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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ev217

Select the correct statements about treatment of industrial effluents.

  1. AAcidic effluent can be neutralised with lime
  2. BHeavy metal ions can be removed as insoluble hydroxides or sulfides
  3. CBiological treatment with activated sludge lowers the biochemical oxygen demand (BOD)
  4. DAdding extra biodegradable organic matter lowers the BOD of the effluent

Answer: A, B, C

Lime neutralises acid (A), metal hydroxides and sulfides are insoluble (B) and microbes in activated sludge oxidise organic matter, lowering BOD (C). Adding organic matter raises BOD (D false).
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