Arsenic Removal from Bangladesh Tube Well Water with Filter Columns Containing Zerovalent Iron Filings and Sand

• Published in: Environmental science & technology Vol. 39; no. 20; pp. 8032 - 8037
• Main Authors: Leupin, Olivier X, Hug, Stephan J, Badruzzaman, A. B. M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-10-2005
• Subjects: Applied sciences; Arsenic - analysis; Arsenic removal; Bangladesh; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Fresh Water - chemistry; Groundwater; Iron; Iron - chemistry; Oxidation-Reduction; Pollution; Sand & gravel; Silicon Dioxide - chemistry; Water Purification - instrumentation; Water Purification - methods; Water treatment and pollution; Wells; X-Ray Diffraction; Bangladesh; Drinking water treatment; Filtration; Sand; Zerovalent metal; Iron; Arsenites; Water well; Reaction mechanism; Arsenic III; Oxidation; Water pollution; Performance; Ground water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es050205d

Arsenic removal is often challenging due to high As(III), phosphate, and silicate concentrations and low natural iron concentrations. Application of zerovalent iron is promising, as metallic iron is widely available. However, removal mechanisms remained unclear and currently used removal units with iron have not been tested systematically, partly due to their large size and long operation time. This study investigated smaller filter columns with 3−4 filters, each containing 2.5 g of iron filings and 100−150 g of sand. At a flow rate of 1 L/h, these columns were able to treat 75−90 L of well water with 440 μg/L As, 1.8 mg/L P, 4.7 mg/L Fe, 19 mg/L Si, and 6 mg/L dissolved organic carbon (DOC) to below 50 μg/L As(tot), without addition of an oxidant. As(III) was oxidized in parallel to oxidation of corrosion-released Fe(II) by dissolved oxygen and sorbed on the forming hydrous ferric oxides (HFO). The open filter columns prevented anoxic conditions. DOC did not appear to interfere with arsenic removal. Manganese was reduced after a slight initial increase from 0.3 mg/L to below 0.1 mg/L. About 100 mg of Fe(0)/L of water was required, 3−5 times less than that for larger units with sand and iron turnings.