Civil Engineering
GATE CE topic:sewage-system-design PYQs
Build your understanding with focused practice from past exam papers.
How to practice topic:sewage-system-design
Attempt a question, record the concept and assumptions, then check the available answer. Rework mistakes after revising the relevant concepts. Topic tags can overlap; review the question context.
Questions 1–5 of 5. Imported answers require independent review unless marked reviewed.
Question 17
Open questionCEMCQ1 markNeeds review
The bacteria mainly responsible for crown corrosion in a sewer is _____.
Your answerChoose one option.
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You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answerQuestion 62
Open questionCENAT2 marksNeeds review
A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is 250 m
, and the biomass concentration in the tank is 3000 mg/L. Analyses results showed that a biomass concentration of 100 mg/L is present in the treated effluent from the secondary sedimentation tank of the ASP. Sludge wastage from the system is at a rate of 5000 L/day with a biomass concentration of 1000 mg/L. The system is in steady state condition.The biological sludge residence time (BSRT) of the system (in days) is ______ (round off to one decimal place).
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Open questionCENAT1 markNeeds review
A river has a flow of 1000 million litres per day (MLD), BOD₅ 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 BOD₅ 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 ________.
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You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answerQuestion 54
Open questionCENAT2 marksNeeds review
A stream with a flow rate of 5 m
/s is having an ultimate BOD of 30 mg/litre. A wastewater discharge of 0.20 m
/s having BOD
of 500 mg/litre joins the stream at a location and instantaneously gets mixed up completely. The cross-sectional area of the stream is 40 m
which remains constant. BOD exertion rate constant is 0.3 per day (logarithm base e). The BOD (in mg/litre, round off to two decimal places) remaining at 3 km downstream from the mixing location, is _____.Log in to check the answer
You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answerQuestion 52
Open questionCENAT2 marksNeeds review
The ultimate BOD (
) of a wastewater sample is estimated as 87% of COD. The COD of this wastewater is 300 mg/L. Considering first order BOD reaction rate constant k (use natural log) = 0.23 per day and temperature coefficient
= 1.047, the BOD value (in mg/L, up to one decimal place) after three days of incubation at 27°C for this wastewater will be _____Log in to check the answer
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