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Zorluk: ZorPurification and Treatment of Water for Supply

A river water sample collected for a township supply system is found to contain fine suspended clay particles, objectionable taste caused by decomposing organic matter, and pathogenic bacteria, but has negligible dissolved calcium and magnesium salts. Which combination of chemical reagents must be utilized during the treatment process to render this water clean, odorless, and biologically safe?

  1. Potash alum, activated charcoal, and chlorineCevap
  2. B
    Slaked lime, washing soda, and chlorine
  3. C
    Potash alum, calcium chloride, and slaked lime
  4. D
    Sodium carbonate, activated charcoal, and boiling water

Cevap

Potash alum, activated charcoal, and chlorine form the correct combination of reagents for purifying soft, turbid, contaminated surface water for public distribution.
The correct answer combines potash alum, activated charcoal, and chlorine because each chemical directly addresses one of the identified raw water issues: potash alum coagulates colloidal clay particles into larger flocs during sedimentation; activated charcoal adsorbs dissolved organic matter causing unpleasant tastes and smells; and chlorine kills disease-causing bacteria during final disinfection.

Adım Adım Çözüm

1
Analyze the specific impurities present in the raw water sample
Impurities identified: fine suspended colloidal clay (requires coagulation), organic taste/odor compounds (requires adsorption), and pathogenic microbes (requires disinfection/sterilization). Hardness minerals are absent.
Different water treatment chemicals address distinct types of physical, chemical, and biological contamination.
2
Select the appropriate chemical reagent for colloidal suspension removal
Potash alum (KAl(SO4)2⋅12H2OKAl(SO_4)_2 \cdot 12H_2O) provides Al3+Al^{3+} ions to neutralize negative charges on clay particles, causing coagulation into settleable flocs.
Physical filtration alone cannot remove extremely fine colloidal clay without prior chemical coagulation.
3
Select the reagent for taste and odor removal
Activated charcoal (carbon) adsorbs volatile organic compounds responsible for objectionable smells and tastes.
Porous activated carbon has a very large surface area optimized for organic molecule adsorption.
4
Select the chemical required for biological safety
Chlorine (or chlorine compounds) acts as a powerful oxidizing disinfectant to destroy disease-causing bacteria.
Water for public distribution must undergo chemical sterilization to eliminate waterborne pathogens.

Anahtar Kavram

Municipal water treatment requires distinct functional reagents: coagulants (potash alum) for suspended particles, adsorbents (activated carbon) for taste/odor, and disinfectants (chlorine) for sterilization. Softening reagents (slaked lime/washing soda) are only needed when hardness ions (Ca2+Ca^{2+}, Mg2+Mg^{2+}) are present.
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Purification and Treatment of Water for Supply

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