Drinking Water Treatment Plants Research Articles

Towards a better understanding of CeO2 manufactured nanoparticles adsorption onto sand grains used in drinking water treatment plants

Increasing production of CeO2 nanoparticles (NPs) will inevitably lead to their higher emissions into natural water bodies. As these emissions pose a significant treat in terms of environmental impacts and possible human health risks, it is necessary to carefully evaluate processes responsible for their mobility, retention and bioavailability. Adsorption is considered as one of the most important processes controlling the fate and transport of nanomaterials in the environment and industrial filtration units. However, mechanisms and physical or chemical parameters influencing these processes are still poorly understood, especially in the case of porous materials used in water purification. In this study, mechanisms responsible for deposition and attachment of CeO2 nanoparticles (NPs) onto quartz sand used as a filter medium in the drinking water treatment plant of Geneva (Switzerland) are examined. For that purpose, a combination of theoretical kinetics and thermodynamic models and a variety of complementary experimental techniques are used. Batch experiments were performed using ultrapure water (pH of 3.0; reference case) and filtered raw Geneva Lake water (pH of 8.6). Size and surface charge of CeO2 NPs dispersed in the supernatant after mixing with sand were determined using dynamic light scattering and laser Doppler velocimetry whereas residual CeO2 NPs concentrations were measured by UV–vis spectroscopy. CeO2 NPs were found to adsorb onto sand grains surfaces under acidic conditions due to electrostatic attractive interactions. The kinetics of adsorption followed well both pseudo-first-order and pseudo-second-order model. The adsorption process was successfully described by Langmuir isotherm which indicated the formation of a monolayer, with a maximal adsorption capacity of 0.85 ± 0.20 mg g-1 at grain surfaces. Further scanning electron microscopy (SEM) images showed individual CeO2 NPs or small aggregates attached to the sand surface, thus confirming the adsorption mechanisms and corresponding model. The results obtained from batch studies conducted using Geneva Lake water showed that aggregation, caused by the presence of natural organic matter (NOM) and multivalent ions, and further aggregate sedimentation are the main processes responsible for CeO2 NPs elimination under environmental conditions. Moreover, as CeO2 NPs and sand grains both carried negative charges, electrostatic repulsion was a main factor limiting the adsorption. The SEM images confirmed these observations and revealed only few aggregates in the vicinity of sand surface irregularities.

Influence of environmental variables on the energy efficiency of drinking water treatment plants

Evaluating and benchmarking the energy efficiency of drinking water treatment plants (DWTPs) is essential to improve the environmental and economic performance of these facilities. However, robust and reliable methods should be used to compute energy efficiency scores to avoid biased conclusions. In this study, the stochastic non-parametric envelopment of data (StoNED) method was employed to assess the energy efficiency of a sample of 146 DWTPs. This methodological approach also allowed us to explore the influence of several environmental variables on the energy performance of DWTPs. The average energy efficiency score of the facilities evaluated was 0.461. It means that they could save 54% of the current energy consumption. 42% of the DWTPs evaluated presented an average energy efficiency score varied between 0.41 and 0.61. None of the 146 water treatment facilities was identified as fully energy efficient which evidences that all DWTPs could save energy. The source of raw water, the age of the DWTP and the main technology used to treat raw water were factors that statistically affected the energy efficiency of DWTPs. It was also estimated that a 1% increase in the removal of total dissolved solids and sulfates result in an increase in energy consumption by 0.340 and 0.409%, respectively, ceteris paribus. The information and conclusions of this study are of great interest for water managers and regulators to improve the operation of DWTPs and plan the design of new facilities.

Tap water as a natural vehicle for microorganisms shaping the human gut microbiome.

Fresh potable water is an indispensable drink which humans consume daily in substantial amounts. Nonetheless, very little is known about the composition of the microbial community inhabiting drinking water or its impact on our gut microbiota. In the current study, an exhaustive shotgun metagenomics analysis of the tap water microbiome highlighted the occurrence of a highly genetic biodiversity of the microbial communities residing in fresh water and the existence of a conserved core tap water microbiota largely represented by novel microbial species, representing microbial dark matter. Furthermore, genome reconstruction of this microbial dark matter from water samples unveiled homologous sequences present in the faecal microbiome of humans from various geographical locations. Accordingly, investigation of the faecal microbiota content of a subject that daily consumed tap water for 3 years provides proof for horizontal transmission and colonization of water bacteria in the human gut.

Design and coagulation mechanism of a new functional composite coagulant in removing humic acid

The deep removal of organic pollutants is a challenging task for coagulation technology in the drinking water and wastewater treatment plants to satisfy the rising water standards. To obtain high removal efficiency for organic matter (OM), a novel coagulant, Fe-PAA, was developed based on ferric salts and polyacrylic acid (PAA) in this study, which contained long flexible carbon chain and positive coordination sites. The humic acid (HA) was employed as a representative OM target with wide molecular weight range in the coagulation tests. The coagulant Fe-PAA with Fe3+/COOH ratio of 1:1 exhibited the promising coagulation performance meeting with the initial design principle. Compared to ferric chloride, Fe-PAA-1:1 exhibited overall advantages on HA removal, formation of large and compact flocs, and control of residual Fe3+. As a macromolecular coagulant, Fe-PAA-1:1 demonstrated the synergetic advantages of iron hydrolysis components and flexible long-chain polymers. The charge neutralization and bridging effects dominated coagulation process under acidic condition, while complexation and bridging effects were the main driving force of Fe-PAA-1:1 under neutral and alkaline conditions for HA removal. Overall, this study provides revelatory information for the development of a new kind of highly efficient and cost-effective coagulant to satisfy the demand of current water treatment.

Contamination and Removal Efficiency of Microplastics and Synthetic Fibres in a Conventional Drinking Water Treatment Plant

Microplastics have been detected all around the globe in freshwaters which are frequently used to produce drinking water. Therefore, the contamination of raw water with microplastics that supplies drinking water treatment plants, and their removal efficiency is raising more concern and interest. In the present study, we evaluated the microplastic contamination in a conventional drinking water treatment plant (Geneva, Switzerland) and the contribution of coagulation on the efficiency of the filtration systems (sand and activated carbon filtrations) in the removal efficiency of microplastics (MPs) and synthetic fibres. This work was performed in a pilot station that replicates the main drinking water treatment process. Raw water and effluents of each filtering processes were analysed for the presence of MPs and synthetic fibres with sizes ≥ 63 μm using infrared spectroscopy. The contamination of MPs in raw water and in drinking water ranged from 19.5 to 143.5 MPs/m3 and from 0 to 8 MPs/m3 (in presence and absence of coagulant), respectively. On the other hand, concentration of synthetic fibres ranged from 7.7 to 23.8 synthetic fibres/m3 in raw water and from 0 to 3 synthetic fibres/m3 in drinking water. Results show that on average 89% of microplastics and 81% of synthetic fibres (≥63 μm) are retained in water treatment in absence of coagulant. Better final removal efficiency of microplastics (97%) and synthetic fibres (96%) was observed in drinking water with coagulation treatment. The chemical composition of microplastics and synthetic fibres is found more heterogeneous in raw water than after sand filtration and activated carbon filtration.

2,6-Dichloro-1,4-benzoquinone formation from chlorination of substituted aromatic antioxidants and its control by pre-ozonation in drinking water treatment plant

Halobenzoquinones are frequently detected as disinfection by-products in drinking water. Among identified halobenzoquinones, 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) is particularly toxic and is frequently detected in drinking water. Synthetic aromatic antioxidants discharged to source water may increase the risk of 2,6-DCBQ formation, as many studies suggest that aromatic compounds are the most likely precursors to 2,6-DCBQ. Herein, we investigated the formation of 2,6-DCBQ from chlorination of three model aromatic antioxidants, including 3-tert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT) and bis(4-tert-butylphenyl)amine (BBPA). Only BBPA produced 2,6-DCBQ under chlorination, while chlorination of BHA and BHT formed α, β-unsaturated C4-dicarbonyl ring-opening products and phenolic compounds. Based on mass balance and intermediate transformation analysis, mechanisms for the formation of 2,6-DCBQ from BBPA chlorination involved hydrolysis, tert-butyl group cleavage, chlorine substitution, desamination and oxidation. Mitigating aromatic compounds will be an efficient method for 2,6-DCBQ control, such as pre-ozonation, because the intermediates involved in 2,6-DCBQ formation were aromatic compounds. Real water samples from two drinking water treatment plants (DWTPs), one with pre-ozonation (DWTP 2) and the other without pre-ozonation (DWTP1), were analyzed. The two DWTPs were built along the Yangtse river in Nanjing city. Raw water parameters from the two DWTPs, including dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254) and NH3–N, indicated the water quality between these sources was similar. Pre-ozonation in DWTP 2 vanished 2,6-DCBQ in raw water. Concentrations of 2,6-DCBQ in finished water from DWTP 1 (5.69 ng/L) was higher than concentrations generated from DWTP 2 (1.31 ng/L). These results demonstrate that pre-ozonation, granular activated carbon (GAC) and quartz sand treatments at DWTP 2 remove more 2,6-DCBQ precursors than the conventional quartz sand and GAC treatments in DWTP 1. These results suggest the pre-ozonation, GAC and quartz sand treatments can help minimize concentrations of 2,6-DCBQ generated in DWTPs.

Exploring the origin of efficient adsorption of poly- and perfluoroalkyl substances in household point-of-use water purifiers: Deep insights from a joint experimental and computational study

Poly- and perfluoroalkyl substances (PFAS) are harmful chemicals to humans and widely detected in water bodies including tap water. PFAS cannot be efficiently removed from water through conventional treatment processes used in full-scale drinking water treatment plants, posing a latent risk to human health via drinking tap water. Here in-field investigations show that the household point-of-use (POU) water purifiers constituted with coconut shell activated carbon can achieve 21%–99% removal for 14 legacy and emerging PFAS in tap water based on the ratio of influent and effluent. Extensive characterizations combine with chemical analyses demonstrate that physical adsorption based on Van der Waals force can remove 23 PFAS from tap water, wherein the hydrophobicity of PFAS is the crucial factor. Density functional theory calculations together with the quantitative structure–activity relationship model confirm that both topological structures as well as hydrophobicity of PFAS and electrostatic interactions between the strong electronegative F atoms and the adsorbent surface are the most critical factors controlling the PFAS adsorption to activated carbon. Overall, our results offer insights into the molecular mechanisms that enable the adsorption of PFAS in POU filters.

Prevalence of antibiotic resistance genes in drinking water of the Kathmandu Valley, Nepal

In resource-limited settings, fecal indicator bacterial analysis is the only microbiological water quality test performed, and emerging contaminants, such as antibiotic resistance genes (ARGs), are often neglected. To address this knowledge gap, water samples were collected from shallow wells (n = 24), deep wells (n = 16), stone spouts (n = 14), springs (n = 8), tanker filling stations (TFS; n = 12), water tankers (n = 12), and drinking water treatment plants (DWTPs; n = 6 each of raw and treated water) of the Kathmandu Valley, Nepal, between December 2015 and August 2016 to investigate the presence of five ARGs (blaNDM-1, blaCTX−M, tetB, qnrS, and sul1) and class one integrase gene (intI1). All ARGs were detected in water samples from shallow wells and stone spouts, whereas blaNDM-1 and blaCTX−M were not detected in deep wells and springs. tetB and intI1 were detected at a greater number of water tanker samples than TFS, indicating that water tankers were not disinfected regularly. Only sul1 and intI1 were detected in treated water of DWTPs. Persistence of intI1 throughout the water treatment process and significantly strong correlation (ρ > 0.5, p < 0.05) with the majority of ARGs included in our study suggested the suitability of intI1 to assess the contamination and fate of ARGs in drinking water of the valley. Low free chlorine levels in treated water before pipeline distribution urge water quality managers to evaluate tap water for pathogens and ARGs. Further studies are recommended on emerging contaminants, such as antibiotics, in drinking water sources that are not routinely assessed but can provide selective pressure for the spread of antibiotic resistance in the environment.

Per- and polyfluoralkyl substances (PFAS) in drinking water system: Target and non-target screening and removal assessment

The massive use and the persistence of per- and polyfluoroalkyl substances (PFAS) have led to their frequent detection in aquatic environments, which may further threaten drinking water safety. So far, our knowledge about the occurrence of PFAS in drinking water system is still very limited. Here we investigated the occurrence and removal of PFAS in a drinking water system using non-target, suspect and target screening strategies. Sampling was performed in three seasons in the drinking water system including a water source, two drinking water treatment plants, and tap water in five households. The results showed detection of 17 homologous series with 51 homologues in non-target screening and 50 potential PFAS detected in suspect screening. Probable structures were proposed for 15 PFAS with high confidence levels (the first three of the five levels), with seven of them being reported for the first time in drinking water system. Semi-quantification was performed on seven homologous series based on target PFAS, the estimated total concentrations for non-target PFAS ranged between 4.10 and 17.6 ng/L. Nine out of 50 target PFAS were found and precisely quantified (<LOQ-13.4 ng/L) with predominance of perfluorocarboxylic acids (PFCA) and perfluorosulfonic acids (PFSA). All target and non-target PFAS were detected in tap water with similar concentrations in all three seasons. Removal efficiency for the detected PFAS in each processing unit was almost zero, indicating the recalcitrance of these chemicals to the conventional treatment process. The findings from this study clearly show the wide presence of PFAS in the whole drinking water treatment process, and suggest an urgent need for effective removal technology for this group of chemicals.

Effect of ozone–tea polyphenols as a drinking water disinfection process on antibiotic resistance genes

Abstract In recent years, the wide spread of antibiotic resistance genes (ARGs) has brought tremendous risk to the biological safety of drinking water. With the increasing demand for drinking water quality, ARGs have been regarded as a new pollutant that may cause serious public health problems. A large number of studies have shown that the disinfection process of drinking water treatment plants can remove ARGs. However, the effects of traditional disinfection methods on ARGs have their own disadvantages. Tea polyphenols have attracted more and more researchers’ attention as a green, efficient and non-disinfection by-products disinfectant. The effect of the ozone–tea polyphenols disinfection process on ARGs in filtered effluent of waterworks was analyzed by using metagenomic sequencing. The result shows that the ozone–tea polyphenols disinfection process is suitable for specific raw water containing more tetracycline, sulfonamide, β-lactam, and aminoglycoside resistance genes, and the removal rate of total resistance genes in water is higher than the traditional disinfection process. The effect of the ozone–tea polyphenols disinfection process on ARGs is to reduce the transfer of ARGs by destroying ARGs molecules and inhibiting the proliferation of ARGs host cells. As an assistant disinfectant, tea polyphenols have significance for the ability to remove ARGs during traditional disinfection.

The effect of sedimentation by chemical coagulants and the rapid sand filters on algal removal at drinking water treatment plants in Egypt

BackgroundThe Nile River included diverse phytoplankton compositions belonging to five main phytoplankton categories. Algae have been classified and identified through comparative morphology.ResultsThe Pyrrophyta, Charophyta, Cyanophyta, Chlorophyta, and Bacillariophyta were presented through the full period of investigation with 1, 3, 14, 23, and 28 species, respectively. Therefore, it may be important to note that diatoms were recorded as an abundant group in all investigated samples. The numbers of diatoms ranged between 1.45 × 106 and 1.18 × 107 Organism/l, this was followed by green algae that ranged from 7.0 × 105 to 1.22 × 106 Organism/l. While the lowest count of blue-green algae was ranged between 1.6 × 105 and 7.03 × 105 Organism/l. The treatment of Nile water using two chemical coagulants "aluminum sulfate (Al2(SO4)3⋅16H2O) and aluminum oxide (Al2O3)" removed algae by about 85% and 90%, respectively. As for, the Cyanophyceae species, they were removed completely in treated water using the sedimentation, filtration, and chlorination process. The sedimentation basins removed from 20 to 100% of the total algal count while the rapid sand filters removed from 65 to 100% of the total algal count during the water treatment that depends on the species of algae.ConclusionsThis study concluded that the removal of algae from the Nile water may be more or less easy depending on the nature of the prevailing algal group. Water treatment plants must modify alum and chlorine doses in their water treatment processes according to the count and species of the algal groups, to provide an aesthetically acceptable and biologically safe water supply.

Microseira wollei and Phormidium algae more than doubles DBP concentrations and calculated toxicity in drinking water

Warm weather and excess nutrients from agricultural runoff trigger harmful algal blooms, which can affect drinking water safety due to the presence of algal toxins and the formation of disinfection by-products (DBPs) during drinking water treatment. In this study, 66 priority, unregulated and regulated DBPs were quantified in chlorinated controlled laboratory reactions of harmful algae Microseira wollei (formerly known as Lyngbya wollei) and Phormidium using gas chromatography (GC)-mass spectrometry (MS). Live algae samples collected from algae-impacted lakes in South Carolina were chlorinated in both ultrapure water and real source waters containing natural organic matter. DBPs were also measured in finished water from a real drinking water plant impacted by a Microseira bloom. Results show that the presence of Microseira and Phormidium more than doubles total concentrations of DBPs formed by chlorination, with levels up to 586 μg/L formed in natural lake waters. Toxic nitrogen-containing DBPs also more than doubled in concentration, with levels up to 36.1, 3.6, and 37.9 μg/L for haloacetamides, halonitromethanes, and haloacetonitriles, respectively. In ultrapure water, DBPs also formed up to 314 μg/L when algae was chlorinated, demonstrating their ability to serve as direct precursors for these DBPs. When environmentally relevant levels of bromide and iodide were added to chlorination reactions, total DBPs increased 144, 51, and 24% for drinking water reservoir, Lake Marion and Lake Wateree Microseira respectively and 29% for Phormidium. Iodo-DBPs, bromochloroiodomethane, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid were observed in finished water from a drinking water plant impacted by Microseira, and bromochloroiodomethane and dibromoiodomethane were observed in chlorinated ultrapure water containing algae, bromide, and iodide. Notably, total calculated cytotoxicity tripled in Microseira–impacted waters and doubled for Phormidium-impacted waters. Calculated genotoxicity doubled for Microseira-impacted waters and more than doubled in Phormidium-impacted waters. Haloacetonitriles were major drivers of calculated cytotoxicity in algae-impacted waters, while haloacetic acids were major drivers of calculated genotoxicity in algae-impacted waters. These results provide the most extensive assessment of DBPs formed from chlorination of algae-impacted waters and highlight potential impacts to drinking water and human health. Results from this study are particularly applicable to drinking water treatment plants that employ pre-chlorination, which can cause the release of algal organic matter (AOM) precursors to form DBPs.

Exposure to microcystin-LR in tropical reservoirs for water supply poses high risks for children and adults.

While the presence of microcystin-LR (MC-LR) in raw water from eutrophic reservoirs poses human health concerns, the risks associated with the ingestion of MC-LR in drinking water are not fully elucidated. We used a time series of MC-LR in raw water from tropical urban reservoirs in Brazil to estimate the hazard quotients (HQs) for non-carcinogenic health effects and the potential ingestion of MC-LR through drinking water. We considered scenarios of MC-LR removal in the drinking water treatment plants (DWTPs) of two supply systems (Cascata and Guarapiranga). The former uses coagulation/flocculation/sedimentation/filtration/disinfection, while the latter has an additional step of membrane ultrafiltration, with contrasting expected MC-LR removal efficiencies. We considered reference values for infants (0.30μg L-1), children/adults (1.60μg L-1), or the population in general (1.0μg L-1). For most scenarios for Cascata, the 95% upper confidence level of the HQ indicated high risks of exposure for the population (HQ > 1), particularly for infants (HQ = 30.910). The water treatment in Cascata was associated to the potential exposure to MC-LR due to its limited removal capacity, with up to 263days/year with MC-LR above threshold values. The Guarapiranga system had the lowest MC-LR in the raw water as well as higher expected removal efficiencies in the DWTP, resulting in negligible risks. We reinforce the importance of integrating raw water quality characteristics and treatment technologies to reduce the risks of exposure to MC-LR, especially for vulnerable population groups. Our results can serve as a starting point for risk management strategies to minimize cases of MC-LR intoxication in Brazil and other developing countries.

Which pre-oxidation methods to choose? From perspective of DBPs formation and toxicities reduction

Pre-oxidation have been widely applied in drinking water treatment plants with micro-polluted water as water sources. In this study, the effects of three commonly used oxidants (ozone, chlorine, and potassium permanganate) on disinfection by-products (DBPs) formation from micro-polluted water during subsequent chlorination and chloramination were investigated. Moreover, the toxicities of treated water were also compared. In addition, principal component analysis was applied to clarify the main components that contributed to DBPs generation. The results demonstrated that all the selected oxidants could reduce DBPs to some extent, but the species and amounts were quite different. Pre-KMnO4 greatly reduced haloacetic acid (HAAs) formation in subsequent chloramination; the removal rate reached up to 45.2%. Pre-HClO could produce trihalomethane (THMs) and HAAs directly, and its effect on DBPs reduction during subsequent disinfection processes was limited. Pre-O3 performed best on N, N-dimethyl nitrosamine (NDMA) reduction during subsequent chloramination; the corresponding removal rates were 49.7%. In addition, pre-O3 significantly reduced UV254 and SUVA. Pre-KMnO4 transferred more organic matter to cationic components (24%), while the highest polar component augmentation was observed during pre-HClO (15%). Based on the analysis of total toxicity of formed DBPs, pre-O3 performed best on toxicity reduction no matter subsequent chlorination or chloramination, which decreased by 25.8% and 46.4%, respectively. The principal component analysis showed that DBPs has a weak correlation with regular water quality parameters, but related with specific organic fractions. The results of this paper had significant guidance for the selection of pre-oxidation methods in drinking water treatment plants for this kind of water sources.

Drinking Water Treatment Plant Design for Administrative Capital in Egypt

Drinking Water Treatment Plant Design for Administrative Capital in Egypt

Evaluating the relative adsorption and biodegradation of 2-methylisoborneol and geosmin across granular activated carbon filter-adsorbers

This study investigated the relative contributions of adsorption vs. biodegradation towards 2-methylisoborneol (MIB) and geosmin removal in the granular activated carbon (GAC) harvested from six filter-adsorbers in three drinking water treatment plants in the Great Lakes region. Column tests using azide-treated (sterilized) and untreated GAC in parallel were used to isolate the two effects. It was identified that substantial MIB and geosmin biodegradation in the GAC was occurring in one location, and that GAC in some cases had significant adsorption capacity after as much as 9 years of operation. Four alternative biological parameters (adenosine triphosphate, esterase activity, phosphatase activity, and 14C-glucose respiration rate) were measured to quantify the biological activity of the GAC, and 14C-glucose respiration rate was identified to be a potential indicator for GAC biodegradative capacity in terms of MIB, geosmin, and dissolved organic carbon. Several potential MIB and geosmin biodegradation products were also identified using non-targeted screening analysis. By using the new tools identified in this study, we can begin to better understand where adsorption vs. biodegradation may predominate under real-world conditions (e.g., different temperatures, influent concentrations, and empty bed contact time), leading ultimately to more cost-effective use of GAC.

Influence of manganese oxide‐coated granular media on disinfection byproduct formation

AbstractThe objective of this study was to determine the influence of manganese oxide (MnOx) coated granular media on disinfection byproduct (DBP) formation for dissolved manganese (Mn(II)) and natural organic matter (NOM) concentrations typical in drinking water treatment (DWT). Instantaneous and 24‐h haloacetic acid and total trihalomethane concentrations of influent and effluent samples from two DWT plants, one using MnOx‐coated dual media (DM) filters and the other using second‐stage contactors for Mn(II) sorption by coarse MnOx‐coated ceramic media after DM filtration, were examined. Results showed that interaction with MnOx‐coated surfaces did not increase measured DBP concentrations. Observed increases in 24‐h DBP concentrations for the surface water plant were attributed to filter‐associated NOM, and not the MnOx coating. The findings of this study indicate that a second‐stage contactor – with MnOx‐coated media utilized for Mn(II) removal after a particle removal filter – does not increase DBP formation under typical treatment conditions.

Predicting the Distribution of Arsenic in Groundwater by a Geospatial Machine Learning Technique in the Two Most Affected Districts of Assam, India: The Public Health Implications.

Arsenic (As) is a well‐known carcinogen and chemical contaminant in groundwater. The spatial heterogeneity in As distribution in groundwater makes it difficult to predict the location of safe areas for tube well installations, consumption, and agriculture. Geospatial machine learning techniques have been used to predict the location of safe and unsafe areas of groundwater As. We used a similar machine learning technique and developed a habitation‐level (spatial resolution 250 m) predictive model to determine the risk and extent of As >10 μg/L in groundwater in the two most affected districts of Assam, India, with an aim to advise policymakers on targeted interventions. A random forest model was employed in Python environments to predict the probabilities of As at concentrations >10 μg/L using intrinsic and extrinsic predictor variables, which were selected for their inherent relationship with As occurrence in groundwater. The relationships between predictor variables and proportions of As occurrences >10 μg/L follow the well‐documented processes leading to As release in groundwater. We identified potential As hotspots based on a probability of ≥0.7 for As >10 μg/L, including regions not previously surveyed and extending beyond previously known As hotspots. Of the total land area (6,500 km2), 25% was identified as a high‐risk zone, with an estimated 155,000 people potentially consuming As through drinking water or cooking food. The ternary hazard probability map (showing high, moderate, and low risk for As >10 μg/L) could inform policymakers on establishing newer drinking water treatment plants and providing safe drinking water connections to rural households.

Statistical assessment for performance of Al-Mussaib drinking water treatment plant at the year 2020

Abstract Assessment of water quality is a major step in the water industry to ensure the suitability of water for human use. In this study, statistically evaluate the quality of raw and treated drinking water of the Al-Mussaib drinking water treatment plant, Babylon city, Iraq, from January to December 2020. Additionally, the water quality of treated water was assessed according to World Health Organization (WHO) and Iraqi standards for drinking water. The results showed the plant has a good efficiency in removing the studied parameters, such as alkalinity, calcium and hardness. It is noteworthy to mention that although the measured concentrations/levels met the WHO and Iraqi standards, they were higher than the favourable limits. For example, the measured sulphate concentration in the produced water was 248 mg/L, which is higher than the favourable concentration (200 mg/L) (WHO). The statistical analysis indicated significant differences between the quality of raw and treated water (p-value &amp;lt;0.05) in terms of turbidity, hardness, magnesium and dissolved solids concentrations, but there was no significant difference (p-value &amp;gt;0.05) in terms of alkalinity, pH, calcium and sulphates concentrations. The results of this work could be useful for water authorities and decision-makers in Iraq and national and international environmental agencies.

Target and suspect screening for biocides in drinking water resources of Honduras

Abstract The objective of this research was to explore biocide occurrence in drinking water resources of Honduras. We collected 46 samples from seven drinking water treatment plants (DWTPs) in Honduras during eight sampling events between October 2018 and August 2019. We used high-resolution mass spectrometry to quantify the concentrations of 55 target biocides and estimate the abundance of four priority suspect biocides and five additional high-abundance biocides. We measured 30 of the target biocides, one of the priority suspect biocides, and all five of the high-abundance biocides in at least one of the samples. No correlation was observed between the overall extent of agriculture and biocide occurrence. However, bean production was strongly and significantly correlated with the biocide mixture complexity, as well as with concentrations of aminobenzimidazole and abscisic acid. Biocide mixture complexity was higher during the rainy season than during the dry season, but biocide concentrations were lower during the rainy season. Finally, we found that existing DWTPs are not consistently effective at removing the target biocides. These data represent the first known broad survey of bioicides in drinking water resources of Honduras and demonstrate the need for further study to better understand and manage biocide occurrence.