Project 3 A sewer system is to be designed to service the re

Project 3 A sewer system is to be designed to service the residential area shown in the figure below. The sewer system is to joi the design period is 0.4 m/s. the /I contribution to the flow in the main sewer at MH1 is negligible. The VI is estimated to be 75 m\'/d/km. when the system is first installed it is estimated that the average flow rates will be 30% of the average flow when the area is fully developed. Design the sewer system considering that the sewer lines must be lower than the basement of the served houses n an existing main sewer at MH1 where the average wastewater flow rate at the end of MH4 50 m MH3 50 m MH5 50 m MH2 50 m 50m MH1 E Arens Rd MH7 E Arens E Arens Rd E Arens

Solution

Step 1:Given data:

Total discharge= 0.4m³/sec

Infiltration/inflow=75m³/day/km

step 2: Calculation of parameters:

As we can see that the sewers are connected in series, the discharge is going to remain the same for each and every sewer and the diameter is constant for every sewer

total length in that area=300 m

Total infiltration/inflow=75m³/day/kmx300/1000m

I/I=22.5 m³/day (for that area)

step 3: Calculation of discharge:

It is given that the discharge is 30% of the average discharge

Q1=0.3x0.4

Q1=0.12 m³/sec

step 4: Calculation of diameter:

from continuity equation we know that

Q=AV

Q=0.785xdxd22.5

0.12=0.785xd²x22.5

d=24.23 m