Simultaneous heterotrophic nitrification and aerobic denitrification by bacterium Rhodococcus sp. CPZ24

Rhodococcus sp. CPZ24 was isolated from swine wastewater and identified. Batch (0.25 L flask) experiments of nitrogen removal under aerobic growth conditions showed complete removal of 50 mg L−1 ammonium nitrogen within 20 h, while nitrate nitrogen removal reached 67%. A bioreactor (50 L) was used to further assess the heterotrophic nitrification and aerobic denitrification abilities of Rhodococcus sp. CPZ24. The results showed that 85% of the ammonium nitrogen (100 mg L−1) was transformed to nitrification products ( NO 3 - -N and NO 2 - -N) (13%), intracellular nitrogen (24%), and gaseous denitrification products (48%) within 25 h. The ammonium nitrogen removal rate was 3.4 mg L−1 h−1. The results indicate that the strain CPZ24 carries out simultaneous nitrification and denitrification, demonstrating a potential use of the strain for wastewater treatment.