Start-up and microbial communities of a simultaneous nitrogen removal system for high salinity and high nitrogen organic wastewater via heterotrophic nitrification

In this study, a simultaneous nitrogen removal system for high salinity and high nitrogen organic wastewater was developed in a pressurized biofilm reactor. The result showed that under the air supply rate of 200 L h−1, salinity of 3.0 ± 0.2%, organic load of 10 kg COD m−3 d−1 and nitrogen loading of 0.185 kg m−3 d−1, the reactor started up rapidly and performed stably after 30 days operation. Meanwhile, a simultaneous COD and nitrogen removal was achieved in the single-stage reactor, with COD, NH4+-N and TN removal efficiency of 97%, 99% and 98%, respectively. Denaturing gradient gel electrophoresis profile demonstrated that simultaneous nitrogen removal could be achieved through heterotrophic nitrification-aerobic denitrification, and the pivotal microorganisms were Flavobacterium phragmitis and Paracoccus denitrificans. The microbial community of salt-tolerant halophilic microorganisms was developed successfully. This study can provide a more efficient and feasible solution to treat high salinity organic wastewater.