Environmental Science and Engineering
2026 · Paper 1
Take it one question at a time. Try an answer, then check your understanding.
Complete GATE ES 2026 Paper 1 overview, original pages and practice · Timed previous-paper practice
Questions 58–60 of 65. Imported answers require review unless explicitly marked reviewed.
Question 58
Open questionESNAT2 marksNeeds review
A sewage treatment plant employing activated sludge process is operated under the following conditions:
Wastewater flow rate into the aeration tank = 0.150 m
/sSoluble BOD
in the influent = 84 mg/LSoluble BOD
in the effluent = 11 mg/LMean cell residence time = 5 days
Total yield co-efficient = 0.5 kg of MLVS/kg BOD
removedDecay rate of microorganism = 0.050/day
The net waste activated sludge produced in the plant is _____ kg of VSS/day (rounded off to two decimal places).
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Open questionESNAT2 marksNeeds review
A continuous flow stirred tank reactor (CSTR) operates under a steady-state condition with a flow rate of 300 L per hour. The influent concentration of a substrate entering the reactor is 150 mg/L.
To give a treatment efficiency of 76% for the substrate that decays according to half-order kinetics with a rate constant of 0.05 (mg/L)
per hour, the required volume of the reactor is _____ m
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Open questionESNAT2 marksNeeds review
In a stack emission measurement at an industry, the stack cross-sectional area at 30 m height was divided into four equal sectors. The measured velocities and SO
concentrations through these sectors at this height are given in the table.The mean SO
concentration from the stack is _____ mg/m
(rounded off to two decimal places).Sector Number | Velocity (m/s) | SO Concentration (mg/m ) |
|---|---|---|
1 | 15 | 1000 |
2 | 17 | 1150 |
3 | 19 | 1250 |
4 | 21 | 1275 |
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