Table 3.4
Design criteria for activated sludge processes for the State of Illinois
– tank capacity and permissible loadings
Process type
BOD and
SS
%
Removal
Design
Flow
MGD
BOD
loading
lb/1000 ft
3
/
d
Detention time
h
MLSS/
BOD
lb/lb/d
Detention time
h
Surface
Settling
rate
gpd/ft
2
Weir overflow
rate
gpd/ft
Extended aeration 70
All
To 20
24
10/1 to
20/1
(To 0.05 MGD) 4.0 300
5000
(0.05–0.15 MGD)
3.6
300
5000
(0.15 MGD up) 3.0 600
5000
Contact
stabilization
90
To 0.5
30
3.0 mix, 6.0 reaer.
2/1 to 5/1
3.6
500
5000
0.5–1.5
30–50
2.0–3.0 mix, 4.0–6.0
reaer.
3.0
600
10,000
1.5 up
50
1.5–2.0 mix, 3.0–4.0
reaer.
2.5
700
10,000
Step aeration
90
0.5–1.5
30–50
7.5–5.0
2/1 to 5/1
(To 0.05 MGD) 3.0 600
5000
90
1.5 and u 50
5.0
(0.5–1.5 MGD) 2.5 700
10,000
p
(1.5 MGD up) 2.0
800
10,000
Complete mix
90
All
35
6.0
2/1
2.0
500
5000
Conventional
90
To 0.5
30
7.5
2/1 to 4/1
3.0
600
5000
0.5–1.5
30–40
7.5–6.0
2.5
700
10,000
1.5 and
up
40
6.0
2.0
800
10,000
Source: US EPA
3 Biological Processes
107