Arrange the following process of wastewater treatment from top to bottom in chronological order:
1. Filtration
2. Coagulation
3. Sedimentation
4. Aeration
5. Softening
6. Chlorination
Select the answer using the code given below:
(a) 2-1-3-6-5-4
(b) 3-1-2-4-5-6
(c) 2-3-1-6-5-4
(d) 3-2-1-5-4-6
Explanation
Wastewater treatment occurs in three stages: Primary, Secondary, and Tertiary Treatment. Primary Treatment: This initial stage removes large impurities through sedimentation, coagulation, and filtration.
Sedimentation: Heavier particles settle in large tanks.
Coagulation: Fine particles clump together using coagulants like potash alum.
Filtration: Water passes through sand, coal, or fibrous materials to remove suspended matter and bacteria. The collected sludge is used as fertilizer or for methane gas production.
Secondary (Biological) Treatment: This step enhances water quality using microorganisms to break down organic matter.
Softening: Removes calcium and magnesium ions, making water soft.
Aeration: Oxygen is added to support bacterial decomposition of organic matter, reducing harmful gases like CO2 and sulfides.
Tertiary Treatment: This final step disinfects water, making it safe for use.
Chlorination: Kills bacteria but may create toxic byproducts.
Alternatives: UV radiation, ozone treatment, or reverse osmosis, though costlier, are safer options.
This systematic process ensures wastewater is treated efficiently before reuse or discharge into natural water bodies.
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