment options.
- In addition to bulk testing, site materials may also be subjected to a synthetic precipitate leaching procedure (SPLP) test to estimate the impact of site materials on groundwater.
- Additional geotechnical testing is often performed on the test materials and/or undisturbed site materials to aid in data interpretation.
- Physical changes to the site materials can be documented, if applicable.
Temperature monitoring, pressure monitoring, and/or pore volume removal are all key parameters to measure during thermal treatability studies to ensure that data meet the needs of your specific program. Studies can be designed to evaluate different treatment temperatures and/or different treatment durations. In addition, various amounts of soil desiccation or steam flushing can be simulated in the laboratory.
Ultimately, thermal treatability study findings aid in understanding the potential effectiveness of ISTR technologies to remove the contaminants of concern. They also support all future efforts to provide a pilot or full-scale treatment concept. The data and proof of concept they provide make them one of the best values available to anyone considering thermal remediation.
Typically, thermal treatability studies can be completed in a matter of several weeks up to several months, depending on the complexity of the testing required and the duration of thermal treatment.
If you are interested in a treatability study for your site, please fill out the site feasibility form located HERE.
The following is a response to Dr. Hatheway’s comments on Manufactured Gas Plants (MGP) at the end of this posting:
TerraTherm has experience successfully remediating sites with high boiling point compounds, including polycyclic aromatic hydrocarbons (PAHs) at former Manufactured Gas Plant (MGP) sites, polychlorinated biphenyls (PCBs) at industrial facilities, and polychlorinated dibenzo-p-dioxins/furans (PCDD/PCDFs) in various settings (including soil/sediment cleanup related to Agent Orange storage at Danang airport in Vietnam).
Specific to MGP sites, TerraTherm offers three levels of in-situ heating, each with different benefits:
- Level 1: Thermally-enhanced free product recovery (low temperature of ~80°C);
- Level 2: Volatile organic compound (VOC) removal and material stabilization (mid temperature of 100°C); and
- Level 3: Semi-volatile organic compound (SVOC) removal (higher temperature of 325°C).
At any given site, one or more levels might be used, depending on the project’s remedial goals. For example, some projects might begin with Level 1 and proceed directly to either Level 2 or 3.
In 2004-2005, TerraTherm demonstrated success with all three levels of heating at a project for National Grid in a former MGP in North Adams, MA. A detailed white paper summarizing this project is available for download on our website here: Demonstration of Three Levels of In-Situ Heating for Remediation of a Former MGP Site, 2006
During Level 1 of the National Grid North Adams project, we recovered over 16,000 gallons of coal tar product. Prior to heating, the product’s high viscosity had prevented recovery of more than a few pints.
A summary of the railyard evaluation for download on our website here: In-Situ Thermal Treatment of MGP Waste and Creosote
Refer to the “Level 2 Heating” section of the paper. In general, TerraTherm recommends ISTS for in situ thermal treatment of MGP constituents, especially below the water table. The EPRI study demonstrated that we can reduce the leachability of BTEX and naphthalene by several orders of magnitude by heating to 100°C and thoroughly steam-stripping off the VOCs, without dewatering. The higher-molecular weight PAHs are left behind as an immobile solid which resembles asphalt. There are similarities between this end material and the materials used in our roads and parking lots – they may contain significant amounts of PAHs, but they pose a minimal risk since the PAHs are immobile and not leachable. More information about the ISTS process is available on our website here: http://terratherm.com/projects/applications/mgp.htm
Level 3 (high temperature heating over 300°C) thermal treatment has been successfully demonstrated at several sites, including the National Grid North Adams site and the Southern California Edison (SCE) site in Alhambra, CA. Overall, TerraTherm’s In-Situ Thermal Remediation (ISTR) technologies have reduced VOC and SVOC (including PAHs such as benzo(a)pyrene) concentrations >96%. A table of individual VOC/PAH reductions for Level 3 heating from the National Grid North Adams site is shown below:
Additional information on the Level 3 heating approach is described in the following white paper available to download on our website: In-Situ Thermal Treatment of MGP Waste and Creosote
Please refer to the “Level 3 Heating” section of the paper.
Whether the goal is to remove mobile NAPL, stabilize material in-situ, or thermally destroy PAHs in situ, TerraTherm’s ISTR and ISTS technologies have proven to be a cost-effective and effective remedial solution for MGP sites.