Carbon removal and nitrification by rotating biological contactors

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

“…This might be confirmed by the bio-film color changing from the redbrown to white-brown [1,4,[30][31][32]. Moreover, the organic loading of the system with SIW containing various HM concentrations at a HRT of 8 h was quite low at only 5.09 g BOD 5 /m 2 d and resulted in reducing the number of aerobic heterotrophic bacteria [1,4,7,20]. From the above results, it could be said that both aerobic heterotrophic bacteria and nitrogen removal bacteria (nitrifying and denitrifying bacteria) were repressed by high HM loadings and low organic loadings and then the facultative heterotrophic bacteria was dominated.…”

“…This was confirmed as the color of the bio-film became white-brown with the increase of HM loadings (physical observation of the bio-film during operation). According to the increasing facultative heterotrophic bacteria population, the organic removal efficiency decreased as a result of the low specific growth rate of acidogenic bacteria [1,4,20,21]. For the nitrogen removal efficiency observation, TN and TKN removal efficiencies decreased with the increase of HM loadings.…”

“…From the above results, it could be said that both aerobic heterotrophic bacteria and nitrogen removal bacteria (nitrifying and denitrifying bacteria) were repressed by high HM loadings and low organic loadings and then the facultative heterotrophic bacteria was dominated. The organic and nitrogen removal efficiencies of the system decreased due to the low specific growth rate of the facultative heterotrophic bacteria [1,2,4,18,20]. However, the number of aerobic heterotrophic bacteria could be increased by increasing the organic loadings.…”

“…The effluents NH 4 + and NO 3 À increased with the increased HM loadings. This could explain why the HM gave a greater repressive effect to the growth and activity of nitrogen removal bacteria (nitrifying and denitrifying bacteria) than that of the heterotrophic bacteria (aerobic and facultative heterotrophic bacteria) [2,5,20,22,35,36]. It could be suggested that the nitrogen compounds were mainly removed by the assimilation mechanism of heterotrophic bacteria due to the small population of nitrogen removal bacteria and the large population of heterotrophic bacteria [5,9,35].…”

“…Theoretically, the nitrogenous compounds of the wastewater were biologically removed by assimilation and oxidation-reduction mechanisms [4,5,19,20,[22][23][24]. According to the results above, HM might have a strong effect to both aerobic heterotrophic and nitrogen removal bacteria due to the decrease of TKN and TN removal efficiencies and the increase of effluents NH 4 + and NO 3 À [5,19,20,22,25]. However, their activities and growths would not be repressed by low HM loadings of less than 0.204 g/m 2 d. Then, to increase the efficiency of the system, HRT was investigated.…”