Nitrogen and potassium variation on contaminant removal for a vertical subsurface flow lab scale constructed wetland

► Lab scale constructed wetlands were evaluated for organic load removal efficiency. ► Organic load remained constant while nitrogen and potassium loads were varied. ► N:K ratios of 0.5 and 0.775 yielded maximum biomass and higher efficiency. ► N:K ratios of 0.125 and 3.1 yielded less biomass and lower efficiency. ► Planted systems had higher redox gradients in depth columns.