Question

Horizontal-shaft paddle wheel flocculators are to be used for flocculation in a water plant with a design flow rate of 150 mld (million-liter per day) and water temperature of 10oC. Flocculation is to be designed with two parallel trains and each train is to be made off five stages of flocculation in series. The total detention time for flocculation is to be 20 min. Two paddle wheels will be on the shaft in each stage. The paddle wheel design contains 4 paddle arms and each paddle arm has three paddle blades with leading edges located at 0.67, 1.33, and 2.0 m from the shaft centerline. The width of the paddle blade is 0.15 m. Determine the following design features for the second stage in each flocculation train: A) Dimensions of the stage (depth, volume, area, length, and width) B) The power input required to achieve a gradient velocity (G) value of 40 s−1 C) The rotational speed of the paddle shaft.

Answer 1

Given Q = 150 Mld of trup (t) = 10 c. Trains 2 parallel Each Train – 5 stages in series Total = 20 min Each stage 2 paddle wheels Each paddle wheel – ut paddle Arais Each am - 3 Blades The leading edges of Blades are located at 0.64m, 1.835 & 2n from the shaft centerline s Blades am - Shaft am o. 115 width of paddle Blade = 0.15m Total width of each stage 0.15 +2 +2 +0.18 = 4.1500 B (of each stage) = 4.15m

Total = 150 MLd & (per Each Trains) - 150 - 45 Med Q ( for each stage) ISMLd. D = 20 min - vol = QX DE INFO - 15 10 x20 L 24x60 = 208333.32 = 208. 33 m3 Standard wo min water depth = 4.15m rade So prouide = 5m H=sm Surface area 209.33 41.66 Surface area = hength & width width = B (of each stage) = 4.15m SA = L x B 10.04 L B - 41.66 4.18 L = 10.04m

& Given G-40ls with or Powey = 1.307 X10 N- Dynamic viscosity of water at 100 (M) U1.30 u = 1-30+ x10 pa-s Power - G²u M ixel - V: Vol LBH M= Dynamic viscosity Power - uob? (208,33) (1-304 x103) = 435.65 MM Power = 435.65 Nm @ 435-65 Ils S