Category: Environmental Engineering Objective Questions

Environmental Engineering Multiple Choice Questions on “Sludge Thickening, Sludge Dewatering”.

1. The design solid surface loading in an activated sludge process is ___________
a) 10 kg/m²/day
b) 25 kg/m²/day
c) 15 kg/m²/day
d) 35 kg/m²/day
Answer: b
Clarification: The design solid surface loading during a gravity thickening process in an activated sludge plant lies between 25 to 30 kg/m²/day.

2. Which of the following plant nutrient is not found in municipal sewage?
a) Arsenic
b) Phosphorous
c) Potassium
d) Nitrogen
Answer: a
Clarification: Potassium, Phosphorous and Nitrogen are found in municipal sewage having maximum plant nutrient concentration of 3.3% of total municipal waste as nitrogen.

3. The design pressure of ____ is applied on pressure type flotation device.
a) 1kg/cm²
b) 2kg/cm²
c) 3kg/cm²
d) 6kg/cm²
Answer: c
Clarification: In pressure type flotation device, 3-5kg/cm² pressure is applied to the sludge thickening process.

4. The design Hydraulic loading rate of the gravity thickener is _______ m³/m²/day.
a) 20
b) 39
c) 40
d) 85
Answer: a
Clarification: The range of design Hydraulic loading rate of the gravity thickener is 20-25m³/m²/day.

5. Which of the following process is not involved in sludge thickening?
a) Gravity thickening
b) Vacuum filter
c) Air flotation
d) Centrifugation
Answer: b
Clarification: The process involved in sludge thickening are gravity thickening, air flotation and centrifugation.

6. 7% of solids concentration of thickened sludge is obtained from gravity thickener. What is the type of sludge?
a) Primary sludge
b) Secondary sludge
c) Tertiary sludge
d) Activated sludge
Answer: d
Clarification: When the thickened sludge, solid concentration is between 7-9, the type of sludge obtained from gravity thickner is activated.

7. Which of the following is not used for drying of sludge?
a) Multiple effect evaporation
b) Dual effect evaporation
c) Rotary dryer
d) Spray dryer
Answer: b
Clarification: The process used for drying of sludge is multiple effect evaporation, rotary dryer, spray dryer and flash dryer.

8. In which of the following method, the sludge is rotated for dewatering process?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter
Answer: a
Clarification: In the centrifugation process, the force is applied so that rotation of sludge takes place which helps in the dewatering of sludge.

9. The dewatered sludge cannot be disposed by ___________
a) Composting
b) Heat drying
c) Acid fermentation
d) Incineration
Answer: c
Clarification: Acid fermentation is a sludge digestion process and composting, heat drying and incineration are the methods of disposal of dewatered sludge.

10. In which of the following process, the sludge is dried and disposed in land?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter
Answer: c
Clarification: Good amount of dried solids is produced by drying bed process and they are commonly used in the sludge dewatering process due to their low cost and better efficiency.

11. Which of the following is not a drying bed?
a) Wedwire beds
b) Artificial media
c) Filter press
d) Conventional sand
Answer: c
Clarification: There are 5 types of drying beds, namely wedwire beds, artificial media, conventional sand, paved and vacuum assisted drying bed.

12. Which of the following is not suitable for dewatering of raw sludge?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter
Answer: b
Clarification: In drying lagoon, if raw sludge is used that contains supernatant liquor, foul smell and fly nuisance occur in the dewatering process.

13. Which of the following is not a part of dewatering process?
a) Drying bed
b) Air flotation
c) Vacuum filter
d) Drying lagoon
Answer: b
Clarification: Air flotation is a part of the sludge thickening process and drying bed, drying lagoon and vacuum filter are part of the dewatering process.

Environmental Science Multiple Choice Questions on “Air Quality”.

1. Which plant helps in detection of pollution from automobile exhaust?
a) Neem
b) Tulsi
c) Lichen
d) Lettuce
Answer: b
Clarification: The tulsi plant is used as a bio-indicator to detect pollution due to exhaust from automobiles.

2. Which of the following plants aid as an indicator to ozone pollution?
a) Tomato
b) Tobacco
c) Watermelon
d) All of the mentioned
Answer: d
Clarification: Tomato, tobacco and watermelon are highly sensitive to ozone, and thereby contribute to indicating ozone pollution.

3. Greater the Air Quality Index of a region, more polluted is the air.
a) True
b) False
Answer: a
Clarification: Air Quality Index is a number used to indicate the severity of air pollution in a given region. Hence more the AQI more is the pollution.

4. How many parameters are taken into consideration when measuring air quality, in India?
a) 4
b) 3
c) 8
d) 9
Answer: c
Clarification: Recently, under the Swachh Bharat Abhiyan, the government increased the number of indicators for measuring air quality from 3 to 8, thereby making it more inclusive.

5. Which of the following pollutants are considered when measuring air quality?
a) CO, O₃, PM_2.5
b) NH₃, PM₁₀, Pb
c) NO₂, SO₂
d) All of the mentioned
Answer: d
Clarification: All the mentioned 8 pollutants’ concentrations over a 24 hour period are considered when measuring air quality.

6. What range of air quality index has the most severe impact on human health?
a) 101-200
b) 201-300
c) 301-400
d) 401-500
Answer: d
Clarification: Air quality is regarded as severe when it has an index of 401-500, and affects even healthy people and impacts them even during simple activity.

7. Hazardous pollutants are those pollutants for which air quality standards have been devised.
a) True
b) False
Answer: b
Clarification: Hazardous pollutants do not have a defined air quality standard but contribute to severe health damage and mortality rate.

8. Which of the following devices is NOT used to control particulate emissions?
a) Electrostatic precipitator
b) Bag filters
c) Catalytic converters
d) All of the mentioned
Answer: c
Clarification: Catalytic converters are used to remove vapour phase and gaseous pollutants whereas, electrostatic precipitator and bag filters are used for particulate removal.

9. Which of the mentioned devices are used for removing vapour phase/ gaseous pollutants?
a) Absorption towers
b) Catalytic converters
c) Thermal oxidisers
d) All of the mentioned
Answer: d
Clarification: Absorption tower, catalytic converters and thermal oxidisers filter out harmful gaseous pollutants from the air.

.

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

1. The size of suspended solids lies in the range of ________
a) 10^-3 – 10^-6 mm
b) 10³ – 10⁶ mm
c) 10^-1 – 10^-3 mm
d) 10¹ – 10³ mm
Answer: c
Clarification: Size of suspended solids – 10^-1 – 10^-3 mm, size of colloidal solids – 10^-3 – 10^-6 mm, size of dissolved solids < 10^-6 mm.

2. Suspended solids are measured by which of the following?
a) Turbidity rod
b) Gravimetric test
c) Chromatography
d) Jackson’s turbidity meter
Answer: b
Clarification: Turbidity rod and Jackson’s turbidity meter is used to find turbidity whereas chromatography is used to detect odour. Hence b is the correct answer.

3. The maximum permissible limit for suspended solids is ____________
a) 10 mg/l
b) 20 mg/l
c) 30 mg/l
d) 40 mg/l
Answer: c
Clarification: The maximum permissible limit for suspended solids is 30mg/l for testing waste water which is set by the Environmental Protection Agency (EPA).

4. Identify the correct relation between the following?
a) Dissolved solid = Total solid + Suspended solid
b) Dissolved solid = Total solid – Suspended solid
c) Total solid = Dissolved solid / Suspended solid
d) Dissolved solid = Suspended solid – Total solid
Answer: b
Clarification: Dissolved solid is the difference between total solid and suspended solid. Suspended solid is non-filterable solid whereas dissolved solid is filterable solid.

5. Which method is used to measure the color of water?
a) Gravimetric analysis
b) Chromatography
c) Tintometer method
d) Hydrometer analysis
Answer: c
Clarification: The colors in water are measured by Tintometer method. It is measured on Burgess scale or cobalt scale by Nessler’s tube.

6. 1 TCU (True Color Unit) is equivalent to _____
a) The color produced by 1 g of platinum cobalt
b) The color produced by 1 mg of platinum cobalt
c) The color produced by 1 mg of platinum cobalt in 1L of distilled water
d) The color produced by 1 mg of platinum cobalt in 1mL of distilled water
Answer: c
Clarification: 1 TCU (True Color Unit) is equivalent to color produced by 1 mg of platinum cobalt in 1L of distilled water. The true color unit is also called a Hazen unit.

7. The range for threshold odour number is __________
a) 0-3
b) 1-5
c) 1-3
d) 0-5
Answer: c
Clarification: The maximum value of Threshold odour number is 3 and its range is 1-3. The threshold odour number is used to measure the intensity of taste and odour.

8. Threshold odour number testing is preferred in hot water.
a) True
b) False
Answer: b
Clarification: TON testing is preferred in cold water as in hot water due to increase in temperature, taste and odour can change.

9. One JTU is equivalent to turbidity produced by __________
a) 1mg of fine silica dissolved in 1L of distilled water
b) 1g of fine silica dissolved in 1L of distilled water
c) 1g of fine silica dissolved in 1ml of distilled water
d) 1mg of fine silica dissolved in 1ml of distilled water
Answer: a
Clarification: 1 JTU is equivalent to turbidity produced by 1mg of fine silica dissolved in 1L of distilled water. It is called as Jackson’s turbidity unit and is based on the absorption principle.

10. If the PO value is 6, what does it imply?
a) No perceptible odour
b) Very faint odour
c) Very distinct odour
d) Extremely strong odour
Answer: d
Clarification: The PO value indicates the odour intensity. 6 is the maximum PO value and it indicates extremely strong odour.

11. The range of temperature of water that is required to do the temperature test is __________
a) 10-25⁰C
b) 0-25⁰C
c) 10-30⁰C
d) 20-30⁰C
Answer: a
Clarification: To do the temperature test of water, its temperature should be between 10⁰C and 25⁰C and the temperature higher than 25⁰C is considered objectionable.

12. Which of the following statement is wrong regarding turbidity?
a) It is an extent to which light is absorbed by particles in the water
b) It is expressed in ppm
c) It depends on the fineness of particle present in the water
d) Turbidity rod is a laboratory method to measure turbidity
Answer: d
Clarification: Turbidity rod is a field method not a laboratory method to measure turbidity.

13. The permissible limit of turbidity of domestic water is ____ ppm.
a) 5-10
b) 1-5
c) 10-50
d) 10-30
Answer: a
Clarification: According to WHO, the permissible limit for drinking water is 5NTU.

14. What is the full form of NTU in context with turbidity?
a) Number of transfer unit
b) Neurological turbidity unit
c) Nephelometric turbidity unit
d) Network terminal unit
Answer: c
Clarification: The value of turbidity measured by nephelometer is expressed in terms of NTU. Sometimes, it is referred as FTU or Formazin turbidity unit.

15. When depth of insertion of turbidity rod increases, the reading in the turbidity rod ___
a) Decreases
b) Increases
c) First decrease, then increase
d) Remains constant
Answer: a
Clarification: Turbidity rod is inserted inside the water and the reading at which needle becomes invisible gives the turbidity.

Environmental Engineering Multiple Choice Questions on “Pressure Filter”.

1. In which of the following filter, water is passed under higher pressure?
a) Slow sand filter
b) Rapid sand filter
c) Dual media filter
d) Pressure filter
Answer: d
Clarification: The pressure filter is a type of rapid sand filter kept in a closed container where water is passed under higher pressure.

2. What is the range of pressure in pressure filter?
a) 1-5 kg/cm²
b) 2-5 kg/cm²
c) 3-7 kg/cm²
d) 1-8 kg/cm²
Answer: c
Clarification: The range of pressure of pressure filter is 3-7 kg/cm², which is done by pumping either in horizontal or vertical type pressure filter.

3. The diameter of the vertical type pressure filter is __________
a) 2-2.5 m
b) 1 m
c) 5 m
d) 10m
Answer: a
Clarification: The diameter of the vertical type pressure filter is 2-2.5 m and its length varies from 2.5 to 8m.

4. Filtration operation in pressure filter is same as in rapid sand filter.
a) True
b) False
Answer: b
Clarification: In pressure filter, the coagulated water is applied to filter directly without any mixing or flocculation process, whereas in rapid sand filter, the flocculation takes place after coagulation and then it is applied to the filtration process.

5. The effective size of a pressure sand filter is ______
a) 0.45mm
b) 0.7mm
c) 0.8mm
d) 0.9mm
Answer: a
Clarification: The effective size of a pressure sand filter lies in the range of 0.35-0.6mm and its common value is 0.45mm.

6. What is the value of uniformity coefficient in a pressure sand filter?
a) 1
b) 1.5
c) 2
d) 2.5
Answer: b
Clarification: The value of uniformity coefficient in a pressure sand filter lies between 1.2 and 1.7 and its common value is 1.5.

7. The thickness of sand bed of a pressure filter is _____ cm.
a) 10-20
b) 20-30
c) 30-50
d) 50-60
Answer: d
Clarification: The thickness of sand bed of a pressure filter is 50-60 cm, whereas the gravel layers of pressure filter are same as a rapid sand filter.

8. Which type of filter is used in treating swimming pool water?
a) Slow sand filter
b) Rapid sand filter
c) Dual media filter
d) Pressure filter
Answer: d
Clarification: The pressure filter is used for treating swimming pool water. It is also used for clarifying softened water at industrial plants.

9. The under drainage system in pressure consists of __________
a) Central drains connected to lateral drain
b) Wheeler system
c) Wagner system
d) Pipe grids, false bottom
Answer: d
Clarification: The under drainage system in pressure consists of pipe grids, false bottom and the washing of filter media is accomplished by reversing the flow by manipulating the valves in the pipe.

10. Consider the following statements regarding pressure filter.
i. It is easy to inspect the under drainage system
ii. It is not possible to provide time for chlorination in direct supply from it
iii. It is not possible to observe the degree of back washing and the agitation process
Which of the above statement is correct?
a) i only
b) ii, iii
c) i, ii, iii
d) i, iii
Answer: b
Clarification: It is difficult to inspect, replace and clean the sand, gravel and under drainage system of pressure filter.

11. The rate of filtration of pressure filtration is ______ l/m²/hour.
a) 1000-5000
b) 5000-10000
c) 6000-8000
d) 6000-15000
Answer: d
Clarification: The rate of filtration of pressure filtration is 6000-15000l/m²/hour due to which it is used for treatment of swimming pool water.

Environmental Engineering Multiple Choice Questions on “Types of Pumps”.

1. Which of the following is the correct classification of pumps?
a) Physical principle of operation
b) Mechanical principle of operation
c) Chemical principle of operation
d) Biological principle of operation
Answer: b
Clarification: The pumps are classified on the basis of the mechanical operation of the principle, type of power and type of service.

2. Displacement pump is classified on the basis of _____________
a) Mechanical operation of principle
b) Type of power
c) Type of service
d) Efficiency
Answer: a
Clarification: Mechanical principle of operation is classified into displacement, centrifugal, air lift and miscellaneous pumps.

3. Which of the following pump is classified based on the type of service?
a) Displacement pump
b) Centrifugal pump
c) Deep well pump
d) Electric driven pump
Answer: c
Clarification: Pumps are of four types on the basis of type of service- low lift, high lift, deep well and booster pump.

4. Which of the following pump is based on the type of power?
a) Low lift pump
b) High lift pump
c) Air lift pump
d) Steam engine pump
Answer: d
Clarification: There are 3 types of pumps on the basis of type of power. They are – steam engine, diesel engine and electrically driven pump.

5. A booster pump is based on _____________
a) Mechanical operation of principle
b) Type of power
c) Type of service
d) Efficiency
Answer: c
Clarification: Booster pump is classified on the basis of type of service. They are used for increasing gas pressure, transferring high pressure gas, scavenging and charging gas cylinders.

6. Consider the following statements.
i. Capacity of the pump
ii. Number of pump units
iii. Discharge condition
The selection of a particular type of pump depends on which of the following?
a) i, ii, iii
b) i only
c) ii, iii
d) i, iii
Answer: a
Clarification: The selection of a particular type of pump depends on the capacity of pump, number of pump units, suction and discharge condition, type of drive, initial and final cost, lift, flexibility of operations and floor space requirements.

7. The centrifugal pump has a ______ flow.
a) Variable
b) Uniform
c) Continuous
d) Constant
Answer: c
Clarification: The centrifugal pump has a continuous flow. It does not give a constant discharge under variable head.

8. The speed at which the centrifugal pump runs (in r.p.m) is _____________
a) 200
b) 300
c) 500
d) 1200
Answer: c
Clarification: The speed at which the centrifugal pump runs lies in the range of 500 to 100 rates per minute (r.p.m). The direct connection of pump with driving machines is possible.

9. The maximum efficiency of a centrifugal pump is _____________
a) 50%
b) 60%
c) 85%
d) 100%
Answer: c
Clarification: The efficiency of the centrifugal pump lies between 40% and 85%. It depends on the head and discharge of the pump.

10. Based on the type of casing, the centrifugal pump is divided into _____ types.
a) 2
b) 3
c) 4
d) 5
Answer: a
Clarification: Based on the type of casing, the centrifugal pump is divided into the volute pump and turbine pump.

Environmental Engineering Multiple Choice Questions on “Hydraulic Elements of Circular Sewers”.

1. Which of the following is incorrect regarding circular sewer?
a) It is easily manufactured
b) It offers more opportunities for deposits
c) It is the most economical section
d) It has uniform curvature
Answer: b
Clarification: The circular section has uniform curvature, so it offers less opportunities for deposits.

2. A circular section of sewer gives _______ area for a given perimeter.
a) Small
b) Large
c) Minimum
d) Maximum
Answer: d
Clarification: A circular section of sewer gives a maximum area for a given perimeter and gives the greatest hydraulic mean depth when running full or half.

3. What is the wetted perimeter of a circular section of sewer?
a) (22/7) *D²
b) (22/7) *D
c) (22/7) *D²
d) (22/7)² *D
Answer: b
Clarification: The wetted perimeter of a circular section of sewer running full is (22/7) *D where D is the internal diameter of circular sewer.

4. The hydraulic mean depth of a circular section running full is __________
a)`D
b) D/2
c) D²
d) D/4
Answer: d
Clarification: The hydraulic mean depth, R = Area of cross section / Wetted perimeter
= ((22/7) *D²/4) / (22/7) *D
= D/4.

5. The proportional depth of a circular sewer running partially half is __________
a) (1-cosK/2)
b) (1/2) * (1-sinK/2)
c) (1/2) * (1-cosK/2)
d) (1-cosK/2)²
Answer: c
Clarification: Depth of flow d = (D/2) * (1-cosK/2)
Proportional depth = Depth of flow d / Diameter of section D = (D/2) * (1-cosK/2) / D
= (1/2) * (1-cosK/2).

6. The proportional perimeter of a circular sewer running partially half where K is the central angle subtended at a circular section of sewer is __________
a) K/360^o
b) K/90^o
c) K/270^o
d) K/180^o
Answer: a
Clarification: Proportional perimeter of a circular sewer running partially half =
(22/7) *D*K/360^o / ((22/7) *D) = K/360^o.

7. The diameter of the circular sewer is 0.2m. The desired depth of flow is __________
a) 2/3 of the circular section of sewer
b) 1/3 of the circular section of sewer
c) 1/2 of the circular section of sewer
d) 1/4 of the circular section of sewer
Answer: c
Clarification: When the diameter of the sewer is up to 0.4m, they are designed to flow at 1/2 depth.

8. The diameter of a circular sewer is 0.8m. The desired depth of flow is __________
a) 2/3 of the circular section of sewer
b) 1/3 of the circular section of sewer
c) 1/2 of the circular section of sewer
d) 1/4 of the circular section of sewer
Answer: a
Clarification: When the diameter of the sewer is between 0.4m and 0.8m, they are designed to flow at 2/3 depth.

9. A circular sewer having 0.4m diameter is flowing with velocity 2m/Sec. If the gradient of sewer is 1 in 90. Find the value of Chezy’s coefficient?
a) 10
b) 30
c) 60
d) 40
Answer: d
Clarification: Hydraulic mean depth, R = D/4 = 0.4/4 = 0.1m
Slope of sewer S = 1/100, velocity V = 1m/Sec
According to Chezy’s formula, V = C (RS) ^1/2 = C* (0.1/90) ^1/2 = C/30
C = V*30 = 2*30 = 60.