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Arsenic (As) is one of the human carcinogens with a global peril to human health through direct or indirect exposure to contaminated water, food, air and skin contact. As a result, research on arsenic remediation has surged. However, no report evaluating the trends of studies on the subject has been documented. Therefore, the present study was conducted to examine global research trends on arsenic removal and remediation. Web of Science and Scopus were explored to retrieve published papers on the subject between 1929 and 2020. In all, 2605 articles were published within the survey period, with annual mean and growth rate of 28.63 and 11.11%, respectively. Research productivity raised consistently and peaked in 2019 (9.9%) and 2020 (9.2%). China (n = 574, 22%) ranked first followed by India (n = 361, 10%) and the United States (n = 239, 9.2%). The top 20 productive authors published articles between 19 and 49 with total citations of 442 to 511. The highest recurrent Keywords were arsenic (n = 992, 38.08%), adsorption (n = 519, 19.2%) and arsenic removal (n = 435, 16.72%). This study revealed an improved global research on Arsenic removal with greater research outputs from both developed and developing countries; however, the global collaboration appears to be low (collaboration index of 2.5), hence, the policymakers, governments and researchers should encourage international collaborations and establish research programs that can monitor arsenic contamination globally. [ABSTRACT FROM AUTHOR]

Fresh and pure water has an important role to play for healthy life. Currently, in many studies higher concentrations of contaminants like calcium, sodium, nitrate, lead, chromium, arsenic, fluoride etc. have been reported that makes the water unfit for its direct consumption. Sources and release mechanism of many such pollutants is still not known. These sources can be anthropogenic or geogenic. This paper deals with one of such contaminants namely fluoride and emphasizes on its release from various minerals viz. Gypsum, fluorite, tourmaline, actinolite, plagioclase, biotite, quartz, kayanite, epidote and orthoclase under different pH environment. It has been noted that maximum fluoride has been released from the fluorite at all pH environment (acidic, normal and alkaline) of water while minimal fluoride was released from kayanite. However, orthoclase, tourmaline and biotite can release fluoride in considerable amount. The attempts were also made to compare the release of fluoride from modern sand (Ganga sediments) with ancient sand (from sandy aquifer) under different pH condition. Outcome of studies shows that maximum fluoride released from the sand at the pH range of 6.1 to 8.2. [ABSTRACT FROM AUTHOR]

Groundwater contamination has become a serious environmental threat throughout the world in the era of Anthropocene. Thus, the present study examined the groundwater quality for irrigation purposes based on the entropy method and heavy metal pollution indices. To compute the entropy-based groundwater irrigation quality index (EIWQI), physicochemical parameters such as pH, chloride (Cl−) and nitrate (NO3−), irrigation indices including electrical conductivity (EC), sodium absorption ratio (SAR), sodium percentage (%Na), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium hazard (MH), Kelley's ration (KR), permeability index (PI) and heavy metals such as manganese (Mn), iron (Fe), zinc (Zn) and arsenic (As) have been employed for the 37 sample wells of the Damodar fan delta (DFD), India, which is a semi-critical agriculture-dominated region. Shannon's entropy method has been used to assign the weights of the different parameters for constructing the EIWQI. The results portray a spatial variation of the irrigation water quality in the DFD. The EIWQI revealed that 27.03%, 59.46%, 8.11%, 2.7% and 2.7% of the sample wells, respectively, contain excellent, good, moderate, poor and very poor quality of irrigation water. On the other hand, heavy metal pollution indices (modified degree of contamination, pollution load index, Nemerow index and modified heavy metal pollution index) show that 15–20% of sample wells of the DFD are contaminated by heavy metal pollution. The pockets of pollution are concentrated in the southwestern, northeastern and central parts of the DFD. The study found that the spatial variation in groundwater quality is controlled by the higher sodium concentration, carbonate weathering and expansion of agricultural and urban-industrial areas. [ABSTRACT FROM AUTHOR]

This article provides updated status of the arsenic affected rural habitations in India, summarizes the policy initiatives of the Ministry of Drinking Water & Sanitation (Government of India), reviews the technologies for arsenic treatment and analyses the progress made by states in tackling arsenic problems in rural habitations. It also provides a list of constraints based on experiences and recommends suggested measures to tackle arsenic problems in an holistic manner. It is expected that the paper would be useful for policy formulators in states, non-government organizations, researchers of academic and scientific institutions and programme managers working in the area of arsenic mitigation in drinking water, especially in developing countries, as it provides better insights compared to other available information in India on mitigating arsenic problems in drinking water in rural areas. [ABSTRACT FROM AUTHOR]

This study was conducted to inspect the spatial distribution, source identification, and risk assessment of groundwater arsenic (As) in different blocks that lie on the opposite banks of river Bhagirathi (a distributary of river Ganges), Murshidabad, West Bengal, India. It has been observed that the blocks that lie towards the eastern bank of river Bhagirathi have elevated arsenic and comparatively more reducing groundwater (lower oxidation–reduction potential and high iron). About 66% of groundwater samples across the district have arsenic concentration higher than the World Health Organization (WHO) permissible limit. Speciation of groundwater arsenic reveals that about 90% of arsenic species were present as arsenic (III). Further, principal component analysis (PCA) was employed to identify the controlling factors that favor the release of arsenic. PC1 comprises EC, TDS, As, Fe, TOC, and HCO3− with moderate loadings, which suggests microbially mediated degradation of organic matter (OM), helps in reductive dissolution of arsenic-bearing Fe–Mn oxyhydroxides. Results pointed out severe groundwater arsenic poisoning; hence, a health risk assessment was performed for the exposure of arsenic in groundwater, using incremental lifetime cancer risk (ILCR) models coupled with Monte Carlo simulations. On the eastern bank of river Bhagirathi, incremental lifetime cancer risk (ILCR) due to oral exposure (5th to 95th percentile values) ranged from 1.30538E − 04 to 9.31398E − 03 with a mean of 2.84194E − 03 for adults, which is 2841 times higher than the USEPA high safety risk guidelines of one in 1 million. The outcomes of the results will be useful for the policymakers and regulatory boards in defining the actual impact and deciding the pre-remediation goals. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we show how the process analysis method (PAM) can be applied to assess the sustainability of options to mitigate arsenic in drinking water in rural India. Stakeholder perspectives, gathered from a fieldwork survey of 933 households in West Bengal in 2012 played a significant role in this assessment. This research found that the ‘most important’ issues as specified by the technology users are cost, trust, distance from their home to the clean water source (an indicator of convenience), and understanding the health effects of arsenic. We show that utilisation of a technology is related to levels of trust and confidence in a community, making use of a composite trust–confidence indicator. Measures to improve trust between community and organisers of mitigation projects, and to raise confidence in technology and also in fair costing, would help to promote successful deployment of appropriate technology. Attitudes to cost revealed in the surveys are related to the low value placed on arsenic-free water, as also found by other investigators, consistent with a lack of public awareness about the arsenic problem. It is suggested that increased awareness might change attitudes to arsenic-rich waste and its disposal protocols. This waste is often currently discarded in an uncontrolled manner in the local environment, giving rise to the possibility of point-source recontamination. [Copyright &y& Elsevier]

People living in almost 50% of the districts in West Bengal are exposed to arsenic contaminated water. This paper seeks to estimate the economic costs imposed by arsenic-related health problems. We use data from a primary survey of 473 households carried out in the districts of North 24 Parganas and Midnapore. We take into account household actions to either decrease the exposure of family members to unsafe water or to alleviate the health effects of consuming arsenic-contaminated water. This allows us to assess the benefits of arsenic-safe water by estimating a three equation system that includes averting actions, medical expenditures and a sickness function. We find that by reducing arsenic concentration to the safe limit of 50 µg/l, a representative household will benefit by Rs 297 ($7) per month. The current cost of supplying filtered piped water by the Kolkata Municipal Corporation to households is Rs 127 ($3) per month per household. Thus, investing in safe drinking water is economically feasible and households are willing to pay for such investments if made aware of the effective gain in welfare. Poor households, who make up the highest proportion of arsenic-affected households and incur the largest number of sick days, will be major beneficiaries of such investments. [Copyright &y& Elsevier]

It is well known that the long-term intake of water contaminated with arsenic (As), chromium (Cr) and fluoride (F−) can develop carcinogenic and non-carcinogenic health problems. This review study for the first time presents the comprehensive data analysis of the groundwater levels of As, Cr and F− reported in different states of India. The experimental studies conducted in different regions of India were compiled for inclusive data analysis. This study emphasizes on the severe carcinogenic and non-carcinogenic impacts of these contaminants on the health of the natives. The studies published in peer reviewed journals indexed in Scopus, Science Citation Index and Web of Science have been compiled and represented systematically in order to make the interpretation more visible and clear to the scientific community. The levels of selected elements have been compared with the limits set by Bureau of Indian Standards and World Health Organization and further interpreted for the health hazards of the natives of that particular region. The highest concentration of As, Cr and F− reported in India remained 1.36 mg/L (West Bengal), 33.80 mg/L (Uttar Pradesh) and 85 mg/L (Haryana), respectively. These values were 136, 676 and 57 times higher than the standard limits set for these elements (0.01 mg/L; 1.0 mg/L and 0.05 mg/L, respectively). The state-wise patterns of concentration levels have been shown in graphical forms. This review also highlights the regions severely affected due to As, Cr and F− contamination and reveals the research gaps. [ABSTRACT FROM AUTHOR]

Geogenic arsenic contamination in groundwaters poses a severe health risk to hundreds of millions of people globally. Notwithstanding the particular risks to exposed populations in the Indian sub-continent, at the time of writing, there was a paucity of geostatistically based models of the spatial distribution of groundwater hazard in India. In this study, we used logistic regression models of secondary groundwater arsenic data with research-informed secondary soil, climate and topographic variables as principal predictors generate hazard and risk maps of groundwater arsenic at a resolution of 1 km across Gujarat State. By combining models based on different arsenic concentrations, we have generated a pseudo-contour map of groundwater arsenic concentrations, which indicates greater arsenic hazard (> 10 μg/L) in the northwest, northeast and south-east parts of Kachchh District as well as northwest and southwest Banas Kantha District. The total number of people living in areas in Gujarat with groundwater arsenic concentration exceeding 10 μg/L is estimated to be around 122,000, of which we estimate approximately 49,000 people consume groundwater exceeding 10 µg/L. Using simple previously published dose–response relationships, this is estimated to have given rise to 700 (prevalence) cases of skin cancer and around 10 cases of premature avoidable mortality/annum from internal (lung, liver, bladder) cancers—that latter value is on the order of just 0.001% of internal cancers in Gujarat, reflecting the relative low groundwater arsenic hazard in Gujarat State. [ABSTRACT FROM AUTHOR]

A low-cost arsenic removal method based on oxidation-coagulation at optimized pH (OCOP), which is popular as Arsiron-Nilogon in Assam, India, uses KMnO4 to remove arsenic and oxidation of As(III) to As(V) before coagulation using FeCl3. In this method KMnO4 shows a major role in oxidation and removal of arsenic from the water. However, the relative efficacy of other oxidants, viz., Fenton's reagent, NaOCl and H2O2, visa vis KMnO4, in OCOP method has not yet been studied systematically. Here we report a comparative study of the removal of arsenic by OCOP with different oxidising agents, viz., KMnO4, Fenton's reagent, NaOCl and H2O2 keeping the doses of NaHCO3 and FeCl3 constant at 100 and 25 mg/L, respectively. A set of OCOP experiments performed with varying KMnO4 dose from 0.2 to 2 mg/L at an interval of 0.2 was examined. This set of OCOP experiments also verified the other oxidants taken in equivalent of the dose of KMnO4. Filtered water taken after 2 h gives result of arsenic removal and oxidation extent of each oxidant. In the OCOP method of arsenic removal, the performance of the four chosen oxidants increases in the order H2O2 < NaOCl Fenton's reagent < KMnO4. With other conditions remaining the same, 2 mg/L KMnO4 and equivalent quantities of Fenton's reagent, NaOCl and H2O2 could remove As3+ from initial concentration 200 μg/L in water to maximum 100, 98.8, 89.0 and 88.0%, respectively. The much better performance of KMnO4 and Fenton's reagent as compared to that of H2O2 and NaOCl is due to additional adsorption of arsenic by MnO2 and FeOOH formed from KMnO4 and ferrous iron of Fenton's reagent. The results also suggest a role of MnO2 in previously reported catalysis of oxidation of As3+ to As5+. The adsorption isotherms suggest that arsenic is adsorbed on the surface as well as inside coagulates/precipitates mixtures of FeOOH and MnO2 produced during the OCOP process. [ABSTRACT FROM AUTHOR]

Presence of arsenic ion [As(V)] in ground water at different locations of India is a big health concern in present days. In this work, effort was made to remove As(V) ions from tap water by electrocoagulation (EC) using iron (Fe) electrodes having an effective surface area of 38.67 m2/m3. Investigation was focused on studying the effects of various process parameters of EC like solution pH, current density (CD), inter-electrode distance (IED) initial arsenic concentration (Co), electrical conductivity of water on removal of As(V) in efficient ways. Experimental results reveal that initial pH of 7, CD of 0.431 mA/cm2, IED of 0.5 cm, agitation speed of 200 rpm and NaCl dose of 0.33 g/L are optimal conditions to reduce As(V) ion concentration from 100 µg/L to below 10 µg/L. Overall, 99.4% As(V) removal was achieved at 30 minutes of EC treatment. Different quality parameters for drinking water such as TDS, turbidity, salinity, electrical conductivity were also assessed during the EC, to verify drinking water quality in several aspects. Kinetic analysis infers that As(V) removal by EC follow the first order reaction model. Present study affirms that, EC is an effective technique for efficient As(V) removal from drinking water with an estimated energy consumption of 8.33 × 10−3 Kwh/m3, electrode utilization of 0.0486 kg/m3, and operational cost of 0.0488 US$/m3. [ABSTRACT FROM AUTHOR]

Arsenic contamination in drinking water is a great concern in different regions of the world as well as in India. Several technologies have been investigated to remove arsenic from water, such as coagulation and co-precipitation, ion exchange, adsorption, and reverse osmosis. In the present research, electrocoagulation with iron electrodes has been assessed as a treatment technology for arsenic removal from groundwater to reach concentrations below 0.01 mg/L (WHO limit) and which is technically effective, affordable for the local area, and easy to operate and maintain. Electrochemically generated iron is converted to hydrated ferric oxide within the contaminated water, which takes up the arsenic from water. A downstream filtration unit (sand or activated alumina) is applied to remove ferric hydroxide flocs produced during the process. The laboratory experiments were conducted in a batch reactor using iron plates as electrodes with monopolar configuration to study the effects of initial pH and electro-charge loading (ECL) on arsenic removal. The optimum operating condition was observed for an electro-charge loading of 25–30 Coulombs/L at pH 7.0 and an initial arsenic concentration of 0.2 mg/L. Two field trials were implemented in West Bengal after suitably designing the electrocoagulation system. Arsenic removal was significant (75–80%) delivering safe water with arsenic below 0.01 mg/L (acceptable limit). Passivation of the electrodes occurred during the operation and calcium-based (including iron) deposition was observed on the cathodes. Passivation is avoidable after running regular polarity reversal of the electrodes. [ABSTRACT FROM AUTHOR]

Arsenic (As) toxicity is a global phenomenon, and it is continuously threatening human life. Arsenic remains in the Earth's crust in the forms of rocks and minerals, which can be released into water. In addition, anthropogenic activity also contributes to increase of As concentration in water. Arsenic-contaminated water is used as a raw water for drinking water treatment plants in many parts of the world especially Bangladesh and India. Based on extensive literature study, adsorption is the superior method of arsenic removal from water and Fe is the most researched periodic element in different adsorbent. Oxides and hydroxides of Fe-based adsorbents have been reported to have excellent adsorptive capacity to reduce As concentration to below recommended level. In addition, Fe-based adsorbents were found less expensive and not to have any toxicity after treatment. Most of the available commercial adsorbents were also found to be Fe based. Nanoparticles of Fe-, Ti-, Cu-, and Zr-based adsorbents have been found superior As removal capacity. Mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.) removed As efficiently from water. Oxidation of AsO33− to AsO43−and adsorption of oxidized As on the mixed element-based adsorbent occurred by different adsorbents. Metal organic frameworks have also been confirmed as good performance adsorbents for As but had a limited application due to nano-crystallinity. However, using porous materials having extended surface area as carrier for nano-sized adsorbents could alleviate the separation problem of the used adsorbent after treatment and displayed outstanding removal performances. [ABSTRACT FROM AUTHOR]

A sonochemical reduction method of permanganate (MnO4−) was utilized for preparation of manganese dioxide (MnO2) coating on the surface of XAD-4 resin. Characterization of the modified MnO2-coated XAD-4 resin (MX-4) was done and sorption studies were carried out using arsenic (76As) radiotracer. The adsorption capacity for As(III) and As(V) using MX-4 were 5.5 mg/g and 7.6 mg/g, respectively. The MX-4 resin was successfully applied for quantitative removal of arsenic from two ground water samples collected from arsenic contaminated regions of North 24 Parganas, West Bengal, India. A schematic mechanism of removal of arsenic by MX-4 beads was also suggested. [ABSTRACT FROM AUTHOR]

In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed, low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected from the river and its tributaries at low discharge during winter and summer seasons and were analysed by ICP-MS. Dissolved As and Fe concentrations were found in the range of 1.29–9.62 and 47.84–431.92 μg/L, respectively. Arsenic concentration in the Gomati River water has been detected higher than in its tributaries water and characteristically increases in downstream, attributed to the downstream increasing of Fe2O3 content, sedimentary organic carbon and silt-clay content in the river sediments. Significant correlation of determination ( r 2 = 0.68) was also observed between As and Fe concentrations in the river water. Arsenic concentrations in the river water are likely to follow the seasonal temperature variation and reach the level of World Health Organization’s permissible limit (10 μg/L) for drinking water in summer season. The Gomati River longitudinally develops reducing conditions after the monsoon season that mobilize As into the river water. First, dissolved As enters into pore-water of the river bed sediments by the reductive dissolution of Fe-oxides/hydroxides due to microbial degradation of sedimentary organic matter. Thereafter, it moves upward as well as down slope into the river water column. Anthropogenically induced biogeochemical processes and tropical climatic condition have been considered the responsible factors that favour the release of As in the fluvial environment of the Ganga Plain. The present study can be considered as an environmental alarm for future as groundwater resources of the Ganga–Brahmaputra Delta are seriously affecting the human–environment relationship at present. [ABSTRACT FROM AUTHOR]

A plethora of technologies has been developed over decades of extensive research on arsenic remediation, although the technical and financial perspective of arsenic removal plants in the field requires critical evaluation. In the present study, focusing on some of the pronounced arsenic-affected areas in West Bengal, India, we assessed the implementation and operation of different arsenic removal technologies using a dataset of 4000 spatio-temporal data collected from an in-depth field survey of 136 arsenic removal plants engaged in the public water supply. Our statistical analysis of this dataset indicates a 120% rise in the average cumulative capacity of the plants during 2014–2021. The majorities of the plants are based on the activated alumina with FeCl3 technology and serve about 49% of the population in the study area. The average cost of water production for the activated alumina with FeCl3 technology was found to be ₹7.56/m3 (USD $1 ≈ INR ₹70), while the lowest was ₹0.39/m3 for granular ferric hydroxide technology. A machine learning-based framework was employed to analyze the impact of water quality and treatment plant parameters on the removal efficiency, capital, and operational cost of the plants. The artificial neural network model exhibited adequate statistical significance, with a high F-value and R2 of 5830.94 and 0.72 for the capital cost model, 136,954, and 0.98 for the operational cost model, respectively. The relative importance of the process variables was identified through random forest models. The models indicated that flow rate, media, and chemicals are the predominant costs, while contaminant loading in influent water and a coagulating agent was important for removal efficiency. The established framework may be instrumental as a decision-making tool for water providers to assess the expected performance and financial involvement for proposed or ongoing arsenic removal plants concerning various design and quality parameters. [ABSTRACT FROM AUTHOR]