Isolation, Identification and Nitrogen Removal Performance of a Halotolerant Heterotrophic Nitrification-aerobic Denitrification Bacteria Rhodococcus sp. LS-2

High concentration of nitrogen in saline wastewater is usually treated by biological method. However, the high salinity stress can inhibit the nitrogen removal performance of freshwater bacteria. In contrast, marine microorganisms exhibit a higher tolerance to salinity and can effectively remove nitrogen in the saline wastewater. In this study, a novel strain LS-2 was isolated from the marine sediment. The bacterium was identified as Rhodococcus sp. by 16S rRNA gene sequencing and physiological tests. Moreover, the maximum tolerated salt concentration of bacterium and the effects of different environmental factors on the nitrogen removal were investigated by series of single factor experiment. The results show that the salt tolerance of this strain is 6%, and the optimal conditions for nitrogen removal include salinity of 4%, C/N ratio of 15, initial ammonia nitrogen concentration of 120 mg/L, pH 7, 30°C and 140 r/min. The removal efficiency of ammonia nitrogen is up to 95.5% without the accumulation of nitrite and nitrate nitrogen in the process. This study demonstrates that Rhodococcus sp. LS-2 displays excellent nitrogen removal performance, highlighting the potential application of this bacterial consortium in nitrogen elimination for the sanity wastewater.