Question

In which of the following wastewater treatment units is organic matter destroyed and stabilized by anaerobic bacteria ?

A. Sedimentation tank

B. Trickling filter

C. Oxidation pond

D. Septic tank

Answer: Option D – Septic tank

Explanation:

Septic tank:

Septic Tank is used in wastewater treatment in which a sudge is directly discharged and organic matterch destroyed and stabilized by anaerobic bacteria.

Activated sludge process:

The essential features of the activated sludge process are an aeration stage, solids-liquid separation following aeration, and a sludge recycle system.
Wastewater after primary treatment enters an aeration tank where the organic matter is brought into intimate contact with the sludge from the secondary clarifier.
It requires less space and requires less time for wastewater treatment.
It requires skilled supervision.

1)
Method:
Rotating biological contactor

Contact Mechanism:
Attached growth

Decomposition:
Aerobic

2)
Method:
Trickling filter

Contact Mechanism:
Attached growth

Decomposition:
Aerobic

3)
Method:
Activated sludge process

Contact Mechanism:
Suspended growth

Decomposition:
Aerobic

4)
Method:
Oxidation pond

Contact Mechanism:
Suspended growth

Decomposition:
Aerobic

5)
Method:
Septic tank

Contact Mechanism:
Suspended growth

Decomposition:
Anaerobic

6)
Method:
Imhoff tank

Contact Mechanism:
Suspended growth

Decomposition:
Anaerobic

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