SHORT-TERM EFFECTS OF GLUCOSE ADDITION ON NITRIFICATION AND ACTIVATED SLUDGE SETTLEMENT IN SEQUENCING BATCH REACTORS - Biochemical Engineering - page 279

increased total nitrogen concentration in the N-Reactor could be attributed to the lysis of
bacteria in the reactor due to shortage of carbon substrates. NO 2 -N was the main component
of the total NOx-N in the effluent in both reactors, with ratios (NO 2 -N/NOx-N) of 0.69 in the
N-Reactor and 0.67 in the G-Reactor.

160

NH4-N -IN NH4- N-EFF NO2-N NO3-N

120

80

40

0

0 4 8 12 16 20 24 28 32

Time (day)

Figure 2. Nitrogen dynamics in the G-Reactor during the short-term study period. NH4-N-IN: NH 4 -N in
the influent; NH4-N-EFF: NH 4 -N in the effluent; NO2-N: NO 2 -N in the effluent; and NO3-N: NO 3 -N
in the effluent.

3.2. Typical Cycle Study in the Two SBRs

In order to examine the nitrification activity and the nitrite accumulation in detail, on Day
19, the dynamics of various nitrogen forms and pH in a react cycle in both reactors were
examined and the results are shown in Figures 3 and 4.
Nitrification mainly occurred within initial 14 hours and there was little change
thereafter. Therefore, only parameters obtained within the initial 14 hours are presented.
Using linear regression, the volumetric nitritation and nitratation rates were 5.4 mg/l·h and 1.6
mg/l·h in the N-Reactor, and 6.4 mg/l·h and 2.6 mg/l·h in the G-Reactor. However, the
specific nitritation and nitratation rates based on unit biomass concentrations were 9.4 mg/g
VSS·h and 3.9 mg/g VSS·h in the N-Reactor, and 4.2 mg/g VSS·h and 1.7 mg/g VSS·h in the
G-Reactor.
The NO 2 -N/NOx-N ratios, obtained at Hour 14 in both reactors, were 0.69. Based on
Equation 1, the NH 3 concentration ranged from 0 to 4.2 mg/l in the N-Reactor and from 0 to
1.5 mg/l in the G-Reactor. According to Equation 2, the HNO 2 concentration ranged from 0 to
0.25 mg/l in the N-Reactor and from 0 to 0.24 mg/l in the G-Reactor. With the processing of
nitrification, pH decreased with time in both reactors. pH varied from 8.4 to 5.9 in the N-
Reactor and from 8.0 to 5.9 in the G-Reactor. When the pH was above 6.0, the nitrification
rate was constant, and this reflected from the good linear regression of the produced NO 2 -N