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5 reak on maximum cay 3 Manimum, 24h. 2 Average daily discharge Ratio of average daily discharge 10 09 06 02 OG 05 0.4 Minmun, 24 M. 03 0.2 Extreme minimum on minimum day 0.1 0 02 03 04 05 06 0.8 10 15 20 30 40 50 60 80 100 2 3 4 5 6 7 8 9 10 Average daily discharge of domestic sewage, in med FIGURE 19.2: Ratio of Extreme Flows to Average Daily Flow in New England. (Mgd x 3,785 = cu m/day.)
A sewage pumping station is to contain three automatically controlled pumps. Domestic wastewater flows into the wet well at an average rate of 1.5 MGD, through a 600 mm sewer. The invert elevation of the sewer at wet well is 25.00 m with the ground elevation of 30.50 m. Calculate: Two duty pumps (i) Minimum hourly and peak hourly rates of flow into the wet well. Use Figure 19.2. (ü) Capacity of each pump (in mühr-1). Provide one pump for sav, one for Q, and one for Qo Qay). ii) + One standby pump (iii) Volume and diameter of wet well. Use 20 min. detention time at average flow rate. (iv) Sizes of suction and delivery pipes for each pump. (v) Size of the common force main and velocities with different pumps in operation. (vi) Cut-in and cut-off levels for each pump. (vii) Minimum time for which each pump remains in operation between cut-in and cut-off levels.