1. Estimate the head loss for clean racks using (a) Bernoulli’s equation, and (b) Kirschmer’s equation, assuming:
-inlet channel = 0.68 m, slope of 0.0001, Manning’s n = 0.012
-average flow = 16,000 m3/day
-angle from horizontal = 60°
-bar shape = rectangular
-bar width = 15 mm
-bar spacing = 20 mm
-C = 0.7 (for clean racks)
Recall: Manning’s equation is:
Q= 1R S A2/3 1/2 n where, for a rectangular channel:
R= WD , A WD= W D+2
2. Design a system of screw pumps for the following sewer, plant, and flow conditions:
Minimum sewage elevation = 112.60 m
Maximum sewage elevation = 112.80 m
Discharge elevation to plant influent = 116.40 m Average flow at design life = 8600 m3/d
Peaking factor for peak hour flow = 2.8
Peaking factor for minimum flow at beginning of design life = 0.49 Provide pump diameter, number of flights, and the number of pumps needed.