1. Assignment 7 sewer.
Side-view:
Rainfall & Rainfall &
Waste water Waste water
GL (ground level) +6.00 m
+5,5 m
P4 P3 P2
Ø500 concrete
P1 weir
Ø300 PVC
Ø250 PVC IL +4,00 m
IL +3,90 m
IL +3,73 m
Pump 50 m
IL (invert level +3,53 m)
Additional information:
- equivalent roughness k-concrete = 1,5 mm, k-PVC = 1 mm
- width weir = 2 m
Preparation
Calculate for each pipe: A, R (submerged) , C (rough boundary) and bed slope
Question 1 (Only wastewater, no precipitation)
a)In this situation the PVC250 pipe is half filled with waste water. Calculate the discharge and
velocitiy.
b)Check if the flow is turbulent
Question 2 (Only wastewater, no precipitation)
The supply of waste water on P3 and P2 is 10 l/s (both manholes). The pump capacity is 20
l/s. Calculate the water depth in pipe P2-P3 . Also calculate the velocity and hydraulic radius.
Question 3 (Rain, precipitation)
3,75 ha paved area is connected to P2, 1,1 ha paved area is connected to P3. The rainfall
intensity is 60 l/s.ha.
a) Calculate the discharge rainwater which will flow from the paved area into the sewer?
The figures show that the amount of rainwater in the sewer is much more than the amount of
waste water. For the next questions we will neglect Waste water and the pump capacity.
b)Indicate the direction of the flow with rainfall. Calculate the discharge for each pipe.
c)Calculate the specific height (H) at the weir (c=1,8)
d)Calculate the head loss for branches P4-P3, P3-P2 and P2-P1. Also calculate the velocity
head and velocity for each branch. Use Chezy’s formula.
e)Calculate for each manhole the energy level and water level
f)Check if the flow is turbulent
Henk Massink, 5 april 2013