MCQ Environmental Engineering

MCQ Environmental Engineering

Topics: Water supply & treatment · Wastewater · Air pollution · Municipal solid waste · Noise pollution

Q1. Per capita water demand for domestic use in India (typical design value) is of the order of:

50–80 lpcd 135–200 lpcd 300–400 lpcd 20 lpcd

Q2. The most important parameter for bacteriological quality of drinking water is:

Hardness Coliform / E. coli count Turbidity only Colour

Q3. Residual chlorine in treated water at the consumer end is typically maintained around:

0.1–0.2 mg/L 2–3 mg/L 10 mg/L Zero

Q4. Hardness in water is mainly due to:

Ca and Mg salts NaCl Dissolved oxygen Chlorine

Q5. The correct sequence of conventional surface-water treatment is:

Filtration → coagulation → disinfection Coagulation–flocculation → sedimentation → filtration → disinfection Disinfection → sedimentation → filtration Aeration only

Q6. Alum is added in water treatment primarily as a:

Disinfectant Coagulant Softener only Fluoridating agent

Q7. Rapid sand filters are cleaned by:

Scraping the top layer only Backwashing with water (and often air scour) Boiling Chlorine only

Q8. Chlorination is mainly done for:

Removing hardness Disinfection Removing iron only Increasing pH

Q9. Average domestic sewage generation is often taken as about:

10% of water supply 80% of water supply 150% of water supply Equal to rainfall

Q10. BOD₅ represents:

Biochemical oxygen demand over 5 days at 20°C Chemical oxygen demand Dissolved oxygen only None

Q11. COD is generally:

Less than BOD Greater than BOD for the same sample Always equal to BOD Independent of organics

Q12. Total solids in wastewater include:

Only settleable solids Suspended + dissolved solids Only dissolved solids Only grit

Q13. Primary treatment of sewage mainly removes:

Dissolved organics Settleable suspended solids and floating matter All pathogens Nutrients only

Q14. Activated sludge process is a type of:

Primary treatment Secondary (biological) treatment Tertiary only Disinfection only

Q15. Trickling filters are:

Anaerobic attached-growth systems Aerobic attached-growth secondary treatment units Only for grit Membrane processes

Q16. The purpose of a secondary clarifier in ASP is to:

Remove grit Separate biomass (sludge) from treated effluent Disinfect Remove nutrients only

Q17. Sludge digestion (anaerobic) primarily aims to:

Increase volume Stabilise organic matter and reduce pathogens/volume Add nutrients None

Q18. Tertiary treatment is used when:

Only screening is needed Higher quality effluent (e.g. nutrient removal, reuse) is required No secondary treatment exists None

Q19. The primary gaseous pollutant from combustion of sulphur-bearing fuel is:

CO₂ only SO₂ O₃ CH₄

Q20. Photochemical smog is associated with:

SO₂ and fog only NOx, VOCs and sunlight forming ozone and oxidants Only CO Only SPM

Q21. A stable atmosphere (inversion) tends to:

Enhance dispersion of pollutants Suppress vertical mixing and worsen air quality Always rain None

Q22. Electrostatic precipitators are used to control:

Gaseous SO₂ only Particulate matter Noise Odour only

Q23. National ambient air quality standards in India are notified for pollutants including:

Only CO₂ PM₁₀, PM₂.₅, SO₂, NO₂, O₃, CO, etc. Only noise Only BOD

Q24. Typical composition of municipal solid waste in Indian cities has a high fraction of:

Only metals Biodegradable / organic matter Only plastics Only glass

Q25. The preferred hierarchy in solid waste management is:

Dispose → recycle → reduce Reduce → reuse → recycle → recover → dispose Incinerate everything Only landfill

Q26. Sanitary landfills differ from open dumps mainly by:

No cover Engineered lining, compaction, daily cover, leachate and gas management Only burning None

Q27. Composting of MSW is a method of:

Thermal treatment only Biological stabilisation of organic fraction Only metal recovery None

Q28. Sound pressure level is commonly expressed in:

Pascal only Decibels (dB) Hertz only Watts only

Q29. A-weighting (dB(A)) is used because:

It matches human ear frequency response It measures only infrasound It ignores all noise None

Q30. Permissible ambient noise limit for residential areas at night in India (typical CPCB) is about:

75 dB(A) 45 dB(A) 90 dB(A) 20 dB(A)

Environmental Engineering – Theory & Key Points

📖 Water Requirements & Quality Standards

Demand components: domestic, industrial, commercial, public use, fire demand, losses. Design often uses 135–200 lpcd for domestic supply (CPHEEO/IS guidance; varies with city size).

Drinking water standards (illustrative BIS/WHO themes): turbidity, colour, pH, hardness, iron, fluoride, nitrate, residual chlorine, and bacteriological criteria (coliforms/E. coli). Standards set acceptable/permissible limits for health and acceptability.

📖 Surface Water Treatment – Unit Operations & Processes

Typical train:

1. Screening / pre-treatment – remove debris.
2. Aeration (if needed) – strip gases, oxidise Fe/Mn.
3. Coagulation–flocculation – alum/ferric salts + mixing; colloidal destabilisation and floc growth.
4. Sedimentation – settle flocs.
5. Filtration – rapid sand / dual media; polish residual turbidity.
6. Disinfection – chlorine, chloramines, UV, ozone; maintain residual in distribution.

Softening (lime–soda or ion exchange), adsorption (GAC), membrane processes and fluoridation/defluoridation are additional processes as required.

Distribution: service reservoirs, pumping, grid/branched/ring networks; maintain pressure and residual disinfectant; minimise leakage and contamination.

📖 Wastewater Quantity & Characteristics

Sewage quantity ≈ 70–80% of water supplied (plus infiltration/inflow in sewers).

Key parameters:

• BOD₅ – oxygen used by microbes over 5 days at 20°C; measure of biodegradable organics.
• COD – chemical oxygen demand; includes non-biodegradable organics; COD > BOD.
• TSS / VSS – suspended solids; settleable solids measured in Imhoff cone.
• Nutrients (N, P), pathogens, pH, oil & grease, heavy metals (industrial contribution).

📖 Wastewater Treatment

Primary: screens → grit chamber → primary sedimentation. Removes settleable SS and floating matter; BOD reduction modest (~25–35%).

Secondary (biological):

• Activated sludge process (ASP) – aerobic suspended growth; aeration tank + secondary clarifier; return activated sludge (RAS).
• Trickling filter / biofilter – aerobic attached growth.
• Oxidation ponds / stabilisation ponds – natural systems.
• UASB and other anaerobic processes for medium–high strength wastes.

Tertiary / advanced: nutrient removal (N, P), filtration, disinfection, membranes – for reuse or sensitive receiving waters.

Sludge: thickening → digestion (anaerobic/aerobic) → dewatering → disposal/reuse (compost, controlled land application) subject to standards.

Effluent standards: prescribed BOD, TSS, pH, residual Cl₂, nutrients, etc. for discharge to inland surface waters, public sewers, land irrigation or marine outfall (CPCB/SPCB).

📖 Air Pollution

Primary pollutants: SO₂, NOx, CO, PM (PM₁₀, PM₂.₅), VOCs, Pb – emitted directly.

Secondary: ozone, PAN, sulphates/nitrates – form in atmosphere (e.g. photochemical smog from NOx + VOCs + sunlight).

Sources: vehicles, industry, power plants, biomass burning, construction, natural (dust, volcanoes).

Impacts: health (respiratory, cardiovascular), visibility, acid rain, crop damage, climate forcing.

Meteorology: wind speed/direction, mixing height, stability and inversions control dispersion. Stable conditions and inversions trap pollutants.

Control:

• Particulates – cyclones, bag filters, ESPs, scrubbers.
• Gases – absorption, adsorption, catalytic converters, FGD (for SO₂), SCR/SNCR (for NOx).

Standards: National Ambient Air Quality Standards (NAAQS) for ambient air; emission standards for stacks and vehicles.

📖 Municipal Solid Waste

Characteristics: composition (organics, paper, plastics, glass, metal, inert), moisture, calorific value, density – vary by income, season, culture.

Generation, collection & transport: per-capita generation rates; storage; primary/secondary collection; transfer stations; haul to processing/disposal.

Management hierarchy: reduce → reuse → recycle → energy recovery → treat → dispose.

Engineered systems:

• Material recovery facilities, composting, biomethanation.
• Waste-to-energy (where calorific value and emissions control allow).
• Sanitary landfill – liner, leachate collection, gas management, daily cover, closure and post-closure care (not open dumping).

📖 Noise Pollution

Sound level is measured in decibels (dB); environmental noise usually reported as dB(A) (A-weighted).

$$ L_p = 20\log_{10}\frac{p}{p_0}\ \text{dB},\quad p_0 = 20\ \mu\mathrm{Pa} $$

Impacts: hearing impairment, sleep disturbance, stress, reduced productivity, interference with communication.

Limits (illustrative CPCB ambient standards): residential 55 dB(A) day / 45 dB(A) night; commercial and industrial zones higher; silence zones stricter.

Control: source control (quieter machinery, maintenance), path control (barriers, enclosures, distance), receiver protection (PPE), land-use planning and timing restrictions.

Yogendra Gopal Borse

Civil Engineer | Assistant Engineer Grade-I, Maharashtra PWD

B.Tech (Civil) from VJTI Mumbai. Experienced in bridge design, road works, estimation, project monitoring and digital engineering tools. Creator of YogiPWD – practical technical resources for civil engineers.

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