Potential stimulation of nitrifying bacteria activities and genera by landfill leachate

With the increasing complexity of influent composition in wastewater treatment plants, the potential stimulating effects of refractory organic matter in wastewater on growth characteristics and genera conversion of nitrifying bacteria (ammonium-oxidizing bacteria [AOB] and nitrite-oxidizing bacteria [NOB]) need to be further investigated. In this study, domestic wastewater was co-treated with landfill leachate in the lab-scale reactor, and the competition and co-existence of NOB genera Nitrotoga and Nitrospira were observed. The results demonstrated that the addition of landfill leachate could induce the growth of Nitrotoga, whereas Nitrotoga populations remain less competitive in domestic wastewater operation. In addition, the refractory organic matter in the landfill leachate also would have a potential stimulating effect on the maximum specific growth rate of AOB genus Nitrosomonas (μ_{max, aob}). The μ_{max, aob} of Nitrosomonas in the control group was estimated to be 0.49 d^-1 by fitting the ASM model, and the μ_{max, aob} reached 0.66-0.71 d^-1 after injection of refractory organic matter in the landfill leachate, while the maximum specific growth rate of NOB (μ_{max, nob}) was always in the range of 1.05-1.13 d^-1. These findings have positive significance for the understanding of potential stimulation on nitrification processes and the stable operation of innovative wastewater treatment process.