A novel Pseudomonas aeruginosa strain performs simultaneous heterotrophic nitrification-aerobic denitrification and aerobic phosphate removal

Nitrogen and phosphate removal from wastewater relies on different functional bacteria. In this study, a novel strain affiliated with Pseudomonas aeruginosa was isolated from activated sludge by gradient dilution and performed heterotrophic nitrification-aerobic denitrification and aerobic phosphate removal (HNADPR). The strain showed an ammonium removal efficiency of 87% and a phosphate removal efficiency of 97% under optimal conditions, such as C/N ratio of 10, P/N ratio of 0.1, temperature of 30°C, and pH of 7.5-8.5. The modified Gompertz model could fit well the heterotrophic ammonium nitrification, aerobic nitrite/nitrate denitrification, and aerobic phosphate removal processes. Functional gene amplification indicated that ammonium removal followed the complete HN-AD pathway (NH4+ → NH2OH → NO2- → NO3- → NO2- → NO → N2O → N2). Phosphate removal only occurred under aerobic conditions and ceased under anaerobic conditions. In successive aerobic cycles, the strain persistently took up phosphate. In wastewater, phosphate was aerobically converted into cell membrane, intracellular and extracellular polymeric substrates (EPS). Phosphorus in the form of phosphate monoester was pooled in EPS. A hypothetic aerobic phosphate removal model for strain SNDPR-01 is proposed to improve our understanding of the novel bacterial function of HNADPR.