Discussion by em. o. Prof. Dr. -Ing. habil. Franz Popel
Stuttgart/B.R.D.
Batch Digestion
The curves in figures 2 and 8 for the BOD removal and the sum of the gas production can be
described by the two following functions:
Oba = O b z (1
with Oba
Obz
=
t
0.002 e 0.0833 . t
1 + 0.00206 . e 0.0833 . t
BOD of the digested substrate,
BOD of the raw substrate,
digestion time in days.
(g/D
(1)
digestion time in days
Oba found
g/1
Oba calculated g/1
20
5.01
4.95
40
4.78
4.86
60
3.80
3.87
80
2.15
2.01
100
0.65
0.66
110
0.185
0.370
g
3.774
1 + 131. e-0.0645 . t ( 1 + 5J6 e -0.0855 . t)
(m /i)
(2)
with g
=
cumulative gas production,
t
=
digestion time
BOD - load = 12.5 g
Temperature 35°C
digestion time in days
digestion gas found 1
calculated 1
20
0.05
0.05
40
0.3
0.299
60
1.0
0.982
80
2.10
2.101
100
3.1
3.115
110
3.40
3.39
The reaction coefficient 0.0645 d"
1
, a little greater than that given by the writers, corresponds better
with the test results, as it is based on the total digestion time and not only on the period considered as
the logarithmic growth phase.
Conventional Digestion.
The datas summarized in table 3 are converted into BOD-load (L), production of gas (g), volatile
acids (VA) and BOD - removal (ΔOb) per volume - unit of the test digestor. Furthermore, the gas -
volatile acids - ratios and the carbon quantities incorporated in the digestion gas have been calculated
in order to find the BOD - carbon - ratios. When developing the functions for these data the
digestion time is replaced by the equivalent expression of the BOD-load per 1 and day.
BOD-load L gO DZ /l-d
gas production g lg/l.d
volatile acids VA gVA/l.d
g/VA ratio lg/gVA
BOD - removal gOb/l-d
carbon in gas gC/l.d
BOD /carbon ratio gOb/gC
1.0
0.64
0.083
7.711
0.914
0.343
2.66
2.0
0.592
0.170
3.482
1.641
0.317
5.177
3.0
0.48
0.333
1.441
2.417
0.257
9.405
4.0
0.2
0.509
0.393
2.402
0.107
22.449
591
Stuttgart/B.R.D.
Batch Digestion
The curves in figures 2 and 8 for the BOD removal and the sum of the gas production can be
described by the two following functions:
Oba = O b z (1
with Oba
Obz
=
t
0.002 e 0.0833 . t
1 + 0.00206 . e 0.0833 . t
BOD of the digested substrate,
BOD of the raw substrate,
digestion time in days.
(g/D
(1)
digestion time in days
Oba found
g/1
Oba calculated g/1
20
5.01
4.95
40
4.78
4.86
60
3.80
3.87
80
2.15
2.01
100
0.65
0.66
110
0.185
0.370
g
3.774
1 + 131. e-0.0645 . t ( 1 + 5J6 e -0.0855 . t)
(m /i)
(2)
with g
=
cumulative gas production,
t
=
digestion time
BOD - load = 12.5 g
Temperature 35°C
digestion time in days
digestion gas found 1
calculated 1
20
0.05
0.05
40
0.3
0.299
60
1.0
0.982
80
2.10
2.101
100
3.1
3.115
110
3.40
3.39
The reaction coefficient 0.0645 d"
1
, a little greater than that given by the writers, corresponds better
with the test results, as it is based on the total digestion time and not only on the period considered as
the logarithmic growth phase.
Conventional Digestion.
The datas summarized in table 3 are converted into BOD-load (L), production of gas (g), volatile
acids (VA) and BOD - removal (ΔOb) per volume - unit of the test digestor. Furthermore, the gas -
volatile acids - ratios and the carbon quantities incorporated in the digestion gas have been calculated
in order to find the BOD - carbon - ratios. When developing the functions for these data the
digestion time is replaced by the equivalent expression of the BOD-load per 1 and day.
BOD-load L gO DZ /l-d
gas production g lg/l.d
volatile acids VA gVA/l.d
g/VA ratio lg/gVA
BOD - removal gOb/l-d
carbon in gas gC/l.d
BOD /carbon ratio gOb/gC
1.0
0.64
0.083
7.711
0.914
0.343
2.66
2.0
0.592
0.170
3.482
1.641
0.317
5.177
3.0
0.48
0.333
1.441
2.417
0.257
9.405
4.0
0.2
0.509
0.393
2.402
0.107
22.449
591