Anoxic storage to promote arsenic removal with groundwater-native iron

Md Annaduzzaman*, Luuk C. Rietveld, Devanita Ghosh, Bilqis A. Hoque, Doris van Halem

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
16 Downloads (Pure)

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.

Original languageEnglish
Article number117404
Number of pages10
JournalWater Research
Volume202
DOIs
Publication statusPublished - 2021

Keywords

  • Anoxic
  • Arsenic
  • Groundwater
  • Iron
  • Storage container
  • Treatment

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