Civil Engineering
GATE CE topic:water-and-wastewater-treatment PYQs
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How to practice topic:water-and-wastewater-treatment
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 1–10 of 81. Imported answers require independent review unless marked reviewed.
Question 21
Open questionCEMCQ1 markNeeds review
A rapid sand filter bed of depth 0.8 m has 40 % porosity during service cycle. It is recommended that during backwash operation, the expanded filter bed should have 70 % porosity. The uniform expanded depth (in m) of the filter bed during backwash is
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Open questionCEMCQ1 markNeeds review
The settling velocity of inorganic particles in the sedimentation tank of a water treatment plant is governed by
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Open questionCEMSQ1 markNeeds review
Which of the following components is/are NOT removed in the secondary treatment of sewage?
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Open questionCEMCQ1 markNeeds review
One-third of the solid matter in a sludge containing 90 % water is composed of fixed mineral solids with specific gravity 2.5, and two-third is composed of volatile solids with specific gravity 1.0.
Specific gravity of all solids lies between
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The grown algae are useful in the operation of
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Open questionCEMCQ2 marksNeeds review
The 2.4 ml of raw sewage is diluted to 240 ml. The Dissolved Oxygen (DO) of the diluted sample at the beginning of Biochemical Oxygen Demand (BOD) test was 8 mg/l and it was 6 mg/l after 5-day incubation at 20 °C.
The BOD₅ (in mg/l) of the raw sewage is
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Open questionCEMCQ2 marksNeeds review
The average sewage from a city is 90 million litres per day and the average 5-day Biochemical Oxygen Demand (BOD₅) is 300 mg/l. Average standard BOD₅ of the domestic sewage is 0.08 kg/day/person. The population equivalent of the city 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 63
Open questionCENAT2 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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Open questionCENAT2 marksNeeds review
The analysis of major cations and anions in a water sample collected from a city’s water supply is given below. Ions present in minor concentrations are not given.
Anions | | | | |
|---|---|---|---|---|
Concentration (mM) | 1.5 | 0.5 | 1.0 | 0.01 |
Cations | | | | |
Concentration (mM) | 2 | 0.5 | 0.25 | 0.02 |
(in %) present in the total free chlorine in the water is ____ (rounded off to the nearest integer).Log in to check the answer
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Open questionCENAT2 marksNeeds review
Anaerobic bacteria are being utilized for the destruction of biodegradable organic content of wastewater measured in terms of Chemical Oxygen Demand (COD). The yield coefficient (Y) is 0.06 gram Volatile Suspended Solids (VSS) per gram of COD. Bacterial biomass forms the sludge during the process. The proximate chemical formula of anaerobic bacteria is C₆H₇NO₂.
The COD (in %) converted into bacterial biomass is ______ (rounded off to the nearest integer).
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