[Effects of Intermittent Starvation on the Operation of the SNAD Process].

ABSTRACT

We report on and discuss the effects of intermittent starvation on the operation of the simultaneous partial nitrification, ANAMMOX, and denitrification (SNAD) process. The SNAD process was carried out in a sequencing batch reactor (SBR) at room temperature (22℃±3℃), and the intermittent starvation was achieved by periodically extending the hydraulic retention time (HRT) of the system. The results showed that after the operation of intermittent starvation, the NO3--N concentration at the end of the aerobic phase decreased to 8.72 mg·L-1 and the NO2- accumulation percentage reached 83.18%, which indicated that the nitrite oxidizing bacteria (NOB) activity was effectively inhibited and that the nitritation performance improved. After the operation of the intermittent starvation, the ratio of NO2- to NH4+-N at the end of the aerobic phase was adjusted to provide more suitable substrates for the subsequent ANAMMOX process, such that the concentration of NH4+-N in the effluent fell below 1.0 mg·L-1. At the same time, due to the decrease of the NO3- concentration, the total N removal rate reached 92.07%, which indicated that the treatment performance improved. By determining the activity of the functional bacteria, we found that the main reason for the improvement in the nitritation performance after starvation was that the decay rate of the ammonia oxidizing bacteria (AOB) activity during the starvation period was lower than of the decay rate of the NOB activity, and that the recovery rate of the AOB activity during the recovery period was significantly higher than that of the NOB.