GATE CE · 2026 · CE
Question 63: Water and Waste Water Quality and Treatment
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Question 63
CENAT2 marksNeeds review
An Activated Sludge Process (ASP) has an inlet wastewater flowrate of 2000 m³/day with a Biochemical Oxygen Demand (BOD) concentration of 250 mg/l. It produces treated wastewater containing 20 mg/l BOD. The aeration tank has a working volume of 600 m³ and a biomass concentration of 3000 mg/l. Biological Sludge Residence Time (BSRT) of the system is 6 days. The influent wastewater and the treated effluent from the system have negligible concentrations of biomass. The sludge recycle line from the bottom of the Secondary Sedimentation Tank (SST) to the inlet of the aeration tank has a flowrate of 600 m³/day.
To maintain equilibrium, the flowrate (in m³/day) of sludge that is to be wasted from the system is _____ (in integer).
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2026CE
GATE CE 2026 · Paper 1
Civil Engineering · Original paper archive
- Section
- Civil Engineering
- Question type
- Numerical answer (NAT)
- Marks
- 2 marks
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