D61 QUIZ OF THE DAY

Which part of a deep manhole forms its lower portion and has a minimum height of 1.8m?

• Access shaft
• Working chamber
• Sidewalls
• Bottom invert

Answer explanation

The working chamber is the lower portion of a deep manhole, with a height not less than 1.8m.

Which structure connects high level branch sewers to low level main sewers?

• Manhole
• Junction chamber
• Drop manhole
• Flushing tank

Answer explanation

Drop manholes are used when there's a vertical level difference of more than 0.5m between sewers.

Catch basins are constructed to:

• Store grease and oil
• Trap grit and admit rainwater
• Measure sewage velocity
• Divert storm water

Answer explanation

Catch basins eliminate silt and grit before allowing rainwater into the combined sewer system.

Which device diverts excess stormwater to natural streams?

• Storm regulator
• Flushing tank
• Cleanout
• Grease trap

Answer explanation

Storm regulators prevent overloading of sewer lines by diverting excess flow to natural water bodies.

Which type of sewer is constructed under obstructions like rivers and railways?

• Outfall sewer
• Inverted siphon
• Relief sewer
• Storm sewer

Answer explanation

Inverted siphons are used to convey sewage under obstructions where normal gravity flow is not possible.

Assertion (A): Eutrophication leads to increased algal growth. Reason (R): Phosphates and nitrates in sewage enhance lake productivity.

• Both A and R are true, and R is the correct explanation of A
• Both A and R are true, but R is not the correct explanation of A
• A is true, R is false
• A is false, R is true

Answer explanation

Excessive nutrients from sewage cause eutrophication, promoting algal blooms.

Which chamber facilitates the junction of two or more sewers at angles less than 30°?

• Drop chamber
• Catch basin
• Junction chamber
• Manhole

Answer explanation

Junction chambers are provided where horizontal angles between sewers are less than 30°.

What is the function of a grease and oil trap in sewer systems?

• Remove sediments
• Store stormwater
• Exclude grease and oil
• Prevent gas escape

Answer explanation

Grease and oil traps remove floating oils and greases near sources like kitchens and garages.

Which physical force helps reduce concentration of organic matter in a polluted river?

• Oxidation
• Sedimentation
• Sunlight
• Dilution and dispersion

Answer explanation

Dilution and dispersion lower the concentration of impurities by spreading them across water volume.

Which zone is characterized by zero dissolved oxygen and gas evolution like H₂S and CH₄?

• Zone of degradation
• Zone of active decomposition
• Zone of recovery
• Clear water zone

Answer explanation

In the zone of active decomposition, anaerobic bacteria generate gases due to lack of DO.