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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. [ABSTRACT FROM AUTHOR]

To elucidate the distribution of arsenic in shallow aquifers of the Guangzhou region (South China), 85 groundwater samples were collected and 18 chemical parameters of them were analyzed. The arsenic concentration of groundwater ranged from below detection limit to 0.13 mg/L. The results showed that those areas with high arsenic concentration were characterized by porous aquifers, low-lying, relief topography and close proximity to fault belt and rivers. The reductive dissolution of Fe (hydr)oxides is the main control mechanism for arsenic enrichment in the river delta region where groundwater is mainly characterized by a reducing environment. This mechanism was well embodied in the areas with these geological and geographical features. Agricultural fertilizer could produce high levels of nitrate in groundwater and the reduction of it could restrain the enrichment of arsenic. Industrial effluents, sewage irrigation and the probable leakage from sewers could promote the arsenic content in groundwater by lateral flow and infiltration. In addition, the effect of ion competition between phosphate and arsenic occurred in sewer leakage areas characterized by middle-high construction leading to the elevation of arsenic concentrations. The arsenic distribution in groundwater was caused by these natural and anthropogenic factors jointly. [ABSTRACT FROM AUTHOR]

In the Municipality of Chimaltenango, Guatemala, we sampled groundwater for total inorganic arsenic. In total, 42 samples were collected from 27 (43.5%) of the 62 wells in the municipality, with sites chosen to achieve spatial representation throughout the municipality. Samples were collected from household faucets used for drinking water, and sent to the USA for analysis. The only site found to have a concentration above the 10 μg/L World Health Organization provisional guideline for arsenic in drinking water was Cerro Alto, where the average concentration was 47.5 μg/L. A health risk assessment based on the arsenic levels found in Cerro Alto showed an increase in noncarcinogenic and carcinogenic risks for residents as a result of consuming groundwater as their primary drinking water source. Using data from the US Geological Survey and our global positioning system data of the sample locations, we found Cerro Alto to be the only site sampled within the tertiary volcanic rock layer, a known source of naturally occurring arsenic. Recommendations were made to reduce the levels of arsenic found in the community's drinking water so that the health risks can be managed. [ABSTRACT FROM AUTHOR]

Groundwater arsenic contamination has caused a significant public health burden in lowland regions of Nepal. For arsenic mitigation purposes, the Kanchan Arsenic Filter (KAF) was developed and validated for use in 2003 after pilot studies showed its effectiveness in removing arsenic. However, its efficacy in field conditions operating for a long period has been scarcely observed. In this study, we observe the efficacy of KAFs running over 6 months in highly arsenic-affected households in Nawalparasi district. We assessed pair-wise arsenic concentrations of 62 randomly selected household tubewells before filtration and after filtration via KAFs. Of 62 tubewells, 41 had influent arsenic concentration exceeding the Nepal drinking water quality standard value (50 μg/L). Of the 41 tubewells having unsafe arsenic levels, KAFs reduced arsenic concentration to the safe level for only 22 tubewells, an efficacy of 54%. In conclusion, we did not find significantly high efficacy of KAFs in reducing unsafe influent arsenic level to the safe level under the in situ field conditions. [ABSTRACT FROM AUTHOR]

Arsenic is a known carcinogen found globally in groundwater supplies due to natural geological occurrence. Levels exceeding the internationally recognized safe drinking water standard of 10 µg/L have been found in private drinking water supplies in many parts of Canada and the United States. Emerging epidemiological evidence confirms groundwater arsenic to be a significant health concern, even at the low to moderate levels typically found in this region. These findings, coupled with survey data reporting limited public adherence to testing and treatment guidelines, have prompted calls for improved protective measures for private well users. The purpose of this review is to assess current jurisdictional provisions for private well water protection in areas where arsenic is known to naturally occur in groundwater at elevated levels. Significant limitations in risk management approaches are identified, including inconsistent and uncoordinated risk communication approaches, lack of support mechanisms for routine water testing and limited government resources to check that testing and treatment guidelines are followed. Key action areas are discussed that can help to build regulatory, community and individual capacity for improved protection of private well water supplies and enhancement of public health. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the in situ bioprecipitation (ISBP) and zero-valent iron (ZVI) for removal of arsenic from groundwater. Batch experiments were set up to test the metal/oxyanion removal efficiency using the processes induced by ZVI, by ISBP and by combining both technologies. For the construction of microcosms in anaerobic condition, aquifer material was mixed with synthetic groundwater in serum bottles. Solutions that contained commercial iron (powder, filings), iron from foundry (chips) and lactate with the carbon concentration of 0.02% (w/v) were amended. After 57 days the pH increased to 7.9 in the microcosm with lactate+ iron chips. In the microcosms amended with lactate+ commercial iron (powder and filings), pH was between 6.9 and 7.5 The highest decrease in sulfate concentrations was observed in the microcosm supplied with lactate (from 1,976 to 630 mg/L), and with lactate+ iron filings (from 1,985 to 1,280 mg/L). The results showed that ISBP and ZVI can be efficient in the removal of As from groundwater; however, it strongly depends on the type and particle size of ZVI. The most effective was commercial ZVI. The highest decrease in As concentration was observed in the microcosm supplied with ethanol and iron powder (from 4,832 to 131 μg/L). [ABSTRACT FROM AUTHOR]

In the Southeast Asia region, arsenic contamination of groundwater has been reported in several countries and a large number of arsenic treatment units were installed in many regions. Microbial activity can greatly affect the mobilization of arsenic under anaerobic conditions when coupled with the oxidation of organic matter. In this study, a mathematical model was developed to predict the bioleaching of arsenic in response to organic matter contamination in the treatment unit. Calibration of the model was performed using the data of batch experiments, and finally the results obtained from the laboratory experiments were used to verify the developed model. The microbial decomposition of organic matter led to an anaerobic condition within the accumulated sludge in the sand filter and hence caused the bioleaching of arsenic. Under the inoperative condition of the treatment unit for 5, 10, and 15 days along with organic matter contamination of 15 mg/L as biochemical oxygen demand, the concentrations of bioleached arsenic were found to be 59, 184, and 275 µg/L, respectively. This study revealed the bioleaching potential of arsenic due to organic matter inclusion in the treatment process, which might contribute in designing safe options for drinking water. [ABSTRACT FROM AUTHOR]

Rivers used for drinking water production might be subject to anthropogenic pollution discharge upstream of the intake point. This problem was investigated in the case of the Moselle River, used for water production in Nancy (350,000 inhabitants) and which might be impacted by industrial activities 60 kmupstream. The arsenic flux of a pulp and paper mill discharging in the Moselle River at this location has been more specifically investigated. The main sources of arsenic in that mill seemed to be the recovered papers and the gravel pit water used as feed water. The arsenic input related to wood and bark was limited. The main arsenic outputs from the plant were the paper produced on site and the deinking sludge. The arsenic concentration in the effluent of the wastewater treatment plant (WWTP) was not correlated to the one in the gravel pit water, but may depend on the operating conditions of the WWTP or the changes in processes of the mill. The impact of this anthropogenic source of arsenic on the Moselle River was slightly larger in summer, when the flowrate was lower. Globally the impact of the paper mill on the Moselle River water quality was limited in terms of arsenic. [ABSTRACT FROM AUTHOR]

Arsenic is a widespread contaminant in the environment around the world. The most abundant species of arsenic in groundwater are arsenite [As(III)] and arsenate [As(V)]. Several arsenic removal processes can reach good removal yields only if arsenic is present as As(V). For this reason it is often necessary to proceed with a preliminary oxidation of As(III) to As(V) prior to the removal technology. Several studies have focused on arsenic oxidation with conventional reagents and advanced oxidation processes. In the present study the arsenic oxidation was evaluated using hydrogen peroxide, UV radiation and their combination in distilled and in real groundwater samples. Hydrogen peroxide and UV radiation alone are not effective at the arsenic oxidation. Good arsenic oxidation yields can be reached in presence of hydrogen peroxide combined with a high UV radiation dose (2,000 mJ/cm2). The quantum efficiencies for As(III) oxidation were calculated for both the UV photolysis and the UV/H2O2 processes. [ABSTRACT FROM AUTHOR]

Arsenic (As) was removed electrochemically from underground water (GW) by electrocoagulation (EC) process employing a bipolar cell configuration with continuous flow using iron electrodes. A kinetic model derived from the Lagergren equation was applied to specify the kinetics of the arsenic removal reaction. Elucidation of the effect of the liquid flow rate on the treatment time and on the simulation results of the model was achieved. The results showed that treatment times decreased from 10.50 min to 0.75 min as the flow rate decreased from 3.500 to 0.875 L min-1 and the current density varied from 15 to 45Am-2 respectively. The used sorption kinetic model successfully describes the arsenic removal by this process. The coefficients of determination were found to be very high in all cases (R2 > 0.99) indicating a good fit of the experimental data to Lagergren model. [ABSTRACT FROM AUTHOR]

One of the problems in drinking water that raises concern over the world is that millions of people still have to use arsenic-contaminated water. There is a worldwide need to develop appropriate technologies to remove arsenic from water for household and community water supply systems. In this study, a new material namely iron oxide coated sponge (IOCSp) was developed and used to remove arsenic (As) from contaminated groundwater in Vietnam. The results indicated that IOCSp has a high capacity in removing both As (V) and As (III). The adsorption capacity of IOCSp was up to 4.6 mg As/g IOCSp, showing better than many other materials. It was observed from a pilot study that a small quantity of IOCSp (180 g) could reduce As concentration of 480 μg/L in 1.5 m³ of contaminated natural water to below 40 μg/L. In addition, an exhausted IOCSp, containing a large amount of arsenic (up to 0.42 wt %) could safely be disposed through the solidification/stabilization with cement. Addition of fly ash also reduced the amount of arsenic in the leachate. [ABSTRACT FROM AUTHOR]

In parts of the western United States groundwater used for drinking water contains high concentrations of metals, including arsenic. In a rural county in Nevada, USA, we measured concentrations of arsenic and tungsten and the proportion of arsenic occurring in trivalent form (As(III)) in tap water samples from private domestic wells in 307 households. The proportion of arsenic occurring as As(III) ranged from 0 to 100% (ave. 21%, median 1%). Tungsten concentrations ranged from 0 to 610 μmg l-1 (ave. 26 μmg l-1, median 2 μmg l-1). Among 253 respondents who consumed water: (a) 177/253 (70%) of tap water samples contained more than 10 μmg l-1 total inorganic arsenic (ave. 66 μmg l-1, median 20 μmg l-1); (b) As(III) occurred as a small proportion of total arsenic in most samples (ave. 22%, median 3%); and (c) tungsten occurred in concentrations ranging from below the detection limit (3 μmg l-1) to a maximum of 610 μmg l-1 (ave. 30 μmg l-1, median 3 μmg l-1). Log10 concentrations of tungsten and total arsenic in consumed water were positively correlated (log10[W] = 20.400 + 0.703(log10[AsT]), p = 0.000+, adj. r² = 0.53). This suggests that householders in this area were likely to be exposed to both metals simultaneously, given that 253/307 of the respondents (82%) reported consuming tap water. [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]

The presence of arsenic in groundwater has been of great public concern because of its high toxicity. For purification of arsenic-contaminated groundwater, bacterial oxidation of arsenite, As(III), with a chemical adsorption process was examined in this study. After As(III) oxidation to arsenate, As(V), arsenic is easily removable from contaminated groundwater because As(V) is more adsorptive to absorbents than As(III). By acclimation to As(III) of high concentrations, a mixed culture of heterotrophic bacteria with high As(III)-oxidizing activity was obtained from a soil sample that was free from contamination. With initial concentration up to 1,500mg l-1 As(III), the mixed culture showed high As(III)-oxidizing activity at pH values of 7-10 and at temperatures of 25-35°C. The mixed culture contained several genera of heterotrophic As(III)-oxidizing and arsenic-tolerant bacteria: Haemophilus, Micrococcus, and Bacillus. Activated alumina was added to the basal salt medium containing 75mg l-1 As(III) before and after bacterial oxidation. Arsenic removal by activated alumina was greatly enhanced by bacterial oxidation of As(III) to As(V). The isotherms of As(III) and As(V) onto activated alumina verified that bacterial As(III) oxidation is a helpful pretreatment process for the conventional adsorption process for arsenic removal. [ABSTRACT FROM AUTHOR]