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 Science Foundation, the Water Research Foundation, the North Carolina Water Resources Research Institute, and the North Carolina Urban Water Consortium.

Publications

Prediction of full-scale GAC adsorption of organic micropollutants

Kennedy, A. M., Reinert, A. M., Knappe, D. R. U., & Summers, R. S. (2017), Environmental Engineering Science, 34(7), 496–507. https://doi.org/10.1089/ees.2016.0525

Determination of 1,4-dioxane in the Cape Fear River watershed by heated purge-and-trap preconcentration and gas chromatography-mass spectrometry

Sun, M., Lopez-Velandia, C., & Knappe, D. R. U. (2016), Environmental Science & Technology, 50(5), 2246–2254. https://doi.org/10.1021/acs.est.5b05875

Environmental comparison of biochar and activated carbon for tertiary wastewater treatment

Thompson, K. A., Shimabuku, K. K., Kearns, J. P., Knappe, D. R. U., Summers, R. S., & Cook, S. M. (2016), Environmental Science & Technology, 50(20), 11253–11262. https://doi.org/10.1021/acs.est.6b03239

Legacy and emerging perfluoroalkyl substances are important drinking water contaminants in the Cape Fear River watershed of North Carolina

Sun, M., Arevalo, E., Strynar, M., Lindstrom, A., Richardson, M., Kearns, B., … Knappe, D. R. U. (2016), Environmental Science & Technology Letters, 3(12), 415–419. https://doi.org/10.1021/acs.estlett.6b00398

Feasibility of using traditional kiln charcoals in low-cost water treatment: Role of pyrolysis conditions on 2,4-d herbicide adsorption

Kearns, J. P., Knappe, D. R. U., & Summers, R. S. (2015), Environmental Engineering Science, 32(11), 912–921. https://doi.org/10.1089/ees.2015.0243

Full- and pilot-scale GAC adsorption of organic micropollutants

Kennedy, A. M., Reinert, A. M., Knappe, D. R. U., Ferrer, I., & Summers, R. S. (2015), Water Research, 68, 238–248. https://doi.org/10.1016/j.watres.2014.10.010

Meeting multiple water quality objectives through treatment using locally generated char: Improving organoleptic properties and removing synthetic organic contaminants and disinfection by-products

Kearns, J. P., Shimabuku, K. K., Mahoney, R. B., Knappe, D. R. U., & Summers, R. S. (2015), Journal of Water Sanitation and Hygiene for Development, 5(3), 359–372. https://doi.org/10.2166/washdev.2015.172

2,4-D adsorption to biochars: Effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data

Kearns, J. P., Wellborn, L. S., Summers, R. S., & Knappe, D. R. U. (2014), Water Research, 62, 20–28. https://doi.org/10.1016/j.watres.2014.05.023

Fertilization of radishes, tomatoes, and marigolds using a large-volume atmospheric glow discharge

Lindsay, A., Byrns, B., King, W., Andhvarapou, A., Fields, J., Knappe, D., … Shannon, S. (2014), Plasma Chemistry and Plasma Processing, 34(6), 1271–1290. https://doi.org/10.1007/s11090-014-9573-x

Synthetic organic water contaminants in developing communities: An overlooked challenge addressed by adsorption with locally generated char

Kearns, J. P., Knappe, D. R. U., & Summers, R. S. (2014), Journal of Water Sanitation and Hygiene for Development, 4(3), 422–436. https://doi.org/10.2166/washdev.2014.073

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Grants

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(8/01/18 - 5/31/19)

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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: 8/01/18

End Date: 5/31/19

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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Occurrence of Pesticides in North Carolina Private Drinking Water Wells and Identification of Point-of-Use Treatment Options

NCSU Water Resources Research Institute(3/01/18 - 6/17/19)

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Occurrence of Pesticides in North Carolina Private Drinking Water Wells and Identification of Point-of-Use Treatment Options

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/18

End Date: 6/17/19

Abstract

Approximately 3.3 million North Carolinians (35% of the population) rely on private wells as their primary source of drinking water.1 Well water quality is not regulated at the state or federal level, despite several studies illustrating a link between well water contamination and adverse health outcomes.2,3 Moreover, well water can contain harmful organic contaminants such as pesticides, but occurrence data are sparse.4 Key goals of the proposed research are to characterize pesticide contamination in private well water across the state and develop information for the selection of effective home treatment devices.

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Assessing impact of drinking water exposure to GenX (hexafluoropropylene oxide dimer acid) in the Cape Fear River Basin, North Carolina

National Institutes of Health (NIH)(11/01/17 - 10/31/19)

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Assessing impact of drinking water exposure to GenX (hexafluoropropylene oxide dimer acid) in the Cape Fear River Basin, North Carolina

Sponsor: National Institutes of Health (NIH)

Start Date: 11/01/17

End Date: 10/31/19

Abstract

GenX is a perflourinated compound used and generated in the production of non-stick coatings. This chemical has been detected in the Cape Fear River in North Carolina, upstream of where the Cape Fear Public Utility Authority obtains drinking water for the City of Wilmington (population ~250,000), Brunswick County and Pender County, NC. In June 2017, community concern about this chemical in drinking water resulted in multiple public meetings of citizens trying to obtain information about their potential exposure and resulting health effects associated with consumption of drinking water. As a result of community concern, the chemical plant has reportedly stopped discharging GenX into the river. However community concern still exists. This project is designed to help address community concerns about GenX exposure and health effects. Little is known about how GenX is stored in the body, the toxicity of GenX, or how long the chemical will remain in the environment. To address these questions, we plan to conduct a community-based study of Wilmington area residents who are served by public utility water. We will work with community partners of the Cape Fear Riverkeeper and the New Hanover County Department of Health to help identify a representative sample of residents, to collect biological samples, and to keep the community informed about what is known about GenX and what the study finds. We plan to recruit ~400 Wilmington area residents (100 men, 100 women, 100 boys, 100 girls) to provide blood, urine, and drinking water samples and to complete a questionnaire on their water use history. We plan to analyze blood, urine, and drinking water for GenX and related perflourinated chemicals; blood and urine samples will also be used for clinical tests (lipid profile, thyroid function, liver function, and urinalysis). All results from the study will be shared with both the community as a whole and each individual participant. We will have a community advisory panel for the study to help advise about study protocols, methods of reporting back results to participants, and provide guidance on ongoing or new community concerns about GenX. This project leverages the expertise of NC State’s Center for Human Health and the Environment to respond to an emerging community concern.

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Collaborative Research: EAGER: Tailored sorbents for the removal of emerging per- and polyfluorinated alkyl substances from water

National Science Foundation (NSF)(9/15/17 - 2/28/19)

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Collaborative Research: EAGER: Tailored sorbents for the removal of emerging per- and polyfluorinated alkyl substances from water

Sponsor: National Science Foundation (NSF)

Start Date: 9/15/17

End Date: 2/28/19

Abstract

Per- and polyfluoroalkyl substances (PFASs) are contaminants of emerging concern because of their toxicological properties, widespread presence, and persistence in the environment. Most water treatment technologies are not effective for PFAS control. For example, we have shown that short-chain PFASs and perfluoroalkyl ether carboxylic acids (PFECAs) were not removed in a drinking water treatment plant equipped with advanced treatment processes. Also, activated carbon adsorption is ineffective for the removal of short-chain PFASs and PFECAs. In the research proposed here, we seek to design cyclodextrins that can strongly bind short-chain PFASs, including PFECAs. We propose to explore the newly modified cyclodextrins by developing PFAS-selective sorbents for drinking water and industrial wastewater treatment.

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Cometabolic Degradation of 1,4-Dioxane in Biologically Active Carbon Filters with Locally Enriched Biota

NCSU Water Resources Research Institute(3/01/18 - 2/28/19)

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Cometabolic Degradation of 1,4-Dioxane in Biologically Active Carbon Filters with Locally Enriched Biota

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/18

End Date: 2/28/19

Abstract

1,4-Dioxane is classified as a likely human carcinogen, and an increased one in one million cancer risk is associated with a lifetime consumption of drinking water containing a 1,4-dioxane concentration of 0.35 μg/L. Data from the US Environmental Protection Agency show that 7 of the 20 highest concentrations of 1,4-dioxane in US drinking water (up to 13.3 μg/L) occur in the Cape Fear River watershed. In all 7 instances, the Cape Fear River served as the source of the treated drinking water. The overall goal of this research is to develop a biological treatment process to degrade 1,4-dioxane from drinking water relevant concentrations. Microcosm and biofiltration column experiments will be conducted with enrichment cultures derived from aquatic environments in North Carolina. The effects of biofilm attachment media (sand, granular activated carbon, carbonaceous resin) on 1,4-dioxane degradation rates and the production of degradation products will be assessed. Research products will include the cultures and knowledge necessary to develop biologically active filters to treat 14-dioxane at drinking water relevant concentrations. An effective biofiltration system would not only enhance the safety of drinking water but would also ensure that surface water-derived contaminants, such as 1,4-dioxane, are not introduced into groundwater at utilities practicing aquifer storage and recovery.

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Design and Application of Cyclodextrin-Based Materials for the Treatment of Legacy and Emerging Perfluoroalkyl Acids

NCSU Water Resources Research Institute(3/01/18 - 2/28/19)

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Design and Application of Cyclodextrin-Based Materials for the Treatment of Legacy and Emerging Perfluoroalkyl Acids

Sponsor: NCSU Water Resources Research Institute

Start Date: 3/01/18

End Date: 2/28/19

Abstract

Per- and polyfluoroalkyl substances (PFASs) are important drinking water and groundwater contaminants. Recent estimates show that approximately six million US citizens are receiving drinking water with PFAS concentrations that exceed the health advisory level issued by the US Environmental Protection Agency. Because of the toxicological properties, stability, and widespread presence of legacy PFASs in the environment, fluorochemical manufacturers have switched to short-chain PFASs and fluorinated alternatives such as perfluoroalkyl ether carboxylic acids (PFECAs). Standard treatment methods, including activated carbon adsorption and oxidative treatments, are ineffective for the treatment of short-chain PFASs and PFECAs. The overarching goal of this proposal is to employ cyclodextrins for the treatment of both legacy and emerging PFASs.

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Strategic Environmental Research and Development Program (SERDP)(5/16/18 - 5/16/19)

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Electrically Assisted Sorption and Desorption of Per- and Polyfluoroalkyl Substances

Sponsor: Strategic Environmental Research and Development Program (SERDP)

Start Date: 5/16/18

End Date: 5/16/19

Abstract

The removal of per- and polyfluoroalkly substances (PFASs) from contaminated groundwater is required to minimize human exposure to these compounds. Activated carbon is a widely used sorbent to remove PFASs, but it suffers from two limitations: 1) the inability to remove short-chain PFASs, and 2) the lack of cost-effective regeneration methods. The overall objective of this proposal is to electrically enhance adsorption of high priority PFASs onto activated carbon and electrically discharge them as an innovative, chemical-free regeneration technique.

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Development of Appropriate Technologies to Treat Drinking Water Co-Contaminants Associated with Chronic Kidney Disease of Unknown Origin (CKDu)

NCSU Research and Innovation Seed Funding Program(1/01/17 - 12/31/17)

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Development of Appropriate Technologies to Treat Drinking Water Co-Contaminants Associated with Chronic Kidney Disease of Unknown Origin (CKDu)

Sponsor: NCSU Research and Innovation Seed Funding Program

Start Date: 1/01/17

End Date: 12/31/17

Abstract

Recent research has suggested that co-contamination of drinking water with fluoride (F), cadmium (Cd), and arsenic (As) may play a causative role in chronic kidney disease of unknown etiology (CKDu)The motivating factor of our research is to develop appropriate, low-cost treatment methods for water co-contaminated with F, Cd, and As. Our work will integrate the expertise and perspectives of researchers from NCSU’s College of Agriculture and Life Sciences (CALS), College of Engineering (COE), Center for Human Health and the Environment (CHHE) in the College of Sciences (COS), and from RTI International (RTI). The specific objective of this RISF research is to quantify the reaction kinetics and uptake mechanisms of F, Cd, and As for two low-cost water water-treatment methods, bone char sorption and contact precipitation. Treatment for these three ions is challenging, due to differing charges, surface interactions and speciation under different conditions. In the sorption method, animal bones are burned at high temperatures and brought into contact with contaminated water. Hydroxyapatite, the main component of bone, removes ions from solution through sorption to mineral surfaces and ion exchange. The contact precipitation method consists of adding calcium and phosphate solutions to contaminated water to promote precipitation of contaminants in flurapatite and calcium fluoride along existing mineral (e.g. bone char) surfaces.

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

NC Department of Transportation(8/01/16 - 7/31/19)

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The effects of contaminated soil and groundwater on subsurface utilities, surface water and drainage

Sponsor: NC Department of Transportation

Start Date: 8/01/16

End Date: 7/31/19

Abstract

The North Carolina Department of Transportation (NCDOT) routinely performs road improvement projects where a portion of the right-of-way might be contaminated. Potential sources of contamination include underground storage tanks in the vicinity of the road improvement site, old unlined landfills, or abandoned industrial and agricultural operations with practices leading to soil and/or groundwater contamination. It has been reported by NCDOT in RNS#7406 that in several situations, subsurface utilities including drainage pipes are present in environments where soil and groundwater contamination exists. The effect of the contamination on the integrity and durability of the subsurface drainage pipes and gaskets is largely unknown but such integrity is a function of the type of contamination and the physicochemical properties of pipe, gasket, and other materials forming a given subsurface utility. In addition to the variety of contaminants and concentrations that prevail at these sites, a wide variation in soil geological formation and hydrogeological conditions exist across the state. While in general the groundwater table is expected to be high in the North Carolina (NC) Coastal Plain Physicographic region, it is expected to be deep in the Mountains. On the other hand, it is more likely that groundwater will feed surface water springs and streams in the NC Mountains. Therefore, a "typical" contaminated site is difficult to define. Accordingly, the adverse effect of subsurface contamination on drainage pipes and the efficacy of hardening measures are usually developed on a site-specific basis. Objectives of this project are to (i) catalog the prevalent types of contaminants and their concentrations at sites where subsurface utilities are installed, (ii) document the typical materials used in subsurface utilities and drainage systems in NC, (iii) quantify the effect of contaminants on the long-term durability of commonly used hardened and unhardened materials that are used in construction of subsurface utilities, (iv) quantify the rate and extent of migration of common contaminants through concrete utilities, (v) recommend effective hardening methods for different materials, and (vi) provide documentation and better understanding of the effect of subsurface utility installation on the contamination of groundwater and surface water through simulation of several typical scenarios. These objectives will be achieved through a multidisciplinary effort of the research team as outlined in the project plan. Objective (i) will be achieved through examination of available data from the NC Department of Environmental Quality (DEQ). If necessary, limited sampling of groundwater and surface water will be conducted in consultation with NCDOT in areas where subsurface utilities have been installed and contamination is known to exist or expected to occur. Objectives (ii), (iii), and (iv) will be accomplished through literature review and accelerated coupon testing in our laboratory. Objective (v) will be achieved by analyzing test results and literature data. Objective (vi) will be accomplished through numerical simulations.

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