Download Revised_Major Exam Solution

Department of Civil Engineering-I.I.T. Delhi
CVL100: Environmental Science (1st Semester 2016-17)/Major Exam (120 minutes; 30 marks)
Name________________________Entry no_________________Gp no___________Serial no.
Q1. Please answer the following questions in one word or sentence: [1*15 = 15 marks]
(Negative marking: 0.5 marks will be deducted for each wrong answer)
a) A species is considered extinct when it’s last surviving member dies and has not been seen in wild
for the last 50 years.
b) The hotspots of biodiversity in India are Western Ghats and Eastern Himalayas.
c) The main difference between a National Park and a Wildlife sanctuary is that National Park is
funded and maintained Central Government and Wildlife sanctuary by State Government
with aid from Central Government.
d) CDM in Kyoto Protocol stands for Clean Development Mechanism.
e) Which of these is/are not considered in calculation of AQI in India: PM2.5, PM10, Hg, CO, CO2,
O3? (Hg, CO2)
f) The most common coagulant used in waste water treatment is Alum Al2(SO4)3 {also called
alum} or Fe2(SO4)3.
g) The toxic gas leaked in Bhopal gas tragedy was Methyl isocyanate.
h) The difference between drift velocity and terminal velocity is that drift velocity is the average
velocity that a particle attains due to an electric field and the terminal velocity is the
constant speed that a freely falling object eventually reaches when the resistance of the
medium through which it is falling prevents further acceleration.
i) The carcinogen released in Henkley Vs PG&E case was Cr6+
j) Gene bank is Ex-Situ measure of biodiversity conservation.
k) Which chemical was used by the U.S. military as a defoliant during the Vietnam War which
caused birth defects in the next generation? Agent Orange.
l) Which class of chemicals causes ozone depletion and hole? CFC (Chloro Fluoro Carbons).
m) If the BOD:COD ratio is 0.7, which treatment technique should be used? Biological
n) Waste water is made homogenous in treatment plants in Equalization Tank.
o) Disinfection of the tertiary treated wastewater is done by adding Chlorine.
Q2. 453 acres of a forest region X covering 650 acres of total area has been destroyed by
human activities. This region has 1562 species of vascular plants species that are endemic.
Can this region be classified as a hotspot of biodiversity? Give your reason. [5 marks]
To qualify as a biodiversity hotspot, a region must meet two strict criteria:
1. It must have at least 1,500 vascular plants as endemics (i.e. 0.5% of the world’s
total of 3,00,000).
2. It must have ≤30% of its original natural vegetation left.
Since only 453 acres of 650 acres i.e. 69.90 % has been destroyed by human activities
which is less than 70 %. Since the 2nd condition is not met therefore this region cannot
be classified as Hot Spot of biodiversity.
Q3. A particle of mass 0.025 g is traveling in a gas stream with velocity 50 ft/s and radius 1.2
ft. What is the ratio of centrifugal force to the gravity force acting on it? Will the particle
drop down immediately or remain suspended for long time. Give your reason.
[5 marks]
Centrifugal Force Fc= mVc2/r
= 0.025*(50)2/1.2 = 52.08 g-ft/s2
Gravity Force Fg = mg = 0.025*32.2 ft/s2 = 0.805 g-ft/s2


Ratio: Fc / Fg = 52.08/0.805 = 64.696
Since Fc >> Fg ; the particle will remain suspended for a long time.
Q4. The efficiency of an ESP is 98%. The efficiency of the ESP drops to 93% as a result of
flow rate changes. Calculate the ratio of flow rates for the above situation using appropriate
assumptions.
[5 marks]
Overall Efficiency, ηo of electrostatic precipitator is given by:
Where,
A
=
area of collection electrodes
Q
=
volume flow rate
we
=
effective drift velocity )
Ratio of flow rates
Q2/Q1 = ln(1-0.98)/ln(1-0.93) = 1.47109