Haryana PSC AE 2010
⭕ A. Rainfall is concentrated in a season of the year and DWF fluctuates from day to day
⭕ B. Rainfall is scattered throughout the year and DWF is too small compared to storm water
⭕ C. Rainfall is distributed throughout the year such that it is ≤ 10× DWF
⭕ D. City is on steep rocky slopes
📚 Explanation:
A combined sewer system carries both storm water and domestic wastewater in the same sewer.
✔ It is preferred where:
🔹 Rainfall is moderate and spread throughout the year
🔹 Stormwater flow is not extremely high
🔹 Rainfall ≤ 10 × Dry Weather Flow (DWF)
This makes the sewer design economical and avoids excessively large sewer sizes.
A combined sewer system carries both storm water and domestic wastewater in the same sewer.
✔ It is preferred where:
🔹 Rainfall is moderate and spread throughout the year
🔹 Stormwater flow is not extremely high
🔹 Rainfall ≤ 10 × Dry Weather Flow (DWF)
This makes the sewer design economical and avoids excessively large sewer sizes.
👉 Therefore, the correct answer is: C. Rainfall is distributed throughout the year such that it is ≤ 10× DWF
Key Points on Combined Sewer System:
- ✔ Best suited where rainfall is moderate and well distributed.
- ✔ Economical when stormwater ≈ domestic sewage flows.
- ❌ Not suitable in areas with very high rainfall.
- ❌ Not recommended on steep rocky terrains.
