AWWA water science最新文献

In 2015, the United States Public Health Service (USPHS) set a target fluoride level for drinking water at 0.7 mg/L to maximize oral health benefits while minimizing any potential harms. Using water fluoridation operational data reported by water systems to the Centers for Disease Control and Prevention (CDC) Water Fluoridation Reporting System (WFRS) during 2016–2021, this study assesses how water systems performed around this target. The authors summarize completeness of data reporting, assess the distribution of monthly average fluoride readings (MAFR) values, and evaluate precision in maintaining fluoride levels. About 69% of adjusting systems provided data, with an average completeness of 63.8% among them. MAFR mean was 0.71 mg/L (SD: 0.20 mg/L), indicating that water systems have primarily adopted the USPHS target. About 76% of MAFRs fell ± 0.1 mg/L around the reporting system point's mean, indicating feasibility in maintaining precision around a target. State programs and water systems could work together to improve data quality and educate operators on best practices.

An established body of research over many decades has identified the importance of both bulk-water and pipe scale surface microenvironment buffering to meet distribution system pH targets and reduce corrosivity toward metallic piping and components. Buffer intensity quantifies the ability of water to resist pH changes, and the greater the buffer intensity, the more resistant the water is to pH changes. To provide a practical tool for exploring buffer intensity, a buffer intensity simulator (BIS) was implemented in open-source R code, incorporating typical chemical species (e.g., carbonate and orthophosphate) that contribute to drinking water buffer intensity along with temperature and ionic strength impacts. The BIS was verified against a parallel spreadsheet implementation and is publicly available at https://github.com/USEPA/BIS. Simulations were conducted to illustrate impacts related to buffer intensity using three practical scenarios: carbonate buffering in drinking waters, temperature impacts, and free ammonia presence from chloramine use and/or source water presence.

The proliferation of harmful cyanobacterial blooms poses a threat to the ecosystem and human health. Microcystins (MCs) are the most frequently detected cyanotoxin released by cyanobacteria, including Microcystis sp. Our study aimed to isolate potential MC-degrading bacteria in Sri Lankan freshwater and determine their possible MC-degradation pathways. Twenty-two morphologically distinct bacterial strains from 13 freshwater bodies were isolated following the enrichment assay. MC-biodegradation assays further confirmed the MC-degradation potential of 21 strains, with Bacillus being the predominant genus. The strain Bacillus altitudinis BL1, isolated from Beira Lake, showed the highest efficiency in Microcystis sp. cell lysis (80%) and MC-degradation (87%). PCR assay results confirmed the absence of mlrABCD genes in all strains, indicating the presence of uncharacterized alternative MC-degradation mechanisms that require further exploration. The dual functions of Microcystis sp. cell lysis and MC-degradation in 21 strains support developing efficient bacteria-mediated strategies to remediate microcystins and eradicate Microcystis-blooms in tropical freshwaters.

Lead in drinking water can lead to serious health effects, including neurodevelopmental issues and heart disease. In December 2023, the U.S. Environmental Protection Agency (EPA) proposed the Lead and Copper Rule Improvements (LCRI), which lower the Lead and Copper Rule's (LCR's) lead action level (AL) from 15 parts per billion (ppb) to 10 ppb and require both first- and fifth-liter sampling and 90th percentile compliance calculations based on the highest lead levels at sites with lead service lines. A methodology for estimating the likelihood a system will have an AL exceedance (ALE) under the LCRI was developed using Michigan LCR compliance data and applied to national LCR compliance data. Findings were compared to EPA's estimates, indicating EPA may have underestimated the percent of smaller systems (serving $��\le �$ 3300) with ALEs and overestimated the percent of larger systems (serving > 10,000), thus underestimating costs and overestimating the benefits of this rulemaking.

A series of paired samples were analyzed to determine if high-precision lead isotopic fingerprinting could help identify the source of lead in plumbing materials and drinking water. Samples were obtained of plumbing materials (lead service lines, copper pipe with lead solder, galvanized materials, and brass fixtures) from water utilities across the United States. Lead samples were taken from the material itself, from scales, and in some cases from associated water. The lead samples were analyzed to determine the ratios of the four stable lead isotopes present. The results enabled the identification of relationships between various components and further aided in the identification of the source of lead found in water and in pipe scales. Isotopic fingerprinting, as demonstrated in this study, could be used to determine if a galvanized line is a galvanized line requiring replacement (GRR) under the Lead and Copper Rule Improvements (USEPA, 2023).

One of the primary ways utilities prevent and address water quality concerns in distribution systems is via regular hydrant flushing, yet rigorous research to evaluate the impact of full-scale flushing programs is limited. This study employed time-series and correlation analyses to evaluate the efficacy of a utility's five-month repeated conventional flushing program to reduce nitrification and improve disinfectant residual concentrations in the distribution system. Short-term water quality improvements during flushes were common across the 16 locations flushed, but lasting improvements were inconsistent as demonstrated by continued nitrification and heterogeneous water quality changes. Flushing frequencies and flow rates may need to be tailored to individual sites, even when similar water quality challenges exist. Water quality monitoring data and related analyses helped to prioritize flush sites, maximize efficiency during and between flushes, and inform decisions to implement additional interventions.

A computational model was developed to investigate the significance of system design and operating conditions on the rejection of neutral, low-MW organics by reverse osmosis for potable reuse. The model demonstrated that the decrease in local rejection as net driving pressure decreases is substantially greater for moderately rejected compounds than for highly rejected compounds. At recovery values less than 70%, the local permeate concentration can exceed the pressure vessel feed concentration for moderately rejected compounds. System-level rejection of moderately rejected compounds is likewise substantially more sensitive to operating conditions than highly rejected compounds. The findings highlight a drawback of relying on rejection results from bench-scale testing that operates at low recovery, which invariably has higher rejection than full-scale systems operating at similar pressure. The analysis demonstrates a trade-off in which the low-pressure, high-recovery operation desired for potable reuse systems can be detrimental to the removal of low-MW neutral organics. The removal of low-MW neutral organics can be improved if organics rejection is explicitly evaluated during the design process.

Water samples from Waiora Drinking Water Treatment Plant in New Zealand were analyzed using excitation-emission matrix fluorescence spectroscopy (EEMS) and parallel factor (PARAFAC) analysis to evaluate organic matter removal across the plant. The assessment also included the individual granular activated carbon (GAC) filters since the filters had varying media ages due to partial media replacement over a 10-month period, presenting a unique assessment opportunity. PARAFAC analysis identified humic-like, tyrosine-protein-like, and tryptophan-protein-like components representing fluorescent dissolved organic matter groups. The humic-like component strongly correlated with total organic carbon (TOC) concentration and removal was significantly influenced by filter media age. However, protein-like components had minimal TOC correlation and were not effectively removed by the overall plant treatment irrespective of filter media age. These findings have implications for disinfection, taste and odor, and bacterial regrowth and require an improved media replacement strategy. Further study of the protein-like components is required.

With increasing interest in using stannous chloride without filtration to achieve hexavalent chromium maximum contaminant level compliance in California, there is new urgency to quantify its effects on water quality and risks to public health manifested in distribution and premise plumbing systems. Accordingly, a 12-week groundwater pilot study was completed using ubiquitous premise plumbing materials under flowing (to waste) and stagnating conditions of hexavalent chromium-containing groundwater following stannous chloride addition without filtration. Results quantified the accumulation and release of chromium and tin, with total chromium concentrations exceeding regulatory or acceptable levels under stagnating conditions. Sediment with elevated chromium, tin, arsenic, and manganese concentrations was also observed. Given these observations would likely occur and worsen over time in distribution systems that cumulatively serve large populations, the use of stannous chloride without filtration represents an unacceptable risk to public health compared to other, more well-established, best available technologies.