Activated Sludge Treabnent Plants
Parameter
Symbol
Unit
Sludge loading kg BOD I (kg SS · d)
0.05-Q.lO
0.20-Q.30
O.SQ-0.60
Sludge concentration Xss
kgSS/m 3
4.0-7.0 I)
3.0-5.0 I)
3.0-5.0 I)
Sludge concentration Xvss
kgVSS/m 3
2.5-4.5 I)
2.Q-3.5 I)
2.0-3.5 1 )
Sludge concentration Xcoo
kgCOD/m 3
3.5-6.5 1 )
3.0-5.0 I)
3.0-5.0 I)
VSS of 55 in sludge
-
%
65-70
7Q-75
7o-75
Volumetric loading
Bv,BOo
kgBOD/(m 3 · d)
0.2-o.6 1 )
0.6-1.5 1 )
1.5-3.0 I)
Sludge loading
Bx,BOD
kgBOD/(kgVSS· d)
0.08-0.15
0.3-o.45
0.7-0.85
Yield constant
YBQD
kgSS/kgBOD
0.6-0.9
0.9-1.1
0.9-1.2
Yield constant
Ycoo
kgCOD/kgCOD
0.3-Q.S
0.4-o.6
0.4-o.6
Treatment efficiency EBOD
o,.{,
90-95
85-90
80-90
Treatment efficiency Ecoo
%
75-85
70-80
65-80
Sludge age
9x
d
15-20
3-6
1-3
I) North American practice corresponds to approx. 50 per cent of the values stated.
Table4.5
Quantities for different parameters in ordinary activated sludge plants in Europe treating domestic
wastewater (concentrations C1 = 0.2-Q.4 kg BOD/m 3 and 0.4-Q.8 kg COD/m\ T = 10°C.
The volumetric loading is a secondary design parameter and should therefore be
used with caution. It cannot be used for the design of more complicated processes.
Example 4.7
On the basis of the volumetric loading, design an activated sludge plant to treat the wastewaters in Table 4.6 to an effluent concentration of 0.020 kg BOD/m 3 .
Parameter
Unit
Dry-weather
Wet-weather
Ql
m 3 /d
5,000
9,000
m 3 / h(max.)
420
750
C1
kgBOD/m 3
0.240
0.160
kgCOD/m 3
0.510
0.360
kgTN/m 3
0.040
0.028
kgTP/m 3
0.012
0.007
Q1 ·C1
kgBOD/d
1,200
1,440
kgCOD/d
2,550
3,240
kgTN/d
200
252
kgTP/d
60
63
Table4.6
Wastewater data for a town distributed on dry-weather and wet-weather days.
The dry-weather and wet-weather treatment efficiency for BOD, respectively, should
be:
Esoo = (240- 20)/240 = 0.92 dry-weather days
Esoo = (160- 20)/160 = 0.88 wet-weather days
135
Parameter
Symbol
Unit
Sludge loading kg BOD I (kg SS · d)
0.05-Q.lO
0.20-Q.30
O.SQ-0.60
Sludge concentration Xss
kgSS/m 3
4.0-7.0 I)
3.0-5.0 I)
3.0-5.0 I)
Sludge concentration Xvss
kgVSS/m 3
2.5-4.5 I)
2.Q-3.5 I)
2.0-3.5 1 )
Sludge concentration Xcoo
kgCOD/m 3
3.5-6.5 1 )
3.0-5.0 I)
3.0-5.0 I)
VSS of 55 in sludge
-
%
65-70
7Q-75
7o-75
Volumetric loading
Bv,BOo
kgBOD/(m 3 · d)
0.2-o.6 1 )
0.6-1.5 1 )
1.5-3.0 I)
Sludge loading
Bx,BOD
kgBOD/(kgVSS· d)
0.08-0.15
0.3-o.45
0.7-0.85
Yield constant
YBQD
kgSS/kgBOD
0.6-0.9
0.9-1.1
0.9-1.2
Yield constant
Ycoo
kgCOD/kgCOD
0.3-Q.S
0.4-o.6
0.4-o.6
Treatment efficiency EBOD
o,.{,
90-95
85-90
80-90
Treatment efficiency Ecoo
%
75-85
70-80
65-80
Sludge age
9x
d
15-20
3-6
1-3
I) North American practice corresponds to approx. 50 per cent of the values stated.
Table4.5
Quantities for different parameters in ordinary activated sludge plants in Europe treating domestic
wastewater (concentrations C1 = 0.2-Q.4 kg BOD/m 3 and 0.4-Q.8 kg COD/m\ T = 10°C.
The volumetric loading is a secondary design parameter and should therefore be
used with caution. It cannot be used for the design of more complicated processes.
Example 4.7
On the basis of the volumetric loading, design an activated sludge plant to treat the wastewaters in Table 4.6 to an effluent concentration of 0.020 kg BOD/m 3 .
Parameter
Unit
Dry-weather
Wet-weather
Ql
m 3 /d
5,000
9,000
m 3 / h(max.)
420
750
C1
kgBOD/m 3
0.240
0.160
kgCOD/m 3
0.510
0.360
kgTN/m 3
0.040
0.028
kgTP/m 3
0.012
0.007
Q1 ·C1
kgBOD/d
1,200
1,440
kgCOD/d
2,550
3,240
kgTN/d
200
252
kgTP/d
60
63
Table4.6
Wastewater data for a town distributed on dry-weather and wet-weather days.
The dry-weather and wet-weather treatment efficiency for BOD, respectively, should
be:
Esoo = (240- 20)/240 = 0.92 dry-weather days
Esoo = (160- 20)/160 = 0.88 wet-weather days
135