In-situ formation of continuous-flow aerobic granular  sludge enhanced by calcium salt sludge-based induced  nuclei at low temperature
In this study, an A/O continuous flow reactor was started and operated at a lowtemperature in a wastewater treatment plant in Changchun City. It was found that theformation of small brown particles with a size of 0.21 mm was observed after only 15 d of operation in the reactor (R1) with calcium-salt sludge-based induced nuclei.By 150 d of operation, the particle diameter increased to 1.30 mm, with the percentage of granular sludge with particle size greater than 0.20 mm reaching 33.20% and SVI30 reaching 23.99 mL/g.Meanwhile, the calcium-salt sludge-based induced nuclei promoted the secretion of PN in the sludge to 62.39 mg/g VSS, which was about 1.22 times higher than that in the control group. For the removal of characteristic pollutants, the removal of carbon, nitrogen, and phosphorus pollutants by AO-particles was improved by 6.69%, 8.12%, and 5.36%, respectively, compared with the control group, although it was affected by the double effect of the low temperature and the fluctuation of the influent water.In addition, macro gene sequencing IV results showed that the low-temperature key bacterial genera such as Candidatus Microthrix, Dechloromonas, Acidovorax and Flavobacterium were enriched in the AO-particles, which promoted the secretion of EPS, the denitrification performance of the AO-particles, and strengthened the low-temperature formation of the continuous-flow granular sludge.