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4 <br /> 11-4 MULTIPASS (RECIRCULATING) PACKED-BED FILTERS 749 <br /> 2. Determine the organic loading rate: <br /> (5.0 gal/ft2•d x 3.785 Llgal x 130 mg/L) <br /> I Lora = <br /> (1000 mg/g x 454 g/lb) <br /> Ik <br /> = 0.0054 lb BOD/fO-d OK(see Table 11-13) <br /> E 3. Lay out gravel filter and the effluent distribution system. Use a spacing of 1.0 ft <br /> (0.3 m)between distribution pipes,orifices,and sidewalls. <br /> a. Determine the number of laterals based on a nominal spacing of 1.0 ft: <br /> Number of laterals = (8 — 1.0)11.0 + 1 = 8 <br /> b. Determine the number of orifices: <br /> Number of orifices = (10 — 1.0)/1 = 9 <br /> c. The layout of the gravel filter and distribution system is shown below. <br /> 9 f <br /> - <br /> C n <br /> F <br /> I <br /> t o tl L I <br /> 4. Determine the quantity of flow per dose and the flowrate in each lateral. <br /> a. Determine quantity of flow discharged per dose: <br /> Flow/dose (150 gaud x 5)/(48 dosed) = 15.6 gal/dose <br /> b. Determine the discharge per lateral, <br /> How/lateral = (15.6 gaUdose)/8 laterals = 1.95 gal/laieral-dose <br /> { 5- Using Eq. (11-7), determine the rate of discharge from an orifice, assuming 5 ft of <br /> residual head at the orifice: <br /> qn = 2.45C(D2) 2ghn <br /> = 2.45(0.63)(0.125)2 2(32.2)5 = 0.43 gal/min•orifice <br /> 6. Determine the duration of the flow and the volume of flow discharged at average flow. j <br /> a. The total flowrate,based on 9 orifices/lateral, with 8 laterals, is <br /> Flowrate/lateral = (0.43 gal/min-orifice)(9 orifice/lateral) <br /> = 3.9 gal/min-lateral a <br /> QT - (3.9 gal/min-lateral)(8 laterals)' = 31 gal/min j <br /> f <br /> I <br />