Fast start-up and enhancement of CANON process for the low-strength wastewater treatment: tactic and action of ultrasonic

In this study, the CANON (Completely Autotrophic Nitrogen-removal Over Nitrite) process was successfully started-up inoculate by anammox sludge which was under cold preservation for three-months, and the stable operation of CANON process for low-strength wastewater treatment were achieved through ultrasonic enhancement. In accordance with the optimal parameters determined in batch tests, which controlled (DO=0.3-1.5mg/L, HRT=4.0-12h and pH 7.5±0.3) three critical factors to repressed the NOB (Nitrite-Oxidizing Bacteria). The CANON process was started-up within 15 days. Subsequently, effect of ultrasonic was gradually added to the CANON system to investigate its impact. Results showed that, through ultrasonic (intensity of 0.3 w/cm2, act on time 4 min/d), the NH4 +-N and TN removal efficiency were 95% and 76.7% in the CANON process(~50 mg N.L-1), respectively. The 16S rRNA analysis showed that the abundance of dominanted phylum has remarkablely conversion after ultrasonic enhancement. The relative abundance of AOB were increased form 12.15% to 24.14%. Moreover, the NOB were decreased from 2.97% to 1.64%. The relative abundance of Candidatus brocadia and Candidatus Kuenenia were accounted for 27.07% and 11.52%, respectively. The Nitrosomonas was also enriched to 12.15% significantly. In general, a certain intensity of ultrasonic (intensity of 0.3 w/cm2, act on time 4 min/d) could provides an effective promotion for AOB and suppression for NOB. The results provide technical assistance for the starting-up and stably performance in the mainstream CANON system.