The authors investigated the bioaugmentation performances of a selected bacterial strain for denitrification in a packed bed bioreactor using PBS as solid carbon source. Fluorescence quantitative PCR was employed to analyze the microbial community composition in the bioreactor. Results indicated that the denitrifier named W14 could remarkably improve denitrification efficiency. At HRT of 0.5 h, nitrogen removal was found to be higher than 90% and the residual DOC of effluent was greatly reduced. Addition of selected denitrifiers led to an increase of nirS gene abundance and proportion, indicating that inoculation of selected bacterial strain could boost denitrifiers’ proliferation and enhance nitrogen removal eventually.