[Partial Nitrification Fast Start-up and Stable Performance of 15℃ SBBR]

In this study, controlled C/N effects on fast start-up and stable performance of partial nitrification process at 15℃ in a Sequenced Batch Biofilm Reactor (SBBR) were investigated. The results showed that partial nitrification successfully fast initiated when C/N was 1.5 but failed when C/N was 0/3 during 60 cycles. Fluorescence in situ hybridization and confocal laser scanning microscope (FISH-CLSM) results showed that ammonia oxidizing bacteria (AOB) was found as the dominant bacteria population when C/N was 1.5. When C/N were 0/3, there were almost no existence of AOB and nitrite oxidative bacteria (NOB). Partial nitrification could be stably achieved without carbon source. However, the addition of an appropriate amount of carbon can effectively improve the nitrification performance, and it is better for the stable operation of partial nitrification. In this experiment, partial nitrification was successfully initiated at high dissolved oxygen (DO) (about 9 mg·L^-1) conditions. The average DO was maintained at about 6.5 mg·L^-1 during the stable operation, which successfully decoupled partial nitrification from low DO concentration. Excessive residual ammonium concentration in the reactors effectively repressed the growth of NOB and guaranteed the stable operation of partial nitrification. At 15℃, full nitritation was more suitable for sidestream wastewater, while mainstream wastewater was more suitable for partial nitritation.