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Question
What is the key difference between primary and secondary sewage treatment?
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Solution
| Sr. No. |
Aspect |
Primary Sewage Treatment | Secondary Sewage Treatment |
| 1. | Nature of Process | Primary sewage treatment is a purely physical process of wastewater purification. | Secondary sewage treatment is a biological process driven by living microorganisms. |
| 2. | Target Material | This treatment focuses on removing floating debris and solid particles, such as grit. | This treatment focuses on degrading the dissolved organic matter in the water. |
| 3. | Mechanism | It achieves purification through sequential filtration and gravitational sedimentation. | It achieves purification using aerobic microbes that form mesh-like structures called flocs. |
| 4. | Impact on BOD | This stage causes little to no reduction in the Biochemical Oxygen Demand of sewage. | This stage significantly reduces the Biochemical Oxygen Demand of the effluent. |
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