A strain of Acinetobacter sp. Y1, which exhibited an amazing ability to remove ammonium, nitrite and nitrate, was
isolated from the activated sludge of a coking wastewater treatment plant. The aim of this work was to study the ability,
influence factors and possible pathway of nitrogen removal by Acinetobacter sp. Y1. Results showed that maximum
removal rate of NH4
D-N by the strain was 10.28 mg-N/L/h. Carbon source had significant influence on the growth and
ammonium removal efficiencies of strain Y1. Pyruvate, citrate and acetate were favourable carbon sources for the strain.
Temperature, pH value and shaking speed could affect the growth and nitrogen removal ability. Nitrate or nitrite could
be used as a sole nitrogen source for the growth and removed efficiently by the strain. N2 levels increased to 53.74%,
50.21% and 55.13% within 36 h when 100 mg/L NH4
D-N, NO2
L-N or NO3
L -N was used as sole nitrogen source in the gas
detection experiment. The activities of hydroxylamine oxidoreductase (HAO), nitrate reductase (NR) and nitrite reductase
(NiR), which are key enzymes in heterotrophic nitrification and aerobic denitrification, were all detectable in the
strain. Consequently, a possible pathway for ammonium removal by the strain was also suggested.