Biomedical Engineering Reference
In-Depth Information
Anaerobic Phase 0th min.
Anaerobic Phase 120th min.
Anoxic Phase 0th min.
Anoxic Phase 120th min.
7.0
10.0
Removal Efficiency
9.0
6.0
8.0
5.0
7.0
6.0
4.0
5.0
3.0
4.0
3.0
2.0
2.0
1.0
1.0
0.0
0.0
C/N=12
C/N=6
C/N=3
Figure 4. TP removal in anaerobic-anoxic SBR reactors during PAO deactivation.
3.1.2. PAO Deactivation in SBR Reactors
PAO deactivation was observed in three anaerobic-anoxic SBR reactors feeding with
different C/N ratio synthetic wastewater and seeded with waste sludge from the parallel AN/AO
process; results were shown in figure 4. No significant phosphorus release occurred in reactors 1
and 2 (0.9mgL-1 and 0.7mgL-1 respectively; C/N=12 and 6 respectively); negative phosphorus
release was even observed in reactor 3 (C/N=3). For all the reactors, negative phosphorus uptake
occurred, which indicated complete activity loss of PAO in the reactors.
Measured DOC at the beginning of anoxic stages was 15.9-24.1 mgL-1 and measured
NO
3
-
-N concentration at the beginning of anaerobic stages was 2.8-7.2 mgL
-1
.
3.2. PAO Rejuvenation
3.2.1. PAO Rejuvenation in Parallel AN/AO Reactors
PAO rejuvenation occurred when SRT was changed from 30d to 15d (figure 2(c)) and
when HRT was changed from 18h to 9h (figure 3(c)). The fast rejuvenation process indicated
that SRT and HRT were main operational factors that influence phosphorus removal capacity
of the process.
3.2.2. PAO Rejuvenation in SBR Reactors
PAO rejuvenation occurred in anaerobic-anoxic SBR reactors by reducing DOC
concentration at the beginning of anoxic stages (anoxic phase 0
th
min.) and NO
3
-
-N
concentration at the beginning of anaerobic stages (anaerobic phase 0
th
min.) to as low as 3.0
mgL-1 and 2.3 mgL-1 respectively, which was done by washing the remaining MLSS with
distilled water at the end of anoxic stages and anaerobic stages respectively. Results were
shown in figure 5.
