Category: Environmental Engineering Objective Questions

Environmental Science Multiple Choice Questions on “Air Pollution – Meteorology”.

1. What does the word ‘meteorology’ define?
a) Study of meteors and asteroids
b) Study of measurements and instruments
c) Study of chemical properties of metals
d) Study of the weather and atmospheric changes
Answer: d
Clarification: Meteorological information is necessary predict and plan the control of air pollution.

2. What is a “tetroon” in the field of meteorology?
a) A tool used to study wind patterns
b) A tool used to study pressure variations
c) A tool used to study temperature deviations
d) A tool used to study humidity
Answer: a
Clarification: Tetroon – Tetrahedral Balloon drifts horizontally along with the wind and is tracked by radar. It is used to analyse local wind patterns.

3. What does the Richardson number indicate in wind analysis?
a) Mechanical turbulence
b) Convective heat production
c) Mechanical turbulence & Convective heat production
d) None of the mentioned
Answer: c
Clarification: Richardson number (-Ri) gives a relative rate of production of mechanical and convective energy.

4. Above which Richardson number does vertical mixing in winds disappear?
a) 1
b) 0.25
c) 0.5
d) 0.75
Answer: b
Clarification: Beyond Richardson number of 0.25, the vertical mixing comes to a standstill and weak horizontal eddies alone remain.

5. When Richardson number is equal to zero, what is the wind turbulence characteristic?
a) No vertical mixing
b) Weak mechanical turbulence due to stratification
c) Convective mixing is greater than mechanical turbulence
d) Only mechanical turbulence
Answer: d
Clarification: When Richardson number is zero, there is mechanical turbulence alone.

6. Below what Richardson number does convective mixing start dominating mechanical turbulence?
a) 0
b) -0.04
c) -0.03
d) -0.1
Answer: b
Clarification: Between 0 and -0.03, both mechanical turbulence and convective mixing are present, but mechanical turbulence is greater. Below -0.04, convective mixing starts dominating.

7. What is high pressure area with sinking air also known as?
a) Cyclone
b) Anti-cyclone
c) Eddy zone
d) Richardson zone
Answer: b
Clarification: Anticyclones are high pressure regions with low ventilation where air is sinking, and is warmed by compression.

8. What does the term “turbidity” indicate in atmospheric quality?
a) Indicates density of clouds
b) Reduction of light due to dust particles
c) Indicates the humidity
d) Turbulence of winds
Answer: b
Clarification: Turbidity is the term used to describe reduction in light/visibility due to smoke and other dust particles. Due to air pollution, about 15-20% reduction in sunshine is observed in cities.

9. Which of the following gases vary significantly over time and place at the atmospheric boundary level?
a) Carbon dioxide
b) Ozone
c) Water vapour
d) Oxygen
Answer: c
Clarification: Water vapour varies based on time and place at the atmospheric boundary level due to the continuous action of evaporation and condensation near water bodies.

10. How does atmospheric pressure vary with increase in altitude?
a) It decreases linearly
b) It decreases exponentially
c) It increases linearly
d) It increases till stratosphere and then starts decreasing exponentially
Answer: b
Clarification: At first the pressure gradually decreases with increase in altitude, and with further increase the rate at which pressure drops starts increasing.

11. What does the term obliquity indicate?
a) Earth’s axial tilt of 23.5 degrees
b) Alignment of the Earth’s internal magnetic field
c) Analysis of ocean currents
d) Pressure variation over different seasons
Answer: a
Clarification: Obliquity is the term used to indicate the Earth’s axial tilt which is responsible for the seasonal variations across the northern and southern hemispheres.

12. Which are the two forces balanced by the geostrophic wind?
a) Coriolis effect and pressure gradient force
b) Coriolis force and centrifugal force
c) Frictional force and pressure gradient force
d) Pressure gradient force and centrifugal force
Answer: a
Clarification: Geostrophic winds are those winds which blow parallel to isobars when the both the Coriolis force and pressure gradient force are balanced.

13. Which of the following has the highest albedo?
a) Water surface
b) Plateau surfaces
c) Vegetation
d) Fresh snow
Answer: d
Clarification: Albedo indicates the fraction of solar energy that is reflected back to space. Fresh snow/ice has the highest albedo due to its reflective properties.

14. The stability of the stratosphere is due to which of the following reasons?
a) Absorption of solar energy by ozone layer
b) Strong wind currents
c) Pressure is minimal
d) All of the mentioned
Answer: a
Clarification: The ozone layer in the stratosphere absorbs radiations (mainly UV) coming from the sun. This energy is the key to stratospheric stability.

15. Which of the following is regarded as climate control factor(s)?
a) Latitude
b) Elevation
c) Ocean currents
d) All of the mentioned
Answer: d
Clarification: Climate is affected by latitude, elevation, ocean currents, etc.

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Environmental Engineering Multiple Choice Questions on “Population Forecasting”.

1. In which method of population forecasting, increase in population from decade to decade is assumed constant?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method
Answer: a
Clarification: In the arithmetic increase method, Dp/dt = K where Dp/dt = rate of change of population and K is a constant. So, the increase in the population from decade to decade is assumed constant.

2. What is the expression used for population forecasting by the arithmetical increase method?
a) PO (1 + R/100)ⁿ
b) PO + n*x
c) PO + n*x + ( n(n+1)/2 )*y
d) PO – n*x
Answer: b
Clarification: The expression of the arithmetical increase method is given by PO+n*x, where PO is the present population, x is the average of the population increase in known decade and n is the number of decades.

3. In which method of population forecast, percentage increase in population from decade to decade is assumed constant?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method
Answer: b
Clarification: In the geometrical increase method, percentage increase in population from decade to decade is assumed constant. Percentage increase in population is found from a population of 3 or 4 decades and then its average is found.

4. What is the expression used for population forecasting by the geometrical increase method?
a) PO (1 + R/100)ⁿ
b) PO + n*x
c) PO + n*x + (n (n+1) /2) *y
d) PO – n*x
Answer: a
Clarification: The expression of geometrical increase method is given by PO (1 + R/100) n
where PO is the present population, R is the average percentage growth rate per decade and n is the number of decades.

5. Which method of population forecast combines both arithmetical increase and geometrical increase method?
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method
Answer: c
Clarification: In the incremental increase method, the population for the next decade is found by adding to the present population, the average increase plus the average incremental increase per decade, hence combines both arithmetical and geometrical methods.

6. What is the expression used for population forecasting by the incremental increase method?
a) PO (1 + R/100)ⁿ
b) PO + n*x
c) PO + n*x + (n (n+1) /2) *y
d) PO – n*x
Answer: c
Clarification: The expression of the incremental increase method is given by PO + n*x + (n (n+1) /2) *y where PO is the present population, x is the average of the population increase in known decade, y is the average of incremental increase and n is the number of decades.

7. Logistic method is also called as _______
a) Arithmetical increase method
b) Geometrical increase method
c) Incremental increase method
d) Decreased rate of growth method
Answer: d
Clarification: Logistic method is also called a decreased rate of growth method. In this method, the percentage increase in growth rate and then the percentage decrease in growth rate are founded where all populations grow according to the logistic curve.

8. Consider the following statements.
i. The arithmetical increase method is suitable for new cities
ii. The decreasing growth rate method is used where the rate of growth shows a downward pattern
iii. The geometrical increase method is used for older cities
Which of the following above statements is/are correct?
a) i, ii, iii
b) i and iii
c) Only ii
d) ii and iii
Answer: c
Clarification: Arithmetical increase method is suitable for older cities, whereas a geometrical increase method is suitable for new cities.

9. Which method is suitable if the growth rate is decreasing and the population is reaching towards saturation?
a) Arithmetical increase method
b) Graphical comparison method
c) Zoning method
d) Decreased rate of growth method
Answer: d
Clarification: In decreased rate of growth method, growth rate is decreasing and the population is reaching towards saturation and is only valid when growth rate shows a downward pattern.

10. Which method of population forecast is suitable when extension is required for small duration and past record is available for long duration?
a) Graphical comparison method
b) Graphical extension method
c) Logistic curve method
d) Zoning method
Answer: b
Clarification: In the graphical extension method, a curve is drawn between population and time up to the present period, then the curve is extended from present to the future decade and the population is approximately determined from the extended part of the curve.

Environmental Engineering Multiple Choice Questions on “Filtration Hydraulics”.

1. The head loss through the bed of solids of the filter can be determined by __________
a) Carmen-Kozney equation
b) Rose equation
c) Carmen-Kozney and Rose equation
d) Charles equation
Answer: c
Clarification: The head loss through the bed of solids of the filter can be determined by both Carmen-Kozney and Rose equation where two cases are considered, one for homogeneous mixed bed and other for stratified bed.

2. Which of the following has the highest shape factor as stated by Carmen?
a) Ottawa sand
b) Pulverized coal
c) Rounded coal
d) Angular sand
Answer: a
Clarification: The shape factor as stated by Carmen is 0.95 for Ottawa sand, 0.73 for pulverized coal and angular sand and 0.82 for rounded sand.

3. Which of the following is the expression of the Carmen equation where symbols have their usual meanings?
a) hf = f* (L/(s *d)) * ((1-e)/e³) * (v²/g)
b) hf = f* (L/(s *d)) * ((1-e)/e³) * (v/g)
c) hf = f* (L/(s *d)) * ((1-e)/e) * (v²/g)
d) hf = f* (L/(s *d)) * ((1-e)/e²) * (v²/g)
Answer: a
Clarification: The expression of the Carmen equation is given by hf = f* (L/(s *d)) * ((1-e) /e³) * (v²/g) where hf =head loss, d= diameter of pipe. L= length of pipe and v=approach velocity.

4. Which of the following represents the correct relation between dimensionless friction factor f and Reynolds number?
a) f = 150* ((1-e) /R²) + 1.75
b) f = 150* ((1-e) /R) +1.75
c) f = 150* ((1-e) /R³) + 1.75
d) f = 150* ((1-e²) /R) + 1.75
Answer: b
Clarification: The correct relation between dimensionless friction factor and Reynolds number is given by f = 150* ((1-e) /R) + 1.75 Where R is the Reynolds number and the expression (1-e) represents the volume of solids.

5. Which of the following is the expression of the Rose equation where symbols have their usual meanings?
a) hf = f* (L/(s *d)) * ((1-e) /e³) * (v²/g)
b) hf = f* (L/(s *d)) * ((1-e) /e³) * (v/g)
c) hf = f* (L/(s *d)) * ((1-e) /e⁴) * (v²/g)
d) hf = f* (L/(s *d)) * ((1-e) /e²) * (v²/g)
Answer: a
Clarification: The expression of the Rose equation is given by hf = f* (L/(s *d)) * ((1-e⁴) /e³) * (v²/g) where hf = head loss, d = diameter of pipe. L = length of pipe and v=approach velocity and f = 1.067CD, Where CD is the coefficient of drag.

6. When the Reynolds number is greater than 1.9 but less than 500, the coefficient of drag CD is?
a) CD = 24/R
b) CD = R/24
c) CD = 18.5/R^0.6
d) CD = R^0.6/18.5
Answer: c
Clarification: When the Reynolds number is greater than 1.9 but less than 500, the coefficient of drag C_D is C_D = 18.5/R^0.6 where R is the Reynolds number.

7. The value of Reynolds number R is 1.5. The coefficient of drag is?
a) 8
b) 10
c) 12
d) 16
Answer: d
Clarification: When R<1.9, the value of the coefficient of drag = 24/R
R=1.5, the coefficient of drag = 24/1.5 = 16.

8. Rose equation is valid for beds in which voids are clear and unobstructed.
a) True
b) False
Answer: a
Clarification: Rose equation is valid for beds in which voids are clear and unobstructed though during continues filtration, voids get clogged and head loss goes on increasing.

9. When does the particle become suspended in an expanded bed?
a) When superficial velocity is greater than critical velocity
b) When superficial velocity is less than critical velocity
c) When superficial velocity is equal to critical velocity
d) When superficial velocity is constant
Answer: c
Clarification: During back washing, the bed remains fixed at low fluid velocity and as the superficial velocity increases, the lighter particles move upward and when this velocity equals the critical velocity, the particle becomes suspended.

10. The superficial velocity in a stratified bed is equal to __________
a) Terminal settling velocity
b) Terminal settling velocity * porosity
c) Terminal settling velocity * (porosity)²
d) Terminal settling velocity * (porosity)^4.5
Answer: d
Clarification: A stratified bed having a non uniform sized particles are completely fluidized when for the largest particle, the superficial velocity v = vs * e^4.5 where vs is the terminal settling velocity and e is the porosity.

11. Carmen-Kozney equation has been derived using which of the following equation?
a) Cole brook white equation
b) Bernoulli equation
c) Darcy Weisbach equation
d) Swamee jain equation
Answer: c
Clarification: Carmen-Kozney equation has been derived using Darcy Weisbach equation which is given by h = f*l*v²/(g*D) Where h is the head loss, D is the diameter of pipe, v is the velocity of the particle and f is the dimensionless friction factor.

Environmental Engineering Multiple Choice Questions on “Desalination”.

1. Which of the following method is not used for desalination?
a) Distillation
b) Coagulation
c) Reverse osmosis
d) Freezing
Answer: a
Clarification: Coagulation is not used for desalination. It is done for removing the suspended impurities from water.

2. Which of the following is not a type of distillation plant?
a) Vertical tube evaporator
b) Multistage flash evaporator
c) Tube settler
d) Multi-effect multistage flash evaporator
Answer: c
Clarification: Tube settler is not a type of distillation plant. It is used for shallow depth sedimentation.

3. Multistage flash evaporator produces _____ kg of water per kg of prime steam.
a) 5
b) 10
c) 15
d) 20
Answer: d
Clarification: Multistage flash evaporator produces 20 kg of water per kg of prime steam.
They operate on the brine recycling basis.

4. Which of the following is the best evaporative desalinating method?
a) Vertical tube evaporator
b) Multistage flash evaporator
c) Tube settler
d) Multi-effect multistage flash evaporator
Answer: b
Clarification: Multistage flash evaporator is the best evaporative desalinating method in which the efficiency of multistage flash evaporator can be further improved by the use of flash enhancers.

5. The number of stages involved in the desalination using a multistage flash evaporator is _________________
a) 20
b) 38
c) 49
d) 69
Answer: d
Clarification: Multistage flash evaporator uses 69 stages in the desalination process. The vapors released during flash each stage condenses to heat the incoming sea water and gives fresh water.

6. Which of the following desalination method is more suitable for brackish water than sea water?
a) Distillation
b) Solar evaporation
c) Reverse osmosis
d) Freezing
Answer: c
Clarification: Reverse osmosis is more suitable for brackish water than sea water. In this process, some part of water permeates the membrane and is collected as fresh water while the remaining water passed through the turbine for recovery.

7. The process in which the brackish water is forced across a permeable membrane by mechanical forces is called as _____________
a) Filtration
b) Semi filtration
c) Coagulation
d) Hyper filtration
Answer: d
Clarification: The process in which the brackish water is forced across a permeable membrane by mechanical forces is called as hyper filtration. The pressure applied must be greater than the osmotic pressure.

8. In which desalination process, the salt ions are removed from seawater by means of electric current?
a) Distillation
b) Electro-dialysis
c) Reverse osmosis
d) Freezing
Answer: b
Clarification: In Electro dialysis, the salt ions are removed from seawater by means of electric current where two membranes are used- one who is more selective to anode and another who is more selective to cathode.

9. In Electro-dialysis, the electric energy which required is _____________
a) Directly proportional to cation permeable membrane
b) Directly proportional to anion permeable membrane
c) Directly proportional to salt concentration
d) Inversely proportional to salt concentration
Answer: c
Clarification: In Electro-dialysis, the passage of electric current helps the diffusion of cation and anion permeable membrane and the energy required is directly proportional to the concentration of salt in the saline water.

10. The maximum salt concentration up to which desalination of brackish water is possible by Electro-dialysis is _____________
a) 1000ppm
b) 2000ppm
c) 3000ppm
d) 5000ppm
Answer: d
Clarification: Electro-dialysis is suitable for brackish water with a total concentration of salt up to 5000ppm and leaving 100ppm in the treated water.

11. In which desalination process, the cooling of sea water is done to obtain fresh water?
a) Distillation
b) Electro-dialysis
c) Reverse osmosis
d) Freezing
Answer: d
Clarification: In freezing method of desalination, cooling of the water takes place to obtain fresh water by separation of the ice and brine liquor.

12. The pressure freezing process works on the vacuum free vapor compression principle.
a) True
b) False
Answer: b
Clarification: Zarchin colt freezing process works on the vacuum free vapor compression principle. In this process, water is used as a refrigerant.

13. In which desalination process, solar energy is used?
a) Reverse osmosis
b) Freezing
c) Electro-dialysis
d) Solar evaporation
Answer: d
Clarification: In the solar evaporation, the solar energy is used as a source of heat energy. The solar energy striking the earth is estimated to be a 250BTU / day/m².

14. The solar evaporation can yield about ___ kg of fresh water per day per m² of basin surface.
a) 5
b) 10
c) 15
d) 20
Answer: a
Clarification: The solar evaporation can yield about 5 kg of fresh water per day per m² of basin surface under good sunshine conditions. The solar energy is absorbed by salt water and fresh water is produced.

Environmental Engineering Questions for Campus interviews on “Minimum and Maximum Velocity of Flow”.

1. _______ is the velocity at which the solid matter in sewage remained in suspended form.
a) Settling velocity
b) Self cleansing velocity
c) Mean velocity
d) Non Scouring velocity
Answer: b
Clarification: Self cleansing velocity is the minimum velocity, which is required to keep the solid particles in suspended form otherwise they will settle and result in clogging.

2. The expression for the self cleansing velocity is given by ____________
a) (8*B* (G-1) *g*d/f)^1/3
b) (8*B* (G-1) *g*d/f) ²
c) (8*B* (G-1) *g*d/f)
d) (8*B* (G-1) *g*d/f)^1/2
Answer: d
Clarification: The self cleansing velocity V is given by V = (8*B* (G-1) *g*d/f) ^1/2 Where, G is the specific gravity, g is the acceleration due to gravity, d is the diameter of sewer and f is the Darcy Weisbach friction factor.

3. The self cleansing velocity required for coarse sand is __________
a) 10cm/Sec
b) 20cm/Sec
c) 30cm/Sec
d) 40cm/Sec
Answer: b
Clarification: The self cleansing velocity required for coarse sand is 20cm/Sec which is higher than fine sand having 15cm/Sec.

4. In which of the following, the self cleansing velocity is maximum?
a) Angular stones
b) Fine sand
c) Fine clay
d) Fine gravel
Answer: a
Clarification: The self cleansing velocity for angular stones is 100cm/Sec while of fine sand, fine clay and fine gravel are 15cm/Sec, 7.5cm/Sec and 30cm/Sec respectively.

5. The diameter of the sewer is 23cm. What should be the self cleansing velocity?
a) 10cm/Sec
b) 40cm/Sec
c) 100cm/Sec
d) 130cm/Sec
Answer: c
Clarification: When the diameter of the sewer is between 15cm and 25cm, the self cleansing velocity is 100cm/Sec.

6. What should be the diameter of the sewer when the self cleansing velocity is 60cm/Sec?
a) 10cm
b) 20cm
c) >60cm
d) 100cm
Answer: c
Clarification: The self cleansing velocity varies inversely with the diameter of the sewer and when the diameter is above 60, the self cleansing velocity is 60cm/Sec whereas, for 15cm diameter of the sewer, it is 100cm/Sec.

7. The maximum velocity at which no abrasion takes place is called _______
a) Settling velocity
b) Self cleansing velocity
c) Mean velocity
d) Non Scouring velocity
Answer: d
Clarification: The non scouring velocity is the maximum velocity at which no scouring action takes place. It depends on the material used in the construction of sewers.

8. The non scouring velocity is 260cm/Sec. The type of material of the sewer is __________
a) Earth channels
b) Stone ware sewers
c) Brick lined sewer
d) Cement concrete sewer
Answer: d
Clarification: The non scouring velocity for cement concrete sewer lies between 250cm/Sec to 300 cm/Sec.

9. The non scouring velocity required for cast iron sewer pipes is __________
a) 50cm/Sec
b) 350cm/Sec
c) 160cm/Sec
d) 220cm/Sec
Answer: b
Clarification: The non scoring velocity depends on the material sewer and it is higher for cast iron sewer pipe with a range of 350-450cm/Sec.

To practice all areas of Environmental Engineering for Campus Interviews, .

Environmental Engineering Multiple Choice Questions on ” Oxygen Sag Curve”.

1. What is yellow curve represents in the following figure?

Figure: Oxygen sag curve
a) Deoxygenation curve
b) Reoxygenation curve
c) Oxygen sag curve
d) Equilibrium concentration of oxygen
Answer: a
Clarification: The yellow curve represents the deoxygenation curve, which depicts the depletion of dissolved oxygen in the absence of aeration.

2. Which of the following is represented by the green curve in the following figure?

Figure: Oxygen sag curve
a) Deoxygenation curve
b) Reoxygenation curve
c) Oxygen sag curve
d) Equilibrium concentration of oxygen
Answer: b
Clarification: The green curve represents the reoxygenation curve, which depicts the supply of oxygen from the atmosphere to counterbalance the oxygen deficit.

3. The maximum deficiency of dissolved oxygen is represented by ____________

Figure: Oxygen sag curve
a) Dotted blue line
b) Green curve
c) Yellow curve
d) Violet curve
Answer: a
Clarification: The maximum deficiency of dissolved oxygen is represented by the dotted blue line. It is finding with respect to the equilibrium concentration of oxygen.

4. Which of the following represents the oxygen sag curve in the following figure?

Figure: Oxygen sag curve
a) Dotted blue line
b) Green curve
c) Yellow curve
d) Red curve
Answer: d
Clarification: The oxygen sag curve is represented by the red curve. It is also called as an oxygen deficit curve.

5. The oxygen deficit is maximum when?

Figure: Oxygen sag curve
a) Rate of reaeration is 0
b) Rate of deoxygenation is 0
c) Rate of reaeration equals the rate of deoxygenation
d) Rate of reaeration > rate of deoxygenation
Answer: c
Clarification: The rate of oxygen deficit is the sum of the rate of reaeration and the rate of deoxygenation and it is maximum when the rate of reaeration equals the rate of deoxygenation.

6. When the BOD of wastewater increases, then?

Figure: Oxygen sag curve
a) Rate of reaeration decreases
b) Rate of oxygen deficit increases
c) Rate of oxygen deficit decreases
d) Amount of oxygen in wastewater increases
Answer: b
Clarification: When the BOD of wastewater increases, the amount of dissolved oxygen decreases, so the rate of oxygen deficit increases.

7. Rate of aeration is independent of the D.O content of wastewater.

Figure: Oxygen sag curve
a) True
b) False
Answer: b
Clarification: Rate of aeration = -(Rate of dissolved oxygen in water) which implies that the rate of aeration increases with increase in reduction of dissolved oxygen from wastewater.

8. The reoxygenation constant at temperature ‘T’ is expressed by ___________
a) K_RT = K_R20 (1.016)^T
b) K_RT = K_R20 (1.047) ^T-20
c) K_RT = K_R20 (1.016)^T-20
d) K_RT = K_R20 (1.047)^T
Answer: c
Clarification: The reoxygenation constant at temperature ‘T’,
K_RT = K_R20 (1.016)^T-20, where K_R20 is the reoxygenation constant at 20^oC.