Arsenic removal from iron-containing groundwater by delayed aeration in dual-media sand filters

Md Annaduzzaman; Luuk C Rietveld; Bilqis Amin Hoque; Md Niamul Bari; Doris van Halem

doi:10.1016/j.jhazmat.2020.124823

Arsenic removal from iron-containing groundwater by delayed aeration in dual-media sand filters

J Hazard Mater. 2021 Jun 5:411:124823. doi: 10.1016/j.jhazmat.2020.124823. Epub 2020 Dec 11.

Authors

Md Annaduzzaman¹, Luuk C Rietveld², Bilqis Amin Hoque³, Md Niamul Bari⁴, Doris van Halem²

Affiliations

¹ Sanitary Engineering Section, Department of Water Management, Delft University of Technology, The Netherlands. Electronic address: M.Annaduzzaman@tudelft.nl.
² Sanitary Engineering Section, Department of Water Management, Delft University of Technology, The Netherlands.
³ Environment and Population Research Center, Bangladesh.
⁴ Department of Civil Engineering, Rajshahi University of Engineering and Technology, Bangladesh.

PMID: 33858074
DOI: 10.1016/j.jhazmat.2020.124823

Abstract

Generally, abstracted groundwater is aerated, leading to iron (Fe²⁺) oxidation to Fe³⁺ and precipitation as Fe³⁺-(hydr)oxide (HFO) flocs. This practice of passive groundwater treatment, however, is not considered a barrier for arsenic (As), as removal efficiencies vary widely (15-95%), depending on Fe/As ratio. This study hypothesizes that full utilization of the adsorption capacity of groundwater native-Fe²⁺ based HFO flocs is hampered by rapid Fe²⁺ oxidation-precipitation during aeration before or after storage. Therefore, delaying Fe²⁺ oxidation by the introduction of an anoxic storage step before aeration-filtration was investigated for As(III) oxidation and removal in Rajshahi (Bangladesh) with natural groundwater containing 329(±0.05) µgAs/L. The results indicated that As(III) oxidation in the oxic storage was higher with complete and rapid Fe²⁺ oxidation (2±0.01 mg/L) than in the anoxic storage system, where Fe²⁺ oxidation was partial (1.03±0.32 mg/L), but the oxidized As(V)/Fe removal ratio was comparatively higher for the anoxic storage system. The low pH (6.9) and dissolved oxygen (DO) concentration (0.24 mg/L) in the anoxic storage limited the rapid oxidation of Fe²⁺ and facilitated more As(V) removal. The groundwater native-Fe²⁺ (2.33±0.03 mg/L) removed 61% of As in the oxic system (storage-aeration-filtration), whereas 92% As removal was achieved in the anoxic system.

Keywords: Anoxic storage; Arsenic removal; Drinking water treatment; Sand filtration.

Publication types

Research Support, Non-U.S. Gov't