Moreover, there was no sequence identical (>97% similarity) with the inoculated PCN strains (Fig. 6), indicating the introduced PCN bacteria did not become dominant in the reactor. However, high aerobic nitrogen removal efficiency was obtained through bioaugmentation in this study. Similar results were present in the bioaugmentation studies on refractory organic matter degradation, which revealed that the inoculated strains were undetectable in the end and the removal of target pollutants was still in effect It could be speculated that the introduced PCN bacteria could synergize with other indigenous microorganisms to achieve good treatment results.