Environmental Engineering Reference
In-Depth Information
6.6 ChaPTer revieW QuesTions
6.1
What is the purpose of sedimentation?
6.2
The sludge pump operates 20 minutes every 3 hours. The pump
delivers 70 gpm. If the sludge is 5.0% solids and has a volatile
matter content of 64%, how many pounds of volatile solids are
removed from the settling tank each day?
6.3
A circular settling tank is 90 ft in diameter and has a depth of
10 ft. The flow rate is 2.5 MGD. What are the detention time in
hours, surface loading rate in gpd/ft
2
, and weir overflow rate in
gpd/foot?
6.4
What is the recommended procedure to follow when removing
sludge intermittently from a primary settling tank?
6.5
Why is there normally a baffle at the effluent end of the primary
settling tank?
6.6
How much of the settleable solids are removed by primary
settling?
6.7
What is an average detention time in a primary clarifier?
6.8
A settling tank 90 ft long, 25 ft wide, and 10 ft deep receives a flow
rate of 1.6 MGD. What is the surface overflow rate in gpd/ft
2
?
6.9
A settling tank with a total weir length of 90 ft receives a flow
rate of 1.35 MGD. What is the weir overflow rate in gpd/ft?
6.10 A wastewater treatment plant has 6 primary tanks. Each tank
is 90 ft long and 15 ft wide with a side water depth of 10 ft and
a total weir length of 80 ft. The flow rate to the plant is 6 MGD.
Three tanks are currently in service. Calculate the detention
time in minutes, the surface overflow rate in gpd/ft
2
, and the weir
overflow rate in gpd/ft.
6.11 A primary settling tank is 80 ft in diameter and 10 ft deep. What
is the detention time when the flow is 3.25 MGD? Your answer
should be in hours.
6.12 A circular settling tank is 90 ft in diameter and has a depth of
10 ft. The effluent weir extends around the circumference of the
tank. The flow rate is 3.70 MGD. What is the detention time in
hours, surface loading rate in gpd/ft
2
, and weir overflow rate in
gpd/ft?
6.13 An underflow pump operates 30 minutes every 3 hours. The pump
delivers 80 gpm. If an underflow is 5.0% solids and has a volatile
matter content of 66%, how many pounds of volatile solids are
removed from the settling tank each day?
6.14 A circular settling tank is 80 ft in diameter and has a depth of
9 ft. The effluent weir extends around the circumference of the
tank. The flow rate is 2.60 MGD. What are the detention time in
hours, surface loading rate in gpd/ft
2
, and weir overflow rate in
gpd/ft?
