Category: Environmental Engineering Objective Questions

Environmental Engineering Multiple Choice Questions on “Flocculation and Clarification”.

1. __________ is an operation designed to force agitation in the fluid and induce coagulation.
a) Sedimentation
b) Flocculation
c) Disinfection
d) Aeration
Answer: b
Clarification: Flocculation is an agitating process in which destabilized particles are brought into contact to promote agglomeration.

2. The rate of change of velocity per unit distance normal to a section is called_______
a) Mean velocity
b) Average velocity
c) Mean velocity gradient
d) Velocity gradient
Answer: c
Clarification: Mean velocity gradient is given by G = (P/uv)^1/2 Where P = power dissipated, u = absolute viscosity, v = volume to which power is applied.

3. What is the dimension formula of mean velocity gradient?
a) 1/T
b) 1/T2
c) T
d) T2
Answer: a
Clarification: Mean velocity gradient is expressed in metre per second/m or Sec^-1, so it has dimension formula of 1/T.

4. What is the desirable value of mean velocity gradient in a flocculator?
a) 20-50sec^-1
b) 20-75sec^-1
c) 50-100sec^-1
d) 30-50sec^-1
Answer: b
Clarification: The desirable value of mean velocity gradient (G) in a flocculator is 20-75sec^-1 and for ‘Gt’ is 2*10⁴ to 6*10⁴ where ‘Gt’ is the ratio of power induced rate of flow to displace mean induced rate of flow.

5. What is the normal value of the detention period adopted in a flocculator for design purpose?
a) 30min
b) 60min
c) 90min
d) 100min
Answer: a
Clarification: The detention period in a flocculator for design purpose should be in the range of 10-40min and its normal value should be 30min.

6. The design value of the velocity of flow in a flocculator is _______
a) 0.2-0.8m/s
b) 0.3-0.5m/s
c) 0.6-0.8m/s
d) 0.1-0.5m/s
Answer: a
Clarification:The normal value of the velocity of flow in a flocculator is 0.4m/s and its range is 0.2-0.8m/s.

7. What is the detention period of a clarifier used in the treatment of water?
a) 1hour
b) 2hours
c) 3hours
d) 4hours
Answer: c
Clarification: The detention period of a clarifier is lower than in the plain sedimentation tank and its range is 2.5 to 3 hours.

8. The pulsator clarifier is a type of __________
a) Horizontal flow sludge tank
b) Vertical flow sludge tank
c) Circular sludge tank
d) Plain sedimentation tank
Answer: b
Clarification: The pulsator clarifier is a vertical flow sludge tank in which pulse is generated at interval of 30Sec to give rapid flow for 5-10Sec resulting in the alternative rising up of the sludge blanket.

9. Which device solved the problem of unstable hydraulic conditions and operation of sludge removal equipment?
a) Centrifugal pump
b) Pulsator clarifier
c) Tube settler
d) Flocculator
Answer: c
Clarification: Tube settler solved the problem of unstable hydraulic conditions and operation of sludge removal equipment by providing laminar flow conditions for sedimentation.

10. In which device, the primary mixing is followed by a secondary reaction zone resulting in formation of sludge blanket?
a) Centrifugal pump
b) Flocculator
c) Tube settler
d) Solid contact clarifier
Answer: d
Clarification: In Solid contact clarifier, sludge blanket is formed where straining action occurs to remove some of the finer particles. The thickness of the blanket is 1m.

11. In which type of tube settler, tubes are slightly inclined in the direction of normal flow?
a) Solid contact clarifier
b) Steeply inclined tube settler
c) Vertical tube settler
d) Horizontal tube settler
Answer: d
Clarification: In Horizontal tube settler, the tubes are slightly inclined in the direction of normal flow and the sludge settled is drained by filter backwash.They are used in small plants.

Environmental Engineering Multiple Choice Questions on “Iodine, Bromine and Ozone Treatment”.

1. The chemical formula of hypoiodous acid is __________
a) H₂IO
b) H₂I
c) HIO
d) HI₂
Answer: c
Clarification: The chemical formula of hypoiodous acid is HIO which is formed by the reaction of iodine with water and its chemical equation is I₂ + H₂O <=> HIO + H⁺ + I⁺.

2. At what pH, the dissociation of hypoiodous acid takes place?
a) 1
b) 2
c) 3
d) 4
Answer: d
Clarification: The dissociation of hypoiodous acid takes place at pH = 4.
HIO <=> H⁺ + IO^–.

3. What happens to the hypoiodous acid when the pH is over 8?
a) HIO is stable
b) Formation of hypoiodite ion takes place
c) Formation of iodine and hypoiodite ion takes place
d) Formation of iodine and iodate takes place
Answer: d
Clarification: When pH is over 8, then HIO is unstable and will not form hypoiodite ion. The decomposition of hypoiodite ion takes place, resulting in the formation of iodine and iodate.

4. The chemical formula of iodate is __________
a) HIO₃
b) HIO
c) HIO₂
d) H₂IO₂
Answer: a
Clarification: The chemical formula of iodate is HIO₃ which is formed when the pH during the decomposition of hypoiodite ion is over 8.

5. a HIO + b OH- <=> HIO₃ + b H₂O + b I^–. What are the values of a and b respectively in the above equation?
a) 1, 2
b) 1, 3
c) 3, 2
d) 3, 1
Answer: c
Clarification: 3HIO + 2OH^– <=> HIO₃ + 2 H₂O + 2 I^–. This equation is formed when the pH is above 8 and where decomposition of hypoiodite ion takes place.

6. What happen to the concentration of iodine when the pH is between 6 and 8?
a) I2 decreases whereas HIO increases
b) I2 increases, whereas HIO decreases
c) Both I2 and HIO increases
d) Both I2 and HIO decreases
Answer: a
Clarification: 3HIO + 2OH^– HIO₃ + 2 H₂O + 2 I^–. When the pH is between 6 and 8, the percentage of iodine as I2 decreases while the percentage of iodine as HIO is increased.

7. Iodine is a better disinfectant to kill virus than hypoiodous acid.
a) True
b) False
Answer: b
Clarification: Hypoiodous acid destroys viruses at a considerably faster rate than I2 as iodine has little viricidal activity.

8. Ozone is a _______ allotrope of oxygen.
a) Monoatomic
b) Diatomic
c) Triatomic
d) Polyatomic
Answer: c
Clarification: Ozone is a triatomic allotrope of oxygen, which is an unstable gas and the breakdown into normal oxygen containing two atoms of oxygen by molecule.

9. The ozone generators can convert ____ % of feed oxygen into ozone.
a) 1
b) 5
c) 1-4
d) 10
Answer: c
Clarification: The ozone generators can convert 1-4 % of feed oxygen into ozone. They are used as an effective method to clean indoor air pollution and odors.

10. What happens during the breakdown of ozone?
a) CO₂ is formed
b) Nascent oxygen is formed
c) CO₂ and Nascent oxygen is formed
d) Formation of oxygen and water takes place.
Answer: b
Clarification: During the breakdown of ozone, nascent oxygen is formed which contains a single atom of oxygen.

11. Which of the following is most effective in the killing of bacteria present in water?
a) Nascent oxygen
b) Chlorine
c) HOBr
d) I2
Answer: a
Clarification: Nascent oxygen is very effective in oxidizing the organic matter and in the killing of bacteria present in the water which is formed during the breakdown of ozone.

12. The water is free from oxidizable materials. What is the dosage of ozone required?
a) 0.01ppm
b) 0.1-0.2ppm
c) 0.2-0.3ppm
d) 0.4-0.5ppm
Answer: c
Clarification: A dosage of 0.2-0.3ppm is required to kill the coliform bacteria present in water which is free from oxidizable materials.

13. The dosage of ozone for municipal water treatment is __________
a) 0.5 ppm
b) 1ppm
c) 1.5 ppm
d) 2ppm
Answer: c
Clarification: The dosage of ozone for municipal water treatment is 1.5ppm, which is not only used for disinfection but also it removes taste, color and odor from water.

Environmental Engineering Multiple Choice Questions on “Service Connection”.

1. A Service connection is a connection from the distribution system to the ______
a) Factory
b) School
c) Industry
d) Consumer
Answer: d
Clarification: A consumer can be a single house, an apartment or a planned block development. A connection to a single house involves tapping the main and installing a corporation cock.

2. Which of the following is not a component of domestic service connection?
a) Water meter
b) Stopcock
c) Tube settler
d) Gooseneck
Answer: c
Clarification: The various components of a domestic service connection are Brass ferrule, Gooseneck, Stopcock, Mains service pipe and Water meter.

3. The length of Goose neck in a domestic service connection is ____________
a) 10cm
b) 20cm
c) 30cm
d) 40cm
Answer: d
Clarification: The Goose neck consists of 40-50cm curved piece of pipe which prevents the breaking of the main service pipe.

4. Which device is used to measure the quantity of water consumed by the consumer?
a) Water meter
b) Stopcock
c) Tube settler
d) Gooseneck
Answer: a
Clarification: Water meter is used to measure the quantity of water consumed by the consumer. It is installed in a suitable chamber with cover.

5. Which of the following is incorrect regarding water meter?
a) Should be durable
b) Easy to maintain and repair
c) Should allow backflow of water
d) Should be rugged
Answer: c
Clarification: Water meter should prevent the back flow of water passing through it. It should not be liable to clogging.

6. Which device is used to measure the velocity of flow for high flows?
a) Water meter
b) Inferential meter
c) Globe valve
d) Gate valve
Answer: b
Clarification: Inferential meter measures the velocity of flow across a cross section whose area is known. They are only used for high flows.

7. Which of the following is an example of Inferential meter?
a) Turbine meter
b) Hydrometer
c) Water meter
d) Gate valve
Answer: a
Clarification: Turbine and rotary meters are examples of Inferential meter. It is also called as velocity meter as they measure the velocity of flow.

8. Which device is used to measure velocity for low flows?
a) Water meter
b) Inferential meter
c) Globe valve
d) Displacement meter
Answer: d
Clarification: Displacement meter is used to measure velocity for flows. Reciprocating, Rotary, Oscillating and Nutating disc meter are the examples of Displacement meter.

9. Which of the following pipe material has a maximum modulus of elasticity?
a) Concrete
b) Mild steel
c) Cast iron
d) PVC
Answer: b
Clarification: Mild steel has the maximum modulus of elasticity with a magnitude of 2.1 *10¹⁰. The modulus of elasticity of concrete, cast iron and PVC are 2.8*10⁹, 7.5*10⁹ and 3*10⁸ respectively.

Environmental Engineering Multiple Choice Questions on “Physical Characteristics of Waste Water”.

1. Which of the following represents the physical characteristics of water?
a) Chloride content
b) BOD
c) Turbidity
d) COD
Answer: c
Clarification: Turbidity represents the physical characteristic of water, whereas BOD, COD and chloride content represents the chemical characteristic of water.

2. Which of the following is measured in mg/L?
a) Unit weight
b) Coefficient of cohesion
c) Discharge
d) Turbidity
Answer: d
Clarification: The turbidity of waste water is measured in mg/L. The other units of turbidity are ppm, NTU and JTU.

3. Which of the following instrument is used to measure turbidity?
a) Olfactometer
b) Turbidity meter
c) Colorimeter
d) Spectrophotometer
Answer: b
Clarification: Turbidity can be measured by Jackson’s turbidity meter, Baylis turbidity meter, turbidity rod and Nephelometer.

4. When the sewage becomes stronger, the turbidity of wastewater?
a) Increases
b) Decreases
c) Becomes constant
d) Slightly decrease
Answer: a
Clarification: When the sewage becomes stronger, the milkiness in water increases and thus, the turbidity increases.

5. Which color indicates the fresh sewage?
a) Pink
b) Red
c) Black
d) Grey
Answer: d
Clarification: If the color of sewage is grey, yellow and light brown, then it means that the sewage is fresh.

6. The color of the septic sewage is __________
a) Pink
b) Red
c) Black
d) Grey
Answer: c
Clarification: The color of septic sewage is black or dark brown. It contains either little or no oxygen.

7. The odor in wastewater is measured by __________
a) Osmoscope
b) Chromatography
c) Olfactometer
d) Turbidity meter
Answer: a
Clarification: The odor in waste water is measured by Osmoscope which consist of two 10mm diameter glass tubes which is 300mm long and 8mm wide.

8. In India, the average temperature of sewage is __________
a) 10^oC
b) 20^oC
c) 40^oC
d) 80^oC
Answer: b
Clarification: The average temperature of sewage is 20^oC. The temperature of sewage is higher than that of the water supply.

9. Identify the incorrect statement from the following?
a) High odor intensity indicates odorless water
b) Fresh sewage is odorless
c) Turbidity can be measured by turbidity rod
d) NTU is a unit of turbidity
Answer: a
Clarification: If the odor intensity of water is 6, it indicates extremely strong odor and when it is 0, it indicates the odorless water.

10. _______ indicates the freshness of sewage.
a) Turbidity
b) Color
c) Temperature
d) COD
Answer: b
Clarification: The color indicates the freshness of sewage. It can be detected easily by the naked eye.

11. ______ represents the number of dilutions required to reduce odor.
a) Dispersion
b) Threshold odor number
c) BOD
d) COD
Answer: b
Clarification: The threshold odor number is equal to the volume of samples of water required to add to 100 units of odorless fresh water at which the mixture gives the first detectable odor.

12. The odor quality of Amines is __________
a) Rotten egg
b) Fishy
c) Fecal matter
d) Decayed cabbage
Answer: b
Clarification: The odor quality of Amines is fishy and its chemical formula is CH₃NH₂.

13. The odor quality of compound is ammoniacal. Identify the type of compound from the following options.
a) Acetic acid
b) Benzene
c) Ammonia
d) Methane
Answer: c
Clarification: Ammonia has an ammoniacal type of odor quality and its chemical formula is NH₃.

14. The wastewater from the kitchen is an example of __________
a) Black water
b) Yellow water
c) Green water
d) Grey water
Answer: d
Clarification: The wastewater from the kitchen is an example of grey water. It also includes water from the bathroom without urine and feces.

15. The type of wastewater from the flushing operation of toilet is __________
a) Green water
b) Red water
c) Black water
d) Brown water
Answer: c
Clarification: The type of wastewater from the flushing operation of toilet is black in color and if it does not include urine, then it is brown in color.

Environmental Engineering Multiple Choice Questions on “Types of Sewage Filter”.

1. The intermittent sand filters have better BOD removal efficiency than trickling filters.
a) True
b) False
Answer: b
Clarification: The trickling filters have the best BOD removal efficiency in comparison to the types of filters used in aerobic treatment with a maximum value of 95%.

2. The filter material used in contact bed is ___________
a) Sand
b) Stone ballast
c) Gravel
d) Fine sand
Answer: b
Clarification: The filter material used in the contact bed is broken stones called as stone ballast.

3. Which of the following is called as contact bed?
a) Primary clarifier
b) Secondary clarifier
c) Contact filter
d) High rate digester
Answer: c
Clarification: Contact filters are water tight tanks that are used for the aerobic treatment of sewage. They are also called as contact bed.

4. How many types of trickling filters are used in sewage treatment?
a) 6
b) 5
c) 3
d) 2
Answer: d
Clarification: The trickling filters are divided into conventional and high rate trickling filters.

5. The depth of the filter media of intermittent filter is ___________
a) 45cm
b) 60cm
c) 20cm
d) 25cm
Answer: b
Clarification: The minimum depth of filter media of intermittent filter is 60cm. These filters give highly nitrified effluent.

6. Which of the following filter is used in the anaerobic treatment of sewage?
a) Intermittent sand
b) Trickling filter
c) Contact filter
d) Biological filter
Answer: d
Clarification: Biological filter is used in anaerobic treatment, whereas intermittent sand filter, trickling filter and contact filter are used in the aerobic treatment of sewage.

7. The maximum size of filter media of a percolating filter is ___________
a) 10mm
b) 25mm
c) 60mm
d) 75mm
Answer: d
Clarification: The minimum and maximum size of filter media of a percolating filter is 25mm and 75mm respectively.

8. The recirculation ratio for the low rate trickling filter is ___________
a) 1
b) 2
c) 3
d) 0
Answer: d
Clarification: The recirculation system is not provided in the low rate trickling filter. So, when the recirculation is 0, the type of filter used is a low rate trickling filter.

Environmental Engineering Question Bank on “Dispersion of Air Pollutants, Contol of Gaseous Pollutants”.

1. When environmental Lapse Rate (ELR) is less is than Adiabatic Lapse Rate (ALR), then which of the following occurs?
a) Sub adiabatic lapse rate
b) Super adiabatic lapse rate
c) Neutral lapse rate
d) Adiabatic lapse rate
Answer: a
Clarification: When the temperature increases with an increase in altitude, Sub adiabatic lapse rate occur and there will be stable environment.

2. _______ occurs when atmospheric temperature increases with height.
a) Negative lapse rate
b) Super adiabatic lapse rate
c) Neutral lapse rate
d) Positive lapse rate
Answer: d
Clarification: Under negative lapse rate, the colder air is below the warmer air. It can be occurred near the earth’s surface.

3. When environmental Lapse Rate (ELR) is equal to the Adiabatic Lapse Rate (ALR), then which of the following occurs?
a) Sub adiabatic lapse rate
b) Super adiabatic lapse rate
c) Neutral lapse rate
d) Adiabatic lapse rate
Answer: c
Clarification: When the temperature is constant with height, then neutral lapse rate occurs.

4. The wet adiabatic rate is greater than the dry adiabatic rate.
a) True
b) False
Answer: b
Clarification: The value of wet adiabatic rate is 60C per 1000m whereas of dry adiabatic rate is 9.80C per 1000m.

5. When Environmental Lapse Rate (ELR) is greater than Adiabatic Lapse Rate (ALR), then which of the following occurs?
a) Sub adiabatic lapse rate
b) Super adiabatic lapse rate
c) Neutral lapse rate
d) Adiabatic lapse rate
Answer: b
Clarification: In Super adiabatic lapse rate, the environment is unstable due to the quick dispersion of pollutants.

6. Which of the following is the absorption unit?
a) Cyclone collector
b) Plate tower
c) Gravitation settling chamber
d) Dynamic precipitator
Answer: b
Clarification: Cyclone collector, Gravitation settling chamber and Dynamic precipitator are used to remove particulate matter, whereas Plate tower is used to remove gaseous matter and is an absorption unit.

7. Which of the following catalyst is used for removing hydrocarbon from gaseous pollutant in combustion unit?
a) Platinum
b) Activated alumina
c) Vanadium
d) Potassium permanganate
Answer: b
Clarification: Activated alumina is used as a catalyst for removing gaseous pollutant called hydrocarbons from the air. The concentration of hydrocarbon emitted from automobiles is 300-1000 mg/l.

8. Which of the following is not a part of adsorption unit?
a) Packed towers
b) Multiple fixed bed
c) Fluidized bed
d) Moving bed
Answer: a
Clarification: Packed tower is a part of the absorption unit, whereas multiple fixed bed, fluidized bed and moving bed are the examples of absorbers.

9. Which of the following is a bulk phenomena?
a) Physical adsorption
b) Chemical adsorption
c) Absorption
d) Sorption
Answer: c
Clarification: Adsorption is a bulk phenomena, whereas absorption is a surface phenomena.

10. Which of the following is not an adsorbent?
a) Molecular sieves
b) Activated carbon
c) Activated alumina
d) Water
Answer: d
Clarification: Water is an absorbent whereas molecular sieves, activated carbon and activated alumina are adsorbents.

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