Role of Equalization Basins of Constructed Wetland Systems for Treatment of Particulate-Associated Elements in Flue Gas Desulfurization Waters

Abstract

Pilot-scale experiments were performed to investigate the role of equalization basins used with constructed wetland systems for treatment of flue gas desulfurization (FGD) waters. Analysis of FGD water samples indicated that aqueous concentrations of Hg, As, and Se remained constant or changed very slightly in a pilot-scale equalization basin during a 24-h hydraulic retention time (HRT). No change in toxicity of FGD water occurred after one HRT. FGD particles were predominantly silt size, and approximately 99% of particles suspended in FGD water settled to the bottom of a 2.5-m-deep equalization basin during the first 4 h of the 24-h HRT. Approximately 90% of the total As, and smaller percentages of Hg and Se, in FGD water and particles were removed by particle settling in the equalization basin. Results of this investigation lend support to the use of equalization basins for treating FGD waters in constructed wetland treatment systems.