This bench-scale study examined the impact of natural organic matter fractions on microcystin-LR adsorption to powdered activated carbons prior to and during a cyanobacterial bloom in a small lake using liquid chromatography-organic carbon detection.

Orthophosphate is commonly added as a corrosion inhibitor in drinking water distribution systems (DWDSs). However, there is limited understanding of the interrelationships between its addition, monochloramine decay, and biofilm growth. Further research is needed to evaluate its potential to accelerate monochloramine decay and promote biofilm development. This study examines the impact of orthophosphate doses (0 to 4 mg PO43-/L) on monochloramine decay and biofilm growth using model distribution systems (MDSs) at a 10-day residence time, fed with phosphorus-limited water. Findings showed that, in addition to expected enhanced microbial growth, biofilm formation potential, and metabolic activity (i.e., carbon utilization), orthophosphate addition also increased monochloramine decay. For instance, biofilm growth increased from 2.9 to 3.2 to 5.3-6.3 log CFU/cm2 between 1 and 4 mg PO43-/L, with the most substantial increase observed between 1 and 2 mg PO43-/L (an increase of >2 log units). Around day 52, changes in metabolic activity, biofilm formation potential, and biofilm growth in MDSs with added orthophosphate suggested a shift in the microbial community from early colonizers to bacteria thriving in biofilms. A correlation between biofilm profiles and monochloramine decay was apparent, with significant positive correlations between total chlorine decay and (i) biofilm HPC (R2 = 0.86, p < 0.001), (ii) biofilm formation potential (R2 = 0.73, p < 0.01), and (iii) metabolic activity (R2 = 0.81, p < 0.001). Higher orthophosphate concentrations (2-4 mg PO43-/L) were linked to greater biofilm growth and monochloramine demand, while 1 mg PO43-/L had minimal impact. Total chlorine decay coefficients ranged from 0.0034-0.004 h-1 (control) to 0.0050-0.0072 h-1 (4 PO43-/L) in the phase of further biofilm development. These findings emphasize that orthophosphate usage in DWDSs needs to balance corrosion control aspects with effects on water quality (e.g., biofilm growth and monochloramine stability).

ABSTRACTClimate change intensifies extreme weather events, potentially posing significant challenges to the quality and quantity of surface water available for drinking water treatment. Quantifying and substantiating a treatment system's capacity and vulnerability in handling a range of raw water conditions is crucial for preparing for future climate scenarios. Concepts like resilience and reliability and related tools have been applied to drinking water treatment plants (DWTPs), but often fail to capture the operational boundaries of treatment processes. Robustness offers a complementary approach, focusing on the range of conditions a system can effectively manage, thereby laying the foundation for improving the system and thus bridging a critical gap in adaptation strategies. This review examines the interconnections between robustness, resilience, reliability, risk, and vulnerability, providing tailored definitions for DWTPs. It also introduces visual diagrams to further illustrate their link and collective role in climate adaptation planning.

Orthophosphate is added into drinking water distribution systems (DWDSs) to reduce lead levels, but its effects on monochloramine decay and microbial activity are underexplored. The main purpose of this study was to determine the effect of orthophosphate addition and increasing monochloramine levels on monochloramine decay in a phosphorus-limited full-scale DWDS using batch tests. The study also evaluated nitrification potential at selected sites in this DWDS after seven years of orthophosphate application, comparing them with findings from a previous study conducted before its introduction. This comparison provides new insights related to orthophosphate's effects in a full-scale DWDS. In the batch test, samples were divided into unprocessed and microbiologically inhibited groups to observe chemical and microbial monochloramine decay over three weeks. The results suggest that orthophosphate may increase microbiological monochloramine decay. Below certain monochloramine levels, defined in previous research as a critical threshold residual (CTR) (0.4-0.7 mg Cl2/L), an accelerated decay rate of monochloramine occurred. The study noted higher CTR values in post-orthophosphate samples, suggesting the need for higher minimum monochloramine levels in the DWDS to prevent accelerated decay when using orthophosphate. Nitrite formation during the batch test was more pronounced in postorthophosphate samples, suggesting that orthophosphate may enhance nitrification potential.

This study investigated the influence of filter media characteristics on manganese (Mn) removal in groundwater biofilters during the start-up phase. Six pilot scale biofilters containing three different granular activated carbons (GAC), two anthracite, and one sand media were run for 133 days to examine their Mn removal performance at a drinking water utility, while also monitoring ATP and bacterial growth as indicators of biological activity. Key findings demonstrate the critical role of media characteristics, especially for GAC media. Initial Mn adsorption on GAC, with its higher surface area, higher macropore volume, and surface charge, promoted physicochemical and biological oxidation, thus contributing to the early onset of Mn removal during the start-up of the GAC biofilters. In contrast, biological processes dominated Mn removal on anthracite and sand biofilters during start-up. As expected, the presence of Mn-oxidizing bacteria was detected in biofilters, and ATP levels were correlated to Mn removal until the biofilters were acclimated, showing the potential of ATP as an acclimation monitoring metric. Once acclimated, all biofilters consistently reduced Mn levels from 60.9 ± 4.5 µg/L to below 5 µg/L (>90 % removal), while concurrently removing iron, thereby highlighting the biofilter's effectiveness at low water temperatures (<15 °C). This study demonstrates the advantage of GAC media for Mn removal in biofilters during start-up in regions with lower water temperatures.

We report on new measurements of elliptic flow (v(2)) of electrons from heavy-flavor hadron decays at mid-rapidity (|y| < 0.8) in Au+Au collisions at vs(NN) = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons (eHF) in Au+Au collisions at vs(NN) = 54.4 GeV exhibit a non-zero v(2) in the transverse momentum (p(T)) region of p(T) < 2 GeV/c with the magnitude comparable to that at vs(NN) = 200 GeV. The measured e(HF) v(2) at 54.4 GeV is also consistent with the expectation of their parent charm hadron v(2) following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at vs(NN) = 54.4 GeV. The measured e(HF) v(2) in Au+Au collisions at vs(NN) = 27 GeV is consistent with zero within large uncertainties. The energy dependence of v(2) for different flavor particles (p, f, D-0/e(HF)) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.(C) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP(3).

Full-scale sampling at 16 facilities illustrated that NDMA precursor concentrations, measured by adding chloramine under Uniform Formation Conditions (NDMA(UFC)), increased across biofiltration at 7 of 16 facilities (by 3-48 ng/L or 12%-296%) but stayed the same or decreased (by up to 5 ng/L or 24%) at the other nine facilities. Increases in NDMA(UFC) concentrations were attributed to both particulate and soluble precursors. Only two facilities had an increase in NDMA(UFC) greater than 10 ng/L. However, NDMA(UFC) concentrations in the biofilter effluent from five facilities exceeded 10 ng/L during one or more sampling events. For these facilities, testing at multiple scales showed that mitigation steps could include pretreatment with ozone (which resulted in overall lower NDMA(UFC)), increased free chlorine contact time prior to ammonia addition, and/or optimized biofilter design and operation.

We report systematic measurements of dielectron (e+e-) invariant-mass Mee spectra at midrapidity in Au + Au collisions at & RADIC;sNN = 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (0.40 < Mee < 0.75 MeV/c2) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the p-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au + Au collisions at midrapidity (|yee| < 1) in the 0-80% centrality bin for each collision energy. The integrated excess yields for 0.4 < Mee < 0.75 GeV/c2, normalized by the charged particle multiplicity at midrapidity, are compared with previously published measure-& RADIC; ments for Au + Au at sNN = 19.6 and 200 GeV. Models that include an in-medium broadening of the p-meson spectral function consistently describe the observed excess. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.

Robustness is the ability of a drinking water treatment plant (DWTP) to achieve the desired finished water quality even during adverse raw water quality events. Increasing the robustness of a DWTP is beneficial for regular operations and especially for extreme weather adaptation. This paper proposes three robustness frameworks: (a) a general framework outlining the main steps and methodology for systematic assessment and improvement of the robustness of a DWTP, (b) a parameter-specific framework applying the general framework to a water quality parameter (WQP), and (c) a plant-specific framework applying the parameter-specific framework to a DWTP. A parameter-specific framework for turbidity is presented using the turbidity robustness index (TRI) for evaluation and applied to a full-scale DWTP in Ontario, Canada. This evaluation was conducted with historical plant data, as well as bench-scale experimental data simulating extremely high-turbidity scenarios. The framework application is capable of identifying (i) less robust processes which are likely to be vulnerable during climate extremes, (ii) operational responses to increasing short-term robustness, and (iii) a critical WQP threshold beyond which capital improvements are necessary. The proposed framework provides insights into the current state of robustness of a DWTP and serves as a tool for climate adaptation planning.

In relativistic heavy-ion collisions, a global spin polarization, P-H, of Lambda and (Lambda) over bar hyperons along the direction of the system angular momentum was discovered and measured across a broad range of collision energies and demonstrated a trend of increasing P-H with decreasing root sNN. A splitting between Lambda and (Lambda) over bar polarization may be possible due to their different magnetic moments in a late-stage magnetic field sustained by the quark-gluon plasma which is formed in the collision. The results presented in this study find no significant splitting at the collision energies of root s(NN) = 19.6 and 27 GeV in the BNL Relativistic Heavy Ion Collisions Beam Energy Scan Phase II using the STAR detector, with an upper limit of P ((Lambda)) over bar - P-Lambda < 0.24% and P<((Lambda))over bar> - P-Lambda < 0.35%, respectively, at a 95% confidence level. We derive an upper limit on the naive extraction of the late-stage magnetic field of B < 9.4 x 10(12) T and B < 1.4 x 10(13) T at root s(NN) = 19.6 and 27 GeV, respectively, although more thorough derivations are needed. Differential measurements of P-H were performed with respect to collision centrality, transverse momentum, and rapidity. With our current acceptance of |y| < 1 and uncertainties, we observe no dependence on transverse momentum and rapidity in this analysis. These results challenge multiple existing model calculations following a variety of different assumptions which have each predicted a strong dependence on rapidity in this collision-energy range.

Suwannee river natural organic matter greatly increased dissolved lead release from galvanic corrosion due to complexation with humic acid-like substances.

The removal of three perfluorinated carboxylic acids (PFCAs)-PFHpA, PFOA, and PFNA-in ultrapure and river water was evaluated using two anion-exchange resins-previously unreported macroporous polystyrenic A-500P and a more widely studied macroporous polyacrylic A-860. Both resins had similar properties, allowing direct comparison of PFCA removal performance between the two resin structures/matrices. This study also presents a new gas chromatography-mass spectrometry (GC/MS) method developed for PFCA analysis in water. In ultrapure water, A-500P exhibited higher removal capacity and faster removal compared to A-860, suggesting greater effectiveness of the polystyrenic structure compared to the polyacrylic structure. In the Grand River water, the target PFCAs were well removed by A-500P but not A-860. However, both resins achieved similarly high overall reductions of dissolved organic carbon (similar to 75%), suggesting, later confirmed in ultrapure water experiments, that inorganic anions (sulfate particularly) were competitors for the A-860 resin. The uncharged styrene and acrylic beads (base materials) of the two tested resins remove PFOA, implying that the dominant removal mechanism involves charge interactions between the negatively and the positively charged anion-exchange functional groups.

Sodium silicate is thought to mitigate lead release via two mechanisms: by increasing pH and by forming a protective silica film. A pilot-scale study using an excavated lead service line (LSL) fed with water from a Great Lakes source was undertaken to: (1) clearly distinguish the pH effect and the silica effect; (2) compare sodium silicate to orthophosphate and pH adjustment; (3) determine the nature of silica accumulation in the pipe scale. The LSL was cut into segments and acclimated with water at pH 7.1. Median dissolved lead was 197 µg/L in the last 8 weeks of acclimation and dropped to 16 µg/L, 54 µg/L, and 85 µg/L following treatment with orthophosphate (dose: 2.6 mg-PO4/L, pH: 7.9), pH adjustment (pH: 7.9) and sodium silicate (dose: 20 mg-SiO2/L, pH: 7.9), respectively. When silica dose was increased from 20 mg-SiO2/L to 25 mg-SiO2/L (pH: 8.1), lead release destabilized and increased (median dissolved lead: 141 µg/L) due to formation of colloidal dispersions composed mainly of lead- and aluminum-rich phases as detected by field flow fractionation used with inductively coupled plasma mass spectrometry. Si was present in the scale at a maximum of 2.2 atomic % after 17 weeks of silica dosing at 20 mg- SiO2/L. Under the conditions tested, sodium silicate did not offer any benefits for reducing lead release from this LSL other than increasing pH. However, sodium silicate resulted in lower levels of biofilm accumulation on pipe walls, as measured by heterotrophic plate counts, when compared to orthophosphate.

A batch test procedure was investigated to provide insight into the microbial contribution to disinfectant decay in drinking water distribution systems using chloramines. A modified method for determining the critical threshold residual (CTR), the intersection point on a semi-log plot between first-order total chlorine fitted decay curves before and after the breakpoint, was developed. Unlike the CTR as originally defined, initial sample conditions were retained rather than artificially raising the monochloramine concentrations. The CTR calculated with this modified method can more easily be applied to distribution system scenarios. In addition, four types of decay curves were identified and could distinguish differences in the microbial contribution to disinfectant residual decay. This study revealed that chloramine decay batch tests should be evaluated based on decay curve type, decay rates, and the CTR value, in addition to the microbial decay factor, which has been used alone in previous studies. The batch test approach and evaluation criteria established here can be used to predict conditions favorable for rapid chloramine decay and nitrification, and that monitoring and control strategies should be implemented.

Pilot-scale granular activated carbon (GAC)-sand and anthracite-sand biofilters were operated in parallel to study the effect of media type and operating conditions on N-nitrosodimethylamine (NDMA) precursor change across the biofilters. Precursor concentrations were assessed by quantifying NDMA formation under simulated distribution system (NDMA(SDS)) conditions in preliminary testing and under uniform formation conditions (NDMA(UFC)) in all subsequent tests. NDMA(SDS) and NDMA(UFC) concentrations in the biofilter influent and effluents were highly variable and typically increased across the biofilters, by as much as 177 ng/L. Backwashing with nonchloraminated filtrate proved to be beneficial in decreasing NDMA(UFC) production compared to chloraminated backwash water, especially for the GAC-sand biofilters. In addition, the GAC-sand biofilters produced significantly lower NDMA(SDS) and NDMA DFc concentrations than the anthracite-sand biofilters. The change in NDMA(SDS) concentration across the biofilters linearly correlated with ATP concentration in both GAC-sand and anthracite-sand biofilters, suggesting that biological activity is important for promoting precursor increase through biofilters. Finally, the fraction of particle-associated NDMA precursors increased across the biofilters, suggesting that biofilm or biofilm-associated compounds are an important contributor to NDMA precursors in the filtrate. Overall, this study provided novel insights into the effects of filter media type and backwashing conditions on NDMA precursor production across biofilters.

Low pressure membranes are attracting attention for their potential to improve secondary effluent quality, but membrane fouling can limit their widespread applicability. In this study, in-line coagulation as pre-treatment to ultrafiltration (UF) was investigated using a bench-scale hollow fiber membrane at a constant flux of 33 L/m2 h. Membrane fouling was monitored by observing change in trans-membrane pressure when the membrane was fed with secondary effluent and in-line coagulated secondary effluent over a 24-h period. The impact of four coagulants at different dosages on reversible and irreversible membrane fouling and permeate quality was studied. It was found that in-line coagulation improved UF performance to varying degrees depending on coagulant type and dosage. Generally, higher reduction of fouling was achieved by increasing coagulant dosage within the 0.5-5.0 mg/L range investigated. Ferric-based coagulants were better than aluminum-based coagulants with respect to improving membrane performance for the secondary effluent investigated, even at low dosages (0.5 mg/L). Further investigations are required to determine how in-line coagulation affects removal of organic compounds through UF membranes.

Microplastics are an emerging issue in water systems, and an understanding of their occurrence and behavior is complicated by a high diversity in physical (i.e., size and shape) and chemical characteristics. To date, there have been limited studies on microplastics in drinking water treatment processes. As the coagulation-flocculationsedimentation (CFS) process is the first step of the particle/colloid removal at many plants, its ability to remove microplastics requires further investigation. By performing alum-CFS bench tests, this study examined the removal of carboxylated polystyrene (PS) microspheres in a wide size range (3, 6, 25, 45, and 90 mu m) in two types of real surface waters (Grand River and Lake Erie water) that are sources for full-scale drinking water treatment plants. Based on experiments using water from the Grand River with a variety of alum doses (10, 20, 30, 40, and 50 mg/L), a higher alum dose generally led to better removal of microspheres smaller than 90 mu m, while an alum dose > 30 mg/L did not substantially improve the removal of particles between 3 and 25 mu m. Further experiments indicated that smaller PS microspheres were more effectively removed in both river (Grand River_Dec 06) and lake water (Lake Erie_Nov 29). For example, with an alum dose of 30 mg/L, 75.6 and 85.2% of the 6-mu m PS microspheres were removed from Grand River and Lake Erie water, respectively. Moreover, the water source significantly (p = 0.0021) affected the removal of PS microspheres, which may have been primarily related to the difference in turbidity. No impacts of PS microspheres were observed on the removal efficiency for turbidity, natural organic matter fractions, or major metal elements by alum-CFS treatment.

Adsorption of the cyanotoxin anatoxin‐a (ANTX) in ultrapure water by five virgin and preloaded granular activated carbons (GACs) was examined using the bottle‐point technique; this article presents baseline adsorption data for ANTX not yet available in the literature. Of the virgin carbons, the two wood‐based carbons adsorbed ANTX more rapidly than the one coconut‐based or two coal‐based carbons. Virgin coal‐based carbons had the greatest equilibrium capacity (1.8–6.9 μg/mg at 1 μg/L aqueous ANTX) compared with their virgin coconut‐ and wood‐based counterparts (1.2 and 0.9–1.0 μg/mg, respectively). GAC preloading via exposure to surface water resulted in kinetic changes and reduced capacity. Preloaded coal‐based carbons adsorbed ANTX faster than the virgin equivalents. At environmentally relevant ANTX concentrations, coal‐based preloaded carbons retained higher equilibrium capacity (1.2 μg/mg) compared with coconut‐ and wood‐based carbons (1.0 and 0.6 μg/mg, respectively). Natural organic matter competition will affect adsorption performance and should be investigated.

Biofiltration has been observed to increase or decrease the concentrations of N-nitrosodimethylamine (NDMA) precursors in the effluents of full-scale drinking water facilities, but these changes have been inconsistent over time. Bench-scale tests comparing biofiltration columns side-by-side exposed to different conditions were employed to characterize factors associated with changes in NDMA precursor concentrations, as measured by application of chloramines under uniform formation conditions (UFC). Side-by-side comparisons of biofiltration media from different facilities fed with water from each of these facilities demonstrated that differences in source water quality were far more important than any original differences in the microbial communities on the biofiltration media for determining whether NDMA precursor concentrations increased, decreased or remained constant across biofilters. Additional tests involving spiking of specific constituents hypothesized to promote increases in NDMA precursor concentrations demonstrated that inorganic nitrogen species associated with nitrification, including ammonia, hydroxylamine and chloramines, and biotransformation of known precursors (i.e., municipal wastewater and the cationic polymer, polyDADMAC) to more potent forms were not important. Biotransformation of uncharacterized components of source waters determined whether NDMA precursor concentrations increased or decreased across biofilters. These uncharacterized source water component concentrations varied temporally and across locations. Where biotransformation of source water precursors increased NDMA precursor concentrations, ∼30–60% of the levels observed in column effluents fed with biofiltration influent water remained associated with the media and could be rinsed therefrom in either the dissolved or particulate form. Ozone pre-treatment significantly reduced NDMA precursor concentrations at one facility, suggesting that pre-oxidation could be an effective technique to mitigate the increase in NDMA precursor concentrations during biofiltration. Biofiltration decreased the concentrations of halogenated disinfection byproduct precursors.