Category: Environmental Engineering Objective Questions

Environmental Engineering Multiple Choice Questions on “Theory and classification of Filtration”.

1. Which of the following statement is wrong regarding filtration?
a) It removes fine particle
b) It removes suspended solids not removed by sedimentation
c) It does not remove turbidity
d) It removes color
Answer: c
Clarification: Filtration is a primary turbidity removal process. It also removes color, suspended solids and fine particles.

2. In which action of filtration, particles coarser than the void size is arrested?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action
Answer: a
Clarification: In Mechanical Straining, particles coarser than the void size is arrested. The water passing the voids will be free from such particles.

3. In which action of filtration, colloidal particles are removed?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action
Answer: b
Clarification: In the sedimentation action of filtration, colloidal particles arrested in the voids attract other finer particle, settle down in the voids and get removed.

4. Which is the first zone of purification in a sand bed?
a) Autotrophic zone
b) Heterotrophic zone
c) Schmutzdecke zone
d) Electrolytic zone
Answer: c
Clarification: Schmutzdecke zone is the first zone of purification in a sand bed. It comes under the biological action of filtration. Schmutzdecke is known as the surface coating.

5. Schmutzdecke acts as an extremely fine meshed straining mat.
a) True
b) False
Answer: a
Clarification: Schmutzdecke is a film of algae, bacteria and protozoa formed on the uppermost layer of sand which helps in the breakdown of organic impurities into harmless compounds acting as a fine mesh straining mat.

6. In which action of filtration, removal of particulate matter takes place?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action
Answer: d
Clarification: Filter removes the particulate matter by electrostatic exchange where the charge of the filter medium neutralizes the charge of the floc and permitting it to be removed.

7. In which type of filter, rate of filtration is low?
a) Slow sand filter
b) Rapid sand filter
c) Gravity filter
d) Pressure filter
Answer: a
Clarification: In Slow sand filter, rate of filtration is low and due to this they requires large land and are expensive to install.

8. What is the color of the surface coating formed during the filtration process?
a) White
b) Brown
c) Green
d) Reddish brown
Answer: d
Clarification: The surface coating is formed by the reddish brown deposit of partially decomposed organic matter together with Iron, Alumina, Manganese and Silica.

9. In the ________ zone of purification in filter media, bacteria oxidizes the organic matter completely.
a) Autotrophic
b) Heterotrophic
c) Schmutzdecke
d) Electrolytic
Answer: b
Clarification: In Heterotrophic zone, bacteria multiplies in large number, breaks down not only the organic matter but also destroys each other to maintain a balance of life in the filter.

10. The filtration rate of a slow sand filter is _____ litres of water per square metre.
a) 20
b) 30
c) 50
d) 100
Answer: d
Clarification: The surface area of the slow sand filter lies between 50m² to 1000m² and its filtration rate lies between 100 to 200 litres of water per m².

11. Identify the correct statement from the following options.
a) Rapid sand filter has a high initial cost
b) Coagulation is essential in slow sand filter
c) Slow sand filter requires skilled supervision
d) Period of cleaning of Rapid sand filter is 1-2 days
Answer: d
Clarification: Rapid sand filter is cheap and economical and its period of cleaning is 1-2 days. Neither the coagulation nor the skilled supervision is required in the slow sand filter.

Environmental Engineering Questions for Freshers on “Types of Hardness and Method of their Removal”.

1. The Total hardness of soft water as CaCO₃ equivalent is __________
a) 50ppm
b) 100ppm
c) 150ppm
d) 200ppm
Answer: a
Clarification: The Total hardness of soft water as CaCO₃ equivalent is 50ppm while of hard water, it is 150-300ppm.

2. The total hardness of water is 100ppm as CaCO₃ equivalent. What is the type of water?
a) Soft
b) Moderately hard
c) Hard
d) Very hard
Answer: b
Clarification: When the total hardness of water is between 50 and 150ppm as CaCO₃ equivalent, then the water is moderately hard.

3. The permanent hardness in water is due to the presence of __________
a) Sulfates, Chlorides
b) Sulfates, chlorides, nitrates
c) Carbonates and bicarbonates
d) Sulfates and carbonates
Answer: b
Clarification: The permanent hardness is due to the presence of sulfates, chlorides and nitrates of calcium and magnesium in water.

4. The temporary hardness in water is due to the presence of __________
a) Sulfates, Chlorides
b) Sulfates, Chlorides, nitrates
c) Carbonates and bicarbonates
d) Sulfates and carbonates
Answer: c
Clarification: The temporary hardness is due to the presence of carbonates and bicarbonates of calcium and magnesium in water.

5. Which of the following causes the temporary hardness?
a) CaSO₄
b) MgSO₄
c) MgCl₂
d) Ca (HCO₃) ₂
Answer: d
Clarification: As the temporary hardness is caused due to the presence of carbonate and bicarbonates, therefore Ca (HCO₃) ₂ cause temporary hardness.

6. The permanent hardness is also known as __________
a) Pseudo hardness
b) Non carbonate hardness
c) Carbonate hardness
d) Brinell hardness
Answer: b
Clarification: The permanent hardness is also known as non carbonate hardness whereas temporary hardness is also known as carbonate hardness.

7. Which of the following is not used for removing the permanent hardness?
a) Lime soda process
b) Zeolite process
c) Demineralization
d) Adding lime
Answer: d
Clarification: Adding lime is a method that is used to remove temporary hardness and it cannot remove the permanent hardness.

8. Which of the following statement is wrong regarding hard water?
a) It causes more consumption of soap in laundry work
b) It causes difficulties in the manufacturing process
c) It increases the taste of food
d) It causes the formation of scales on the boilers
Answer: c
Clarification: Hard water makes the food tasteless, tough and rubbery. So, the process of softening is done to improve the cooking of food.

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Environmental Engineering Multiple Choice Questions on “Conservancy System”.

1. Which system of collection of sewage is a dry system?
a) Conservancy system
b) Biological digestion
c) Incernation
d) Water carriage system
Answer: a
Clarification: The conservancy system is a dry and old system where sewage is deposited in the pit and then removed periodically after 24 hours.

2. After how many years, night soil gives good quality manure?
a) 1
b) 5
c) 10
d) 14
Answer: a
Clarification: Night soil is buried into the ground or trenches to give good quality manure in 1 or 2 years.

3. Hog feeding is a type of ______
a) Campaign
b) Food
c) Garbage disposal method
d) Disease
Answer: c
Clarification: Hog feeding is a type of garbage disposal method where hog eats the garbage. However, this method is opposed by health official as the place where hogs are kept smelling very bad.

4. Conservancy system is a highly unhygienic system, causing insanitary conditions.
a) True
b) False
Answer: a
Clarification: In conservancy system, the excreta starts decomposing within the few hours of its production, produce bad smell and give rise to fly nuisance.

5. Which of the following is not correct regarding conservancy system?
a) High maintenance cost
b) Highly unhygienic system
c) Independent of labour
d) Chances of epidemic
Answer: c
Clarification: This system is highly dependent on labour. Absence of Labour even for a day will cause a foul smell in the whole area.

6. Which system of collection of sewage is called a dry system?
a) Conservancy system
b) Biological digestion
c) Incernation
d) Water carriage system
Answer: a
Clarification: The conservancy system is an old method of collection of sewage where instead of water; humans are responsible for its collection, conveyance and disposal.

7. ________ is a method where water is used as a medium for the flow of sewage from its production of the treatment unit.
a) Conservancy system
b) Biological digestion
c) Incernation
d) Water carriage system
Answer: d
Clarification: In water carriage system, the collection, conveyance and disposal of various types of wastes are carried out with the help of water.

8. Normally, the amount of water required for flushing operation is _____ litres.
a) 10-20
b) 5-10
c) 15-20
d) 20-30
Answer: b
Clarification: In water carriage system, water closets are used where human excreta is removed by the flushing 5-10 litres of water by each person.

9. The water carriage system is a hygienic system without any bad smell.
a) True
b) False
Answer: a
Clarification: Water carriage system is very hygienic as the night soil and other waste water is conveyed through close conduits which are not directly exposed to the atmosphere.

10. Which of the following is correct regarding water carriage system?
a) Chances of the epidemic is there
b) Foul smell is produced
c) Does not cause pollution
d) Highly dependent on labours
Answer: c
Clarification: The liquid waste in the water carriage system is directly conveyed through the sewer, so there is no chance of the waste being soaked into the ground or contaminating the soil.

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.

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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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