Real-time PCR quantification of the population dynamics of ammonia-oxidizing bacteria in a pilot-scale wastewater treatment plant

To determine whether the stable nitrification was correlated with a stable AOB population size in a pilot-scale wastewater treatment plant (WWTP) and to relate the AOB population to the ammonia removal efficiency, the population dynamics of AOB in a pilot-scale WWTP was monitored over a half-year period using real-time PCR assay. During the study period, the effluent ammonia concentrations were below 2.5 mg/L almost all the time, indicting a stable function of nitrification. The change of AOB population was relatively stable, ranging from 0.7 × 1010 to 7.9 × 1010 cells per liter mixed liquor suspended solids (MLSS) mixture, indicating that the stable function of nitrification was correlated with a stable AOB number in the pilot-scale WWTP. Correlation analysis demonstrates a significantly positive correlation between ammonia removal efficiency and total AOB population number (r = 0.711, P < 0.01). The findings enrich the theory involving the relation between AOB population dynamics and function of nitrification in WWTPs.

► We monitored AOB number in a pilot-scale WWTP.
► Stable function of nitrification was correlated with a stable AOB number.
► Ammonia removal efficiency was positively correlated with AOB number.