Charles J. Werth

Ensuring safe drinking water remains a critical public health concern in the United States, where many community water systems (CWSs) experience regulatory noncompliance with drinking water standards that are designed to protect public health. The Safe Drinking Water Act establishes a regulatory framework with enforceable standards for a variety of water quality constituents. While health-based (HB) violations are commonly used as indicators of waterborne disease risk, there is a lack of studies directly linking these violations to health outcomes. This study addresses this gap by examining the association between HB and nonhealth-based (NHB) violations in CWSs and emergency department visits (EDVs) for gastrointestinal illnesses across Texas from 2016 to 2022. Using Poisson regression, we evaluate these associations while adjusting for system characteristics (e.g., size, ownership, population served) and socio-demographic indicators (e.g., Social Vulnerability Index (SVI) and percent urban population). Results show that both HB and NHB violations are positively associated with EDV rates, and these associations remain significant after accounting for system and sociodemographic factors. To address how spatial misalignment of health and violations data impacts model estimates, we apply a bootstrap approach that confirms the statistical significance of HB violations, source water type, population density, SVI, and urban population. This study represents an important step toward evaluating service-area-level associations between regulatory water quality violations and public health outcomes and highlights the importance of improved data quality and more refined health risk indicators. As the first study to examine associations between drinking water violations and EDV rates at the CWS service-area level, our findings offer critical insights that inform future research and guide the development of more effective regulatory and public health interventions.

The increasing urgency to address nitrate (NO₃ ^–) pollution in water sources has intensified research on electrochemical nitrate reduction, a process capable of transforming NO₃ ^– into valuable ammonia (NH₃) by using renewable electricity. Copper (Cu) catalysts can reduce NO₃ ^–, but their activity and selectivity toward NH₃ can vary based on their structure, reaction environment, and support material. This study examines the efficacy of Cu-modified carbon nanofiber (CNF) supports, tailored through electrospinning, in enhancing the electrocatalytic reduction of NO₃ ^– to NH₃. Three variants of CNF supports were synthesized: pristine CNFs, CNFs integrated with carbon nanotubes (CNF/CNTs), and CNFs embedded with titanium dioxide nanoparticles (CNF/TiO₂). Each electrode’s physical and electrochemical properties were analyzed before and after Cu electrodeposition. Notably, the CNF/TiO₂/Cu composites demonstrated a selectivity exceeding 40% for the conversion of NO₃ ^– to NH₃ at neutral pHsignificantly outperforming the CNF/CNT/Cu (2/Cu electrode also exhibited consistent and stable performance over the extended experimental duration (|Q| = 70 C), maintaining NH₃ selectivity rates of over 50%. Tafel analysis and operando Raman spectroscopy suggest that TiO₂ plays an active role in hydrogenating nitrogenous reduction products for enhanced selectivity. This research highlights the importance of electrode-catalyst selection in electrochemical NO₃ ^– reduction and identifies TiO₂-containing electrodes as promising solutions in this domain.

Motility and chemotaxis allow bacteria to migrate from areas that become depleted in energy yielding substrates to more favorable locations, possibly enhancing the biodegradation of pollutants in soil and groundwater. However, in some cases substrates are co‐mingled with one or more toxic solutes that inhibit pollutant degradation and/or microbial growth, and the impacts on motility and chemotaxis represent a knowledge gap. In this study, a one‐dimensional diffusion reaction model is developed and used to simulate dissimilatory biological reduction of nitrate to ammonia (DNRA) presented in a previously published microfluidic gradient chamber (MGC) experiment, where spatial abundances of Shewanella oneidensis MR‐1 cells were recorded over 5 days in a diffusion limited porous media domain as it degraded nitrate and lactate introduced from opposite boundaries, and at one boundary co‐mixed with the antibiotic ciprofloxacin. The model considers S. oneidensis chemotaxis toward nitrate and nitrite, random motility, and growth inhibition by ciprofloxacin. Parameters were adjusted within ranges commonly reported in the literature to obtain results that agreed with the data. Simulation results indicate that motility and not chemotaxis, in combination with inhibition of cell growth by ciprofloxacin, controls the distribution of cells in the toxic region (containing ciprofloxacin) of the MGC. This suggests that cell motility may facilitate nitrate removal in soil and groundwater by enabling microorganisms to migrate toward nitrate contaminated regions with elevated antibiotic concentrations.