Interaction effect of phenanthrene degradation on nitrogen transformation in heterotrophic nitrification and aerobic denitrification systems

The heterotrophic nitrification and aerobic denitrification (HNAD) system plays an important role in treatment of nitrogen pollution in water, and nitrogen transformation is closely related to carbon source. In this study, in order to explore the interaction between nitrogen conversion and phenanthrene degradation under the HNAD system, different concentrations of phenanthrene (0, 3, 6, 9 mg/L) were used as the typical and only carbon source of microorganisms, and different concentrations of ammonium nitrogen (0, 25, 50, 75 mg/L) and nitrate nitrogen (0, 25, 50, 75 mg/L) were used as nitrogen sources of microorganisms. The results showed that with the increase of phenanthrene concentration, the degradation rate of ammonia nitrogen gradually increased, which was higher than that of the control by 24.9%. With the increase of phenanthrene concentration, the inhibition effect was more obvious, and the denitrification effect was weakened. The addition of ammonia nitrogen and nitrate nitrogen accelerated the degradation of phenanthrene. As the increase of the concentration of ammonia nitrogen and nitrate nitrogen, the degradation rate of phenanthrene gradually increased. The degradation rate of phenanthrene can reach 100% and 98.8% when the concentration of ammonia nitrogen and nitrate nitrogen was the highest. This may be related to the fact that a large amount of inorganic nitrogen can promote the assimilation of microorganisms and accelerate the co-metabolism of phenanthrene degradation by microorganisms. In short, there was an obvious interaction effect between the degradation of organic carbon source and the conversion of nitrogen in the HNAD system.