Category: Environmental Engineering Objective Questions

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

1. The temperature of sewage increases. What will be the effect on the dissolved oxygen in sewage?
a) Remains constant
b) Increase
c) Decrease
d) No effect
Answer: c
Clarification: The temperature and dissolved oxygen are inversely proportional to each other.

2. What is the minimum quantity of dissolved oxygen that should be present in the treated sewage?
a) 6ppm
b) 4ppm
c) 1ppm
d) 10ppm
Answer: b
Clarification: At least, 4ppm of dissolved oxygen should be present in treating sewage otherwise, fishes will die due to lack of dissolved oxygen.

3. The presence of which of the following in sewage indicates nitrogen content before decomposition of sewage?
a) Nitrites
b) Nitrates
c) Free ammonia
d) Albuminoid nitrogen
Answer: d
Clarification: The presence of Albuminoid nitrogen in water indicates the decomposition of sewage has not taken place.It nitrogen is also called as organic nitrogen.

4. The presence of free ammonia in sewage represents ____________
a) Air pollution
b) Old pollution
c) Recent pollution
d) Water pollution
Answer: c
Clarification: The presence of free ammonia in sewage represents recent pollution. Which can be removed from wastewater by the nitrification process.

5. Which chemical is used for the titration of waste water for finding its chloride content?
a) Potassium chloride
b) Sodium chloride
c) Potassium chromate
d) Potassium dichromate
Answer: c
Clarification: Potassium chromate is used for the titration of waste water with silver nitrate solution for finding the chloride content.

6. The type of solids which floats in sewage is __________
a) Suspended solids
b) Settleable solids
c) Dissolved solids
d) Total solids
Answer: a
Clarification: The suspended solids float in sewage. 1000kg of sewage contain 0.112 kg of suspended solids.

7. The presence of which of the following indicates old pollution?
a) Nitrates
b) Nitrites
c) H₂S
d) Sulfates
Answer: d
Clarification: The presence of nitrates indicates the old pollution. It also means that the nitrogen is fully oxidized in sewage.

8. ________ is used to find the D.O content of sewage.
a) Winkler method
b) Chromatography
c) Kjeldahl method
d) Olfactometer
Answer: b
Clarification: Wrinkler method is used to find the D.O content of sewage where the D.O content is proportional to the titration of iodine with S2O32- solution.

9. The permissible dose of chloride in domestic sewage is __________
a) 120ppm
b) 10ppm
c) 1ppm
d) 250ppm
Answer: a
Clarification: Domestic sewage includes waste from kitchen, laundry, toilet, bathroom, etc., which contain higher amount of chloride content, so the permissible dose of 120ppm is kept for domestic sewage.

10. Imhoff cone is used to measure the _______
a) Suspended solids
b) Settleable solids
c) Dissolved solids
d) Total solids
Answer: b
Clarification: Imhoff cone is used to measure the settleable solids where wastewater is allowed to stand for a specific time, solids get settled down and the readings are taken through the graduations on the cone.

11. The decomposition of sewage takes place, causing a pungent smell. Which of the following causes the pungent smell?
a) CO₂
b) H₂SO₄
c) HCL
d) H₂S
Answer: d
Clarification: The decomposition of sewage leads to the formation of sulfur compound like H₂S which produces a pungent smell.

12. Which of the following disease is caused due to lack of nitrates?
a) Diphtheria
b) Methemoglobinemia
c) Tuberculosis
d) Meningitis
Answer: b
Clarification: Methemoglobinemia is a disease caused due to lack of nitrates in the body where the concentration of methemoglobin in red blood cells becomes greater than 1%.

13. The maximum quantity of dissolved oxygen present in wastewater is called __________
a) Saturated dissolved oxygen
b) Maximum dissolved oxygen
c) Optimal dissolved oxygen
d) Peak dissolved oxygen
Answer: a
Clarification: At a given temperature, the maximum quantity of dissolved oxygen in sewage in wastewater is called saturated dissolved oxygen.

14. Identify the odd one of the following.
a) Fatty acids
b) Chlorides
c) Cellulose
d) Fats
Answer: b
Clarification: Chlorides are inorganic matter, whereas Fatty acids, Cellulose and Fats are organic matter.

15. The fresh sewage is acidic in nature.
a) True
b) False
Answer: b
Clarification: The fresh sewage is alkaline, but after sometime, the production of acid takes place and the pH of sewage decreases.

Environmental Engineering Multiple Choice Questions on “Conventional Trickling Filter”.

1. The breaking of the biomass from the slime layer in conventional filter is called _____
a) Sloughing
b) Carbonation
c) Biological magnification
d) Weathering
Answer: a
Clarification: The breaking of the biomass from the slime layer in conventional filter is called sloughing. It makes the effluent turbid.

2. The minimum hydraulic loading of percolating filter is ___________
a) 1 m³/m²/day
b) 2 m³/m²/day
c) 3 m³/m²/day
d) 4 m³/m²/day
Answer: a
Clarification: The minimum hydraulic loading of percolating filter is 1m³/m²/day whereas, the maximum hydraulic loading of percolating filter is 4m³/m²/day.

3. Which of the following is called as a conventional trickling filter?
a) Rapid sand filter
b) Slow sand filter
c) High rate trickling filter
d) Low rate trickling filter
Answer: d
Clarification: Low rate trickling filter is called as a conventional trickling filter. It is also called a standard rate and percolating filter.

4. The BOD after the filtration of sewage from the low rate trickling filter is ___________
a) 40-50%
b) 80-90%
c) 70-80%
d) 90-99%
Answer: b
Clarification: The BOD of the effluent obtained after the filtration of sewage from the low rate trickling filter is between 80 to 90% and the effluent obtained is highly nitrified and stabilized.

5. The efficiency of a percolating filter is given by ___________
a) 100/(1+0.0044 (μ))
b) 100/(1+0.044 (μ) ^1/2)
c) 100/(1+0.44 (μ) ^1/2)
d) 100/(1+0.0044 (μ) ^1/2)
Answer: d
Clarification: The efficiency of a percolating filter is given by η = 100/(1+0.0044 (μ)^1/2) where, μ is the organic loading in kg per hectare meter per day.

6. The removal of BOD is independent of the loading conditions in infiltration process.
a) True
b) False
Answer: b
Clarification: When the loading conditions are less, the efficiency of the filter will be more and the removal of BOD from the effluent will be more.

7. The organic loading in low rate trickling filter is 900 kg/hectare-meter/day. What is the efficiency of the filter?
a) 43.1%
b) 88.3%
c) 7.04%
d) 83%
Answer: b
Clarification: Efficiency of low rate trickling filter = 100/(1+0.0044 (μ)^1/2) = 100/(1+0.0044 (900)^1/2) = 100/1.132 = 88.3.

8. The organic loading in a trickling filter is measured in ___________
a) m³/day
b) gm/m²/day
c) Kg/hectare-meter/day
d) Kg/hectare/day
Answer: c
Clarification: The organic loading in a trickling filter is measured in kg / hectare-meter/day where, 1 hectare = 10⁴m³.

9. The hydrogen sulfide gas formed during the filtration of sewage can be removed by ___________
a) Carbonation
b) Chlorination
c) Addition of lime
d) Titration with potassium dichromate
Answer: b
Clarification: The hydrogen sulfide gas is formed when the fixed nozzles are used during the filtration process, so sewage is chlorinated to prevent the formation of H₂S gas.

10. The recirculation factor in a low rate trickling filter is ___________
a) 0
b) 1
c) 10
d) 100
Answer: b
Clarification: The recirculation factor F = (1+ R/I) / (1+0.1 (R/I)) ² = (1+0) /(1+0)² = 1.

Global Education & Learning Series – Environmental Engineering .

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

1. What is the principle behind which opacity monitors/transmissometers work?
a) Change in capacitance for various gaseous media, between two stationary plates
b) Pressure exerted by a fixed volume of gas enclosed in a container of specific dimension
c) Scattering of light transmitted through a gas stream
d) None of the mentioned
Answer: c
Clarification: Like the name suggests, opacity monitors or transmissometers work by transmitting light into a particular stream of gas, and gives information regarding the combustion conditions and efficiency.

2. Are any of the following monitors used to measure the concentration of particular gases from the exhaust generated in vehicles?
a) Opacity monitors
b) Gaseous emission monitors
c) Opacity & Gaseous emission monitors
d) None of the mentioned
Answer: b
Clarification: These monitors are used to measure the concentrations of certain gases such as oxygen, carbon monoxide, oxides of sulphur and nitrogen from the exhaust.

3. What does the abbreviation NDIR stand for, in the category of spectrometric analysers?
a) Non-Destructive Integrated Restoration
b) Neo-Destructive Integrated Radiation
c) Non-Dispersive Infrared
d) Neo-Dispersive Integrated Radiation
Answer: c
Clarification: NDIR detectors/analysers are used to monitor sulphur dioxide, oxides of nitrogen and carbon, hydrocarbons, etc.

4. Non-Dispersive Ultraviolet (NDUV) analysers are primarily used to detect which of the following two gases?
a) Oxygen and Carbon Dioxide
b) Oxygen and Nitrogen Dioxide
c) Nitrogen Dioxide and Sulphur Dioxide
d) Sulphur Dioxide and Oxygen
Answer: c
Clarification: NDUV analysers are mainly used to detect nitrogen dioxide and sulphur dioxide.

5. NDUV monitors use a reference gas to analyse other gases.
a) True
b) False
Answer: b
Clarification: NDIR monitors use a reference gas for analysis and not NDUV, which is the main difference between the two.

6. NDUV analysis is also known as the differential absorption.
a) True
b) False
Answer: a
Clarification: NDUV method uses a reference wavelength which has less absorption capabilities to find out variations in absorption with respect to this reference wavelength in different media.

7. Fluorescence analysers are used to analyse which of the following gases?
a) Nitrogen dioxide
b) Sulphur dioxide
c) Sulphur trioxide
d) Nitrous oxide
Answer: b
Clarification: Fluorescence occurs when a molecule is excited by light energy of specific wavelength and emits light energy of another wavelength.

8. Electroanalytical monitors rely on which of the following methods?
a) Polarography and amperometric analysis
b) Polarography and electrocatalysis
c) Polarography, electrocatalysis and conductivity
d) All of the mentioned
Answer: d
Clarification: Electroanalytical instruments rely on polarography, conductivity, electrocatalysis and amperometric analysis.

9. Which of the following analyser is used for oxygen analysis?
a) Electrocatalytic
b) Polarographic
c) Conductive
d) Amperometric
Answer: a
Clarification: Electrocatalytic analysers are used for oxygen monitoring.

10. In-situ cross stack analysers work behind which of the following principles?
a) Differential absorption spectroscopy
b) Gas-filter correlation spectroscopy
c) Differential absorption & Gas-filter correlation spectroscopy
d) None of the mentioned
Answer: c
Clarification: Cross stack analysers work behind the principles of differential absorption/gas-filter correlation spectroscopy.

11. In-situ in-stack analysers are used for measuring concentrations of which of the following gases?
a) Ammonia
b) Sulphur dioxide
c) Nitrogen monoxide
d) All of the mentioned
Answer: d
Clarification: In-site in-stack analysers work on the principle of second derivative spectroscopy to measure concentrations of ammonia, sulphur dioxide and nitrogen monoxide.

12. What is the disadvantage of using conductometric analysers?
a) Low sensitivity
b) Interfering gases must be removed before monitoring process
c) Medium used to measure change in conductivity is expensive
d) All of the mentioned
Answer: b
Clarification: Conductometric analysis is a non-specific method and hence requires interfering gases to be removed before monitoring process.

13. Flame photometric analysers are specific to sulphur compounds.
a) True
b) False
Answer: a
Clarification: Flame photometric analysers work behind the principle of luminescence through molecule/flame interaction and their use is limited to detect sulphur compounds alone.

14. Airshed modelling takes into account the effects of only stationary sources and not the mobile sources of pollution.
a) True
b) False
Answer: b
Clarification: Airshed modelling takes into account the effects of both mobile and stationary sources scattered in a small geographical region.

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Environmental Engineering Multiple Choice Questions on “Filter Media”.

1. Which of the following is not commonly used as a filter material in the treatment of water?
a) Sand
b) Anthracite
c) Crushed rock
d) Garnet sand
Answer: c
Clarification: Sand, Anthracite and Garnet sand are used as a filter material but crushed rock is not used in the treatment of water.

2. Which of the following is correct regarding the cheapest filter material used in water treatment?
a) Sand>Anthracite>Garnet sand
b) SandGarnet sand
c) Sandd) Sand=Anthracite>Garnet sand
Answer: a
Clarification: Sand is the cheapest filter material followed by anthracite whereas Garnet sand is the costliest among them and is not used as a sole filter material but as a constituent in mixed media filter.

3. Consider the following statements regarding sand as filter material.
i. It should be free from clay or silt
ii. Organic matter should be present in the sand
iii. It should be nonuniform
Which of the above statement is/are correct?
a) i, ii
b) i only
c) ii, iii
d) i, ii, iii
Answer: b
Clarification: Sand used as a filter material should be free from clay, silt, organic matter or other impurity. It should be uniform and of proper size.

4. The uniformity characteristics of sand expressed in terms of __________
a) Effective size
b) Effective size and uniformity coefficient
c) Uniformity coefficient
d) Mean velocity
Answer: b
Clarification: The uniformity characteristics of sand are expressed in terms of effective size and uniformity coefficient. Effective size is called as effective diameter and uniformity coefficient is a measure of particle range.

5. ____ represents the size of sand particle such that 10% of particles are finer than this size.
a) D_0.1
b) D₁
c) D₁₀
d) D₁₀₀
Answer: c
Clarification: D₁₀ represents the size of sand particle such that 10% of particles are finer than this size. It is also called the effective size or effective diameter and is measured in mm.

6. What is CU in the expression C_U= D₆₀/D₁₀ where D₆₀ and D₁₀ are the sizes of particle such that 60% and 10% of the particles are finer than these sizes respectively?
a) Coefficient of compaction
b) Coefficient of consolidation
c) Uniformity coefficient
d) Effective size
Answer: c
Clarification: The uniformity coefficient is a measure of particle range and it is the ratio of D₆₀ and D₁₀ sizes. It is denoted by C_U.

7. The effective size of sand of the slow sand filter is __________
a) 0.1-0.2mm
b) 0.2-0.3mm
c) 0.4-0.7mm
d) 1-2mm
Answer: b
Clarification: The effective size of sand of the slow sand filter is 0.2-0.3mm and for rapid sand filter, the effective size is 0.4-0.7mm.

8. What is the value of specific gravity of sand filter?
a) 2
b) 2.6
c) 3.1
d) 3.5
Answer: b
Clarification: The specific gravity of sand filter lies in the range of 2.55-2.65. So, the value 2.6 lies in the range of specific gravity of sand filter.

9. The value of uniformity coefficient for uniformly graded sand is ______
a) 0
b) 1
c) 10
d) 100
Answer: b
Clarification: Uniformity coefficient C_U = D₆₀/D₁₀
For uniformly graded sand, C_U = 1
So, D₆₀ = D₁₀.

10. The value of specific gravity for Garnet sand is ____
a) 2.1
b) 3.6
c) 4.2
d) 5.1
Answer: c
Clarification: Garnet sand is a dense material with a specific gravity of 4.2 and is used as a constituent in mixed media filter. It is a costlier filter material.

11. Which of the following statement is correct?
a) Ignition loss of filter should not exceed 3%
b) Wearing loss of filter sand should not exceed 5%
c) The range of CU for the slow sand filter is 3-5
d) The range of CU for the rapid sand filter is 3-5
Answer: c
Clarification: The ignition loss of filter should not exceed 0.7%, wearing loss of filter sand should not exceed 3%, range of CU for the slow sand filter is 3-5 and for the rapid sand filter is between 1.3 and 1.7.

Environmental Engineering Multiple Choice Questions on “Lime Soda Process”.

1. The permanent hardness can be removed by adding lime and soda.
a) True
b) False
Answer: a
Clarification: The permanent hardness can be removed by adding Ca (OH)₂ as lime and sodium carbonate as soda in water and the process is called lime soda process.

2. The time required for the mixing of lime and soda in lime soda process is _____________
a) 10min
b) 20min
c) 40min
d) 80 min
Answer: c
Clarification: The time required for the mixing of lime and soda in water in lime soda process is between 30-60min to allow completion of the chemical reaction. Precipitated chemicals are removed by sedimentation or filtration or both.

3. The temperature at which the softening of water takes place by lime soda process is ____________
a) 10^o-21^oC
b) 20^o-30^oC
c) 39^o-45^oC
d) 90^oC
Answer: a
Clarification: The lime soda process can be operated continuously or intermittently at either 10^o-21^oC or at 100^oC.

4. Which chemical is used for removing the permanent hardness of Calcium chloride?
a) Lime
b) Chlorine
c) Soda
d) Both lime and soda
Answer: b
Clarification: Only soda ash is used for removing the permanent hardness of Calcium chloride whereas for magnesium chloride both lime and soda are used for removing the permanent hardness.

5. Softening chemicals, lime and soda do not depend on ____________
a) Free carbon dioxide present
b) Non carbonate hardness
c) Total magnesium
d) Carbonate hardness
Answer: d
Clarification: Lime and soda depend on free carbon dioxide present, non carbonate hardness, total magnesium and does not depend on carbonate hardness.

6. The detention period of a lime soda treatment plant is ____________
a) 1hour
b) 3hours
c) 2-4hours
d) 4-7hours
Answer: c
Clarification: The detention period of a lime soda treatment plant is 2-4 hours to obtain greater clarification.

7. The minimum reaction time allowed in the recarbonation basin is ____________
a) 5minutes
b) 10minutes
c) 15minutes
d) 20minutes
Answer: d
Clarification: During lime soda treatment, the recarbonation of water is done in recarbonation basin where the minimum reaction time is 20minutes.

8. What is the pH at which recarbonation should be done?
a) 7
b) 4.5
c) 8.2
d) 9.5
Answer: d
Clarification: The carbonation of water containing excess lime will form a colloidal precipitate of calcium carbonate that is less soluble at pH 9.4-9.6, so the recarbonation should not be done below this range.

9. Which filter is normally used in the lime soda treatment plant?
a) Slow sand filter
b) Rapid sand filter
c) Dual media filter
d) Mixed media filter
Answer: b
Clarification: The recarbonated water in lime soda treatment plant is passed through the rapid filter to ensure complete clarification.

10. What is the detention time of a water softening accelerator?
a) 1-6minutes
b) 20minutes
c) 30 minutes
d) 1-2hours
Answer: d
Clarification: A water softening accelerator is a device that is used for mixing, flocculation and clarification of water and they have a short detention period in comparison to a sedimentation tank that is 1-2hours.

11. The sludge in water softening accelerator is deposited at ____________
a) Sedimentation tank
b) Reaction zone
c) Concentrator
d) Secondary mixing zone
Answer: c
Clarification: The sludge in water softening accelerator is deposited at a concentrator which can be discharged through a pipe continuously or can be discharged upon a schedule that can operate automatically.

Environmental Engineering Multiple Choice Questions on “Water Carriage System”.

1. Into how many types, the water carriage system is divided?
a) 2
b) 3
c) 4
d) 5
Answer: b
Clarification: The water carriage system is divided into a separate system, combined system and partially separate system.

2. The number of separate systems in a sewer area are?
a) 2
b) 3
c) 4
d) 6
Answer: a
Clarification: There are two separate systems of sewer, one for the conveyance of foul smell and other in the rain water.

3. The water carriage system is more suitable in rural conditions.
a) True
b) False
Answer: b
Clarification: The water carriage system is more suitable in urban conditions, whereas the conservancy system is more suitable in rural conditions.

4. Which of the following is an advantage of a separate water carriage system?
a) Get choked easily
b) Difficult to clean the sewer
c) Two sets of sewer are used
d) The more uniform character of sewage
Answer: d
Clarification: The sewage in the separate water carriage system will be of more uniform character and it will lend itself more easily to purification.

5. Which of the following is a disadvantage of a separate water carriage system?
a) Low installation charge
b) No loads on treatment units
c) Lesser air contact with small sized sewer
d) Provision of the automatic flushing tank is not required
Answer: c
Clarification: In a separate water carriage system, because of lesser air contact with small sized sewer, foul smell is formed due to the formation of sewage gas.

6. _______ provides only one sewer to carry both foul sewage and rainwater.
a) Separate water carriage system
b) Combined water carriage system
c) Partially combined water carriage system
d) Conservancy system
Answer: b
Clarification: In combined water carriage system, the sewage and the rain water are carried to the treatment units through only one sewer, before its final disposal.

7. Which of the following is correct regarding combined water carriage system?
a) The sewers are of small size
b) The strength of sewer is reduced by dilution
c) Low cost of construction
d) More chances of choking are there
Answer: b
Clarification: In the combined water carriage system, the sewers are of large size, the strength of sewer is reduced by dilution, there is the high cost of construction and rare chances of choking.

8. Which of the following is an advantage of the combined water carriage system?
a) There is more air in large sewer
b) There is the inclusion of storm water
c) There is difficulties in ventilation of large sewer
d) Overflowing of sewer
Answer: a
Clarification: In combined water carriage system, due to more air in large sewer, the sewer gas formed gets diluted and the chances of foul smell reduces.

9. Which of the following is incorrect regarding partially combined water carriage system?
a) The sewers are of reasonable size
b) There is choking of sewer
c) The storm water increases load on treatment units
d) The storm water increases the cost of pumping
Answer: b
Clarification: The storm water permitted in the sewer eliminates its chances of choking. The sewers are completely cleaned during rainy season.

10. The choice of combined water carriage system does not depend on ____________
a) Space consideration
b) Even rainfall pattern
c) Steep topography
d) Pumping requirements
Answer: c
Clarification: The choice of a combined water carriage system depends on space consideration, even rainfall pattern, conversion of existing storm water drains and pumping requirements.