Complete information on different Systems of Drainage or Sewerage

(i) Separate system:

Rain water is kept separate from sewage.

(ii) Combined of single sewer system:

One set of pipes takes both sewages & rain water.

Advantages of Separate System:

(a) Load on treatment units become less.

(b) The natural water is not unnecessary polluted.

(c) The sewers are small in size.

(d) The storm water can be discharged into natural streams without any treatment.

(e) The system proves to be economical when pumping is required for the lifting of sewage.

Disadvantages of Separate System:

(a) The cleaning of sewer is difficult, as they are of small size.

(b) The maintenance cost is high.

(c) They self-cleaning velocity is not easily achieved.

(d) The system requires two sets of sewer end hence; it may prove to be costly.

(e) The storm water sewers will come into operation during monsoon only. Hence, they may become the dumping places for garbage during summer and winter and may thus be chocked.

Advantages of Combined of Single Sewer System:

(a) It is easy to clean a combined sewer as it is of large size.

(b) The maintenance costs are reasonable

(c) The storm water reduces the strength of sewage by dilution.

(d) This system requires only one set of sewers and it may thus prove to be economical.

Disadvantages of Combined of Single Sewer System:

(a) During ordinary heavy storms, the combined sewers may overflow and it may thus put public health in danger.

(b) The combined sewer, if not properly designed, gets easily silted and it may even become foul in dry weather.

(c) The load on treatment plant increases.

(d) The sewers are huge in diameter.

(e) The storm water is unnecessary polluted:

(f) The system proves to be uneconomical when pumping is required for the lifting of sewage.

(iii) Partially Separate System:

In this system, arrangement is made to permit early washings by rain into the sewers carrying sewage. But when the quantity of storm water exceeds a particular limit, it is collected and conveyed in open drains to the natural river of stream.

Advantages of partially Separate System:

(a) It combines the advantages of both the above systems.

(b) The entry of storm water avoids silting in sewers.

(c) The problem of disposing storm water from houses is simplified.

(d) The sewers are of reasonable size.

Disadvantages of Partially Separate System:

(a) The quantity of storm water admitted in sewer may increase the load on pumping & treatment unit.

(b) The velocity of flow is low in dry weather.