Question

Question 2: daily peak flow of crude s r screen is installed in a wastewater treatment plant receiving a daily peak flow of crude sewage of 50000 m3. The folowing information are available - Desired velocity through screen at peak flow 0.8 m/s. 5 em clear spacing Using rectangular steel bars with I cm width, 1 m height and placed at - The inclination of screen to horizontal is 90. Estimate the a) net area of screen openings in m2 b) number of bars required, c) total area of screen in m d) approach velocity in m/s, e) headloss through the clean screen in m and f) headloss in m if the screen openings are 40% plugged. 16 marks [6 mark 6 mar 6 ma 6 ma 10 m 40 uestian.3:

Answer 1

2) Daily peak flow = 50000
?7m
= 0.579
?7m
/s

Desired velocity through screen = 0.8 m/s

width = 1 cm = 0.01 m

Height = 1 m

Spacing = 5 cm = 0.05 m

a) Net area of screen openings = 0.579/0.8 = 0.72375 $m^{2}$

b) B * H = 0.72375

B = 0.72375 m

B-72 * s + (n + 1)o

0.72375 = n * 0.05 + (n+1) * 0.01

0.72375 = 0.06 n + 0.01

n = 11.896 ~ 12 bars

c) Total area of screen = (12 * 0.05 + 13 * 0.01) * 1 = 0.73 $m^{2}$

d) approach velocity = 0.579/(12 * 0.05 * 1/sin 90°) = 0.965 m/s

e) Head loss =
2 15
=
0.9652 -0.821 2 9.81 0.7
= 0.0212 m

f) Head loss if screen openings are 40% plugged = 0.0212*0.4 = 0.00848 m