Removal of Mercury from Wastewater Using a Constructed Wetland

Abstract

Removal of mercury from municipal wastewater using a constructed wetland was studied. Wastewater, wetland plant, and sediment samples were analyzed using an advanced mercury analyzer AMA-254. Average concentrations of total mercury in inflow and outflow water were 0.157 and 0.057 µg L−1, respectively. Significant fraction of mercury (38.2 %) was removed from wastewater during pretreatment. Mercury concentrations in vegetation (Phragmites australis) varied in the range of 0.0099−0.0105 and 0.0079−0.0086 mg kg−1 for the above and belowground biomass, respectively. Total mercury concentrations in the constructed wetland sediments were 0.151 and 0.103 mg kg−1 at distances 1 and 10 m from the inflow zone. Mercury can be precipitated and deposited at the initial part of the wetland bed and thus removed from wastewater. The formation of volatile mercury species is another mechanism of its removal. On the other hand, assimilation of Hg in wetland plants does apparently not contribute to mercury removal from wastewater.