Individual and combined effects of nickel and copper on nitrification organisms

Abstract Individual and combined effects of Ni 2+ and Cu 2+ concentrations on the nitrification process were investigated in a submerged biofilter. The activity of nitrification organisms was inhibited by high concentrations of Cu 2+ . However, low concentrations of Cu 2+ promoted NOB activity. There were no observable stimulation effects of Ni 2+ . The presence of 0.2–4.0 mg/L Ni 2+ caused a decrease in the rate of nitrification. Although the inhibition of Cu 2+ on the nitrification organisms started at a concentration of 0.5 mg/L, it started at 0.2 mg/L for Ni 2+ . Ni 2+ had stronger inhibitory effect on the nitrification organisms than Cu 2+ . Using a mixture of Ni 2+ and Cu 2+ , inhibition level drastically increased to 32% and 49% at concentrations of 2.0 and 3.0 mg/L, respectively. At the same concentrations, individual inhibition by Ni 2+ and Cu 2+ was much lower, about 12–15% and 18–24%, respectively.