Environmental Engineering Reference
In-Depth Information
12.52 What is the most critical criterion for determining when a mixed
media filter should be backwashed?
12.53 What is grit? Give three examples of materials that are consid-
ered to be grit.
12.54 The plant has three channels in service. Each channel is 2 ft
wide and has a water depth of 4 ft. What is the velocity in the
channel when the flow rate is 9.0 MGD?
12.55 What is the concentration of hydrogen ions at a pH of 7?
12.56 How are the results of a membrane filter test reported?
12.57 A membrane filter test for fecal coliform reveals blue, green,
black, and yellow dots. Which ones should be counted?
12.58 Where should chlorine vents be placed?
12.59 The grit from the aerated grit channel has a strong hydrogen
sulfide odor upon standing in a storage container. What does
this indicate, and what action should be taken to correct the
problem?
12.60 What is the purpose of primary treatment?
12.61 What is the purpose of the settling tank in the secondary or bio-
logical treatment process?
12.62 Belt filter presses are operated as a
process.
12.63 An incubator for the BOD test should be controlled at a tempera-
ture of
°C.
12.64 The circular settling tank is 80 ft in diameter and has a depth of
12 ft. The effluent weir extends around the circumference of the
tank. The flow rate is 2.20 MGD. What is the detention time in
hours, surface loading rate in gpd/ft
2
, and weir overflow rate in
gpd/ft?
Use the following information for Questions 12.65 through 12.68:
Plant effluent
Flow = 0.40 MGD
Suspended solids = 370 mg/L
BOD = 380 mg/L
Town population
= 2850 people
Industrial construction
Flow = 0.039 MGD
Suspended solids = 650 mg/L
BOD = 970 mg/L
Pond
Length = 1400 ft
Width = 1100 ft
Operating depth = 4.1 ft
