Microcystis aeruginosa flour as carbon and nitrogen source for aerobic denitrification and algicidal effect of Raoultella sp. R11

•Effect of inoculum, initial pH, C/N ratio and temperature on aerobic denitrification. process was compared.•Microcystis aeruginosa flour as carbon and nitrogen source for aerobic denitrification.•Fourier transform near infrared was used to analyze mechanism of algae-lysing.

Harmful algal blooms (HABs) could be deemed hazardous materials in aquatic environments. In this study, we investigated aerobic denitrification and algicidal effects of the Raoultella sp. R11. Based on PCR amplification, the denitrification genes napA was detected. A response surface methodology (RSM) analysis demonstrated that the maximum nitrate removal ratio was 96.06%, and optimal conditions occurred for inoculum of 13.02% (v/v), initial pH of 6.65, C/N ratio of 7.59 and temperature of 27.08 °C based on a ridge analysis. When the Microcystis aeruginosa flour as carbon and nitrogen source for denitrification in aerobic conditions, the NO3−-N and TOC removal ratios were 72.36% and 85.56%, respectively. Additionly, the denitrification rate was 0.0123 mg L−1 h−1. Furthermore, the infrared spectrogram and SEM images showed the M. aeruginosa cell structure was destroyed, indicating that R11 could use algal death for denitrification. Therefore, Raoultella sp. R11 played a crucial role for simultaneous denitrification and algicidal effects in wastewater treatment.