This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Oxidation Ditch”.
1. Oxidation ditch is an extended activated sludge process.
a) True
b) False
View Answer
Explanation: Oxidation ditch is an extended aeration activated sludge process. An oxidation ditch is a large holding tank in a continuous ditch with an oval shape similar to that of a racetrack. The ditch is built on the surface of the ground and is lined with an impermeable lining.
2. What is the shape of the oxidation ditch?
a) Square
b) Rectangular
c) Circular
d) Oval
View Answer
Explanation: An oxidation ditch is a large holding tank in a continuous ditch with an oval shape similar to that of a racetrack. The ditch is built on the surface of the ground and is lined with an impermeable lining.
3. The ditch is lined by _______ layer.
a) Brick
b) Cement
c) Permeable
d) Impermeable
View Answer
Explanation: The ditch is built on the surface of the ground and is lined with an impermeable lining. This allows the waste water to have plenty of exposure to the open air for the diffusion of oxygen.
4. What is the range of liquid depth in oxidation ditches?
a) 0.2-0.3 m
b) 0.3-0.5 m
c) 0.5-0.9 m
d) 0.9-1.5 m
View Answer
Explanation: The liquid depth in the ditches is very shallow, 0.9 to 1.5 m, which helps to prevent anaerobic conditions from occurring at the bottom of the ditch.
5. Anaerobic conditions occur at the bottom of the ditches.
a) True
b) False
View Answer
Explanation: The liquid depth in the ditches is very shallow, 0.9 to 1.5 m, which helps to prevent anaerobic conditions from occurring at the bottom of the ditch.
6. What is the range of MLSS concentration in oxidation ditch?
a) 500-1000 mg/L
b) 1000-2000 mg/L
c) 2000-4000 mg/L
d) 3000-5000 mg/L
View Answer
Explanation: The MLSS concentration in the oxidation ditch generally ranges from 3,000 mg/L to 5,000 mg/L. This is dependent upon the surface area provided for sedimentation, the rate of sludge return and the aeration process.
7. Which of the following is MLSS concentration not dependant upon?
a) Surface area of sedimentation
b) Rate of return sludge
c) Aeration process
d) Number of bar screens
View Answer
Explanation: The surface area provided for sedimentation, the rate of sludge return and the aeration process affects MLSS concentration. The MLSS concentration in the oxidation ditch generally ranges from 3,000 mg/L to 5,000 mg/L.
8. Oxidation ditch uses ______ to remove biodegradable organics.
a) Long SRTs
b) Short SRTs
c) pH
d) chemicals
View Answer
Explanation: Long solids retention times (SRTs) are used by oxidation ditch to remove biodegradable organics. The typical oxidation ditch is equipped with aeration rotors or brushes that provide aeration and circulation.
9. What is the velocity of wastewater within the ditch?
a) 0.5 ft/s
b) 0.7 ft/s
c) 5 ft/s
d) 2 ft/s
View Answer
Explanation: The velocity of the wastewater within the ditch is 1 to 2ft/s. This process may be adaptable to the fluctuations in flows and loadings associated with recreation area wastewater production.
10. Which of the following process is not adopted in oxidation ditches?
a) Adsorption
b) Desorption
c) Oxidation
d) Decomposition
View Answer
Explanation: An oxidation ditch is a large circular basin equipped with aerators that are used to remove organic matter and pollutants from sewage through the processes of adsorption, oxidation and decomposition.
Sanfoundry Global Education & Learning Series – Waste Water Engineering.
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