Education

Research Description

Dr. Knappe has conducted research on water treatment processes for over 25 years. Current research efforts focus on (1) developing and evaluating physical-chemical treatment processes for the control of disinfection byproduct precursors and trace organic compounds (taste and odor causing substances, carcinogenic volatile organic contaminants, 1,4-dioxane, per- and polyfluoroalkyl substances, endocrine disrupting chemicals, antibiotics, and other pharmaceutically active compounds), and (2) overcoming gaps between the Clean Water Act and the Safe Drinking Water Act by developing information about the effects of reactive and unregulated wastewater contaminants on drinking water quality and treatment. Funding agencies that have supported or are currently supporting his research include the U.S. Environmental Protection Agency, the National Institute of Environmental Health Sciences, the National Science Foundation, the Water Research Foundation, the North Carolina Water Resources Research Institute, and the North Carolina Urban Water Consortium.

Publications

Assessing the Effectiveness of Point-of-Use Residential Drinking Water Filters for Perfluoroalkyl Substances (PFASs)

Herkert, N. J., Merrill, J., Peters, C., Bollinger, D., Zhang, S., Hoffman, K., … Stapleton, H. M. (2020), ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, 7(3), 178–184. https://doi.org/10.1021/acs.estlett.0c00004

Assessment of the breakthrough of micropollutants in full-scale granular activated carbon adsorbers by rapid small-scale column tests and a novel pilot-scale sampling approach

Merle, T., Knappe, D. R. U., Pronk, W., Vogler, B., Hollender, J., & Gunten, U. (2020), ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, 6(10), 2742–2751. https://doi.org/10.1039/d0ew00405g

Degradation Model for the Tensile Strength of PVC and Rubber Gasket Materials Exposed to Benzene and PCE-Saturated Aqueous Solutions

Hosseini, P., Alhomair, S., Faeli, Z., Pour-Ghaz, M., Gabr, M., Knappe, D., & Parker, C. (2020), TRANSPORTATION RESEARCH RECORD. https://doi.org/10.1177/0361198120906126

Elevated levels of per- and polyfluoroalkyl substances in Cape Fear River Striped Bass (Morone saxatilis) are associated with biomarkers of altered immune and liver function

Guillette, T. C., McCord, J., Guillette, M., Polera, M. E., Rachels, K. T., Morgeson, C., … Belcher, S. M. (2020), ENVIRONMENT INTERNATIONAL, 136. https://doi.org/10.1016/j.envint.2019.105358

Enabling Organic Micropollutant Removal from Water by Full-Scale Biochar and Activated Carbon Adsorbers Using Predictions from Bench-Scale Column Data

Kearns, J., Dickenson, E., & Knappe, D. (2020), ENVIRONMENTAL ENGINEERING SCIENCE. https://doi.org/10.1089/ees.2019.0471

GAC to BAC: Does it make chloraminated drinking water safer?

Cuthbertson, A. A., Kimura, S. Y., Liberatore, H. K., Knappe, D. R. U., Stanford, B., Summers, R. S., … Richardson, S. D. (2020), WATER RESEARCH, 172. https://doi.org/10.1016/j.watres.2019.115432

Measurement of Novel, Drinking Water-Associated PFAS in Blood from Adults and Children in Wilmington, North Carolina

Kotlarz, N., McCord, J., Collier, D., Lea, C. S., Strynar, M., Lindstrom, A. B., … Hoppin, J. A. (2020), ENVIRONMENTAL HEALTH PERSPECTIVES, 128(7). https://doi.org/10.1289/EHP6837

Pilot scale removal of per- and polyfluoroalkyl substances and precursors from AFFF-impacted groundwater by granular activated carbon

Rodowa, A. E., Knappe, D. R. U., Chiang, S.-Y. D., Pohlmann, D., Varley, C., Bodour, A., & Field, J. A. (2020), ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, 6(4), 1083–1094. https://doi.org/10.1039/c9ew00936a

Scientific Basis for Managing PFAS as a Chemical Class

Kwiatkowski, C. F., Andrews, D. Q., Birnbaum, L. S., Bruton, T. A., DeWitt, J. C., Knappe, D. R. U., … Blum, A. (2020), ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS, 7(8), 532–543. https://doi.org/10.1021/acs.estlett.0c00255

1,4-Dioxane in drinking water: emerging for 40 years and still unregulated

McElroy, A. C., Hyman, M. R., & Knappe, D. R. U. (2019), Current Opinion in Environmental Science & Health, 7, 117–125. https://doi.org/10.1016/j.coesh.2019.01.003

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Grants

Occurrence and Fate of Per- and Polyfluoroalkyl Substances (PFAS) in North Carolina Agricultural Systems

NC Department of Justice (NCDOJ)(1/01/21 - 12/31/23)

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Occurrence and Fate of Per- and Polyfluoroalkyl Substances (PFAS) in North Carolina Agricultural Systems

Sponsor: NC Department of Justice (NCDOJ)

Start Date: 1/01/21

End Date: 12/31/23

Abstract

The overall goal of this project is to identify the frequency of PFAS occurrence within swine sludge and biosolids to understand the risk of PFAS movement when these byproducts are applied to agricultural fields in the Cape Fear Watershed and other areas.

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Development of a Perfluoroalkyl Substances (PFAS) Systems Analysis Tool (SAT) to Assist in Prioritization of Destruction Research and Management Decisions

US Environmental Protection Agency (EPA)(6/11/20 - 9/30/20)

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Development of a Perfluoroalkyl Substances (PFAS) Systems Analysis Tool (SAT) to Assist in Prioritization of Destruction Research and Management Decisions

Sponsor: US Environmental Protection Agency (EPA)

Start Date: 6/11/20

End Date: 9/30/20

Abstract

The objective of this project is to develop a comprehensive systems analysis tool (SAT) to estimate PFAS release associated with management alternatives for a wide range of PFAS-containing wastes. Through this project, we will establish an analytical framework to rigorously describe alternatives for the management of individual PFAS-containing wastes, estimate PFAS release and the receiving medium (air, surface water, groundwater, land).

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Thermal Reactivation of Spent GAC from PFAS Remediation Sites

Strategic Environmental Research and Development Program (SERDP)(12/16/20 - 2/28/21)

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Thermal Reactivation of Spent GAC from PFAS Remediation Sites

Sponsor: Strategic Environmental Research and Development Program (SERDP)

Start Date: 12/16/20

End Date: 2/28/21

Abstract

The overarching goal of this research is to determine the fate of per- and polyfluoroalkyl substances (PFASs) during thermal reactivation of granular activated carbon (GAC) that had treated PFAS-laden water. Bench-scale studies will be conducted to determine reactivation conditions that release PFAS from spent GAC and lead to PFAS mineralization. To close the fluorine mass balance, this study will focus on laboratory-loaded GAC with known PFAS loadings. Limited experiments will be conducted with spent GAC from remediation sites with high PFAS levels.

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

NC Department of Transportation(8/01/19 - 7/31/21)

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Field Evaluation of Hardening Methods for Subsurface Utilities and Drainage Pipes

Sponsor: NC Department of Transportation

Start Date: 8/01/19

End Date: 7/31/21

Abstract

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Based on the field evaluations carried out by NCDOT, at times subsurface utilities including water and/or drainage pipes are present, or need to be installed, in environments where soil and groundwater contamination exists. The currently funded project (RP 2017-08 with end date on July 31, 2019), is focused on the laboratory evaluation of contaminant migration through concrete pipes, as well as evaluation of the effect of contaminants on the mechanical performance of PVC pipe and three gasket materials (Neoprene, Buna-N, and Viton) when exposed to contaminated water. In addition, modeling of hardening methods and evaluating their efficacy is conducted as a part of the ongoing project.

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Center for Environmental and Health Effects of PFAS

National Institutes of Health (NIH)(2/28/20 - 1/31/21)

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Center for Environmental and Health Effects of PFAS

Sponsor: National Institutes of Health (NIH)

Start Date: 2/28/20

End Date: 1/31/21

Abstract

Per- and polyfluoroalkyl substances (PFAS) are emerging as a major public health problem in North Carolina and across the United States. PFAS comprise a class of over 5,000 compounds. Their unique chemical properties have been harnessed to make consumer and industrial products more water, stain, and grease resistant; they are found in products as diverse as cosmetics and flame-retardants. PFAS are resistant to degradation, move easily through the environment, and accumulate in living organisms. Exposure to PFAS has been associated with health effects including cancer and toxicity to the liver, reproductive development, and thyroid and immune systems. Despite widespread detection in the environment and evidence of increasing human exposure, understanding about PFAS toxicity, its bioaccumulative potential in dietary sources such as aquatic organisms, and effective remediation remain notably understudied. The recent discovery by this proposed Center’s Deputy Director, Dr. Detlef Knappe, of widespread PFAS contamination in the Cape Fear River watershed in NC underscores that these compounds are in need of immediate investigation.. The goal of our Center is to advance understanding about the environmental and health impacts of PFAS. To meet this goal we are employing a highly trans-disciplinary approach that will integrate leaders in diverse fields (epidemiology, environmental science and engineering, biology, toxicology, immunology, data science, and advanced analytics); all levels of biological organization (biomolecule, pathway, cell, tissue, organ, model organism, human, and human population); state-of-the-art analytical technologies; cutting-edge data science approaches; a recognized track record in interdisciplinary, environmental health science (EHS) training; and well-established partnerships with government and community stakeholders.

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An Electroactive Point-of-Use Filter for Per- and Polyfluoroalkyl Contaminant Removal

US Environmental Protection Agency (EPA)(10/01/19 - 8/15/21)

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An Electroactive Point-of-Use Filter for Per- and Polyfluoroalkyl Contaminant Removal

Sponsor: US Environmental Protection Agency (EPA)

Start Date: 10/01/19

End Date: 8/15/21

Abstract

Emerging contaminants are widely present in raw and treated drinking water and present an ongoing threat to human health, prosperity, and the planet. Per- and polyfluoroalkyl substances (PFAS), a broad class of fluorinated chemicals compounds used in a variety of industrial products, such as food packages, and household products, have been detected in drinking water across the country, including locally in Wilmington, North Carolina. Many PFAS are known or suspected carcinogens and pose a risk to humans even at trace levels (ng/L to ug/L). Moreover, they present a risk to the planet because they poorly degrade in the environment. The profound health risk of PFAS has therefore created an urgent need to develop viable methods and technologies to remove PFAS from water resources. The proposed technology in this project directly addresses the three aspects of sustainability because it will result in a cost- and energy-efficient PFAS removal method that can be readily adopted in households across the US. Furthermore, this project will provide an excellent opportunity for educating the public, especially school students in the regional community, many of which have been exposed to PFAS-contaminated waters. To broaden our dissemination of our project and the concepts of sustainability, we will attend and present our results in regional science fairs, such as at the NC Science Festival.

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Investigation of Treatment Alternatives for Short-Chain Poly- and Perfluoroalkyl Substances

Water Research Foundation(3/01/19 - 3/01/22)

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Investigation of Treatment Alternatives for Short-Chain Poly- and Perfluoroalkyl Substances

Sponsor: Water Research Foundation

Start Date: 3/01/19

End Date: 3/01/22

Abstract

Poly- and perfluoroalkyl substances (PFASs) are contaminants of emerging concern for drinking water providers nationwide. As concerns about adverse health impacts have risen for long-chain PFASs, fluorochemical manufacturers have shifted their production to short-chain PFASs. As a result the detection frequency of short-chain PFASs in drinking water sources is increasing. The overarching objective of this research is to develop effective water treatment approaches for the control of short-chain PFASs. Treatment technologies, such as activated carbon adsorption, anion exchange, and high-pressure membrane filtration will be evaluated in both surface and ground water treatment contexts. In addition, innovative sorbents and destructive processes will be explored. Data generated in this study will inform life cycle analysis and cost models and will provide guidance for drinking water providers impacted by short-chain PFASs.

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PFAS UNITEDD: U.S. National Investigation of Transport & Exposure from Drinking Water & Diet

US Environmental Protection Agency (EPA)(5/01/19 - 4/30/22)

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PFAS UNITEDD: U.S. National Investigation of Transport & Exposure from Drinking Water & Diet

Sponsor: US Environmental Protection Agency (EPA)

Start Date: 5/01/19

End Date: 4/30/22

Abstract

Per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants of global concern. Over 3,000 PFASs are on the global market, but for most PFASs we lack information about their properties, environmental fate and transport, bioaccumulation in foods of plant and animal origin, and human exposure. The overarching objective of the proposed research is to develop actionable information on the fate, transport, bioaccumulation, and relative exposures of understudied PFASs in PFAS-impacted communities. Information developed in this research is expected to enable risk managers to make informed decisions and reduce uncertainties related to human PFAS exposures.

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Impacts of GenX (2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate) on reproductive function and transcriptome signature in Caenorhabditis elegans

NCSU Center for Human Health and the Environment(6/01/18 - 3/31/20)

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Impacts of GenX (2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate) on reproductive function and transcriptome signature in Caenorhabditis elegans

Sponsor: NCSU Center for Human Health and the Environment

Start Date: 6/01/18

End Date: 3/31/20

Abstract

Perfluoroalkyl substances (PFASs) are a diverse group of synthetic chemicals used in a wide variety of industrial processes and consumer products. The short-chain PFAS GenX (2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate) has been detected in drinking water from NC’s Cape Fear River downstream of a facility that generates GenX at an average concentration four times higher than the estimated safe level. Currently, little or nothing is known about the potential health effects of exposure to GenX. The overarching goal of this pilot project is to address this gap employing the nematode Caenorhabditis elegans (C. elegans) to identify toxic effects in reproduction upon exposure to this compound. We hypothesize that exposure of C. elegans to environmentally relevant concentrations of GenX will result in impaired reproductive function and alterations in transcriptome profile. To test this hypothesis the following two specific aims will be conducted 1) Characterize effects of exposure to a range of environmentally relevant concentrations of GenX on reproductive function including brood size, egg hatching rate, gonadal development, permatogenesis and oogenesis. and 2) Evaluate effects of GenX exposure on gene expressions by transcriptome profiling and qRT-PCR confirmation. Based on aim 1) one GenX treated group will be selected for transcriptome profiling and compared with control. This study will identify potential health effects of exposure to GenX that will guide future analysis of mixtures, guide validation studies in vertebrate animals and inform translation into exposed human cohorts.

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Collaborative Research: Cyclodextrin-Based 2D Materials for the Treatment of Legacy and Emerging Perfluoroalkyl Substances

National Science Foundation (NSF)(8/15/18 - 7/31/21)

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Collaborative Research: Cyclodextrin-Based 2D Materials for the Treatment of Legacy and Emerging Perfluoroalkyl Substances

Sponsor: National Science Foundation (NSF)

Start Date: 8/15/18

End Date: 7/31/21

Abstract

Development of water purification media for perfluoroalkyl contaminants via cyclodextrin grafted graphene oxide.

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