CE-702-B Environmental Engineering-II - Nov 2023 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. 7 Marks
   aExplain the importance of micro-organism in biological treatment.
   How to answer

   • Role of bacteria, fungi, algae, protozoa in degradation
   • Aerobic vs anaerobic metabolism, BOD removal
   • Nutrient cycling, floc formation, stabilization
   • Examples in ASP, trickling filter, oxidation pond
2. 7 Marks
   bA rectangular grit chamber is designed to remove particles with a diameter of $0.2\, mm$, specific gravity $2.65$. Settling velocity for these particles has been found to range from $0.016$ to $0.022\, m/sec$, depending on their shape factor. A flow through velocity of $0.3\, m/sec$ will be maintained by proportioning weir. Determine the channel dimensions for a maximum wastewater flow of $10,000\, m^3/day$.
   How to answer

   • Settling velocity range $0.016$ to $0.022\, m/sec$, adopt critical value
   • Flow velocity $0.3\, m/sec$ maintained by weir
   • Compute cross-section, length, depth from detention and settling
   • Fix channel dimensions for $10,000\, m^3/day$
3. 8 Marks
   aExplain, with the help of neat sketch, the working of an oxidation ditch. Also give various configuration of oxidation ditches.
   How to answer

   • Oxidation ditch principle - extended aeration loop
   • Rotor/brush aeration, continuous circulation and oxygenation
   • Neat sketch of ditch with aerator
   • Configurations: single channel, multi-channel, carousel, Orbal
4. 6 Marks
   bCalculate kg of alum needed per day if alum dose is $28.6\, mg/l$ and the flow is $18$ Million litre/day.
   How to answer

   • Convert flow $18\, MLD$ to $L/day$
   • Alum dose $28.6\, mg/l$ to $kg/day$ : dose x flow
   • Compute $28.6 \times 18 \times 10^6 /10^6 = kg/day$
   • Result in $kg/day$
5. 7 Marks
   aCompare and contrast septic tank with Imhoff tank in scope, function and performance.
   How to answer

   • Two-storey vs single-storey concept
   • Sedimentation + digestion compartments
   • Scope, function, efficiency, maintenance comparison
   • Performance: effluent quality, sludge digestion
6. 7 Marks
   bDesign a suitable rectangular sedimentation tank (provided with mechanical cleaning equipment) for treating the sewage from a city, provided with an assured public water supply system, with a max. Daily demand of $12$ million litres per day. Assume $80\%$ of water supplied becomes wastewater, detention period is $2$ hours and velocity of flow is $0.3\, m/minute$ in the tank.
   How to answer

   • Design flow = 80% of 12 MLD = 9.6 MLD
   • Volume = Q x detention 2 hrs
   • Length from velocity 0.3 m/min, fix depth, width
   • Provide mechanical cleaning, freeboard, check surface loading
7. 7 Marks
   aWhat is meant by activated sludge? Describe with sketches the treatment of sewage by activated sludge process.
   How to answer

   • Definition of activated sludge - biological floc
   • Flow sheet: aeration tank, secondary clarifier, recycle
   • Sketches of process units
   • Function of aeration, F/M, sludge age
8. 7 Marks
   bCompute the diameter of a circular trickling filter for $250$ users. Dry weather flow is $120$ litres per capita per day. Rate of filtration of trickling filter may be taken as $10$ million litres per hectare/metre.
   How to answer

   • Population 250, DWF 120 lpcd -> total flow
   • Filter loading 10 ML/ha/m
   • Required filter area/volume, assume depth
   • Diameter of circular filter from area
9. 6 Marks
   aWrite a detailed note on ultrafiltration.
   How to answer

   • Definition and membrane pore range
   • Principle, pressure driven separation
   • Applications in wastewater reuse
   • Advantages, fouling and limitations
10. 8 Marks
    bDiscuss in brief biological nitrification denitrification for removal of nitrogen from wastewater.
    How to answer

    • Nitrification: ammonia to nitrate, Nitrosomonas/Nitrobacter
    • Denitrification: nitrate to nitrogen gas, anoxic conditions
    • Process conditions: DO, pH, carbon source
    • Flow schemes for N-removal
11. 6 Marks
    aWhat is photochemical smog and how is it formed?
    How to answer

    • Definition of photochemical smog
    • Precursors: NOx, VOCs, sunlight
    • Reactions forming ozone, PAN
    • Conditions and effects
12. 8 Marks
    bEnumerate the different major air pollutants, their characteristics, sources and health effects on human beings in a tabular form.
    How to answer

    • List major pollutants: SPM, SO2, NOx, CO, HC, O3
    • Columns: characteristics, sources, health effects
    • Tabular presentation
    • Key diseases and exposure routes
13. 7 Marks
    aWrite down the Gaussian distribution equation which is commonly used to predict the concentration of an air pollutant evolving from a source (factory) at any downwind point and the location of the maximum pollution.
    How to answer

    • Gaussian plume equation for $C(x,y,z)$
    • Meaning of dispersion coefficients $\sigma_y, \sigma_z$, wind speed, emission rate
    • Ground-level concentration form
    • Condition for maximum pollution location
14. 7 Marks
    bA coal fired $1000\, MW$ power plant is operating around $38\%$ efficiency. The ash and sulphur content in the coal used respectively are $35\%$ and $3\%$ and the calorific value of $21\, MJ$ per kg of coal. Find the emission rate of $SO_2$ from the plant.

    1. i)Difference between RSPM and TSPM
    2. ii)Factors affecting the dispersion of air pollutants
    3. iii)Environmental Lapse Rate (ELR) and Adiabatic Lapse Rate (ALR).
    4. iv)Primary and Secondary air pollutants
    5. v)Effect of air pollution on materials
    6. vi)Adsorption by activated carbon
    How to answer

    • Power 1000 MW at 38% efficiency -> heat input
    • Coal rate = heat / calorific value 21 MJ/kg
    • Sulphur 3% -> SO2 = 2 x S mass
    • Emission rate in kg/sec or tonnes/day
15. 14 Marks
    Write short notes on : (Any four)

    1. i)Difference between RSPM and TSPM
    2. ii)Factors affecting the dispersion of air pollutants
    3. iii)Environmental Lapse Rate (ELR) and Adiabatic Lapse Rate (ALR).
    4. iv)Primary and Secondary air pollutants
    5. v)Effect of air pollution on materials
    6. vi)Adsorption by activated carbon
    How to answer

    • Any four topics with definition and key points
    • Relevant examples, equations or diagrams
    • Environmental significance
    • Concise structured presentation for each note