Ammonium removal characteristics of an acid-resistant bacterium Acinetobacter sp. JR1 from pharmaceutical wastewater capable of heterotrophic nitrification-aerobic denitrification.

•A newly acid-resistant strain JR1 was isolated from pharmaceutical wastewater.•A high nitrogen removal could be achieved by JR1 under the acidic condition.•Nitrate began to be utilized as substitute N-source after exhausting of ammonium.•Ammonium was utilized through assimilation along with heterotrophic nitrification.