Which of the following statements about the secondary treatment of sewage is INCORRECT? 

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SSC JE Civil 06 Jun 2024 Shift 3 Official Paper - 1
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  1. Oxidation of organic matter occurs in trickling filters under aerobic conditions.
  2. Secondary treatment methods are broadly divided into filtration and activated sludge process. 
  3. Activated sludge is biologically active. 
  4. Primary treatment of sewage is not essential for efficient working of contact beds. 

Answer (Detailed Solution Below)

Option 4 : Primary treatment of sewage is not essential for efficient working of contact beds. 
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Detailed Solution

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Oxidation of organic matter occurs in trickling filters under aerobic conditions:

  • This statement is correct.
  • Trickling filters use a bed of media where microorganisms form a biofilm that degrades organic matter.
  • The process occurs under aerobic conditions, meaning that oxygen is required for the microorganisms to function effectively.

Secondary treatment methods are broadly divided into filtration and activated sludge process:

  • This statement is correct.
  • Secondary decompostion consist of biological decompostion of organic matter
  • Treatment reactors in which the organic matter is decomposed by aerobic bacteria are known as aerobic biological units and may consist of filters, aeration tank, oxidation pond and aerated laggons
  • Treatment units in which organic matter is destroyed and stabilized anaerobically are anerobic units and consist of septic tank, anaerobic lagoons, imoff tank.

Activated sludge is biologically active:

  • This statement is correct.
  • The activated sludge process relies on a mixture of microorganisms that biologically degrade organic matter in wastewater.
  • These microorganisms form a biologically active sludge that treats the wastewater.

Primary treatment of sewage is not essential for efficient working of contact beds:

  • This statement is incorrect.
  • Primary treatment removes large solids and particulate matter from sewage.
  • This step is essential for the efficient operation of secondary treatment systems like contact beds, preventing clogging and overloading.
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