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| 2. |
- Ahmad, Arslan, et al.
(författare)
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Characteristics of Fe and Mn bearing precipitates generated by Fe(II) and Mn(II) co-oxidation with O-2, MnO4 and HOCl in the presence of groundwater ions
- 2019
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 161, s. 505-516
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we combined macroscopic measurements of precipitate aggregation and chemical composition (Mn/Fe solids ratio) with Fe and Mn K-edge X-ray absorption spectroscopy to investigate the solids formed by co-oxidation of Fe(II) and Mn(II) with O-2, MnO4, and HOCl in the presence of groundwater ions. In the absence of the strongly sorbing oxyanions, phosphate (P) and silicate (Si), and calcium (Ca), O-2 and HOCl produced suspensions that aggregated rapidly, whereas co-oxidation of Fe(II) and Mn(II) by MnO4 generated colloidally stable suspensions. The aggregation of all suspensions decreased in P and Si solutions, but Ca counteracted these oxyanion effects. The speciation of oxidized Fe and Mn in the absence of P and Si also depended on the oxidant, with O-2 producing Mn(III)-incorporated lepidocrocite (Mn/Fe = 0.01-0.02 mol/mol), HOCl producing Mn(III)-incorporated hydrous ferric oxide (HFO) (Mn/Fe = 0.08 mol/mol), and MnO4 producing poorly-ordered MnO2 and HFO (Mn/Fe > 0.5 mol/mol). In general, the presence of P and Si decreased the crystallinity of the Fe(III) phase and increased the Mn/Fe solids ratio, which was found by Mn K-edge XAS analysis to be due to an increase in surface-bound Mn(II). By contrast, Ca decreased the Mn/Fe solids ratio and decreased the fraction of Mn(II) associated with the solids, suggesting that Ca and Mn(II) compete for sorption sites. Based on these results, we discuss strategies to optimize the design (i.e. filter bed operation and chemical dosing) of water treatment plants that aim to remove Fe(II) and Mn(II) by co-oxidation.
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| 3. |
- Ahmad, Arslan, et al.
(författare)
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Environmental arsenic in a changing world
- 2019
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 8, s. 169-171
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Kimambo, Vivian, et al.
(författare)
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Fluoride occurrence in groundwater systems at global scale and status of defluoridation – State of the art
- 2019
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 9
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Forskningsöversikt (refereegranskat)abstract
- Occurrence of elevated concentrations of fluoride in the drinking water supply in many regions of the world has caused widespread dental and skeletal fluorosis. In this paper the studies available on the routes of fluoride exposure, regions with excess fluoride in water sources and various defluoridation techniques has been reviewed. It is evident from the literature survey that no single technique fits for diverse technical and socioeconomic situations and there is a pressing need to develop suitable defluoridation techniques for household and community level water supply system in order to prevent fluorosis.
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| 5. |
- Litter, Marta I., et al.
(författare)
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Arsenic in Argentina : Technologies for arsenic removal from groundwater sources, investment costs and waste management practices
- 2019
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Ingår i: Science of the Total Environment. - : ELSEVIER. - 0048-9697 .- 1879-1026. ; 690, s. 778-789
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Tidskriftsartikel (refereegranskat)abstract
- An overview about the presence of arsenic (As) in groundwaters of Argentina, made by a transdisciplinary group of experts is presented. In this second part, the conventional and emerging technologies for As removal, management of wastes, and the initial investment costs of the proposed technologies, with emphasis on developments of local groups are described. Successful examples of real application of conventional and emerging technologies for As removal in waters for human consumption, for medium, small and rural and periurban communities are reported. In the country, the two most applied technologies for arsenic removal at a real scale are reverse osmosis and coagulation-adsorption-filtration processes using iron or aluminum salts or polyelectrolytes as coagulants. A decision tree to evaluate the possible technologies to be applied, based on the population size, the quality of the water and its intended use, is presented, including preliminary and indicative investment costs. Finally, a section discussing the treatment and final disposal of the liquid, semiliquid and solid wastes, generated by the application of the most used technologies, is included. Conclusions and recommendations, especially for isolated rural and periurban regions, have been added.
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