ABSTRACT Nanofiltration (NF) and reverse osmosis (RO) membranes are typically highly effective for the rejection of per‐ and polyfluoroalkyl substances (PFAS), but existing studies have primarily focused on a small subset of compounds. Since the properties of individual PFAS vary and the rejection characteristics of NF and RO membranes likewise vary, a model that can predict PFAS rejection by membranes with specific properties would give water treatment practitioners more confidence in knowing that their choice of membrane treatment today would be effective for other PFAS of concern in the future. In this review, the state of the science of NF and RO rejection models is discussed, along with the unique physicochemical aspects of membranes and PFAS that impact membrane rejection. Finally, research is recommended to advance the state of membrane transport modeling by combining mechanistic, statistical, and system‐level modeling methods to achieve predictive models without onerous input requirements.
ABSTRACT Accurate water metering is essential for reducing non‐revenue water (NRW) and supporting sustainable urban water management. This study proposes a data‐driven framework for assessing water meter performance and supporting replacement planning by integrating advanced metering infrastructure (AMI) data with semi‐supervised learning. Using case studies from two Chinese cities, an apparent metering error (AME) metric was developed by combining flow‐dependent error curves with actual usage patterns. A neural network model, trained on 136 mechanical meters and applied to 140,000 residential meters, showed that aging meters systematically under‐register water use (AME: −6% to −2%), mainly because of low‐flow measurement failures and prolonged service duration. Results indicate that optimized replacement strategies can reduce greenhouse gas emissions and operating costs compared with conventional practices. The proposed framework provides a scalable approach for utilities to improve apparent loss assessment and meter replacement planning.
Research on drinking water disinfection continues to find both supporting and non‐supporting evidence that trihalomethanes (THMs) and haloacetic acids (HAAs) are causative agents for adverse human health effects such as bladder cancer and that they are appropriate surrogates for reducing adverse health effects through further regulation. The EPA is revising the microbial/disinfection byproduct (M/DBP) rules to further protect public health; however, the decision to change or add regulations is hindered by uncertainty about the causative agents of DBP‐associated risk and the role of compliance strategies to protect public health. Research conducted since the Stage 2 DBP rule was established helps fill some gaps and outlines lingering uncertainties that should be acknowledged as part of revised rulemaking. This thematic review summarizes regulatory implications of the state of the science in epidemiology, toxicology, occurrence/monitoring, and treatment/compliance, and identifies actions toward meaningful regulatory revisions despite ongoing uncertainty of DBP‐associated human health risk drivers.
The study investigates the impact of chlorine-based disinfectants on the mechanical properties of leaks in water supply networks. Through dynamic and static corrosion experiments, as well as numerical simulations, the research reveals that higher concentrations of disinfectants such as chlorine, monochloramine, and chlorine dioxide significantly affect leak flow rates and the mechanical properties of pipes made from galvanized steel and polypropylene random copolymer. The findings show that the elastic modulus of the leak area follows an "increase-peak-decrease-stabilization" pattern over time, influenced by disinfectant concentration and exposure duration. The study further develops an improved Fixed Area and Variable Area Discharge model, which incorporates these factors, providing a more accurate prediction for leak behavior. The model helps in optimizing water supply network design and leak management. Future research could expand the variety of pipe materials and explore the microscopic interaction between disinfectants and pipe surfaces.
Legionella pneumophila is an opportunistic drinking water microorganism of serious health concern. Anticipated revisions to U.S. EPA's Microbial and Disinfection Byproduct Rules may propose a numeric minimum disinfectant residual-rather than the current "detectable"-in part to better control Legionella in drinking water distribution systems and buildings served. Data to inform distribution system disinfectant residual concentration impacts on L. pneumophila concerns in buildings are scarce. In 2024, the General Services Administration tested water quality, including Legionella, at similar to 8250 federally owned and leased buildings. This study analyzed summary data from similar to 5600 buildings, detailed results from 40 buildings, and corresponding distribution system disinfectant residuals to assess links between residual levels and Legionella occurrence. Utilizing this largest and most nationally representative dataset available to date, findings varied by building and water system, with no clear numeric distribution system residual threshold consistently linked to lower Legionella occurrence in buildings.
Granular activated carbon (GAC) adsorption is commonly used to remove per- and polyfluoroalkyl substances (PFAS) from water. In this study, we evaluated the impact of dissolved organic matter (DOM) concentration and pretreatment on GAC use rates for PFAS removal. Rapid small-scale column tests (RSSCTs) were conducted using a surface water source with a dissolved organic carbon (DOC) concentration of 4.7 mg/L that was subjected to DOM pretreatment methods and groundwater sources with DOC concentrations ranging from < 0.25-4.6 mg/L. DOM pretreatment methods included three full-scale treatment processes-coagulation-flocculation-sedimentation (CFS), CFS followed by ozonation (CFS-O3), and CFS-O3 followed by biological activated carbon (CFS-O3-BAC)-as well as five bench-scale jar test pretreatments: CFS (Jar-CFS), powdered activated carbon (PAC) adsorption, magnetic ion exchange (MIEX), and combinations of PAC or MIEX with CFS (PAC-CFS and MIEX-CFS). GAC use rates decreased dramatically with decreasing DOC concentration. Also, all pretreatment methods lowered GAC use rates, with MIEX-CFS, PAC-CFS, and CFS-O3-BAC being the most effective. Both DOM removal (MIEX-CFS, PAC-CFS) and DOM transformation during ozonation and BAC treatment enhanced GAC performance. GAC use rates to meet U.S. national drinking water standards for PFAS were estimated for a surface water (DOC: 4.7 mg/L) containing six PFAS at concentrations corresponding to the median and 90th percentile values reported by public water systems with detectable PFAS levels in the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5). GAC use rates ranged from 0.01 to 0.34 kg GAC/m3 (0.10-2.8 lb. GAC/1000 gal), depending on the employed DOM pretreatment and initial PFAS concentrations. These findings highlight the importance of DOM concentration and pretreatment on GAC performance for PFAS removal.
Water utilities must balance long-term planning with next year's field operations. This study addresses that challenge with a dual-horizon framework, implemented for the City of Sugar Land, Texas. The framework combines a survival model for capital planning and a machine learning classifier for operational targeting. For the capital planning, anchored Weibull curves are fitted to local break data and aligned to manufacturer life expectations, producing stable hazard estimates, and remaining-life projections. For operations, a feature-enhanced XGBoost model was trained on a historic asset-year panel and validated by predicting future breaks. Its features incorporate joint type normalization, a 25 year break history, and spatial hotspot indicators. When trained through 2023 and tested on 2024, the model achieved 81.4% (area under the curve = 0.934), yielding a manageable list of 2676 pipes from 35,281 assets. Both horizons were integrated within a Geographic Information System, creating spatially clustered candidates for capital improvement programs.
Colloidal gas aphrons (CGAs) have proven successful in separating both long- and short-chain PFAS from water; however, little information is available on the impact of surfactants used for aphron generation. This study assesses the use of five cationic surfactant-generated CGAs in batch experiments to remove PFAS from two site groundwaters. The results found that lauric arginate ethyl ester (LAE), a food-grade surfactant used to generate CGAs, had the best performance, removing over 80% of PFAAs in a single stage. Removal rates were consistent between high- and low-concentration waters, indicating its versatility. The addition of a second stage of treatment improved PFAS removal, particularly for short-chain PFAS, as the first stage predominantly removed long-chain PFAS due to their greater presence in the initial water. Higher salinity and saponins reduced the removal rates due to competitive sorption. Overall, the success of a food-grade surfactant for CGA generation is significant in terms of water treatment.
This study compared a standard Direct Filtration process (DFSTD) with a similar process that incorporated dissolved air flotation into a flocculation basin (DFDAF) to mitigate the effect of particle loading events on filter run time and water quality. Pilot tests evaluated coagulant (0-20 mg/L as FeCl3) and cationic polymer (0-1 mg/L) dosing under varied influent turbidity conditions (0.5-20 NTU) at a fixed DAF recycle ratio (9.5%-10%) and hydraulic loading rate 2.2-2.4 gpm/ft2 (5.4-5.8 m/h). With an influent turbidity of 20 NTU, DFDAF consistently extended filter run times (48-55 h) compared to DFSTD (< 18 h), while meeting filter effluent water quality goals. Polymer addition during DFDAF resulted in a thicker sludge blanket, enhanced solids removal (NTU, Fe, and TSS), organics removal meeting enhanced coagulation requirements (TOC and UV254), and floc/particle accumulation in the upper filter layers rather than throughout the media. Continued development could prove the DFDAF process as feasible for full-scale implementation.
Total organic carbon (TOC) and permanganate chemical oxygen demand (COD Mn ) are the most commonly employed methods to determine the amount of natural organic matter (NOM) in raw and drinking water. However, the usage of COD Mn is questionable due to its variable degrees of oxidation for different types of organics. Our study investigates the ratio of COD Mn to TOC in source waters with diverse NOM compositions characterized by specific UV absorbance (SUVA) and total organic nitrogen (TON). Herein, mountainous water sources with high amounts of humic substances (high SUVA, low TON) exhibit approximately 1.8–2.5 times higher COD Mn values than lowland algae‐laden sources (low SUVA, high TON) despite having the same TOC values. The determination of COD Mn , therefore, can give misleading information about the amount of organics in waters with different NOM character and underestimate the NOM concentration in lowland algae‐laden water sources, which could have implications for drinking water quality.
Manganese (Mn) in drinking water poses aesthetic, health, and operational concerns. One common removal method involves adsorbing soluble Mn(II) onto manganese (III/IV) oxide (MnO x )‐coated media, but this approach typically relies on chemical reagents for surface regeneration. In systems lacking chemical storage, dosing, and containment capacity, this may be impractical. This study demonstrated an alternative regeneration technique using an electrochemical reactor for in situ oxidant production at conditions relevant to drinking water treatment. The reactor generated oxidants, likely free chlorine, and increased the pH of the applied water. Across batch‐scale recirculating, intermittent regeneration, and single‐pass continuous regeneration experiments, electrochemically regenerated MnO x ‐coated media produced ~90% removal of Mn(II), achieving a common treatment goal of 0.02 mg/L. Regeneration was also confirmed by analyzing the average oxidation state of the MnO x surface. Performance depended on several factors, such as raw water Mn, applied voltage, and alkalinity. Although modeling and Mn fractionation suggested limited homogenous oxidation of Mn(II), the formation of some colloidal MnO x may have confounded results in some experimental situations. These findings highlight a promising, reagent‐free strategy for regenerating oxide‐coated media, expanding its applicability for water treatment, especially in isolated systems and point‐of‐use applications.
This study produced a comprehensive drinking water ozone-biofiltration evaluation by assessing performance at a newly commissioned facility with varying hydraulic and ozonation operations. In brief, 30 water quality, operational, and biological parameters were collected at 11 locations throughout the treatment train at least every other week for an entire year. Seasonal and environmental variation seemed to influence treatment performance more than operational changes (i.e., ozone or hydraulic re-rating). However, media adenosine triphosphate (ATP), an indicator of biomass, was sensitive to hydraulic variability. Organic carbon was identified as a reliable performance metric, particularly when total organic carbon (TOC) and dissolved organic carbon (DOC) shared a strong linear relationship. Carboxylic acid removal also served as a useful long-term monitoring tool for assessing ozone-biofilter performance. This study establishes a critical benchmark for capturing the effects of intermittent ozonation, variable hydraulic loading, and seasonal transitions that utilities can utilize to better understand ozone-biofiltration processes in drinking water treatment systems.
Water distribution systems (WDS) are critical infrastructures essential for human well-being and economic prosperity. However, climate change (CC) is increasingly causing variational environmental stress and natural disasters that threaten the integrity of these systems. Without resilient and sustainable WDS, societies will struggle to function effectively. This review article examines the impact of CC on the integrity of WDS, focusing on physical, hydraulic, and water quality aspects. It presents a synthesis of recently published peer-reviewed journal articles that address these dimensions, while acknowledging their synergistic interrelationships. The paper presents adaptation strategies and highlights utility case studies aimed at strengthening the resilience of WDS against the impacts of CC.
This review introduces a novel risk-based management framework for asbestos cement (AC) pipes in drinking water systems, emphasizing maintenance practices and occupational health risks while harmonizing global regulatory and utility practices. Inhalation risks are well established, but WHO guidance indicates negligible risks from ingestion, not warranting regulatory limits. The framework addresses gaps in fiber release monitoring, standardizing protocols to minimize occupational exposure. AC pipes, deployed since the 1920s, persist in many systems despite phase outs. The study highlights deficiencies in fiber release under varying water corrosivity, advocating management of aging infrastructure through GIS tracking, non-destructive testing (NDT), and phased replacement, informed by case studies from Australia and New Zealand. Airborne exposure underscores the need for standardized protocols. Public engagement and evidence-based decisions are essential where immediate replacement is not mandated. This global synthesis integrates regulatory guidance, utility practices, and health data into an actionable framework.
This study provides a comprehensive evaluation of the effectiveness of 280 nm UV LEDs in enhancing chlorine disinfection in natural water sources. The results of this work indicate sequential treatments (UV-chlorine and chlorine-UV) further enhanced the disinfection efficiency of T1 in natural waters, especially at higher UV doses, such as 40 mJ cm-2. The log reduction value for the chlorine-UV sequence reached 6.65, slightly higher than the 6.29 for the UV-chlorine sequence, suggesting that sequencing influences disinfection efficacy at higher fluences. UV LED-enhanced chlorine disinfection did not significantly alter concentrations of THMs and HAAs. Overall, the findings of this study open new avenues for the application of UV LEDs in drinking water disinfection, demonstrating their potential as an alternative to traditional disinfection methods. Future research should further explore the effects of UV-chlorine combined treatments under different water quality conditions to optimize disinfection processes and provide theoretical support for innovation in water treatment technologies.
The combined effects of orthophosphate addition and residence time on chloramine stability, biofilm development, and nitrification potential in drinking water distribution systems (DWDSs) remain unexplored. Most previous studies examined orthophosphate dose under fixed residence time conditions, leaving a gap in understanding how water age modifies these impacts. This study evaluated the effects of orthophosphate and residence time (6/12 days) on monochloramine decay, biofilm growth, and nitrification potential using bench-scale systems. At the 12-day residence time, chloramine decay, biofilm growth, and nitrite accumulation were significantly greater, with orthophosphate amplifying these effects. Biofilm metabolic activity initially increased with orthophosphate before converging with the control, while bulk water metabolic activity remained higher. Genetic profiling revealed microbial community shifts under extended residence time and orthophosphate. These findings demonstrate that orthophosphate, when combined with longer residence times, can accelerate microbial activity and nitrification, highlighting the need to manage both factors to safeguard water quality.
Ten days of continuous torrential rain pushed warm late Spring runoff in deltaic patterns far into Lake Michigan over two subsequent months. Repeated expeditions on the RV Neeskay documented shallow lenses of plankton-enriched water spreading across the surface at 1 km (0.6 mi) per day for months, reaching halfway across the lake, and often running against prevailing currents. Floating cohesively near the surface, a trail of strong, river-harbor-originating biological productivity long outlasted chemical evidence of stormwater efflux in depleted coastal and offshore regions. Only sinking algal populations descended into cooler midwater depths. Previously depauperated siliceous protein- and lipid-rich diatom algae were strongly favored, suggesting a change in water chemistry not readily detected in standard water quality measurements. Initial community outgrowth in near-surface water was evident through turbidity and enhanced biomass as a wave of growth moved offshore, trailed by resurgence of midwater diatom community blooms. Anomalously high surface chloride moved past 25 km 30 days after peak flow. Conductivity is a valuable tool for detection of riverine and harbor water intrusion, as runoff-fed rivers have higher dissolved salts than receiving waters. Endurance of impact indicated that sources far from intakes could pose water quality risks for stable substances. Seasonal temperatures controlled river-lake interactions as Spring runoff warmed by surfaces was buoyant on cool lakewater. Nearshore water treatment intakes thus lay well below the initial surface lens outflows, but biological products would have impinged on them during subsequent sinking. Operational recommendations for predictive event assessment by water producers are provided.
Gel-type anion exchange (AEX) resin performance is impacted by internal mass transfer, which is represented by the solid-phase intraparticle diffusion coefficient (D-s). Importantly, D-s values are required inputs to ion exchange treatment process models but are rarely reported. Previous experiments using gel-type AEX resins exhibited external mass transfer control, preventing D-s estimation for several anions, including perfluoroalkyl substances. To reduce external mass transfer resistance and allow D-s estimation, a stainless-steel centrifugal stirrer device was standardized and validated with nitrate (model anion). Initially, experiments were conducted across mixing speeds (750-1750 rpm) to balance (1) maximizing external mass transfer and (2) preventing flow disturbances. Subsequently, experiments used an optimized speed to estimate nitrate D-s at multiple initial concentrations on three gel-type AEX resins. The developed methodology was useful for determining nitrate D-s and should enable improved Ds estimates for other contaminants, including perfluoroalkyl substances, needed for ion exchange treatment process models.
Manganese (Mn) in drinking water poses aesthetic, health, and operational concerns. One common removal method involves adsorbing soluble Mn(II) onto manganese (III/IV) oxide (MnOx)-coated media, but this approach typically relies on chemical reagents for surface regeneration. In systems lacking chemical storage, dosing, and containment capacity, this may be impractical. This study demonstrated an alternative regeneration technique using an electrochemical reactor for in situ oxidant production at conditions relevant to drinking water treatment. The reactor generated oxidants, likely free chlorine, and increased the pH of the applied water. Across batch-scale recirculating, intermittent regeneration, and single-pass continuous regeneration experiments, electrochemically regenerated MnOx-coated media produced similar to 90% removal of Mn(II), achieving a common treatment goal of 0.02 mg/L. Regeneration was also confirmed by analyzing the average oxidation state of the MnOx surface. Performance depended on several factors, such as raw water Mn, applied voltage, and alkalinity. Although modeling and Mn fractionation suggested limited homogenous oxidation of Mn(II), the formation of some colloidal MnOx may have confounded results in some experimental situations. These findings highlight a promising, reagent-free strategy for regenerating oxide-coated media, expanding its applicability for water treatment, especially in isolated systems and point-of-use applications.
Workforce quality has been a major concern in the water utility sector for decades. While previous research presumes that workforce quality plays an important role in water utility performance, no research to date has explored this relationship empirically. This study represents a first attempt at quantifying the relationship between workforce quality and performance using a dataset containing water utilities in Texas serving over 500 customers, data on Safe Drinking Water Act (SDWA) violations, and water utility operator classes. The results of two negative binomial models, where the dependent variables are the count of SDWA health and SDWA monitoring and reporting violations between 2020 and 2024, show that workforce quality has a substantively large and statistically significant negative effect on SDWA compliance across both types of violations. An additional analysis explores the interactive effect of workforce quality and median income and workforce quality and water source on utility performance.
