Abstract:Nitrite accumulation was always observed in the saline wastewater nitrification process, but the effect of NaCl salinity on ammonia-oxidizing bacteria (AOB) activity and kinetic characterization has not been clear. In this study, AOB was enriched in a lab-scale SBR system with high concentration of ammonium wastewater, and the partial nitrification was successfully achieved. The fluorescence in situ hybridization (FISH) analysis showed that AOB accounted for (55 ± 7)% of total bacteria. The maximum specific ammonia oxidation rate was (0.92 ± 0.13)gN/(gVSS·d). The effect of NaCl salinity on AOB activity was investigated using this mixed culture. The kinetic parameters of AOB (KNH3、Ko) were also measured under NaCl salinity of 10g/L. Results showed that compared with NaCl salinity 0g/L, the activity of AOB decreased 37% under NaCl salinity of 15g/L and decreased 85% under NaCl salinity of 30g/L. When salinity was 10g/L, the maximum ammonia oxidation rate was (0.62 ± 0.03)gN(gVSS·d), the half-saturation constant for ammonia (KNH3) was (7.62±0.13)mg/L, the half-saturation constant for oxygen (Ko) was (0.39±0.04)mg/L. The KNH3 value was higher than recommended value of ASM2model. NaCl salinity could reduce maximum specific ammonia oxidation rate, and also affects the substrate (ammonia) affinity of AOB.