Drinking Water Treatment Systems Research Articles

TiO2-Coated Meltblown Nonwoven Fabrics Prepared via Atomic Layer Deposition for the Inactivation of E. coli as a Model Photocatalytic Drinking Water Treatment System

The controlled manufacturing of semiconductor photocatalysts is crucial to their development for drinking water treatment. In this study, TiO2-coated meltblown nonwoven fabrics prepared via Atomic Layer Deposition (ALD) are applied for the inactivation of Escherichia coli (E. coli). It is observed that in the presence of an ultraviolet light-emitting diode (UV-LED) light source (255 nm), 1.35 log E. coli inactivation is achieved. However, exposure to catalyst-coated fabrics in addition to the light source resulted in >4 log E. coli inactivation, suggesting a much higher rate of hydroxyl radical formation on the surface, leading to cell death.

Membrane fouling control and contaminant removal during direct nanofiltration of surface water

Direct nanofiltration (NF) is an attractive separation process that produces high-quality drinking water without pretreatment. However, the propensity for membrane fouling is a considerable challenge. This study evaluated the potential of direct NF treatment of surface water using submerged flat-sheet (polyamide composite) NF membranes to achieve stable operation and high-quality water production. Direct NF treatment at a constant permeate flux of 5.0 L/m2h (NF270) and 2.5 L/m2h (NF90) was successfully continued for over 100 d with a monthly one-wipe sponge cleaning. Sponge cleaning eliminated the foulants on the NF270 membrane surface, thereby recovering the membrane permeability. Contrastingly, tight NF90 membranes did not exhibit significant changes in membrane permeability. The rejection of odorous compounds and other dissolved organic matter by the NF90 membrane was significant (>95 %), whereas those by the NF270 membrane considerably varied with the feed temperature. Further investigation suggested that the visible foulant on the membrane surface could be a porous cake layer mainly composed of constituents with a molecular weight of >300 Da, resulting in low hydraulic resistance. One-wipe sponge cleaning can readily detach fluffy cake layers. The results of this study suggest the viability of direct NF treatment as a low-energy advanced drinking water treatment system.

Long-term trial of a community-scale decentralized point-of-use drinking water treatment system

Two billion people lack access to safely managed drinking water services, many of these are in low/middle income countries where centralised systems are impractical. Decentralised point-of-use drinking water treatment systems offer alternative solutions in remote or resource constrained settings. The main aim of this study was to assess the long-term (3 year) operation and performance of a point-of-use drinking water treatment system (POU-DWTS). A biologically contaminated urban drainage pond was used as a water source and the quality of the produced drinking water was assessed over two independent trials. The decentralised POU-DWTS combined ultrafiltration membranes with disinfection from electrochemically generated hypochlorous acid (HOCl). The operational parameters, such as flow rate, free available chlorine and transmembrane pressure, were monitored in real-time and recorded via a remote monitoring system. Water quality from the source and treated water was assessed over two trial periods within the 3-year operational trial: an 11-week period at the start and a 22-week trial at the end. All water samples were assessed for a range of basic, chemical, microbiological and metal water quality parameters. The results demonstrate that the decentralised POU-DWTS is capable of continuously producing high quality drinking water when HOCl is continuously used to dose water prior to entering the ultrafiltration [UF] membranes. Over the 3-year operational study, the continuous dosing of HOCl pre-UF membranes resulted in stable permeability, indicating no occurrences of irreversible biofouling within the UF membranes and that good membrane ‘health’ was maintained throughout. As such, there was no need to replace the UF membranes nor undertake acid/alkaline chemical cleans at any point throughput the three-year study. The POU-DWTS continuously produced high quality drinking water, resulting in 6453 m3 of drinking water produced over the trial period, that met international water quality standards, at a community scale within the location studied.

Investigating the suitability of online flow cytometry for monitoring full-scale drinking water ozone system disinfection effectiveness

While online monitoring of physicochemical parameters has widely been incorporated into drinking water treatment systems, online microbial monitoring has lagged behind, resulting in the use of surrogate parameters (disinfectant residual, applied dose, concentration × time, CT) to assess disinfection system performance. Online flow cytometry (online FCM) allows for automated quantification of total and intact microbial cells. This study sought to investigate the feasibility of online FCM for full-scale drinking water ozone disinfection system performance monitoring. A water treatment plant with high lime solids turbidity in the ozone contactor influent was selected to evaluate the online FCM in challenging conditions. Total and intact cell counts were monitored for 40 days and compared to surrogate parameters (ozone residual, ozone dose, and CT) and grab sample assay results for cellular adenosine triphosphate (cATP), heterotrophic plate counts (HPC), impedance flow cytometry, and 16S rRNA gene sequencing. Online FCM provided insight into the dynamics of the full-scale ozone system, including offering early warning of increased contactor effluent cell concentrations, which was not observed using surrogate measures. Positive correlations were observed between online FCM intact cell counts and cATP levels (Kendall's tau=0.40), HPC (Kendall's tau=0.20), and impedance flow cytometry results (Kendall's tau=0.30). Though a strong correlation between log intact cell removal and CT was not observed, 16S rRNA gene sequencing results showed that passage through the ozone contactor significantly changed the microbial community (p < 0.05). Potential causes of the low overall cell inactivation in the contactor and the significant changes in the microbial community after ozonation include regrowth in the later chambers of the contactor and varied ozone resistance of drinking water microorganisms. This study demonstrates the suitability of direct, online microbial analysis for monitoring full-scale disinfection systems.

Estimation of Rotavirus Associated Diarrheal Disease Burden Amongst Primary School Children of Sindh

Introduction: Human Rotavirus Virus (HRV) is amongst the common enteric viral diarrheal diseases that indirectly or directly influence school-going children in low-income countries. Inadequate information exists on the presence of rotavirus, with reference to drinking water supplies of primary schools in Sindh, Pakistan. Aims &amp; Objectives: We estimated the risk of rotavirus-associated diarrhea through drinking water. The study further compared the HRV-associated risk of diarrheal disease by a type of water source. Place and Duration of Study: A cross-sectional survey was conducted in ten representative districts of Sindh from February 2022 to December 2022. The samples for drinking water were collected from primary schools of ten representative districts of Sindh. This study was a part of the WASH Project funded by USAID (USPCASW Seed Grant P-II) Material &amp; Methods: We selected 425 samples of drinking water from primary schools based on pre-defined selection criteria. We used a Quantitative Microbial Risk Analysis using indicator organisms, i.e., E. coli, to predict the possible health risks of rotavirus. Data was entered and analyzed on SPSS version 26. The graphs were developed using Arc GIS version 3. Morbidity and mortality were predicted using the Quantitative Microbial Risk Assessment (QAMRA) model. Results: Our data revealed that the highest daily risk of HRV-associated diarrhea amongst school children was 11 per 10,000 schoolchildren, resulting in 8.4% annual risk, and the minimum risk was estimated to be 1 in 10,000 children. The burden of diseases for rotavirus using the QAMRA model revealed the severity of the diarrhea. Majority of the children presented with mild diarrhea (86%) followed by severe, and the probability of death was less than &lt;1%. The daily risk of HRV infection was highest (estimated to be 7 and 11%) in pupils of Southern Sindh, with an annual risk of 17.4% to 40%. Conclusion: Our study concluded that the children in the primary schools of Sindh were exposed to poor drinking water quality. The surface water source poses the highest risk of HRV-related diarrhea to school children. Thus, it is highly recommended that point-of-use drinking water treatment systems be adopted. The water sanitation and hygiene (WASH) resources are interlinked, so each resource impacts the other; hence, schools urgently need to invest in providing adequate WASH facilities to stop enteric virus transmission through drinking water sources.

Controlling membrane fouling of nanofiltration using poly-aluminum chloride and Moringa oleifera coagulants

Membrane fouling control during nanofiltration (NF) of contaminated water sources is critical to establishing a cost-efficient advanced drinking water treatment system. This study aimed to evaluate the effect of pre-coagulation using Moringa oleifera (MO) or poly-aluminum chloride (PACl) coagulant on membrane fouling mitigation and final water quality during NF treatment of lake water. This study used four pre-coagulation methods: (i) full coagulation: coagulation-flocculation-sedimentation, (ii) coagulation and flocculation, (iii) rapid mixing alone, and (iv) without coagulant addition. The full coagulation with PACl or MO before NF treatment mitigated membrane fouling, and the optimum PACl or MO coagulant doses achieved the lowest membrane fouling. PACl or MO pre-coagulation with rapid mixing also mitigated membrane fouling, which suggested the potential use of inline coagulation. Turbidity in the coagulated water was the best indicator to predict the level of NF membrane fouling; thus, turbidity in the pre-coagulated water can be utilized to control NF membrane fouling. Regardless of the types of pre-coagulation methods, turbidity and dissolved organic matter concentrations in the NF permeate were equivalent. The results suggest that nanofiltration coupled with inline pre-coagulation can provide high-quality water.

Changes of putative pathogenic species within the water bacterial community in large-scale drinking water treatment and distribution systems

Although the management of microbes in drinking water is of paramount importance for public health, there remain challenges in comprehensively examining pathogenic bacteria in the water supply system at the species level. In this study, high-throughput sequencing of nearly full-length 16S rRNA genes was performed to investigate the changes of the water bacterial community in three large-scale drinking water treatment plants (DWTPs) and their corresponding distribution systems during winter and summer. Our findings revealed significant differences in the bacterial community structure between winter and summer water samples for each DWTP and its distribution management area (DMA). In the groundwater-fed DWTP, selective enrichment of mycobacterial species was observed in both seasons, and the subsequent DMA also exhibited strong selection for specific mycobacterial species. In one of the surface water-fed DWTPs, certain Legionella species present in the source water in winter were selectively enriched in the bacterial community after pre-oxidation, although they were susceptible to the subsequent purification steps. A variety of putative pathogenic species (n = 83) were identified based on our pathogen identification pipeline, with the dominant species representing opportunistic pathogens commonly found in water supply systems. While pathogen removal primarily occurred during the purification processes of DWTPs, especially for surface water-fed plants, the relative abundance of pathogenic bacteria in the DMA water flora was lower than that in the DWTP effluent flora, indicating a diminished competitiveness of pathogens within the DMA ecosystem.

Impact of phosphate addition on PFAS treatment performance for drinking water

AbstractAdding new unit operations to drinking water treatment systems requires consideration of not only efficacy for its design purpose but also costs, water quality characteristics, impact on overall regulatory compliance, and impact of other treatment unit operations. Here, pilot study results for ion exchange (IX) and granular activated carbon (GAC) are presented for a utility with both per‐ and polyfluoroalkyl substances (PFAS) and volatile organic contaminant removal needs. Specifically, the impact of upstream air stripping and phosphate addition on PFAS treatment performance was evaluated. Modeling was used to fit the IX and GAC pilot data and predict performance under different scenarios. GAC performance was generally consistent for treating water before or after the air stripper, but the addition of phosphate prior to air‐stripping resulted in a loss of 15%–25% capacity for some PFAS on IX media, demonstrating the need to consider the entire treatment train before implementing PFAS removal unit operations.

Improving conventional household greensand treatment for efficient Mn(II) removal from drinking water

Geogenic contaminants pose a global threat to ensuring access to safe drinking water. Manganese (Mn) is a naturally-occurring redox-active element which in its reduced form, Mn(II), is a widespread groundwater contaminant. Prolonged consumption of water containing high levels of Mn has been linked to adverse effects on memory, attention, motor skills, and nervous system function, particularly in vulnerable groups including pregnant individuals and young children. In addition, Mn can lead to aesthetic issues such as altered taste, clogging, and damage to plumbing systems. While Mn has historically been regulated as an aesthetic concern, a mounting body of evidence linking health issues to Mn exposure through drinking water has heightened the challenges of using groundwater to meet drinking water needs. Recently, Health Canada established a health guideline which set a maximum acceptable concentration for total Mn in drinking water of 120 μg/L. Greensand (GS) filters are commonly used in conventional drinking water treatment systems for Mn(II) removal due to their cost-effectiveness and high exchange capacity. However, under certain conditions conventional GS systems may have a low Mn(II) removal efficiency (Galangashi et al. 2021) and encounter challenges related to Mn leaching (Outram et al. 2018), resulting in failure to meet health-related standards. Furthermore, GS filters typically undergo regeneration using potassium permanganate (KMnO4), a mild oxidant that results in the release of additional Mn waste byproducts during the regeneration of the filter. Recent research suggests that Mn-containing materials can effectively activate peroxymonosulfate (PMS) and produce reactive oxygen species (ROS) that facilitate contaminant degradation. This study aims to investigate whether PMS may be used to improve greensand treatment systems and enhance Mn(II) removal from drinking water. Batch experiments were performed to test the Mn(II) removal efficiency across a range of PMS concentrations (0-500 μM) and GS mass (0.1-3 g). Aqueous Mn concentrations were measured over time using inductively coupled plasma optical emission spectrometry (ICP-OES). Solid-phase reaction products were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The mechanisms of Mn oxidation were identified by quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. The activation of PMS by greensand significantly increased the removal efficiency of Mn(II) compared to the conventional method (e.g., 96.83(±3.77)% at PMS = 500 µM vs. 5.77(±11.1)% at PMS = 0 µM). Our results attribute the mechanism underlying increased Mn removal in our improved treatment method to advanced oxidation processes that involve free radicals (e.g., hydroxyl radical (·OH) and sulfate radical (SO4·-)) and non-free radical pathways, with Mn oxides as the main oxidation products. This study provides a new treatment method for more efficient Mn(II) removal while simultaneously reducing Mn wastes produced during the regeneration cycle which allows for a more sustainable and holistic management of invaluable groundwater resources.

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.

Economic and social perspectives of implementing artificial intelligence in drinking water treatment systems for predicting coagulant dosage: A transition toward sustainability

The traditional determination of optimum coagulant doses in drinking water treatment plants (WTPs) using the jar test technique is time-consuming, expensive, significantly influenced by variations in raw water quality, and susceptible to human error. Therefore, this study employed an artificial intelligence (AI) technique, namely, artificial neural network (ANN), to predict the coagulant dosage and explore the economic and social perspectives of its implementation in waterworks. Data on raw water quality parameters obtained from a drinking WTP were utilized to develop prediction models. The results show that the proposed ANN model performed slightly better than the multiple linear regression (MLR) model regarding coagulant dosage prediction. With test data, the ANN model provided the mean absolute percentage error (MAPE), root mean square error (RMSE), and coefficient of determination (R2) values of 5.59, 2.49 mg/L, and 0.94, which were improved by 52.1%, 44.2%, and 17.1%, in comparison to the MLR model. The economic benefits from AI implementation in coagulation-flocculation operations could produce total savings of US$ 8036.44 per year, net present value (NPV) of US$ 18,154.81, and a discounted payback period of 3.4 years. Moreover, social benefits included safeguarding human health, decent job creation, and reliability and resilience of water production infrastructure. The adoption of AI in WTPs showed a strong linkage with multiple technological- and water-related sustainable development goals (SDGs) and associated targets. Identifying SDG correlations would aid in the sustainable planning and management of operational processes in WTPs worldwide.

Content of E.Coli, Coliform and Iron (Fe) Bacteria with A Refill Drinking Water Treatment System in Tinggimoncong District

Drinking water is water that has gone through a processing process or without a processing process that meets health requirements and can be drunk directly. Drinking water is safe for health if it meets the Physical, Microbiological, Chemical and Radioactive requirements contained in the mandatory parameters and additional parameters. The purpose of this study was to determine the content of E.coli, Coliform and Iron (Fe) Bacteria with a Refill Drinking Water Treatment System in Tinggimoncong District. This type of research is quantitative research with a descriptive approach, namely the type of research used to analyze data by describing or describing the data that has been collected as it is. This sampling technique is total sampling. This research was conducted on August 12-13 2022. The sample in this study was refill drinking water in Tinggimoncong District. In examining the laboratory test, the researcher used the Sanitarian Kit. Drinking water samples were taken from 11 drinking water depots spread across Tinggimoncong District. The results of this study indicated that of the 11 samples of drinking water that did not contain E.coli, and 7 samples of drinking water that contained coliform, 11 samples contained iron (Fe) according to the permissible levels and 4 samples of drinking water were free of microbiological and chemical content. From the results of this study, it is suggested that the Health Service and Community Health Centers improve supervision of the quality of DAMIU not only checking the quality of AMIU but also the feasibility of DAM and PHBS of employees and DAMIU quality is not only checked on processed products but on DAMIU that is ready to be distributed because contamination can occur during packaging.

Microbiome, resistome and mobilome of chlorine-free drinking water treatment systems

Drinking water treatment plants (DWTPs) are designed to remove physical, chemical, and biological contaminants. However, until recently, the role of DWTPs in minimizing the cycling of antibiotic resistance determinants has got limited attention. In particular, the risk of selecting antibiotic-resistant bacteria (ARB) is largely overlooked in chlorine-free DWTPs where biological processes are applied. Here, we combined high-throughput quantitative PCR and metagenomics to analyze the abundance and dynamics of microbial communities, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) across the treatment trains of two chlorine-free DWTPs involving dune-based and reservoir-based systems. The microbial diversity of the water increased after all biological unit operations, namely rapid and slow sand filtration (SSF), and granular activated carbon filtration. Both DWTPs reduced the concentration of ARGs and MGEs in the water by circa 2.5 log gene copies mL−1, despite their relative increase in the disinfection sub-units (SSF in dune-based and UV treatment in reservoir-based DWTPs). The total microbial concentration was also reduced (2.5 log units), and none of the DWTPs enriched for bacteria containing genes linked to antibiotic resistance. Our findings highlight the effectiveness of chlorine-free DWTPs in supplying safe drinking water while reducing the concentration of antibiotic resistance determinants. To the best of our knowledge, this is the first study that monitors the presence and dynamics of antibiotic resistance determinants in chlorine-free DWTPs.

Slow Sand Filters for the 21st Century: A Review.

Safe drinking water remains a major global challenge, especially in rural areas where, according to UNICEF, 80% of those without access to improved water systems reside. While water, sanitation, and hygiene (WASH)-related diseases and deaths are common outcomes of unsafe water, there is also an economic burden associated with unsafe water. These burdens are most prominent in rural areas in less-developed nations. Slow sand filters (SSFs), or biological sand filters (BSFs), are ideal water treatment solutions for these low-resource regions. SSFs are the oldest municipal drinking water treatment systems and improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odor problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination. While the working principles of slow sand filtration have remained the same for over two centuries, the design, sizes, and application of slow sand filters have been customized over the years. This paper reviews these adaptations and recent reports on performance regarding contaminant removal. We specifically address the removal of turbidity and microbial contaminants, which are of great concern to rural populations in developing countries.

Energy efficiency of drinking water treatment plants: A methodological approach for its ranking

Drinking water treatment systems (DWTSs) are energy intensive facilities, and are an example of the water-energy nexus. Benchmarking energy efficiency is a valuable tool for improving the economic and environmental performance of such facilities. Data envelopment analysis (DEA) is typically used to assess efficiency, allocating flexible weights (FSW) to variables that maximise energy efficiency scores for each DWTS (DEA-FSW). It means that different conditions are applied to each DWTS. Moreover, the DEA-FSW approach has finite discriminatory power which limits cross-unit comparison of energy efficiency hindering the benchmarking of DWTSs. To overcome these limitations, our study explored the effect of estimating the energy efficiency scores of DWTSs by allocating common sets of weights (CSW) within DEA (DEA-CSW). This approach was applied empirically on a sample of 146 DWTSs. Evaluated DWTSs had poor energetic performance based on both DEA-FSW and DEA-CSW estimates (low energy efficiency scores: 0.329 and 0.163, respectively). Even in the optimistic scenario, the average energy efficiency score was low (0.220), with potential electricity savings of 78 % by DWTPs when energy efficient. Unlike DEA-FSW, DEA-CSW allowed energy efficient DWTSs to be distinguished from the 146 facilities. Significant differences in the weights allocated to electricity and pollutants removed from raw water were reported for both approaches, and contributed to diverging energy efficiency scores. In conclusion, this study demonstrated the relevance of using suitable methods to generate comparable results for water companies, allowing the energy performance of DWTSs to be objectively evaluated for benchmarking purposes.

An electrical- and chemical-free approach using microfilter and Ag-based catalysts for emergency drinking water treatment

ABSTRACT In emergency cases such as disasters, supplying enough safe drinking water is one of the most urgent needs for human life. This research aimed to develop a chemical- and electricity-free drinking water treatment system based on microfiltration and catalysts of Ag and Ag-TiO2-SiO2 coated on glass spheres in both dark and sunlight conditions. The system was applied to treat raw water samples taken from five rivers in Vietnam, simulated floodwater samples with high turbidity and E. coli concentration, and real flooding water samples. The results showed the filtration unit fed with simulated floodwater generated lower fluxes and shorter working durations before chemical cleaning than that fed with normal river water. However, filtrate quality was not significantly different for these five water samples with very low values of turbidity (0–0.66 NTU), total coliform (5–19 CFU (100 mL)−1), and E. coli (0–17 CFU (100 mL)−1). The catalyst units using glass spheres coated with either Ag in dark and sunlight or Ag-TiO2-SiO2 under sunlight can completely remove E. coli and coliform as well as additionally mitigate natural organic matters. This study hence suggests the combination of microfiltration and Ag-based catalytic treatment for safe drinking water supply in emergencies, especially for flooding conditions.

Limnoperna fortuneias an invasive biofouling bivalve species in freshwater: a review of its occurrence, biological traits, risks, and control strategies

AbstractConcerns have been raised about the significant biofouling and environmental problems caused by the large numbers of Limnoperna fortunei clinging to water intake facilities. This review first provides a summary of the occurrence of L. fortunei in typical regions including China, South America, and Japan. Furthermore, this article provides a comprehensive overview of the biological traits, risks, and control of L. fortunei. Importantly, the planktonic larval stage is a critical period for the expansion of L. fortunei. Its biofouling process mainly relies on the adhesion of byssus to substrates. Various physical and chemical methods have been proposed and used to control L. fortunei. Among these methods, sodium hypochlorite has been shown to be effective in preventing the adhesion of L. fortunei by dissolving its byssus at much lower concentrations. Overall, effective and environmental-friendly antifouling strategies are still rare, particularly in drinking water treatment systems, and are encouraged to develop in future studies. This review not only provides a comprehensive understanding of L. fortunei but also helps to guide the prevention and control of L. fortunei.

A Coagulation Process Combined with a Multi-Stage Filtration System for Drinking Water Treatment: An Alternative for Small Communities

As set out in the Sustainable Development Goals, it is necessary to achieve universal and equitable access to safe drinking water services for all the world’s population. Appropriate water treatment alternatives for rural areas should be prioritised to achieve this goal. In this work, a simplified drinking water treatment system (SDWTS), which has great potential for application in small communities and rural areas, was evaluated on a pilot scale for turbidity and apparent colour removal using synthetic raw water. The SDWTS integrates Upflow Gravel Filter in Layers (UGFL) and Rapid Sand Filter (RSF) with previous coagulation. This evaluation was carried out using a 23 factorial experiment, with the factors: type of water, type of coagulant and flow. The factorial design showed that the SDWTS had the highest turbidity removal efficiencies (&gt;98.7%) with type II (20 NTU) water and PACl coagulant, while flow rate had no significant effect on turbidity removal. Under optimal operating conditions (type II water, PACl and 1.0 m3/d), the SDWTS produces treated water that meets the standards required by Colombian regulations and World Health Organisation recommendations for drinking water, concerning the variables: turbidity, apparent colour, total coliforms, E. coli, pH, electrical conductivity and Al. The SDWTS maintained its capacity to produce potable water when evaluated with the increased operating flow (up to 3.0 m3/d) and raw water turbidity (up to 50 NTU). The SDWTS can be an efficient and innovative alternative for water treatment, and its implementation in small communities can contribute to equitable access to drinking water.

Seasonal and Spatial Variations in the Presence of Giardia and Cryptosporidium in Rural Drinking Water Supply Systems in Different Municipalities of Antioquia, Colombia

This study evaluated the seasonal and spatial variations in the presence of Giardia and Cryptosporidium in rural drinking water supply systems of different municipalities of Antioquia. The municipalities evaluated were Envigado, Caldas, Sabaneta, La Estrella, Itagüi, Bello, Barbosa, Copacabana, and Girardota, located in the department of Antioquia, Colombia. The experimentation was carried out over 9 sampling campaigns in the period between July 2019 and November 2020. This period encompassed the two seasons presented in Colombia: dry and wet. Each municipality included in this study has a conventional basic drinking water treatment system (DWTS) which includes sand trap, rapid filtration, and chlorination. The results showed good removal efficiencies of Cryptosporidium and Giardia in the DWTS evaluated. However, evaluation of other characteristics of water quality and of the water quality risk index for human consumption (IRCA) showed concerning water quality conditions in the rural drinking water systems supply. The prevailing risk levels of the drinking water are medium, high, or non-viable sanitary, which means the population is supplied with water that does not meet the minimum quality criteria established by Colombian regulations.

Organophosphate tri- and diesters in source water supply and drinking water treatment systems of a metropolitan city in China.

The water contaminations with organophosphate triesters (tri-OPEs) and diesters (di-OPEs) have recently provoked concern. However, the distributions of these compounds in natural water sources and artificial water treatment facilities are poorly characterized. A comprehensive study was therefore performed to measure their concentrations in a water source, a long-distance water pipeline, and a drinking water treatment plant (DWTP). Eight tri-OPEs and 3 di-OPEs were found to be widely distributed, with total concentrations in source water and pipelines ranging from 290.6 to 843.9ng/L. The most abundant pollutants were tris(1-chloro-2-propyl) phosphate (TCPP), triethyl phosphate, tri-n-butyl phosphate (TnBP), and diphenyl phosphate (DPhP). Di-OPEs appeared to be removed less efficiently in the DWTP than the parent tri-OPEs, and the elimination efficiencies of tri-OPEs were structure-dependent. Long-distance pipeline transportation had no significant effect on the distributions of tri- and di-OPEs. Statistical analysis suggested that the sources of di-OPEs and the corresponding tri-OPEs differed, as did those of DPhP and di-n-butyl phosphate. A risk analysis indicated that tri-OPEs present limited ecological risks that are mainly due to TnBP and TCPP, and that the human health risks of tri-OPEs are negligible. However, di-OPEs (especially DPhP) may increase these risks. Further studies on the risks posed by di-OPEs in aquatic environments are therefore needed.