2. Chapter: 3
Air & Noise Pollution (12 hours)
Air Pollution
Air quality, air pollution and its effects.
Air quality control and treatment of emission products.
Noise Pollution
Effects of noise on health, measurement of noise.
Reduction and control of noise.
Course Outcome
Discuss the types, sources and treatment of air pollution.
Describe noise pollution and effects on environment.
2
3. Pure air is a mixture of gases, containing,
on a dry volume (or molar) basis,
• 78.1% nitrogen
• 20.9% oxygen
• 0.9% argon
• 0.04% carbon dioxide
• 0.002% neon
• 0.0005% helium and so on.
But such air is not found in nature and is of
interest only as a reference.
4. Air pollution is the presence in the outdoor
atmosphere of one or more air contaminants
(i.e., dust, fumes, gas, mist, odour, smoke, or
vapour) in sufficient quantities, of such
characteristics, and of such duration as to be or
to threaten to be injurious to human, plant, or
animal life or to property, or which reasonably
interferes with the comfortable enjoyment of life
or property’
DEFINITION
5. Pollutants can be classified into THREE that are:
1) Origin
Primary pollutants
Materials that when released pose health risks in their
unmodified forms or those emitted directly from identifiable
sources.
Such as SOx, NOx and hydrocarbon (HC) are those emitted
directly to the atmosphere and were found in the form in which
they were emitted.
Secondary Pollutants
Primary pollutants interact with one another, sunlight, or natural
gases to produce new, harmful compounds.
Such as O3 and peroxyacethyl nitrate (PAN) are those formed
in the atmosphere as the result of chemical reactions among
the primary pollutant and chemical species present in the
atmosphere.
CLSSIFICATION OF POLLUTANTS
6. 2) Chemical Composition
Organic compounds – contain carbon & hydrogen, and may
also contain element such as O, N , P and S.
Inorganic compounds – found in contaminated atmosphere
include CO, CO2, carbonates, SOx, NOx,O3, HCl.
7. 3) State of Matter
Particulate pollutants – finely divided solids and liquids,
include dust, fumes, smoke, fly ash, mist and
spray.Under proper properties, particulate pollutant will
settle.
Gaseous pollutants – formless fluids that completely
occupy the space into which they are released, behave
more as air & do not settle down. Including vapors of
substance that are liquid or solid at normal Pressure &
T. e.g: COx, SOx, NOx, HC and oxidants.
9. - The filter is weighted before and after and the difference
is the particulates collected
- the air flow is measured by a small flow meter, usually
calibrated every 24 hours because its get dirty during 24
hours of operations.
- Less air goes through the filter during later part of the
test than the beginning. Therefore air flow has to
measure at both points , starting and ending points.
- since the later part has different air flow than the
beginning, air flow value it’s the average value of the
start and end of the test.
Air Quality Measurements
10.
11.
12.
13. Gaseous measurements
The concentration of gasses can be either part per million
(ppm) on a volume to volume basis or micrograms per
cubic meter.
ppm means 1 volume of pollutants per 106 volume of Air.
Converting µg/m3 needs to know the molecular weigh of
the gas. At standard condition 00C and 1 Atmosphere
pressure, one mole of gas occupies 22.4 L while at 250C
and 1 Atmosphere pressure, one mole of gas occupies
24.5 L
Air Quality Measurements
14. Air Quality Measurements
ppm
x
4
.
22
1000
MW x
m
ug
g
g
10
x
mole
/
m
10
x
L
4
.
22
(g/mole)
MW
x
m
10
pollutants
m
1
3
6
3
3
-
3
6
3
Ex 2: A stack gas contains carbon monoxide (CO) as a
concentration of 10% by volume. What is the concentration of
(CO) in microgram per cubic meter. If CO MW is 28 g/mol,
assume 250C and 1 Atmosphere pressure.
SoL. 28 X 1000 X 100, 000/24.5 = 114 X 106 µg/m3
15. UNITS OF MEASUREMENT
•There are 3 basic units used in reporting air pollution data that are
micrograms per cubic meter (µg/m3), parts per million (ppm) and the
micron (µ) or preferably known as micrometer (µm).
•Micrograms per cubic meter and parts per million are unit of
measurement for concentration and they are used to indicate the
concentration of gaseous pollutant.
•The µm is used to report the particle size.
•Formerly concentration of gaseous pollutants were usually reported
in parts per million (ppm), parts per hundred million (pphm), or parts
per billion (ppb) by volume.
•Thus, designations in µg/m3 may be followed by equivalent
concentration on a ppm basis - e.g. 80 µg/m3 (0.03 ppm) of sulfur
dioxide.
16. •For gases, ppm can be converted to µg/m3 by using the following
formula:
µg/m3 = ppmx 10-6 xGMW x103 L/m3 x106 µg/g
L/mol
GMW = gram molecular weight of gas
•‘L/mol’ term is influenced by the temperature (T) and pressure (P) of
the gas. According to Avogadro’s Law, 1 mole of any gas occupies
the same volume as 1 mole of any gas at the same T and P.
•Therefore, at 273 K (0OC) and 1 atm pressure (760 mmHg /101.3
kPa), standard conditions for many chemical reactions, the volume is
22.4 L/mol.
17. To convert to L/mol at other conditions, the
following formula can be used:
V1P1 = V2P2
T1 T2
where V1, P1 and T1 is relate to the standard condition V2, P2 and T2 is
relate to the actual condition that is being considered.
18. EXAMPLE :
Calculate the volume occupied by 4 mol of gas at 21.1OC and
760 mmHg.
SOLUTION:
V1P1 = V2P2
T1 T2
V1 = 22.4 L/mol P1 = 760 mmHg T1 = 273K
V2 = ? P2 = 760 mmHg
T2 = 21.1+273 = 294.1K
4mol x 22.4 L/mol x 760mmHg = V2 x 760mmHg
273K 294.1K
V2 = 96.53 L
19. DO IT YOURSELF
Determine the volume of 3 mol of stack gas at 1400 mmHg
and 1000OC.
Ans: 170.12 L
20. EXAMPLE :
The NO2 content of a sample of stack gas measured at
950OC at 2 atm pressure was 9 ppm. Determine the NO2
concentration in µg/m3 and mg/m3. NO2 weight 46 g/mol.
SOLUTION:
Step 1 – Find V2
V1P1 = V2P2
T1 T2
22.4L/mol x 1 atm = V2 x 2 atm
273K (273K + 950)
21. V2 = 50.17 L/mol
Step 2 – Substitute V2 in Equation 1
µg/m3 = ppm x 10-6 x GMW x 103 L/m3
L/mol
µg/m3 = 9 x 10-6 x 46 g/mol x103 L/m3 x 106 µg/g
50.17 L/mol
= 8251.94 µg/m3 = 8.252 mg/m3
22.
23. DO IT YOURSELF
Gas from thermal pool has an SO2 content of 80 µg/m3
at 104.2 kPa and 50OC. Calculate the SO2
concentration in ppm.
24. EXAMPLE :
What volume would one mole of an ideal gas occupy at
25.00C and 101.325kPa?.
SOLUTION:
26. EXAMPLE :
Convert 7.5 ppm of 64 g/mol SO2 to µg/m3 at 80OC and
110.5 kPa.
SOLUTION:
Step 1: Find V2
27. Step 2: Calculate SO2 concentration in μg/m3
3
3
g/m
18.072
7.5
x
mol
L
26.56
x1000
mol
g
64
ppm
x
mol
L
56
.
26
1000
MW x
m
ug
28. Effects of Acidic Rain
-The potential effects of acid rain are relates to
the acidity on aquatic life, damage to crops and
forests, and damage to building materials.
-Lower pH values may affect fish directly by
interfering with reproductive cycles or by
releasing otherwise insoluble aluminium (Al),
which is toxic.
Acid rain also leaches calcium (Ca) and
magnesium (Mg) from the soil thus lower the
molar ratio of Ca to Al which in turn, favours the
uptake of Al by fine roots, that ultimately leads
to their deterioration.
30. AIR Quality Control
Selection of treatment devices will be depend on :
1- Size of Air pollutant
2- Type of Air pollutant, such as SO2 can clean by
water spray but the result is corrosion problem.
Therefore, are divided into different types for Air
pollutant control process.
31. AIR Quality Control
Where:
Xo : Amount of pollutant entering the device per unit time (kg/s)
X1 : Amount of pollutant collected by treatment device per unit
time (kg/s)
X2 : Escaped particles (kg/s)
Xo
X1
X2
32. AIR Quality Control
Where:
R: Treatment device removal efficiency
Concentration of emission will be equal to the mass
per volume.
Principles of mass balance will be valid for this process
100%
x
X
X
R
o
1
1
33. AIR Quality Control
EX: An air pollution control device is to remove a
particulate that is being emitted at a concentration
of 125000 µg/m3 at an air flow rate of 180 m3/s. the
device removes 0.48 metric ton per day. What are
the emission concentration and the collection
recovery?
42. 1) Gravity settlers
Easy to construct
Requires littlie maintenance
Treating very dirty gases in some industries
Contaminated gas passes slowly, allowing time for
the particles to settle by gravity to the bottom.
Particles with diameters greater than 50µm to 100
are effectively removed
43.
44.
45. Settling chamber Design
Settling chambers are typically designed having
a velocity less than 3 m/s, best results being
obtained with velocities less than 0.3 m/s.
For a particle that enters the top of the collector
and is removed, the time for the particle to fall the
collector height H must be less than or equal to
the time of the horizontal movement within the
collector.
46. Centrifugal separators
The disadvantage of gravity settlers is not
effective in small particles.
Therefore, it has to find a substitute that is
more powerful then the gravity force to drive
the particles to the collection surface.
47. AIR Quality Control
Cyclone Collector
Cyclones provide a low cost, low maintenance
method of removing larger particulates from a
gas stream.
Mechanism
1- The particulate is forced to change direction.
2- The particles continue in the original
direction and be separated from the
stream.
3- The walls of the cyclone narrow towards the
bottom of the unit allowing the particles to
be collected in a hopper.
4- The cleaner air leaves the cyclone through
the top of the chamber.
48. AIR Quality Control
Cyclone are efficient in removing large particles but are
not sufficient with smaller particles. For this reason, they
are used with other particulate control devices.
Proper disposal for the collected material is needed.
why?
Collected solid particles are most often disposed off in a
landfill.
49. Electrostatic Precipitator (ESP)
Gravity settlers and centrifugal settlers are
devices driving the particles against a solid walls.
For particles below 5 micron , the above devices
are not effective.
ESP is like gravity of centrifugal forces driving the
particles to the wall and effective on much smaller
particles than the previous devices
50. Electrostatic Precipitator (ESP)
The basic idea of ESP is to give the particles
an electrostatic charges and then put them in
electrostatic field that drives them to the
collecting wall.
Two steps charging and collecting process.
Common known electronic air filter.
51.
52. The gasses possesses between the plates
and which are electrically grounded (zero
voltage).
Between the plates are rows of wires held at
a voltage of 40 000 volts.
This combination of the charged wires and
grounded plates produces both the free
electrons to charge the particles and the field
to drive them against the plates.
53. Bag(or fabric) filters
• Used for controlling particulate air pollutants.
• Fabric bags are used to collect the dust, which must be
periodically shaken out of the bags.
• The fabric will remove nearly all particulates, including
submicron sizes.
• Bag filters are widely used in many industrial applications
but are sensitive to high temperatures and humidity.
55. GRAVITATIONAL SETTLING CHAMBERS
Where
dp = diameter/size of the particle, m
µ = viscosity of air, kg/m.s.
Vh = horizontal flow-through velocity, m/s
H = height of settling chamber, m
L = length of settling chamber, m
ρp = density of particle, kg/m3
g = 9.81 m/s2
56. Q1) It is desired to construct a settling chamber to
remove particles from an air stream of 120
m3/min. The temperature of air is 77 °C, and the
specific gravity of the particles is 2. The viscosity
of air is 2.1 X 10-5 kg/m.s. The chamber is to be
strapped to the ceiling of an industrial building,
and the space is limited vertically to 2 m and
horizontally to 1.5 m. Determine the length
required to remove 100 percent of 50-µm
particles.
57. Sol.) Q = 120 m3/min
Vh = 120/2 X 1.5 = 40 m/min = 40/60 = 0.7 m/s.
50 X 10-6 m = (18 X 2.1 X 10-5 X 0.7 X 2/9.81 X L X 2000)1/2
L = 10.6 m
= 11 m
58.
59. dp= (18 X 2.1 X 10-5 X 0.3 X 2/ 9.81 X 8.5 X
2000)1/2
= (0.0002268/166770)1/2
= 3.69 x 10-5 m = 36.9 µm
60. ELECTROSTATIC PRECIPITATOR
Where
A = area of the collector plates, m2
w = drift velocity of the charged particles,
m/s = adp
dp = diameter/size of the particle, m
a = function of charging field, s-1
Q = flow rate of the gas stream, m3/s
ξ = 1 -
)
/
( Q
Aw
e
61.
62. Sol.) (a) 90 percent efficiency ξ = 1 - )
/
( Q
Aw
e
w = 1.5 X 105
X 0.7 X 10-6
= 0.105
0.9 = 1- e-(AX 0.105/5)
e-(AX 0.105/5) = 0.1
-(AX 0.105/5) = ln (0.1)
=-2.3026
A = 2.306 X 5/0.105
= 110 m2
64. Stack gas flows through an electrostatic
precipitator at a rate of 12 m3/s. The total
collection plate area is 250 m2 and the drift
velocity for the system has been determined to
be w = 2.8 X 105 dp
Draw a size-efficiency curve for particles
ranging in size from 0.1 to 10 µm.
71. Definition
Noise is defined as unwanted signal.
To be more specific, noise is referring to unwanted
sound.
Human is tolerable to certain level of noise but will
react to a very loud noise
• Public reaction
<40 dB – no reaction
45 dB – isolated complain
50-55 dB – Widespread complaints
60-65 dB – Public starts to take action
> 70 dB – Action by public
72. Classification of Sound
• Continuous
-An uninterrupted sound level that varies less than 5 dB
during
the period of observation.
-Example: Noise from household fan
• Intermittent
-A continuous sound that last for more than one second
but then
interrupted for more than one second.
- Example: A dentist’s drilling
• Impulsive/Impact
-A sound which last for less than one second.
-Example: Noise from firing a weapon
73. Effect of Noise
• Reduction of quality of life; i.e. interfere
speech, conversation and sleep.
• Physiological effects, i.e. hearing effects.
• Psychological effects, i.e learning effect,
mental health
74. EFFECT OF NOISE ON HUMAN HEALTH
Damage to the human ear can occur in several ways.
First, very loud impulse noise can burst the ear drum,
causing mostly temporary loss of hearing, although
frequently torn eardrums heal poorly and can result in
permanent damage.
The bones in the middle ear are not usually damaged by
loud sounds, although they can be hurt by infections.
Finally, the most important and most permanent damage
can occur to the hair cells in the inner ear.
75. EFFECT OF NOISE ON HUMAN HEALTH
Very loud sounds will stun these hair cells and cause
them to cease functioning.
Most of the time this is a temporary condition, and time
will heal the damage.
Unfortunately, if the insult to the inner ear is prolonged,
the damage can be permanent.
This damage cannot be repaired by an operation or
corrected by hearing aids.
Noise that deprives a person of sleep carries with it an
additional array of health problems.
76. Source of Noise
Noise can be emitted from:
• A point source – electric fan
• A line source – moving train
77. Source of Noise
Noise pollution comes from:
• Traffic
• Industrial equipment
• Construction activities
• Sporting & crowding activities
• Low-flying aircraft.
78. Noise Control
The level of noise can be reduce by using one
of three strategies
1- Protect the recipient
2- Reduce Source Noise
3- Control Path of Noise
79. Noise Control
1- Protect the recipient
Using ear plugs for ear protection is not
effective for most of noise types.
Thus , better to protect the entire ear and
protect the ear plugs wearer from the most
noise
80. Noise Control
2- Reduce Source Noise
The most effective means of noise control is
source reduction.
Re-design of commercial airplanes has
already been mention as an example of noise
source reduction.
81. Noise Control
Reduction can be achieved via re-designing
vehicles and pavements.
Increasing the use of alternative
transportation
Reducing vehicle speed and encouraging to
use alternative routes, through speed control
devices or road designs
82. Sound Power
• Sound power (W): the rate at which energy is
transmitted by sound wave.
• Sound Intensity (I): Average sound power per
unit area normal to propagation of a sound.
W = ∫A I dA ….. (1)
83. Sound Power
• In an environment, in which there are no
reflecting surface, the r.m.s. sound pressure,
Prms at any point is related to I by following
equation:
I = P2
rms / ρc ….. (2)
P = root mean-square (rms) pressure, N/m2
ρ = density of wave medium, kg/m3
c = speed of wave, m/s.
84. The Decibel
Human ear able hear enormous range of sound
pressure. (20 μPa to 1013 for normal people).
Therefore, sound pressure of linear scale is an
inconvenient quantity to use.
This also applied to sound power and sound
intensity.
85. Sound Pressure Level, Lp
Sound pressure level, Lp is defined as
Lp = log10 (P2
rms/ P2
ref) Unit : Bel …..(3)
Or,
Lp = 10 log10 (P2
rms/ P2
ref) Unit : (dB) …..(4)
Pref = 20 μPa.
The factor 10 is introduced in above equation as to avoid a
scale that is to compressed.
86. Adding Sound Pressure Levels
• Given four machines producing 100 dB,
91dB, 90 dB, and 89 dB respectively, what
is the total sound pressure level?
87. Sound Power Level, Lw
Sound power level, Lw is defined as:
Lw = 10 log10 (W/ Wref) Unit : (dB) …..(5)
where;
Wref = 10-12 Watt
92. Example 3-1
The sound pressure inside a diesel lorry is
2 Pa. What is corresponding SPL in dB?
93. • SPL (dB) = 10 X log 10(22/(20 x 10-6)2
= 10 X 10 = 100
94. Example 3-2
Do your self
If a sound source has a pressure of 1500
Pa, compute:
a) The SPL in dB
b) The sound intensity in Watt/m2
Given;
ρ = 1.185 kg/m3 , c = 340 m/s
95. Example 3-3
What is the increase in dB that corresponds
to a five time increase of sound pressure?
96.
97. Daily noise dose, D
• Daily noise dose means a unit of measurement of sound
level indicated by a sound level meter, when used for A
weighted sound level at slow response
D = C1/T1 + C2/T2 + …..+ Cn/Tn
Where,
C1,C2,Cn = actual duration of exposure for an employee
at the various noise levels (unit time)
T1,T2,Tn = Respective duration allowed limits obtained
from First Schedule (unit time)
• D = no units
• The standard value of D is not to exceed 1. if D is greater
than 1, the workers are not working in safe environment
and control measures are necessary.
IMPACT OF NOISE & LEGISLATION
100. Example
A worker is working for 1 hour in a noisy environment
of 90 dB(A) followed by a 2 hours in 92 dB(A) and 3
hours in 94 dB(A). The next 2 hours he works in a
quiet control room. Does the worker comply with the
Factories and Machinery (Noise Exposure)
Regulations 1989,
IMPACT OF NOISE & LEGISLATION
101. D = c1/t1+c2/t2+c3/t3
= 1/8 + 2/6.066 + 3/4.6
= 0.125 + 0.329 + 0.652
= 1.106
D is greater than 1, the workers are not
working in safe environment and control
measures are necessary.
102. Do Your Self
Question
A worker is being exposed to the following noise levels
- 100 dB(A) for 30 minutes
- 85 dB(A) for 6 hour
- 89 dB(A) for 1 hour
Does the worker work in a safe noise level?
IMPACT OF NOISE & LEGISLATION
103. 3.5 Legislation
• Legislation on noise differ from one country to the other
• The basic principle remain the same – to control the noise
emission – to safe guide our hearings from being damaged – to
have a safe working environment
• 2 main legislation
- legislation for ambient air
- legislation for safe working environment
• Ambient air
– Environmental Quality (Motor Vehicle Noise) Regulations
1987 under Environmental Quality act 1974
– Guidelines on the Noise Quality for Ambient Air
• Working environment
– Factories and Machinery (Noise Exposure) Regulations
1989
IMPACT OF NOISE & LEGISLATION
104. Factories and Machinery (Noise Exposure) regulations
1989
• Part I – Preliminary
• Part II – Permissible Exposure Limit
• Part III – Exposure Monitoring
• Part IV – Methods of Compliance
• Part V – Hearing Protection devices
• Part VI – Audiometric Testing Programme
• Part VII – Employee Information and Training
• Part VIII – Warning Signs
• Part IX – Record Keeping
• Part X - Miscellaneous
IMPACT OF NOISE & LEGISLATION
