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Title: Laboratory comparison of four iron-based filter materials for water treatment of trace element contaminants

Author
item Allred, Barry
item TOST, BRIAN - The Ohio State University

Submitted to: Water Environment Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2013
Publication Date: 6/15/2014
Citation: Allred, B.J., Tost, B.C. 2014. Laboratory comparison of four iron-based filter materials for water treatment of trace element contaminants. Water Environment Research. 86(11):2221-2232.

Interpretive Summary: A laboratory study that included saturated falling-head hydraulic conductivity tests, contaminant removal batch tests, and low-to-high flow rate saturated solute transport column tests was conducted to evaluate the capabilities of four iron-based filter materials to remove trace element contaminants from waters containing either arsenic, chromium, and selenium (As-Cr-Se) or cadmium, copper, and lead (Cd-Cu-Pb). Sulfur modified iron (SMI) was found to completely remove As, Cd, Cr, Cu, Se, and Pb (at least below detection limits). An iron oxide/hydroxide (IOH) was especially effective in removing As, Cd, Cr, Cu, and Pb, but not Se. Potential advantages for using IOH compared to the other three iron-based filter materials include its very high hydraulic conductivity and the release of treated waters that are not extremely acidic or alkaline. The zero valent iron (ZVI) and porous iron composite (PIC) filter materials generally worked quite well removing Cd, Cr, Cu, and Pb. These results are preliminary, and more laboratory and field research is certainly needed to fully evaluate these four iron-based materials for filter treatment of waters contaminated with mixtures of trace elements.

Technical Abstract: A laboratory investigation was conducted to evaluate four iron-based filter materials for trace element contaminant water treatment. The iron-based filter materials evaluated were zero valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and iron oxide/hydroxide (IOH). Only filter material retained on a 100 mesh sieve (> 0.15 mm) was used for testing. Tested trace element contaminant solutions combined As, Cr, and Se (added as AsO43-, CrO42-, and SeO42-, respectively) or combined Cd2+, Cu2+, and Pb2+. The laboratory investigation included saturated falling-head hydraulic conductivity tests, contaminant removal batch tests, and low-to-high flow rate saturated solute transport column tests. Hydraulic conductivity test results indicate that all four iron-based filter materials have sufficient water flow capacity as indicated by saturated hydraulic conductivity values greater than 1 x 10-2 cm/s. Essentially 100% of each trace element contaminant (As, Cd, Cr, Cu, Pb, and Se) was removed by SMI during batch and column tests, while IOH exhibited good removal of each trace element except Se. The combined batch and column test results showed ZVI and PIC were most capable of treating Cd, Cr, Cu, and Pb. Consequently, ZVI, PIC, SMI, and IOH all have substantial potential for trace element contaminant water treatment.