Sunday, 8 July 2018

Combined Sewer System And Their Advantages & Disadvantages

In this system only one set of sewer is laid and it carries both sewage and storm water. The sewage and storm water are carried to the sewage treatment plant and finally disposed off. 

Conditions Favourable for Combined System

The combined system is favoured under the following condition: 
1) If the rainfall is small and evenly spread throughout the year .
2) When space available for the laying of sewer is restricted .
3) When pumping is required for sanitary sewage as well as storm water .
4) When the amount of sewage is less

Advantages of Combined Sewer System

Following are the advantages of combined system:
1) The cleaning of sewers is easy as they are of large in size .

2) The maintenance cost is less .
3) The storm water reduces the strength of sewage by dilution .
4) The self cleaning velocity is easily achieved .
5) This system requires only one set of sewer. Thus it becomes economical. 

Disadvantages of Combined Sewer System

Following are the disadvantages of combined system: 
1) The load on treatment plant becomes high. 
2) The storm water is unnecessarily polluted .
3) The sewers are large in diameter .
4) This system proves to be uneconomical when pumping is required for lifting of sewage .
5) During a heavy storm, the combined sewer may be over flown which may create trouble for the people. 

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