LAISHA
Open Laisha

ICAR AICE-JRF/SRF Water & Wastewater Treatment: practice questions

ICAR AICE-JRF/SRF (PhD) — Environmental Sciences (subject 71) and Agricultural Meteorology (subject 60) · India · National Testing Agency for ICAR

Original practice questions written to the published syllabus · not past papers
10worked here, free
17written to this exam in this subject
12syllabus units

What this subject covers

Making water safe to drink and wastewater safe to release or reuse: unit operations, biological treatment, reactor kinetics, sludge, industrial effluents and zero liquid discharge. Farm-scale lagoons and manure systems are in the Agricultural Engineering subject waste-management-environmental-engg; this subject covers municipal and agro-industrial treatment to GATE ES depth.

In the exams: GATE ES Section 5 (whole section, numerical); ICAR AICE subject 71 Unit 4; UGC NET Unit 6; NCEES FE/PE Environmental

What ICAR AICE-JRF/SRF asks from it

ICAR AICE-JRF/SRF Environmental Sciences (Unit 4) and UGC NET Environmental Sciences (Unit 6)

Urban and industrial wastewater characteristics, treatment levels, activated sludge, anaerobic treatment and UASB, distillery, sugar and dairy effluents, CETPs and ZLD, sludge disposal.

Where the 17 questions fall

How our questions for ICAR AICE-JRF/SRF spread across the units of Water & Wastewater Treatment. Difficulty: 0 easy, 15 medium, 2 hard.

BOD kinetics2
Filtration, desalination and disinfection2
Sewers, storm sewers and appurtenances2
Anaerobic treatment and UASB reactors2
Agro-industrial effluents: dairy, sugar, distillery, food processing2
Water and wastewater quality parameters: BOD, COD, solids, nutrients1
Screening, sedimentation, coagulation and flocculation1
Primary, secondary and tertiary treatment1
Activated sludge, trickling filters and their design parameters1
Reactor kinetics: batch, CSTR and plug flow1
Sludge treatment and disposal1
Common effluent treatment plants, recycling and zero liquid discharge1

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Screening, sedimentation, coagulation and flocculation · medium

Which coagulation mechanism involves particles being enmeshed in precipitating metal hydroxide?

  1. Inter-particle bridging
  2. Sweep flocculation
  3. Double-layer compression
  4. Charge neutralisation
Answer and working

B. Sweep flocculation

Bridging uses polymers; compression and neutralisation act on surface charge.

2 · Filtration, desalination and disinfection · hard

Estimate the osmotic pressure of a 35 g/L NaCl solution at 25 degrees C using pi = i C R T (i = 2, R = 0.08314 L bar/(mol K)).

  1. 15 bar
  2. 30 bar
  3. 3.0 bar
  4. 867 bar
Answer and working

B. 30 bar

C = 35/58.44 = 0.599 mol/L; pi = 2 x 0.599 x 0.08314 x 298 = 30 bar. Omitting i halves it.

3 · Sewers, storm sewers and appurtenances · hard

Crown corrosion of concrete sewers is caused mainly by:

  1. Hydrogen sulphide oxidised to sulphuric acid by bacteria on the pipe crown
  2. Methane combustion inside the sewer during dry weather
  3. Chlorine residuals reacting with the cement at the invert of the pipe during wet weather
  4. Nitrate in sewage dissolving the steel reinforcement directly
Answer and working

A. Hydrogen sulphide oxidised to sulphuric acid by bacteria on the pipe crown

Anaerobic conditions produce H2S; aerobic bacteria on the crown form acid.

4 · Primary, secondary and tertiary treatment · medium

Enhanced biological phosphorus removal requires:

  1. Continuous aeration throughout the tank
  2. Anaerobic then aerobic zones
  3. Addition of nitrate to the raw influent
  4. Only anoxic conditions in every zone
Answer and working

B. Anaerobic then aerobic zones

Phosphate-accumulating organisms release P anaerobically and take up excess P aerobically.

5 · Activated sludge, trickling filters and their design parameters · medium

An SVI above about 150-200 mL/g usually indicates:

  1. Anaerobic digestion
  2. Complete nitrification
  3. Sludge bulking
  4. Excellent settling
Answer and working

C. Sludge bulking

Often caused by filamentous organisms. Bulking sludge settles poorly and can wash out of clarifiers.

6 · Anaerobic treatment and UASB reactors · medium

Who developed the UASB reactor, and where?

  1. Karl Imhoff, Germany
  2. Edward Ardern, England
  3. Gustaf de Laval, Sweden
  4. Gatze Lettinga, Netherlands
Answer and working

D. Gatze Lettinga, Netherlands

Ardern and Lockett developed activated sludge (1914); Imhoff the Imhoff tank.

7 · Reactor kinetics: batch, CSTR and plug flow · medium

Why is a CSTR more resistant to shock loads than a PFR?

  1. Inflow is immediately diluted in the tank
  2. It always has a shorter retention time
  3. It has no microorganisms that a shock could harm
  4. It operates at higher pressure than plug flow
Answer and working

A. Inflow is immediately diluted in the tank

Complete mixing dampens spikes in concentration or toxicity.

8 · Sludge treatment and disposal · medium

Typical solids retention time for mesophilic anaerobic sludge digesters is about:

  1. 1-2 days
  2. 1-2 years
  3. 1-2 hours
  4. 15-30 days
Answer and working

D. 15-30 days

Methanogens need long SRT. Short SRTs wash out methanogens and cause failure.

9 · Agro-industrial effluents: dairy, sugar, distillery, food processing · medium

What gives distillery spentwash its dark brown colour, which is hard to remove?

  1. Melanoidins and related colourants
  2. Chlorophyll from cane leaves
  3. Methylene blue added in processing
  4. Iron oxides from soil
Answer and working

A. Melanoidins and related colourants

Maillard-reaction melanoidins resist biological degradation.

10 · Agro-industrial effluents: dairy, sugar, distillery, food processing · medium

What is the usual first treatment step for distillery spentwash before further treatment in India?

  1. Direct discharge to rivers
  2. Chlorination at high doses
  3. Primary sedimentation alone
  4. Biomethanation with energy recovery
Answer and working

D. Biomethanation with energy recovery

Biomethanation recovers energy; ZLD routes follow.

Ten here, 17 in the app. The Laisha app has every practice question we have written to ICAR AICE-JRF/SRF in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.

Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.

Practise the full set in Laisha →

Read the subject

Water & Wastewater TreatmentThe full study manual, free ICAR AICE-JRF/SRFFormat, sections and how it has changed

More ICAR AICE-JRF/SRF practice

Agrobiodiversity & Genetic ResourcesAtmospheric Science & AgrometeorologyWetlands, Coastal Ecosystems & Blue CarbonEnvironmental & Agro-ecosystem ModellingBiodiversity Science & ConservationClimate Change Impacts on Agriculture & Food SystemsEnvironmental Monitoring & Instrumental AnalysisClimate Adaptation, Climate-Smart Agriculture & Disaster RiskEcosystem Services & Pollinators in Agricultural LandscapesRemote Sensing & GIS for Environmental MonitoringResearch Methods in Environmental & Sustainability ScienceEnergy, Environment & Agri-energy TransitionsLandscape Ecology, Protected Areas & Human-Wildlife InteractionsPesticides in the Environment: Fate, Risk & ReductionClimate Models, Scenarios & DownscalingAgroforestry & Trees on Farms for SustainabilityEcology & Ecosystem ScienceSoil Contamination, Toxicology & RemediationAgroecology: Principles & PracticePrinciples of Environmental ScienceSoil Science & Soil HealthLand Degradation, Desertification & Soil ConservationHydrology & Water Resources for Environmental ScientistsSoil Organic Carbon & Carbon Sequestration

Water & Wastewater Treatment for other exams

GATE · India

Ask Laisha about this

Opens Laisha's chat with your question ready to send. Sign in or start free.