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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Table 5, Data For Peak Filter Operation, <br /> <br />1. Hi~h performance days (1993) with 3 backwashes per d<\y: <br /> <br />Shift <br />(Hrs) <br /> <br />Raw/Finished <br />(NTU) <br /> <br />Filter Runs <br />(Hrs) <br /> <br />Production <br />(MG) <br /> <br />June 30 16,2 * <br /> <br />2.4/n,a, <br /> <br />4,0, 5,5, 3,0+ <br /> <br />0,714 <br /> <br />July 7 16,5 <br /> <br />1.50/0,39-0,50 <br /> <br />6,1,6,2,2,3+ <br /> <br />0,928 <br /> <br />2, Filter performance criteria for mixed-media filters: <br /> <br />Existing <br /> <br />USEPA <br /> <br />CDOH <br /> <br />Loading rate (g,p,m.lft2) <br /> <br />2,9 <br /> <br />2- 8 <br /> <br />5 (max) <br /> <br />Backwash rate (g,p,m.lft2) <br /> <br />6,5 <br /> <br />15-20 <br /> <br />20 <br /> <br />Backwash time (min) <br /> <br />12-13 <br /> <br />10-15 <br /> <br />Influent pipe velocity <br />(fps) <br /> <br />3,0 <br /> <br />2,0 (max) <br /> <br />* Estimated <br />n,a, = not available <br /> <br />By any existing standard, the present system is inadequately designed, Assuming complete <br />instantaneous mixing of the C12 solution and no short-circuiting of the water in the clearwell, <br />contact time may be as low as 5 minutes, Due to the position of inflow pipes and pump <br />intakes, in practice, contact times are probably much less than 5 minutes at the withdrawal rate <br />of Pump No, 1, The accepted standard for contact time in a clearwell, or prior to the first <br />use, is 30 minutes minimum, Performance capacity for this process has arbitrarily been <br />estimated at 1.32 MG x 5/30 minutes = 0,22 MGD, or less, <br /> <br />21 <br />