GATE 2026 Question Paper Environmental Science and Engineering (ES)

FOR GATE EXAM PREPARATION

GATE 2026
Question Paper ·
Environmental Science
Engineering (ES)
EXAM YEAR TYPE SUBJECT

GATE 2026 Question Paper Environmental Science Engineering (ES)

Notes · Sample Papers · Previous Year Papers · Mock Tests

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Environmental Science & Engineering (ES)

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General Aptitude (GA)
Q.1 – Q.5 Carry ONE mark Each

Q.1 Suresh said, “I did it yesterday.”

Which one of the following options is the correct form of this sentence in indirect
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speech?
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(A) a Suresh said that I did it yesterday.

(B) Suresh says I did it yesterday.

(C) Suresh says that he did it the day before.

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(D) Suresh said that he had done it the day before.

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Environmental Science & Engineering (ES)

Q.2 To continue the sequence of tiles shown, the tile indicated by the question mark
should be

(A)

(B)

(C)

(D)

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Q.3 Consider an art gallery whose walkways are shown as lines in the diagram. A
black dot represents a junction of two walkways. A guard may be placed at a
junction to watch over the walkways that join at that junction. The minimum
number of guards needed to watch all the walkways is ________.

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(A) 2
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(B) 3
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(C) 4 a
(D) 5

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Environmental Science & Engineering (ES)

Q.4 The 2nd of June is a Thursday in a certain year. Which day of the week is the
3rd of July in that year?

(A) Thursday

(B) Friday

(C) Saturday

(D) Sunday

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Q.5 A coin with heads facing up is shown as and a coin with tails facing up is
shown as .

Six coins are placed in the Starting Arrangement, as shown in the figure below.
A “step” is defined as interchanging a pair of adjacent coins without flipping
them. The minimum number of steps needed to go from the Starting Arrangement
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to the Final Arrangement, as shown in the figure, is ________.
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(A) 3

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(B) 6

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(C) 9
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(D) 12

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Environmental Science & Engineering (ES)

Q.6 – Q.10 Carry TWO marks Each

Q.6 Exacerbate : Mitigate :: ___________

Choose the option with the correct pair of words to fill the blank.

(A) Aggravate : Alleviate

(B) Alleviate : Precipitate

(C) Aggravate : Precipitate

(D) Emancipate : Exonerate

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Q.7 A paper shown in Panel I is folded along the dashed lines (- - -) to construct a
cube. The shaded regions shown in Panel I appear on the outer surface of the cube.
Referring to cubes shown in Panel II, which one of the options is correct?

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(A) Only (i) can correspond to the unfolded cube in Panel I.

(B) Only (ii) can correspond to the unfolded cube in Panel I.

(C) Both (i) and (ii) can correspond to the unfolded cube in Panel I.
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(D) Neither (i) nor (ii) can correspond to the unfolded cube in Panel I.
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Environmental Science & Engineering (ES)

Q.8 In a population, patients who have high cholesterol also have high blood-pressure
(BP). Some patients with high BP also have diabetes. There are no patients who
have both high cholesterol and diabetes. Furthermore,

1. the total number of patients with at least one of these conditions is 75,
2. the number of patients with high cholesterol is 10,
3. the number of patients with high BP is 45, and
4. the number of patients with only high BP and no other conditions is 20.

Then the number of patients who have both diabetes and high BP is _______

(A) 0

(B) 15

(C) 20

(D) 10

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Q.9 Four people P, Q, R, and S, of different ages, make the following observations.

P – I am younger than S.

Q – I am neither the youngest nor the oldest.

R – P is older than me. m
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Based on these observations, the youngest person is ______.
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(A) P

(B) Q

(C) R
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(D) S
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Environmental Science & Engineering (ES)

Q.10 Circles 𝐶1 , 𝐶2 , and 𝐶3 , with centers 𝑂1, 𝑂2, and 𝑂3 , and radii 𝑟1 , 𝑟2 , and 𝑟3 ,
respectively, touch each other as shown in the following figure. Given 𝑟1 = 2 cm,
𝑟2 = 1 cm and the angle ∠𝑂1 𝑂3 𝑂2 is 90°, 𝑟3 = _____ cm.

(A) 1
(−3 + √17 )
2

(B) 1
(3 + √17 )
2

(C) 1
(−2 + √17 )
2

(D) 1
(−3 + 2√17 )
2

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Q.11 – Q.35 Carry ONE mark Each

Q.11 1 2 3 8
If 2𝑋 + [ ]=[ ], then X is ______.
3 4 7 2

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(A) 2 5 .co s e m
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[ ]
s
5 3
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(B) a [
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−1
a
3
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]
2 −1

(C) [
1 3
]
2 −1

(D) 1 0
[ ]
0 1
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sin 𝑥
Q.12 The correct integral of ∫ 𝑑𝑥 (assuming integral constant as c) is ______.
√1+cos 𝑥

(A) 𝑥
−2√2 sin + 𝑐
2

(B) 𝑥
−2√2 cos + 𝑐
2

(C) 1 𝑥
− cos +𝑐
√2 2

(D) 1 𝑥
− sin +𝑐
√2 2

Q.13 Given 𝑓(𝑥) = 3𝑥 4 + 4𝑥 3 − 12𝑥 2 + 6 , the minimum value of 𝑓(𝑥) is ______.

(A) −6

(B) −36

(C) −26

(D) −46

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Q.14 A box contains 26 cards with all English alphabets from A to Z.

The probability of randomly choosing the card with either ‘E’ or ‘S’ from this box
is ______.

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(A) 2/26
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(B)
a 1/26

(C) 3/26

(D) 4/26

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Q.15 Which ONE of the following options is the CORRECT formula for Chi-Square
(χ2) test?

Given, 𝑂1 , 𝑂2 , … . . 𝑂𝑛 are the observed values, 𝐸1 , 𝐸2 , … . . 𝐸𝑛 are the corresponding
expected values, 𝑂̅ is the mean of observed values, , n is the number of observations,
µ is the mean of 𝐸𝑖 , 𝑖 = 1, … , 𝑛, 𝜎𝑜 is the standard deviation of observed values, and
𝜎𝐸 is the standard deviation of expected values 𝐸𝑖 , 𝑖 = 1, … , 𝑛.

(A) χ2 = ∑ni=1
(𝑂𝑖 −𝐸𝑖 )2
𝐸𝑖

(B) ∑𝑛 (𝑂 −𝑂̅)
χ2 = √ 𝑖=1𝑛−1𝑖

(C) χ2 =
𝑂̅ −𝜇
𝜎𝑜 √𝑛

(D) (𝜎 )2
χ2 = (𝜎𝑜 )2
𝐸

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Q.16 In the reversible reaction shown below, 𝑘𝑓 is the forward reaction rate constant and
𝑘𝑟 is the reverse reaction rate constant.

The CORRECT expression representing the reaction equilibrium constant is
______.

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(A) 𝑘𝑓 + 𝑘𝑟

(B) 𝑘𝑓 × 𝑘𝑟

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(C) 𝑘𝑓
𝑘𝑟
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(D) 𝑘𝑟
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𝑘𝑓

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Q.17 The major class of enzymes catalyzing the cleavage of 𝐶 − 𝐶, 𝐶 − 𝑂, 𝐶 − 𝑁, or
other bonds by elimination, leaving double bonds or rings, or addition of groups to
double bonds in any biochemical reactions is ______.

(A) lyases

(B) transferases

(C) oxidoreductases

(D) hydrolases

Q.18 Malaria is caused by pathogenic _____.

(A) bacteria

(B) fungi

(C) protozoa

(D) viruses

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Q.19 Consider the following statements regarding the pressure measured at a point in a
fluid.

S1: Absolute pressure is gauge pressure plus atmospheric pressure.

S2: Gauge pressure is measured by considering absolute zero pressure as datum.
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S3: Absolute pressure is measured by considering atmospheric pressure as datum.
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. pressure is negative pressure obtained by subtracting absolute pressure se
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S4: Vacuum
s
from atmospheric pressure.
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(A) S1 and S2

(B) S2 and S3
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(C) S1 and S4
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(D) S1, S2, and S4 a

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Q.20 Which ONE of the following options CORRECTLY matches the processes
associated with the growth condition given in the table?

Process Growth Condition

(P) Activated sludge process (i) Anaerobic suspended growth

(Q) Anaerobic filter (ii) Anaerobic attached growth

(R) Trickling filter (iii) Aerobic suspended growth

(S) Anaerobic digestion (iv) Aerobic attached growth

(A) (P) - (ii); (Q) - (iii); (R) - (iv); (S) - (i)

(B) (P) - (iii); (Q) - (ii); (R) - (iv); (S) - (i)

(C) (P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)

(D) (P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

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Q.21 In the design of air pollution control devices, size of the particles that are removed
with 50% efficiency is termed as ______.

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(A) mean size
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(B)
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mode size l a
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(C) a cut size

(D) median size

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Q.22 The general atmospheric composition of gases in the decreasing order is ______.

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(A) N2 > O2 > CO > CO2 > NH3

(B) N2 > O2 > CO2 > CO > NH3

(C) N2 > CO2 > O2 > NH3 >CO

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(D) N2 > CO2 > NH3 > CO > O2
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Q.23 Which ONE of the following options is NOT a parameter as a part of proximate
analysis of municipal solid waste?

(A) Volatile matter

(B) Ash content

(C) Carbon to nitrogen ratio

(D) Moisture content

Q.24 A species whose impact on an ecosystem is disproportionately large in comparison
to its population is called ______ species.

(A) dominant

(B) keystone

(C) apex predator

(D) endemic

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Q.25 Which ONE of the following principles is directly related to environmental
compensation?

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(A)
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Intergenerational equity principle
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(B)
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Precautionary principle l a
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(C) a Subsidiarity principle

(D) Polluter-pay principle

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Q.26 As per the United Nations General Assembly resolution adopted in 2015
“Transforming Our World: The 2030 Agenda for Sustainable Development”, the
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s
number of sustainable development goals (SDGs) is ______.
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(A) 4

(B) 15

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(C) 17
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Q.27 Which ONE of the following options CORRECTLY matches the ISO series with
their usages in environmental management system (EMS) given in the table?

ISO Series Environmental Management System

(P) ISO 14001 (i) Environmental labeling

(Q) ISO 14020 (ii) Evaluation of environmental management system

(R) ISO 14040 (iii) Addressing environmental aspects of products

(S) ISO 14060 (iv) Life cycle assessment procedure

(A) (P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)

(B) (P) - (ii); (Q) - (i); (R) - (iv); (S) - (iii)

(C) (P) - (iii); (Q) - (iv); (R) - (i); (S) - (ii)

(D) (P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

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Q. 28 Which of the following chemical reactions is/are related to smog formation in the
troposphere?

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(A)
m
𝐶𝐹𝐶𝑙3 + ℎ𝜐 → 𝐶𝐹𝐶𝑙2 + 𝐶𝑙∙
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(B)
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𝐶𝐻3 𝑂2 + 𝑁𝑂 + 𝑂2 → 𝐻𝐶𝐻𝑂 + 𝐻𝑂2 + 𝑁𝑂2

g la
(C) a 𝑁𝑂 + 𝑂 + ℎ𝜈 → 𝑂 + 𝑁𝑂 𝑀
2 2 3

(D) 𝐶𝐻4 + 8𝑂2 → 𝐶𝑂 + 𝐻2 𝑂 + 2𝑂𝐻∙ + 4𝑂3

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Q.29
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Which of the following processes is/are primarily used to remove the organic matter
in sludge? m
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(A) Digestion

(B) Incineration

(C) Magnetic separation m
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m Wet-oxidation
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Q.30 Which of the following options is/are CORRECTLY listing the species included in
Total Kjeldahl Nitrogen (TKN) estimation of an aqueous sample?

(A) Ammoniacal − N

(B) Nitrite − N

(C) Nitrate − N

(D) Organic − N

Q.31 Which of the following statements is/are CORRECT in the context of hazardous
waste management and its risk assessment?

(A) Risk is estimated based on the probability of an action occurring multiplied by the
severity of damage.

(B) High octanol water constant (𝐾𝑂𝑊 ) is indicative of lower accumulation of an
organic chemical in body tissue.

(C) Pump and treat is an example of contaminated groundwater remediation.

(D) Biological treatment processes are never applied for hazardous waste management.

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Q.32 Which of the following statements is/are TRUE about global warming?

(A) Interception of incoming solar radiation by greenhouse gases in earth’s
m
m
atmosphere is responsible for global warming.
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(B)
s e
Interception of outgoing longwave radiation by greenhouse gases in earth’s l a
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atmosphere is responsible for global warming. ag
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(C) Global warming can cause sea level rise.

(D) Carbon dioxide is one of the major greenhouse gases in earth’s atmosphere
responsible for global warming.

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Q.33
s e
Which of the following options is/are directly associated with the steps involved in
la
carrying out life cycle assessment (LCA)?
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a

(A) Determination of functional unit

(B) Defining goal and scope
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(C) Defining technology readiness level
e m
e m l as
las (D) Listing out inventory of inputs and outputs
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Q.34 A 6-hour rainfall of 6 cm at a station was found to have a return period of 40 years.

The probability that a 6-hour rainfall of this or larger magnitude will occur at least
once in 20 successive years at that station is ______ (rounded off to three decimal
places).

Q.35 Water is flowing at the rate of 15 m3/s through a rectangular channel of 5 m width.

If the acceleration due to gravity (g) is 9.81 m/s2, the critical velocity for the flow
is ______m/s (rounded off to three decimal places).

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Q.36 – Q.65 Carry TWO marks Each

Q.36 A first-order ordinary differential equation is given as follows:

𝑑𝑦
+ 𝑥2𝑦 = 0
𝑑𝑥
m
Which ONE of the following options CORRECTLY represents the characteristics of
m .co
.co m
this equation?

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(A) Linear, homogeneous, and exact

(B) Nonlinear, nonhomogeneous, and exact

(C) Linear, homogeneous, and non-exact

m
(D) Nonlinear, nonhomogeneous, and non-exact
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Q.37 2 2 3
Consider the matrix 𝐴 = [2 5 6 ].
3 4 10
Which ONE of the following options CORRECTLY lists the eigenvalues of 𝐴?

(A) 1; 8 − √37; −8 + √37

(B) 2; 8 − √37; −8 + √37

(C) 1; 8 + √37; 8 − √37

(D) 2; 8 + √37; 8 + √37

Q.38 Which ONE of the following options is CORRECT with respect to sequential
breakdown of deoxyribonucleic acid (DNA) into lower-molecular weight
compounds?

(A) Deoxyribonucleic acid  2-deoxyribose  Nucleosides  Nucleotides

(B) Deoxyribonucleic acid  2-deoxyribose  Nucleotides  Nucleosides

(C) Deoxyribonucleic acid  Nucleotides  Nucleosides  2-deoxyribose

(D) Deoxyribonucleic acid  Nucleosides  Nucleotides  2-deoxyribose

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Q.39 Which ONE of the following options CORRECTLY matches the Criteria Air
Pollutants with measurement methods used in Continuous Ambient Air Quality
Monitoring Stations (CAAQMS) operated by Central Pollution Control Board
(CPCB) given in the table?

Criteria Air Pollutants Measurement Methods
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3
(P) Sulphur Dioxide (SO2, in µg/m ) (i) Chemiluminescence
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(Q) Nitrogen Dioxide (NO2, in µg/m ) 3
(ii) Non Dispersive Infra
l as
l as Red (NDIR) spectroscopy
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ag(R) Particulate Matter (PM in µg/m ) (iii) Ultraviolet
2.5,
3

fluorescence

(S) Carbon Monoxide (CO, in mg/m3) (iv) Beta attenuation

o m
(A) (P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv) .c
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(B) (P) - (iv); (Q) - (iii); (R) - (ii); g la- (i)
(S)
a
(C) (P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)

(D) (P) - (ii); (Q) - (iii); (R) - (i); (S) - (iv)

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Q.40 Which ONE of the following options CORRECTLY matches the atmospheric
stability conditions with plume conditions/ behaviours given in the table?

Atmospheric Stability Plume Conditions/
Conditions Behaviours

(P) Strong instability (i) Fanning plume

(Q) Neutral stability (ii) Fumigation

(R) Surface inversion (iii) Coning plume

(S) Aloft inversion (iv) Looping plume

(A) (P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)

(B) (P) - (iv); (Q) - (iii); (R) - (i); (S) - (ii)

(C) (P) - (iii); (Q) - (iv); (R) - (ii); (S) - (i)

(D) (P) - (ii); (Q) - (i); (R) - (iv); (S) - (iii)

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Q.41 The analysis of a water sample is shown in the table. The hardness of the water
sample is ______ mg/L as CaCO3.

Atomic weight (g/mol): Ca = 40; Mg = 24; Na = 23; Cl = 35.5; S = 32; O = 16;
N = 14

m
m .co
Species Concentration (mg/L)

m .co Na+ 30
s e m
s e l a
g l a Ca2+ 10
ag
a Mg2+ 15

Cl- 30

SO42- 60

NO3- 5

m
m .co
s e
(A) 87.5
g la
a
(B) 62.5

(C) 25.5

(D) 47.5

m
m .co
m .co s e m
s e g l a
g la a
a

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.co s e m
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Q.42 A system of linear equations is given as 𝐴𝑋 = 𝐵,

2 5 7
where 𝐴 = [ ], 𝐵 = [ ], and 𝑋 is the solution vector.
5 −2 3
Which of the following statements is/are TRUE for this system?

(A) Matrix 𝐴 is skew-symmetric.

(B) Eigenvalues of matrix 𝐴 are real.

(C) The system is homogeneous.

(D) The system is singular.

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Q.43 Which of the following statements is/are CORRECT based on the electron donor
(ED) and electron acceptor (EA) used in various bacterial mediated reactions in
wastewater treatment?

m
m .co
(A)
.co
In anaerobic heterotrophic acid fermentation, organic compounds are used as both
s e m
em
ED and EA.
s g l a
l a a
ganaerobic heterotrophic methanogenesis, volatile fatty acids and CO are used as
(B)
aInED and EA, respectively.
2

(C) In denitrification process by denitrifiers, organic compounds and CO2 are used as
ED and EA, respectively.

(D) In aerobic autotrophic iron oxidation, Fe(II) and O2 are used as ED and EA,
respectively. m
.co
s em
g la
a
Q.44 Which of the following options is/are TRUE about reverse osmosis process?

(A) Reverse osmosis is used as a pretreatment for microfiltration process.

m
(B)
m Ultrafiltration is used as a pretreatment for reverse osmosis process.
.co
m .co s e m
s e (C)
l a
Membrane fouling occurs in microfiltration and reverse osmosis processes.

g la ag
a (D) Concentration polarization does not occur in reverse osmosis process.

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.co s e m
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Q.45 Which of the following options is/are TRUE about coagulation-flocculation process?

(A) Collision of colloidal particles due to their Brownian motion results in orthokinetic
flocculation.

(B) Collision of colloidal particles due to the external mixing of bulk medium results
only in perikinetic flocculation.

(C) In an electric double layer model of a colloidal particle, Stern layer is more compact
than the diffuse layer.

(D) The zeta potential is also called Stern potential.

Q.46 Which of the following options is/are CORRECT assumption(s) in the Gaussian
plume dispersion model?

(A) The concentration of pollutants emitting from stack is continuous.

(B) The process is under steady state.

(C) The pollutants emitted are non-conservative.

(D) The diffusion of pollutants is dominant in comparison with advection in the
direction of wind.

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Q.47 The sound level measured at various locations in an urban area is given in the table.

The average sound level for that area is ______ dBA (rounded off to two decimal
places).

Location A B C D
m
m .co
.co
Sound level 40 55 65 75
e m
e m
(dBA)
l as
l as ag
ag
Q.48 Standard deviation for the particulate matter (PM) concentrations listed in the table
is ______ µg/m3 (rounded off to one decimal place).

Location No. 1 2 3 4 5 6 7

m
PM concentration
45 40 55 65 60 35 50
(µg/m3)
c. o
s em
g la of 1 atm and at 300K is reported as 340 ppmv.
a
Q.49 The mixing ratio of CO at a pressure 2

Considering ideal gas conditions, the equivalent concentration of CO2 in air is ______
mg/m3 (rounded off to two decimal places).

The molecular weight of CO2 = 44 g/mol

Universal gas constant = 8.314 J/mol-K

m
m
Q.50 Reaction A  B follows first-order elementary kinetics and the reaction rate constant
.co
m .co for A is 0.01 per min.
s em
s e The time taken to reduce the concentration of A from 100 M
reactor is ______min (rounded off to one decimal place). ag
lato 10 M in a batch
g la
a

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Q.51 The following two reactions describe the chemistry of S(IV) in an aquatic system.

Under ideal conditions, the equilibrium constants for reactions (i) and (ii) are 1.3 ×
10−2 M (KS1) and 6.6 × 10−8 M (KS2), respectively.

If the pH of the system is 4.0 and the equilibrium concentration of SO2(aq) is 1.0 M,
the equilibrium concentration of SO2− 3 is ______ mM (rounded off to one decimal
place).

𝑆𝑂2(𝑎𝑞) ⇌ 𝐻 + + 𝐻𝑆𝑂3− (i)

𝐻𝑆𝑂3− ⇌ 𝐻 + + 𝑆𝑂32− (ii)

Q.52 The calibration graph between absorbance and the concentration of chromate
(CrO42-) in a water sample is shown in the figure.

For an absorbance of 0.35 in a water sample, the estimated Cr(VI) concentration is
______ mg/L (rounded off to two decimal places).

Use the atomic weight (g/mol) of Cr and O as 52 and 16, respectively.

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Q.53 In a batch culture experiment, 2 cells of a microorganism were added to a growth
medium. During the experiment, a lag phase of 1 hour was first experienced by the
added cells, in which no cell multiplication occurred. Afterwards, cells started
multiplying exponentially with a doubling time of 1 hour.

After total 8 hours of experiment, the number of cells present in the growth medium
m
.co
was ______ (answer in integer).

o m m
. c at a specific temperature, results in 2-log removal of non- se
s em pathogenic microorganisms from a water sample in 20 min.
Q.54 A thermal process,
thermotolerant
g l a 10

g l a a
acondition is ______ min (answer in integer).
The time needed to achieve 99.999% removal of these microorganisms under similar

Q.55 A cylindrical roller gate of diameter 6.0 m and length 10.0 m is placed on a dam to
store water behind it, as shown in figure.

The magnitude of the resultant force due to water acting on that gate when the water
is about to spill is _______ × 106 N (rounded off to two decimal places).
m
Consider acceleration due to gravity (g) = 9.81 m/s2;
m .co
s e
la
density of water (ρ) = 1000 kg/m3; and π = 3.14.

ag

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Q.56 The mass curve of a rainfall event of 100 min duration over a catchment is given in
the table.

If the initial loss is 0.6 cm and 𝜙-index is 0.6 cm/hour, the total surface runoff from
the catchment is ______ cm (rounded off to one decimal place).

Time from start of 0 20 40 60 80 100
rainfall (min)

Cumulative rainfall (cm) 0 0.5 1.2 2.6 3.3 3.5

Q.57 A well penetrates an unconfined aquifer. The water level (i.e., head) in the well prior
to pumping is 25 m. After a long period of pumping at a constant rate of 0.05 m3/s,
the drawdowns at distances of 50 m and 150 m from the well are observed to be 3 m
and 1.2 m, respectively.

The hydraulic conductivity of the unconfined aquifer is ______ × 10−4 m/s (rounded
off to two decimal places).

Consider π = 3.14.

Q.58 A sewage treatment plant employing activated sludge process is operated under the
following conditions:

Wastewater flow rate into the aeration tank = 0.150 m3/s

Soluble BOD5 in the influent = 84 mg/L

Soluble BOD5 in the effluent = 11 mg/L

Mean cell residence time = 5 days

Total yield co-efficient = 0.5 kg of MLVSS/kg BOD5 removed

Decay rate of microorganism = 0.050/day

The net waste activated sludge produced in the plant is ______ kg of VSS/day
(rounded off to two decimal places).

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Q.59 A continuous flow stirred tank reactor (CSTR) operates under a steady-state
condition with a flow rate of 300 L per hour. The influent concentration of a substrate
entering the reactor is 150 mg/L.

To give a treatment efficiency of 76% for the substrate that decays according to half-
order kinetics with a rate constant of 0.05 (mg/L)1/2 per hour, the required volume of
m
.co
the reactor is ______ m3 (answer in integer).
m
.co e m
s ememission measurement at an industry, the stack cross-sectional area atglas
a height was divided into four equal sectors. The measured velocities and SO
Q.60 In a stack
30 lm
g a
aconcentrations through these sectors at this height are given in the table.
2

The mean SO2 concentration from the stack is ______ mg/m3 (rounded off to two
decimal places).

Sector Velocity SO2 Concentration
Number (m/s) (mg/m3)

1 15
o m 1000
.c
2
s em17 1150

3
g la19 1250

4
a 21 1275

Q.61 An anaerobic digestion system is operated for methane gas generation from organic
fraction of municipal solid waste (OFMSW). The moisture content and volatile solids
(VS) content of OFMSW are 20% and 90%, respectively. The biodegradable volatile
solids (BVS) in the VS is 70%, and the BVS conversion efficiency to methane gas is
85%.
o m
m . c
c. o Iftotalthevolume
3

e m
methane gas generation in the system is 12 m per kg of BVS converted, the
s
3
of gas produced from one kilogram of OFMSW is _______ m (rounded
e m l a
l as off to two decimal places).
ag
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Q.62 The characteristics of two types of solid waste are given in the table.

The quantity of sludge to be added to leaves to achieve a C/N ratio of 25 (on dry
basis) for the mixed waste is ______ kg of sludge/kg of leaves (rounded off to three
decimal places).

Characteristics of the solid waste (weight/weight)
Type of solid
waste Moisture Nitrogen Carbon to Nitrogen
content (%) content (%) (C/N) ratio

Leaves 50 0.7 50

Sludge 75 5.6 6.3

Q.63 The concentration of chemical A in ambient air is 50 g/m3 and the toxicological
index limit for a threshold health effect for this chemical is 5 mg.

If the average breathing rate is 4 L/min, the minimum time of exposure that can
lead to any health effect is ______ days (rounded off to one decimal place).

Q.64 The area in the first quadrant bounded by the function 𝑦 = (8 − 𝑥) and the
coordinate axes is ______ square units (answer in integer).

Q.65 An agricultural land can support energy crops yield to produce 7000 L of bioethanol
per hectare and energy content of bioethanol is 21 MJ/L. This bioethanol displaces
fossil-based petrol.

The CO2 offset potential of land used for growing energy crops as a bioethanol
feedstock is ______ × 106 g of CO2 /hectare (rounded off to one decimal place).

Consider CO2 footprints of 10 g and 80 g of CO2 per MJ for bioethanol and petrol,
respectively.

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