<Table-3>
Number of Wastewater Treatment Plants in Japan(Mar.2001)
Treatment method
Capacity(in 1000 cu m/day)
Total
5
5 to 10
10 to 50
50 to 100
100 to 500
500 or more
simple
sedimentation tank
1
1
2

Biological treatment
(Standard)

Conventional
39
57
305
118
127
15
661
Step aeration
1
9
10
7
2
29
Oxygen
1
1
4
1
4
11
Extended aeration
18
5
2
25
Oxidatation ditch
526
71
29
626
Contact stabilization
1
1
Sequencing batch reactar
58
5
4
67
High rate biological oxidation
6
1
7
Rotating biological contactor
12
4
6
1
23
High rate tricking filter
2
2
4
Fixed oxidation
24
24
Aerobic filter
23
1
24
AO filter
12
12
Others
4
1
6
5
5
21

Biological treatment
(High grade)

Nitrification denitrification
4
1
2
6
13
Endogenous denirifications
3
3
A2O
1
1
5
2
9
AO
12
2
13
6
22
5
60
Total
740
151
394
141
174
22
1,622

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