GATE Civil Engineering Environmental Engineering Syllabus

Environmental Engineering syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Environmental Engineering in GATE Civil Engineering, not a summary of it.

1. 1

   Water and Waste Water Quality and Treatment

   6 topics

   • Basics of Water Quality Standards
     • Physical parameters
     • Chemical parameters
     • Biological parameters
   • Water Quality Index
   • Unit Processes and Operations
   • Water Requirement
   • Water Distribution System
   • Drinking Water Treatment
2. 2

   Sewerage System Design

   6 topics

   • Quantity of Domestic Wastewater
   • Primary Treatment
   • Secondary Treatment
   • Effluent Discharge Standards
   • Sludge Disposal
   • Reuse of Treated Sewage for Different Applications
3. 3

   Air Pollution

   5 topics

   • Types of Pollutants
   • Sources and Impacts
   • Air Pollution Control
   • Air Quality Standards
   • Air Quality Index and Limits
4. 4

   Municipal Solid Wastes

   4 topics

   • Characteristics
   • Generation
   • Collection and Transportation of Solid Wastes
   • Engineered Systems for Solid Waste Management
     • Reuse/Recycle
     • Energy Recovery
     • Treatment
     • Disposal

Environmental Engineering flashcards for GATE Civil Engineering

21 of 50 cards from the Environmental Engineering deck — real questions with worked answers.

1. What does turbidity measure in water, and in which unit is it expressed?

   Turbidity measures the optical cloudiness caused by suspended/colloidal particles scattering light. It is expressed in NTU (Nephelometric Turbidity Units). Drinking water should ideally have turbidity $< 1$ NTU (acceptable up to $5$ NTU per IS 10500).

2. Define BOD (Biochemical Oxygen Demand) and state the standard test conditions.

   BOD is the amount of dissolved oxygen consumed by microorganisms to biochemically oxidize organic matter. The standard test ($\text{BOD}_5$) is incubated at $20^{\circ}\text{C}$ for $5$ days, expressed in mg/L.

3. Write the first-order equation relating BOD exerted ($y_t$) to ultimate BOD ($L_0$).

   $$y_t = L_0\left(1 - 10^{-k_D t}\right)$$ where $k_D$ is the deoxygenation rate constant (base 10) per day and $t$ is time in days.

4. How does the BOD rate constant $k$ change with temperature?

   $$k_T = k_{20}\,\theta^{(T-20)}$$ where $\theta \approx 1.047$ for BOD deoxygenation. So the rate roughly increases by about $4.7\%$ per $^{\circ}\text{C}$ rise.

5. What is COD and how does it compare with BOD?

   COD (Chemical Oxygen Demand) is the oxygen equivalent of organic matter oxidizable by a strong chemical oxidant (e.g. $\ce{K2Cr2O7}$). COD $>$ BOD always, because COD oxidizes both biodegradable and non-biodegradable matter; a low BOD/COD ratio indicates poor biodegradability.

6. Define DO (Dissolved Oxygen) and its typical saturation value in fresh water at $20^{\circ}\text{C}$.

   DO is the concentration of molecular oxygen dissolved in water (mg/L). Saturation DO in fresh water is about $9.17$ mg/L at $20^{\circ}\text{C}$; it decreases as temperature and salinity increase.

7. What is the permissible pH range for drinking water as per IS 10500?

   The acceptable pH range for drinking water is $6.5$ to $8.5$. There is no relaxation permitted beyond this range.

8. State the IS 10500 acceptable and permissible limits for total hardness (as $\ce{CaCO3}$).

   Acceptable limit: $200$ mg/L; permissible limit (no alternate source): $600$ mg/L, expressed as $\ce{CaCO3}$.

9. Classify water hardness ranges (as $\ce{CaCO3}$) into soft, moderate, hard and very hard.

   Soft: $0$–$75$ mg/L; Moderately hard: $75$–$150$ mg/L; Hard: $150$–$300$ mg/L; Very hard: $>300$ mg/L (as $\ce{CaCO3}$).

10. Differentiate carbonate (temporary) and non-carbonate (permanent) hardness.

    Carbonate hardness is due to bicarbonates/carbonates of $\ce{Ca}$ and $\ce{Mg}$, removable by boiling or lime. Non-carbonate hardness is due to sulphates, chlorides and nitrates of $\ce{Ca}$/$\ce{Mg}$, removable only by lime-soda or ion exchange.

11. What chemical/biological parameter does MPN test estimate, and what does it indicate?

    MPN (Most Probable Number) statistically estimates the density of coliform bacteria per $100$ mL of water. Coliforms are indicator organisms signaling possible faecal contamination; drinking water should have zero $E.\,coli$ per $100$ mL.

12. Define the Water Quality Index (WQI) and its purpose.

    WQI is a single dimensionless number that aggregates several water-quality parameters (DO, pH, BOD, turbidity, etc.) using weighted sub-indices into one value, simplifying communication of overall water quality to a non-technical audience.

13. Write the general weighted-sum form of the Water Quality Index.

    $$\text{WQI} = \sum_{i=1}^{n} W_i\, q_i$$ where $q_i$ is the quality rating (sub-index) of parameter $i$ and $W_i$ is its unit weight, with $\sum W_i = 1$.

14. List the main physical parameters of water quality.

    Temperature, turbidity, colour, taste, odour, and total solids (suspended + dissolved). These affect aesthetics and acceptability rather than direct toxicity.

15. Distinguish total solids (TS), total suspended solids (TSS) and total dissolved solids (TDS).

    TS = all residue after evaporation. TSS = portion retained on a filter (suspended). TDS = portion passing the filter (dissolved). Thus $\text{TS} = \text{TSS} + \text{TDS}$.

16. Name three common unit operations and three unit processes in water treatment.

    Unit operations (physical): screening, sedimentation, filtration. Unit processes (chemical/biological): coagulation, disinfection, biological oxidation. Operations rely on physical forces; processes involve chemical/biological reactions.

17. State the per-capita water demand figures used in Indian design (domestic + total).

    For Indian towns with full flushing, typical design figures are domestic demand $\approx 135$ lpcd and total demand $\approx 270$ lpcd (including industrial, public, fire and losses).

18. What is the Goodrich formula for variation of water demand over a period $t$ (days)?

    $$p = 180\, t^{-0.10}$$ where $p$ is the percentage of the annual average daily demand drawn in $t$ days (e.g. for $t=1$ day, $p=180\%$).

19. Give the standard peak factors for maximum daily, maximum hourly, and combined demand.

    Maximum daily demand $= 1.8 \times$ average daily; Maximum hourly demand $= 1.5 \times$ average hourly of max day; Combined (coincident) peak $= 1.8 \times 1.5 = 2.7 \times$ average.

20. What is fire demand by the Kuichling formula?

    $$Q = 3182\sqrt{P}$$ where $Q$ is fire demand in L/min and $P$ is population in thousands.

21. Name the four common layouts of a water distribution system.

    Dead-end (tree) system, grid-iron (gridded) system, ring (circular) system, and radial system. Grid-iron and ring give good circulation and reliability; dead-end is cheapest but accumulates stagnant water.

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