GATE CE 2020 Set 1 — Question 35
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Environmental Engineering → Wastewater Treatment Processes → DO, BOD & COD
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Question
A river has a flow of 1000 million litres per day (MLD), of 5 mg/litre and Dissolved Oxygen (DO) level of 8 mg/litre before receiving the wastewater discharge at a location. For the existing environmental conditions, the saturation DO level is 10 mg/litre in the river. Wastewater discharge of 100 MLD with the of 200 mg/litre and DO level of 2 mg/litre falls at that location. Assuming complete mixing of wastewater and river water, the immediate DO deficit (in mg/litre, round off to two decimal places), is ___________.
Correct answer
2.45 to 2.65
Solution
Given:
River flow () = 1000 MLD, = 8 mg/L
Wastewater flow () = 100 MLD, = 2 mg/L
Saturation DO () = 10 mg/LStep 1: Calculate the DO of the mixture ():Step 2: Calculate the initial DO deficit ():Rounding off to two decimal places, the immediate DO deficit is 2.55 mg/L.
River flow () = 1000 MLD, = 8 mg/L
Wastewater flow () = 100 MLD, = 2 mg/L
Saturation DO () = 10 mg/LStep 1: Calculate the DO of the mixture ():Step 2: Calculate the initial DO deficit ():Rounding off to two decimal places, the immediate DO deficit is 2.55 mg/L.
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