| 11. |
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| 12. |
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| 13. |
- Abarca, R. R. M., et al.
(författare)
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Metals toxic pollutants in the environment : Anthropogenic and geological causes and remediation
- 2019
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Ingår i: Current Trends and Future Developments on (Bio-) Membranes: Membranes in Environmental Applications. - : Elsevier Inc.. ; , s. 109-124
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Heavy metals are naturally present in nature, but if their concentration is higher than the normal accepted threshold levels, they constitute one of the pollutants that is more difficult to remove and also to rehabilitate the contaminated site by them. There are many heavy-metal pollutants-the most common among them are arsenic (As), chromium (Cr), lead (Pb), mercury (Hg), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), and zinc (Zn), along with the less common ones, which produced, for example, by the nuclear process, such as uranium (U)-in different configuration; hence, many possibilities of contamination in the world exist, and they are more difficult to remove.Thus heavy-metal pollution is more and more becoming one of the principal issues of the global interest, because it is common to both industrialized countries and developing countries. These issues are getting hard to be recognized and cannot be followed the simple rules concerning safety and environmental protection, thus fall into the same errors of the already industrialized countries. At the same time, new environment-remediation techniques are developed in the last decade, especially, in these last years. Some of these technologies concern physical or chemical process or effects, such as ion exchanges, flotations, and photocatalysis, while other technologies concern the use of membrane process, especially ultrafiltration or membrane integrated process or hybrid systems, where membranes are generally submerged and used together with another process.In this chapter a review of this problem and some example of technologies for removing and remediation of the environment are reported.
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| 14. |
- Abiye, T. A., et al.
(författare)
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Arsenic concentration in groundwater : Archetypal study from South Africa
- 2019
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- South Africa does not have significant surface water resources, which is often easily affected by unpredictable and rapidly changing climatic variables, due to its location in the arid and semi-arid climatic setting. In large part of the country, groundwater from weathered and fractured crystalline rocks plays pivotal role in sustaining the livelihood, often it contains toxic metals released from the host rocks. The host rocks that are responsible for arsenic release in groundwater are primarily enriched due to metamorphism and igneous processes that resulted in the enrichment of economic minerals. Preliminary assessment indicates that the main arsenic containing minerals are arsenopyrite (FeAsS), arsenical oxide, sulpharsenide, arsenopyritical reefs, leucopyrite, löllingite (FeAs2) and scorodite (FeAsO4·2H2O). Owing to the release of arsenic from highly mineralized rocks that constitute the aquifers, arsenic concentration in the groundwater reaches up to 253 μg/L (Namaqualand), 6150 μg/L (west of Johannesburg), about 500 μg/L in the Karoo aquifers, considerably higher than the WHO guideline value of 10 μg/L. Acid mine drainage from coal and gold mining is also found to be an important source of arsenic and other toxic metals in groundwater.
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| 15. |
- Abu-Khader, M. M., et al.
(författare)
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Radon in the groundwater in the Amman-Zarqa Basin and related environments in Jordan
- 2018
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 7, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of radon (222Rn) in environment (groundwater and indoor air) from geogenic sources is receiving an growing attention due to its adverse impact on human health worldwide including Jordan. Highlighting the current status of radon in Jordan, the present study of radon concentrations in ground waters in the Amman-Zarqa basin (AZB) was investigated. Groundwater samples were collected from fifteen wells located in three main areas of Ras Al-Ain, Al-Rsaifeh and Al-Hashemite. Radon concentration was measure using Liquid scintillation counting (LSC) Tri- Carb 3110 with discriminator and the highest values for radon concentration in water were observed in Al-Rsaifeh area and ranged from 4.52 up to 30.70 Bq/l with an average of 11.22 Bq/l, which were attributed to the decay of naturally distributed uranium in phosphate rock from Al-Rsaifeh mines. In Ras Al-Ain area, the radon concentration were noted ranged from 0.6 to 5.55 Bq/l with an average of 2.82 Bq/l, and also in Al-Hashemite area were ranged from 0.77 to 5.37 Bq/l with an average of 4.04 Bq/l. The overall average concentration of tested samples was 5.77 Bq/l and found within the acceptable international levels. Ground water samples of Ras Al-Ain area showed good quality as was tested of low salinity. It recorded the lowest average radon concentration of 2.82 Bq/l. Also, Radon indoor and building materials was reviewed. In conclusion, this study presented an urged need for developing national regulations and standards as well as awareness program concerning the radon status in Jordan.Elsevier B.V.
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| 16. |
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| 17. |
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| 18. |
- Ahmad, Arslan, et al.
(författare)
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Arsenic reduction to < 1 mu g/L in Dutch drinking water
- 2020
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 134
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Forskningsöversikt (refereegranskat)abstract
- Arsenic (As) is a highly toxic element which naturally occurs in drinking water. In spite of substantial evidence on the association between many illnesses and chronic consumption of As, there is still a considerable uncertainty about the health risks due to low As concentrations in drinking water. In the Netherlands, drinking water companies aim to supply water with As concentration of < 1 mu g/L - a water quality goal which is tenfold more stringent than the current WHO guideline. This paper provides (i) an account on the assessed lung cancer risk for the Dutch population due to pertinent low-level As in drinking water and cost-comparison between health care provision and As removal from water, (ii) an overview of As occurrence and mobility in drinking water sources and water treatment systems in the Netherlands and (iii) insights into As removal methods that have been employed or under investigation to achieve As reduction to < 1 mu g/L at Dutch water treatment plants. Lowering of the average As concentration to < 1 mu g/L in the Netherlands is shown to result in an annual benefit of 7.2-14 M(sic). This study has a global significance for setting drinking water As limits and provision of safe drinking water.
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| 19. |
- Ahmad, Arslan, et al.
(författare)
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Arsenite removal in groundwater treatment plants by sequential Permanganate-Ferric treatment
- 2018
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Ingår i: Journal of Water Process Engineering. - : ELSEVIER SCIENCE BV. - 2214-7144. ; 26, s. 221-229
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Tidskriftsartikel (refereegranskat)abstract
- The Dutch drinking water sector is actively investigating methods to reduce arsenic (As) to < 1 mu g/L in drinking water supply. We investigated (1) the effectiveness of sequential permanganate (MnO4-)-ferric (Fe(III)) dosing during aeration-rapid sand filtration to achieve < 1 mu g/L As (2) the influence of MnO4--Fe(III) dosing on preestablished removal patterns of As(III), Fe(II), Mn(II) and NH4+ in rapid sand filters and (3) the influence of MnO4--Fe(III) dosing on the settling and molecular-scale structural properties of the filter backwash solids. We report that MnO4--Fe(III) dosing is an effective technique to improve arsenite [As(III)] removal at groundwater treatment plants. At a typical aeration-rapid sand filtration facility in the Netherlands effluent As concentrations of < 1 mu g/L were achieved with 1.2 mg/L MnO4--and 1.8 mg/L Fe(III). The optimized combination of MnO4-and Fe(III) doses did not affect the removal efficiency of Fe(II), Mn(II) and NH4+ in rapid sand filters, however, the removal patterns of Fe(II) and Mn(II) in rapid sand filter were altered, as well as the settling behaviour of backwash solids. The characterization of backwash solids by Fe K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) showed that the changed settling velocity of backwash solids with MnO4-Fe(III) in place was not due to changes in the molecular-scale structure of Fe-precipitates that constitute the major portion of the backwash solids.
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| 20. |
- 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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