1. A water treatment plant with a maximum daily flow of 4.4 m3/s is treating surface water with a minimum ambient temperature of -1°C (30°F). The water is coagulated with alum and the alum floc was measured to have a settling velocity of 1.6 m/h at 15°C (59°F). The settled water turbidity is expected to be <20 NTU prior to filtration. Design a horizontal rectangular sedimentation basin. Assume four basins for redundancy and to provide enough basins if the other basins need to be serviced or cleaned. The width of a basin is governed by the standard size of sludge removal equipment, and the standard maximum width of the chain-and-flight sludge collector is 6 m. So assume a basin width of 18 m. Assume a basin depth of 4 m. Prove that your basin design meets design criteria.
2. Draw a diagram explaining how the sedimentation basin you designed in Problem 1 will remove flocs or particles from the water.
a.Draw a diagram of the rectangular sedimentation basin designed in Problem 1. Be sure to clearly label the height, length, and width. Also clearly label the four zones of a sedimentation basin and briefly define each of the zones.
b.Once you have drawn and labeled the sedimentation basin, draw the path a small, fragile alum floc with a 1.6 m/h settling velocity would take in this basin if it entered at the top of the basin. Next to its path, label the settling velocity for this floc as "vF1" and provide its numerical value.
c.If an alum floc were to enter at the top of this basin with a settling velocity of 2.8 m/h, would it be removed from the basin? Why or why not? Draw the path of an alum floc with a 2.8 m/h settling velocity entering at the top of the basin on the sedimentation diagram you prepared. Next to its path, clearly label the settling velocity for this floc as "vF2" and provide its numerical value.
d.Under what conditions would an alum floc entering at the top of the basin not be removed from the basin (i.e. alum floc settling velocity)? Draw the path of an alum floc that would not be removed from the basin and describe its settling velocity in comparison to the settling velocity of the alum floc in Part A. Next to its path, label the settling velocity for this floc as "vNR".
e.How will the alum floc described in Part D need to enter the settling basin to be removed? Draw this path on the sedimentation diagram and clearly label the settling velocity as "vR".