Selection of Granules with Nitrifying Activity

Figure 10.9 shows the time course of process by SBR operation. After 17 days of start-up, no nitrification occurred. At day 17, the reactor was inoculated with a little of nitrifying sludge. From day 18, weak nitrification happened. After another 3 weeks, the granules with nitrification ability were formed (Fig. 10.9). After the system reached the steady state,

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rn ra 3000

O 1500 m 0

JL 150

800 700 600 500 400 300 200 100 0

: '1

i

:

Fig. 10.9. Parameters of growth and nitrification in microbial granules during their cultivation in SBR.

the mean diameter of granules, SVI of granular biomass, and biomass concentration was 0.6 mm, 22 mL g-1, and 7g L-1, respectively. Nitrite was not detected in the effluent, and ammonium consumption efficiency was very close to 100%. Conversion of the consumed NH+-N to NO--N was 93% and the specific NO--N production rate was 0.12 d-1 at the constant NH+-N loading late of 0.9 kg m-3 d-1.

Figure 10.10 shows the time course of parameters in one cycle by SBR operation. Complete nitrification could be finished during three hours. pH in one cycle first decreased to the lowest value and then increased to a steady state. This pH changing trend has been confirmed in many batch cultures. Peng (1999) also reported the same pH changing trend during

50 100 150 200 Time (min)

50 100 150 200 Time (min)

Time (min)

Fig. 10.10. Parameters of nitrification in microbial granules in one cycle of cultivation in SBR. Following parameters are shown: (a) concentrations of ammonium (•), nitrite (■), and nitrate (A); (b) pH (♦) and alkalinity (■).

Time (min)

Fig. 10.10. Parameters of nitrification in microbial granules in one cycle of cultivation in SBR. Following parameters are shown: (a) concentrations of ammonium (•), nitrite (■), and nitrate (A); (b) pH (♦) and alkalinity (■).

nitrification process by nitrifying sludge. This interesting phenomenon could be applied to monitor if there was complete nitrification, which was much easier than the analysis of nitrogen.

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