What is the correct sequence for treatment of polluted surface water ?

1. Disinfection and fluoridation
2. Screening and mixing
3. Flocculation and sedimentation
4. Filtration and sludge processing

Select the correct answer using the code given below :

1-2-3-4

3-4-1-2

2-3-4-1

3-2-1-4

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CAPF – 2011

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The correct sequence for the typical treatment of polluted surface water from the given options is 2-3-4-1. This corresponds to Screening & mixing, followed by Flocculation & sedimentation, then Filtration & sludge processing, and finally Disinfection & fluoridation.

The standard sequence of surface water treatment involves removing large debris (screening), coagulating small particles (mixing, flocculation), settling the flocs (sedimentation), removing remaining suspended particles (filtration), and killing microorganisms (disinfection). Optional steps like fluoridation are added after disinfection. Sludge processing is a parallel or subsequent treatment for the solid waste generated.

The complete conventional water treatment process typically includes: 1. Screening (removes large debris), 2. Aeration (optional, adds oxygen), 3. Coagulation (chemicals added to neutralize charges), 4. Flocculation (gentle mixing to form larger flocs), 5. Sedimentation/Clarification (settling of flocs), 6. Filtration (removes smaller particles), 7. Disinfection (kills pathogens, e.g., chlorination, UV, ozonation), 8. pH adjustment (if needed), 9. Fluoridation (optional, adds fluoride for dental health), 10. Sludge treatment (handling waste from sedimentation and filtration). The provided options represent key stages in this overall process in sequential order.

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