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Information about microbial water quality is critical for managing water safety and protecting public health. In low-income countries, monitoring all drinking water supplies is impractical because financial resources and capacity are insufficient. Data sets derived from satellite imagery, census, and hydrological models provide an opportunity to examine relationships between a suite of environmental risk factors and microbial water quality over large geographical scales. We investigated the relationships between groundwater fecal contamination and different environmental parameters in Uganda and Bangladesh. In Uganda, groundwater contamination was associated with high population density ( p < 0.001; OR = 1.27), high cropland coverage ( p < 0.001; OR = 1.47), high average monthly precipitation ( p < 0.001; OR = 1.14), and high surface runoff ( p < 0.001; OR = 1.37), while low groundwater contamination was more likely in areas further from cities ( p < 0.001; OR = 0.66) and with higher forest coverage ( p < 0.001; OR = 0.70). In Bangladesh, contamination was associated with higher weekly precipitation ( p < 0.001; OR = 1.44) and higher livestock density (p = 0.05; OR = 1.11), while low contamination was associated with low forest coverage ( p < 0.001; OR = 1.23) and high cropland coverage ( p < 0.001; OR = 0.80). We developed a groundwater contamination index for each country to help decision-makers identify areas where groundwater is most prone to fecal contamination and prioritize monitoring activities. Our approach demonstrates how to harness satellite-derived data to guide water safety management.

Shallow groundwater containing toxic concentrations of arsenic is the primary source of drinking water for millions of households in rural West Bengal, India. Often, this water also contains unpleasant levels of iron and non-negligible fecal contamination. Alternatives to shallow groundwater are increasingly available, including government-built deep tubewells, water purchased from independent providers, municipal piped water, and household filters. We conducted a survey of 501 households in Murshidabad district in 2014 to explore what influenced the use of available alternatives. Socioeconomic status and the perceived likelihood of gastrointestinal (GI) illness (which was associated with dissatisfaction with iron in groundwater) were the primary determinants of the use of alternatives. Arsenic knowledge was limited. The choice amongst alternatives was influenced by economic, social, and aesthetic factors, but not by health risk perceptions. The use of purchased water was rarely exclusive and was strongly associated with socioeconomic status, suggesting that this form of market-based water provision does not ensure universal access. Demand for purchased water appeared to decrease significantly shortly after free piped water became available at public taps. Our results suggest that arsenic mitigation interventions that also address co-occurring water problems (iron, GI illness) could be more effective than a focus on arsenic alone.

Technologies addressing both arsenic and microbial contamination of Bengal groundwater are needed. Fe electrocoagulation (Fe-EC), a simple process relying on the dissolution of an Fe(0) anode to produce Fe(III) precipitates, has been shown to efficiently remove arsenic from groundwater at low cost. We investigated Escherichia coli (E. coli) attenuation by Fe-EC in synthetic Bengal groundwater as a function of Fe dosage rate, total Fe dosed, pH, and presence of natural organic matter (NOM). A 2.5 mM Fe dosage simultaneously achieved over 4-log E. coli attenuation and arsenic removal from 450 to below 10 μg/L. E. coli reduction was significantly enhanced at pH 6.6 compared to pH 7.5, which we linked to the decreased rate of Fe(II) oxidation at lower pH. 3 mg/L-C of NOM (Suwanee River fulvic acid) did not significantly affect E. coli attenuation. Live-dead staining and comparisons of Fe-EC with chemical coagulation controls showed that the primary mechanism of E. coli attenuation is physical removal with Fe(III) precipitates, with inactivation likely contributing as well at lower pH. Transmission electron microscopy showed that EC precipitates adhere to and bridge individual E. coli cells, resulting in large bacteria-Fe aggregates that can be removed by gravitational settling. Our results point to the promising ability of Fe-EC to treat arsenic and bacterial contamination simultaneously at low cost.

The ecology and environment of the Yellow River Basin is threatened by fluoride and nitrate contamination induced by anthropogenic activity and geogenic factors. As a result, deciphering the spatio-temporal variability of fluoride and nitrate contamination in this area remains a challenge. Three hundred eighty-six samples of surface water and groundwater from the Inner Mongolia Reaches of the Yellow River Basin were taken for this investigation. According to the results of the multivariate statistical and geostatistical analyses, the fluoride pollution was primarily discovered in the middle and lower reaches of the study area and was determined to be more severe during the dry season. In contrast, nitrate contamination was found to be more severe during the wet season while being widely distributed in groundwater and concentrated in areas with intensive agricultural activities. The primary mechanisms governing the spatial-seasonal patterns of NO 3 - and F - pollution were shown by the principal component analysis, isotopic, and hydrochemical diagrams. The water-rock interaction or evaporation was crucial in the enrichment of F - . The human inputs (e.g., fertilizer or sewage) dominated fluoride and nitrate contamination. Additionally, the alkaline environment played a role in the generation of NO 3 - and F - . The health risk assessment concluded that the threat of fluoride contamination was greater than that of nitrate contamination. Children faced the greatest health risks, followed by females and males. These findings would serve as a guide for water management and pollution control in the Yellow River Basin., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Mixed-valent iron nanoparticles (NP) generated electrochemically by Fe(0) electrocoagulation (EC) show promise for on-demand industrial and drinking water treatment in engineered systems. This work applies multiple characterization techniques (in situ Raman spectroscopy, XRD, SEM, and cryo-TEM) to investigate the formation and persistence of magnetite and green rust (GR) NP phases produced via the Fe(0) EC process. Current density and background electrolyte composition were examined in a controlled anaerobic system to determine the initial Fe phases generated as well as transformation products with aging. Fe phases were characterized in an aerobic EC system with both simple model electrolytes and real groundwater to investigate the formation and aging of Fe phases produced in a system representing treatment of arsenic-contaminated ground waters in South Asia. Two central pathways for magnetite production via Fe(0) EC were identified: (i) as a primary product (formation within seconds when DO absent, no intermediates detected) and (ii) as a transformation product of GR (from minutes to days depending on pH, electrolyte composition, and aging conditions). This study provides a better understanding of the formation conditions of magnetite, GR, and ferric (oxyhydr)oxides in Fe EC, which is essential for process optimization for varying source waters.

Millions of people in rural South Asia are exposed to high levels of arsenic through groundwater used for drinking. Many deployed arsenic remediation technologies quickly fail because they are not maintained, repaired, accepted, or affordable. It is therefore imperative that arsenic remediation technologies be evaluated for their ability to perform within a sustainable and scalable business model that addresses these challenges. We present field trial results of a 600 L Electro-Chemical Arsenic Remediation (ECAR) reactor operating over 3.5 months in West Bengal. These results are evaluated through the lens of a community scale micro-utility business model as a potential sustainable and scalable safe water solution for rural communities in South Asia. We demonstrate ECAR's ability to consistently reduce arsenic concentrations of ~266 μg/L to <5 μg/L in real groundwater, simultaneously meeting the international standards for iron and aluminum in drinking water. ECAR operating costs (amortized capital plus consumables) are estimated as $0.83-$1.04/m(3) under realistic conditions. We discuss the implications of these results against the constraints of a sustainable and scalable business model to argue that ECAR is a promising technology to help provide a clean water solution in arsenic-affected areas of South Asia., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Understanding influential factors for fecal contamination in groundwater is critical for ensuring water safety and public health. The objective of this study is to identify key factors for fecal contamination of shallow tubewells using machine learning methods. Three methods, including recursive feature elimination (RFE) with XGBoost, Random Forest, and mutual information, were implemented to examine E. coli presence and concentration in 1495 tubewell water samples in Matlab, Bangladesh. For E. coli presence, climatic variables, including average rainfall and temperature over the 30, 15, and 7 days preceding sampling, as well as ambient temperature and rainfall on the sampling day, emerged as critical predictors. Land cover characteristics, such as the percentages of urban and agricultural areas within 100 m of a tubewell, were also significant. For E. coli concentration, land cover characteristics within 100 m, the number of hot and heavy-rain days in the 30 days preceding sampling, average rainfall and temperature in the 3 days preceding sampling, and ambient temperature on the sampling day were identified as key drivers. Random Forest and mutual information yielded results that were more similar to each other than to those of RFE with XGBoost. The findings highlight the interplay between climatic factors, land use, and population density in determining fecal contamination in shallow well water and demonstrate the power of machine learning algorithms in ranking these factors. [ABSTRACT FROM AUTHOR]

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Coliforms (FB) posing population health risks in groundwater (GW) have been identified for decades, with recent studies assessing how hydrogeological and non-hydrogeological parameters correlate with their presence. This study focused on explaining the physicochemical and hydrological factors influencing the presence of fecal contamination in the GW system of Ad-Dawadmi, KSA, a hyperarid area facing a prolonged drought. It was designed and implemented by sampling 47 working wells and their laboratory analysis. The data analyses indicated that the salinity exhibited a purification effect such that at levels higher than 3500 and 6000 mg/L, no E. coli and total coliform (TC) were detected. Heavy metals, especially copper, showed strong, hygienic effects at 195 and 300 µg/L thresholds for E. coli and TC, respectively, while those of Fe were at 1200 and 2000 µg/L. Nitrates, dissolved organic carbon (DOC), and dissolved oxygen (DO) showed a quasi-random interrelationship with FB. The occurrence of FB in boreholes up to 52 m below ground level (BGL) challenges the single water resource in the region. Integrating various analyses help constrain and provide multiple lines of evidence for the inferred remarks. This work presented some methodological aspects for understanding the effects of the physicochemical and hydrogeological factors on FB that may better protect water quality and improve human health outcomes. [ABSTRACT FROM AUTHOR]

Fluoride contamination of groundwater is a significant concern because of its detrimental impact on human health. Adsorption using composite oxyhydroxide mineral ores such as bauxite has demonstrated feasibility as an environmental remediation technique for rural and disadvantaged communities due to its cost-effective, environmentally friendly, generally acceptable, and adaptive characteristics. The effects of the composition, pretreatment methods, and influencing factors or parameters on the adsorptive defluoridation of groundwater by bauxite, as well as the adsorption mechanisms and the environmental advantages of using composite mineral ore in the remediation of fluoride from groundwater, are highlighted. Generally, the results indicated that some raw mineral assemblage adsorbents and their pretreated versions are better than or practically similar to current commercial fluoride filters. [ABSTRACT FROM AUTHOR]

People who drink groundwater in rural areas of Southeast Asia are exposed to pathogens and arsenic (As)-related health problems. A water treatment system consisting of electrocoagulation reactors, using iron (Fe) electrodes and a filtration tank, was designed to treat complex contaminated groundwater for drinking. Its applicability was demonstrated near the Red River in Vietnam. The water treatment system reduced 10.3 CFU/mL of total coliform and 376 μg/L of As(III) in the groundwater to 0 CFU/mL and 6.68 μg/L, respectively. Total coliforms were attenuated by Fe(II) infiltration or enmeshed during Fe precipitate formation. Of the total As, 43% formed As(III) complexation with the Fe precipitates and the other 57% was oxidized to As(V) then adsorbed to Fe precipitates. The Fe precipitates, containing total coliforms and As, were separated from the discharge water in the filtration tank. The system required 49 W of power to operate, which equates to 423 kWh/year, to continuously purify 0.5 t water/day. This requirement was powered by a 380–750 W solar panel, without external energy supply, making the water treatment system an appropriate option for addressing drinking water problems in rural areas. [ABSTRACT FROM AUTHOR]

In this study, influences of seven process variables such as initial pH (pHi), applied current (i), operating time (tEC), initial As(III) concentration (Co), diameter of Fe ball anode (dp), column height in the electrocoagulation (EC) reactor (h) and airflow rate (Qair) for removal of As(III) from groundwater by a new air-fed fixed-bed EC reactor were evaluated with a response surface methodology (RSM). The proposed quadratic model fitted very well with the experimental data for the responses. The removal efficiencies and operating costs were determined to be 99% and 0.01 $/m3 at the optimum operating conditions (a pHi of 8.5, 0.05 A, 4.94 min, dp of 9.24 mm, h of 7.49 cm, Qair of 9.98 L/min for 50 µg/L). This study clearly showed that the RSM in the EC process was a very suitable method to optimize the operating conditions at the target value of effluent As(III) concentration (10 µg/L) while keeping the operating cost to minimal and maximize the removal efficiency. [ABSTRACT FROM AUTHOR]

Electrocoagulation (EC) is gaining increased attention for water treatment as it efficiently removes various water contaminants. Therefore, EC was applied to remove arsenic from groundwater of a highly contaminated site in Hamburg, Germany. Groundwater containing 3250 and 14,600 µg/L arsenic, mainly as Arsenite (As(III)), was treated in three different EC batch reactors using a monopolar parallel electrode-configuration. This study focused on iron EC with constant current densities and variable voltage, to investigate the influence of current density, surface to volume ratio, initial arsenic concentration and water volume on the removal of arsenic and the influences on the groundwater composition. Arsenic removal >99.9% was achieved for configurations with high iron dosage after four hours of EC treatment. German drinking water standard for arsenic (<10 µg/L) was obtained after around two hours depending on the applied current densities. Arsenic removal efficiency shows independence from current density, surface to volume ratio, initial concentration and water volume, with respect to the calculated iron dosage. Consequently, the dimensioning and regime of efficient operation of the EC reactor for arsenic removal from groundwater can be calculated solely from the iron dosage determined by the applied current. [ABSTRACT FROM AUTHOR]

Several confirmed cases of arsenic (As) poisoning have been reported in Central Luzon, the Philippines, in recent years. There is a growing interest in As research in the Philippines due to the reported As poisoning cases. However, an extensive spatiotemporal As study has not been conducted. In this work, As concentration measurements were conducted in 101 wells in Guagua, Pampanga, in Central Luzon, the Philippines, from November 2018 to November 2019. The wells included 86 public hand pumps, 10 pumping stations, and 5 private, jet-powered pumps. Using hydride generation—inductively coupled plasma—optical emission spectroscopy (HG-ICP-OES), analysis of the wells in 12 barangays in Guagua revealed that 38.7% had average As concentrations beyond the 10 ppb limit with some wells having high Mn (4.0 ppm) and Fe (2.0 ppm) content as well. The high pH and reducing conditions in the wells in Guagua may have contributed to the persistence of As in the groundwater. The mean difference in wet season versus dry season As measurements were −4.4 (As < 10 ppb), −13.2 (10 to 50 ppb As), and −27.4 (As > 50 ppb). Eighty-three wells (82.2%) had higher As concentrations in the dry season, 8 wells (7.92%) had higher As concentrations in the wet season, 7 wells (6.93%) had no significant difference between the wet and dry season, and 3 wells had been decommissioned. These results indicate that there is a significant difference in As concentrations in the wet and dry seasons, and this could have implications in water treatment technology and policy implementation. The work resulted in the first year-long characterization of groundwater As in the Philippines. [ABSTRACT FROM AUTHOR]

A relatively low voltage can be favor of e- transfer and peroxide generation from dominant 2e--reduction of O2 on carbon materials as cathode, with low energy loss. In this study the conversion of As(III) in simulated high arsenic groundwater at low voltage was compared in a mixed and a anode–cathode separated electrolytic system. With applied voltages (the potential difference between cathode and anode) from 0.1 V to 0.8 V, As(III) was found to be efficiently converted to As(V) in the mixed electrolytic cells and in separated anodic cells. The complete oxidation of As(III) to As(V) at 0.1–0.8 V was also achieved on graphite in divided cathodic cells which could be long-running. The As(III) conversion process in mixed electrolytic cells, anodic cells and cathodic cells all conformed to the pseudo first-order kinetics equation. The energy consumed by As(III) conversion was decreased as the applied voltage declined. Low voltage electrolysis is of great significance for saving energy consumption and improving the current efficiency and can be applied to in-situ electrochemical pre-oxidation for As(III) in high arsenic groundwater. [ABSTRACT FROM AUTHOR]