Research Reports

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  • Novel Mass Spectrometry Approaches for the Identification of Pesticides and Per- and Polyfluoroalkyl Substances in North Carolina Drinking Water Sources
    (NC WRRI, 2024-01-18) Knappe, Detlef; Baker, Erin
    Water quality can be adversely impacted by a wide range of organic contaminants, including pesticides and per- and polyfluoroalkyl substances (PFAS). To support the assessment of water quality by liquid chromatography, ion mobility spectrometry, and tandem mass spectrometry, a database of collision cross sections was developed for pesticides. The database can be used in both targeted and nontargeted analyses of aqueous samples. Within the database, a clear separation occurs between pesticides and highly halogenated exposomic compounds, such as per- and polyfluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), which will be useful in nontargeted workflows as unknown features can be tentatively assigned to specific exposomic classes without a true identification. The utility of these methods for the assessment of water quality and human exposure was explored. Using the database, atrazine was identified in 3 out of 13 surface water samples (11-40 ng/L). To assess the potential impact of land-applied biosolids on aqueous PFAS concentrations, 13 surface water sites and 9 private wells were sampled near fields that had received biosolids. Eight of the surface water sites contained detectable PFAS at concentrations up to 1,880 ng/L, and eight of the private wells contained detectable PFAS at concentrations up to 194 ng/L. The primary subclasses identified in the samples were perfluoroalkyl sulfonic acids and perfluoroalkyl carboxylic acids.
  • Developing a Watershed Prioritization Index to Guide Restoration Initiatives in the Upper Little Tennessee River Basin
    (NC WRRI, 2024-03-28) Gibbs, W. Keith; Styers, Diane M.; Martin, Thomas H.
    Our research objectives were to: 1) analyze geospatial data across the Upper Little Tennessee River Basin (ULTRB) to 2) rank subwatersheds for risks to water quality at multiple spatial scales and 3) link land cover change over time to water quality and aquatic biota. We extracted land cover and landscape feature data at multiple spatial scales to categorize attributes and rank subwatersheds from least to most susceptible to impairment. Water quality and aquatic habitat were sampled in a subset of subwatersheds to verify and validate geospatially derived prioritization rankings. Historical fish and macroinvertebrate assemblage data were compiled and georeferenced to identify gaps in knowledge and target supplemental sampling efforts. Although the ULTRB is predominantly forested (>87%), ~8.5% is developed and ~2.5% is agricultural. Some subwatersheds exceeded 78% developed land use and others exceeded 34% agricultural land use within a 30m riparian zone. Altered land uses (i.e., agriculture and development) were negatively correlated to steep slopes and concentrated in areas of gentler slopes found in riparian zones. Soil erodibility was not strongly correlated to land use or slope steepness. Agricultural land uses had the strongest negative correlation to larger substrate sizes and stream reaches with more agriculture had higher percentages of finer substrates (i.e., sand and silt). Development was also positively correlated to the percentage of silt within stream reaches. Visual habitat assessments were negatively correlated to percentage of agriculture and development. Macroinvertebrate indices of biotic integrity scores were also negatively correlated with agriculture and development. However, fish indices were only negatively correlated to development. Macroinvertebrate indices were most correlated to physical habitat and positively correlated to bottom velocity and percent cobble. Macroinvertebrates were negatively correlated to percent silt and weakly correlated to turbidity. Fish indices were negatively correlated to bottom velocity and positively correlated to riffle embeddedness and chain roughness. Macroinvertebrate indices were positively correlated to visual habitat assessments, whereas fish indices did not have a strong correlation to visual habitat assessments. In general, sites with the highest percentage of agriculture had the lowest habitat quality and, consequently, the lowest biotic integrity. Sites within more developed watersheds generally had suboptimal habitat quality but had better ecological integrity compared to agricultural subwatersheds. Sites with intact riparian zones and forested headwaters had the highest habitat quality and ecological integrity. These results confirm the importance of healthy riparian zones for maintaining water quality and ecological integrity, especially in areas that are highly susceptible to erosion and intense rainfall. We recommend continued monitoring of water quality, biota, and land use changes throughout the region to further elucidate these relationships. We also recommend targeting watersheds with the greatest impairment or risk of impairment to provide the most ecological uplift during restoration efforts. Effective restoration and watershed management will require active participation from individual landowners. With regional partners, we will help to establish watershed coalitions to educate landowners, promote hydrologically connected communities, and enhance stewardship of our local watersheds. Additionally, the transferability of techniques we used could be tested in other regions of the state with inherently different landscape attributes.
  • Fecal Contamination Source Tracking and Forecasting to Support Recreational and Cultural Development in the Black River Watershed
    (NC WRRI, 2024-04-30) Harris, Angela; Emanuel, Ryan; Obenour, Daniel
    The Coharie Tribe expressed interest in learning more about specific CAFO and human impacts on water quality along the Great Coharie River, with special attention to spatial and temporal variability of these impacts. The Tribe’s interest also aligns with opportunities to answer fundamental research questions about water quality in North Carolina’s Coastal Plain and areas similarly impacted by industrialized agriculture. We proposed research questions and objectives intended to help meet these needs while also advancing fundamental science concerning biological water quality. What are the dominant sources of fecal contamination at 3 sites in the watershed? How do these sources vary across base flow and storm flow conditions, and warm and cold seasons? Can forecasting tools be developed to capture elevated levels of fecal contamination in the watershed to support Tribal decision-making related to the use of river? To address these questions, low frequency and high frequency (determined by base and storm flow) sampling events were conducted at three sites in the Great Coharie River watershed from March 2022 to March 2023. Each sample was evaluated for total coliforms, Escherichia coli, molecular microbial source tracking (MST) targets, Total suspended solids, Total Kjeldahl Nitrogen, the sum of Nitrate and Nitrite, Ammonia, Total Phosphorus, Orthophosphate, Temperature, pH, dissolved oxygen, specific conductivity, and turbidity. An automated DNA extraction kit was optimized for use with surface water filters and nucleic acid was extracted from each sample. Following DNA extraction, samples were analyzed using polymerase chain reaction microbial source tracking targets including LA35, Pig2bac and hCYTB484 which is sensitive and specific to swine and poultry combined, swine, and human fecal contamination, respectively. Results from the MST assays indicate that the watershed likely suffers from fecal contamination from the three target hosts. Escherichia coli data collected throughout the study indicate that the three sites have contamination levels that would deem the Great Coharie River as impaired per the United States Environmental Protection Agency’s Recreational Water Quality Criteria. An explanatory model using multiple linear regression was developed with the available data. The preliminary model revealed that 2-day total rainfall is an important covariate to help explain E. coli concentrations in the watershed. In addition to the explanatory model, a random forest predictive model was constructed to predict whether the water was at an E. coli concentration above or below the EPA recommended threshold (i.e., 126 MPN/100 mL). When performing covariate importance analysis, it was determined that 2-day total rainfall was the most important covariate of any examined in this study when predicting E. coli. Lastly, a generalized estimating equation was developed, and this model also found 2-day total rainfall to be an important covariate. It is recommended that caution be used during primary contact recreation, which includes activities that involve increased likelihood of water ingestion or immersion like swimming, at each of the three sites due to elevated levels of E. coli- especially following an intense rainfall event. We also recommend that a land use study be undertaken to determine potential management strategies to minimize fecal contamination at the Marsh Swamp site, which experienced higher levels of E. coli contamination than other sites. Additionally, further studies into the human contributions to the watershed could be performed to help identify if further interventions related to human waste management need to be made.
  • Remove Per- And Polyfluoroalkyl Substance From Water By Combined Ion Exchange and UV/Sulfite Treatment
    (NC WRRI, 2024-03-15) Sun, Mei
    Per- and polyfluoroalkyl substances (PFAS) are contaminants of concern in North Carolina. Ion exchange (IX) is effective in separating PFAS from contaminated drinking water, but incapable of chemically breaking down the contaminants. Thus, waste streams from IX, including spent resins and regenerant, contain high levels of PFAS and are challenging to be disposed of safely. This project addresses this problem by strategically combining IX and resin regeneration via chemical PFAS degradation. We hypothesize that in this treatment train, PFAS can be separated from contaminated water and subsequently mineralized for safe and feasible waste management. With the goal of sustainable and cost-effective management of IX wastes for PFAS removal, this project includes tasks of determining the most suitable chemical treatment for IX wastes, optimizing the treatment conditions, and assessing the feasibility of the treatment train for water treatment practice. In this project, we proposed and evaluated several variations of a treatment train for PFAS removal and defluorination for water treatment. The most effective option for the treatment train design we identified in this project combines IX, NaCl/methanol regeneration, distillation, and UV/sulfite defluorination. Using this treatment train, PFAS at environmentally relevant levels (ng/L) can be captured by IX to near 100% by either PFAS-specific or generic resins. The spent resins can be regenerated using 60% methanol/5% NaCl solutions and reused in the following treatment cycles, with much better regeneration performance from the generic resins than PFAS-specific resins. The waste regenerant can be distilled to separate methanol for reuse, with simultaneous PFAS enrichment and volume reduction of the waste stream. Finally, the concentrated waste (still bottoms) can be treated with UV/sulfite to transform PFAS into nontoxic fluoride. This process is effective for most PFAS with almost 100% removal and >75% defluorination, although a few short-chain sulfonates and GenX are more challenging to treat. The generic resins (e.g., IRA910 tested in this project) are recommended for the treatment train over PFAS-selective resins and can be reused for treatment over multiple cycles. All the detailed conditions for each treatment step were optimized. Overall, PFAS with different chain lengths and functional groups can be effectively removed and eventually defluorinated in different water matrices using the proposed treatment train.
  • Internet of Water: Research and Development Toward a Linked Data System and Foundational Knowledge Network for the Internet of Water: Final Report
    (NC WRRI, 2023-10-31) Doyle, Martin; Onda, Kyle
    Internet of Water: Research and Development Toward a Linked Data System and Foundational Knowledge Network for the Internet of Water is a project designed to improve the discoverability of water-related datasets. The main objective of this project was to establish a foundational framework for a contributor-based system that facilitates regular harvesting and cross-referencing of metadata through two key components: (1) facilitating the Internet of Water community in publishing detailed, machine-readable, and cross-referenced metadata (linked data); and (2) developing a centralized crawler/harvester to catalog all the linked data into a single knowledge graph, serving as a part of the index for eventual Internet of Water search utilities. The project built on previous efforts to continue and enhance the development of Geoconnex, a linked data system and foundational knowledge network for water data. Geoconnex can be conceptualized as an operationalization of the Open Geospatial Consortium Environmental Linked Features Interoperability Experiments for the United States in the domains of water science and management. Our methods encompassed data-publisher-oriented research and engagement, development of Geoconnex architecture, and implementation of the Geoconnex system. The results of this project include a performant infrastructure leveraging semantic technology and open, modern API standards that allow data providers to independently publish metadata on the web in a manner that results in their data becoming linked to other providers’ data where spatially, hydrologically, and topically relevant. If adopted by data providers at a wide scale, this infrastructure would enable users to easily find water information across a variety of topics and geographies via user-friendly search applications. Through this project, we have concluded that further work is needed to encourage participation in the system and use of the infrastructure. We recommend that future work include the development of a user-friendly interface, technical advancements to improve the usability of the system and enable scaling, a promotional campaign to build the userbase, and the development of a governance structure. Potential future work could also establish best practices to use the same technologies to enable the automatic translation of observation and model data across data systems, fostering improved interoperability of data in addition to the improved discoverability already enabled by the currently implemented infrastructure.
  • Enabling rural water utilities to create, transfer information, and use digital service area boundaries: Year 2 final report
    (NC WRRI, 2023-10-31) Ward, Ashley; Onda, Kyle
    Enabling Rural Water Utilities to Create, Transfer Information, and Use Digital Service Area Boundaries is a project that aims to increase equity by lowering the digital divide for small utilities by providing free, open-source tools that support regional and statewide planning. The project’s objectives are to (1) enable water and wastewater utilities to create and maintain digital service area boundaries through the development of an open-source, free technology called BoundarySync (formerly ABOUT-US); and (2) create an online tool that spatially links digital service area boundaries with parcel data to better equip small rural utilities to meet new Environmental Protection Agency (EPA) regulatory reporting requirements through the development of the Lead Service Line Inventory Tool (LSLIT). The creation of BoundarySync, in combination with LSLIT, will assist small rural utilities in meeting EPA’s new reporting requirements and provide more complete information on where lead service lines are likely to exist in their service areas. This information may inform the allocation of federal funding to support lead service line replacement and could help utilities pursue external funding for infrastructure improvements and enhance decision-making. In addition, BoundarySync will provide the state with up-to-date data to support regional and statewide planning. In Year 1, we developed BoundarySync, a user-friendly tool for the creation and maintenance of digital service area boundaries and assessed how rural utilities could use digital service area boundaries in combination with other data to solve a pressing challenge. Through these engagements, we learned that new EPA rules requiring water utilities to develop lead service line inventories placed a significant burden on rural water utilities which often do not have access to GIS software. In Year 2, we developed the LSLIT to give small rural utilities an easier way to comply with the new rules. Our methods included (1) close collaboration with the North Carolina Rural Water Association (NCRWA) to identify and reach a representative group of users to provide feedback on tool planning and development, (2) engagement with the North Carolina Department of Environmental Quality (NC DEQ) on the future hosting and maintenance of BoundarySync, (3) leveraging additional funding for software development support to ensure that BoundarySync had a modern and intuitive design, (4) working with a Ph.D. student and a postdoc to integrate digital service area boundaries created in BoundarySync with parcel data through LSLIT, and (5) participating in NCRWA conferences and workshops and developing instructional and promotional videos to encourage adoption and use of BoundarySync and LSLIT. Our results include (1) BoundarySync; (2) engagement with a representative group of water utilities, NCRWA leadership, and NC DEQ in a user-based design process to refine BoundarySync’s usability; (3) the Lead Service Line Inventory Tool (LSLIT); (4) engagement with rural water utilities in the planning, development, and continued improvement of LSLIT; (5) a GitHub repository for BoundarySync and LSLIT enabling other states or entities adapt these tools to their needs; (6) two instructional videos (Getting Started in BoundarySyc and Using the Admin Role in BoundarySync) and a promotional video about BoundarySync; and (7) a promotional video that details the challenges rural water utilities face in modernizing their data infrastructure and highlights NCRWA’s work. Through our engagements with North Carolina rural water utilities and partners in other states, we have discovered that there is a great deal of need for these two products not only in North Carolina but in rural areas across the US. As a result, we recommend that in addition to continuing to host, maintain, and promote these two tools in North Carolina we develop a national version of LSLIT and promote the use of LSLIT and BoundarySync throughout the US.
  • Performance Evaluation of Novel Resins in Flow-Through Columns for PFAS Removal from Drinking Water and Treated Wastewater
    (NC WRRI, 2023-11-30) Coronell, Orlando; Leibfarth, Frank; Manning, Irene; Gorzalski, Alexander; Chew, Guan
    Per- and polyfluoroalkyl substances (PFAS) are known bioaccumulative and persistent chemicals which pollute natural waters globally. However, there exists a lack of granular sorbents optimized to efficiently remove PFAS at environmentally relevant concentrations. To address this need, we previously developed a platform approach for fabrication of regenerable granular sorbents (i.e., ionic fluorogel (IF) resins) that selectively remove PFAS over background competing contaminants. In this project, we modified 1st generation IFs to realize structurally tunable and chemically stable resins with systematic variations of network architecture and cation density. Chemical stability was demonstrated through accelerated degradation studies. Investigation of the library of chemically stable IFs enabled insights into structure–property relationships important to high affinity PFAS binding. Results show that the chemically stable IF resin outperformed a leading commercially available ion-exchange resin in batch and column tests. Using as a guiding principle in sorbent development the cost and availability at large scale of base materials, we developed a 2nd generation IF resin based on trifunctional crosslinkers with a more translationally relevant profile in terms of chemical inputs and cost. Batch results from challenge tests with various NC waters showed that the 2nd generation IF resin had a PFAS-removal performance level intermediate between those of two leading commercial ion exchange resins. The 2nd generation IF resin had a substantially better performance in drinking water sources than in wastewater matrices. Results also showed that there is the potential to improve PFAS removal performance via optimization of the resin synthesis procedure. Additionally, because of the high modularity and copolymerization amenability of the platform chemistry used for IF synthesis, we hypothesize that future tuning of the fluorinated backbone can be used to optimize PFAS partitioning, and resin swelling and flexibility and enable superior PFAS removal across water matrices.
  • A citizen science internship program to quantify racial and economic disparities in lead levels in drinking water across North Carolina
    (NC WRRI, 2023-09) Cooper, Caren; Berglund, Emily; Johnson, Valerie
    “A Citizen Science Internship Program to Quantify Racial and Economic Disparities in Lead Levels in Drinking Water Across North Carolina” (Grant #21-17-W) has four objectives: 1) characterizing lead plumbing in North Carolina, 2) mentoring underrepresented undergraduate researchers, 3) increasing public awareness and self-efficacy related to drinking water, with a focus on marginalized communities, and 4) refining a statistical model to estimate water lead levels using citizen science data. To characterize lead plumbing in North Carolina, we engaged participants in the Crowd the Tap citizen science program. Since Crowd the Tap was started until August 8, 2023 1796 North Carolina residents have screened their home through Crowd the Tap, identifying 1989 in-home plumbing materials and 1671 service line or well casing materials, of which 32 in-home pipes and 20 service lines or well casings were leaded. Of these households, 365 had their water tested in the lab and 208 conducted at-home lead tests. Crowd the Tap identified 226 households with some detectable lead levels, seven of which were greater than 10 ppb. There were nine positive at-home lead tests. We have recruited 43 undergraduate and post-baccalaureate research interns. We have recruited 12 Shaw University students, one student from North Carolina Agricultural and Technical University, one student from Montreat College, 28 students from North Carolina State University, and one post-baccalaureate intern. Altogether, 16 of the 43 interns have underrepresented racial or ethnic identities, and six others are people of color. Through these internships, students learned about public engagement through faith communities, community activist groups, community-based health organizations, and in their own communities. To increase public awareness and self-efficacy, we engaged people through various partnerships, which ensured that we engaged people of diverse backgrounds. We recruited 828 university students, 480 households connected to university interns, 296 households from high schools, 26 from faith communities, 21 from a corporate volunteer program, 31 from the Southeastern Wake Adult Day Center (a community-based health organization that supports primarily low-income Black residents of Wake County), and 109 households came to the project independently. Altogether, we recruited 969 White households, 238 Black or African American ones, 109 Asian, 71 Hispanic or Latino, three American Indian or Alaska Native, one Native Hawaiian or Other Pacific Islander, and 231 households with two or more races or ethnicities present. We are using the citizen science data collected from Crowd the Tap to test a Bayesian Belief Network (BBN) model to predict lead levels in household drinking water. Preliminary results indicate that water quality test strips have high degrees of error and that the BBN has low predictive performance for predicting lead levels in drinking water. Our analysis is ongoing, and we are continuing to explore BBN’s predictive ability for a range of samples. Thus, Crowd the Tap has made significant progress towards each of these objectives. These results can provide guidance to utility companies seeking to prioritize areas for lead infrastructure removal that prioritize equity. Furthermore, our program has supported the professional development of undergraduate researchers from Historically Black Colleges and Universities and/or have underrepresented identities.
  • Data-Driven Analytics Tools to Support Prioritized Management of Stormwater Infrastructure
    (NC WRRI, 2023-09-19) Barclay, Nicole; Smith, Michael; Qi, Jingyi
    Maintenance of aging underground infrastructure compounded with urbanization encroachment and economic pressures have caused a number of challenges for municipal agencies that are tasked with managing and operating these infrastructure systems. However, the budget and time constraints that municipalities often face present challenges for managing culverts. Reliable prediction of infrastructure conditions can help these municipal agencies manage this burden for culverts by providing decision support regarding optimal renewal, replacement, and maintenance, which offers reduced overall costs and improved system reliability. As opposed to traditional physics-based models, data-driven models (e.g., machine learning) offer benefits in processing large datasets where some data is missing or there is “noisy” data. Considering these compounding issues, our study aimed to develop predictive models for culvert condition assessment to better inform repair and replacement schedules. The overall goal is to complement and bolster existing toolsets for prioritization & asset management. The project objectives were to 1) estimate current conditions based on measured data and infrastructure characterization, 2) design models to predict conditions via data analytics, 3) train and validate the models by evaluating each model and verifying results, and 4) identify at-risk pipelines and culverts within the study area. This report describes the data-driven modeling approach via machine learning for predicting culvert conditions to identify at-risk culverts using Charlotte-Mecklenburg Stormwater Services existing data inventory. Several supervised machine learning models were considered and their performance evaluated, respectively. Simulation test results and discussion are included to showcase the key contributions and findings of this work. The results show that one model, the random forest classifier (RFC) gives the prediction performance. The main contributions highlighted in this report include: 1) the performance of four different machine learning models which are compared for the target application to predict culvert conditions, 2) the application of the model for stormwater infrastructure asset management, 3) the viewpoint that the machine learning approach offers economic savings for utilities, 4) the machine learning approach provides potential for improved reliability of stormwater infrastructure.
  • Empowering underrepresented citizens of Charlotte-Mecklenburg with a voice and role in municipal storm water program goals
    (NC WRRI, 2022-08-31) Patterson, Bryan; Guyer, Regina; Raburn, Kari
    In our research study “Our Voice Our Water” focused on community engagement and stormwater knowledge within three communities in Charlotte, NC. A goal of our study sought to address the linkages between stormwater and trash, litter, and/or illicit discharges. The neighborhoods selected were historically underserved communities of Historic Washington Heights, Lincoln Heights, and Northwood Estates. Primary research objectives included: 1) Applied research techniques by Johnson C. Smith University faculty, Rising Solutions, PLLC staff, and an AmeriCorps Member were implemented to access the behaviors and knowledge of stormwater issues with community citizens. Community members were encouraged to “Be Heard” by sharing their knowledge and perspectives. Research techniques included focus groups, surveys, and stream indexing. 2) The 3-1-1 Call Center Data was evaluated to gain a historic understanding of the citizens’ concerns and follow up actions by Charlotte Mecklenburg. 3) Engagement with neighborhood leaders and citizens to build community trust and understanding through education and outreach opportunities as well as community meetings. The “3-1-1, Having a Voice Workshop”, was a model to provide opportunities for citizens to have a voice by expressing concerns which, in turn, helps to build relationships, two-way communication, and enhance trust. The “Neighborhood Empowerment Model” was a powerful result of the research, it enabled us to create a new systematic approach to engage with stakeholders and communities. These purposeful interactions with neighborhood leaders and city and county municipalities-built community trust and understanding through education and outreach opportunities as well as increased community stream and residential cleanups.
  • Intensification of Anaerobic Digestion: Co-Digestion of Grease Interceptor Waste (GIW) with Thermally Hydrolyzed (TH) Biosolids
    (NC Water Resources Research Institute, 2022-07-12) de los Reyes, Francis
    Intensifying methane production during anaerobic digestion (AD) is a key factor in making anaerobic digestion economically feasible. We explore two key ideas in biomethane production: using thermally hydrolyzed (TH) biosolids, and co-digestion with grease interceptor waste (GIW). We used modified biochemical methane potential (BMP) tests in several Phases in triplicate: Phase 1 investigated the optimal COD-based substrate to inoculum (S/I) ratio for mono-digestion of TH biosolids and GIW, Phase 2 investigated co-digestion, and Phase 3 investigated codigestion under conditions modified to be more like those of full-scale operations. Application of a TH pretreatment to Phase 1 biosolids, Phase 3 mixed and thickened (M&T) biosolids, and Phase 3 co-substrate (M&T biosolids and GIW) increased the fraction of soluble to total COD by 51.7%, 25.2%, and 25.5%. Modified Gompertz models identified maximum methane potential (MMP) and maximum daily methane production rate (MDMPR). The most productive Phase 1 GIW mono-digestion had a MMP three times that of Phase 1 TH biosolids but had a lag period that was almost seven times longer. In Phase 2 biosolids monodigestions, TH increased MMP and MDMPR in biosolids but no significant effect was observed in GIW. Inclusion of TH GIW and GIW without TH in Phase 2 co-digestions both increased MMP and MDMPR, compared to mono-digestions of biosolids, but there was no significant difference in MMP or MDMPR between these co-digestions. These are consistent with very similar microbial communities at the end of the incubations (analyzed using 16S gene sequencing). Modified Gompertz Model fitting of Phase 3 results also showed no significant difference between TH and raw co-digestions of M&T biosolids and GIW in terms of MMP or MDMPR. Again, these were consistent with the microbial community analysis results, that showed very similar communities at the end of the runs. One reason for the difference in TH effects between Phase 3 and other Phases was the inclusion of primary solids in M&T biosolids. The benefits of TH appeared to be less dramatic in substrates that contained primary solids than in those exclusively composed of waste activated sludge. TH was shown to be beneficial in mono-digestion of waste activated sludge biosolids, more than doubling MMP and increasing MDMPR by more almost seven times. However, TH does not intensify anaerobic digestion when applied to co-substrates of biosolids and GIW. This study found that TH is suitable for application to biosolids at the current state of practice. Incorporation of TH GIW showed no consistent benefit over addition of untreated GIW. The application of TH to GIW does not always lead to increased methane yield or improved digestion kinetics: many factors, including the type of biosolids (WAS vs. primary sludge; thickened vs. unthickened) affect the methane yield.
  • Biological Condition in NC Urban Streams Phase III: Development of a Web Application
    (NC Water Resources Research Institute, 2022-05-13) Paul, Michael; Allen, Diane
    Using the model of biological potential along urban1 land cover gradients in North Carolina constructed using EPT and biotic index metrics, a web application (ArcGIS StoryMap) was constructed to visualize the results for every urban (>1% impervious cover) watershed in North Carolina. The web application allows any user to identify the potential EPT richness and NCBI score for any watershed constrained by urbanization. This constrained biological potential is provided as both a scaled value (comparable across the state) and ecoregion specific actual predicted score. Watershed managers should be able to use this information to help guide urban stream prioritization, planning, restoration and monitoring and the concept would support construction of a tiered aquatic life use framework. NCDEQ agreed to host the web application as part of the ArcGIS StoryMap service and the plan is to migrate the web application to the state for this purpose.
  • Tertiary Anammox for Sustainable Nitrogen Removal
    (NC Water Resources Research Institute, 2022-04-28) Aziz, Tarek; de los Reyes, Francis; Young, Anthony
    Concentrated discharges of nitrogen into our waterways have led to serious environmental impacts, such as eutrophication and algae blooms. Due to these discharges, stringent total nitrogen (TN) discharge limits have been placed on Water Reclamation Facilities (WRFs). Mainstream deammonification offers a novel approach for improving nitrogen removal at these facilities by harnessing anaerobic ammonia oxidizing bacteria (Anammox). However, the success of this process has been limited. Previous research at NC State explored the conversion of tertiary filters to mainstream deammonification filters which were shown to be capable of an average total inorganic nitrogen (TIN) removal rate of 91%, with effluent TIN reaching below 2 mg/L-N. However, this research suggested that nitrate loading concentrations were the limiting factor in meeting 2 mg/L-N TIN effluent limits. Incorporating partial denitrification (PdN), the conversion of nitrate to nitrite for subsequent use in Anammox, offers a promising solution. The goal of this research was to explore the TIN removal capability and feasibility of a PdN-Anammox (PdNA) filter under typical filter loading conditions, in comparison to a conventional denitrification (FdN) filter. Different carbon loading strategies in pilot scale filters confirmed that maintaining a nitrate residual of >1.5 mg-N/L allowed for the highest PdN conversion efficiencies and in turn increased Anammox activity. Furthermore, the carbon requirement (C/N ratio) of 5.1 g COD/g TIN in pilot scale FdN was higher than the 2.08 g COD/g TIN achieved in the PdNA filters, demonstrating the cost benefits associated with mainstream deammonification and the application of PdNA. In addition to greater than 50% reduction in supplemental carbon, other benefits include nearly 38% reduction in oxygen demand and reduction in excess sludge in comparison to conventional BNR processes. Through this pilot study, PdNA was demonstrated to provide TIN removal efficiencies of greater than 80%. With further research, stable TN removal at WRFs at typical filter loading rates can be achieved, and with that, the possibility for substantial operational expenditure (OPEX) savings.
  • Fostering Engagement in the Cottage Grove Neighborhood Through Community Involvement in Riparian Cleanup to Enhance Stormwater Quality
    (NC Water Resources Research Institute, 2021-12-12) Sills, Stephen
    This community engaged project with residents of the Cottage Grove neighborhood in East Greensboro addressed environmental justice concerns with unnamed tributaries of South Buffalo Creek that pass through a former landfill containing incinerated waste. Many communities of color have, over the last century, experienced the destruction of historical landmarks, erosion of social ties through urban renewal projects, and challenges to health by environmental hazards. This project involved the residents and children of the Cottage Grove community through in collecting oral histories of long-time residents, conducting surveys, volunteering during trash/litter clean-up days (also including university student and environmental groups), and finally in citizen-science stormwater data gathering. Twice monthly we meet with residents and community leaders. Youth environmental education included virtual summer camps, environmental justice literacy lessons, and an Earth Day challenge week. We held quarterly community workdays with over 242 volunteers the neighborhood, local universities, other environmental groups, and AmeriCorps. More than 250 bags of litter, a dozen shopping carts, bicycles, strollers, car seats, fire extinguishers, and other miscellaneous debris have been removed from the creek. We collected oral histories, surveys, and historical documentation instrumental in bringing $356,000 in additional funding to environmental justice activities in the neighborhood including a three-year Robert Wood Johnson Foundation Award.
  • Effects of Extreme Flooding on Water Quality in Areas of Dense Food Animal Production
    (NC WRRI, 2022-02-07) Stewart, Jill; Serre, Marc; Kothegal, Nikhil; Christenson-Diver, Elizabeth
    Storm events are expected to increase with climate change, with the potential to adversely impact environmental quality and public health. This study assessed impacts of Hurricane Florence on water quality in areas of dense food animal production. Twelve surface water sites in rural, eastern North Carolina were sampled before and after Hurricane Florence to assess storm effects and duration of impacts. Concentrations of fecal indicator bacteria Escherichia coli were not significantly different in our first sampling event, conducted 10 days after Hurricane Florence. Instead, the longitudinal data show that first runoff events, defined as rainfall following a dry period, are associated with increased concentrations of fecal indicator bacteria in these watersheds. Additionally, watersheds with larger commercial hog operations (CHOs) and CHOs closer to sampling sites, as well as sites with larger number of households closer to sampling sites had increased E. coli concentrations. Unlike E. coli concentrations, we found that mean ranks of microbial source tracking markers associated with swine wastes (pig-2-bac) and human wastes (HF183) were higher immediately after Florence (Mann Whitney U p=0.009, p=0.0003 respectively). The swine MST marker was markedly elevated at several sites in watersheds with CHOs, while the human MST marker suggested diffuse human contamination across study sites. Antimicrobial resistance among E. coli isolated from study waters was also higher in watersheds with CHOs. Resistant E. coli was detected in 46% (n=147) of samples collected downstream of CHOs compared to 22% (n=94) of samples collected in watersheds without CHOs, resulting in a relative risk of 1.47 (95% CI: 1.21, 1.78). Bacteria with multiple antibiotic resistance was isolated in 15 of the CHO-associated samples and 1 background sample. Occurrence of AMR does not appear to be driven by precipitation, suggesting other dynamics such as spray events or antibiotic use practices may better explain contributions to resistant bacteria to surface waters. These results help clarify the effects of extreme flooding on microbial contamination of surface waters and can inform strategies for waste management, antibiotic use, and one health surveillance. Ultimately, this work contributes information to build more resilient agricultural systems and communities better prepared to weather the storms that frequent the North Carolina coast.
  • Investigating the Microbial Culprits of Taste/Odor Issues in City of Durham Drinking Water Reservoir Lake Michie and Algicidal Mitigation Tactics
    (NC WRRI, 2022-01-31) Paerl, Ryan; Huang, Hwa; Ehrlich, Linda
    Project title: Investigating the Microbial Culprits of Taste/Odor Issues in City of Durham Drinking Water Reservoir Lake Michie and Algicidal Mitigation Tactics. Taste and odor (T&O) compounds, especially geosmin and 2-methylisoborneol (2-MIB) are of concern to water managers worldwide and those serving large cities within the Piedmont region of North Carolina (NC). Project objectives: 1) Identify the taste/odor producing populations in Lake Michie (LM) by microscopy or flow cytometry surveying, genetic data, and/or correlation between hydrologic, biochemical conditions and T&O compound concentrations; 2) Evaluate if flux of T&O compounds from cells can be minimized by reduced dosages of already used algicide EarthTec. Methods: Archived data for LM from City of Durham Water Management (CDWM) were examined to determine longer-term (6 year) trends in biochemical and physical conditions along with T&O compound concentrations, as well as contextualize higher resolution sampling in 2020. LM water was collected in 2020 from 2x the Secchi depth for multiple chemical and biological analyses - including the collection of biomass from two different size fractions (>8μm and 8-0.8μm) for DNA extraction and downstream PCR amplicon or metagenomic sequencing. Samples were also collected for microscopic analysis of plankton diversity and biovolume, as well as flow cytometry-based cell counts (phytoplankton and bacteria). Bottle incubations were used to assess the efficacy of the CuSO4 containing algaecide EarthTec in reducing concentrations of geosmin and 2-MIB. Results: Geosmin reached higher average and maximum concentrations in LM samples in the 6 years of sampling LM and is increasing over time, although datapoints supporting the trend are limited. 2-MIB also exceeded the human detection threshold of 10 ng/L in 5 of 6 years and remains a T&O concern. Geosmin often peaked earlier than 2-MIB in late spring into early summer. Dolichospermum biomass and relative abundance of geoA sequences increased in parallel with geosmin in our intensive 2020 sampling campaign. Metagenome assembled genomes (MAGs) also point to Dolichospermum populations as the dominant geosmin producers, while also uncovering Chloroflexota populations as geosmin sources which has not been previously reported. One putative 2-MIB producing Microcoleus (N-fixing cyanobacterial genus) population was uncovered based on metagenomic sequencing. Conclusions & recommendations: Filamentous N-fixing cyanobacteria (esp. Dolichospermum spp., putative Microcoleus) are key sources of T&O to LM. Previously unrecognized Chloroflexota are sources of geosmin and their contribution of the compound to the greater lake, and other lakes, requires further investigation. Increases in the relative abundance of Dolichospermum geoA sequences paralleled increases in geosmin, thus PCR-based assays hold potential as a rapid geosmin indicator tool. Overall, geosmin concentrations are on an upward trajectory and this is likely to continue with continued increases in average air temperature in the southeastern US and low total N to P ratios in LM that favor N-fixing geosmin producers. Reductions in P may help limit the growth of T&O producing N-fixers, but likely will require substantial efforts and/or financial investment (e.g. dredging). EarthTec treatment of LM water at concentrations previously used by CDWM often caused increases in geosmin (and 2-MIB at times) in our experiments. Lower EarthTec additions (ca. 0.0125 mg/L CuSO4) appear more effective to limit algal growth and T&O concentrations and are recommended.
  • Assessing Controls on Nutrient Loading at the Watershed Scale through Data-Driven Modeling
    (NC WRRI, 2022-02-07) Obenour, Daniel R.; Mitasova, Helena
    Anthropogenic nutrient loading is a critical driver of water quality throughout North Carolina and much of the world. Nutrient (nitrogen and phosphorus) loading has increased over the last century due to fertilization of crops and green spaces, as well as waste from humans, pets, and livestock. The most salient outcome of nutrient loading is eutrophication of lakes and coastal waters, often leading to harmful algal blooms and hypoxia, which jeopardize water supplies, wildlife habitats, and public recreation. While sources of nutrients have been identified and many control measures have been proposed, there remains a need to quantitatively assess these sources and controls, particularly at the watershed scale. In this project, we develop a modern, data-driven approach to characterizing nutrient sources and control strategies, using the Falls and Jordan Lake watersheds of North Carolina as our study area. The approach leverages large databases of water quality, hydro-meteorology, and watershed attributes, which have been developed by federal, state, and local governments over the last few decades. The approach also advances a “hybrid” watershed model that integrates a mechanistic representation of nutrient fate and transport within a Bayesian framework, so that prior knowledge of loading and transport rates is updated through data-driven inference with quantified uncertainties. As an integral part of this effort, we develop a comprehensive geospatial database on watershed development, buffers, and stormwater management regions. We then use the Bayesian hybrid modeling approach to assess nitrogen and phosphorus export from lands with different forms of development and stormwater management. Results generally support the hypothesis that stormwater management has been effective. Streamside vegetated buffers are associated with approximately 36% and 37% reductions in TN and TP, respectively; and post-construction SCMs are associated with 43% and 52% reductions in TN and TP, respectively. Finally, we apply the model to assess hypothetical urban growth scenarios. These future scenarios indicate that stormwater management (SCMs and buffers) will substantially reduce (but not fully compensate for) the impacts of continuing urban development.
  • Multidimensional Assessment of North Carolina Community Water System Vulnerabilities
    (NC WRRI, 2022-01-31) Mullin, Megan; Pickle, Amy
    Our project, Multidimensional Assessment of North Carolina Community Water System Vulnerabilities, assessed the nature and distribution of vulnerabilities in North Carolina community water systems through achievement of two objectives. First, we developed a network-based method for assessing interrelationships among water system vulnerabilities and used expert information and data from several sources to apply the method to North Carolina water systems. Our measurement of water system characteristics relied on population data estimated from a newly generated digitized statewide map of water system service area boundaries developed in collaboration with the Water Supply Planning Branch at the Division of Water Resources (DWR). Applying our multicriteria approach to 319 North Carolina water systems, we found that vulnerabilities are dispersed: poor performance on one dimension, especially compliance with safe drinking water regulations, does not indicate poor performance on other dimensions. We also found that financial vulnerabilities are correlated with economic conditions in the communities served—in particular, water systems struggling to meet their debt obligations tended to serve disproportionately low-income populations. Second, we used web scraping and automated data processing to measure and analyze the signals that the public receives about water system performance through news coverage of boil advisories, water main breaks, and other service disruptions. We found that coverage of service disruptions as a proportion of overall news coverage has not increased over time. Although coverage rises during severe weather, the most common news attention to infrastructure failure is not tied to weather, planned disruption, or human error—instead, it seems to signal the deterioration we would expect to see in aging systems. We carried out our work while the State Water Infrastructure Authority and the Local Government Commission were developing the Viable Utility Program and used much of the same data. Our purpose was different, however: whereas the Viable Utility Program seeks to identify particular utilities in need of assistance, our aim was to identify patterns in vulnerabilities across water systems to inform policy-making that addresses multiple systems. Overall, our results demonstrate the tradeoffs that water systems face in balancing affordability against the capacity to deliver drinking water reliably over the long term, especially in lowincome communities. Our findings also indicate that fiscally distressed water systems are performing by other measures similarly to non-distressed small utilities, suggesting that financial support could go far in improving water system performance. We have maintained ongoing communication with partners in state water agencies about our methods and findings, and we have conducted broader outreach with water systems about the service area maps. Members of our team have met four times with federal officials about applying knowledge from our vulnerability assessment to tools and requirements for the equitable distribution of water infrastructure funding under Justice40. We have produced four articles for academic and practitioner audiences based on our work (two published, one under review, one in preparation).
  • Understanding the FOG deposit adhesion mechanism on different sewer line surfaces
    (NC WRRI, 2022-01-31) Ducoste, Joel J.; Pour-Ghaz, Mohammad; Kusum, Samrin Ahmed
    The adhesion of fat, oil, and grease (FOG) deposits in sewer pipes causes 25% of the Sanitary Sewer Overflow (SSOs) in the USA. Additionally, the sewer collection system in the U.S is old and requires replacement or renovation. One potential solution to the FOG deposit accumulation challenges in the collection systems is to design new sustainable sewer line construction materials that reduces the adhesion of these deposits on sewer pipe walls. Previous research has only reported the FOG deposit formation mechanism and the factors affecting those formations. Yet, no research has been performed to understand the FOG deposits adhesion mechanism. This study provides an improved understanding of the FOG deposit adhesion mechanism inside sewer lines by testing various materials, i.e., concrete, PVC, granite, limestone, and porous ceramic materials for a 30-day FOG deposit adhesion test. The test materials were prepared by varying a number of surface properties such as surface roughness, porosity, pH, and surface chemical composition. After analyzing the FOG deposit adhesion test results on various test materials, research results revealed that only the sewer line materials containing calcium as a strong electropositive Lewis acid bonding sites resulted in the FOG deposit adhesion on their surface. In addition, samples having high surface roughness, pH, and porosity also resulted in higher FOG deposit accumulation on their surfaces. The FTIR analyses of FOG deposits formed on different sewer line materials showed that a high fraction of saponified calcium soaps were formed on concrete samples. Moreover, the percent soap content of the FOG adhered on concrete samples exhibit a spatial variation with the layer adjacent to the concrete surface had a higher percentage saponification (82%) compared to the layer adjacent to the wastewater interface (38%). The result of this study encourages municipalities to avoid the use of sewer system cleaning process that damages the surface of sewer lines and introduces additional surface roughness. Also, a regular cleaning of sewer lines is encouraged to avoid the FOG build-up by rinsing the weakly adhered FOG deposits.