[Start-up and Performance Recovery of Granular Sludge for Phosphorus Removal and Nitrification]

In this experiment, to determine the characteristics of low carbon and nitrogen water quality in domestic sewage, a sequencing batch reactor (SBR) was used to realize the stable operation of dephosphorization-nitrosation, by inoculating the enhanced biological phosphorus removal granular sludge, which was stored at low temperature. The sludge was activated by control of the aeration intensity and sludge age, which provided water for the influent of a CANON or anaerobic ammonia oxidation (ANAMMOX) process. In the experiment, when the concentration of dissolved oxygen was 6.5 mg·L^-1 and the sludge age was 30 days, the effluent TP was less than 0.5 mg·L^-1, the concentration of COD was less than 50 mg·L^-1, and the accumulation rate of nitrite nitrogen was above 90%. It was also found that the performance of phosphorus removal can be improved by reducing the aeration intensity and reducing the age of sludge when the performance was damaged by excessive aeration strength. Aging the sludge for 40 days could restore nitrification during the process of phosphorus removal and nitrification. The final concentration of phosphorus was kept below 0.5 mg·L^-1, and the removal rate of COD and TP was stable at 80% and 95%, respectively, the accumulation rate of nitrite remained above 90%, and the SVI value decreased from the initial 63 mL·g^-1 to 35 mL·g^-1. The settling performance of the granular sludge was good, and the particle size was kept above 1000 μm.