Treatment of gully pot effluent containing nickel and copper with constructed wetlands in a cold climate

The aim of this study was to assess the treatment efficiencies for gully pot effluent of experimental vertical-flow constructed wetland niters containing macrophytes and granular media of different adsorption capacities in a cold climate. For approximately 6 months, nickel nitrate and copper nitrate were added to sieved gully pot effluent in order to simulate contaminated primary treated stormwater runoff. The inflow concentrations for nickel, copper and nitrate were approximately 1.0, 1.0 and 3.7 mg dm^-3, respectively. For those filters receiving metals, an obvious breakthrough of nickel was recorded after road gritting (containing salt). Reductions of nickel, copper, biochemical oxygen demand and suspended solids were frequently insufficient compared with international secondary wastewater treatment standards (eg suspended solids <30 mg dm^-3). A further treatment step should be considered. Outflow conductivity and nickel concentrations were high due to the effect of road salting. Microbial activity was likely to be responsible for the overall filtration performance.