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UV-LED technology, utilizing light-emitting diodes (LED) to produce UVC light, has been demonstrated as a promising technology for drinking water applications. The absence of a validated UV-LED reactor or a validation protocol may limit its application. The first full-scale UV-LED280 reactor in the Americas was installed at a municipal well for Legionella pneumophila disinfection. USEPA guidance was used to design validation bench- and full-scale tests with two surrogates (MS2 and T1UV). Full-scale parameters were varied over relevant ranges (893-1000 GPM, 90-99% UVT280, 12-100% power levels, and varying LED280 bank operation) to understand effects on performance. The Calculated Dose Approach successfully generated L. pneumophila-tailored UV intensity setpoints and a validated reduction equivalent dose (RED) monitoring equation. Validated L. pneumophila REDs of 3.7-47 mJ/cm2 were found through the incorporation of an L. pneumophila UV sensitivity factor in the equation, not only reducing RED over/underestimation but also removing the need for UVDGM bias factors. The UV-LED280 REDs exceeded the requirements under a variety of extreme conditions. Although this study successfully demonstrates a UV-LED280 reactor and validation approach, guidance specifically addressing UV-LED would provide clarity and assurance to utilities seeking to implement and receive treatment credit with this promising new technology.
We sequenced 53 Legionella pneumophila isolates from Southern Nevada groundwater, an understudied source despite its use for drinking water. Genomes averaged 3.48 Mbp, and 25 carried plasmids. These data provide a resource for identifying genomic features distinguishing environmental strains from those associated with disease outbreak.
ABSTRACT The IDEXX Legiolert test has been implemented for the quantification of Legionella pneumophila in a variety of potable and non-potable water matrices. For example, through coordination with the state regulatory agency, the Southern Nevada Water Authority (SNWA) has implemented treatment strategies and corresponding L. pneumophila monitoring (via Legiolert) to ensure groundwater quality and public health protection. Because of its specificity to L. pneumophila , confirmation of a positive Legiolert test is often assumed to be unnecessary, although high false positive rates have previously been reported for Legiolert testing of groundwater systems. This study evaluated four confirmation methodologies on liquid media harvested from Legiolert-positive trays: latex agglutination, MALDI-MS, rapid qPCR for the mip and srkA genes, and BCYE plating (±L-cysteine). With the exception of BCYE, these confirmation methods provide results in <24 h, allowing for rapid regulatory and/or public health response. Of 108 presumptive positive analyses of groundwater samples collected in Southern Nevada, only two were ultimately determined to be false positive Legiolert results, although one prompted the shutdown of the corresponding groundwater well. qPCR of the mip gene had the highest L. pneumophila confirmation rate (96%), followed by MALDI-MS (92%), latex agglutination (88%), and BCYE (±L-cysteine) (88%). Although Legiolert alone proved to be effective and relatively accurate in detecting L. pneumophila , confirmation testing yielded valuable supporting information, including serogroup determination and false positive identification ( Stenotrophomonas maltophilia ). Collectively, these data highlight the benefits and drawbacks of various L. pneumophila confirmation methodologies for reporting and decision-making by SNWA and other drinking water utilities. IMPORTANCE In the United States, Legionella pneumophila is the leading cause of drinking water-associated illnesses, hospitalization, and deaths. It is the causative agent of Legionnaires’ disease and the less severe Pontiac Fever. As awareness of L. pneumophila risks increases and monitoring plans are implemented, it is imperative that laboratory analysts, practitioners, and decision-makers understand the limitations of available methods and the value of confirmation in increasing data confidence and informing appropriate actions. Groundwater is commonly used as a drinking water source for public and private systems and generally has less stringent treatment requirements than other sources. Studies have described groundwater as an environmental reservoir for L. pneumophila , but there have also been reports of high false positive rates when monitoring groundwater, particularly when using IDEXX Legiolert. Therefore, the results from this study provide critical knowledge to those monitoring L. pneumophila and using the data for regulatory compliance and/or operational decision-making.
Lake Mead is the primary drinking water source for the Las Vegas Valley and supplies water to 25 million people in the Lower Colorado River Basin. Historically, Lake Mead per- and polyfluoroalkyl substances (PFAS) concentrations have been low; however, decreasing lake levels from drought may result in increased impact from the Las Vegas Wash (LVW) leading to increased PFAS levels. Thus, there is a need to better map Lake Mead PFAS sources. Herein, samples were collected from (1) Lake Mead, rainwater, and snowmelt; (2) wastewater, groundwater, and stormwater sources to the LVW; and (3) sewershed sampling for two wastewater treatment plants (WWTP) in the Las Vegas Valley. Nineteen PFAS were quantified via liquid chromatography tandem mass spectrometry. Additionally, some samples were either analyzed using non-targeted high resolution mass spectrometry or processed using the total oxidizable precursor (TOP) assay method. Total PFAS in the Boulder Basin area of Lake Mead was 3.84 ng/L and was dominated by short-chain perfluorocarboxylic and perfluorosulfonic acids. The Colorado River was the primary source of PFAS to Lake Mead (65% of total PFAS loading) and the LVW was an important secondary source (27%). Total PFAS in precipitation samples were low (0.329–1.51 ng/L) with rainwater dominated by long-chain perfluoroalkyl acids while only perfluorobutane sulfonic acid (PFBS) was detected in snowmelt. Domestic wastewater was the primary WWTP PFAS source due to high residential and domestic flow contributions (63%–94%) and lack of industry, while laundry and PFAS-containing cosmetics are significant PFAS sources in residential wastewater (i.e., estimated mass flow contributions of 11%, 9.3% and 2.2% for household laundry, shampoo and cosmetic cream, respectively). These results provide a better understanding of the PFAS sources to Lake Mead, and similar systems, and will help inform future efforts to manage PFAS flows to this important drinking water source.
This study demonstrates the use of wastewater monitoring for opioids and other high-risk substances on a university campus, intended to inform public health surveillance and response efforts for youth and transitional age youth. Over a 14-week campaign, we collected 54 grab samples from three campus manholes, including one that isolated flows from a student housing complex, and analyzed them for 24 parent compounds and metabolites using LC-MS/MS. Heroin and its metabolite 6-acetylmorphine were among several opioid-related detections, illustrating how campus wastewater monitoring can capture actionable use events for targeted public health interventions. Fentanyl, norfentanyl, and xylazine were consistently below their method reporting limits across all 54 samples, consistent with recent declines in national overdose and wastewater datasets. The highest detection frequencies were associated with methamphetamine (22-50%), amphetamine (39-83%), and a THC metabolite (50-100%). This study also highlights the implications of sample type (grab vs. composite) and day of week for wastewater-based epidemiology (WBE). Considering that the use of opioid-related WBE as an actionable public health surveillance tool is still relatively new, additional case studies are needed to explore the potential of this emerging tool and increase confidence in deploying public health interventions in response to wastewater data.
