During wastewater treatment using a traditional biological denitrification process, the excessive concentration of nitrate nitrogen (NO3--N) in the effluent is the primary cause of excessive total nitrogen (TN) generation. By using an external carbon source to increase the carbon to nitrogen ratio (C/N), the denitrification process can be strengthened, which effectively addresses this problem. Using an integrated denitrification reactor developed based on the two-stage denitrification process principle with the addition of polybutylene succinate (PBS) in the second stage, the denitrification process was analyzed using a scanning electron microscope before and after characterization of PBS materials. Moreover, amplicon sequencing was used for in-depth exploration of changes in the microbial community structure in the second denitrification pool before and after the addition of PBS. The data of a continuous 120-day experiment showed that the COD removal rate dropped from 95.7% to 90.8%, the TN removal rate increased from 51.8% to 80%, the relative abundance of Proteobacteria phylum rose from 36.1% to 46.1%, and the relative abundance of Thermomonas rose from 6.47% to 13.48%. The results show that after the addition of PBS, PBS can not only provide carbon source for denitrification, but its surface can also serve as a carrier for microbial growth and attachment, play a good role in filming, and increase the abundance of denitrifying bacteria and strengthen denitrification. During the nitrification process, denitrification performance was significantly enhanced, effectively improving the TN removal rate of the system.
Keywords: C/N; denitrification; microbial community; solid slow-release carbon source; two-stage denitrification.