GATE 2017 CE (CE1) – Question 24

Water and Waste Water Quality and Treatment · Water quality standards, parameters and water quality index · 1 mark · Multiple choice

Wastewater rich in biodegradable organics enters a flowing river at S. If river-water aeration is slower than degradation of the organics, where is dissolved oxygen lowest?

At S.
Upstream of S.
Constant along the river.
Downstream of S.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (D) Downstream of S.

Explanation

Organic oxidation consumes oxygen as the polluted water travels downstream. When deoxygenation initially exceeds reaeration, an oxygen sag develops after the discharge point, reaching its minimum downstream before recovery. The minimum is not necessarily at the point of mixing. Thus D.

More Water quality standards, parameters and water quality index questions

GATE 2017 CE (CE1) Q64 – Two wastewater streams A and B have identical ultimate BOD and mix to form stream C.…
GATE 2026 CE (CE2) Q42 – The 2.4 ml of raw sewage is diluted to 240 ml. The Dissolved Oxygen (DO) of the diluted…
GATE 2025 CE (CE1) Q44 – MgCl 2 and CaSO 4 salts are added to 1 litre of distilled deionized water and mixed until…
GATE 2025 CE (CE2) Q49 – A compound has a general formula C aH bO cN d and molecular weight 187. A 935 mg/l…
GATE 2025 CE (CE2) Q61 – The analyses results of a water sample are given below. The non-carbonate hardness of the…
GATE 2023 CE (CE1) Q27 – Identify the waterborne diseases caused by viral pathogens:

All Water quality standards, parameters and water quality index questions →