Evaluation of simultaneous nitrification and denitrification under controlled conditions by an aerobic denitrifier culture.

Paracoccus versutus LYM was characterized with the ability of simultaneous nitrification and denitrification (SND) in presence of NH4(+)-N and NO3(-)-N (140mg/L-N each). However, there was approximate 95.80mg/L NO2(-)-N left during SND process. Fe(2+) was added in the SND medium and it benefited bacterial growth and further converted NO2(-)-N a little. Besides, remaining NO2(-)-N could be completely reduced by adding carbon donors in presence of NH4(+)-N and NO3(-)-N, whose converting efficiencies also reached 97.09% and 96.34%, respectively. And N2 stayed as the main product of SND process. While NO2(-)-N and NH4(+)-N were present simultaneously, strain LYM could also remove nitrogen compounds thoroughly with sufficient carbon source. But there was no NO2(-)-N reduced as sole nitrogen source in the medium even if C/N ratio reached as high as 30.