Anoxic storage to promote arsenic removal with groundwater-native iron

Annaduzzaman, M and Rietveld, LC and Ghosh, D and Hoque, BA and van Halem, D (2021) Anoxic storage to promote arsenic removal with groundwater-native iron. In: Water Research, 202 .

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Abstract

Storage containers are usually used to provide a constant water head in decentralized, community groundwater treatment systems for the removal of iron (Fe) and arsenic (As). However, the commonly practiced aeration prior to storage assists in rapid and complete Fe2+ oxidation, resulting in poor As removal, despite sufficient native-Fe2+ in the source water. In this study, it was found that application of anoxic storage enhanced As removal from groundwater, containing �300 µg/L of As(III) and 2.33 mg/L of Fe2+ in an As affected village of Rajshahi district in Bangladesh. Although the oxidation of Fe2+ and As(III) during oxic storage was considerably faster, the As/Fe removal ratio was higher during anoxic storage (61�80±5 µgAs/mgFe) compared to the oxic storage (45±5 µgAs/mgFe). This higher As removal efficacy in anoxic storage containers could not be attributed to the speciation of As, since As(V) concentrations were higher during oxic storage due to more favorable abiotic (As(III) oxidation by O2 and Fenton-like intermediates) and biotic (As(III) oxidizing bacteria, e.g., Sideroxydans, Gallionella, Hydrogenophaga) conditions. The continuous, in-situ hydrous ferric oxide floc formation during flow-through operation, and the favorable lower pH aiding higher sorption capacities for the gradually formed As(V) likely contributed to the improved performance in the anoxic storage containers. © 2021

Item Type:	Journal Article
Publication:	Water Research
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Authors
Keywords:	Arsenic; Chemicals removal (water treatment); Containers; Iron; Iron oxides; Oxidation; Pollution control; Reaction intermediates, Anoxic; Arsenic removal; Arsenic(III); Decentralised; Groundwater treatment; Source waters; Storage container; Treatment; Treatment systems; Water heads, Groundwater, aeration; anoxia; anoxic conditions; arsenic; oxidation; sorption; storage tank; water treatment, Bangladesh; Rajshahi, Gallionella; Hydrogenophaga
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	25 Sep 2021 12:37
Last Modified:	25 Sep 2021 12:37
URI:	http://eprints.iisc.ac.in/id/eprint/69788

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