Question

Using the values provided in Table 21-1, minimum sewage elevation in interceptor of 112.60 m, maximum sewage elevation in interceptor of 112.80 m, discharge elevation to stilling well of 116.40 m, an average design flow of 8,600 m³/d, peaking factor for peak hour of 2.8 and minimum factor of 0.49.

A. Determine the most efficient screw pump diameter (in m)
B. How many flights are recommended
C. How many pumps are recommended in the final design?

Typical/comment TABLE 21-1 Typical design criteria for primary sedimentation basins Parameter Range of values General Overflow rate (average flow) 30 to 50 mº/dm2 Overflow rate (peak flow) 60 to 120 mld - m? Detention time (average flow) 1.5 to 2.5 h Flow velocity 0.020 to 0.025 m/s Weir loading rate 125 to 500 m®/ dm Sludge hoppers 1.7 vertical to 1 horizontal Geotechnical 40 m/d - m² 100 mld - m 2.0 h 250 mºld - m Minimum; bottom width < 0.6 m Consider potential for flotation when tank is empty Circular tanks 3 to 100 m 9 to 45 m 3 to 5 m I vertical to 12 horizontal 12 to 45 m In 1.5 m increments 4.3 m Dimensions Diameter Standard Side water depth Floor slope Splitter box Inlet velocity Inlet configuration Detention time Submergence EDI detention time <0.3 m/s At peak flow 20 minutes 30 to 75% of depth 8 to 10 s Feedwell Size to prevent scour (continued)

Answer 1

max. height the strene pump must lift = Discharge elevation - min. Sewage elevation = 116.40 – 112-6 - 3-87 Mini an flow rate = Ratio factos minimums flom at begining of desisn life x Aug. flow at desism lite -0.49 X 8,6oon/des = 4214 m3/dy peak hous flow rate = Peak factos x Aug. flove at desisn life = 2.8 x 8,650 = 24080 m3/ds (Here, Ratio fectos for min floue is 0.49 & P.F as 2.8)

Min. flow rate - 4214 m3/d 24 hoold = 175-58 m3/h Aug. flow rate = 8600 wild . 24 h/dy = 358:33 m3/15 peak for flow rate = 24080 m3/h -= 1003-3 uplo - 24 holds Capacity of pump = 175.58 m3/ng 0:3 =585-27 43 )ws Base on this capacity, the standard screw diameter for I flint is 1.07m rated at 621 m3/s. No-of Pumps - man. flow rate capacity of one pump 10003.33 621 = 1+62 ~ 2 pumps Eficiency of pump = 358 33 20.57 ~ 574

- The dia of Pump j 1.07m, no. of flisnts are le no. of Pumps are "3 ... Cone Puup out of Sesnice)