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

Improved Darcian streambed measurements to quantify flux and mass discharge of volatile organic compounds from a contaminated aquifer to an urban stream

Nickels, J. L., Genereux, D. P., & Knappe, D. R. U. (2023), JOURNAL OF CONTAMINANT HYDROLOGY, 253. https://doi.org/10.1016/j.jconhyd.2022.104124

Pilot-scale biofiltration of 1,4-dioxane at drinking water-relevant concentrations

McElroy, A. C., Ogles, M. E., Hyman, M. R., & Knappe, D. R. U. (2023), WATER RESEARCH, 231. https://doi.org/10.1016/j.watres.2023.119652

Removal and destruction of perfluoroalkyl ether carboxylic acids (PFECAs) in an anion exchange resin and electrochemical oxidation treatment train

Fang, Y., Meng, P., Schaefer, C., & Knappe, D. R. U. (2023), WATER RESEARCH, 230. https://doi.org/10.1016/j.watres.2022.119522

Source apportionment of serum PFASs in two highly exposed communities

Wallis, D. J., Barton, K. E., Knappe, D. R. U., Kotlarz, N., McDonough, C. A., Higgins, C. P., … Adgate, J. L. (2023), SCIENCE OF THE TOTAL ENVIRONMENT, 855. https://doi.org/10.1016/j.scitotenv.2022.158842

Diffusion of benzene and tetrachloroethylene through saturated cement paste

Hosseini, P., McElroy, A., Knappe, D. R. U., Gabr, M., & Pour-Ghaz, M. (2022), CONSTRUCTION AND BUILDING MATERIALS, 329. https://doi.org/10.1016/j.conbuildmat.2022.127196

Drinking Water-Associated PFAS and Fluoroethers and Lipid Outcomes in the GenX Exposure Study

Rosen, E. M., Kotlarz, N., Knappe, D. R. U., Lea, C. S., Collier, D. N., Richardson, D. B., & Hoppin, J. A. (2022), ENVIRONMENTAL HEALTH PERSPECTIVES, 130(9). https://doi.org/10.1289/EHP11033

Extraction and Matrix Cleanup Method for Analyzing Novel Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances in Fruits and Vegetables

Meng, P., DeStefano, N. J., & Knappe, D. R. U. (2022), JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, 70(16), 4792–4804. https://doi.org/10.1021/acs.jafc.1c07665

Impact of ozone-biologically active filtration on the breakthrough of Perfluoroalkyl acids during granular activated carbon treatment of municipal wastewater effluent

Vatankhah, H., Tajdini, B., Milstead, R. P., Clevenger, E., Murray, C., Knappe, D., … Bellona, C. (2022), WATER RESEARCH, 223. https://doi.org/10.1016/j.watres.2022.118988

Mechanisms of orthophosphate removal from water by lanthanum carbonate and other lanthanum-containing materials

Zhi, Y., Paterson, A. R., Call, D. F., Jones, J. L., Hesterberg, D., Duckworth, O. W., … Knappe, D. R. U. (2022), SCIENCE OF THE TOTAL ENVIRONMENT, 820. https://doi.org/10.1016/j.scitotenv.2022.153153

PFAS Challenges and Novel Research A Conversation With the Editorial Board of the AWWA Water Science Topical Collection on PFAS Analytics and Treatment

Crimi, M., Speth, T. F., Chowdhury, Z. K., Dickenson, E. R. V., Knappe, D. R. U., & Liu, J. (2022, September), JOURNAL AWWA, Vol. 114, pp. 13–22. https://doi.org/10.1002/awwa.1956

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Grants

Studying the Fate of PFAS through Sewage Sludge Incinerators

Hampton Roads Sanitation District (HRSD)(3/28/22 - 6/30/23)

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Studying the Fate of PFAS through Sewage Sludge Incinerators

Sponsor: Hampton Roads Sanitation District (HRSD)

Start Date: 3/28/22

End Date: 6/30/23

Abstract

Incineration can destroy per- and polyfluoroalkyl substances (PFAS), but the conditions required for destruction are not known. This research aims to elucidate the fate of these compounds through sewage sludge incinerators (SSIs), and thereby provide utilities and decision makers with an indication regarding the extent SSIs can reduce PFAS discharges to the environment which is important for informing PFAS handling strategies.

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TSA: Testing PFAS Removal in Pilot-Scale Granular Activated Carbon Columns and Bench-Scale Ion Exchange Columns

Hazen and Sawyer(8/01/21 - 7/31/22)

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TSA: Testing PFAS Removal in Pilot-Scale Granular Activated Carbon Columns and Bench-Scale Ion Exchange Columns

Sponsor: Hazen and Sawyer

Start Date: 8/01/21

End Date: 7/31/22

Abstract

TSA "Water Quality Testing Using Rapid Small-Scale column tests for PFAS Removal by ION Exchange Resins"

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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)(3/22/21 - 3/31/22)

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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: 3/22/21

End Date: 3/31/22

Abstract

The overall objective of this project is to develop and exercise a comprehensive systems analysis tool (SAT) to estimate PFAS release associated with management alternatives for a wide range of PFAS-containing wastes. In September 2020, we submitted the alpha version of the SAT as well as associated documentation. While this tool facilitates the comparison of alternative management strategies for PFAS-containing waste materials, it is not yet ready to be publicly released. The most critical next steps to advance the functionality and applicability of the tool consist of 1) reviewing and updating model input data, 2) developing PFAS-waste management scenarios and exercising the model to analyze predictions, and 3) upgrading the usability and functionality of the graphical user interface (GUI).

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

NC Department of Justice (NCDOJ)(1/01/21 - 12/31/24)

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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: 12/31/24

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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Assessment of Pesticide Stability in Water and Analysis of Pesticide Degradates in Private Wells in North Carolina

NCSU Water Resources Research Institute(3/01/21 - 8/31/22)

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Assessment of Pesticide Stability in Water and Analysis of Pesticide Degradates in Private Wells in North Carolina

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/21

End Date: 8/31/22

Abstract

Approximately 30% of North Carolinians rely on private wells as their primary source of drinking water. Because private wells fall outside of the purview of the Safe Drinking Water Act, occurrence data are lacking for compounds such as pesticides. Furthermore, currently available analytical methods for pesticides target only a limited number of pesticides and do not keep up with the ever-evolving list of pesticides in use. Additionally, many pesticides partially degrade in the environment (e.g. via hydrolysis) and evidence of pesticide impact requires analysis for degradates in such cases. In order to more fully understand the impact that pesticides have on private well water quality, it is vital that we understand current use patterns for pesticides and the stability of these pesticides in water. To address this information gap, the proposed project aims to 1) assess the stability of the ten most widely used pesticides in NC and identify possible hydrolysis products and 2) investigate the occurrence of these pesticides and their degradates in NC private wells known to contain pesticides.

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Novel Mass Spectrometry Approaches for the Identification of Pesticides and Per- and Poly-Fluoroalkyl Substances in North Carolina Drinking Water Sources

NCSU Water Resources Research Institute(3/01/21 - 2/28/23)

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Novel Mass Spectrometry Approaches for the Identification of Pesticides and Per- and Poly-Fluoroalkyl Substances in North Carolina Drinking Water Sources

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/21

End Date: 2/28/23

Abstract

North Carolina drinking water sources are vulnerable to impacts from a unique set of emerging organic contaminants, including per- and poly-fluoroalkyl substances (PFAS), pesticides, and pesticide degradates. The impact of these contaminants on the private well community in NC remains understudied. In this proposal, we will use the combination of ion mobility spectrometry (IMS) and mass spectrometry (MS) to extend a multidimensional database of toxicants, create a rapid analytical method suitable for organic contaminants, and apply this method to up to 50 private wells in NC.

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Highly Fluorinated Compounds – Social and Scientific Discovery: 3rd Annual Meeting

National Institutes of Health (NIH)(9/02/21 - 8/31/22)

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Highly Fluorinated Compounds – Social and Scientific Discovery: 3rd Annual Meeting

Sponsor: National Institutes of Health (NIH)

Start Date: 9/02/21

End Date: 8/31/22

Abstract

This three-day conference on “Highly Fluorinated Compounds – Social and Scientific Discovery” will examine the complex set of social, scientific, political, and environmental health issues raised by the recent discoveries of water contamination with high levels of highly fluorinated compounds. By bringing together scientists, government officials, activists, lay people, journalists, and lawyers, the conference can build on the diverse experiences and perspectives in order to better understand issues of science, regulation, remediation, prevention, and community engagement.

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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 - 12/16/23)

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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: 12/16/23

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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Occurrence of PFAS in US Wastewater Treatment Plants

Water Research Foundation(3/26/20 - 7/01/22)

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Occurrence of PFAS in US Wastewater Treatment Plants

Sponsor: Water Research Foundation

Start Date: 3/26/20

End Date: 7/01/22

Abstract

The overall goal of this project is to develop a comprehensive, methodologically consistent dataset regarding PFAS occurrence, fate, and mass distribution in wastewater treatment plants (WWTPs). This dataset will provide the scientific justification to develop appropriate guidance for site managers that benchmarks typical PFAS mass flows from WWTPs, sampling procedures and analytical methods, as well as potential mitigation strategies specific to WWTP unit processes. Specific objectives include: i) assessing the occurrence of a wide range of PFAS (32 target analytes and 325 precursors) and their fate in solid and liquid streams, ii) applying statistical tools to identify potential geographical or seasonal variables that impact WWTP susceptibility to PFAS, iii) determining the impacts of various treatment processes, including advanced treatment processes, on PFAS fate and partitioning, particularly PFAA precursor transformation, and iv) identifying key elements or data gaps in PFAS occurrence and fate in WWTPs to develop guidelines and mitigation/management strategies for PFAS.

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