Grantee Research Project Results
Final Report: In Situ Remediation Technology (InSRT) for Remediation of PFAS Contaminated Groundwater
EPA Contract Number: 68HERC21C0044Title: In Situ Remediation Technology (InSRT) for Remediation of PFAS Contaminated Groundwater
Investigators: Holsopple, Laura
Small Business: RemWell, LLC
EPA Contact: Richards, April
Phase: II
Project Period: April 1, 2021 through March 31, 2023 (Extended to December 31, 2023)
RFA: Small Business Innovation Research (SBIR) - Phase II (2021) Recipients Lists
Research Category: Endocrine Disruptors , SBIR - Water , Small Business Innovation Research (SBIR)
Description:
RemWell’s In Situ Remediation Technology (InSRT) reactor is designed to destroy PFAS in contaminated groundwater in situ using sonolysis when deployed within a horizontal well in the subsurface. Horizontal wells passively capture and focus flow from a wide capture zone upgradient of the well. InSRT avoids expensive and energy-intensive pumping for traditional aboveground treatment, and ultimately reduces a site manager’s annual operating costs by up to 40%. RemWell successfully completed SBIR Phase I, advancing the reactor and assuring it was leak-proof, readily deployable in a horizontal well, and able to operate in situ. Phase II focused on expanding the applicability of InSRT by developing and testing three additional reactor sizes; investigating the need for and effectiveness of oxidative pretreatment to improve InSRT’s overall treatment efficiency; subjecting InSRT to a 3rd-party design review; and developing a user interface and automated control system.
Summary/Accomplishments (Outputs/Outcomes):
Task 1. Design, construct, and test three InSRT sizes. Designs and engineering drawings were completed for three reactor sizes – 10”, 12” (the original size), and 14”, where the size references the size of the horizontal well casing in which the reactor fits. We initially intended to design for an 8” reactor, however the ultrasound transducer manufacturer was unable to modify the baseline transducer to fit this smallest size. One of the three sizes (10”) was fabricated. Treatment tests were conducted in the original reactor and in the newly fabricated 10” reactor using PFAS-contaminated site groundwater, and results were compared. The extent and rate of treatment in the two reactors were nearly identical, indicating that this small modification in size, which significantly expands the applicability of the technology as the well size is optimized based on site-specific hydrogeologic properties, does not negatively impact treatment.
Task 2. Oxidative pretreatment. Pretreatment of PFAS-contaminated groundwater using the chemical oxidant activated persulfate prior to sonolysis could potentially improve the efficiency of treatment using InSRT by breaking down some of the easier-to-treat PFAS compounds, reserving sonolyis energy for the more recalcitrant compounds. Pretreatment tests were conducted using contaminated site groundwater. While pretreatment did somewhat improve the efficiency of sonolytic treatment, decreasing the treatment half-life by an average of ~14%, this modest improvement would not significantly decrease associated total treatment costs, thus would not be worth the added cost and implementation challenges of oxidative pretreatment. Results are site-specific, though are expected to be representative of many PFAS-contaminated sites. There may be sites with higher concentrations of precursor PFAS compounds that can convert to target compounds. Pretreatment should continue to be considered for such sites.
Task 3. Design review and optimization. Collaborators from the U.S. Army Corps of Engineers’ Engineer Research and Development Center (ERDC) conducted a comprehensive design review and optimization with our team and the team from Blackstone-NEY Ultrasonics, the company that manufacturers InSRT’s ultrasonic transducers, the key reactor component. Review and optimization resulted in improved body design, decreased reactor body weight, inclusion of heat and leak detection sensors, electronics cooling capability, and ease of installation via addition of an installation “handle”. Additionally, the Blackstone team worked to extend the traditional power cable length, enabling installation of InSRT in situ at lengths up to 300+ feet.
Task 4. System automation. The key parameter that can impact in situ operability is the build-up of heat within InSRTs transducer casing. Excess heat results in automatic shut-down of the unit. Internal temperature was added to InSRTs programmable logic controller (PLC) to enable better tracking of these key parameter and the operating conditions for which temperature is particularly sensitive (e.g., transducer frequency and operating power, operating duration, etc.). Humidity sensing (early indicator of potential leak) was also integrated. The PLC, when deployed in the field, can be integrated into a remote monitoring and control system (e.g., Sensophone, sensaphone.com), which enables site personnel to monitor operating conditions from the office.
Conclusions:
Overall, outcomes of RemWell’s Phase II SBIR include:
- Design drawings and assembly manuals for three sizes of InSRT reactors
- Experimental validation of two InSRT reactor sizes
- Improved understanding of design and operating factors that impact treatment efficiency and effectiveness, including:
- Oxidative pretreatment
- Operating temperature
- Frequency
- Operating power and power cable length
- Unit size
- Field-ready, optimized InSRT with deployable platform, instrumentation, and controls.
SBIR Phase I:
In Situ Remediation Technology (InSRT) for Remediation of PFAS Contaminated Groundwater | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.