Effect of Ni2+ and Pb2+ on the efficiency of packed cage rotating biological contactor system

The research aimed to study the effects of Ni2+ and Pb2+ on the efficiencies of the packed cage rotating biological contractor (packed cage-RBC) system with synthetic industrial wastewater (SIW) containing various concentrations of Ni2+ or Pb2+ (SIW-Ni2+ or SIW-Pb2+) of 10, 20, 30, 40, 50 mg/L at various hydraulic retention times (HRT) of 4, 6 and 8 h. The results showed that the system efficiencies decreased with the increase of heavy metal (HM) concentrations or loadings. However, Ni2+ and Pb2+ concentrations of up to 10 mg/L did not affect the system efficiencies. The COD, BOD5, TKN and Ni2+ or Pb2+ removal efficiencies of 89 ± 1% and 93 ± 0%, 87 ± 1% and 87 ± 1%, 80.2 ± 0.3% and 80.0 ± 0.8% and 85.7 ± 0.7% or 89.8 ± 1.5%, respectively, were obtained with SIW-10Ni2+ and SIW-10Pb2+, respectively, at a HRT of 8 h. According to the increase of HM, the numbers of aerobic heterotrophic, nitrifying and denitrifying bacteria decreased while facultative heterotrophic bacteria dominated. Moreover, Ni2+ gave a greater repression effect than Pb2+ on the growth and activity of bio-film.