Question: If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is________________?

• 1. 1 in 60
• 2. 1 in 100
• 3. 1 in 120
• 4. None of these

Question: The sewage treatment units in which anaerobic decomposition of organic matter is used, are called________________?

• 1. Imhoff tanks
• 2. Trickling filters
• 3. Sludge sedimentation tanks
• 4. None of these

Question: If the flame of a miner’s safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains_______________?

• 1. Hydrogen sulphide
• 2. Carbon dioxide
• 3. Methane
• 4. Oxygen

Question: If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is______________?

• 1. /2
• 2. /4
• 3. /3
• 4. D

Question: If q is the average sewage flow from a city of population P, the maximum sewage flow______________?

• 1. Q = (4 + )/(18 + ) q
• 2. Q = (18 + P)/(4 + ) q
• 3. Q = (18 + )/(4 + ) q
• 4. Q = (5 + )/((15 + ) q

Question: For a grit chamber, if the recommended velocity of flow is 0.2 m/sec and detention period is 2 minutes, the length of the tank, is__________________?

• 1. 16 m
• 2. 20 m
• 3. 24 m
• 4. 30 m

Question: The sewer that unloads the sewage at the point of treatment is called_________________?

• 1. Main sewer
• 2. Outfall sewer
• 3. Branch sewer
• 4. House sewer

Question: Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for__________________?

• 1. Unexpected large scale infiltration of stream water
• 2. Unexpected increase in the population
• 3. Under estimates of maximum and average flows
• 4. All of the above

Question: At the junction of sewers___________________?

• 1. Top of smaller sewer is kept lower
• 2. Top of larger sewer is kept lower
• 3. Tops of both the sewers are at the same level
• 4. None of these

Question: The normal values of over flow rates for sedimentation tanks using coagulant, ranges between__________________?

• 1. 25,000 to 35,000 litres/sqm/day
• 2. 40,000 to 50,000 litres/sqm/day
• 3. 50,000 to 60,000 litres/sqm/day
• 4. 80,000 to 100,000 litres/sqm/day