Thesis - faculty.ait.ac.th - Asian Institute of Technology

COD Removal Efficiency
(%)
90
80
70
60
50
40
30
20
10
0
BMBR YMBR
0 20 40 60 80 100 120 140 160 180
Time (days)
Figure 4.17 COD Removal Efficiency in the BMBR and YMBR at Different HRT
The average COD removal efficiency in YMBR system was 63% when HRT
ranged from 16 h to 24 h, whereas in BMBR system, the average COD removal efficiency
was 60% at HRT from 16 h to 24 h as listed in Table 4.6 and Table 4.7. When municipal
wastewater with 300 mg/L COD was treated, a 97% of removal could be achieve (Fan, et
al., 1996). At HRT of 12 h, the average COD removal efficiency in YMBR and BMBR
was to 60% and 51%, respectively. The decrease in removal efficiency in the bacterial
system at a lower HRT was more apparent, which could be due to the presence of
ammonia in the leachate posing toxicity to the bacterial culture. This aspect is also
supported by the biokinetic studies, which states that the ammonia inhibits bacterial cells to
a greater extent than the yeast cells.
The COD removal in 12 h HRT in both the reactors was very low compared to that in
other HRTs. In addition to a better COD removal efficiency, YMBR was more stable than
BMBR. As, the yeast system did not show a significant improvement compared to bacteria
in terms of COD removal, it could be suggested that further investigations are required to
conclude.
Table 4.6 COD Removal Efficiency in YMBR System at Different HRT
Values
COD Removal (%)
HRT 24 h HRT 20 h HRT 16 h HRT 12 h
Maximum 69 70 75 72
Minimum 58 60 59 50
Average 63 64 66 60
Std. Dev. 4 4 6 8
85
26
24
22
20
18
16
14
12
10
8
HRT (h)