Abstract: “The present study aims in investigating simultaneous heterotrophic nitrification and aerobic denitrification (SND) ability of a newly isolated bacterium. The bacterial strain GS5 was isolated from a laboratory scale denitrifying bioreactor and characterized. Based on phenotypic and phylogenetic characteristics as derived from partial 16S rRNA gene sequence, the isolate was identified to be Bacillus cereus GS5 strain (Gen Bank accession no. KM212993). The strain had exhibited the capability of utilizing ammonia, nitrate and nitrite as sole nitrogen sources in presence of external carbon sources, thus heterotrophic in nature. Considering, initial concentration of ammonium as 50 mg/L, 92.02% was removed after 24h incubation with little accumulation of the intermediates such as hydroxylamine, nitrite, and nitrate. Similarly, the new isolate had a high denitrifying ability, from initial 100 mg/L nitrate, 98.26% was removed in a 24h period under aerobic conditions, with reduced level of nitr”

Keywords: Bacillus cereus GS5 strain, Heterotrophic nitrification, Aerobic denitrification, Simultaneous nitrification and denitrification (SND)