[Realization of short cut nitrification under the limited filamentous sludge bulking condition]

In order to realize the combination of "low oxygen limited filamentous sludge bulking" and short cut nitrification,the startup method of short cut nitrification and the maintenance strategies of sludge settleability were investigated under limited filamentous sludge bulking condition by using sequencing batch reactor (SBR). The effects of environmental factors like water quality, pH, DO,temperature and operation methods like mixture flow pattern, aeration mode, influent pattern on sludge settleability were analyzed. The results show that, when pH is between 7.2 and 8.0 and temperature is between 20 degrees C and 25 degrees C, short cut nitrification can be gradually realized through maintaining low DO and controlling the aeration time accurately. Nitrite accumulating ratio can increase from 28% to 80% after operating 160 cycles. Sludge settleability can be maintained effectively by changing the influent volume exchanging ratio (VER) assisted by aeration rate .The sludge volume index (SVI) can be maintained around 150 mL/g by adjusting the VER from 0.25 to 0.33 under limited sludge bulking. At the end of the aerobic phase, dissolved total nitrogen concentration increase slightly.