ENVIRONMENT AND SAFETY ENGINEERING

1. 1
NATIONAL INSTITUTE OF TECHNOLOGY ROURKELA
Department of Chemical Engineering
Environment and Safety Engineering (CH1400)
NUMERICAL QUESTIONS
Environment and its Challenges
 A farmer is growing 50 plants of a mango species by removing all the existing plants from his
land, which originally had a plant diversity of 200 species. Calculate the loss of plant diversity.
[M2024-25S]
Water Pollution and Control
 Express the concentration of 100 mg/L of Mg2+
ions present in water in terms of mg/L of CaCO3
[M2022-23A]
 Calculate the concentration (in mol/L) of 1mL of H2SO4 required to neutralizes 1mg of
alkalinity as CaCO3. [M2024-25S]
 Calculate the "approximate" and the "exact" alkalinity (in mg/L as CaCO3) of a water
containing 200.0 mg/L of bicarbonate ion and 150.0 mg/L of carbonate ion. If the pH is 10.
 A water has an alkalinity of 100 mg/L as CaCO3. The Ca2+
concentration is 60 mg/L. Find the
non-carbonate hardness. [M2022-23A]
 If the total hardness and alkalinity of the water sample are 400 mg/L as CaCO3 and 450 mg/L
as CaCO3 respectively, what are the values of carbonate hardness and non-carbonate hardness?
[M2023-24A]
 A sample of water having a pH of 7.2 has the following concentrations of ions. Calculate the
TH, CH, NCH. [M2022-23S]
 A sample of water has been analyzed for common ions and results are presented in the form of
a bar diagram as shown in figure below (the values have been given in terms of CaCO3). Find
the total, carbonate, and non-carbonate hardness as mg/L CaCO3. [M2023-24A]
 A sample of water has been analysed for common ions and results are presented in the form of
a bar diagram as shown in figure below (the values have been given in terms of CaCO3). Find
the total, carbonate, and non-carbonate hardness as mg/L CaCO3. [M2024-25A]

2. 2
 A sample of water having pH of 7.2 has following concentration of ions. Calculate the total
hardness, carbonate hardness, non-carbonate hardness and approximate alkalinity of the sample
in mg/L as CaCO3. Also construct a bar chart of the cations and anions. [M2024-25S]
 A sample of water having a pH of 7.5 has the following concentrations of ions. Construct a bar
chart of the ions in terms of mg/L as CaCO₃. Calculate the TH, CH, NCH, Alkalinity [M2025-
26A]
 The analysis of water sample produces the following results. Find out the carbonate, non-
carbonate, and total hardness in mg/l as CaCO3. [M2023-24A]
 The analysis of water sample produces the following results. (a) Find out the carbonate, non
carbonate and total hardness in mg/L as CaCO3. (b) Construct a bar chart of the ions in term of
mg/L CaCO3. [M2023-24S]
 The analysis of water sample produces the following results. Find out the total, carbonate and
non-carbonate hardness in mg/L as CaCO3. [M2024-25A]

3. 3
 What is theoretical oxygen demand (THOD)? Calculate THOD for 400 PPM of Glucose?
[M2023-24A]
 What is the theoretical oxygen demand for 500 PPM of Glucose? [M2024-25A]
 Calculate the theoretical oxygen demand of water that contains 210 mg/L of glucose (C6H12O6)
and 39 mg/L of benzene (C6H6). Molar mass of glucose and benzene are 180 g/mol and 78
g/mol respectively. [M2024-25S]
 What is the theoretical oxygen demand for 600 mg/L of methane? [M2025-26A]
 A wastewater sample is collected from a river, and its BOD is to be determined. A 300 mL
sample of the water is placed in a BOD bottle. After 5 days of incubation at 20°C, the dissolved
oxygen (DO) concentration in the BOD bottle is measured and found to be 6.3 mg/L. The initial
DO concentration in the BOD bottle was 10.6 mg/L. Calculate the BOD of the wastewater
sample. [M2024-25A]
 For a waste water sample, the two-day biochemical oxygen demand (BOD) at incubation
temperature of 20℃ is estimated as 160 mg/L. Taking the value of the first order BOD reaction
rate constant as 0.25 day-1, what will be the value of the five-day BOD of the wastewater at
incubation temperature of 20℃? [M2024-25A]
 If the 5 day BOD (BOD5) of a wastewater is 100 mg/L and the BOD decay constant, k, is 0.369
day 1, what is the ultimate BOD? [M2023-24S]
 If the 3-day BOD (BOD3) of a waste is 0.135 g/L and the BOD decay constant, k, is 0.02 hr-1
,
what is the ultimate BOD? [M2025-26A]
 The BOD of a sewage incubated for one day at 30°C has been found to be 100 mg/L. What will
be the five day 20°C BOD? Assume K = 0.12 (base 10) at 20°C, and θ = 1.056 [M2022-23S]
 The 5-day BOD of wastewater is found to be 150 mg/L at 20 ℃. The value of k is 0.23 per day.
What would be the 3-day BOD if the test were run at 15 ℃? The value of k at any temperature
T ℃ is given by 𝑘𝑇=𝑘20(1.047)𝑇−20
[M2024-25S]
 A waste water of 3 ml is made up to 300 ml in a BOD (Biochemical Oxygen demand) bottle
with distilled water. Initial DO (Dissolved Oxygen) of water is 8 mg/l and after 5 days at 20℃
DO is 3 mg/l. Find BOD in PPM? [M2023-24A]
 In a BOD test, initial DO of the 2% diluted sample is 8 mg/l and its DO after 5-day incubation
at 20℃ is 3 mg/l. Calculate the 5-day BOD value of sewage sample? [M2023-24A]
 In a BOD test, initial DO of the 7% diluted sample is 15 mg/L and its DO after 3 day incubation
at 20℃ is 7 mg/L. Calculate the 3 day BOD value of sewage sample? [M2023-24S]
 In a BOD test, initial DO of the 5.5% diluted sample is 11 mg/L and its DO after 5 day
incubation at 20℃ is 4 mg/L. Calculate the 5 day BOD value of sewage sample? [M2024-25A]
 In a BOD test, initial DO of the 3% diluted sample is 9.8 mg/L and its DO after 5-day incubation
at 20 ℃ is 7.2 mg/L. What is the 5-day BOD of sewage sample? [M2025-26A]
 The dissolved oxygen in a sample of diluted wastewater having an initial DO of 9 mg/l is
measured to be 3 mg/l after 5 days. The dilution fraction is 0.03 and reaction rate constant
k=0.22 day-1
. Calculate: (a) 5 day BOD of the waste, (b) ultimate BOD, and (c) What would be
the remaining oxygen demand after 5 days? [E2023-24A]
 The dissolved oxygen in a sample of diluted waste water having an initial DO of 6.0 mg/L is
measured to be 4.5 mg/L after 5 days. The dilution fraction is 0.03 and reaction rate constant k

4. 4
= 0.22 day-1
. Calculate a) 5 day BOD of wastewater b) ultimate BOD c) the remaining oxygen
demand after 5 days. [M2024-25S]
 In a wastewater sample, the initial dissolved oxygen is 14 mg/L and it is reduced to 6 mg/L
after 5 days. The dilution factor is 75 and reaction rate constant k = 0.5 day-1
. Calculate (a) 5
day BOD of the waste (b) ultimate BOD and (c) What would be the remaining oxygen demand
after 5 days? [E2023-24S]
 The initial dissolved oxygen in a wastewater sample is 17 mg/L and it is reduced to 5 mg/L
after 5 days. The dilution factor is 80 and reaction rate constant k=0.02 hour-1
. Calculate: (a) 4
day BOD of the waste, (b) ultimate BOD, and (c) What would be the remaining oxygen demand
after 5 days? [E2024-25A]
 A coagulation treatment plant with a flow of 0.5 m3
/s is dosing alum at 23 mg/l. Concentration
of suspended solid is 37 mg/l. The effluent suspended solid concentration is 12 mg/l. The sludge
content is 1 % and specific gravity of sludge is 3 %. What volume of dry sludge must be
disposed of each day? [M2022-23A]
 A coagulation treatment plant with a maximum flow of 4 m3
/s is dosing alum at 30 mg/l.
Concentration of suspended solid in raw water is 43 mg/L. The effluent suspended solid
concentration is 17 mg/L. The sludge content is 2 % and specific gravity of sludge solids is 4.
What volume of sludge must be disposed of each day? [E2023-24A]
 A coagulation treatment plant with a maximum flow of 6 m3
/s is dosing alum of 45 mg/l. The
concentration of suspended solids in raw water is 33 mg/l. The effluent-suspended solid
concentration is 24 mg/L. The sludge content is 1% by weight and the specific gravity of sludge
solids is 2. What volume of sludge must be disposed of each day? [E2023-24S]
 A coagulation treatment plant has an effluent suspended solid concentration of 32 mg/L. It has
a maximum flow of 8 m3
/s and the dosage of alum is 39 mg/l. Concentration of suspended solid
in raw water is 42 mg/L. The. The sludge content is 3 % and specific gravity of sludge solids
is 3. What volume of sludge must be disposed of each day? [E2024-25A]
 A coagulation treatment plant has an effluent suspended solid concentration of 28 mg/L. It has
a maximum flow of 8 m3
/s, and the dosage of alum is 35 mg/l. The concentration of suspended
solids in raw water is 42 mg/L. The. The sludge content is 5 % and the specific gravity of sludge
solids is 2. What volume of sludge must be disposed of each day? [E2025-26A]
 A coagulation treatment plant with a maximum flow of 1.5 m3
/s is dosing alum at 50 mg/l. The
concentration of suspended solid in raw water and effluent are 50 mg/L and 12 mg/L
respectively. The sludge content is 1% by weight and specific gravity of sludge solids is 6.48.
What volume of sludge that must be disposed of each day? 1 mole of alum produce 2 moles of
Al(OH)3. The molar mass of alum and Al(OH)3 are 666 g/mol and 78 g/mol respectively.
[E2024-25S]
 A water treatment plant with an average flow of Q = 0.044 m3
/s 1 treats its water with alum
(Al2(SO4)3⋅14H2O) at a dose of 25 mg/L. Alum coagulation is used to remove particulate matter,
reduce the concentration of organic matter, and reduce the alkalinity of the water according to
the stoichiometry below. If the organic matter concentration is reduced from 8 mg/L to 3 mg/L
determine the total mass of alkalinity consumed and the total mass of dry solids removed per
day. [E2023-24A]
 A water treatment plant with an average flow of Q = 0.056 m3
/s treats its water with alum
(Al2(SO4)3⋅14H2O) at a dose of 30 mg/L. Alum coagulation is used to remove particulate matter,

5. 5
reduce the concentration of organic matter, and reduce the alkalinity of the water according to
Equation 1. If the organic matter concentration is reduced from 10 mg/L to 3 mg/L. Determine
the total mass of alkalinity consumed and the total mass of dry solids removed per day. [M2023-
24S]
 A water treatment plant with an average flow of Q = 0.054 m3
/s treats its water with alum
(Al2(SO4)3⋅14H2O) at a dose of 30 mg/L. Alum coagulation is used to remove particulate matter,
reduce the concentration of organic matter, and reduce the alkalinity of the water according to
the equation given below. If the organic matter concentration is reduced from 10 mg/L to 4
mg/L determine the total mass of alkalinity consumed and the total mass of dry solids
removed per day. [M2024-25A]
 A water treatment plant with an average flow of Q = 0.072 m³/s treats its water with alum
(Al2(SO4)3⋅14H2O) at a dose of 35 mg/L. Alum coagulation is used to remove particulate matter,
reduce the concentration of organic matter, and reduce the alkalinity of the water according to
the equation given below. If the organic matter concentration is reduced from 12 g/m³ to 5 g/m³,
determine the total mass of alkalinity consumed and the total mass of dry solids removed per
day. [M2025-26A]
 How much Lime is required for the softening of wastewater with 180 PPM (as CaCO3) of
Mg(HCO3)2? [M2023-24S]
 A wastewater contains 180 PPM and 210 PPM of calcium sulphate and and calcium chloride
respectively. How much soda ash is required to removed the hardness due to calcium? [E2023-
24S]
 A wastewater contains 195 PPM and 220 PPM of Calcium sulphate and Calcium chloride,
respectively. How much Soda ash is required to remove the hardness due to Calcium? [E2024-
25A]
 In a water softening plant, how much Lime has to be added to neutralize carbonic acid generated
by 10 PPM CO2? In the same plant, how much Soda ash is required to remove non-carbonate
hardness created by 15 PPM of CaSO4? [M2024-25A]
 Find the terminal settling velocity (m/s) of a spherical discrete particle with diameter 0.1 mm
and a specific gravity of 3.5 settling through the water at 20°C. Density of water = 1000 kg/m3
and viscosity of water = 0.001 Ns/m2
. [M2022-23A]
 Find the terminal settling velocity of a spherical discrete particle with diameter 1 mm and
specific gravity of 2.79 settling through water at 20℃with laminar flow condition. Density of
water = 1000 kg/m3
; Viscosity of water = 0.001 Ns/m2
[E2023-24A]
 Find the terminal settling velocity of a spherical discrete particle with diameter 0.7 mm and
specific gravity of 2.65 settling through water at 20℃ with laminar flow condition. Density of
water = 1000 kg /m3; Viscosity of water = 0.001 Ns/m2
[M2023-24S]
 Find the terminal settling velocity of a spherical discrete particle with diameter 0.4 mm and
specific gravity of 2.67 settling through water at 20℃ with laminar flow condition. [M2024-
25A]
 Find the terminal settling velocity of a spherical discrete particle with diameter 0.12 cm and
specific gravity of 2.50 settling through water at a temperature of 25 °C with laminar flow
condition. Density of water = 1 kg/L, Viscosity of water = 0.001 Ns/m² [M2025-26A]
 A spherical discrete particle of specific gravity of 4.5 settle in water at a terminal velocity of
0.9 m/s. This particle is coated uniformly with a material to create a composite particle. The
thickness of coating (shell) is equal to the radius of core. Calculate the maximum specific
gravity of coating material such that the composite particle does not settle when placed in water.
[M2024-25S]

6. 6
 The length, height, and width of a rectangular settling tank are 10 m, 2.5 m and 5 m,
respectively. If water enters and leaves the settling tank at 25 m3
/h, what is the detention time
of water in the settling tank. [M2022-23A]
 The length, height, and width of a rectangular settling tank are 10m, 2.5 m and 5 m, respectively.
If water enters and leaves the settling tank at 25 m3
/h, what is the detention time of water in the
settling tank? [E2022-23S]
 The dimensions of a wastewater treatment tank are 24 x 8 x 3 m3
and the inlet flow rate is 5
million litres/day. Calculate the loading rate. [E2024-25A]
 The dimensions of a wastewater treatment tank are 30 x 7 x 3 m3
and the inlet flow rate is 5.5
million litres/day. Calculate the loading rate. [E2025-26A]
 In a water treatment plant, the settling tank has length of 24 m, width 8 m, and height 2 m. The
inlet flow of water into the tank is 3 million litres per day. Calculate the surface overflow rate.
 A rectangular sedimentation tank is treating 3 million litres/day. The size of the tank is 20 x 6
x 3 m. If 100 ppm suspended solids are present in the water, assuming 70% removal in the basin
and the average specific gravity as 2.0. Determine the following: (i) average flow of water
through the tank (ii) detention time (iii) amount of solids deposited in the tank. [E2022-23A]
 If a rectangular sedimentation tank is treating 4.5 million litres/day. The size of the tank is 24
x 8 x 4 m. If 150 ppm suspended solids are present in the water, assuming 70% removal in the
basin and the average specific gravity as 2.0. Determine the following: (i) average flow of water
through the tank (ii) detention time (iii) amount of solids deposited in the tank (iv) overflow
rate. [E2023-24A]
 If a rectangular sedimentation tank is treating 2.5 million litres/day. The size of the tank is 17.5
x 5.5 x 3.5 m. If 80 ppm suspended solids are present in the water, assuming 75% removal in
the basin and the average specific gravity as 2.0. Determine the following: (i) average velocity
of flow of water through the tank (ii) detention time (iii) amount of solids deposited in the tank
(iv) overflow rate. [E2024-25S]
 The dimensions of a sedimentation tank are 36 x 12 x 6 m3
and it treats 7 million litres/day. If
300 ppm suspended solids are present in the water, assuming 80% removal in the basin and the
average specific gravity as 3.0. Determine the following: (i) average flow of water through the
tank (ii) detention time (iii) mass of solids deposited in the tank (iv) overflow rate. [E2023-
24S]
 The surface area and cross-sectional area of a 6 m height sedimentation tank are 60 m2
and 400
m2
, respectively. It treats 10 million litres/day. If 350 ppm suspended solids are present in the
water, assuming 85% removal in the basin, and the average specific gravity is 2.0. Determine
the following: (a) Average flow of water through the tank (b) Detention time (c) Amount of
solids deposited in the tank (d) Overflow rate. [E2025-26A]
 The surface area and cross sectional area of a 5 m height sedimentation tank are 50 m2
and 300
m2
, respectively. It treats 8 million litres/day. If 250 ppm suspended solids are present in the
water, assuming 75% removal in the basin and the average specific gravity as 2.0. Determine
the following: (i) average flow of water through the tank (ii) detention time (iii) amount of
solids deposited in the tank (iv) overflow rate. [E2024-25A]
 Design a plain sedimentation rectangular tank for a town with a population of 50,000. Per capita
water demand of 140 lit/p/d, horizontal flow velocity of 0.30 m/min; detention period of 3 h.
[M2022-23A]
 A rectangular primary settling tank in a wastewater treatment plant has the following
dimensions: Tank length (L) = 40 m, Tank width (W) = 8 m, Effective water height (H) = 3.5
m. The influent flow rate (Q) to the tank is 1800 m³/h. Verify that the tank dimensions satisfy
the design criteria. Calculate the horizontal velocity, V (in m/s) through the tank. [M2025-26A]
 A rapid sand filter is designed for a flow rate of 10 m3
/s and it was loaded at 1000 m3
/ day.m2
of water. If the total load was shared by four filter boxes, what should be the surface area (in
square meters) provided by each filter. [M2022-23A]

7. 7
 Calculate the surface area of sand filter beds for the water works of a town of population 95,000;
per capita demand as 135 litres/capita/day. Rate of filtrations is 220 litres/hour/m2
. [M2022-
23S]
 Rapid sand filters are being installed in a wastewater treatment plant. The design loading rate
to the filter is 320 m3
/day.m2
. How much filter surface area should be provided for their design
flow rate of 2.8 x 106
cm3
/s? If the surface area per filter box is to be limited to 90 m2
, how
many filter boxes are required? [E2023-24S]
 A new treatment plant installed rapid sand filters after their sedimentation tanks. The design
loading rate to the filter is 240 m3
/day.m2
. How much filter surface area should be provided for
their design flow rate of 1 m3
/s? If the surface area per filter box is to be limited to 60 m2
, how
many filter boxes are required? [E2023-24A]
 In a wastewater treatment plant, the design loading rate to the rapid sand filter is 14 m3
/hour.m2
.
How much filter surface area should be provided for their design flow rate of 280 cm3
/s? If the
surface area per filter box is to be limited to 80 m2
, how many filter boxes are required? [E2024-
25A]
 In a wastewater treatment plant, the design loading rate to the rapid sand filter is 14 m3/hour.m2
.
How much filter surface area should be provided for their design flow rate of 2.8 m3
/s? If the
surface area per filter box is to be limited to 80 m2
, how many filter boxes are required? [E2025-
26A]
 A small town is having a population of 2,00,000 and the per capita demand of water is 135
litres/capita/day. Design slow sand filters that are required for treating the municipal water for
the town. Assume the rate of filtrations is 150 litres/hour/m2
. If the total area required is
provided for 10 filters, what is the area of each filter. Also mention the appropriate dimensions
of each filter. [E2022-23A]
 The population of a town is 90000 and the per capita demand is 180 litres/capita/day and the
rate of filtration is 200 litres/hour/m2
. Seven slow sand filters are used for the filtration process
but five filters are operational. Find out the surface area of each filter unit. [E2023-24S]
 The population of a town is 110000 and the per capita demand is 220000 millilitres/capita/day
and rate of filtrations is 30 litres/min/m2
. Five slow sand filters are used for the filtration process
but four filters are operational. Find out the surface area of each filter unit. [E2024-25A]
 The population of a town is 130000, and the per capita demand is 240000 millilitres/capita/day,
and the rate of filtration is 40 litres/min/m2
. Six slow sand filters are used for the filtration
process, but four filters are operational. Find out the surface area of each filter unit. [E2025-
26A]
 Design seven slow sand filter beds from the following data for the water works of a town of
population 90000; per capita demand as 165 litres/capita/day. Rate of filtrations as 180
litres/hour/m2
. Out of seven units, two unit is to be kept as standby. [E2023-24A]
 Design five rapid sand filter beds from the following data for the water works of a town of
population 225,000; per capita demand as 45 litres/capita/day. Rate of filtrations as 150
litres/hour/m2
. Out of five units, one unit is to be kept as standby. Take length to be thrice of
width. [E2024-25S]
 It is required to supply water to a population of 20000 at a per capita demand of 150 litres per
day. The disinfectant used for chlorination is bleaching powder which contains 30% of
available chlorine. Determine how much of bleaching powder is required annually at the
waterworks, if 0.4 ppm of chlorine dose is required for disinfection. [E2022-23S]
 Design a grit chamber for a maximum wastewater flow of 0.18 m3
/s with a horizontal velocity
of 0.25 m/s, depth of 1.2 m and detention period of one minute. [E2023-24S]
 Design a grit chamber for maximum waste water flow of 0.25 m3
/sec with the horizontal
velocity as 0.35 m/sec, depth as 2 m and detention time period as one minute. [E2024-25A]
 Design a grit chamber for a maximum wastewater flow of 0.28 m3
/sec with the horizontal
velocity as 0.4 m/sec, depth as 2.2 m, and detention time period as one minute. [E2025-26A]

8. 8
Air Pollution and Control
 What is the minimum size of the particle that will be removed with 100% efficiency from a
settling chamber under the following conditions; Viscosity of air = 2.1 x 10-5
kg/m.s; Air
horizontal velocity = 45 cm/s; Particle specific gravity = 2.4; Chamber length = 9 m; Height =
2 m [E2023-24A]
 What is the minimum size of the particle that will be removed with 100% efficiency from a
settling chamber under the following conditions: Viscosity of air = 2.1x10-5
kg/m.s. Air
horizontal velocity = 40 cm/s. Particle specific gravity = 2. Chamber length = 8 m; Height =
2m [E2023-24S]
 What is the minimum size of the particle that will be removed with 100 % efficiency from a
settling chamber under the following conditions; Viscosity of air = 2.1 x 10-5
kg/m.s Air
horizontal velocity = 60 cm/s Particle specific gravity = 3 Chamber length = 11 m; Height = 3
m [E2024-25A]
 What is the minimum size of the particle that will be removed with 100 % efficiency from a
settling chamber under the following conditions; Viscosity of air = 1.8 x 10-5
kg/m.s Air
horizontal velocity = 63 cm/s Particle specific gravity = 2.5 Chamber length = 11 m; Height =
3 m [E2025-26A]
 A multi-tray settling chamber having 8 trays, including the bottom surface, handles 6 m3
/s of
air at 20 °C. The trays are spaced 0.25 m apart and the chamber is to be 1 m wide and 4 m long.
What is minimum particle size of density 2000 kg/m3
that can be collected with 100 %
efficiency? What will be the efficiency of the settling chamber if 50 μm particles are to be
removed? Assume μg at 20°C as 1.8 x 10-5 kg/m-s. [E2022-23A]
 A cyclone is used to separate particulate material from air. The cyclone has specifications of:
body diameter = 1 m, height of inlet= 15 cm, width of inlet = 15 cm, length of cone = 1.2 m,
length of body = 1.8 m. Flow rate of air--particulate mixture is 200 m3
/min. Density of the
particle is 1800 kg/m3
. Density and viscosity of air are 1.204 kg/m3
and 1.81 x 10-5
kg/m.s.
Particle size distributions are as follows: Calculate collection efficiencies and contribution to
performances of each particle size range. [E2023-24A]
 A cyclone separator is used to separate particulate material from air. The cyclone has the
dimensions of body diameter = 2m, height of inlet = 20cm, width of inlet = 20 cm, length of
cone = 2m, length of body = 3 m. Flow rate of air-particulate mixture is 220 m3
/min. Density
of the particle is 1900 kg/m3
. Density and viscosity of air are 1.204 kg/m3
and 1.81x10-5
kg/m.s.
Particle size distribution are given below. Calculate the collection efficiencies and contribution
to performances of each particle size range. [E2023-24S]

9. 9
 A cyclone separator has the dimensions of: body diameter = 3 m, height of inlet = 25 cm, width
of inlet = 25 cm, length of cone = 2.5 m, length of body = 4 m. Flow rate of air-particulate
mixture is 250 m3
/min. Density of the particle is 1700 kg/m3
. Density and viscosity of air are
1.204 kg/m3
and 1.81 x 10-5
kg/m.s. Calculate collection efficiencies and contribution to
performances of each particle size range. Particle size distributions are as follows: [E2024-25A]
 A cyclone separator has the dimensions of: body diameter = 3.2 m, height of inlet = 30 cm,
width of inlet = 30 cm, length of cone = 2.5 m, length of body = 4 m. The Flow rate of the air-
particulate mixture is 250 m3
/min. Density of the particle is 1800 kg/m3
. Density and viscosity
of air are 1.204 kg/m3
and 1.81 x 10-5
kg/m.s. Calculate collection efficiencies and contribution
to performance of each particle size range. Particle size distributions are as follows: [E2025-
26A]
 A cyclone has an inlet width of 10 cm and five effective turns. The gas temperature is 350 K
and the inlet velocity is 10 m/s. The average particle diameter is 7 microns and the average
density is 1.5 g/cm3
. The viscosity of air at 350 K is 0.0748 kg/m.h and assuming that the
density of the air is negligible compared to particle density, what is the collection efficiency?
[E2023-24S]
 A cyclone is used to separate particulate material from air. The cyclone has specifications of:
body diameter = 1 m, height of inlet = 30 cm, width of inlet = 15 cm, length of cone = 3.6 m,
length of body = 3.0 m. Flow rate of air-particulate mixture is 200 m3
/min. Density of the
particle is 1800 kg/m3
, Density and viscosity of air are 1.204 kg/m3
and 1.81 x 10-5
kg/m.s.
Calculate collection efficiency for particle of average radius 2.5 μm. [E2024-25S]
 Calculate the pressure drop across the fabric filter. The details are given as the flow velocity
2.0 m/s, fluid viscosity 0.001 Pa.s, length of the feed section 0.5 m, length of the permeate

10. 10
section 0.3 m, permeability of feed 2.0×10−12
m2
, permeability of permeate 3.0×10−12
m2
.
[E2025-26A]
 Design an electrostatic precipitator for an air flow of 45 m3
/s from a cement manufacturing unit.
It contains cement particles whose settling velocity is 0.12 m/s. If 99 percent removal efficiency
is required, calculate the surface area of the electrostatic precipitator. [E2022-23A]
 Calculate the collection efficiency of horizontal flow, single stage electrostatic state precipitator
consisting of two sections formed by plates 6.0 m wide and 8.0 m high on 30 cm centers
handling a gas flow of 2.5 m3
/s. Assume the migration velocity is 12 cm/s. [E2022-23S]
 An electrostatic precipitator (ESP) with 5600 m2
of collector plate area is 96 percent efficient
in treating 185 m3
/s of flue gas from a 200 MW thermal power plant. To increase the efficiency
to 99 percent, what will be the ESP collector plate area? [E2023-24S]
 Find the migration velocity of an electrostatic precipitator with a collection plate of length 22
m and width 5 m. The gas flow rate is 2.5 m3
/s and collection efficiency is 99.5%. Calculate
the collection efficiency if the gas flow rate is doubled. Assume that the migration velocity is
constant. [E2024-25S]
Noise Pollution and Control
 A machine shop has two machines, one producing a sound pressure level of 80 dB and one
producing 60 dB. A new machine producing 70 dB is brought into the room. What is the new
sound pressure level in the room? [E2022-23A]
 A machine shop has two machines, one producing a sound pressure level of 90 dB and one
producing 68 dB. A new machine producing 94 dB is brought into the room. What is the new
average sound pressure level and sound pressure in the room? [E2022-23S]
 A machine shop has two machines, one producing a sound pressure level of 60 dB and one
producing 58 dB. A new machine producing 68 dB is brought into the room. What is the new
sound pressure level in the room? [E2023-24A]
 A machine shop has two machines, one producing a sound pressure level (SPL) of 60 dB and
one producing 48 dB. Two new machines producing 68 dB and 59 dB are brought into the
room. What is the new sound pressure level in the room? [E2023-24S]
 A machine shop has two machines, one producing a sound pressure level of 70 dB and one
producing 61 dB. Two new machines producing 81 dB and 92 dB are brought into the room.
What is the new sound pressure level in the room? [E2024-25A]
 A sound source generates 60 dB. What would the SPL be 80 m from the source? [E2023-24A]
 A sound source generates 85 dB. What would the SPL be 80 m from the source? [E2023-24S]
 A sound source generates 110 dB. What would the SPL be 0.1 miles from the source? [E2024-
25A]
 A sound source in a room generates 80 dB. What would the SPL be 100 m from the source?
Two new machines producing 75 dB and 85 dB were brought into the room. What is the new
sound pressure level in the room? [E2024-25S]
 A machine shop has two machines, one producing a sound pressure level of 80 dB and one
producing 65 dB. Two new machines producing 78 dB and 85 dB are brought into the room.
What is the new sound pressure level in the room? What would the SPL be 0.15 miles from the
room? [E2025-26A]
Safety Engineering
 As shown in Fig., the occurrence of the top fault event “dark room” is hazardous. The
probabilities of occurrence of fault events “power failure”. “switch fails to close”, “fuse

11. 11
failure”, “bulb A burnt out”, “bulb B burnt out”, and “bulb C burnt out” are 0.02, 0.03, 0.04,
0.05, 0.07 and 0.08 respectively. Calculate the probability of occurrence of the unsafe event
“dark room”. [E2023-24S]
 “Pump Fails” is an unsafe or hazardous event. The probabilities of “switch fails to close”, “fuse
failure”, “power failure”, “pump A fails”, “pump B fails”, “pump C fails” are 0.02, 0.03, 0.04,
0.05, 0.06, and 0.07, respectively. Calculate the probability of the unsafe event “Pump Fails”.
[E2024-25A]
 “Pump Fails” is an unsafe or hazardous event. The probabilities of “switch fails to close”, “fuse
failure”, “power failure”, “pump A fails”, “pump B fails”, and “pump C fails” are 0.03, 0.04,
0.05, 0.06, 0.07, and 0.08, respectively. Calculate the probability of the unsafe event “Pump
Fails”. [E2025-26A]
 Assume that in an organization during a 6-month period a total of 137 accidents occurred and
their monthly breakdowns are presented in Table 1. Develop a C-chart. [E2022-23S]

12. 12
 Develop a HAZOP data sheet consisting of deviations, consequences, causes and suggested
actions by considering ‘No’, ‘Less’, ‘More’, ‘Part of’ as ‘Guide words’ and ‘Flow’ as process
parameter. [E2024-25A] [E2025-26A]
Phosphoric acid + ammonia = DAP (non-hazardous)
Too little phosphoric acid → hazardous ammonia
Too little ammonia → safe but undesirable product.
 What are the basic assumptions of Markov process? The process diagram of a Markov process
is given in the adjacent figure. Calculate the transition matrix of the process. If the process is
initially in state A, calculate the probability that the process exist in state B after first step and
in state C after second step. [E2024-25S]

13. 13
THEORY QUESTIONS
Environment and its challenges
 Write short note on Nitrogen cycle. [E2023-24A]
 Briefly explain: (a) Nitrogen cycle (b) Waste management hierarchy [M2023-24S]
 What is the importance of ecological cycles? Briefly explain carbon and water cycles with a
 schematic diagram. [E2024-25S]
 Elaborate the nitrogen and phosphorous cycle along with their significance in environmental
engineering. [M2025-26A]
 Write a short note on ‘Biodiversity’. [M2023-24S]
 Explain the concept of biodiversity and provide an overview of its classifications. List the
threats to biodiversity. [M2023-24A]
 Explain the concept of biodiversity, including its classifications, and list three major threats to
it. [M2025-26A]
 What is the difference between in-situ and ex-situ conservation of biodiversity? Give examples
for each. [M2024-25S]
 Compare between Ocean acidification and Acid rain. [M2023-24S]
 What do you mean by global environmental challenge? Explain with example. [E2022-23S]
 Write short notes on acid rain, Ozone depletion, Nitrogen cycle and waste management
hierarchy. [M2024-25A]
 List the five options of the waste management hierarchy. [M2024-25S]
 Write short notes on acid rain and ozone depletion, highlighting their causes and effects.
[M2025-26A]
 Write a short note on ocean acidification and its environmental impact. [M2025-26A]
Water Pollution and Control
 List the four categories of water quality for drinking water. [M2022-23S]
 Enumerate the physical, chemical, and biological aspects to assess water quality. [M2023-24A]
 List and briefly explain any three physical, chemical and biological properties of water?
[M2023-24S]
 Elaborate the water quality parameters in details. [M2024-25A]
 Explain the physical, chemical, and biological aspects used to assess water quality with
examples [M2025-26A]
 Mention the chemicals used to remove temporary hardness and permanent hardness of water.
Also mention the reactions with those chemicals. [M2022-23A]
 Derive an expression to calculate the amount of BOD that has been exerted (amount of oxygen
consumed) at any time ‘t’. [M2022-23S]
 Derive the relation for BOD at any time ‘t’ assuming the rate of consumption of oxygen
equivalent of organics follows first order kinetics. [M2024-25S]
 Explain the various methods of aeration used in water treatment plant. [M2022-23A]
 Differentiate between coagulation and flocculation. [M2022-23S]
 What is the principle behind the coagulation method of the water treatment process? [E2024-
25S]
 Explain the basic differences between coagulation and flocculation in details. [E2022-23S]
 Explain the water softening process citing the use of lime addition and lime-soda ash method
along with the reactions involved. [M2023-24A]
 Describe the following basic process variations of the Lime Soda ash softening process with
flow diagram: (a) Excess lime treatment (b) Selective Calcium removal (c) Split treatment
[M2023-24S]
 How to soften Mg(HCO3)2 associated wastewater, explain with reactions. [M2023-24S]

14. 14
 Lime soda-ash softening has three process variations - excess lime treatment, selective calcium
removal and split treatment. (i) Which of the above processes do not require recarbonation?
Why? (ii) Which of the above softening methods cannot remove hardness completely? Why?
[M2024-25S]
 Explain the chemistry of Lime-Soda Ash Softening with proper equations. [M2025-26A]
 Discuss the process variation in Lime Soda-Ash softening with neat schematic layout. [M2025-
26A]
 Explain the difference between Type I, Type II, and Type III sedimentation. Derive an
expression for terminal settling velocity of a spherical particle. [M2022-23S]
 Briefly explain the four types of settling of suspended particles. [M2024-25S]
 Explain different types of settling in sedimentation. [M2025-26A]
 Draw schematic showing different zones of a settling tank. [E2024-25S]
 Compare slow sand filters and rapid sand filters. [M2022-23S]
 Differentiate between slow sand and rapid sand filter. [M2022-23A]
 Briefly explain the method used to clean the rapid sand filters. [E2024-25S]
 Draw flow sheets showing the different unit operations in the treatment of (i) Ground water for
drinking applications (ii) Industrial wastewater. [E2022-23A]
 Draw flow sheets showing the different unit operations in the treatment of industrial
wastewater. Explain the function of each unit operation. [E2022-23S]
 Explain different processes of wastewater treatment. [E2023-24A]
 Describe different wastewater treatment processes in the industry. [E2023-24S]
 Describe preliminary, primary, secondary, tertiary, solid treatment and waste disposal processes
in wastewater treatment industry. [E2024-25A]
 Write a shorts on (a) Activated sludge process (b) Trickling Filter. [M2022-23A]
 Explain the working principle of oxidation pond of secondary treatment method. [E2022-23S]
 Write short notes on Oxidation ponds [E2023-24S]
 Explain different types of wetlands with diagrams. [E2025-26A]
Air Pollution and Control
 What do you mean by criteria air pollutants. Name five criteria air pollutants, the major sources
and health hazard associated with them. [E2022-23S]
 Explain electrostatic precipitator. [E2022-23A] [E2022-23S]
 What is drift or migration velocity in ESP? [E2024-25S]
 Explain at least two methods to control gaseous air pollutants. [E2022-23S]
 Write short notes on Lime Scrubbing [E2023-24S]
 Write a short note on the given Air pollution control equipments: (a) Venturi Scrubbers (b)
Wet scrubbers (c) Electrostatic Precipitators (d) Fabric Filter (e) Cyclone Separator [E2025-
26A]
Noise Pollution and Control
 Define sound pressure level (SPL). [E2024-25S]
Waste Management
 What are the different types of wastes? Classify solid waste and their effects. [E2024-25A]
 Write short notes on Solid-waste management approach. [E2023-24S]
 Briefly explain the five stages of waste management hierarchy. Also list the methods of disposal
for solid waste management. [E2024-25S]
 Discuss the 3R-based waste management Hierarchy. [E2025-26A]

15. 15
Safety Engineering
 Differentiate between Accident and Incident. [E2022-23S]
 Write a short note on Domino Theory and Heinrich’s Domino theory. [E2022-23S]
 What is the difference between an accident and an incident? Explain accident-incident theory
by introducing human factors theory [E2024-25S]
 Differentiate between hazardous conditions and hazardous practices with few examples.
[E2022-23S]
 Explain why basic causes of accident should be studied, and not the immediate causes. [E2022-
23A]
 Explain different sections of Occupational Safety and Health Administration. [E2024-25A]
 Write short notes on the Occupational Safety and Health Administration and Job Hazard
Analysis. [E2025-26A]
 Describe different types of hazards and hazard management process. [E2024-25A]
 Define (a) risk and (b) hazard. [M2022-23A] [E2022-23S]
 What are the different types of risk components and objectives of risk management? [E2024-
25A]
 What are risk management rules? [E2024-25A]
 Write short notes on (a) Risk management (b) JHA [E2023-24S]
 Show the relationship between hazard, accident, Job hazard analysis and accident investigation.
[E2022-23A]
 Explain briefly about Fault Tree Analysis (FTA) and how it is implemented.
 Write a comparative discussion between Job Hazard Analysis (JHA) and Hazard and
Operability (HAZOP). [E2022-23A]
 Write short notes on the followings: (a) HAZOP (b) OSHA [E2023-24A]
 What is meant by ergonomics. [E2022-23S]
 Compare ergonomic aspects of a big classroom and of an administrative office. [E2022-23A]