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Publisher DOI: 10.3390/w14182903
Title: Chromium removal in the presence of NOM during Fe(II) reductive precipitation for drinking water treatment
Language: English
Authors: Langer, Margarethe 
Jamal, Mohammad Umair 
Conklin, Amanda 
Ernst, Mathias  
Issue Date: 16-Sep-2022
Publisher: Multidisciplinary Digital Publishing Institute
Source: Water 14 (18): 2903 (2022)
Abstract (english): 
Cr(VI) is toxic and carcinogenic, which fuels discussions on reducing existing standards for maximum Cr concentrations in drinking water. Fe(II) reductive precipitation is a common and economical method for achieving very low Cr(tot) concentrations (<5 µg/L). While Cr(VI) is reduced to Cr(III), Fe(II) is oxidized to Fe(III). The resulting Cr(III) and Fe(III) have low solubilities at neutral pH, precipitate as hydroxides, and can be removed by conventional media filtration. The presence of natural organic matter (NOM) in the raw water source can, depending on pH, concentration, type of NOM, and contact time, affect this process in various ways, from promoting Cr(VI) reduction, to re-reducing Fe(III), to forming stable complexes with Cr and Fe, thus, impairing chromium removal. The presented data showed that NOM, whether dominated by terrestrial humic acid, or of aquatic origin, could substantially impair chromium removal at neutral pH conditions. In particular, the ultimate removal of Cr(III) was affected. Soluble complexes and/or colloids of Cr(III), Fe(III) and NOM in the size range of 10 kDa–0.1 µm were formed, that could not be removed by conventional media filtration. Presence of iron sludge (>50 mg/L Fe(III)) mitigated the negative impacts of NOM on Cr(VI) reduction and Cr(III) removal. However, even 100 mg/L Fe(III), the highest applied sludge concentration, did not lead to a decrease in Fe(II) dosing requirements under the given conditions. A molar ratio higher than the given stochiometric ratio of [Fe(II)]:[Cr(VI)] = 3 was necessary for sufficient Cr(VI) removal.
DOI: 10.15480/882.4603
ISSN: 2073-4441
Journal: Water 
Other Identifiers: doi: 10.3390/w14182903
Institute: Wasserressourcen und Wasserversorgung B-11 
Document Type: Article
Project: Open-Access-Publikationskosten / 2022-2024 / Technische Universität Hamburg (TUHH) 
Entfernung von Cr(VI) aus Grundwasser durch chemische Reduktion, Koagulation und Membranfiltration 
Funded by: Deutsche Forschungsgemeinschaft (DFG) 
License: CC BY 4.0 (Attribution) CC BY 4.0 (Attribution)
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