Question

The purpose of biological treatment of waste water is to

• A. Increase BOD
• B. Decrease BOD
• C. Increase Sedimentation
• D. Reduce Sedimentation

Answer 1

The correct option is B

Decrease BOD

The correct option is B.

Explanation of the correct option:

1. The biological treatment of wastewater is a process that is carried out to degrade the microbes and the organic compounds that are present in sewage and to make it suitable to discharge into the water bodies.
2. The microbes and organic matter present in sewage take up a lot of oxygen content of the water bodies in order to decompose.
3. This leads to a shortage of oxygen for the plants and animals that thrive underwater.
4. In order to prevent this from happening, the organic matter and microbes are chemically treated in wastewater plants so that their decomposition is increased and when this water is released into other water bodies, it does not alter the oxygen content and decreases the biological oxygen demand.

Explanation of the incorrect options:

Option A:

1. Biological oxygen demand is the amount of oxygen that is required by the organic matter in wastewater to fully decompose.
2. If the BOD will be high, then it will lead to a shortage of oxygen for underwater plants and animals.

Option C:

1. Sedimentation is a part of the physical water treatment. It helps in the removal of the solid particles that are suspended throughout the wastewater.
2. It is not a part of the biological treatment of wastewater.

Option D:

Sedimentation is a part of the physical treatment of wastewater and not the biological treatment and hence its rate would not be affected.

Final answer: The purpose of biological treatment of wastewater is to decrease BOD.