Ammonium reduction kinetics in drinking water by newly isolated Acinetobacter sp. HITLi 7 at low temperatures

The Acinetobacter sp. HITLi 7 was isolated from the Songhua River and shown to be capable of heterotrophic nitrification ability at 2 degrees C. To predict the ammonium reduction performance in drinking water at low temperature, the kinetics of strain HITLi 7 were investigated using Monod kinetic models. The results of calculations showed that the substrate half saturation constant K-s was 9.9mg/L of total ammonium, and the maximum specific rate mu(max) was 7.9 x 10(-4)h(-1) at 8 degrees C, C/N 2, pH 6.0 while shaking at 100r/min. The effects of temperature (2, 5 and 8 degrees C), C/N (2, 4, and 10), and pH (6.0, 7.0, and 7.5) on kinetic parameters were also evaluated. K-s and mu(max) increased consistently with an increase in temperature and decreased as C/N ratio increased. The specific affinity a(0) (a(0 )= mu(max)/K-s) for ammonium was the highest for a C/N of 10. This value was 2.1-fold higher than the affinity observed for a C/N of 2. The results demonstrated that the affinity of HITLi 7 for ammonium was higher when a sufficient carbon source was present. The maximum ammonium reduction rate was 0.18mg [GRAPHICS] -N/L/h at a C/N of 10. These results suggest that HITLi 7 may be used for ammonium removal in drinking water at low temperatures.