Category: Environmental Engineering Objective Questions

Environmental Engineering Multiple Choice Questions on “Problems in Filter Operation”.

1. The loss of head during cleaning operation of a rapid sand filter is __________
a) 15-30cm
b) 1-5cm
c) 10-20cm
d) 10-25cm
Answer: a
Clarification: When cleaned bed is put into operation, the loss of head through it is 15-30cm and it goes on increasing as impurities are arrested in filter media.

2. The thickness of the suspended matter on top of the sand bed is __________
a) Directly proportional to head loss
b) Inversely proportional to head loss
c) Independent of the head loss
d) Directly proportional to the square of head loss
Answer: a
Clarification: As the thickness of suspended matter on top of the sand bed increases, the head loss is increased. So, it is directly proportional to head loss.

3. When the loss of the head exceeds the static head, the head becomes _____
a) Positive
b) Negative
c) Constant
d) Zero
Answer: b
Clarification: The head becomes negative when the loss of the head through the bed depth exceeds the static head. The negative head is the fall of liquid level in the piezometric tube below the center line of under drainage system.

4. What is the permissible negative head loss of a rapid sand filter?
a) 0.2-1m
b) 0.1-0.5m
c) 0.5-2m
d) 0.8-1.2m
Answer: d
Clarification: The permissible negative head loss of a rapid sand filter is 0.8-1.2m. When the permissible limits are reached, the filter run is terminated and the filter is back washed.

5. Which type of problem is caused in filter due to the accumulation of solids on the top surface of filter media?
a) Clogging
b) Air binding
c) Sand incrustation
d) Sand leakage
Answer: a
Clarification: Clogging of bed is caused due to the accumulation of solids on the top surface of filter media, which results in the formation of mud balls and cracking of the bed.

6. ______ are formed in filters due to insufficient washing of sand grains.
a) Sand boils
b) Mud balls
c) Clogging
d) Bubbles
Answer: b
Clarification: Mud balls are formed in filters due to insufficient washing of sand grains. Mud accumulates on the sand surface and form a dense mat.

7. The cracking of bed is more prominent __________
a) Near the wall junction
b) Outside the wall junction
c) Inside the wall junction
d) On the wall junction
Answer: a
Clarification: The cracking of bed is more prominent near the wall junction which allows the dirty matter to penetrate into filter media which decreases the efficiency of filtration.

8. In which type of filtration problem, layers of gravel are displaced?
a) Clogging
b) Air binding
c) Sand incrustation
d) Sand leakage
Answer: d
Clarification: During Sand leakage, layers of gravel are displaced during back-washing. This can be minimized by proper proportioning of sand and gravel layers.

9. The tendency of jetting can be minimized by __________
a) Carbonating the water
b) Proportioning of layers of sand and gravel
c) Surface washing
d) Control of algae growth in the water
Answer: c
Clarification: The tendency of jetting can be minimized by surface washing. It can also be minimized by the use of an 8cm layer of coarse garnet between fine media and gravel.

10. _______ type of trouble in filter is caused by the released of dissolved air and gases from water.
a) Air binding
b) Clogging
c) Mud balls
d) Jetting
Answer: a
Clarification: Air binding is caused by the released of dissolved air and gases from water to form bubbles which occupy void space of the filter media and the drainage system.

11. How the problem of sand incrustation can be minimized?
a) Carbonating the water
b) Proportioning of layers of sand and gravel
c) Surface washing
d) Control of algae growth in the water
Answer: a
Clarification: The problem of sand incrustation can be minimized by carbonating the water so as to dissolve calcium carbonate that has deposited on sand grains.

Environmental Engineering Multiple Choice Questions on “Activated Carbon Treatment”.

1. Which of the following is used for the control of taste and odor in water?
a) Sedimentation
b) Coagulation
c) Filtration
d) Activated carbon
Answer: d
Clarification: Activated carbon is used for the control of taste and odor, which has resulted from the presence of dissolved gases.

2. Granular activated carbon has a surface area of ____________
a) 100-200m²/g
b) 500-1400m²/g
c) 400-600m²/g
d) 500-900m²/g
Answer: b
Clarification: Granular activated carbon has a surface area of 500-1400m²/g. Higher surface area is the prime consideration in adsorption.

3. _______ is produced by passing a carbonaceous material through a heating mechanism at high temperature.
a) Potassium per-manganate
b) Potassium dichromate
c) Activated carbon
d) Iodine
Answer: c
Clarification: Activated carbon is produced by passing a carbonaceous material through the heating mechanism at high temperature against air, steam, chlorine and flue gases.

4. Which of the following is a carbonaceous material?
a) Charcoal
b) Petroleum
c) Hydrogen sulfide
d) Sodium chloride
Answer: a
Clarification: Charcoal is a carbonaceous material. Various other carbonaceous materials are coke, paper, char and sawdust.

5. Which of the following is not a property of activated carbon?
a) It is impermeable
b) It has many carbon atoms with free valencies
c) It is available in granular as well as powder form
d) It has a prolonged suspension
Answer: a
Clarification: Activated carbon is very porous. It should have prolonged suspension, easily wettable and effective odor absorption capacity.

6. The thickness of the activated carbon filter bed is ____________
a) 10-20cm
b) 30-80cm
c) 75-100cm
d) 40-50cm
Answer: c
Clarification: The thickness of the activated carbon filter bed is between 75 to 100 cm which is supported on 35-50 cm thick graded gravel bed.

7. When activated carbon is applied at more than one point, then it is called ________
a) Dual treatment
b) Split treatment
c) Sludge treatment
d) Carbonaceous treatment
Answer: b
Clarification: The activated carbon in powder form can be applied to the water before, during or after coagulation at more than one point, which is called split treatment.

8. Activated carbon in powder form is applied in the mixing basin.
a) True
b) False
Answer: a
Clarification: Activated carbon in powder form can be applied in the mixing basin either alone or fixed with other chemicals like alum by means of a dry chemical feed machine.

9. Activated carbon can be applied to raw water ______ treatment process.
a) During
b) Ahead of
c) Before
d) After
Answer: b
Clarification: Activated carbon can be applied in various ways like ahead of the treatment process, in the mixing basin or after filtration. Its rate of application is high when the filter is washed.

10. The dose of activated carbon in powdered form is controlled by ____________
a) Chromatography
b) Distillation
c) Threshold odor test
d) MPN test
Answer: c
Clarification: The dose of activated carbon in powdered form is controlled by threshold odor test. For effective use, the dose must be adequate, thoroughly mixed and time of contact should be long.

11. What is the dose of copper sulfate required for the treatment of water?
a) 0.3-0.6ppm
b) 2-6ppm
c) 4-8ppm
d) 10-20ppm
Answer: a
Clarification: Copper sulfate is used for the removal of odor, taste and color from water and the dose required varies from 0.3 to 0.6ppm.

12. There are protozoa present in the water. Its name is Dinobryen. What is the dose of copper sulfate required to kill it?
a) 0.02ppm
b) 0.3ppm
c) 0.5ppm
d) 0.8ppm
Answer: b
Clarification: Dinobryen produces an aromatic, violet and fishy odor and the dose of copper sulfate required to kill it is 0.3ppm.

Environmental Engineering Multiple Choice Questions on “Rational Method”

1. The runoff in cumec by the Rational method is defined by ______________
a) Q = K*A*I*R
b) Q = (K+A+I) *R
c) Q = (K+A) *R
d) Q = A*I*R
Answer: a
Clarification: According to the Rational method, the storm water or runoff is defined by Q = K*A*I*R where, ‘K’ is a constant, ‘A’ is the catchment area in hectares,’I’ is the impermeability factor and ‘R’ is the intensity of rainfall in mm per hour.

2. The value of the factor K in finding the storm water flow by Rational method is ____________
a) 100
b) 160
c) 1
d) 1/360
Answer: d
Clarification: According to the Rational method, the storm water or runoff is defined by
Q = K*A*I*R where, K is a constant and K = 1/360,
So, Q = A*I*R/360.

3. _______ is defined as the percentage of rain water in the form of runoff.
a) Storm water flow
b) Coefficient of permeability
c) Impermeability factor
d) Coefficient of consolidation
Answer: c
Clarification: Impermeability factor is defined as the percentage of rain water in the form of runoff. The storm water flow depends on the imperviousness of the surface and if it is more, more runoff takes place.

4. The impermeability factor is also called as ____________
a) Coefficient of impermeability
b) Runoff coefficient
c) Coefficient of permeability
d) Precipitation factor
Answer: b
Clarification: The impermeability factor is also called as runoff coefficient and it includes Kuichling’s impermeability factor and Fruhlings factor.

5. Which of the following surface has a maximum Kuichling’s impermeability factor?
a) Gravel road
b) Water tight roof surface
c) Unpaved surface
d) Macadamized road ways
Answer: b
Clarification: The water tight roof surface has maximum Kuichling’s impermeability factor with a magnitude of 0.7 to 0.95 while gravel road, unpaved surface and macadamized road ways have < 0.7.

6. Which of the following locality has a minimum Fruhlings factor?
a) Business area
b) An area closely built up
c) Area with 50% attached and detached houses
d) Extremely suburban area
Answer: d
Clarification: Extremely suburban area having 20% to 60/5 parking and widely detached houses has a minimum Fruhlings factor with a magnitude of 0.35 while business area, closely built up area and area with 50% attached and detached house have magnitude > 0.35.

7. If the type of surface is of the most densely populated portion of the city, what is the value of Kuichling’s impermeability factor?
a) 0.14
b) 0.30
c) 0.80
d) 0.45
Answer: c
Clarification: The value of Kuichling’s impermeability factor for a surface of the most densely populated portion of the city lies between 0.7 to 0.9.

8. The value of Fruhlings factor for suburban locality is ______
a) 0.10
b) 0.20
c) 0.50
d) 0.80
Answer: c
Clarification: If the type of locality is suburban area having detached houses, the value of Fruhlings factor lies in the range of 0.45 to 0.55.

9. The storm frequency for a peripheral residential area is ___ a year.
a) Once
b) Twice
c) Thrice
d) 4 times
Answer: b
Clarification: The frequency of storm for which the sewer is to be designed for a peripheral residential area is twice a year.

10. The storm frequency for a peripheral commercial area is ____________
a) Once a year
b) Twice a year
c) Once in 2 years
d) Once in a month
Answer: c
Clarification: The commercial and higher priced area more subject to less storm frequency than the residential area and its storm frequency is once in 2 years.

11. Shorter the duration of rainfall ____ will be the rainfall intensity.
a) Lesser
b) Constant
c) Slightly lesser
d) Greater
Answer: d
Clarification: The intensity of rainfall is inversely proportional to the duration period, so the shorter the duration of rainfall, greater will be the rainfall intensity.

12. When the storm occurs once a year, the rainfall intensity R is ____________
a) R = 300/t^0.625
b) R = 150/t^0.625
c) R = 150/t²
d) R = 300/t²
Answer: b
Clarification: When the storm occurs once a year, the rainfall intensity R is given by R = 150/ t ^0.625 Where, t is the duration of storm in minutes.

13. The Kuichlings formula when the storm occurs once in 10 years is ____________
a) R = 2667/(t + 50)
b) R = 260/(t + 20)
c) R = 2667/(t + 20)
d) R = 260/t
Answer: c
Clarification: According to Kuichling, when the storm occurs once in 10 years, the rainfall intensity R is given by R = 260/(t + 20) and when it occurs once in 15 years, it is given by R = 3048/(t + 20) where t is the duration of storm in minutes.

14. ________ is the time required by flood discharge to reach the maximum limit.
a) Storm frequency
b) Run-off time
c) Detention period
d) Time of concentration
Answer: d
Clarification: The time of concentration is defined as the longest time required for a drop of water to flow from the farthest point of drainage area to the point of concentration.

15. The maximum runoff occurs when the duration of storm equals the time of concentration.
a) True
b) False
Answer: a
Clarification: It is because if duration of storm is shorter than time of concentration, then whole catchment will not be the contributing water, resulting in lesser runoff whereas if duration of storm exceeds the time of concentration, then rainfall intensity will be less, resulting in lesser runoff.

Environmental Engineering Multiple Choice Questions on “Disposal of Sewage”.

1. Which of the following is a prime lake pollutant?
a) Iodine
b) Phosphorous
c) Potassium
d) Sodium
Answer: b
Clarification: Phosphorous is a prime lake pollutant that promotes the algal bloom and destroys the quality and appearance of a lake.

2. The turbulence decreases the DO content of water.
a) True
b) False
Answer: b
Clarification: The turbulence increases the DO content of water, however, beyond a certain limit, it scours the sediments placed at the bottom.

3. The dilution factor is expressed by _____________
a) Volume of diluted sample + Volume of sewage
b) Volume of diluted sample / Volume of sewage
c) Volume of diluted sample – Volume of sewage
d) Volume of diluted sample* Volume of sewage
Answer: b
Clarification: The dilution factor is the ratio of volume of diluted sample of water to the volume of sewage. It is used in finding the BOD of water.

4. The tolerance limit of BOD of sewage to be disposed on land is ____________
a) 100ppm
b) 200ppm
c) 500ppm
d) 400ppm
Answer: c
Clarification: The tolerance limit of BOD of sewage to be discharged into sea water is 100ppm while to be disposed on land is 500ppm.

5. The tolerance limit of pH value of sewage to be discharged into sea water is ____________
a) 1-5ppm
b) 2-9ppm
c) 5.5-9ppm
d) 6-10ppm
Answer: c
Clarification: The tolerance limit of pH value of sewage to be discharged into sea water or to be disposed on land is between 5.5 and 9ppm.

6. The dilution factor is 400. What should be the type of treatment given to the water?
a) Preliminary treatment
b) Sedimentation, Flocculation
c) Complete treatment
d) No treatment
Answer: a
Clarification: When the dilution factor lies between 300 and 500, then preliminary treatment is given to the water.

7. The tolerance limit of oil and grease of sewage to be disposed on land is ____________
a) 40ppm
b) 30ppm
c) 20ppm
d) 10ppm
Answer:b
Clarification: The tolerance limit of oil and grease of sewage to be disposed on land is 30ppm while on sea water is 20ppm.

8. The minimum depth to which sewage should be discharged of sea water is ____________
a) 0.5m
b) 1m
c) 2m
d) 3m
Answer: d
Clarification: The minimum depth to which sewage should be discharged of sea water is 3m to avoid marine pollution.

9. The tolerance limit of COD of sewage to be discharged in sea water is ____________
a) 250ppm
b) 100ppm
c) 40ppm
d) 20ppm
Answer: a
Clarification: The tolerance limit of COD of sewage to be discharged in sea water and on land for irrigation purpose is 250ppm.

Environmental Engineering online test on “Digestion of Sludge, Sludge Digestion Tank”.

1. How many stages are there in the sludge digestion process?
a) 2
b) 3
c) 4
d) 5
Answer: b
Clarification: The sludge digestion process consists of acid fermentation, acid regression and alkaline fermentation.

2. The form of sludge which is free from pathogenic bacteria is ___________
a) Undigested sludge
b) Digested sludge
c) Primary sludge
d) Supernatant liquor
Answer: b
Clarification: The digested sludge is free from pathogenic bacteria. It has the behavior of rich humus soil.

3. The BOD of supernatant liquor in a sludge digestion process is ____ ppm.
a) 3000
b) 0
c) 1000
d) 250
Answer: a
Clarification: The range of BOD of supernatant liquor in a sludge digestion process is between 2000 and 3000 ppm. It is a form of sludge that is obtained in the sludge digestion process.

4. Which of the following is correct regarding pH in different stages of the sludge digestion process?
a) Acid fermentation > Acid regression > Alkaline fermentation
b) Acid regression > Acid fermentation > Alkaline fermentation
c) Acid fermentation < Acid regression < Alkaline fermentation
d) Acid fermentation < Acid regression > Alkaline fermentation
Answer: c
Clarification: The pH value in Alkaline fermentation stage is 7.5 whereas in Acid regression and Acid fermentation stage, the pH>7, having the least in acid fermentation stage.

5. Which gas evolves the most in the sludge digestion process?
a) SO₂
b) CO₂
c) N₂
d) CH₄
Answer: d
Clarification: Methane gas evolves the most during the sludge digestion process by approximately 70% of the total gas evolved.

6. Which of the following is incorrect about aerobic digestion in the sludge digestion process?
a) It has a low capital cost
b) It is easier to manage.
c) It has high residual energy
d) It decreases the BOD
Answer: c
Clarification: The residual energy in aerobic digestion is very less in comparison to anaerobic digestion.

7. The color of digestive sludge is ___________
a) Blue
b) Black
c) Brown
d) Gray
Answer: b
Clarification: The color of the digestive sludge is black. It has an inoffensive odor.

8. Which of the following is correct regarding anaerobic digestion in the sludge digestion process?
a) It contains high amount of biomass
b) It is a low energy process
c) It causes infertility in soil
d) Aerobic bacteria oxidize the organic matter
Answer: b
Clarification: Anaerobic digestion is a low energy process that contains low amount of biomass and where both facultative and anaerobic bacteria solubilize the organic matter.

9. The maximum temperature at which thermophilic microorganisms remain active in sludge digester is ___________
a) 60^oC
b) 40^oC
c) 30^oC
d) 20^oC
Answer: a
Clarification: The maximum and minimum temperature at which thermophilic microorganisms remain active in sludge digester are 60^oC and 40^oC respectively.

10. Which of the following is obtained in the secondary tank in two stage sludge digester?
a) Partially digested sludge
b) Partially digested sludge and supernatant liquor
c) Digested sludge and supernatant liquor
d) supernatant liquor
Answer: c
Clarification: In two stage sludge digester, the partially digested sludge is obtained in primary tank, whereas digested sludge is obtained in the secondary tank along with supernatant liquor.

11. The high rate sludge digestion tanks are used when the capacity of the tank is ____ million liters per day.
a) 1
b) 3
c) 4
d) 10
Answer: c
Clarification: High rate digesters are used when the capacity of tank is 4 million litres per day. Complete mixing and uniform feeding of raw sludge take place in high rate digesters.

12. In which of the following, both primary and secondary tanks are used?
a) Two stage sludge digesters
b) Single stage sludge digesters
c) Low rate digesters
d) High rate digesters
Answer: a
Clarification: In two stage sludge digesters, the sludge is passed in the primary tank for 7 days and then it is passed in the secondary tank followed by the removal of residual matter.

13. The minimum size of sludge digestion tank is ___________
a) 0.5m
b) 1m
c) 2m
d) 3m
Answer: d
Clarification: The minimum size of sludge digestion tank is 3m. They are cylindrical in shape with a funnel shaped at the bottom.

14. The range of temperature at which mesophilic microorganism becomes active in sludge digester is ___________
a) 30-40^oC
b) 10-40^oC
c) 20-50^oC
d) 20-40^oC
Answer: d
Clarification: The mesophilic microorganism becomes active at 20-40^oC in the sludge digester. The rate of digestion, increases with increase in temperature.

15. The sludge digestion process is independent of which of the following?
a) Temperature of sludge
b) pH of sludge
c) Shape of tank
d) Mixing of sludge
Answer: c
Clarification: The sludge digestion process depends on the temperature of sludge, pH conditions and mixing of sludge and is independent of shape of tank.

To practice all areas of Environmental Engineering for online tests, .

Environmental Science Multiple Choice Questions on “Air Pollution – Sources – 2”.

1. What is the residence time (average time a particle is active in a given system) of carbon monoxide?
a) 11-15 years
b) 0.1-0.3 years
c) 0.5 years
d) Few minutes
Answer: b
Clarification: The residence time is the average time a particle remains active in a given system.

2. Which of the following gases has the highest affinity for blood haemoglobin?
a) Carbon dioxide
b) Oxygen
c) Carbon monoxide
d) Nitrogen
Answer: c
Clarification: It has 200 times greater affinity for haemoglobin than oxygen.

3. At what concentration can the taste and smell of sulphur dioxide be detected?
a) 1000-2000ppm
b) 11-30ppm
c) 500-700ppm
d) 0.1-0.3ppm
Answer: d
Clarification: Sulphur dioxide has a pungent odour which can be detected in even in very minute concentrations in the range of 0.1 – 0.3 parts per million.

4. Which is the major source for sulphur dioxide?
a) Volcanic eruptions
b) Coal and crude oil combustion
c) Burning of petrol
d) Sewage treatment process
Answer: b
Clarification: Though emission of sulphur dioxide is peak during volcanic eruptions, its major source is during combustion of crude oil and coal for heat and power generation.

5. Which is the largest source for production of nitrous oxide?
a) Chemical industry
b) Fertiliser industry
c) Fossil fuel combustion
d) Bacterial action
Answer: d
Clarification: Denitrifiers (such as ammonia oxidising bacteria) in aerobic conditions serve as the major producer for nitrous oxide.

6. Pesticides also contribute to air pollution along with polluting underground reservoirs.
a) True
b) False
Answer: a
Clarification: The method of spraying pesticides leads to small portion of pesticide serving as an air pollutant. Some pesticides evaporate from soil and pollute the air. Eg. DDT.

7. Which of the following are sources to fluorine air pollution?
a) Coal combustion
b) Steel industries
c) Phosphate fertiliser manufacturing
d) All of the mentioned
Answer: d
Clarification: Phosphate rock (Fluorapatite) is used for manufacturing of fertilisers and contributes to fluorine air pollution along with steel industries and coal combustion.

8. Which is/are the most significant air-borne allergen(s)?
a) Fungi
b) Pollen
c) Soot
d) All of the mentioned
Answer: b
Clarification: Pollen grains are the most significant air-borne allergen with an indestructible outer membrane, and are known to cause severe respiratory problems when inhaled.

9. Which of the following is a source for boron air pollution?
a) Rockets and jets
b) Automobiles
c) Soap industries
d) Refrigerants
Answer: a
Clarification: Borane is mixed with petroleum and used as a fuel in rockets and jets which when combusted releases boron which causes air pollution.

10. Which are the sources of arsenic pollution?
a) Coal and petroleum
b) Detergents and pesticides
c) Mine tailings
d) All of the mentioned
Answer: d
Clarification: Arsenic is a human carcinogen and is emitted during the combustion of coal and petroleum. It is also found in detergents, pesticides and mine tailings.

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