Special Issue "Water Pollution and Sanitation"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: closed (30 November 2021).

Special Issue Editors

Prof. Dr. Satoshi Takizawa
E-Mail Website
Guest Editor
University of Tokyo, Tokyo, Japan
Interests: water pollution control; water supply; water treatment technologies; removal of inorganic contaminants; management of urban water systems; safe drinking water and sanitation in developing countries
Special Issues, Collections and Topics in MDPI journals
Dr. Takashi Hashimoto
E-Mail Website
Guest Editor
Research Center for Advanced Science and Technology, the University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan
Interests: water supply; water treatment technologies; membrane filtration processes; safe drinking water in developing countries
Special Issues, Collections and Topics in MDPI journals
Dr. Shinobu Kazama
E-Mail Website
Guest Editor
University of Tokyo, Tokyo, Japan
Interests: microbial contamination of water sources; microbial health risk analysis; safe drinking water and sanitation in developing countries

Special Issue Information

Dear Colleagues,

Water sources are contaminated by both natural and anthropogenic pollutants. Natural organic matter in water sources can be enriched due to algal bloom and enhanced plant growth caused by climate change. In addition, anthropogenic pollution is still rampant in many developing countries due to a lack of wastewater collection and treatment systems. In almost ten years to the target year of 2030 of the SDGs, we must accelerate our efforts to achieve SDGs Goal 6 by minimizing and controlling water pollution. Water pollution has been making it even difficult to supply safely managed drinking water to the people. Therefore, cities and villages, as well as small communities, need to tap water sources that have been considered to be difficult to treat to produce potable water. We are facing challenges of treatment of non-conventional water sources such as highly contaminated water sources, water sources with high turbidity, groundwaters containing inorganic contaminants, e.g., arsenic, fluoride and manganese, and even sea water. This Special Issue welcomes the submission of papers reporting these challenges in water pollution control, development of water sources, and treatment and supply of drinking water from the contaminated and nonconventional water sources. Both technical and management papers are welcome and considered for publication in this Special Issue.

Prof. Dr. Satoshi Takizawa
Dr. Takashi Hashimoto
Dr. Shinobu Kazama
Guest Editors

Manuscript Submission Information

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Keywords

  • Water pollution
  • Water supply
  • Sanitation
  • Natural organic matter
  • Water treatment technologies
  • SDGs Goal 6
  • Source water protection
  • Groundwater
  • Climate change

Published Papers (12 papers)

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Research

Article
Seasonal Variations in Groundwater Quality and Hydrogeochemistry in the Endemic Areas of Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka
Water 2021, 13(23), 3356; https://doi.org/10.3390/w13233356 - 26 Nov 2021
Viewed by 371
Abstract
Groundwater quality and geochemical processes were investigated in the endemic areas of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. Representative groundwater samples (n = 60) were collected from 30 dug wells located in the Anuradhapura district, over the dry [...] Read more.
Groundwater quality and geochemical processes were investigated in the endemic areas of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. Representative groundwater samples (n = 60) were collected from 30 dug wells located in the Anuradhapura district, over the dry and wet seasons. The samples were analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS), alkalinity, major cations and major anions. Calcium-magnesium-bicarbonate ion combinations are predominant in this groundwater, and the simultaneous occurrence of high hardness (382–394 mg/L as CaCO3), alkalinity (364–379 mg/L as CaCO3) and ionicity is a salient characteristic. Alkalinity, TDS, hardness, and magnesium exceeded the safe limits for drinking in over half of the samples, regardless of the season. The major ion chemistry (Ca2+, Mg2+, Na+ and HCO3) is primarily governed by the weathering of carbonate and silicate minerals, ion exchange, and evaporation which is accelerated by the semi-arid climate. Fluoride and chloride inputs are regulated by dissolution of fluoride-bearing minerals and anthropogenic causes, respectively. Saturation indices suggested supersaturation of carbonates and silicates, and undersaturation of evaporites and fluorite. Persistent high ionicity, and hardness of groundwater that is seldom impacted by seasonal variations might be playing a vital role in the genesis of CKDu. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Network Model Analysis of Residual Chlorine to Reduce Disinfection Byproducts in Water Supply Systems in Yangon City, Myanmar
Water 2021, 13(20), 2921; https://doi.org/10.3390/w13202921 - 17 Oct 2021
Viewed by 669
Abstract
In Yangon City, chlorination commenced in January 2020 to supply drinkable water; therefore, there is as yet no information on chlorine decay and DBP formation in the water supply system. This study aimed to find methods to optimize chlorine dosage in Yangon City. [...] Read more.
In Yangon City, chlorination commenced in January 2020 to supply drinkable water; therefore, there is as yet no information on chlorine decay and DBP formation in the water supply system. This study aimed to find methods to optimize chlorine dosage in Yangon City. Onsite sampling and laboratory analyses of residual chlorine and trihalomethane (THM) formation, as well as water quality simulations, were conducted to find the chlorine decay and THM formation kinetics. Due to a high chlorine dose of 2 mg/L for both pre- and post-chlorination, disinfection was effective despite the low removal efficiency of turbidity. However, THMs were found in high levels in both treated and tap water due to the high THM formation potential of raw water. The re-contamination and/or transformation of dissolved organic matter were found in the distribution network by increases in specific ultraviolet absorption (SUVA) values and excitation-emission matrix (EEM) fluorophores, which brought about variations of THMs in the networks. The EPANET models were run assuming there to be no water leakages; it was found that the chlorine dose could be decreased to 0.8 mg/L to meet the guidelines for THMs and residual chlorine. The methods employed in this study could be also applied in other water supply systems in tropical developing countries with limited water quality monitoring data. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Sewage Markers as Determinants to Differentiate Origins of Emerging Organic Pollutants in an Urban Sri Lankan Water Drainage Network
Water 2021, 13(20), 2898; https://doi.org/10.3390/w13202898 - 15 Oct 2021
Viewed by 317
Abstract
Urban sanitation is a major challenge during the rapid urbanization being experienced by developing countries, as a low sewerage infrastructure capacity and irregular onsite wastewater treatment raise the risk of surface water contamination. The application of specific sewage markers to characterize contaminant sources [...] Read more.
Urban sanitation is a major challenge during the rapid urbanization being experienced by developing countries, as a low sewerage infrastructure capacity and irregular onsite wastewater treatment raise the risk of surface water contamination. The application of specific sewage markers to characterize contaminant sources is therefore essential for managing urban sanitation issues. In this study, we investigated the concentrations of eight sewage markers (acetaminophen, caffeine, carbamazepine, cotinine, sulfamethoxazole, sulfapyridine, atenolol, and acesulfame) in various water sources within urban area of the Galle City, Sri Lanka. The total concentration of the eight markers was in the order of hospital discharge > sewage treatment plant (STP) influent > surface drainage system. Among the eight selected markers, acetaminophen was dominant in hospital discharge (70.2–123.6 µg/L) while caffeine was the largest contributor to STP influent (16.2–68.7 µg/L) and surface drainage (0.95–21.73 µg/L). We then proposed and tested a set of criteria for evaluating the applicability of markers, including removal efficiency, concentration magnitude, excretion rate, and wastewater burden. The labile markers caffeine and acetaminophen were suitable for characterizing domestic gray and black wastewater, respectively. These results imply that the city’s drainage system receives both domestic graywater and human excretion, likely due to insufficient on-site sanitation systems. The conservative marker carbamazepine was useful for tracking hospital residues over long distances; these results imply that hospital wastewater treatment was not working properly, accounting for pharmaceutical residues reaching surface water via a hidden discharges connected to the drainage system. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Water Demand Management Based on Water Consumption Data Analysis in the Emirate of Abu Dhabi
Water 2021, 13(20), 2827; https://doi.org/10.3390/w13202827 - 12 Oct 2021
Viewed by 546
Abstract
In Abu Dhabi, in the United Arab Emirates (UAE), the population and water demand have nearly tripled in the last two decades. Thus, it has become critical to curtail the growing water demand. This study aimed to evaluate the efficacy of Abu Dhabi’s [...] Read more.
In Abu Dhabi, in the United Arab Emirates (UAE), the population and water demand have nearly tripled in the last two decades. Thus, it has become critical to curtail the growing water demand. This study aimed to evaluate the efficacy of Abu Dhabi’s residential water demand management through the installation of water-saving fittings. The analysis of water consumption time-series data revealed that water consumption of the three water user categories was significantly different. Briefly: water-tariff exempt users consumed 95.19 m3/d/connection in 2019, followed by nationals with 5.14 m3/d/connection, and expats at 0.7 m3/d/connection. Nationals began saving water in 2011, which was earlier than the water tariff revision of 2015. In a newly developed area of Khalifa City, the water consumption of new residents was 46.0% less than that of old residents, indicating the effectiveness of water-saving fittings installed in new homes following the Housing Rules’ requirements. Then, based on the estimated number of new connections and the fittings’ saving efficiencies, we estimated that water-saving fittings contributed to 73.1% of the water savings since 2011. These results strongly recommend the introduction of an incentive or subsidy for owners of old houses to replace their outdated fittings with water-saving ones. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Evaluation of Microbial Contamination of Groundwater under Different Topographic Conditions and Household Water Treatment Systems in Special Region of Yogyakarta Province, Indonesia
Water 2021, 13(12), 1673; https://doi.org/10.3390/w13121673 - 16 Jun 2021
Viewed by 704
Abstract
Since the coverage of piped water is still only 20.1% in Indonesia, many people rely on groundwater for drinking and daily use, although the quality of the groundwater is not well understood. This study evaluated the influence of the topography, well type, groundwater [...] Read more.
Since the coverage of piped water is still only 20.1% in Indonesia, many people rely on groundwater for drinking and daily use, although the quality of the groundwater is not well understood. This study evaluated the influence of the topography, well type, groundwater abstraction depth, sanitation facility type, and distance between the well and the sanitation facility on the groundwater quality. In addition, a possible household treatment system was investigated based on microbial removal efficiency and household acceptance. The results showed the groundwater abstraction depth and well type were the most important factors in controlling microbial contamination. The sanitation facility type, except small-scale sewer systems, and the distance from a well were not significantly correlated with E. coli concentration. A high microbial concentration was found in a flat area with predominantly shallow wells, latrines, and septic tanks because the topographic conditions determined the commonly used well types and groundwater abstraction depth. The RO + UV system was the only system that assured microbial safety of treated water. The chlorination and microfiltration systems had difficulty with chlorine-dosage adjustment and microbial removal, respectively. Raising public awareness of water quality problems was found to be important to improve acceptance of household treatment systems. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Influence of Service Levels and COVID-19 on Water Supply Inequalities of Community-Managed Service Providers in Nepal
Water 2021, 13(10), 1349; https://doi.org/10.3390/w13101349 - 13 May 2021
Cited by 4 | Viewed by 717
Abstract
In Nepal, there are three types of water service providers; two types of government-managed service providers covering urban and municipal areas, and community-managed service providers called Water Users and Sanitation Associations (WUSAs). This study aims to assess the current water supply service levels [...] Read more.
In Nepal, there are three types of water service providers; two types of government-managed service providers covering urban and municipal areas, and community-managed service providers called Water Users and Sanitation Associations (WUSAs). This study aims to assess the current water supply service levels and water supply inequalities of WUSAs in terms of water consumption, supply hours, and customer satisfaction. Among the three types of water service providers, WUSAs offered the best performance in terms of their low non-revenue water (NRW) rates and production costs, high bill collection rates, and long supply hours. During the COVID-19 lockdown, water consumption increased, but bill payment notably decreased, possibly due to restricted movement and hesitation by customers to make payments. The multiple-year water consumption variations illustrated the uneven water consumption behavior of customers. Despite the variation in water supply hours, Lorenz curves, Gini coefficients (G), and water consumption analysis depicted low inequalities (G ≈ 0.20–0.28) and adequate water consumption among WUSAs even in 2019–2020. In the three WUSAs, more than 90%, 74%, and 38% of customers consumed water above the basic, medium, and high levels, respectively. Thus, maintaining high service levels of WUSAs is instrumental in achieving Goal 6 of the Sustainable Development Goals (SDGs) in Nepal. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Effects of Ferrihydrite-Impregnated Powdered Activated Carbon on Phosphate Removal and Biofouling of Ultrafiltration Membrane
Water 2021, 13(9), 1178; https://doi.org/10.3390/w13091178 - 24 Apr 2021
Viewed by 867
Abstract
The presence of multiple contaminant species in surface waters makes surface water treatment difficult to accomplish through a single process. Herein, we evaluated the ability of an integrated adsorption/ultrafiltration (UF) membrane filtration system to simultaneously remove phosphates and dissolved organic matter (DOM). When [...] Read more.
The presence of multiple contaminant species in surface waters makes surface water treatment difficult to accomplish through a single process. Herein, we evaluated the ability of an integrated adsorption/ultrafiltration (UF) membrane filtration system to simultaneously remove phosphates and dissolved organic matter (DOM). When bare powdered activated carbon (PAC) and PAC impregnated with amorphous ferrihydrite (FHPAC) adsorbents were compared, FHPAC showed a greater adsorption rate and capacity for phosphate. FHPAC had a phosphate adsorption capacity of 2.32 mg PO43−/g FHPAC, even when DOM was present as a competing adsorbate. In a lab-scale hybrid FHPAC-UF system (i.e. integrated adsorption by FHPAC with UF membrane filtration), irreversible membrane fouling was ca. three times lower than that in a PAC-UF system. When membrane fouling in the PAC-UF system was described with pore blockage models, we found that the main cause of fouling was bacterial deposition on the membrane surface. CLSM analysis determined that the chemical composition of foulants in the PAC-UF system included higher proportions of proteins, nucleic acids, and alpha-polysaccharides than that in the FHPAC-UF system. Overall, FHPAC’s ability to undergo ligand exchanges with DOM helped to reduce the nutrients and bacteria that cause biofouling to accumulate on the membrane surface. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Assessing the Removal of Arsenite and Arsenate Mixtures from the Synthetic Bangladesh Groundwater (SBGW) Using Combined Fe(VI)/Fe(III) Treatments and Local Regression Analysis
Water 2021, 13(9), 1134; https://doi.org/10.3390/w13091134 - 21 Apr 2021
Cited by 1 | Viewed by 672
Abstract
Arsenic is an inorganic pollutant that, depending on oxidation–reduction and pH level conditions, may be found in natural waters in two variants: As(III) and As(V). Any treatment to effectively remove arsenic from water will be conditioned by the presence of one or both [...] Read more.
Arsenic is an inorganic pollutant that, depending on oxidation–reduction and pH level conditions, may be found in natural waters in two variants: As(III) and As(V). Any treatment to effectively remove arsenic from water will be conditioned by the presence of one or both variants. In this context, this study assesses using electrochemically produced Fe(VI) with Fe(III) to remove As(III), As(V), and their combinations from the Synthetic Bangladesh Groundwater (SBGW) containing anions that interfere with iron-based arsenic removal processes. The combined use of Fe(VI) and Fe(III) allowed us to remove the total arsenic below the 10 mg L−1 threshold established by the World Health Organization and Peruvian regulations for drinking water. An optimum combination of 1 mg L−1 of Fe(VI) and 30 mg L−1 of Fe(III) was identified and tested on the removal of four different proportions of As(III):As(V) for two total concentrations: 500 and 250 mg L−1. There were no significant differences in the final removal values under the different proportions of As(III):As(V) for each total concentration, with a final removal average of 99.0% and 96.9% for the 500 and 250 µg L−1 concentrations, respectively. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Water Treatment Plant Prototype with pH Control Modeled on Fuzzy Logic for Removing Arsenic Using Fe(VI) and Fe(III)
Water 2020, 12(10), 2834; https://doi.org/10.3390/w12102834 - 12 Oct 2020
Cited by 2 | Viewed by 933
Abstract
This study proposes a fuzzy control strategy embedded in a Siemens IoT2040 gateway developed for removing inorganic arsenic from synthetic underground water in a treatment plant prototype. The prototype is used to dose a constant flow of Fe(VI) to maintain an oxide-reduction potential [...] Read more.
This study proposes a fuzzy control strategy embedded in a Siemens IoT2040 gateway developed for removing inorganic arsenic from synthetic underground water in a treatment plant prototype. The prototype is used to dose a constant flow of Fe(VI) to maintain an oxide-reduction potential to guarantee the oxidation of arsenite into arsenate, while the fuzzy logic embedded in the IoT control manages the addition of Fe(III) to achieve a proper pH adjustment and efficient arsenate removal. The tests used synthetic Bangladesh groundwater enriched with 200 µg/L of arsenite and 200 µg/L of arsenate. The results revealed that the plant prototype yielded an effective treatment of the water. Arsenate was decreased to an average value of 6.66 µg/L and, the arsenite concentration decreased to 1.01 µg/L or less. These values were lower than the limit of 10 µg/L deemed by the World Health Organization as safe for human consumption. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Re-Examination of the Relationship between Agricultural Economic Growth and Non-Point Source Pollution in China: Evidence from the Threshold Model of Financial Development
Water 2020, 12(9), 2609; https://doi.org/10.3390/w12092609 - 18 Sep 2020
Viewed by 627
Abstract
The coordinated development of agricultural economic growth and non-point source (NPS) pollution is an important task in enhancing pollution prevention. Significantly, agricultural economic growth and NPS pollution are interrelated, and their mechanism will be affected by financial development. For this reason, the current [...] Read more.
The coordinated development of agricultural economic growth and non-point source (NPS) pollution is an important task in enhancing pollution prevention. Significantly, agricultural economic growth and NPS pollution are interrelated, and their mechanism will be affected by financial development. For this reason, the current study established a panel smooth transformation regression (PSTR) model to reveal the mechanical evolution under different financial development levels. It was found that the impact of agricultural economic growth on NPS pollution was significantly positive in the low level of financial development, which is manifested as an “intensification effect”. Fortunately, when the level of financial development reaches the medium and high thresholds, agricultural economic growth will inhibit agricultural NPS pollution. At the same time it was also found that the impact of agricultural economic growth on NPS pollution is manifested as an “inhibition effect” at the overall level, but presenting significant structural differences. Specifically, the impact on the eastern and central regions of China is manifested as an “inhibition effect”, whereas the impact in the western region of China is characterized as an “intensification effect”. Finally, the elasticity analysis showed that the influence of financial development on agricultural NPS pollution was significantly positive, and that its intensification effect is ubiquitous. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
Article
Modeling and Analysis of Particle Deposition Processes on PVDF Membranes Using SEM Images and Image Generation by Auxiliary Classifier Generative Adversarial Networks
Water 2020, 12(8), 2225; https://doi.org/10.3390/w12082225 - 07 Aug 2020
Viewed by 988
Abstract
Due to highly complex membrane structures, previous research on membrane modeling employed extensively simplified structures to save computational expense, which resulted in deviation from the real processes of membrane fouling. To overcome those shortcomings of the previous models, this study aimed to provide [...] Read more.
Due to highly complex membrane structures, previous research on membrane modeling employed extensively simplified structures to save computational expense, which resulted in deviation from the real processes of membrane fouling. To overcome those shortcomings of the previous models, this study aimed to provide an alternative method of modeling membrane fouling in water filtration, using auxiliary classifier generative adversarial networks (ACGAN). Scanning electron microscope (SEM) images of 0.45 µm polyvinylidene difluoride (PVDF) flat sheet membranes were taken as inputs to ACGAN, before and after the filtration of feed waters containing 0.5 µm diameter particles at varied concentrations. The images generated with the ACGAN model successfully reconstructed the real images of particles deposited on the membranes, as verified by human validation and particle counting of the real and generated images. This indicated that the ACGAN model developed in this research successfully built a model architecture that represents the complex structure of the real PVDF membrane. The image analysis through particle counting and density-based spatial clustering of application with noise (DBSCAN) revealed that both real and generated membranes had an uneven deposition of particles, which was caused by the complex structures of the membranes and by different particle concentrations. These results indicated the importance and effectiveness of modeling intact membranes, without simplifying the structure using such models as the ACGAN model presented in this paper. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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Article
Modelling the Mineralization of Formaldehyde by Treatment with Nitric Acid
Water 2020, 12(6), 1567; https://doi.org/10.3390/w12061567 - 30 May 2020
Cited by 1 | Viewed by 799
Abstract
Formaldehyde is a recalcitrant pollutant, which is difficult to remove from wastewater using conventional and advanced treatments. The objective of this research was to remove the organic matter from formaldehyde from an industrial wastewater, achieving its total mineralization and allowing the reuse of [...] Read more.
Formaldehyde is a recalcitrant pollutant, which is difficult to remove from wastewater using conventional and advanced treatments. The objective of this research was to remove the organic matter from formaldehyde from an industrial wastewater, achieving its total mineralization and allowing the reuse of the water. The treatment was based on the reaction of formaldehyde with nitric acid, which was first studied and modelled with synthetic waters. Results show that it was possible to almost completely mineralize the formaldehyde (>95% TOC removal) at the best conditions studied (1.72 M of nitric acid and 85 °C of temperature). The addition of NaNO2 accelerated this reaction; however, after 2 h of reaction time, its effect was negligible at the maximum concentration of HNO3 studied. The results obtained with industrial wastewater fit well with the model. It is concluded that formaldehyde in actual wastewaters can be successfully removed through direct mineralization with nitric acid, under selected conditions. Full article
(This article belongs to the Special Issue Water Pollution and Sanitation)
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