SHORT-TERM EFFECTS OF GLUCOSE ADDITION ON NITRIFICATION AND ACTIVATED SLUDGE SETTLEMENT IN SEQUENCING BATCH REACTORS - Biochemical Engineering - page 278

carbohydrate and protein concentrations in the supernatant were measured by the sulfuric-
phenol method (Dubois et al., 1956) and the Lowry method (Lowry et al., 1951), respectively.
The dynamics of NH 4 -N, NO 2 -N and NO 3 -N concentrations were measured in typical
cycles in the two reactors. The data from the periods when the parameters had linear
relationships with time were used to calculate the nitritation and nitratation rates based on the
reactor volume (the volumetric rate) or the unit of biomass concentration (the specific rate),
respectively.
The morphology of activated sludge was observed with a phase contract light microscopy
(OPTIKA Microscopes, Italy) and photos were taken with a digital camera (INOVO USB2.0-
CAM) connected to the microscopy.

3. Results

3.1. Short-term Dynamics of Various Nitrogen Forms in the Two SBRs

The dynamics of various nitrogen forms in the N-Reactor and the G-Reactor during the
32-day short-term study period are shown in Figures 1 and 2.

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 1. Nitrogen dynamics in the N-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.

At the influent NH 4 -N concentrations of 109.3 ± 8.7 mg/l in the N-Reactor and 109.1 ±
9.1 mg/l in the G-Reactor, the respective NH 4 -N removal efficiencies were 84% in the N-
Reactor and 93% in the G-Reactor. The total oxidized nitrogen (NOx-N: NO 2 -N + NO 3 -N)
concentrations were 97.2 ± 8.4 mg/l in the N-Reactor and 86.1 ± 7.5 mg/l in the G-Reactor.
The high NH 4 -N removal efficiency and the lower effluent NOx-N concentration in the G-
Reactor showed that a high amount of NH 4 -N was used for biomass synthesis by heterotrophs
due to the addition of glucose. In the N-Reactor, the influent total nitrogen (influent NH 4 -N)
was 109 mg/l and the effluent total nitrogen (effluent NH 4 -N + NOx-N) was 115 mg/l. The