Design a flocculation basin for water at 10°C flowing at Q = 49,200 m3/day for a typical process train in a drinking water treatment plant. The basin shall be a cross-flow, horizontal-shaft, paddlewheel type with an average velocity gradient of G = 26.7 sec−1, a detention time τ = 45 minutes, and a Gτ value of 50,000 to 100,000. Tapered flocculation shall be used in three compartments of equal depth in series. Compartments shall be separated by slotted, redwood baffle fences and have a level basin floor. G-values shall be 50, 20, and 10 sec−1 as the water passes through each compartment sequentially. The flocculation basin shall have a width of 27.43 m matching the adjacent sedimentation basin width. Paddle wheels shall have blades with a 150-mm width and a length of 3.05 m. Outer blades should clear the floor by 305 mm and be 305 mm below the water surface. Six blades shall be used per paddle wheel with a clear spacing of 305 mm between the blades. There shall be a clear spacing of 760 to 915 mm between the blades of adjacent paddle wheels, and an end wall clearance of 305 to 460 mm. Specifically determine: a. Basin dimensions to nearest 0.01 meters. b. Optional (zero points): Sketch a preliminary design for the paddle wheels – this is a mechanical engineering geometry problem, if you decide to give it a try do not spend too much time on it. c. Power input to the water in each compartment (watts), and the total power (watts). d. Range in rotational speed for each compartment using 1:4variable speed drives.
Design a flocculation basin for water at 10°C flowing at Q = 49,200 m3/day for a typical process
train in a drinking water treatment plant. The basin shall be a cross-flow, horizontal-shaft, paddlewheel type with an average velocity gradient of G = 26.7 sec−1, a detention time τ = 45 minutes,
and a Gτ value of 50,000 to 100,000. Tapered flocculation shall be used in three compartments of
equal depth in series. Compartments shall be separated by slotted, redwood baffle fences and
have a level basin floor. G-values shall be 50, 20, and 10 sec−1 as the water passes through each
compartment sequentially. The flocculation basin shall have a width of 27.43 m matching the
adjacent sedimentation basin width. Paddle wheels shall have blades with a 150-mm width and a
length of 3.05 m. Outer blades should clear the floor by 305 mm and be 305 mm below the water
surface. Six blades shall be used per paddle wheel with a clear spacing of 305 mm between the
blades. There shall be a clear spacing of 760 to 915 mm between the blades of adjacent paddle
wheels, and an end wall clearance of 305 to 460 mm. Specifically determine:
a. Basin dimensions to nearest 0.01 meters.
b. Optional (zero points): Sketch a preliminary design for the paddle wheels – this is a
mechanical engineering geometry problem, if you decide to give it a try do not spend too
much time on it.
c. Power input to the water in each compartment (watts), and the total power (watts).
d. Range in rotational speed for each compartment using 1:4variable speed drives.
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