Which of the following statements is INCORRECT?

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SSC JE Civil 07 Jun 2024 Shift 1 Official Paper - 1
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  1. In plain sedimentation tanks, the removal of particles is independent of the depth of the sedimentation tank.
  2. Filters purify water through the following four different processes: mechanical straining, flocculation and sedimentation, biological metabolism and electrolyte charges charging.
  3. Flocculation is a chemical technique that is directed towards the destabilisation of charged particles and the coagulation promotes the agglomeration of stabilised particles.
  4. Activated carbon is a de-chlorinating agent.

Answer (Detailed Solution Below)

Option 3 : Flocculation is a chemical technique that is directed towards the destabilisation of charged particles and the coagulation promotes the agglomeration of stabilised particles.
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Detailed Solution

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Explanation:

Evaluating the Statements:

Statement 1: In plain sedimentation tanks, the removal of particles is independent of the depth of the sedimentation tank.

From the provided image, it is clear that:

  • The settling velocity of the particle is given by \(\frac{D}{L} \times \frac{Q}{BD} = \frac{Q}{LB}\).
  • This implies that particles with a settling velocity greater than the overflow rate \(\frac{Q}{LB}\) will settle in the sedimentation basin.
  • It states: "Settling efficiency is independent of depth, as per the theory."

Therefore, this statement is correct.

Statement 2: Filters purify water through the following four different processes: mechanical straining, flocculation and sedimentation, biological metabolism and electrolyte charges charging.

  • This statement is correct. Filters utilize these processes for water purification.

Statement 3: Flocculation is a chemical technique that is directed towards the destabilization of charged particles and the coagulation promotes the agglomeration of stabilized particles.

  • This statement is incorrect. The correct relationship is:
    • Coagulation is the process of destabilizing charged particles.
    • Flocculation involves the agglomeration of these destabilized particles into larger clumps.

Statement 4: Activated carbon is a de-chlorinating agent.

  • This statement is correct. Activated carbon is used to remove chlorine from water.

 

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