CE-702-B Environmental Engineering-Ii - Dec 2025 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
   aA municipal wastewater has a $BOD_5$ of $200$ mg/l and $K_1$ (base e) is $0.39$ day$^{-1}$. Determine.

   1. i)The ultimate first stage BOD $L_0$ in mg/l.
   2. ii)The $y/L_0$ as a fraction and as a percent.
   How to answer

   • Define BOD exerted y = L0*(1-e^{-K1*t}) for base e
   • Compute L0 = BOD5 / (1-e^{-K1*5}) with K1=0.39/day
   • Calculate numerical value of L0 in mg/l ~233 mg/l
   • Compute ratio y/L0 = 1-e^{-K1*5} as fraction and percent
2. 7 Marks
   b(i) Design a primary settling tank for a 150 MLD sewage treatment plant. Assume all data required. (ii) Discuss the process involved in a sludge digester.
   How to answer

   • Assume surface overflow rate, detention time, depth, weir loading for primary settling tank
   • Compute flow 150 MLD, size diameter/volume, number of tanks, check criteria
   • Describe sludge digestion stages: hydrolysis, acidogenesis, methanogenesis
   • Mention gas production, volatile solids reduction, factors
3. 7 Marks
   a(i) Explain working of oxidation pond and symbiotic relationship in it. Also write its kinetic equations for plug flow and complete mix reactors. (ii) Define following terms: Mean Cell Residence Time (MCRT), F/M ratio, bulking of sludge.
   How to answer

   • Explain algae-bacterial symbiosis: O2 by algae, CO2/nutrients by bacteria
   • Describe working zones of oxidation pond
   • Write plug-flow kinetic equation
   • Write complete-mix kinetic equation and define MCRT, F/M, bulking
4. 7 Marks
   bWrite down the principle of oxidation of organic matter in trickling filter Using NRC equation; design the diameters of a two-stage trickling filter treating $8000$ m3/d wastewater at $200^{\circ}C$. Use the following given data: $BOD5$ of raw wastewater $= 300$ mg/l; Effluent $BOD5$ desired $= 30$ mg/l; depth of both the filter $= 1.9$m, Recirculation ratio $= 2:1$, BOD removal in primary sedimentation tank is $40\%$ and the efficiency of both the filters are equal. Also compute the BOD loadings on each filter.
   How to answer

   • Explain trickling filter biofilm oxidation principle
   • State NRC equation for efficiency
   • Apply two-stage with equal efficiency and recirculation correction
   • Compute diameters from volume/depth and BOD loadings on each filter
5. 7 Marks
   aDescribe the following terms along-with their significance:

   1. i)F/M ratio
   2. ii)MLSS
   3. iii)ML VSS
   4. iv)Hydraulic detention time
   5. v)Solid retention time
   6. vi)Volumetric Organic loading
   How to answer

   • Define F/M ratio and its control significance
   • Define MLSS, MLVSS and biomass indication
   • Define hydraulic detention time and solids retention time
   • Define volumetric organic loading and design significance
6. 7 Marks
   b(i) Explain the processes of nitrification and de-nitrification in biological nitrogen removal. (ii) Describe two major methods for phosphorus removal in wastewater treatment.
   How to answer

   • Write nitrification reactions: ammonia to nitrite to nitrate, aerobic conditions
   • Write denitrification: nitrate to N2 gas, anoxic conditions
   • Describe chemical precipitation and enhanced biological phosphorus removal
   • Compare requirements and sludge handling
7. 7 Marks
   aWhat are the main mechanisms by which activated carbon removes contaminants from water? Discuss factors affecting adsorption capacity.
   How to answer

   • State adsorption mechanisms: physical adsorption, chemisorption, ion exchange
   • Explain pore structure and surface area role
   • Discuss factors: pH, temperature, contact time, pollutant nature, dose
   • Mention regeneration and applications
8. 7 Marks
   bWhat is secondary treatment? Differentiate between preliminary treatment, primary treatment and secondary treatment? Also differentiate between attached growth system and suspended growth system.
   How to answer

   • Define secondary biological treatment objective
   • Differentiate preliminary vs primary vs secondary by function and units
   • Differentiate attached vs suspended growth with examples
   • Give examples: trickling filter vs activated sludge
9. 7 Marks
   aExplain the principle of operation of a diatomaceous earth filter. Why is a precoat necessary and what is the function of body-feed addition during filtration?
   How to answer

   • Explain diatomaceous earth as filter medium and septum support
   • Explain precoat formation and its necessity to prevent clogging
   • Explain body-feed to maintain porosity and extend run
   • Mention backwash and applications
10. 7 Marks
    bDefine air pollution. Explain the various primary and secondary sources of air pollutants with suitable examples.
    How to answer

    • Define air pollution
    • List primary sources: combustion, vehicles, industries with examples
    • List secondary pollutants: ozone, PAN, smog formation
    • Give suitable examples for each category
11. 7 Marks
    aDifferentiate ultrafiltration from microfiltration and reverse osmosis in terms of pore size, separation mechanism, and typical applications.
    How to answer

    • Compare pore sizes: micro ~0.1 micron, ultra ~0.01, RO dense membrane
    • Compare mechanism: sieving vs solution-diffusion
    • Compare operating pressure and rejection
    • Give typical water/wastewater applications
12. 7 Marks
    bWhat is photochemical smog? Explain its formation mechanism major constituents and harmful impacts on environment and human beings.
    How to answer

    • Define photochemical smog
    • Explain NOx + VOC + sunlight reactions forming ozone, PAN
    • List major constituents
    • Discuss health, vegetation, material and environmental impacts
13. 7 Marks
    aDescribe different plume behaviors (such as looping, coning, fanning, fumigation, lofting, trapping) with neat sketches and explain the meteorological conditions under which they occur.
    How to answer

    • Sketch looping, coning, fanning, fumigation, lofting, trapping plumes
    • Relate each to lapse rate and stability class
    • Explain inversion and mixing height role
    • Give meteorological conditions for each occurrence
14. 7 Marks
    bClassify air pollutants on the basis of their origin, physical state and chemical composition. Discuss their major characteristics.
    How to answer

    • Classify by origin, physical state, chemical composition with examples
    • Describe gases, particulates, aerosols characteristics
    • Discuss size, reactivity, persistence
    • Mention major sources and behavior
15. 7 Marks
    aDiscuss the effects of air pollution on:

    1. i)Human health
    2. ii)Vegetation
    3. iii)Building materials
    How to answer

    • Discuss respiratory, cardiovascular effects with pollutant examples
    • Discuss vegetation damage: chlorosis, necrosis, yield loss
    • Discuss building corrosion, soiling, acid rain effects
    • Give relevant examples in each case
16. 7 Marks
    bDerive the expression for the Gaussian Plume Model for continuous point source emission. State the assumptions made in the derivation and explain the significance of the parameters used.
    How to answer

    • State assumptions: steady wind, continuous source, Gaussian dispersion, no reaction
    • Derive from diffusion equation to Gaussian plume formula
    • Define dispersion coefficients sigma-y, sigma-z, effective stack height
    • Explain parameter significance for ground-level concentration