Details

Autor(en) / Beteiligte

• Schwindaman, Jeffrey P.
• Castle, James W.
• Rodgers, John H.

Titel

Fate and distribution of arsenic in a process-designed pilot-scale constructed wetland treatment system

Ist Teil von

• Ecological engineering, 2014-07, Vol.68, p.251-259

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2014

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• •A pilot-scale wetland treatment system was constructed for arsenic removal.•Arsenic removal was greater in oxidizing wetland cells than in reducing cells.•Most of the arsenic removed from the aqueous phase was transferred to sediment.•The majority of sediment-bound arsenic was retained in the upper 6cm of sediment.•Wetland treatment decreased arsenic concentration in the water to below 10μgL−1. The fate and distribution of arsenic in simulated groundwater was determined in a pilot-scale constructed wetland treatment system (CWTS) designed to promote specific biogeochemical processes for arsenic removal. Two CWTS series were designed to promote co-precipitation and sorption of arsenic with iron oxyhydroxides under oxidizing conditions, and two series were designed to promote precipitation of arsenic with sulfide and co-precipitation of arsenic with iron sulfide under reducing conditions. Measured conditions in the CWTS were within ranges favorable for the targeted processes. Arsenic removal was significantly greater (α=0.05) in an oxidizing series amended with zero-valent iron (ZVI) than in the other series, with removal extents, efficiencies, and rate coefficients ranging from 6 to 79μgL−1, 40 to 95%, and 0.13 to 0.77d−1, respectively. The majority of inflow arsenic retained in the first reactor of each series partitioned to the sediment (88–99%), while the remainder partitioned to Typha latifolia. A greater percentage of inflow arsenic was retained in the sediment of the first reactor of the two oxidizing series (20 and 13%) than in the first reactor of the two reducing series (6 and 7%). Addition of ZVI enhanced arsenic removal from the aqueous phase in both oxidizing series and reducing series and increased the percentage of inflow arsenic partitioned to sediment. A vertical concentration gradient developed over time in the sediment, with 74–85% of sediment-bound arsenic accumulated in the upper 6cm and the remaining percentage below 6cm. Results from this study demonstrate that a CWTS can decrease the concentration of arsenic in simulated groundwater to below the World Health Organization (WHO) drinking water quality guideline of 10μgL−1 primarily by transferring arsenic from the aqueous phase to the sediment.