TESTIMONY OF LINGKE ZENG, REMEDIATION SPECIALISTLANGAN ENGINEERING AND ENVIRONMENTAL SERVICES, INC.BEFORE THE US CONGRESSIONAL PFAS TASK FORCE
May 6, 2019
Chairman Kildee and members of the PFAS Task Force, thank you for the opportunity to discuss PFAS treatment technology with everyone today. I am presenting this testimony on behalf of Stewart Abrams, who is the director of remediation technology at Langan Engineering. Mr. Abrams had hoped to attend this event, but he had a schedule conflict. So as a leader in Langan’s remediation technology group, I was able to step in for him. I will offer some insights into the opinions and the general consensus among remediation and water treatment professionals concerning PFAS treatment technologies. Some of the terms that I will use may not be familiar, so please let me know if you have any questions about some of the technical concepts I will present.
For any contaminant, treatment is achieved either through either physical removal from the water or, better yet, through a means to destroy the chemical, rendering it harmless and detoxifying the water. PFAS are exceptionally stable molecules. The contaminants’ stability comes from PFAS molecules’ carbon-fluorine chemical bond that is very strong and difficult to break. Sustained Congressional support into the development of remediation techniques in general has occurred during the last several decades, including funding of destructive methods for other common contaminants. However those methods for the most part do not apply to PFAS, so effective, practical, and cost effective technologies that can destroy PFASs remain to be identified and developed.
Technologies generally fall into three categories: commercially field implemented, limited application, and technologies in the R&D phase. I will also discuss ex-situ treatment versus in-situ treatment. Ex-situ treatment takes place after the impacted soil, groundwater or surface water are placed into a treatment system. In-situ treatment technologies are methods that treat the contaminant(s) in place, that is, underground where the contamination lies.
In-situ treatment can target the long term sources of the contamination and effectively reduce the impact on the environment. Field implemented technologies for PFAS in-situ treatment mainly focus on immobilizing the contamination, but not destroying it. This is accomplished either through adsorption or stabilization techniques. For in-situ adsorption technologies, pulverized microscopic activated carbon powder (sometimes called “activated charcoal”) is injected into the ground to reduce PFAS groundwater concentrations. The PFAS then sticks or “adsorbs” to the carbon. With in-situ stabilization technologies, a cement-based product can be mixed with soil to encapsulate the contaminant, essentially turning the subsurface into a concrete block from which the PFAS cannot escape. The long-term effectiveness of these treatments over many decades is not yet fully understood.
As mentioned, ex-situ refers to the groundwater, surface water or soil being physically removed from the ground and placed into a treatment system. Similar to in-situ treatments, the commercially available treatment technologies are also adsorption technologies. A municipal water supply that relies on deep wells must recover and treat impacted groundwater through ex-situ water treatment systems. Activated carbon (in a more granular form) and ion-exchange resins are the most common media. Ion exchange techniques are basically high-tech versions of the water softeners many people use. These media are placed into above ground tanks and the PFAS-containing water is pumped through the tanks. There are advantages and disadvantages of each. Activated carbon systems require larger tanks than ion exchange. Ion exchange can also be more effective for the lower molecular weight PFAS. (Though for the most part, the lower molecular weight PFAS is not currently targeted for regulation.) Activated carbon has the added feature that it can also remove most organic contaminants and improve general water quality. The used media requires waste management and disposal.
Reverse osmosis or “RO” is also known to effectively remove PFASs, as well as a wide range of larger and smaller compounds, including important electrolytes that make drinking water palatable. RO systems are almost always expensive to purchase and operate, especially when the amount of water to be treated is large. Regardless, before designing and installing a PFAS treatment system, both laboratory and field experiments are almost always necessary. These so called “pilot studies” add time delays and costs to the implementation of any treatment program for PFAS.
“Limited application technologies” are those technologies that have a limited track record and have only been built and operated at a small number of sites, typically less than a “handful”. Flocculation/coagulation, which in a lower-tech form is used in many water treatment plants, shows promise as a commercial technology for ex-situ removal of high concentrations of PFAS, though a second step using either activated carbon or ion exchange remains necessary. Some limited case studies show that some of the more advanced forms of chemical oxidation can also be effective. This includes hydrogen peroxide and persulfate (persulfate is used in common consumer products, most notably hair coloring dyes.)
Technologies in the R&D phase mostly focus on the destruction of PFAS. Many researchers from academia and industry are working on developing PFAS destruction technologies. These technologies have technical complex names such as: advanced chemical reduction, electrochemical oxidation, electrochemical reduction, sonolysis, plasma, and bio-Fenton oxidation. Significant research progress has been made during the last several years. Most of the funding for this research comes from Congressional support to the DOD’s SERDP/ESTCP programs, from the National Institutes of Health (NIH) and from EPA. However, more research funding is important and needed to fully evaluate the effectiveness of these PFAS destruction technologies and to fund first-of-their kind field implementation programs that can establish cost-effectiveness.
Only through the incineration of waste activated carbon or ion exchange resin is destruction currently achieved, and then at only very high temperatures at very high costs. Without commercially available destructive techniques, PFAS contamination will simply be held in place in the ground under the long term environmental threat of re-release.
Field implementations (mostly of conventional separation technologies) are moving forward at federal facilities, but industrial and private facilities, including quite a number of water purveyors, are waiting for final resolution of water regulations nationwide. Once those regulations are promulgated, the demand for cost-effective treatment technologies will soar, including a need for more choices in effective technologies. Therefore, the need to develop new technology is urgent. Despite funding already occurring, even more funding is needed to meet the challenge!