Identify the correct sequence of treatment flow scheme for groundwater with low mineral content but presence of objectionable gases :
- ARaw Water – Aeration – Disinfectant – Disinfection Tank – SupplyCorrect
- BRaw Water – Disinfection Tank – Disinfectant – Aeration – Supply
- CRaw Water – Disinfectant – Disinfection Tank – Sedimentation Tank – Aeration – Supply
- DRaw Water – Disinfection Tank – Aeration – Sedimentation Tank – Supply
Solution
Concept
Treatment of groundwater containing dissolved gases
Step-by-step solution
1. Groundwater with low minerals needs no coagulation or sedimentation. 2. Dissolved gases (H₂S, CO₂) are removed by aeration first. 3. Disinfection follows, with chlorine added and contact time in a tank, before supply.
Explanation
The simplest scheme for clean groundwater with only gaseous impurities is aeration followed by disinfection.
Why the other options are wrong
The other sequences disinfect before removing the gases or include sedimentation that is unnecessary for low-mineral groundwater.
Shortcut
Groundwater with gases: aeration → disinfection.
Common mistake
Adding sedimentation.
Correct answer: A) Raw Water – Aeration – Disinfectant – Disinfection Tank – Supply