Today we know thermal remediation as a safe, practical, and cost-effective remediation method used all over the world for cleaning up contaminated soil and groundwater source zones. But why did thermal remediation become the go-to technology? In many cases, there are other remediation technologies that could be considered.
There are five major reasons thermal technology has gained that status, and today’s blog post will explain each one.
Thermal remediation is neighbor-friendly.
Until recently, the fastest, most reliable way of cleaning up contaminated source zones was to dig them up, and either treat the soil ex situ (above ground) or truck it off-site for treatment or disposal. The problem with excavation, however, is that it’s intrusive and can expose site workers and nearby residents to odors, vapors, dust, and traffic.
In situ thermal remediation (ISTR) doesn’t share those problems and is a much friendlier treatment option for neighborhoods and sites that are occupied and in active use. Treatment happens on the property, so no heavy machinery digging and hauling away contaminated soil and no odors or vapors to worry about. Once the heaters are installed, thermal technology is a safe, quiet, non-disruptive treatment process.
Thermal solutions consistently achieve stringent remedial goals.
Consistently and predictably meeting stringent remedial goals in high mass/DNAPL source zones requires an approach that can reliably overcome typical geologic heterogeneities and complex contaminant distributions and behaviors. The family of ISTR technologies offers such an approach. What makes ISTR so powerful and effective is that heating the source zone to the boiling point of water (or beyond in some cases!) results in a phase change for most organic chemicals and some metals; it makes them volatilize and become more mobile, so they can be readily and rapidly removed by typical vapor extraction approaches.
During ISTR operation, detailed temperature monitoring and process sampling are conducted and compared to the modeled performance based on mass and energy balances to verify that the target treatment area has been thoroughly and sufficiently heated and treated. Interim and final soil sampling is used to verify remedial progress and performance prior to site demobilization. The quality and veracity of the data and consistency of the end results make ISTR the best choice for sites with high-mass/dense non-aqueous phase liquid (DNAPL) source zones and stringent goals.
Thermal remediation provides quick and reliable results.
Under normal subsurface conditions, the movement of contaminants out of bypassed low permeable zones is slow, with diffusion time frames on the order of decades. Rarely do site owners have that much time to wait.
Thermal technologies have been proven to reach very low soil and groundwater concentrations by eliminating the DNAPL source, then reducing dissolved and adsorbed chlorinated volatile organic compound (CVOC) concentrations to near non-detect levels. For effective treatment, pneumatic and hydraulic control must be achieved during the heating period to prevent unwanted mobilization to areas outside the treatment zone and to efficiently remove the contaminants from the subsurface for subsequent treatment in an above-ground vapor and liquid treatment system.
ISTR technologies have demonstrated success in removing extremely high percentages of the mass (>99%) while meeting and exceeding project goals, with no rebound. ISTR offers the benefits of robust, predictable outcomes, relatively short timeframes, and site closure without follow-on remediation required.
Thermal technology is effective for recalcitrant organic contaminants in source zones.
The development of other in situ technologies, such as soil vapor extraction, surfactant and cosolvent flushing, and in situ oxidation, promised removal of source zones without excavation.
Unfortunately, for high mass/DNAPL source zones, these technologies are not as reliable or predictable as ISTR. The primary challenge for these technologies is accessing all the contaminant mass in heterogeneous source zones and overcoming the limitations of low permeable zones. ISTR doesn’t have that problem and regularly is used to treat recalcitrant contaminants in high mass/DNAPL source zones.
Thermal solutions are safe to implement.
Operation of ISTR systems involves the delivery of energy and heating the subsurface to the boiling point of water (or sometimes higher). All of these generate opportunities for injury or health concerns if not properly designed and safely performed. Fortunately, ISTR has one of the best safety records in the environmental remediation industry (and TerraTherm has an industry leading safety record—ask us about it!). You can read more about keeping thermal project sites safe here.
Thermal technology has earned its status as a go-to remediation solution. Are you thinking about implementing thermal remediation on one of your projects? You should! If so, contact me, and we will be happy to take a closer look to see if thermal is a good fit for your site conditions, schedule, and remedial objectives.
Anna Hansen has been the leader of TerraTherm’s marketing program since 2013; managing our website, social media platforms, blogs, and webinar content. Anna is also a critical member of our sales team; managing our pipeline, client strategies, sales processes, opportunity tracking, client site tours, and proposal development. She works closely with the thermal leadership team…