CE-702-B Environmental Engineering-II - Dec 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 6 Marks
   aWhat do you understand by unit operations and processes? Elaborate various types of unit operations used for waste water treatment.
   How to answer

   • Define unit operations vs unit processes with distinction (physical vs chemical/biological).
   • List physical unit operations: screening, grit removal, sedimentation, filtration, etc.
   • List chemical/biological processes: coagulation, disinfection, activated sludge, trickling filter, etc.
   • Elaborate role of each in wastewater treatment train.
2. 8 Marks
   bExplain the various types of settling for waste water treatment.
   How to answer

   • Define settling/sedimentation in wastewater treatment.
   • Explain types: discrete, flocculent, hindered/zone, compression settling.
   • Give governing principle and example of each (grit chamber, primary clarifier, secondary clarifier, sludge thickener).
   • Mention Stokes law and factors affecting settling.
3. 6 Marks
   aExplain with the help of neat sketch, the working of an oxidation ditch.
   How to answer

   • Define oxidation ditch as extended aeration looped channel.
   • Describe components: oval ditch, brush/botor aerator, continuous circulation.
   • Explain working: aeration, circulation, secondary settling, sludge recirculation.
   • Provide neat labelled sketch of plan and section.
4. 8 Marks
   bWrite a note on racks and screens. How do you determine head loss through bar screen?
   How to answer

   • Define racks (coarse bar screens) and screens (fine/medium) and purpose.
   • Describe types, cleaning, placement at headworks.
   • State head loss formula for bar screen (Kirschmer/Metcalf-Eddy equation).
   • Explain procedure to determine head loss with velocity and clogging factor.
5. 6 Marks
   aCompare and contrast septic tank with Imhoff tank in scope, function and performance.
   How to answer

   • Define septic tank and Imhoff tank with sketches.
   • Compare scope: capacity, single vs community, two-storey digestion.
   • Compare function: sedimentation + digestion combined vs separated.
   • Compare performance: effluent quality, sludge digestion, maintenance.
6. 8 Marks
   bThe sewage flows from a preliminary settling tank to a standard rate trickling filter at a rate of 5 million litres per day having a 5 day BOD of $150 \text{ mg/lit}$. Determine the depth and the volume of the filter, adopting a surface loading of $2500 \text{ lit/m}^2\text{/day}$ and an organic loading of $165 \text{ g/m}^3\text{/day}$. Also determine the efficiency of the filter unit, using NRC formula.
   How to answer

   • Compute surface area from hydraulic loading: Area = Q / surface loading.
   • Compute volume from organic loading: Volume = total BOD load / organic loading, then depth = Volume/Area.
   • Check standard depth and adjust diameter/volume.
   • Apply NRC formula for efficiency of standard rate trickling filter.
7. 6 Marks
   aWhat is meant by activated sludge? Describe with sketches the treatment of sewage by activated sludge process.
   How to answer

   • Define activated sludge (biological floc with active microorganisms).
   • Describe flow sheet: aeration tank, secondary clarifier, sludge recirculation and wasting.
   • Explain role of MLSS, F/M, aeration and microbial degradation.
   • Provide neat sketches of process units.
8. 8 Marks
   bExplain how you determine the oxygen requirements in an activated sludge process.
   How to answer

   • State oxygen demand components: carbonaceous BOD removal + endogenous respiration + nitrification.
   • Give mass balance formula using influent/effluent BOD, MLSS, sludge wastage.
   • Explain steps with design parameters (BOD load, cell yield, oxygen per kg BOD).
   • Mention aerator capacity and safety factor.
9. 6 Marks
   aWhy it is necessary to remove nitrogen from the secondary plant effluents mention different methods used for this.
   How to answer

   • Explain eutrophication, algal growth and oxygen depletion due to nitrogen.
   • Mention ammonia toxicity and need for nutrient removal standards.
   • List methods: nitrification-denitrification, BNR, breakpoint chlorination, ion exchange.
   • Brief working of each biological/chemical method.
10. 8 Marks
    bWhat do you understand by Advanced Wastewater Treatment? How it is different from the conventional treatment? Give, in a tabular form, important AWT processes.
    How to answer

    • Define Advanced Wastewater Treatment (tertiary/polishing).
    • Differentiate from conventional primary+secondary on objective and pollutants removed.
    • Present tabular list of important AWT processes (filtration, carbon adsorption, RO, nutrient removal).
    • Mention application for reuse.
11. 6 Marks
    aWhat do you understand by 'aerosols'? Describe various types of aerosols along with their characteristics.
    How to answer

    • Define aerosols (suspended solid/liquid particles in air).
    • Classify types: dust, fume, smoke, mist, fog, haze with size range.
    • Describe characteristics: size, settling, visibility, health effects.
    • Give sources/examples for each type.
12. 8 Marks
    bExplain the sources and characteristics of the following air pollutants?

    1. i)Sulphur dioxide
    2. ii)Hydrogen sulphide
    How to answer

    • Identify sources of SO2 (fuel combustion, smelters) and H2S (sewage, refineries).
    • Describe physical/chemical characteristics and ambient behaviour.
    • Explain health and environmental effects (acid rain, odour).
    • Mention control/measurement aspects.
13. 6 Marks
    aList out meteorological factors influencing air pollution.
    How to answer

    • Define role of meteorology in dispersion/dilution.
    • List factors: wind speed/direction, temperature lapse, stability, mixing height.
    • Include humidity, precipitation, solar radiation, topography.
    • Briefly state influence of each on air pollution concentration.
14. 8 Marks
    bA coal fired 800 MW power plant generates daily huge quantum of flyash, bottom slurries, besides particulate matter present in the burnt coal. Estimate the quantum of bottom ash, flyash and particulates generated daily by the plant. Also, suggest eco-friendly method of disposal of the flyash and bottom ash. Following information available: Calorific value of the coal (ash content 38%) burnt $21 \text{ MJ/kg}$; $60\%$ of ash discharged as flyash, and $75\%$ of flyash and $90\%$ of the bottom ash generated may be recovered; overall efficiency of the plant is $40\%$.
    How to answer

    • Compute daily coal consumption from power output, calorific value and efficiency.
    • Compute total ash = coal x 38%, split into flyash 60% and bottom ash 40%.
    • Estimate recoverable fractions: 75% of flyash, 90% of bottom ash; particulates balance.
    • Suggest eco-friendly disposal/utilization: bricks, cement, road fill, mine filling.
15. 14 Marks
    Write short notes on (any four)

    1. i)Photochemical smog
    2. ii)Temperature lapse rate
    3. iii)Gaussian Plume Model
    4. iv)Diatomaceous earth filter
    5. v)Ultrafiltration
    6. vi)Ammonia stripping method
    How to answer

    • For each of any four topics: give definition/principle.
    • Explain mechanism with equation/sketch where applicable.
    • Mention application in water/air treatment.
    • Mention significance/limitations.