Mesophilic Digestion of Beet Molasses Distillery Waste Water
585
100
a
o
m
m
3 gas/Kg. BOD removed
0.8|
0.6
0.2
_L
J_
10
15
Detention time
20
Fig. 3.
Table 3
Results of Conventional digestion at different loadings and detention time
Detention
time in
days
25
15
10
7
B.O.D.
Influent
(mg/1)
25,004
30,075
30,000
27,900
B.O.D.
Effluent
(mg/1)
2,441
5,436
5,830
11,192
B.O.D.
Removal
(%)
90.2
81.9
80.6
59.9
Volatile
Acids
(CH 3
COOH)
(mg/1)
2,074
2,549
3,327
3,563
Alkalinity (as
CaC0 3 )
(mg/1)
3,092
3,641
4,105
3,290
Gas Content (%)
CH 4
64
60.8
54.5
20.3
C 0 2
35
38.1
42.8
66.7
Others
1.0
1.1
2.7
13.0
Vol.
Gas
ml/d
1,600
1,480
1,200
500
Table 4
Results of High rate digestion at different loadings
Detention
time in
days
10
10
10
10
B.O.D.
Influent
(mg/1)
20,005
25,000
32,013
35,000
B.O.D.
Effluent
(mg/1)
812
895
1,299
9,194
B.O.D.
Removal
(%)
96.0
96.4
95.9
73.7
Volatile
Acids
(CH 3
COOH)
(mg/1)
1,064
1,438
1,795
3,085
Alkalinity (as
CaC0 3 )
(mg/1)
3,338
2,948
3,336
3,620
Gas Content (%)
CH 4
64.0
62.0
59.0
29.5
C 0 2
34.5
35.2
38.0
64.0
Others
1.5
2.8
3.0
6.5
Vol.
Gas
(ml/d)
4,098
5,450
7,010
2,060
High rate digestion
Since earlier experiments with conventional digestion established that the process
failed at 4 kg/m
3 .d a higher detention time was used, and the organic loadings varied so as
to arrive at the optimum efficiency. Stirring was done by a mechanical stirrer, and the
feeding was semi-continuous. As with conventional digestion, the loadings in the digestors
were gradually increased.
Four sets of experiments in duplicate were set up with organic loadings of 2.0, 2.5, 3.2
and 3.5 kg/m
3 .d corresponding to a fixed detention time of 10 days for all experiments.