Critical review and rethinking of USEPA secondary standards for maintaining organoleptic quality of drinking water

Optimizing UVA and UVC synergy for effective control of harmful cyanobacterial blooms

Harmful cyanobacterial blooms (HCBs) pose a global ecological threat. Ultraviolet C (UVC) irradiation at 254 nm is a promising method for controlling cyanobacterial proliferation, but the growth suppression is temporary. Resuscitation remains a challenge with UVC application, necessitating alternative strategies for lethal effects. Here, we show synergistic inhibition of Microcystis aeruginosa using ultraviolet A (UVA) pre-irradiation before UVC. We find that low-dosage UVA pre-irradiation (1.5 J cm-2) combined with UVC (0.085 J cm-2) reduces 85% more cell densities compared to UVC alone (0.085 J cm-2) and triggers mazEF-mediated regulated cell death (RCD), which led to cell lysis, while high-dosage UVA pre-irradiations (7.5 and 14.7 J cm-2) increase cell densities by 75-155%. Our oxygen evolution tests and transcriptomic analysis indicate that UVA pre-irradiation damages photosystem I (PSI) and, when combined with UVC-induced PSII damage, synergistically inhibits photosynthesis. However, higher UVA dosages activate the SOS response, facilitating the repair of UVC-induced DNA damage. This study highlights the impact of UVA pre-irradiation on UVC suppression of cyanobacteria and proposes a practical strategy for improved HCBs control.

Control of fluid intake in dehydrated rats and evolution of sodium appetite

The objective of the present work is to examine from a new perspective the existence of causal factors not predicted by the classical theory that thirst and sodium appetite are two distinct motivations. For example, we ask why water deprivation induces sodium appetite, thirst is not "water appetite", and intracellular dehydration potentially causes sodium appetite. Contrary to the classical theory, we suggest that thirst first, and sodium appetite second, designate a temporal sequence underlying the same motivation. The single motivation becomes an "intervenient variable" a concept borrowed from the literature, fully explained in the text, between causes of dehydration (extracellular, intracellular, or both together), and respective behavioral responses subserved by hindbrain-dependent inhibition (e.g., lateral parabrachial nucleus) and forebrain facilitation (e.g., angiotensin II). A corollary is homology between rat sodium appetite and marine teleost thirst-like motivation that we name "protodipsia". The homology argument rests on similarities between behavior (salty water intake) and respective neuroanatomical as well as functional mechanisms. Tetrapod origin in a marine environment provides additional support for the homology. The single motivation hypothesis is also consistent with ingestive behaviors in nature given similarities (e.g., thirst producing brackish water intake) between the behavior of the laboratory rat and wild animals, rodents included. The hypotheses of single motivation and homology might explain why hyperosmotic rats, or eventually any other hyperosmotic tetrapod, shows paradoxical signs of sodium appetite. They might also explain how ingestive behaviors determined by dehydration and subserved by hindbrain inhibitory mechanisms contributed to tetrapod transition from sea to land.

Enhancing water quality monitoring through the integration of deep learning neural networks and fuzzy method

The escalating growth of the global population has led to degraded water quality, particularly in seawater environments. Water quality monitoring is crucial to understanding the dynamic changes and implementing effective management strategies. In this study, water samples from the southwestern regions of Iran were spatially analyzed in a GIS environment using geostatistical methods. Subsequently, a water quality map was generated employing large and small fuzzy membership functions. Additionally, advanced prediction models using neural networks were employed to forecast future water pollution trends. Fuzzy method results indicated higher pollution levels in the northern regions of the study area compared to the southern parts. Furthermore, the water quality prediction models demonstrated that the LSTM model exhibited superior predictive performance (R2 = 0.93, RMSE = 0.007). The findings also underscore the impact of urbanization, power plant construction (2010 to 2020), and inadequate urban wastewater management on water pollution in the studied region.

Qualitative and quantitative water investigation of Erin-Ijesha (Olumirin) Waterfall, Erin-Ijesha, Nigeria

This study focused on the assessment of water quality in Erin-Ijesha (Olumirin) Waterfall, a prominent natural attraction in southwestern Nigeria. The physiochemical parameters, heavy metal concentrations, and bacteriological characteristics were examined in the upstream, midstream, and downstream sections, to ensure the resource quality and safety from harm. The results revealed notable variations in water quality. The pH, Total Dissolved Solids, Electrical Conductivity, and Temperature were highest in the midstream while Total Hardness, Alkalinity, salinity, Chloride, sulphate, Phosphate, Nitrate, Calcium, and Magnesium were highest in the downstream section. The physicochemical parameters were within the acceptable limits of World Health Organization (WHO), United States Environmental Protection Agency (USEPA), and the Standard Organization of Nigeria (SON) standards, except the pH, temperature, and Total Hardness were higher than the acceptable limits of 6.5-8.5, <25 °C or >50 °C and 50 mg/L in all the sections. Iron was above the WHO, USEPA, and SON permissible limits of 3.0 mg/L in all the sections of the river while there was no indication of copper, lead, and cadmium. Bacterial contamination, particularly the presence of E. coli, exceeded recommended safety thresholds. The Total Bacterial Count (TBC) exceeded safety limits by 0.1 million cfu/mL in the downstream. The mean of the parameters was higher in some instances, and sometimes lower than the values in the various sections of the river. A significant relationship existed between most physical, chemical, and bacteriological parameters at p < 0.01. The appraisal of water quality in Olumirin Waterfalls emphasizes the need for proactive measures to ensure water safety, preserve ecosystems, and promote responsible water resource management.

Distribution of inorganic compositions of Japanese tap water: a nationwide survey in 2019-2024

A nationwide survey of inorganic components of tap water all over Japan was conducted from 2019 to 2024. In this survey, 1564 tap water samples were collected, and an additional 194 tap water samples were collected from 33 other countries. The water samples were analyzed for 27 dissolved inorganic components, with a primary focus on the distribution of major and trace components, including Ca, Mg, K, Na, Cl-, NO3-, SO42-, total-hardness, Al, Fe, Cu, Mn, and Zn. The Japanese tap water hardness was 50.5 ± 30.2 (± 1σ SD) mg/L, classified as soft water according to the World Health Organization (WHO) classification. The average content of each major component in Japanese tap water tended to be lower than those in other countries. Furthermore, Piper trilinear diagrams were used to categorize Japanese tap water types. The dominating water types were the Ca-HCO3 and mixed types, which had a nationwide distribution. Japanese tap water generally complied with Japanese and WHO drinking water criteria, with only 1% (17/1564 sites) of the samples exceeding water quality standards. Observations of water quality changes for 2 years at three household faucets revealed that fluctuations in major components and trace metals (Al, Fe, Cu, Mn, and Zn) varied in different patterns. This suggests that the behavior of trace metal elements is influenced by local infrastructure, such as supply pipes, distinct from the variability in source water quality.

Simultaneous removal of nutrients and biological pollutants via specialty absorbents in a water filtration system for watershed remediation

To investigate watershed remediation within a Total Maximum Daily Load program, this study examined the field-scale filtration performance of two specialty absorbents. The goal was to simultaneously remove nutrients and biological pollutants along Canal 23 (C-23) in the St. Lucie River Basin, Florida. The filtration system installed in the C-23 river corridor was equipped with either clay-perlite with sand sorption media (CPS) or zero-valent iron and perlite green environmental media (ZIPGEM). Both media were formulated with varying combinations of sand, clay, perlite, and/or recycled iron based on distinct recipes. In comparison with CPS, ZIPGEM exhibited higher average removal percentages for nutrients. Findings indicated that ZIPGEM could remove total nitrogen up to 49.3%, total Kjeldahl nitrogen up to 67.1%, dissolved organic nitrogen (DON) up to 72.9%, total phosphorus up to 79.6%, and orthophosphate up to 73.2%. Both ZIPGEM and CPS demonstrated similar efficiency in eliminating biological pollutants, such as E. coli (both media exhibiting an 80% removal percentage) and chlorophyll a (both media achieving approximately 95% removal). Seasonality effects were also evident in nutrient removal efficiencies, particularly in the case of ammonia nitrogen; the negative removal efficiency of ammonia nitrogen from the fifth sampling event could be attributed to processes such as photochemical ammonification, microbial transformation, and mineralization of DON in wet seasons. Overall, ZIPGEM demonstrated a more stable nutrient removal efficiency than CPS in the phase of seasonal changes.

Simultaneous time-resolved inorganic haloamine measurements enable analysis of disinfectant degradation kinetics and by-product formation

We demonstrate the application of proton transfer time-of-flight mass spectrometry (PTR-TOF-MS) in monitoring the kinetics of disinfectant decay in water with a sensitivity one to three orders of magnitude greater than other analytical methods. Chemical disinfection inactivates pathogens during water treatment and prevents regrowth as water is conveyed in distribution system pipes, but it also causes formation of toxic disinfection by-products. Analytical limits have hindered kinetic models, which aid in ensuring water quality and protecting public health by predicting disinfection by-products formation. PTR-TOF-MS, designed for measuring gas phase concentrations of organic compounds, was able to simultaneously monitor aqueous concentrations of five inorganic haloamines relevant to chloramine disinfection under drinking water relevant concentrations. This novel application to aqueous analytes opens a new range of applications for PTR-TOF-MS.

The fluorosis conundrum: bridging the gap between science and public health

Fluorosis, a chronic condition brought on by excessive fluoride ingestion which, has drawn much scientific attention and public health concern. It is a complex and multifaceted issue that affects millions of people worldwide. Despite decades of scientific research elucidating the causes, mechanisms, and prevention strategies for fluorosis, there remains a significant gap between scientific understanding and public health implementation. While the scientific community has made significant strides in understanding the etiology and prevention of fluorosis, effectively translating this knowledge into public health policies and practices remains challenging. This review explores the gap between scientific research on fluorosis and its practical implementation in public health initiatives. It suggests developing evidence-based guidelines for fluoride exposure and recommends comprehensive educational campaigns targeting the public and healthcare providers. Furthermore, it emphasizes the need for further research to fill the existing knowledge gaps and promote evidence-based decision-making. By fostering collaboration, communication, and evidence-based practices, policymakers, healthcare professionals, and the public can work together to implement preventive measures and mitigate the burden of fluorosis on affected communities. This review highlighted several vital strategies to bridge the gap between science and public health in the context of fluorosis. It emphasizes the importance of translating scientific evidence into actionable guidelines, raising public awareness about fluoride consumption, and promoting preventive measures at individual and community levels.

Aquaculture activities influencing the generation of geosmin and 2-methylisoborneol: a case study in the aquaculture regions of Hongze Lake, China

Contamination by odor substances such as geosmin (GSM) and 2-methylisoborneol (2-MIB) was examined in the cultured water from aquaculture farming in the region of the Hongze Lake in 2022, and some factors influencing residual levels of them in the water were analyzed. Geographically, high concentrations of GSM were located mainly in the north and northeast culture areas of the lake, while those of 2-MIB were found in the northeast and southwest. Analysis of the water in the enclosure culture revealed significant differences in the concentrations of GSM and 2-MIB among the cultured species. The mean concentrations of GSM in culture water were ranked in the order: crab > the four major Chinese carps > silver and bighead carp, and silver and bighead carp > crab > the four major Chinese carps for 2-MIB. The concentration of GSM was significantly higher at 38.99 ± 18.93 ng/L in crab culture water compared to other fish culture water. Significant differences were observed in GSM concentrations between crab enclosure culture and pond culture, while 2-MIB levels were comparable. These findings suggest that cultural management practices significantly affect the generation of odor substances. The taste and odor (T&O) assessment revealed that the residual levels of GSM and 2-MIB in most samples were below the odor threshold concentrations (OTCs), although high levels of GSM and 2-MIB in all water bodies were at 30.9% and 27.5%, respectively. Compared with the corresponding data from other places and the regulation guidelines of Japan, USA, and China, the region in the Hongze Lake is generally classified as a slightly T&O area, capable of supporting the aquaculture production scale.

Elevated radon level in drinking water of Ajodhya Hill Area of West Bengal, India: probable health impact on lung and stomach

A screening survey has been carried out to measure the radon concentration in drinking water at various locations of Ajodhya hill and surrounding areas in Purulia district of West Bengal, India, using AlphaGUARD radon monitor. The obtained 222Rn concentration in ground water varies from 5.71 ± 0.29 to 579.47 ± 23.18 Bq/l with an average of 110.00 ± 6.61 Bq/l. Comparison between our results with the internationally recommended reference levels reveals that drinking of water from the majority of these tube-wells can pose significant health risks to the local people. Correlation study indicates that tube-well depth has significant influence on the radon level in water samples. Using 60 l/yr and 1642.50 l/yr water consumption estimated annual effective radon doses for most of the samples (almost 70% and 96%, respectively) are high compared to the World Health Organization (WHO) and the European Union (EU) Commission prescribed reference dose limit of 100 μSv/yr. Also, the evaluated Excess Lifetime Cancer Risk (ELCR) values associated with the tube-wells are showing serious threat to the health of the locals.The primary goal of this work is to develop a radon profile map of this area and to find out the possible reasons behind the elevated radon level in ground water. This type of work may play a very crucial role to aware the locals in perspective of human exposure to radon. The local health officials and the water quality regulators of India are requested to take necessary steps for protecting the local people from water radon hazard.

Nitrogen-sparging assisted anoxic biological drinking water treatment system

Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen-sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

Consumer quality management for beverage food products: analyzing consumer’ perceptions toward repurchase intention

Purpose

The research on consumerism has been dramatically rising in recent decades. However, in the food industry, little research has been empirically conducted in the beverage industry. This research empirically tests the consequences of consumer perceptions: perceived price (PPR), perceived quality (PQ), perceived packaging (PPG) and perceived taste (PT) on repurchase intention (RI) particularly; it unveils the consumer attributes, e.g. gender, age and ethnicity between consumer perceptions and RI of the consumers.

Design/methodology/approach

The data were collected from 403 consumers of the beverage industry (e.g. Nestle, Mitchell's Fruit Farms, Murree Brewery and OMORE) in Pakistan. The researchers used online survey questionnaires followed by a cross-sectional approach because data collection physically was not possible due to COVID-19.

Findings

Data were analyzed by Smart partial least square structural equation modeling (PLS-SEM) 3.3.3, and the results supported the significant influence of consumer perceptions separately, e.g. PPR, PQ, PPG and PT on RI. Additionally, gender, age and ethnicity were found to have a moderating role between consumer perceptions and RI, so, the truth of having consumer attributes has been revealed.

Practical implications

The managers of beverage industries should provide ethical and operational strategies to tackle consumer's problems based on cultural norms. Furthermore, they should make sensible measures for the quality branding of the beverage products. In this way, the consumers will have a better experience of quality, price, taste and packaging, in turn, to RI.

Originality/value

This research targeted the beverage industry that needs facts and figures based on consumer attributes, e.g. age, gender and ethnicity. This research also disclosed the behaviors of consumers according to their gender, age and area of residence.

Identifying Geogenic and Anthropogenic Aluminum Pollution on Different Spatial Distributions and Removal of Natural Waters and Soil in Çanakkale, Turkey

The Çanakkale-Kirazlı region (Turkey) is enriched with minerals, especially aluminum (Al), which dangerously get transported into aquatic media due to several mining and geological activities in recent years. In this study, Al and other potentially toxic metals (PTMs) including B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, and Zn, in both water and soil samples, were measured for quality determination. Selected metals were also analyzed by the enrichment factor (EF), the geoaccumulation index (I _geo), the contamination factor (CF), and the pollution load index (PLI) to evaluate both water and soil pollution geogenically or anthropogenically. Also, the metals were clustered to support the pollution source with Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA). Forty-five natural water samples and 12 soil samples were collected spatially. To perform pollution assessment, two fundamental treatment processes to remove Al pollution from the sample including the highest Al concentration (38.38 mg/L) in water were applied: (1) precipitation with pH adjustment and (2) removal with ion exchange. The pH values of water samples were changed in the range of 3-9 to test the dissolution of Al. The results demonstrated that the study area was mostly under the influence of geogenic aluminum pollution.

Enhanced visible light assisted peroxymonosulfate process by biochar in-situ enriched with γ-Fe2O3 for p-chlorophenol degradation: performance, mechanism and DFT calculation

In this study, a novel γ-Fe₂O₃/biochar (BF_γ) composite by a plant in-situ enrichment and one-step pyrolysis strategy was prepared, which was applied as a photocatalyst to activate peroxymonosulfate (PMS) for the degradation of p-chlorophenol (4-CP) under visible light irradiation (BF_γ/PMS/Vis) system. The characterization results exhibited that γ-Fe₂O₃ with localized carbon doping was evenly embedded in biochar during the pyrolysis. BF_γ exhibited better photoresponse properties than biochar (BC) and γ-Fe₂O₃. The removal efficiency of this system for 4-CP reached 96.41% under optimal conditions. This system showed high removal efficiency with a wide pH range (3.0-13.0) and under conditions of different organic pollutants. It also showed strong resistance to interference with co-existing inorganic ions and humic acid (HA). Electron paramagnetic resonance (EPR) and radical scavenging experiments revealed that the reactive oxygen species (ROS) in this system included SO₄^-·, ·OH, ·O₂^- and ¹O₂. The density functional theoretical (DFT) calculations further revealed the promotion of localized carbon doping in γ-Fe₂O₃ on electron transfer and photoresponse, including C-O bond (d=1.29 Å), C-Fe bond (d=1.80 Å) and band gap value (E_gap < 0.72 eV). This study provides new insights into constructing environmentally-friendly catalysts and the possibility of the solid waste recycling for other wetland plants.

Characterization of Metallic Off-Flavors in Drinking Water: Health, Consumption, and Sensory Perception

Characterization of taste- and flavor-producing metals, namely iron and copper, in drinking water is a multifaceted subject. Both metals are essential nutrients, can be toxic, and are known to produce unpleasant tastes and flavor sensations in drinking water. Ingestion of trace metal contaminants through drinking water is a probable source of human exposure. Biochemical mechanisms of metallic flavor perception have been previously described; however, less is known about how variations in salivary constituents might impact individuals' sensitivities to metallic flavors and beverage consumption behaviors. This research presents findings from in vitro experiments, using artificial human saliva, to better understand the role of salivary lipids and proteins on metallic flavor production as measured by biomarkers of metal-induced oxidative stress. The results indicate that metal-induced lipid oxidation, as measured by thiobarbituric acid reactive substances (TBARS), is dominated by salivary proteins, is slightly inhibited in the presence of salivary nitrite, and is detectable by the TBARS method at and above respective concentrations of 9 µM (0.5 mg/L) and 90 µM (5 mg/L), which are both above the aesthetic standards for iron (0.3 mg/L) and copper (1.0 mg/L) in drinking water. Preliminary study with human subjects indicated that reduction in metallic flavor sensitivity, as measured by the best estimate flavor threshold for ferrous iron among 33 healthy adults aged 19-84 years old (22 females), corresponded with reduced drinking water consumption and increased caloric beverage intake among older subjects (>60 years), as determined by a validated self-reported beverage intake questionnaire. These findings provide insights for further research to examine how salivary constituents can impact humans' sensory abilities in detecting metallic off-flavors in water, and how reduced metallic flavor sensitivity may influence beverage choices and drinking water consumption.

Can Common Pool Resource Theory Catalyze Stakeholder-Driven Solutions to the Freshwater Salinization Syndrome?

Freshwater salinity is rising across many regions of the United States as well as globally, a phenomenon called the freshwater salinization syndrome (FSS). The FSS mobilizes organic carbon, nutrients, heavy metals, and other contaminants sequestered in soils and freshwater sediments, alters the structures and functions of soils, streams, and riparian ecosystems, threatens drinking water supplies, and undermines progress toward many of the United Nations Sustainable Development Goals. There is an urgent need to leverage the current understanding of salinization's causes and consequences─in partnership with engineers, social scientists, policymakers, and other stakeholders─into locally tailored approaches for balancing our nation's salt budget. In this feature, we propose that the FSS can be understood as a common pool resource problem and explore Nobel Laureate Elinor Ostrom's social-ecological systems framework as an approach for identifying the conditions under which local actors may work collectively to manage the FSS in the absence of top-down regulatory controls. We adopt as a case study rising sodium concentrations in the Occoquan Reservoir, a critical water supply for up to one million residents in Northern Virginia (USA), to illustrate emerging impacts, underlying causes, possible solutions, and critical research needs.

Chloramine Prevents Manganese Accumulation in Drinking Water Pipes Compared to Free Chlorine by Simultaneously Inhibiting Abiotic and Biotic Mn(II) Oxidation

The oxidation of residual Mn(II) in finished water can lead to MnO_x deposit formation in drinking water pipes. Previous work has illustrated that microbes readily cause Mn deposit build-up in nondisinfected pipes. Here, we investigated how disinfectant type and dose affected Mn(II) oxidation and MnO_x accumulation through long-term pipe experiments using water produced by a full-scale water treatment plant. The results showed that Mn(II) oxidation initiated quickly in the new pipes chlorinated with 1.0 mg/L free chlorine. After 130 days of MnO_x accumulation, 100 μg/L Mn(II) in water could drop to 1.0 μg/L within 1.5 h, resulting from autocatalytic Mn(II) oxidation and Mn(II) adsorption by MnO_x deposits accumulated on pipe walls. In contrast to chlorination, chloramination (1.0 mg/L Cl₂) caused almost no MnO_x accumulation during the entire study period. The underlying mechanism was probably that monochloramine inhibited microbial Mn(II) oxidation without causing significant abiotic Mn(II) oxidation like free chlorine. A low free chlorine dose (0.3 mg/L) also reduced Mn deposit formation by mass but to a lesser extent than chloramination. After disinfection (chlorination or chloramination) was discontinued for days, biotic Mn(II) oxidation occurred, and this process was inhibited again once disinfection was resumed. In addition, Fe(III) of 200 μg/L enhanced the stability of MnO_x accumulated on pipe surfaces, while humic acid induced MnO_x deposit resuspension. Overall, this study highlighted the regulating role of disinfectants in MnO_x formation and provided insights into developing appropriate disinfection strategies for Mn deposit control.

Color removal for large-scale interbasin water transfer: Experimental comparison of five sorption media

The increasing needs of drinking water due to population growth requires seeking for new tap water sources. However, these large-scale tap water sources are oftentimes abundant with dissolved natural organic matter (NOM), such as tannic acid issue causing color in water. If not removed at the source locations beforehand, NOM would impact coagulation and flocculation unit, and/or become precursors to prompt the production of disinfectant by-products after chlorination in drinking water treatment. This study focuses on developing and testing a suite of cost-effective, scalable, adaptable, and sustainable sorption media that can be implemented near the source locations of tap water as a pretreatment option to remove color for a long-distance interbasin transfer. Within the five tested sorption media, a media recipe of Zero-valent-Iron and Perlite based Green Sorption Media (ZIPGEM) with ingredients of 85% sand, 5% clay, 6% zero-valent-iron (ZVI) and 4% perlite by volume stood out as the best option for color removal. Findings showed that ZIPGEM can maintain a color removal of ∼77% for about 14,080 min, maintaining the effluent concentration below 40 Pt-Co units given the influent condition of 175 ± 10 Pt-Co units. A recovery on the adsorption capacity of ZIPGEM was observed around 40,000 min due to synergetic effects among several different ingredients of recycled ZVI, clay, sand, and perlites. ZIPGEM can be applied to industrial wastewater treatment for dye removal as well.

Resin-Mediated pH Control of Metal-Loaded Ligand Exchangers for Selective Nitrogen Recovery from Wastewaters

Highly selective separation materials that recover total ammonia nitrogen (i.e., ammonia plus ammonium, or TAN) from wastewaters as a pure product can supplement energy-intensive ammonia production and incentivize pollution mitigation. We recently demonstrated that commercial acrylate cation exchange polymer resins loaded with transition metal cations, or metal-loaded ligand exchangers, can recover TAN from wastewater with high selectivity (TAN/K+ equilibrium selectivity of 10.1) via metal-ammine bond formation. However, the TAN adsorption efficiency required further improvement (35%), and the optimal concentration and pH ranges were limited by both low ammonia fractions and an insufficiently strong resin carboxylate-metal bond that caused metal elution. To overcome these deficiencies, we used a zinc-acrylate ligand exchange resin and a tertiary amine acrylic weak base resin (pH buffer resin) together to achieve resin-mediated pH control for optimal adsorption conditions. The high buffer capacity around pH 9 facilitated gains in the adsorbed TAN per ligand resin mass that enhanced the TAN adsorption efficiency to greater than 90%, and constrained zinc elution (below 0.01% up to 1 M TAN) because of decreased ammonia competition for zinc-carboxylate bonds. During TAN recovery, resin-mediated pH buffering facilitated recovery of greater than 99% of adsorbed TAN with 0.2% zinc elution, holding the pH low enough to favor ammonium but high enough to prevent carboxylate protonation. For selective ion separation, solid phase buffers outperform aqueous buffers because the initial solution pH, the buffering capacity, and the ion purity can be independently controlled. Finally, because preserving the resin-zinc bond is crucial to sustained ligand exchange performance, the properties of an ideal ligand resin functional group were investigated to improve the properties beyond those of carboxylate. Ultimately, ligand exchange adsorbents combined with solid pH buffers can advance the selective recovery of nitrogen and potentially other solutes from wastewaters.

A survey of monitoring tap water hardness in Japan and its distribution patterns

We conducted a comprehensive overall tap water hardness assessment for Japan. Tap water was collected from 665 points throughout Japan, and its standing position was quantitatively clarified by prefecture. The mean and median hardness of tap water in Japan was 48.9 ± 25.8 (1σ SD) and 46.0 mg/L, respectively. Compared with 27 other countries, Japan exhibited soft water with low-mineral content. Water hardness tended to be high in the Kanto region and low in the Hokkaido and Tohoku regions. The impact of the distribution system's water pipes on tap water hardness is discussed using a unified index to evaluate variations in hardness from raw to tap water. A comparison of the variations in hardness showed that hardness variations from raw to purified water and from purified to tap water exhibited a 20% variation range. Furthermore, tap water hardness and its fluctuations in any region of Japan were found to be caused by raw water hardness. It was demonstrated that the distribution pipe system had no large impacts on water hardness.

A critical review on geosmin and 2-methylisoborneol in water: sources, effects, detection, and removal techniques

The exposure to geosmin (GSM) and 2-methylisoborneol (2-MIB) in water has caused a negative impact on product reputation and customer distrust. The occurrence of these compounds and their metabolites during drinking water treatment processes has caused different health challenges. Conventional treatment techniques such as coagulation, sedimentation, filtration, and chlorination employed in removing these two commonest taste and odor compounds (GSM and 2-MIB) were found to be ineffective and inherent shortcomings. The removal of GSM and MIB were found to be effective using combination of activated carbon and ozonation; however, high treatment cost associated with ozonation technique and poor regeneration efficiency of activated carbon constitute serious setback to the combined system. Other shortcoming of the activated carbon adsorption and ozonation include low adsorption efficiency due to the presence of natural organic matter and humic acid. In light of this background, the review is focused on the sources, effects, environmental pathways, detection, and removal techniques of 2-MIB and GSM from aqueous media. Although advanced oxidation processes (AOPs) were found to be promising to remove the two compounds from water but accompanied with different challenges. Herein, to fill the knowledge gap analysis on these algal metabolites (GSM and 2-MIB), the integration of treatment processes vis-a-viz combination of one or more AOPs with other conventional methods are considered logical to remove these odorous compounds and hence could improve overall water quality.

Identification of MIB producers and odor risk assessment using routine data: A case study of an estuary drinking water reservoir

Identification of MIB(2-methylisoborneol)-producing cyanobacteria in source water has been a big challenge for reservoir authorities because it normally requires isolation of cyanobacteria strains. Here, a protocol based on Pearson's product moment correlation analysis combined with standardized data treatment and expert judgement was developed to sort out the MIB producer(s), mainly based on routine monitoring data from an estuary drinking water reservoir in the Yangtze River, China, and a risk model using quantile regressions was established to evaluate the risk of MIB occurrences. This reservoir has suffered from MIB problems in summer since 2011. Among 323 phytoplankton species, Planktothrix was judged to be the MIB producer in this reservoir because it exhibited the highest correlation coefficient (R = 0.60) as well as the lowest false positive-ratio (FP% = 0) and false-negative rate (FN% = 14). The low false-positive rate is particularly important, since MIB should not detected without detection of the producer. A high light extinction coefficient (k=5.57±2.48 m^-1) attributed to high turbidity loading in the river water lowered the subsurface water light intensity, which could protect the low irradiance Planktothrix from excessive solar radiation, and allow them to grow throughout the summer. The risk model shows that the probability of suffering unacceptable MIB concentrations (>15 ng L^-1) in water is as high as 90% if the cell density of Planktothrix is >609.0 cell mL^-1, while the risk will be significantly reduced to 50% and 10% at cell densities of 37.5 cell mL^-1 and 9.6 cell mL^-1, respectively. The approach developed in this study, including the protocol for identification of potential producers and the risk model, could provide a reference case for the management of source water suffering from MIB problems using routine monitoring data.

Adsorption of Mn2+ from Aqueous Solution Using Manganese Oxide-Coated Hollow Polymethylmethacrylate Microspheres (MHPM)

Results of investigation on adsorption of Mn2+ from aqueous solution by manganese oxide-coated hollow polymethylmethacrylate microspheres (MHPM) are reported here. This is the first report on Mn-coated hollow polymer as a substitute for widely used materials like green sand or MN-coated sand. Hollow polymethylmethacrylate (HPM) was prepared by using a literature procedure. Manganese oxide (MnO) was coated on the surface of HPM (MHPM) by using the electroless plating technique. The HPM and MHPM were characterized by using optical microscopy (OM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Optical and scanning micrographs were used to monitor the surface properties of the coated layer which revealed the presence of MnO on the surface of HPM. TGA showed the presence of 4-5% of MnO in MHPM. Adsorption isotherm studies were carried out as a function of pH, initial ion concentration, and contact time, to determine the adsorption efficiency for removal of Mn2+ from contaminated water by the synthesized MHPM. The isotherm results showed that the maximum adsorption capacity of MnO-coated HPM to remove manganese contaminants from water is 8.373 mg/g. The obtained ${\text{R}}^2$ values of Langmuir isotherm and Freundlich isotherm models were 1 and 0.87, respectively. Therefore, ${\text{R}}^2$ magnitude confirmed that the Langmuir model is best suited for Mn2+ adsorption by a monolayer of MHPM adsorbent. The material developed shows higher adsorption capacity even at a higher concentration of solute ions, which is not usually observed with similar materials of this kind. Overall findings indicate that MHPM is a very potential lightweight adsorbent for removal of Mn2+ from the aqueous solution because of its low density and high surface area.

Modeling the Formation and Propagation of 2,4,6-trichloroanisole, a Dominant Taste and Odor Compound, in Water Distribution Systems

2,4,6-trichloroanisole (2,4,6-TCA) formation is often reported as a cause of taste and odor (T&O) problems in water distribution systems (WDSs). The biosynthesis via microbial O-methylation of 2,4,6-trichlorophenol (2,4,6-TCP) is the dominant formation pathway in distribution pipes. This paper attempted to utilize the reported data on the microbial O-methylation process to formulate deterministic kinetic models for explaining 2,4,6-TCA formation dynamics in WDSs. The pipe material’s critical role in stimulating O-methyltransferases enzymatic activity and regulating 2,4,6-TCP bioconversion in water was established. The kinetic expressions formulated were later applied to develop a novel EPANET-MSX-based multi-species reactive-transport (MSRT) model. The effects of operating conditions and temperature in directing the microbiological, chemical, and organoleptic quality variations in WDSs were analyzed using the MSRT model on two benchmark systems. The simulation results specified chlorine application’s implication in maintaining 2,4,6-TCA levels within its perception limit (4 ng/L). In addition, the temperature sensitivity of O-methyltransferases enzymatic activity was described, and the effect of temperature increase from 10 to 25 °C in accelerating the 2,4,6-TCA formation rate in WDSs was explained. Controlling source water 2,4,6-TCP concentration by accepting appropriate treatment techniques was recommended as the primary strategy for regulating the T&O problems in WDSs.

Enhanced perfluorooctanoic acid (PFOA) accumulation by combination with in-situ formed Mn oxides under drinking water conditions

Particulate manganese oxide (MnOx) deposition in drinking water distribution systems (DWDS) gives rise to the risk of water discoloration at the consumers' tap; however, its role in the fate and transport of trace organic pollutants in DWDS is not clear. Perfluorooctanoic acid (PFOA), a persistent organic pollutant frequently detected in natural water, was selected to investigate the potential effect of MnOx on its transportation behavior under DWDS conditions through laboratory batch experiments. The results show that PFOA can be greatly combined with MnOx formed in-situ through a Mn(II) oxidation process by free chlorine. However, the accumulation of PFOA by preformed MnOx was negligible. It was found that 1 mg/L Mn captured over 50% of PFOA with an initial concentration of 50 ng/L during oxidation. The water compositions of actual water could contribute to the effect of PFOA accumulation to a certain extent. Characterization of the solid products revealed that PFOA is homogenously embedded into MnOx. The combination of PFOA with MnOx occurs through a bridging effect of Mn(II) between the surface hydroxyls of MnOx and the -COOH group of PFOA. The resulting MnOx-PFOA particles were more inclined to agglomerate, enabling possibly easy deposition onto the pipe wall than ordinary MnOx particles. This study provides insights into the co-occurrence of metal deposits with PFOA and the potential risks posed by PFOA accumulation to consumers through the water distribution process.

A review of the flavor profile of metal salts: understanding the complexity of metallic sensation

The oral sensation of metallic is a complex experience. Much of our current understanding of metallic sensation is from the investigation of metal salts, which elicit diverse sensations, including taste, smell, and chemesthetic sensations, and therefore meet the definition of a flavor rather than a taste. Due to the involvement of multiple chemosensory systems, it can be challenging to define and characterize metallic sensation. Here, we provide a comprehensive review of the psychophysical studies quantifying and characterizing metallic sensation, focusing on metal salts. We examine the factors that impact perception, including anion complex, concentration, nasal occlusion, and pH. In addition, we summarize the receptors thought to be involved in the perception of metallic sensation (i.e., TRPV1, T1R3, TRPA1, and T2R7) either as a result of in vitro assays or from studies in knock-out mice. By enhancing our scientific understanding of metallic sensation and its transduction pathways, it has the potential to improve food and pharmaceuticals, help identify suppression or masking strategies, and improve the ability to characterize individual differences in metallic sensation. It also has the potential to translate to clinical populations by addressing the disparities in knowledge and treatment options for individuals suffering from metallic taste disorder (i.e., phantom taste or "metal mouth"). Future psychophysical studies investigating the sensory perception of metal salts should include a range of compounds and diverse food matrices, coupled with modern sensory methods, which will help to provide a more comprehensive understanding of metallic sensation.

Nutrient Effect on the Taste of Mineral Waters: Evidence from Europe

In this study, 15 selected bottled mineral waters from chosen European countries were tested for their mineral nutrient contents. In particular, six important nutrients (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-) were measured using atomic absorption spectroscopy. The content of mineral nutrients in all sampled mineral waters were compared to their expected content based on the label. Consequently, their taste was evaluated by 60 trained panelists who participated in the sensory analysis. The results from both the atomic absorption spectroscopy and sensory analysis were analyzed using the regression framework. On the basis of the results from the regression analysis, we determined to what extent the individual mineral nutrients determined the taste of the mineral water. According to the regression results, four out of six analyzed nutrients had a measurable impact on taste. These findings can help producers to provide ideal, health-improving nutrients for mineral water buyers.

Fluorescein Derivatives as Fluorescent Probes for pH Monitoring along Recent Biological Applications

Potential of hydrogen (pH) is one of the most relevant parameters characterizing aqueous solutions. In biology, pH is intrinsically linked to cellular life since all metabolic pathways are implicated into ionic flows. In that way, determination of local pH offers a unique and major opportunity to increase our understanding of biological systems. Whereas the most common technique to obtain these data in analytical chemistry is to directly measure potential between two electrodes, in biological systems, this information has to be recovered in-situ without any physical interaction. Based on their non-invasive optical properties, fluorescent pH-sensitive probe are pertinent tools to develop. One of the most notorious pH-sensitive probes is fluorescein. In addition to excellent photophysical properties, this fluorophore presents a pH-sensitivity around neutral and physiologic domains. This review intends to shed new light on the recent use of fluorescein as pH-sensitive probes for biological applications, including targeted probes for specific imaging, flexible monitoring of bacterial growth, and biomedical applications.

Impact of water source mixture and population changes on the Al residue in megalopolitan drinking water

This study establishes a new understanding of the contributions of Al residue in a megalopolitan drinking water supply system with mixed water sources. The different influences and contributions of foreign water source, resident migration and season changing to Al residue in drinking water were investigated. Especially, the role of Southern water transferred over 1200 km via the South-to-North Water Diversion Project in the Al residue of drinking water supply system of a northern megalopolitan were revealed for the first time. Comparisons of big data on Al residue in the water supply system with sole and mixed water sources showed that the introduction of Southern water enhanced the Al residue in drinking water by over 35%. The world's largest annual residents' migration during Chinese Lunar New Year and the changes of season affect the water pipework hydrodynamics, which were embodied as the periodic changes of particulate aluminium and the relations with resident's temporal-spatial distribution in the megalopolitan. Because of the differences in water quality, Southern water promotes the release of historically deposited Al and facilitates the cleaning of old pipes.

Human exposure to particles at the air-water interface: Influence of water quality on indoor air quality from use of ultrasonic humidifiers

Ultrasonic humidifiers provide indoor relief to symptoms caused by dry air and produce aerosols containing both water and minerals that are present in the water that fills the humidifier. This study investigated the spatial distributions, concentrations, and metal and mineral composition of aerosols emitted when an ultrasonic humidifier was filled with deionized water (DI), low mineral tap water (LL), high total dissolved solids (TDS)/high hardness water (HH), and high TDS/low hardness water (HL). Aerosol/particle sizes and counts were obtained at six horizontal distances in both the plume and near floor for each water quality. Results are that water quality significantly affects particle size distributions which become uniform after 0.9 m from the humidifier outlet, and are independent of vertical distance from the humidifier. The mean count median diameters were 64 nm for DI, 129 nm for LL, 234 nm for HH, and 260 nm for HL; the particle counts and total mineral solids concentrations were 2,194 #/cm³ (16 µg/m³) for DI, 21,070 #/cm³ (113 µg/m³) for LL, 38,353 #/cm³ (438 µg/m³) for HH, and 43,880 #/cm³ (521 µg/m³) for HL. The µg/m³ values for LL, HH, and HL exceeded PM_2.5 ambient air standards. Model predictions are that the deposition mass in the human respiratory system from inhaling particles emitted from HH and HL water exceed 135 µg for a 1 to 3-month old child and 600 µg for an adult over an 8-hr period. Mineral water quality significantly affects the distribution and concentration of emitted and inhaled indoor air particles. Consumers may unknowingly be degrading their indoor air quality when using tap water of acceptable drinking water quality as humidifier fill water.

Sources of and Solutions to Toxic Metal and Metalloid Contamination in Small Rural Drinking Water Systems: A Rapid Review

Exposure to toxic metals and metalloids (TMs) such as arsenic and lead at levels of concern is associated with lifelong adverse health consequences. As exposure to TMs from paint, leaded gasoline, canned foods, and other consumer products has decreased in recent decades, the relative contribution of drinking water to environmental TM exposure and associated disease burdens has increased. We conducted a rapid review from June to September 2019 to synthesize information on the sources of TM contamination in small rural drinking water systems and solutions to TM contamination from these sources, with an emphasis on actionable evidence applicable to small rural drinking water systems worldwide. We reviewed publications from five databases (ProQuest, PubMed, Web of Science, Embase, and Global Health Library) as well as grey literature from expert groups including WHO, IWA, and others; findings from 61 eligible review publications were synthesized. Identified sources of TMs in included studies were natural occurrence (geogenic), catchment pollution, and corrosion of water distribution system materials. The review found general support for preventive over corrective actions. This review informs a useful planning and management framework for preventing and mitigating TM exposure from drinking water based on water supply characteristics, identified contamination sources, and other context-specific variables.

Identifying the function of activated carbon surface chemical properties in the removability of two common odor compounds

In this study, the adsorption capacities of two common odor compounds, 2-methylisoborneol (2-MIB) and dimethyl disulfide (DMDS), onto nine common types of powdered activated carbon (PAC) were comprehensively compared to screen the critical surface chemical properties affecting the adsorption performance. The results showed that the adsorption capacities of all the PACs for DMDS were generally lower than those for 2-MIB. The Spearman's rank correlation analysis indicated that the adsorption capacity for 2-MIB did not have any correlation with the PAC surface sites, while the DMDS adsorption capacity was positively related to the number of basic sites. The effect of the PAC basic sites on the DMDS adsorption was further verified by density functional theory (DFT) calculation in two adsorption modes (facial mode and edge mode). The graphene structure in the edge mode was the most favorable for DMDS adsorption with the lowest adsorption enthalpy, followed by the ketone-doped structure under the facial mode. An independent gradient model indicated that van der Waals forces were dominant in the DMDS adsorption. Moreover, thermal modification was conducted to further prove the relationship between the basic sites and the DMDS adsorption. After thermal modification, the PAC with more basic sites and graphene structures was found to be more effective for DMDS adsorption. Overall, this study could offer guidance for water treatment plants with respect to the selection of PAC to solve the odor problems caused by various compounds (e.g., DMDS or 2-MIB), and the modification of PAC, aiming at more efficient odor removal.

Heme as a Taste Molecule

PURPOSE OF REVIEW

The sense of taste has evolved to enable the identification of appropriate substances to consume, to acquire nutrients, and to avoid consuming potential toxins. Five basic taste classes have been recognized, although there may be others, including metallic taste, which have not been well defined. The purpose of this review was to survey available data from diverse sources to determine how much was known about the molecular basis for metallic taste.

RECENT FINDINGS

Metallic taste has been studied in the context of dysgeusia, primarily using non-heme iron as an inducer of metallic taste sensation. However, recent efforts by industry to develop plant-based meat substitutes have suggested that iron in the form of heme may be the main molecule underlying the taste of meat. Little work has been done on heme as a taste molecule. Data support a primary role for heme in metallic taste that may have evolved as part of a means to consume and preserve elemental iron for physiological needs.

Perception of tap water quality: Assessment of the factors modifying the links between satisfaction and water consumption behavior

Perception of tap water is subject to a wide range of factors and interactions. These include risk perception, tap water quality and organoleptic perceptions, microbiological and chemical quality, prior experiences, information sources, trust in water companies and other groups, and perceived control and contextual factors, among others. The objective of this study is to assess the factors that influence and determine citizen behavior regarding drinking water. A phone survey was conducted among 1014 citizens living in the city of Québec, Canada. Five different domestic water consumption profiles were elaborated according to the citizens' preferences and behavior. Descriptive statistics and mediation analyses were carried out to analyse the survey results and assess the factors modifying the links between satisfaction and water consumption behavior. Results show that drinking water quality could be loosely linked with overall satisfaction with tap water. The water consumption profile was strongly linked with satisfaction levels related to the taste, odor and color of tap water. We observed that the association between an individual's tap water satisfaction and water consumption behavior was mediated by the water treatment strategies applied at home (filtering, cooling), knowledge about drinking water quality and its production, and risk perception. The mediating effects were shown to be significant mainly among bottled-water-only and tap-water-only consumers. Future interventions that aim to encourage the population's use of tap water as a primary source should prioritize cooling and filtering tap water in their messaging, in order to improve population satisfaction. The reduction of risk perception through targeted information campaigns is also of primary importance for decreasing the number of citizens who exclusively drink bottled water.

A review: The challenge, consensus, and confusion of describing odors and tastes in drinking water

Documentation exists for many chemicals that cause tastes and odors in water, however, water suppliers do not routinely monitor for these chemicals. Effective management of a taste-and-odor (T&O) problem in drinking water often requires good verbal description of the offending sensory experience. Experience demonstrates that obtaining verbal descriptions is challenging. To improve our understanding of communications, sensory science literature was reviewed to obtain descriptors for twenty-one chemicals acknowledged to cause T&O issues in drinking water. The review focused on pure chemicals above their odor threshold concentrations. Results reveal that descriptors follow four general categories. For select chemicals, strong consensus exists around a single or very few appropriate descriptors. Examples are "salty" for sodium and "chlorinous" for free chlorine. The next category has moderate agreement for several descriptors, with at least one major descriptor. For example the microbiological metabolite 2-methylisoborneol is most commonly described as "earthy/musty/moldy" but also "camphor, grass, and sweet". Some chemicals have weak agreement on their descriptors, but overall associate words with similar meaning. An example is the chemical toluene with descriptors of "solvent-like" words including "solvent", "gasoline", "paint-like", "cleaning fluid", and "etherish", but also "vinegar" and "sweet". The last chemical category possesses diverse descriptors with no consensus. For example, the oxylipin n-heptanal is described as "oily, fatty, chemical, musty/earthy/moldy, rancid, sweaty, grass, sickening, and stale". While descriptor diversity for select chemicals may not identify the cause of T&O, understanding that certain chemicals are perceived very differently aids in effective communications and eliminates confusion from expecting consumers or utility personnel to respond with consensus.

Sources of and solutions to mistrust of tap water originating between treatment and the tap: Lessons from Los Angeles County

Tap water mistrust has adverse impacts on health and welfare. This study identifies, defines and motivates attention to cases of mistrust of tap water which originate between the treatment plant and the tap where people ultimately consume it. Between treatment and the tap, water quality contamination can be introduced within two segments of the built environment with two distinct responsible parties- community water system's distributional networks and property owner's premise plumbing. This contamination is considered secondary from a health perspective but elevates consumer concern. We use examples from Los Angeles County, an area with high resident tap water mistrust especially among disadvantaged communities, despite there being relatively few health-related water quality violations. We triangulate evidence from primary and secondary sources to illustrate how such water quality concerns occur. We identify potential solutions to address concerns using a series of case studies of communities with high levels of tap water mistrust, a stakeholder workshop and associated working group on premise plumbing concerns, and customer concern data from the city of Los Angeles' water system. Findings suggest that there are numerous instances where the distributional network, and secondarily premise plumbing, introduce water quality contamination which contributes to tap mistrust in urban communities by making water unclean, but not necessarily unsafe per existing regulation. In cases where water systems' distributional networks have introduced water quality contamination, responses to assuage concerns have largely rested upon pressure from the press and advocates. Premise plumbing issues have been harder to address. Our study suggests that an evidence-based path forward to comprehensively addressing these issues involves new requirements for systems to report quality contamination in distributional networks and incentives for property owners to upgrade premise plumbing. Moreover, this study reasserts that infrastructure neglect contributes to rational, but costly decision-making by disadvantaged urban communities to consume tap alternatives.

Emission of iron and aluminum oxide particles from ultrasonic humidifiers and potential for inhalation

Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This research evaluated the behavior of insoluble iron oxide and aluminum oxide particles in water used to fill room-sized ultrasonic humidifiers. Solutions of 10 mg/L Fe, as iron oxide particles, or 5 mg/L Al, as aluminum oxide suspension, were added into tap water used to fill ultrasonic humidifiers. The humidifiers were operated for 14 h; samples were obtained over time and monitored for soluble and particulate Fe and Al, as well as particle sizes in the humidifier reservoir and emitted in aerosols. Denser, settleable particles of approximately 1.5 μm diameter of iron or aluminum oxides accumulated at the bottom of the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22-0.57 μm diameter were emitted as aerosols from the humidifier. Soluble anions and cations in tap water were also present in the aerosols emitted from humidifiers. The results indicate that a typical 1.6 MHz ultrasonic humidifier can emit 0.22-0.57 μm particles and dissolved minerals from fill water into breathable air.

Field studies of manganese deposition and release in drinking water distribution systems: Insight into deposit control

Drinking water discoloration is one of the most common customer complaints. The accumulation of residual manganese (Mn) in drinking water distribution systems (DWDS) accounts for part of the discolored water that reaches household taps. Field studies were conducted at seven full-scale DWDS to investigate the deposition and release behaviors of Mn in different forms and at different concentrations in finished water. The results show that particulate Mn tended to accumulate in DWDS even at concentrations as low as 10 μg/L. The oxidation of soluble Mn(II) ions in DWDS was highly affected by water chemistries as well as water age; 10 μg/L of soluble Mn could still transform into particulate Mn under suitable conditions. When total Mn concentration in finished water was below 5 μg/L, erosion of Mn deposits occurred in DWDS with a Mn deposit inventory. Soluble Mn release was observed when chlorine or chlorine dioxide concentration was lower than 0.1 mg/L, and the release was speculated to be a result of microbial reductive dissolution of Mn oxides. Ensuring the total Mn concentration is below 10 μg/L and decreasing the particulate Mn concentration to 5 μg/L in finished water are both recommended to minimize Mn accumulation risk in DWDS. Enhanced oxidation and filtration for Mn removal during water treatment processes are proposed.

Leaching of Organic Toxic Compounds from PVC Water Pipes in Medina Al-Munawarah, Kingdom of Saudi Arabia

It is well established that the use of synthetic material in water pipes significantly affects the quality of domestic water, especially trace organics that are leached through with the flow of water. In the present study, the migration of volatile organic compounds (VOCs) from water pipes manufactured of polyvinyl chloride (PVC) has been investigated using static laboratory conditions and in residential areas. The contact of deionized water with various PVC pipes for three successive test periods of 24, 48, and 72 h duration has been made. Twenty water samples were collected from houses within Medina Al-Munawarah residential area and were analyzed by using solid phase extraction, followed by high resolution gas chromatography with flame ionized detector (GC-FID). The presence of carbon tetrachloride (CTC), toluene, chloroform, styrene, o-xylene, bromoform (BF), dibromomethane (DBM), cis-1,3-dichloropropane (Cis-1,3-DCP), and trans-1,3-dichloropropane (Trans-1,3-DCP) was initially confirmed. The most frequent contaminants found were DBM, CTC, and toluene that were monitored in 55%, 50%, and 45% of samples, respectively. The levels of CTC, Cis-1,3-DCP, and Trans-1,3-DCP were found to exceed the World Health Organization (WHO) limits in 50%, 20%, and 20% of samples, respectively. The migration test indicated that nine of the targeted contaminants occur in a double distilled water sample incubated in pipe in laboratory level experiment. This implies that these components are more likely to migrate from PVC pipe in home plumbing systems network.

Antifouling effect of water-soluble phosphate glass frit for filtration plants

The antifouling, antimicrobial, elution behavior, skin irritant, and cytotoxicity properties of water-soluble phosphate glass on stainless steel were evaluated. Water-soluble phosphate glass samples with 35% Cu (mol/mol) were prepared by altering the network modifier (Na₂O, K₂O) and network former (P₂O₅, B₂O₃) compositions. The materials were melted at temperatures within the range of 850-950 °C. The melt was then quenched and ground into fine particles using a twin roll mill. The resulting water-soluble glasses were prepared as glass frit (size < 100 μm) using a sieve. The amorphous phase was determined by X-ray diffraction and differential thermal analysis. Water-soluble glasses with a reduced Cu ion elution rate of 1.2 ppm per week were formed because the chemical resistances of the formulated glasses improved as the P₂O₅ content decreased and the B₂O₃ content increased. To test its antifouling properties, the glass frit was mixed with paint and coated onto a STS316L sheet. The surface roughness was increased markedly from 1.4 to 19.2 nm, increasing the specific surface area for antimicrobial activity. It was demonstrated that the proposed method was able to form noncytotoxic, nonirritant, water-soluble glasses with 99.9% antimicrobial activity against Staphylococcus aureus. These results suggest that water-soluble phosphate glass on STS316L sheets could be useful in filtration plants.

Toward a comprehensive explanatory model of reliance on alternatives to the tap: evidence from California's retail water stores

Building on a recent increase in scholarly attention to the problem of tap water mistrust and resulting negative health impacts, we examine the relationship between neighborhood reliance on tap water alternatives and a range of explanatory factors. We model retail water store locations as a proxy for reliance on tap water alternatives in urbanized neighborhoods across California. Our study is unique in its inclusion of variables representing both compliance with primary and secondary water quality standards by publicly regulated drinking water systems serving particular neighborhoods, other water system attributes and the socioeconomic characteristics of neighborhoods. The location of retail water stores in urbanized neighborhoods does not appear strongly related to observed measures of water quality. Secondary contamination shows a weak relationship to tap alternative reliance, and primary contamination was not correlated with higher levels of tap alternative reliance. On the other hand, our research suggests that other socioeconomic factors, particularly country of birth, are associated with the prevalence of more water stores. Increasing reliance on tap water likely requires measuring and addressing secondary contamination found in distributional systems and premise plumbing, and more aggressive public education campaigns.

Variations in sensitivity to chlorine in Ecuador and US consumers: implications for community water systems

Successful implementation of chlorination for disinfecting community water systems in developing countries faces obstacles, with rejection of chlorinous flavor as a significant factor. Determining consumers' abilities to accurately detect chlorine in treated water is important to identifying acceptable chlorination levels that are also effective for water disinfection. Chlorine detection sensitivity was tested in untrained Ecuadorian consumers with limited prior experience with chlorinated water and US consumers with extensive prior experience with chlorinated water. Water samples with free chlorine concentrations up to 3.0 mg/L were presented for flavor testing. Ecuadorian consumers showed higher sensitivity, being able to detect chlorination at 2.0 and 3.0 mg/L, while US consumers did not reliably detect chlorine presence for any concentration levels. Additionally, Ecuadorian consumers' rejection of water samples depended on chlorination, showing a statistically significant increase in rejections of samples with chlorine concentrations above 1.0 mg/L. On the other hand, although US consumers rejected more samples overall, their tendency to reject did not vary as a function of chlorination levels. This study demonstrated that limited experience with chlorination is a critical factor for accurate chlorine flavor detection in drinking water.

Effect of lactoferrin on taste and smell abnormalities induced by chemotherapy: a proteome analysis

Cancer patients receiving chemotherapy often experience taste and smell abnormalities (TSA). To date, the underlying molecular mechanisms of this frequent side-effect have not been determined and effective treatments are not available. This study assessed the feasibility of lactoferrin (LF) supplementation as a treatment for TSA and investigate the related mechanisms through salivary proteome analysis. Nineteen cancer patients with established TSA following chemotherapy administration were enrolled in this study. Cancer patients and additional 12 healthy subjects took LF supplements, 3 tablets per day (250 mg per tablet), for 30 days. Saliva was collected at three timepoints: baseline, 30-day LF supplementation, and 30-day post-LF supplementation. Patient's TSA level, salivary proteome, and salivary minerals at each LF treatment stage were analyzed. High TSA level was associated with high concentration of salivary Fe and loss of critical salivary immune proteins. LF supplementation significantly decreased the concentration of salivary Fe (P = 0.025), increased the abundance (P < 0.05) of salivary α-amylase and Zn-α-2-GP, and led to an overall increase of expression (≥2-fold changes) of immune proteins including immunoglobulin heavy chain, annexin A1, and proteinase inhibitor. Abundance of α-amylase and SPLUNC2 were further increased (P < 0.05) at 30-day post-LF supplementation in cancer patients. At the same time, total TSA score was significantly reduced (P < 0.001) in chemotherapy patients. This study demonstrated the feasibility of developing lactoferrin supplementation as a treatment to reduce TSA caused by chemotherapy and improve cancer patient's oral immunity.

Low risk posed by engineered and incidental nanoparticles in drinking water

Natural nanoparticles (NNPs) in rivers, lakes, oceans and ground water predate humans, but engineered nanoparticles (ENPs) are emerging as potential pollutants due to increasing regulatory and public perception concerns. This Review contrasts the sources, composition and potential occurrence of NNPs (for example, two-dimensional clays, multifunctional viruses and metal oxides) and ENPs in surface water, after centralized drinking water treatment, and in tap water. While analytical detection challenges exist, ENPs are currently orders of magnitude less common than NNPs in waters that flow into drinking water treatment plants. Because such plants are designed to remove small-sized NNPs, they are also very good at removing ENPs. Consequently, ENP concentrations in tap water are extremely low and pose low risk during ingestion. However, after leaving drinking water treatment plants, corrosion by-products released from distribution pipes or in-home premise plumbing can release incidental nanoparticles into tap water. The occurrence and toxicity of incidental nanoparticles, rather than ENPs, should therefore be the focus of future research.

Sensory politics: The tug-of-war between potability and palatability in municipal water production

Sensory information signaled the acceptability of water for consumption for lay and professional people into the early twentieth century. Yet as the twentieth century progressed, professional efforts to standardize water-testing methods have increasingly excluded aesthetic information, preferring to rely on the objectivity of analytic information. Despite some highly publicized exceptions, consumer complaints remain peripheral to the making and regulating of drinking water. This exclusion is often attributed to the unreliability of the human senses in detecting danger. However, technical discussions among water professionals during the twentieth century suggest that this exclusion is actually due to sensory politics, the institutional and regulatory practices of inclusion or exclusion of sensory knowledge from systems of action. Water workers developed and turned to standardized analytical methods for detecting chemical and microbiological contaminants, and more recently sensory contaminants, a process that attempted to mitigate the unevenness of human sensing. In so doing, they created regimes of perception that categorized consumer sensory knowledge as aesthetic. By siloing consumers' sensory knowledge about water quality into the realm of the aesthetic instead of accommodating it in the analytic, the regimes of perception implemented during the twentieth century to preserve health have marginalized subjective experiences. Discounting the human experience with municipal water as irrelevant to its quality, control and regulation is out of touch with its intended use as an ingestible, and calls for new practices that engage consumers as valuable participants.