Metal Removal from Water Discharges by a Constructed Treatment Wetland

Abstract

A full‐scale constructed wetland treatment system consisting of four pairs of wetland cells (3.2 ha total area) with water flowing through a pair of cells in series prior to discharge was investigated. A retention basin provided stable water flow to the system. Water retention time in the wetland system was approximately 48 hours, and the wetland cells operated at circumneutral pH. Vegetation development within the cells has been excellent. Copper removal efficiency was greater than 75 % from the start‐up of the system, while mercury efficiency improved with maturation of the treatment cells. Sampling of the water course through the wetlands conducted during the fourth year of operation validated continued performance, and assessed the fate of a larger suite of metals present in the water. Copper and mercury removal efficiencies were still very high, both in excess of 80 % removal from the water after passage through the wetland system. Mercury removal continued along the entire water course through the system, while copper was removed almost immediately upon entering the wetland cells. Lead removal from the water by the system was 83 %, zinc removal was 60 %, and nickel was generally unaffected. Organic carbon in the water was also increased by the system and reduced the bioavailability of some metals. Operation and maintenance of the system continued to be minimal, and mainly consisted of checking for growth of the vegetation and free flow of the water through the system. The system was entirely passive, relying on gravity as the power source of water flow. No reportable permit exceedances have been experienced since the wetland began treating an outfall discharge.

Metal and metalloid sequestration in a constructed wetland system for treatment of landfill leachate during 2003-2012

“…The studies published earlier, show similar results with large iron reduction in constructed wetlands for LL treatment [12], [20]- [22]. While manganese is an essential element for plants vital functioning, in high concentrations it may Linnaeus ECO-TECH` 14 Kalmar, Sweden, November [24][25][26]2014 be toxic to some organisms. Previous studies have stated that manganese has low removal rate as it goes through CW and [15], [23], [24] mention 54% as average reduction rate in FWS wetlands.…”

“…Linnaeus ECO-TECH` 14 Kalmar, Sweden, November [24][25][26]2014 and contained unlikely values for such elements like Al, As, Ba, Cu, Fe and Zn. The second case was sampled in October 2011 and had extremely high values for Al, As, Fe and Pb.…”

“…Linnaeus ECO-TECH` 14 Kalmar, Sweden, November [24][25][26]2014 The overall trend analysis has shown that the concentrations in the outlet maintain at the same level disregarding the variations in the inlet. Even though the heavy metals and metalloids are not the major environmental concern in the landfill leachate [1] and the Atleverket wetland was not specially designed for removal those pollutants it is interesting to notice that wetland sequestrates these elements to a great extent.…”

“…While manganese is an essential element for plants vital functioning, in high concentrations it may Linnaeus ECO-TECH` 14 Kalmar, Sweden, November [24][25][26]2014 be toxic to some organisms. Previous studies have stated that manganese has low removal rate as it goes through CW and [15], [23], [24] mention 54% as average reduction rate in FWS wetlands. However, in this study Mn was retained to a large extent equal to 88%.…”

Comparison of pollutant emission control strategies for cadmium and mercury in urban water systems using substance flow analysis

“…In addition, by installing BMPs such as infiltration basins, constructed wetlands and porous paving, which have been shown to be efficient at removing metals (Revitt et al, 2008), the removal efficiencies can be increased to 70% for Cd (Visesmanee et. al., 2008) and 90% for Hg (Nelson et. al., 2006).…”