Urban Water Consortium

Astrid Schnetzer, NC State

Awareness of exposure risks to cyanobacterial toxins through drinking water has risen dramatically (Cheung et al., 2013) continuing to bring Cyanobacterial Harmful Algal Blooms (CyanoHABs) to the center of media reports (e.g., Ohio lakes). CyanoHABs adversely affect freshwater lakes and estuaries as excess biomass leads to discoloration, odor issues, decreased oxygen levels and subsequent fish kills. Furthermore, cyanobacteria (or blue-green algae) produce various types of cyanotoxins including hepatotoxins, neurotoxins, cytotoxins and/or gastrointestinal toxins that have severe short- and long-term health effects from tingling and burning, to respiratory failure and death (Backer et al., 2015; Carmichael, 2008). Problems associated with CyanoHABs have been linked to periods of increased water temperature (climate variability) and increasing nutrient loading which may favor taxa shifts from non-toxic to toxic cyanobacteria (Anderson et al., 2002; O’Neil et al., 2012; Paerl and Huisman, 2008). Recent studies confirmed the presence of microcystin in 37% of 75 tested streams throughout the Southeast US, including North Carolina (Loftin et al., 2016a). A recently published nation-wide survey on cyanotoxins, in conjunction with EPA’s 2007 National Lake Assessment, showed the presence of potential anatoxin-, cylindrospermopsin-, microcystin- and saxitoxin-producing cyanobacteria in 67–81% of the screened samples from a total of 1,161 lakes and reservoirs (Loftin et al., 2016b). Despite ongoing research efforts to address CyanoHAB issues, major knowledge gaps in our understanding of bloom dynamics exist due to methodological challenges in:- Detecting and quantifying varying cyanotoxins over natural concentration ranges- Identifying and quantifying cyanobacteria at high taxonomic (ecologically meaningful) resolution (toxic versus non-toxic species/strains)The proposed study addresses knowledge gaps on year-round toxin absence/presence in NC water bodies to inform present and future monitoring strategies and decision making.

Tarek Aziz, NC State

The use of artificial mixing has been proposed as a means of suppressing the formation of algal (phytoplankton) blooms in freshwater and coastal waterbodies. However, there are conflicting reports on the performance of such systems, with sparse data relating to how artificial mixing affects bloom formation in North Carolina (NC) reservoirs. An understanding of the linkages between blooms, artificial mixing, climate variability, and other water quality constituents is critical to effectively managing water supplies and developing useful geo-engineering solutions. In this proposed research we aim to (1) conduct field campaigns in multiple Piedmont reservoirs to measure vertical diffusivity, water quality, and phytoplankton assemblages in natural and artificially mixed conditions, (2) perform statistical (hierarchical) modeling of vertical diffusivity and phytoplankton concentrations to help identify and quantify key biophysical relationships, (3) perform mechanistic water-column modeling to generalize the results obtained in (2), and (4) develop a decision-support tool from the data and analysis performed in objectives (1) – (3) to predict algal type and abundance under different artificial mixing and background physical and chemical scenarios. Findings from this research will provide new insights into the impacts of both natural and artificial mixing in Piedmont reservoirs, and aid engineers and managers in developing strategies to protect the beneficial uses of these reservoirs.

Francis de los Reyes, NC State University

Fat, oil, and grease (FOG) generated at food service establishments are removed by grease abatement devices to reduce the incidence of sanitary sewer overflows. In North Carolina, grease interceptor waste (GIW) pumped from the food service industry is treated as septage and either land applied or composted as a soil amendment. The anaerobic co-digestion of GIW provides a value added disposal option whereby GIW can be used to generate electricity at wastewater treatment facilities. Previous research at NC State, funded by the WRRI, has shown that addition of GIW results in increases in biogas production of up to 336%, the highest levels reported in the literature. These results directly impact the economic feasibility of operating GIW co-digesters, specifically with respect to maintaining high methane yields. However, the interactions between substrate variability (high FOG and food solids) and microbial community adaptations are not known, and directly impact start-up times and process resilience and resistance. This is an important issue in full scale operation, since the collected GIW can vary in strength and characteristics on a daily or per load basis. The overall objective of this project is to understand substrate-community interactions to optimize anaerobic co-digestion, particularly to minimize start-up time, and increase process resilience and resistance. This will lead to operation and start-up procedures that can be used in full-scale implementation of anaerobic co-digestion of GIW in utilities in NC and around the country.

Mark Sobsey, UNC-Chapel Hill

Regulations for NC type 2 reclaimed water (NCT2RW) address risks from pathogens by specifying log10 reductions and effluent quality for bacteria, virus and protozoan parasite indicators and treatment including dual disinfection by UV radiation and chlorination (or substitutes). There are little to no data for NC reclaimed water facilities to know if microbial requirements are met, if indicators predict water quality and treatment performance for pathogens and if NCT2RWs from current systems pose low pathogen health risks from various exposure pathways of allowed non-potable uses or as source water for potable drinking water. New NC legislation approves potable reuse of NCT2RW for drinking water. There is now an urgent need to quantify microbial quality and human health risks from exposures to NCT2RW in order for stakeholders to make informed use decisions. Objectives. The overall objectives are to determine the microbial quality of NCT2RWs, run-of-river source waters and mixtures of them from NC facilities and then do quantitative microbial risks assessments (QMRAs) on their microbial health risks based on microbial quality and various exposures resulting from different non-potable and potential potable uses. Methods. 1. Do monthly and episodic (storm events) sampling and analysis for the microbial quality of NCT2-like RW, raw sewage, and run-of-river source waters of selected treatment facilities. Measure concentrations of NCT2RW fecal indicators (E. coli bacteria, coliphage viruses and Clostridium perfringens as a protozoan parasite surrogate) and key pathogens, specifically, Salmonella and selected human enteric viruses (adenoviruses and noroviruses). 2. Use levels of fecal indicators and pathogens in NCT2-like RW and raw sewage to determine log10 reductions and compare to those of the regulation. Also compare log10 microbe levels in NCT2-like RW to run-of-river drinking source waters at various times and conditions. 3. Mix NCT2RW at 20% with run-of-river source water, store mixtures for 5 days at 5 and 25°C with and without mixing and measure initial and final microbe levels and their reductions. 4. Use indicator and pathogen data in NCT2RW, source waters and mixtures of 20% NCT2RW water in source water stored for 5 days to do QMRA analyses for (1) exposures from various nonpotable uses and compare them to US EPA recreational water health risk levels and (2) for potable reuse of 5-day stored mixtures of NCT2RW and source waters, and compare risks to US the EPA acceptable drinking water microbial risk level of 10-4 infections/person/year, after accounting for further microbial reductions by conventional drinking water treatment. Expected outcomes. Reliable data on the microbial quality of NCT2RW and drinking source waters and QMRAs of health risks from various water exposure scenarios when used for non-potable purposes and as potential source water for potable use in drinking water supplies.

Detlef Knappe, NC State University

Objective 1: Through a literature review, identify (1) possible sources of 1,4-dioxane (e.g. industrial usage, manufacturing byproduct, landfill leachate, etc.) and (2) effective treatment options for 1,4-dioxane removal. Objective 2: Establish occurrence of 1,4-dioxane in NC drinking water sources, identify factors that control 1,4-dioxane concentrations (e.g., source variability, stream flow), and determine 1,4-dioxane sources. Objective 3: At the bench-scale, assess the effectiveness of existing treatment processes at UWC member utilities for 1,4-dioxane removal (powdered activated carbon adsorption, permanganate oxidation, ozonation, biofiltration, photolysis by UV light) and identify treatment conditions for effective 1,4-dioxane removal. Objective 4: Identify new treatment options for 1,4-dioxane removal (O₃/H₂O₂, UV/H₂O₂, UV/chlorine, persulfate, tailored sorbents such as zeolite molecular sieves or polymers).