Drinking Water Supply Research Articles

Recycling of puffed polystyrene beads waste as a low‐cost antifouling ultrafiltration membrane for water purification

AbstractCurrently, plastic waste, limited water resources, and water contamination are challenges of universal concerns. Recycling plastic waste as a membrane for water/wastewater treatment is of great significance from the perspective of environmental protection and safe drinking water supply. In this study, we used for the first time the puffed polystyrene beads waste (PPSBW) as a basic material for the fabrication of an ultrafiltration membrane and Pluronic F127 (PF127) as a plasticizer and hydrophilizing agent. Different ratios of PF127 were added to the casting solution, and the characteristics of the blank PPSBW and PF127‐modified membranes (PPSBW‐PF127) were evaluated in detail. The addition of PF127 increased the turbidity and viscosity of the casting solution, decreased the contact angle (increased the hydrophilicity), decreased the pure water flux, and increased the rejection of humic acid. The PPSBW membrane with 3 wt.% of PF127 showed the highest antifouling properties, the highest cleaning efficiency, and kept a satisfactory BSA and pure water flux for 4 runs. Overall, PF127 improved the hydrophilicity, organic matter separation, and enhanced the antifouling properties of the PPSBW‐derived membrane.Highlights Renew flow: Repurposing plastic waste as a UF membrane was successfully achieved. The PPSBW‐PF127 membrane was applied for wastewater treatment. Mechanical properties showed reasonable response by adding Pluronic F127. The PPSBW‐PF127 membrane demonstrated a significant rejection and permeability. The PPSBW‐PF127 membrane showed the highest antifouling and cleaning properties.

Delineation and Mapping of Groundwater Quality Assessment in Salem District, Tamil Nadu, India using GIS Techniques

Groundwater is a crucial natural resource with significant economic importance, supporting industrial activities, irrigation, and drinking water supplies. However, its extensive use for these purposes depletes water tables, which diminishes its future availability and leads to increased salinity, stream depletion, and land subsidence. A study was conducted to evaluate and map groundwater quality across different blocks in Salem district viz., Salem, Gangavalli, Thalaivasal, Attur, Pethanaickenpalayam, Valappady, Ayothiyapattinam, Yercaud, Panamarathupatty, Veerapandi, Edappadi, Sankari, Kadayampatti, Kolathur, Konganapuram, Magudanchavadi, Mecheri, Nangavalli, Omalur, and Tharamangalam. Sampling was conducted in February 2024, during which a total of 200 samples were collected and examined for pH, electrical conductivity, cations like Ca2+, Mg2+, Na+ and K+, anions like CO32-, HCO3-, SO42-, and Cl-. Based on the ionic concentration, the water quality parameters are derived such as Sodium Adsorption Ratio(SAR) and Residual Sodium Carbonate (RSC). The pH and EC values were ranged from 7.08 to 8.58 and 0.74 to 2.75 dS/m, respectively. The residual sodium carbonate (RSC) concentration ranged from -7.3 to 10.1 meq/L, while the sodium adsorption ratio (SAR) ranged from 0.7 to 9.7 meq/L. According to the CSSRI, Karnal Water Quality Classification, approximately 66.5 % of the samples fit into the good quality category, approximately 13% of the samples fit into the alkaline water category, and 20% of the samples fit into the saline water category in the Salem district. Using this classification, thematic maps depicting groundwater quality in the Salem district were generated with ArcGIS software. The study concludes that the majority of the samples are classified as good-quality water, while saline and alkali water emerge as the next major concern. Using this saline water for irrigation can change the soil's physical properties and lower agricultural productivity. Thus, it's crucial to apply soil amendments like gypsum and provide proper drainage to avoid long-term soil damage.

Assessment of diffusive recharge at regional scale in karst systems, Amazon basin, Ecuador

Karst systems play a crucial role in drinking water supply and biodiversity. Therefore, their comprehensive characterization of their recharge mechanisms is essential for safeguard water resource quality and sustainable management. This study utilizes the open-access thematic cartography of Ecuador to analyze the lithological, geomorphological, and hydrographic boundaries of groundwater karst systems. Then, employing the APLIS method, the diffusive recharge for each system is calculated. As a result, five hydrogeological karst systems and twelve small isolated karst bodies were delineated within the Amazon Region of Ecuador, collectively occupying a total area of 11112 km2. The effective infiltration of precipitation within these systems was found to vary between 11.11% and 77.11%, with a predominant low infiltration range (20%-40%) covering 48% of the karst area. One of the multiple parameters used in water balance calculations is defined by this research, serving as the initial step in creating conceptual models for evaluating karst aquifer systems in Ecuador from a hydrological perspective. The findings not only offer insights into the vulnerability and characteristics of these systems but also establish the foundation for informed decision-making in sustainable groundwater resource management and protection efforts.

Determination of Average Water Demand and Diurnal Consumption Pattern for a Multifamily Apartment Complex in Peshawar

Abstract: Accurately estimating and understanding domestic water demand and consumption patterns is essential for the efficient planning and management of drinking water supply systems. Traditional methods for estimating water demand are labor-intensive and often rely on assumptions. To overcome these limitations, this study employed a novel approach using highprecision data loggers to monitor water levels continuously in rooftop tanks at 5-minute intervals within a residential apartment complex in Peshawar, Pakistan. The findings indicate that per capita water consumption varies between 97 and 209 liters per capita per day (lpcd), with an average consumption of 173 lpcd. This methodology offers enhanced accuracy in quantifying water usage, providing a robust alternative to conventional estimation techniques.

Advancing mechanistic understanding of cohesive sediment transport: Integrating flume experiments, field measurements, and modelling approaches in a gravel-bed river

Gravel-bed rivers draining mountainous forested headwater regions are critically important for drinking water supply and ecological integrity. These rivers, however, have been increasingly impacted by intensifying anthropogenic and natural (especially climate change exacerbated) landscape disturbances that commonly increase hillslope/channel connectivity and the delivery of cohesive sediment (<63 μm) and associated pollutants. Despite the known deleterious threats of excess cohesive sediments, there is still limited understanding of their transport and intra-gravel storage due to the complexities of such processes. Accordingly, the objectives of this study were to: i) calibrate and validate a semi-empirical cohesive sediment transport model (RIVFLOC) using the observations from flume experiments; ii) estimate the intra-gravel storage capacity for cohesive sediment with the calibrated model based on the field dataset (collected in two field campaigns between 2019 and 2021), and; iii) investigate mechanisms of cohesive sediment transport dynamics in this gravel-bed river, identifying knowledge gaps and areas for future research. Our results showed that despite the increased floc settling velocity, deposition was hindered by turbulent flow fields. The model predicted that ~60 % of upstream cohesive sediment would ingress within the 10 km study reach due to the flow interaction with the gravel-bed. Despite the agreement between flume and field observations on ingress rates and preferential ingress of coarser (~100 μm) flocs, notable differences were observed between modelled and field datasets, highlighting unknowns regarding cohesive sediment exfiltration without framework mobilization. This study uniquely integrates field measurements, flume experiments, and modelling strategies to evaluate the transport and fate of cohesive sediment in a gravel-bed river. Accordingly, our findings advance current knowledge on the mechanistic understanding of cohesive sediment transport and highlight future research directions.

Tracking Microplastics Contamination in Drinking Water Supply Chain in Haikou, China: From Source to Household Taps

The presence of microplastics (MPs) in aquatic environments has become a significant global concern due to their potential adverse effects on human health. This study aimed to investigate the contamination of MPs throughout the drinking water supply chain in Haikou City, China, and to conduct risk assessments regarding the relationship between MPs contamination and human health. The results revealed that the abundance of MPs in raw, treated, and tap water was 0.6 ± 0.6, 5.2 ± 2.7, and 1.2 ± 1.1 particles·L−1, respectively. Fragments were identified as the most prevalent shape across all samples, with the size category of 20–50 μm showing the highest abundance of MPs. Among the 11 types of polymers identified, polyethylene and polypropylene accounted for 50% and 29%, respectively. The potential risk index values were significantly higher for treated water (370.26) and tap water (303.85) compared to raw water (13.46), suggesting that plastic pipes may be a key contributor to MPs contamination in drinking water. Therefore, efforts should be directed toward developing pipes with low release rates of MPs, as well as improving detection methods for smaller particles and accurately assessing associated risks.

Trihalomethane Formation Potential at the Barekese Water Treatment Plant and the Related Cancer Risk to Consumers in the Kumasi Metropolis of Ghana

The prevalence of disinfection by-products in drinking water supplies is a global concern due to their carcinogenicity. However, the monitoring of DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water supplies is non-existent in many developing Asian, South American, and African countries. The formation of THMs during disinfection arises from a reaction between the disinfectant and natural organic matter in the water, particularly, dissolved organic carbon (DOC). This reaction is hastened by increases in temperature, high levels of disinfectant doses or residual, elevated water pH, long disinfection contact times, and high DOC concentrations. However, the inclusion of a granular activated carbon adsorption process in the water treatment process is the most effective method for the removal of the main precursor (DOC) for the formation of THMs in treated water. The Barekese WTP, which disinfects with chlorine, has no adsorption process for DOC removal, and supplies over 80% of pipe-borne water to the city of Kumasi in Ghana, was assessed for the THM formation potential (THMFP). A THM predictive model was used to determine the potential THM concentration in the final water. The THMFP at the Barekese WTP ranged between 22.42 and 38.94 µg/L, which was below the 100 µg/L threshold set by the WHO. The lifetime average daily doses were 3.9494 × 10−4 µg/Kg/d and 3.9294 × 10−4 µg/Kg/d for male and female consumers, respectively. The lifetime integrative cancer risks associated with consumption of the water were 1.817 × 10−5 and 1.808 × 10−5 for males and females, respectively. The cancer risk posed was acceptably low. However, direct measurement of DBPs is required to corroborate these findings and verify the cancer risk posed to the consumers of treated water from the Barekese WTP to inform policies, regulations, public health interventions, and investment.

Main challenges and measures taken by public health institutions in response to war in Kyiv Region

Abstract Background The establishment of martial law due to Russia’s military aggression against Ukraine led to specific adjustments in the functioning of the Centers for Diseases Control and Prevention (СDС). The negative impact of hostilities is determined by the increased morbidity rate of communicable and non-communicable diseases, insufficient supply of safe drinking water and food to damaged sites, inadequate living conditions, etc. Objectives The purpose of the work was to create an effective system for responding to biological, chemical and radiation hazards and eliminating the consequences of an emergency situation in the realities of martial law. Methods We used the most common methods, namely descriptive, statistical, microbiological and сhemical laboratory tests. Results The activities of the CDC under martial law include daily monitoring studies of environmental objects. The epidemic situation of acute intestinal infection (AII) and other communicable diseases (CD) is constantly analyzed. The Kyiv Oblast CDC became the basic institution for the implementation of the ‘pilot project’ in the direction of sanitary and epidemic assessment and monitoring of environmetal objects in 188 de-occupied areas. The main public health risks were identified: providing the population with high-quality drinking water; low immunization rate of the population; sites for the location of internally displaced persons; natural foci of especially dangerous diseases, such as tularemia, leptospirosis, infection fevers, etc. In 2022, the overall level of CD in the Kyiv region decreased by 44.0% from 2021. The most common nosologies were acute respiratory viral infections and influenza (98.9%), AII (42.4%), tuberculosis (15.3%), Lyme disease (15.3%), and viral hepatitis (14.2%). Conclusions Based on the research conducted, mechanisms have been developed for responding to hazards of various origins by public health institutions, including risk assessmant and laboratory studies. Key messages • The main focus of the Centers for Diseases Control and Prevention is aimed at effective response to hazards of various origins in order to ensure public health under martial law. • Risk assessment in de-occupied territories has become an important tool for identifying correct approaches to prevent negative consequences for public health.

Best Management Practices to Mitigate Contamination of Karstic Aquifers from Emergency Fire-Control Runoff

We propose best management practices to increase karstic aquifer drinking water supplies’ resilience to potential hazardous material impacts where first responders and public safety officials suspect emergency firefighting runoff has entered the subsurface in the aquifer recharge zone. Karstic aquifers are unique because of their direct openings to the land’s surface, which allows contaminants in runoff or other surface waters to rapidly enter the subsurface and impact aquifer water quality. In the United States, 20% of the land surface is karst, and about a third of the groundwater used for drinking comes from karstic aquifers. Proposed best management practices emphasize on-site, real-time evaluation of the transport and fate of HAZMAT that may enter the subsurface and focus on water quality sampling, runoff and groundwater flow modeling, nontoxic dye tracing, and related studies for use in planning before and during an event and after emergency response has ended. We recommend best management practices for evidence-based screening of high-risk sites to facilitate placement of hazardous material sampling devices and emergency responder deployment. The best management practices, tools, curricula, and training described combine with earlier work by the authors to provide a comprehensive menu of actions to (1) help first responders prevent or limit flushing of hazardous material into a karstic aquifer; (2) help emergency management officials understand the consequences of contamination and issue data-driven geographically focused health and safety risk communications; and (3) help provide health and safety officials with relevant science- and data-based information that can help mitigate human and environmental health risks.

“And Justice for All”: Modifying the Ninth Circuit’s &lt;em&gt;Feres&lt;/em&gt; Doctrine Test to Reduce Service Member Inequity

In 1946, the Federal Tort Claims Act (FTCA) waived what was once absolute: federal sovereign immunity for government-caused torts. Nevertheless, the Supreme Court’s Feres doctrine declines to extend the FTCA’s immunity waiver to certain tort claims of military service members. The doctrine precludes petitioners who have suffered an injury incident to their military service from bringing a negligence claim against the government. Its origins are not without controversy and modern courts often have trouble applying it in an equitable manner. In 2021, for example, the U.S. Navy negligently contaminated the drinking water supply of thousands of civilians and service members on the island of Oahu. Although recent case law applying the FTCA to drinking water-related torts indicates a willingness to allow some of these claims to proceed, that willingness has not been extended to service members due to the Feres doctrine. This Note argues that the Feres doctrine is inequitable because it excludes service members’ injuries in an overbroad manner. Further, this Note proposes a modified Feres test based on the Ninth Circuit’s interpretation of the doctrine to promote equity and applies it to the Navy’s actions on Oahu.

The Influence of Fluoride Ions on the Forms of Lanthanide Migration in Natural and Polluted Waters of the Lovozero Massif (The Kola Peninsula)

A comprehensive study (monitoring, thermodynamic modeling) of natural and anthropogenically polluted waters of the Lovozero Massif has been carried out. A thermodynamic study of the weathering of the Lovozero Massif within the “water-rock-atmosphere” system at a temperature of 5 °C showed that the elements contained in the rocks of the studied massif influence the formation of the chemical composition of natural waters. It has been established that an increase in the degree of “water-rock” interaction leads to an increase in the concentrations of F−, Cl−, SO42−, and HCO3− in the solution. This affects the mobility of lanthanum, cerium, and other elements due to the formation of complex compounds with them. The relatively high content of fluorine, phosphorus, and HCO3− (weak and medium acids) in the solution promotes the dissolution of silicates while Si, Al, and P are released into the solution. Monitoring of water from a flooded mine in which there is an increase in the degree of interaction of water with rock showed higher pH values for the concentrations of Na, HCO3−, F−, P, Al, Si, V, U, La, and Ce. The conclusions are relevant in the context of the use of groundwater for drinking water supply purposes. The obtained information is useful to evaluate the health of the population of the region under study.

Predictions of groundwater PFAS occurrence at drinking water supply depths in the United States.

Per- and polyfluoroalkyl substances (PFAS), known colloquially as "forever chemicals", have been associated with adverse human health effects and have contaminated drinking water supplies across the United States owing to their long-term and widespread use. People in the United States may unknowingly be drinking water that contains PFAS because of a lack of systematic analysis, particularly in domestic water supplies. We present an extreme gradient boosting model for predicting the occurrence of PFAS in groundwater at the depths of drinking water supply for the conterminous United States. Our model results indicate that 71 to 95 million people in the conterminous United States potentially rely on groundwater with detectable concentrations of PFAS for their drinking-water supplies prior to any treatment.

Understanding the impact of deep structures on the hydrological setting of the Eastern Bahira Basin in Morocco using combined geophysical analysis of gravity, seismic, and electrical resistivity data

In arid regions like the Eastern Bahira Basin, communities mainly rely on groundwater for drinking and irrigation. However, efficiently managing these vital resources requires a deep understanding of the underlying aquifers’ structure and identifying the most suitable areas for exploitation. This presents a significant challenge for the success of water supply and irrigation programs in the Eastern Bahira Basin. This study is based on an integrative approach, combining Electrical Resistivity Tomography data, with the compilation and reinterpretation of pre-existing seismic, gravimetric and vertical electrical sounding data. This approach is based on compiling old gravimetric data and applying advanced processing techniques to determine the horizontal gradient maxima, which helps highlight the major structural alignments in the basin. Furthermore, the approach utilizes seismic data in order to enhance understanding of the deep structure of the basin, reinterpreting it in light of recent drilling data. The interpretation of the gravimetric and seismic data has also been validated by the results of vertical electrical soundings and electrical tomography that we recently acquired in the Eastern Bahira basin. The outcomes of this research provide new insights into the deep structure of the Eastern Bahira Basin and suggest the most promising hydrogeological prospects, thereby contributing to the success of the ongoing drinking water supply and irrigation program in the Eastern Bahira Basin.

Emergency Preparedness for Waterborne Diseases in the Wake of Floods in Northern Cameroon: A Call for Immediate Action

Severe flooding in Northern Regions of Cameroon (Far North, North and Adamawa Regions), triggered by torrential rains, has led to widespread displacement, destruction of infrastructure, and significant disruptions in essential services, particularly water, sanitation, and healthcare. This article, issued by public health researchers from Science For Life Foundation and Pinnacle University Institute, highlights the heightened risk of waterborne diseases following the recent floods and underscores the urgent need for enhanced emergency preparedness and response measures. Floods create conditions conducive to the spread of diseases such as cholera, typhoid fever, dysentery, and viral hepatitis by contaminating drinking water supplies with sewage and waste. Vulnerable populations, including children, pregnant women, the elderly, and those with pre-existing health conditions, are at increased risk. Overcrowding in temporary shelters further exacerbates the potential for disease outbreaks. The impact of climate change is intensifying the frequency and severity of such flooding events, making timely and effective intervention critical. This article reviews best practices for preventing and mitigating waterborne disease outbreaks, offering guidance to government authorities, health agencies, humanitarian organizations, and local communities. It aims to catalyze immediate action to safeguard public health and prevent a major crisis in the aftermath of the flooding Keywords: Waterborne Diseases, Flooding, Emergency Preparedness.

Mitigation of Fluoride Contamination in Drinking Water Supply Sources by Adsorption Using Bone Char: Effects of Mineral and Organic Matrix

This study focused on fluoride (F−) contamination of water sources in Bahimi village, Cameroon. After the first investigation, results revealed that all water samples collected had elevated concentrations of fluoride ions (2.3 ± 0.1) mg/L to (4.5 ± 0.2) mg/L above the WHO guidelines (less than 1.5 mg/L). To mitigate the F− levels, the use of bone char (BC) as an adsorbent material was proposed and its performance was tested. BC was prepared from bovine bones at different calcination temperatures (350 °C, 450 °C, 550 °C and 650 °C) and residence times (1 h and 2 h). The prepared materials were characterized in detail by SEM/EDS, BET, FTIR, and XRD. The BET findings indicated that the surface area of BC samples decreased with increasing calcination temperature and residence time. At a lower heating temperature and holding time (350 °C, 1 h), the prepared BC exhibited a higher specific surface area (112.3 ± 0.3) m2/g and adsorption capacity for F− in the sampled water. Also, the batch adsorption experiments showed that the optimized adsorbent dose of 8 g/L facilitates the reduction in the F− level of the sampled water below the acceptable limit level (1.5 mg/L) within 5 min of treatment. The presence of Ca2+ and Mg2+ in natural water has a positive effect on the removal of F− in BC resulting in a high adsorption performance range of (72.5 ± 1.4)% to (80.3 ± 0.6)%. It was found that the adsorption of Ca2+ on the BC surface occurs via cation exchange with Na+. However, an increase in dissolved organic carbon (DOC) in the treated water limited the application of BC. Overall, the study presented a cost-effective adsorbent for the removal of this recalcitrant ion in the water source.

Microalgae to remove pharmaceutical and personal care products (PPCPs) from wastewater

Substances used for medicinal, cosmetic, hygiene, and health care objectives are included in the category of pharmaceuticals and personal care products (PPCPs). They are a major source of public concern because of their ubiquitous manufacturing, usage, and careless disposal of expired products into the environment. Many PPCPs, including antibiotics, analgesics, endocrine disruptors, and microbial/disinfecting agents, are commonly detected in freshwater systems, groundwater, and wastewater treatment effluents in amounts ranging from nanograms per liter to milligrams per milliliter. Additionally, these compounds frequently show persistence and accumulate in biological tissue, eventually finding their way into crops, vegetables, and drinking water supplies. Because many PPCPs are known to have the ability to upset ecosystems and/or provide health hazards, they are categorized as “emerging contaminants.” The research on the occurrence, fate, and possible health and environmental hazards related to PPCPs in both aquatic and terrestrial habitats is thoroughly reviewed in this work. It also covers reported cases of danger or health concerns in humans, although a full assessment may not be possible given the limitations of the data at hand. This review aims to provide a comprehensive and well-focused overview of the current understanding of bioremediation strategies for the removal of pharmaceuticals and personal care products (PPCPs), with an emphasis on the application of macroalgae, microalgae, and aquatic macrophytes. It examines the physicochemical properties of PPCPs and their potential risks to environmental and human health. Additionally, the review explores the potential and challenges associated with the broader application of biotechnologies employing algae and aquatic macrophytes. This includes research efforts to correlate the operational parameters of these biotechnologies with the primary mechanisms responsible for PPCP removal. In conclusion, algae and macrophytes present promising, eco-friendly solutions for wastewater treatment, significantly contributing to the mitigation of PPCP contamination.

Enhanced efficiency of water purification plant by combined riverbank filtration

Water shortages occur due to several factors, with drought being one of the biggest drivers. Another major environmental issue related to the contamination of freshwater systems worldwide is thousands of micropollutants, although they generally occur at low concentration levels. The provision of safe drinking water to the population in rural developing nations remains a problem, in particular when surface water and shallow wells or non-watertight headworks wells serve as sources of drinking water. Dramatically changing raw water qualities, floods and high rainfall events anthropogenic pollution, lack of electricity supply in developing regions demand new and adapted solutions for treatment and rendering water safe for distribution. Our study aimes to find another source of water supply using riverbank filtration (RBF). The RBF is a water treatment method that removes water from rivers by pumping wells into a nearby alluvial aquifer. Several physical, chemical, and biological processes that occur underground improve the quality of surface water and eliminate the need for traditional potable water treatment. Additional treatment techniques in this process include biological degradation, sorption, and filtration. Physical, chemical, and microbiological variables were used to assess the effectiveness of the RBF system in Upper Egypt. Our study proposes a workable water treatment strategy that replaces RBF treatment or pretreatment technique for high-quality Nile water to eliminate or reduce surface water pollutants without the use of chlorine.

Cleaning Up Metal Contamination after Decades of Energy Production and Manufacturing: Reviewing the Value in Use of Biochars for a Sustainable Future

The lasting impact of ancestral energy production operations and global manufacturing has not only generated substantial CO2 emissions, but it has also led to the release of metal-based pollutants into Earth’s water bodies. As we continue to engineer, mine (coal and metals), and now bore into geothermal wells/fracking sites for alternative energy sources, we continue to contaminate drinking water supplies with heavy metals through infiltration and diffusion, limiting progress towards achieving Sustainable Development Goals 3 (Sustainable Development Goal 3: Good health and well-being), 6 (Sustainable Development Goal 6: Clean water and sanitation), 14 (Sustainable Development Goal 14: Life below water), and 15 (Sustainable Development Goal 15: Life on land). This review shows how the research community has designed and developed mesoporous biochars with customizable pore systems, as well as functionalized biochars, to extract various heavy metals from water sources. This article investigates how biochar materials (non-activated, activated, functionalized, or hybrid structures) can be adapted to suit their purpose, highlighting their recyclability/regeneration and performance when remediating metal-based pollution in place of conventional activated carbons. By utilizing the wider circular economy, “waste-derived” carbonaceous materials will play a pivotal role in water purification for both the developed/developing world, where mining and heavy manufacturing generate the most substantial contribution to water pollution. This review encompasses a wide range of global activities that generate increased heavy metal contamination to water supplies, as well as elucidates emerging technologies that can augment environmental remediation activities, improving the quality of life and standard of living for all.

Safety and security of household water purifiers against pathogenic microbial contamination and bio-risk evaluation of their microbial community structures

Household water filters, particularly point-of-use systems, are crucial to ensure safe drinking water consumption by eliminating microbial contaminants. This study evaluated the efficacy of three types of water purifiers (ultrafiltration [UF], nanofiltration [NF], and reverse osmosis [RO]) against microbial contamination. In our experiments, Escherichia coli and bacteriophage MS2 were used as two microbial indicators in daily household settings to track the spatial and temporal profiles of their behavior from the filter inlets to in-UF, NF, and RO water purifiers, and then to effluents. The results showed that both NF and RO water purifiers removed 100 % of the indicator organisms. The UF water purifier achieved 100 % removal of E. coli, but the removal of MS2 phage was poor. The presence of coexisting ions and natural organic matter in tap water can significantly affect the behavior of MS2 phages during the water treatment process. Their presence reduces the charge repulsion effect of the UF membrane on the MS2 phage as well as promotes the migration of the MS2 phage on the post-activated carbon cartridge that was placed in the last unit of the water purifier system, which could increase the pathogen transmission risks in drinking water supplies. The bacterial community structures of the cartridge materials and cartridge effluents from each unit were analyzed by 16S rRNA gene sequencing, which revealed distinct microbial profiles of the different purifiers. Environmental conditions such as pH, nutrient availability, materials, and operational parameters can affect the composition of bacterial communities. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) was used to examine the surface morphology of the membranes after they were exposed to water contaminants, which demonstrated that the inherent differences in the membrane structure influenced the retention of pollutants and microorganisms on the surfaces. In summary, this study demonstrates that both NF and RO water purifiers can significantly reduce the presence of various enteric and opportunistic pathogenic bacteria in drinking water, leading to safer potable water, whereas UF water purifiers may have certain risks owing to their UF membranes and post-activated carbon. In addition, secondary microbial contamination may be introduced by the post-activated carbon units of water purifiers, especially after long-term usage. Therefore, we concluded that addressing the secondary microbial pollution caused by post-activated carbon after prolonged use and long-term shutdown is essential for maintaining the safety and quality of drinking water.

Assessing the influence of environmental variables on energy efficiency changes in the provision of drinking water services

Within the context of the water-energy nexus in drinking water provision, it is crucial to evaluate temporal shifts in energy efficiency. Utilizing the Stochastic Nonparametric Envelopment of Data (StoNED) approach, this research estimates longitudinal variations in the energy efficiency of drinking water services integrating multiple environmental variables. The analysis, conducted in England and Wales from 2008 to 2020, indicates that the source and quality of raw water, as well as population density, influenced the energy performance of water utilities. Quantitative findings evidenced marked disparity in energy efficiency among different companies, with an average efficiency of 0.617 and a range from 0.437 to 0.944. The dynamic assessment indicates an average annual enhancement of 1.1% in the sector, predominantly propelled by technical advancements (0.9%) rather than by improvements in efficiency (0.2%). This study emphasizes the critical need for bespoke policies and incentives to boost energy efficiency and support sustainable urban water management.