Separate Sewer System
In this system, two sets of sewers are laid. One is used for carrying sewage and the other is used for carrying stormwater.
The sewage is carried to the treatment plant and finally disposed of after treatment. The stormwater is directly discharged into the river or stream.
Condition Favourable For Separate Sewer System
The separate sewer system is favoured under the following condition:
1. If the area is flat.
2. When the rainfall is uneven or it is heavy for a short duration.
3. When it is necessary to pump the sanitary sewage.
4. If the area possesses steep slope.
5. If sewer is to be laid through hard rocky soil.
6. If sewers are to be laid before the area is developed.
7. If it is not possible to lay sewers at suitable gradients.
Advantages of the separated sewer system
Following are the advantages of the separate sewer system:
1. The load on the treatment unit becomes less.
2. The stormwater is not unnecessarily polluted.
3. The sewers are small in size.
4. The stormwater can be discharged into natural streams without any treatment.
5. This system proves to be economical when pumping is required for the lifting of sewage.
Disadvantages of the separated Sewer system
Following are the disadvantages of a separated sewer system:
1. The cleaning of sewers is difficult as they are of small in size.
2. The maintenance cost is high.
3. The self-cleaning velocity is not easily achieved.