Suitable Dissolved Oxygen(DO) for Startup and Steady Operation of SBR Partial Nitrification Process

In SBR process,rapid startup of partial nitrification was not only associated with the number of cycles needed for startup,but also with nitrification time(nitrification rate) of each cycle.When temperature was 21²3℃,the effect of dissolved oxygen(DO) on partial nitrification indicated that DO mass concentration of 0.25¹.25 mg/L was beneficial to startup of partial nitrification in which ρ(DO)of 0.25⁰.75 mg/L was superior for rapid startup.The effects of ρ(DO) of 0.25⁰.50 and 0.50⁰.75 mg/L on rapid startup of partial nitrification were fair,mainly because when ρ(DO) was 0.25⁰.50 mg/L,although competitive advantage of AOB was more significant,doubling time of AOB increased.During the operation of partial nitrification in which ρ(DO) was about 1.50¹.75 mg/L,long-term steady operation achieved by reducing ρ(DO) to 0.50⁰.75 mg/L at intervals.Molecular biology was used to analyze the sludge sample taken from steady operation period.Resultsof general primers analysis showed that the proportion of AOB and NOB in total bacteria was 22.50%and 3.75%respectively,especially,Nitrosomonas sp.was the dominant bacterial genus in AOB,and its proportion of the total bacteria was 17.50%.