222 W MARINE VIEW DR 2016-01-01 MF Import

y gradient in the fluid. acosity of the Huid, and des of Eq. 8•3 by the �S'9) hout 15 to 30 min vary ary from 10' to 10° [9j. follo�cing example. e Area lor Flxculator =ment and the paddle area '' in a tank a•ith a volume temperature is 60°F, the :dles is 1.5, the paddle•tip zlocity oi the paddla v is quirement. `f�� :ec osal 283 SEDIMENTATION Sedimentation is the separation of suspended particles that ure heavier than �ceter from �cater b}• grnvitationnl settling. It is one of the most nidely used unit operutions in ��•aste�cater treatment. This operation is used for grit removal, pnrticiilate-mutter removal in the primnry settling basin, biologicel-floc removul iu the activnted-sludge settling basin, chemical-floc remocal �chen the chemical coagu]ation pracess is used, and for solids concentrution in sludge thickeners. In most cases, the primary purpose is to produce a clarified eHiuent, but it is al�o necessary to produce sludge ��ith a solids concentrnfion thnt can be ensily h¢ndled nnd treated. In other processes, such as sludge thicken- ing, the primary purpose is to produce a concentrated sludge thnt can be treated more economically. In tl�e de�ign of sedimentntion basins, due consideretion should be given to production of both :ti clarified eftluent and a concentrated sludge. On the busis of the wncentrntion nnd the tendenc}• of the pnrtides to interact, four genernl classificntions of the manner in �chich particles settle can be mnde. It is common to have more thun one t�•pe of setding taking place nt u gicen time during a eedimentatinn operntion, and it is possible to h�ve all four occurri�g simultnneousl}�. T}•pe-1 settling refers to the sedimentntion of discrete pnrticles in a suspension of lo�c solids concentration. Particles settle ns indi��idual �' entities, and there is no eignificant interaction �cith neighboring pnr- ticles. A typicnl example is a dilute suspension of grit or snnd pnrticles. � This type of settling is al:ro called free settling. ' Type-2 xettling refers to a rathr• ailute suspension of pnrtides thnt coalesce, or flocculate, during the selimentation operation. Bp coalesc- y��'- ing, the particles incrensa in mass nnd'settle at a faster rute. ,y Type-3 settling occurs in suspensions of intermedinte concentrn- '� tion, in ��•hich interpnrticle forces are suflicient to hinder the settling �of neighboring particles. The particles tend to remain in fised positions ` �cith respect to each other und the maes of pnrtides settles as a unit. ii :1 distinct solids-liquid interface decelops at the top of the retding ;� sludge mass. This t}•pe of settling is generally called zone �ettling. Type-4 settling occurs �chen the particles nre of such concentrntion � that a sh•ucture is formed nnd further setding can occur only by com- pression of the structure. Compression tskes pince due to the ��•eight of � the particles, �chich nre constantly being ndded to the structure by `� sedimentntion from the supernntant liquor. This tppe oi settling is called compressimi settling and occurs usunll}• in the lo�cer la>•ers of deep sludge mnsses. Physfcal Unit Operatlons