| 1. |
- Ahmad, Arslan, et al.
(författare)
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Mobility and redox transformation of arsenic during treatment of artificially recharged groundwater for drinking water production
- 2020
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigate opportunities for reducing arsenic (As) to low levels, below 1 mu g/L in produced drinking water from artificially infiltrated groundwater. We observe that rapid sand filtration is the most important treatment step for the oxidation and removal of As at water treatment plants which use artificially recharged groundwater as source. Removal of As is mainly due to As co-precipitation with Fe(III)(oxyhydr)oxides, which shows higher efficiency in rapid sand filter beds compared to aeration and supernatant storage. This is due to an accelerated oxidation of As(III) to As(V) in the filter bed which may be caused by the manganese oxides and/or As(III) oxidizing bacteria, as both are found in the coating of rapid sand filter media grains by chemical analysis and taxonomic profiling of the bacterial communities. Arsenic removal does not take place in treatment steps such as granular activated carbon filtration, ultrafiltration or slow sand filtration, due to a lack of hydrolyzing iron in their influent and a lack of adsorption affinity between As and the filtration surfaces. Further, we found that As reduction to below 1 mu g/L can be effectively achieved at water treatment plants either by treating the influent of rapid sand filters by dosing potassium permanganate in combination with ferric chloride or by treating the effluent of rapid sand filters with ferric chloride dosing only. Finally, we observe that reducing the pH is an effective measure for increasing As co-precipitation with Fe(III)(oxyhydr)oxides, but only when the oxidized arsenic, As(V), is the predominant species in water.
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| 2. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Tubewell platform color : Assessment of a tool for rapid screening of arsenic and manganese in well water
- 2012
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Ingår i: UNDERSTANDING THE GEOLOGICAL AND MEDICAL INTERFACE OF ARSENIC, AS 2012. - : CRC PRESS-TAYLOR & FRANCIS GROUP. ; , s. 515-518
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Konferensbidrag (refereegranskat)abstract
- This study attempts to make a statistical comparison between Tubewell (TW) platform color and the level of Arsenic (As) and Manganese (Mn) concentration in groundwater abstracted from a set of 423 Tubewells (TWs) in Chakdaha Block of Nadia District, West Bengal, India to validate platform color as a screening tool for both As and Mn in groundwater. The results indicate that water extracted from TWs with black colored platform in 93% cases was safe for As while water extracted from TWs with red colored platform is contaminated with As with 38% certainty, compared to drinking water standard of India (50 mu g/L). At this standard the respective efficiency, sensitivity and specificity of the tool are 65, 85 and 59%. If WHO drinking water guideline (10 mu g/L) is considered, the certainty increases to 73% and 84% respectively for black and red colored platform with respective efficiency, sensitivity and specificity values of 79, 77 and 81%. Furthermore, the black colored platform with 78% certainty indicates well water is enriched with Manganese (Mn), while red colored platform indicates water is low in Mn with 64% certainty evaluated against Indian national standard of 300 mu g/L. This study demonstrates that platform color can be potentially used as an initial screening tool for As and Mn, to assess the safe water acess for drinking purposes.
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| 3. |
- Herath, Indika, et al.
(författare)
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Natural Arsenic in Global Groundwaters : Distribution and Geochemical Triggers for Mobilization
- 2016
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Ingår i: CURRENT POLLUTION REPORTS. - : SPRINGER HEIDELBERG. - 2198-6592. ; 2:1, s. 68-89
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Tidskriftsartikel (refereegranskat)abstract
- The elevated concentration of arsenic (As) in the groundwaters of many countries worldwide has received much attention during recent decades. This article presents an overview of the natural geochemical processes that mobilize As from aquifer sediments into groundwater and provides a concise description of the distribution of As in different global groundwater systems, with an emphasis on the highly vulnerable regions of Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead to the contamination of groundwaters by increased As concentrations. The primary source of As in groundwater is predominantly natural (geogenic) and mobilized through complex biogeochemical interactions within various aquifer solids and water. Sulfide minerals such as arsenopyrite and As-substituted pyrite, as well as other sulfide minerals, are susceptible to oxidation in the near-surface environment and quantitatively release significant quantities of As in the sediments. The geochemistry of As generally is a function of its multiple oxidation states, speciation, and redox transformation. The reductive dissolution of As-bearing Fe(III) oxides and sulfide oxidation are the most common and significant geochemical triggers that release As from aquifer sediments into groundwaters. The mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. According to recent estimates, more than 130 million people worldwide potentially are exposed to As in drinking water at levels above the World Health Organization's (WHO's) guideline value of 10 mu g/L. Hence, community education to strengthen public awareness, the involvement and capacity building of local stakeholders in targeting As-safe aquifers, and direct action and implementation of best practices in identifying safe groundwater sources for the installation of safe drinking water wells through action and enforcement by local governments and international water sector professionals are urgent necessities for sustainable As mitigation on a global scale.
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| 4. |
- Mahanta, C., et al.
(författare)
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Geochemical evidences in the release processes of Arsenic into the groundwater in a part of Brahmaputra Floodplains
- 2012
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Ingår i: METALS AND RELATED SUBSTANCES IN DRINKING WATER. - : IWA PUBLISHING. ; , s. 268-271
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Konferensbidrag (refereegranskat)abstract
- To understand the sources and mobilization processes responsible for arsenic enrichment in groundwater in the Brahmaputra Basin where higher arsenic concentration have been reported, the geochemical features of the aquifer sediments were studied. Six boreholes were drilled near the tubewells (1 and 2) where aqueous arsenic concentration varies between 250 - 350 mu g/l. The soil sediment was collected at 3 m (10 ft) interval and it was drilled to the depth of 45 m (150 ft) which is the common depth of the tubewell installed in the study area. The bulk chemical studies on the sediments show that the pH of soils varies from 4.2 to 5.2 with a mean value of 4.75. The groundwater composition in the study area is of Na-HCO3-. The major anions HCO3- is likely from the decomposition of organic matter and originates from weathering of silicate and calcite minerals by atmospheric or respired CO2. Selective sequential extraction (SSE) method proposed by Wenzel et al., (2001) for extraction of arsenic from soil was used. Results of sequential extraction experiment show that solid-phase arsenic is present predominantly in the reducible fraction (Ext_5 and Ext_6), and residual fraction (Ext_7) contributes to highest fraction in many soil sediment. The major processes of arsenic mobilization probably linked to desorption of As from Fe oxides/oxyhydroxides and the reductive dissolution of Fe rich phases in the aquifers sediments under reducing and alkaline conditions.
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| 5. |
- Mahanta, C., et al.
(författare)
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Source, distribution and release mechanisms of arsenic in the groundwater of Assam floodplains of Northeast India
- 2008
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Ingår i: World Environmental and Water Resources Congress 2008: Ahupua'a - Proceedings of the World Environmental and Water Resources Congress 2008. - Reston, VA : American Society of Civil Engineers. - 9780784409763
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Konferensbidrag (refereegranskat)abstract
- This study conducted in Bongaigaon and Darrang districts of Assam, India is based upon water chemistry and sediment characteristics investigation in an reportedly arsenic infested belt. Of total 50 sampled wells, 15 had arsenic concentration above national drinking water standard of 50 μg/l, and 33 had As concentrations above the WHO guideline of 10 μg/l. However no distinct zones or depths with specific sedimentological features could be identified. Sediments with colour on green-olive scale are probably more likely to bear As contaminated water than white sediments. Sand filters used to reduce high iron content seem to reduce As content of water effectively. Arsenic rich water is also partly avoided since drillers seek water low in iron, which is often also low in arsenic content. Reductive dissolution of Ferric hydroxides is believed to be the release mechanism controlling the mobility of arsenic, rather than oxidation of arsenopyrite or pH induced desorption.
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| 6. |
- Mukherjee, A., et al.
(författare)
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Wide spread arsenic in deeper groundwater of western Bengal basin, West Bengal, India : Implications for sustainable alternate drinking water sources
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012. - : Taylor & Francis Group. ; , s. 522-525
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Konferensbidrag (refereegranskat)abstract
- Availability of safe drinking water is a major concern in the delta plains of the major Himalayan-Tibetan rivers in southern and southeastern Asia. While indiscriminate use of rivers and other surface water bodies for disposal of sewage and industrial waste has rendered them non-potable, natural, non-point source, elevated Arsenic (As) concentrations in groundwater exceeding the World Health Organization's (WHO) guideline value for drinking water of 0.01 mg/L have put millions of people at risk. Hence, finding an alternate, suitable and sustainable drinking-water source has been a priority in these areas. Generally, higher concentrations of dissolved As are found in groundwater of shallower aquifers and several studies have advocated deeper aquifers as a possible safe substitute. Using a composite hydrogeological approach, we demonstrate that regional-scale deeper groundwater As contamination in the western Bengal basin is dependent on the aquifer-aquitard framework and complex redox processes with partial equilibrium under natural flow conditions. Widespread deep irrigation pumping may be drawing shallower, contaminated groundwater down to greater depths. These findings have severe implications on finding alternate drinking water sources, in West Bengal, and adjoining areas of Bangladesh, with plausible similar geological and hydrogeological framework.
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| 7. |
- Shah, M., et al.
(författare)
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Assessment of geothermal water quality for industrial and irrigation purposes in the Unai geothermal field, Gujarat, India
- 2019
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 8, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays, a spotlight on the direct manipulation of water from the geothermal fields is laid for manifold applications. This manuscript discusses the utilization of water produced from geothermal wells for irrigation and industrial purposes. In order to identify the suitability of the water for the above mentioned uses, various hydrochemical parameters were evaluated. Samples were collected from three geothermal well sites from Unai village, a prominent geothermal field situated in Navsari district, Gujarat, India. The hydrochemistry of the samples collected from hot spring (depth 30–45 m) was studied and samples were examined by calculating different parameters. The complete study was done individually for both industrial and irrigational uses of geothermal water. The mean surface temperature of the water is 55 °C and average pH of the sample studied is 8.12. The key Water Quality Indices (WQI) such as Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI) and Larson-Skold Index (LS) were examined for industrial utilization and the key indices like Sodium Absorption Ratio (SAR), Sodium Percentage (SP), Kelly Ratio (KR) Residual Sodium Carbonate (RSC) and Permeability Index (PI) were examined for irrigational utilization of geothermal water. LSI and RSI values show that carbonate and bicarbonate concentration is in the desirable range, however, LS (15.09, 13.54) is very high which indicates higher Cl- content. High value of indices such as SAR, KR, and SP points out the increased concentration of Na+ in the water sample. The results of this study would help the end users to identify the necessary water-treatments before utilizing the water for industrial and irrigation purposes in the study area.
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| 8. |
- Ahmad, Arslan, et al.
(författare)
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Impact of phosphate, silicate and natural organic matter on the size of Fe(III) precipitates and arsenate co-precipitation efficiency in calcium containing water
- 2020
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Ingår i: Separation and Purification Technology. - : ELSEVIER. - 1383-5866 .- 1873-3794. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- Removal of arsenic (As) from water by co-precipitation with Fe(III) (oxyhydr)oxides is a widely used technique in water treatment. Nevertheless, As removal efficiency appears to be sensitive to the composition of the water matrix. The aim of this study was to gain a deeper understanding of the independent and combined effects of silicate (Si), phosphate (P), natural organic matter (NOM) and calcium (Ca) on arsenate [As(V)] co-precipitation efficiency and the size of Fe(III) precipitates. We found that, in complex solutions, containing multiple solutes and high levels of Ca, (variations in) Si and P concentrations reduce As(V) removal to some extent, mainly due to a decreased adsorption of As(V) onto Fe(III) precipitates. On the other hand, NOM concentrations reduced As(V) removal to a much greater extent, due to possible formation of mobile Fe(III)-NOM complexes that were difficult to remove by filtration. These findings have a great significance for predicting As(V) removal as a function of seasonal and process-related water quality changes at water treatment plants.
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| 9. |
- Annaduzzaman, Md., et al.
(författare)
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Characterization of a chitosan biopolymer and arsenate removal for drinking water treatment
- 2014
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Ingår i: One Century of the Discovery of Arsenicosis in Latin America (1914-2014). - : CRC Press. - 9781138001411 ; , s. 745-747
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Konferensbidrag (refereegranskat)abstract
- Chitosan biopolymer with a deacetylation degree of 85%, was assessed for its capability to adsorb As(V) from drinking water by batch experiments. To characterize the chitosan biopolymer, chitosan was analyzed by FTIR and SEM. The results showed that chitosan is an effective and promising sorbent for As(V) from drinking water. From the batch tests, results showed a maximum adsorption of 355 μg/L of As(V) with 1.18 μg g-1 adsorption capacity at pH 6. The kinetic data, obtained at pH 6 could be fitted with pseudo-second order equation (adsorption capacity: 0.923 μg g-1) and the process was suitably described by a Freundlich (R2 = 0.9933) model than by a Langmuir model (R2 = 0.9741). The results above indicated that chitosan is a very favorable sorbent for As(V) removal from aqueous solution.
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| 10. |
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