Design of Flocculation Tank
Design a conventional rectangular horizontal-shaft flocculation tank unit for 10 MLD of settled raw water after coagulant addition and rapid mixing as per design parameters given below:
Detention time (t): 10 – 30 minutes
Velocity gradient (G): 20 – 75 /s
Gt: 2 x 104 – 6 x 104
Tank Depth (D): < 5 m
Paddle tip speed (vp): 0.25 – 0.75 m/s
Velocity of paddle relative to water (v): 0.75 x paddle tip speed
Paddle area (Ap)/Tank section area (AT): 10:100 to 20:100
Coefficient of drag on paddle blade (CD): 1.8
Maximum length of each paddle (l): 5.0 m
Maximum width of each paddle (b): 0.50 m
Kinematic viscosity : 1.003 x 10-6 m2/s
Dynamic viscosity of water : 1.002 x 10-3 N.s/m2
Freeboard: 0.50 m
Draw a net sketch of the designed tank (top and front view) clearly showing tank dimensions, paddle shaft position, paddle blade dimensions, water level, etc. Also mention paddle rotation speed and power requirement.
