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cles cnn be aualyzed by <br />nulated by \e�cton and <br />icle veloc;ty bp equating <br />ional resistunce, or drag. <br />le �•elocity, fluid density, <br />lg C00�1CIERL QD �d1IDBR- <br />(s•11) <br />of particle at right angles <br />eight of the particle, !or <br />ig'12) <br />nt values depending on <br />rticle is laminar or turbu- <br />8�4 as a function of the <br />� affects the value of the <br />�rve in Fig. S•4 is appro�i- <br />it of NR = 10') [9J: <br />(8•13) <br />;posal <br />k <br />;; <br />; <br />Kli <br />A <br />U <br />� <br />V <br />U <br />O <br />Ve <br />O <br />Q <br />o.uooi o.u> >.0 iuu �o.uoo �.000.000 <br />Reynolds number. N� e �=� <br />v <br />285 <br />FIG. 8•4 Urag coeilicients at <br />spheres, disks, enE cyli�ders <br />j13�. <br />For Repnolds number3 less than 0.3, the first term in Eq. S•13 pre- <br />dominates, and substitution of this drag term into Eq. &12 �•ields <br />Stokes' ln«�: <br />j�` a 9�P. — P�di <br />18p <br />For laminar flo�v con3itions, Stokes found the drag force to be <br />F� = 3x�md <br />(s•i4> <br />(S•15) <br />Equating this force to the effective particle «•eight also yields Eq. S•14. <br />In the design of sedimentation basins, the usual procedure is to <br />select u particle ��•ith a terminal velocity V, and to design the bnsin so <br />that ell particles thnt hnr•e n terminnl celocity equsl to or greater than <br />V� ��ill be removed. The rnte at e•hich clarified �cat.er is produced is <br />then <br />Q = AV< <5�16� <br />�chere d is the surface nren of the sedimentetion busin. Equntion S•16 <br />�•ields <br />V, = A= overRou• rate, gpd/sq ft <br />��•hich sho��'s thut the overHo�c rate or surFnce loading rnte, n common <br />bnsis of design, ie equivalent to the settling ��elocity. Equation S46 <br />also indicates thnt for tppe-1 setding the flo�c capacity is independent <br />of the depth. <br />For continuous-fto��• sedi 7entation, the length of the b�sin nnd <br />the time u unit volume of ��•nter is in the bnsin (detention time) should <br />Physlcal Unit Operotlons <br />