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Chronic arsenic (As) pollution in aquifers is one of the major challenges faced by economically and socially marginalized sections of the world, which often depend heavily on groundwater for their sustenance. To safeguard these sections against As poisoning, an easy-to-use and sustainable water-treatment solution is warranted. This study was undertaken to systematically evaluate the performance and feasibility of a low-cost modified biosand filter (JalKalp) in providing potable water to affected rural households in India. JalKalp removes As by sorption on rusted-iron nails and pathogens by an additional copper layer. Initially, As-removal efficiencies of this filter were evaluated under laboratory conditions using (1) unpolluted groundwater spiked with variable concentrations (50–500 μg/L) of total dissolved arsenic (AsT), either as As(V), or As(III), or both; and (2) real As-polluted groundwater (∼150 μg/L). Results indicated that the JalKalp filter removed AsT with an efficiency of 95–99% and passed all water quality tests, except hardness and alkalinity. An ∼3-year long "JalKalp" program was then initiated to provide clean drinking water in selected villages of Bihar, India with the support of local agents, nongovernmental and governmental organizations. Filters were installed in select households (n = 22), and the community was involved in the program through training and workshops. The performance of these filters was evaluated through the testing of water and sludge generated, and the conduct of socioeconomic and health surveys. The filter was equally effective under field conditions and removed AsT (<10 μg/L), total iron (<1 mg/L), and fecal coliforms at all locations, at a cost of ∼INR 0.28 (US$ ∼0.004)/L of treated water. JalKalp requires replacement of iron nails after an estimated ∼1.7 years of treatment of ∼6,000 L of water containing 100 μg/L of AsT. Toxicity characteristic leaching procedure on As-containing sludge after filtration indicated that the sludge was not hazardous and could be disposed safely in landfills along with regular municipal waste. Findings from this study could be replicated elsewhere in providing immediate solutions to As-affected water pollution by enabling independent construction and sustainable use of this potentially long-lasting filter. [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]

A total of 45 morphologically distinct arsenic (As)‐resistant bacterial strains were isolated from the soils of different regions of Chhattisgarh, India. The minimum inhibitory concentration (MIC) values of these isolates varied widely in the range of 100‐500 mM for arsenate [As(V)] and 15‐30 mM for arsenite [As(III)]. Out of forty‐five, three isolates viz; ARP3, ARRP3, and ADT5 also revealed plant growth‐promoting properties, including phosphate solubilization and production of siderophores, indoleacetic acid, ammonia, and exopolysaccharide. Besides all these, the strains not only exhibited significant growth in the presence of As(V)/As(III) but also displayed higher efficiency (87%‐94%) of As removal from the growth medium followed by intracellular accumulation (17‐19 mg As/g). Hydride generation atomic absorption spectroscopic (HG‐AAS) analysis revealed the intracellular accumulation of As, and the structural changes that took place in these isolates were further confirmed by microscopic studies. The 16 S rRNA and phylogenetic analyses unveiled that the isolates ARP3, ARRP3, and ADT5 belonged to genera Pseudomonas, Exiguobaterium, and Microbacterium, respectively. The conducted study suggested that such beneficial bacterial strains could be conveniently exploited at a commercial level for enhancing plant growth in As‐contaminated agricultural fields, thereby improved productivity and enhanced bioremediation of soil having alarming strength of As. [ABSTRACT FROM AUTHOR]

Arsenic contamination in drinking water is a worldwide health crisis. Treatment of arsenic laden water in areas of the world such as West Bengal, India has proven to be an extremely difficult task. Practical and reliable treatment technologies that can overcome the socioeconomic and geochemical barriers present in these areas of the world must be developed. Cupric Oxide (CuO) nanoparticles have shown promising characteristics as a sorbent to remove arsenic from water. Presented in this study is, to our knowledge, the first time CuO nanoparticles have been used to treat groundwater from West Bengal that is naturally high in arsenic. Batch experiments were conducted by reacting CuO nanoparticles with sixteen groundwater samples from West Bengal that exceed 10 µg/L. All samples showed near complete removal of arsenic following the treatment with CuO nanoparticles. The removal of arsenic was unaffected by the presence of high concentrations of competing ions such as bicarbonate (HCO), phosphate (PO), and sulfate (SO) The CuO nanoparticle treatment showed no major affect on other water constituents. Overall, the results of this study suggest that CuO nanoparticles show potential as an effective sorbent of arsenic under diverse geochemical makeups. [ABSTRACT FROM AUTHOR]

Abstract: Groundwater of Assam (India) contains excessive amounts of As(III) and Fe(II). The rural and semi-urban population of Assam uses indigenous household iron filters fabricated using community prepared wooden charcoal (CPWC) to reduce Fe(II) concentration, however no efforts are made to reduce As(III) concentrations before use. The present work is directed toward assessing the potential of CPWC for metal removal from mono- and binary-metal ion systems comprising of Fe(II) and As(III) through continuous mode column studies. A decrease in breakthrough throughput volumes (V B ) from mono- and binary-metal ion systems is observed with increase in flow rates and decrease in bed depths. The order of breakthrough of metal ions observed as As(III) followed by Fe(II) from binary-metal ion system and hence the V B for As(III) is termed as critical V B as Fe(II) is yet to breakthrough through the beds. An early breakthrough for Fe(II) and As(III) from binary-metal ion system compared to respective mono-metal ion systems is observed for all the cases of flow rates and bed depths. It indicates impact on the uptake of a selected metal ion [either Fe(II) or As(III)] by the presence of the other metal ion [either As(III) or Fe(II)] present in the binary-metal ion system. The minimum and maximum errors involved between the predicted and experimental BDST curves for As(III) uptake till critical V B from the binary-metal ion system varied between 1.0% and 24.8%. [Copyright &y& Elsevier]

The contamination of groundwater by leached out arsenic has assumed an alarming proportion in several countries. Continued and prolonged ingestion even at a very low level can lead to serious arsenic-related diseases. Strong epidemiological evidence of arsenic carcinogenicity has forced the World Health Organization (WHO) to lower the maximum permissible contaminant limit (MCL) in drinking water to 10 ppb from earlier limit of 50 ppb. This has thrown a big challenge to the scientific community to devise efficient methods to purify contaminated water to such a high level. Though literature abounds in occurrence of groundwater contamination by arsenic and its removal from drinking water by laboratory techniques, millions of people continue to suffer, particularly in the developing countries like India (Bangladesh, West Bengal). Through a comprehensive review of the existing literature on the occurrence, causes, impacts and remedial measures, this article finds out what has gone wrong and what is to be done with special emphasis on membrane-based separation that seems to be highly promising in purifying arsenic-contaminated groundwater to a WHO-prescribed level. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic poisoning in drinking water is a health issue in many Asian countries including Bangladesh, India, China and Vietnam. In areas where the drinking water supply contains unsafe levels of arsenic, technologies to remove arsenic are of prime importance. Many technologies have been developed for the removal of arsenic. Among those reverse osmosis (RO) and nanofiltration (NF) are very promising techniques because they have the advantage of removing dissolved arsenic along with other dissolved and particulate compounds. So far, however, this kind of membrane filtration has needed bulky and sophisticated units, which are not suitable for application in the rural areas of developing and newly industrializing countries. Therefore the purpose of this work was to test a small-scale, commercially available marine RO desalinator with three different membrane modules on arsenic removal. The experiments were conducted with arsenic-spiked local tap water, using As(III) and As(V) up to feed concentrations of 2400 μg/L. The As(V) rejection was generally much better than the retention of As(III). With two of the tested membranes As(V) rejection was so high, that the permeate water quality complied with the WHO recommended maximum contaminant level (MCL) of 10 μg/L even at a feed concentration of 2400 mg/L. In the case of As(III) only feed concentrations below 350 μg/L resulted in permeate concentration lower than the MCL. The experiments should provide a basis for field tests on the ground in Bangladesh using natural arsenic contaminated groundwater. These field tests are currently running. [Copyright &y& Elsevier]

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]

Arsenic in groundwater is a huge problem in numerous regions of the world. Many people are exposed to high arsenic concentrations and consequently risk getting ill or even die as a result of arsenic poisoning. There are several efficient technologies for the removal of arsenic but often these methods have disadvantages, e.g. high costs for installation and/or operation, the need for chemicals or the production of arsenic contaminated filter sludge. These disadvantages can make the application difficult, especially in poor regions. Under suitable ancillary conditions the subterranean (in-situ) treatment, which is often used for iron and manganese removal from groundwater, can also be applied for the removal of arsenic and can be a cost-effective treatment technology. A field trial was carried out with a low-cost in-situ treatment plant in West Bengal/India which is described in this paper, in order to investigate whether this treatment technology is also applicable under the boundary conditions there. As for the in-situ treatment technology besides oxygen no additives are required and no arsenic contaminated filter sludge is produced this technology could be a suitable method for arsenic removal especially in poor regions. [ABSTRACT FROM AUTHOR]

Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10,000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over 2 years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 μg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 μg/L As removed per kWh) compared to before cleaning (72.9 μg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales. Image 1 • We studied the impact of electrode surface layer growth on arsenic treatment by FeEC. • After 2 years of EC plant operation, thick surface layers formed (3 distinct regions). • Surface layers decreased transport of anodically-produced Fe(II) to bulk solution. • Mechanical cleaning of electrodes restored Fe(II) transport to bulk solution. • Electrode cleaning greatly improved arsenic removal and decreased power consumption. [ABSTRACT FROM AUTHOR]

• Arsenic-contaminated water is a major public health issue in India and Bangladesh. • Laterite soil provides a novel and cost-efficient way of removing arsenic from water. • A mathematical model determines filter lifetime and an upscaling protocol. • The model captures the filter behaviour through three simple parameters. • The model plays an essential role in the filter deployment and maintenance. Arsenic is among the most hazardous contaminants present in drinking water. Recent increase in agricultural growth and fertiliser use in India and Bangladesh has led to the release of naturally occurring arsenic from the rocks, creating a major public health issue. A novel technology has been developed using naturally abundant laterite soil to filter arsenic, providing potable water to more than 5000 people. To upscale this technology and realise its full potential, a comprehensive understanding of the dependence of filter life on operating regime (flow rate, arsenic concentration and filter size) is essential. We present a mathematical model that characterises arsenic removal, circumventing the need for time-consuming experiments. The model incorporates inter- and intra-particle mass transport within the filter medium. The resulting model enables prediction of a filter lifetime in a specified role, such as on a domestic or community scale, and should assist in future filter deployment and maintenance. [ABSTRACT FROM AUTHOR]