ASSIGNM ENT

ON

PROBLEM OF ODOR POLLUTIO N

AND ITS MANAGEM EN T SOLUTIO N

Submitted to:

Dr. N.A. Siddiqui

Professor & Head -Health, Safety, Fire & Environment Engineering Department

SUBMITTED BY-:

CHINTAN GUPTA - 500042035

RENJITH PAROLIA - 500043311

RICHA ARORA – 500043338

ROHIT BISHT – 500043049

TABLE OF CONTENTS

1. ODOUR POLLUTION AND ITS CONTROL 3

2. EFFECTS OF ODOUR 3

3. ODOUROUS COMPOUNDS 4

4. SOURCES OF ODOROUS COMPOUNDS 4

5. MEASUREMENT AND CONTROL TECHNIQUES OF ODOUR 5

5.1. MEASURING CONCENTRATION 5 5.2. INTENSITY 6 5.3. HEDONIC TONE ASSESSMENT 7 5.4. CHARACTER 7 5.5. INTERPRETING DISPERSION MODELING 7 5.6. SAMPLING FROM AREA SOURCES 7 5.7. DIRECT SAMPLING 7 5.8. INDIRECT SAMPLING 8

6. ODOUR CONTROL TECHNOLOGIES 8

6.1. ODOUR CONTROL FROM AREA SOURCES 8 6.2. ODOUR CONTROL FROM POINT SOURCES 9

7. INTERNATIONAL STANDARDS, LEGISLATIONS AND REGULATIONS W.R.T.

ODOUR 10

8. RECOMMENDATION 11

9. BIBLIOGRAPHY 11

1. ODOUR POLLUTION AND ITS CONTROL

The term odour refers to perception regarding smell or scientifically it can be called as “a sensation resulting from the reception of stimulus by the olfactory sensory system”. It can be

unpleasant or pleasant but it is caused by inhaling air borne inorganics or organics. The ever growing population, urbanization and industrialisation has led to odour problem which has increased in to a large proportion and thus a need to control the problem has risen.

The major reason of odour problem is no proper sanitation facilities for urbanization. Industrialisation is taking place at a very fast pace and it has added to the problem.

Undesirable odour detoriates the air quality and affects the human lifestyle. Odour problem is one the most complex form of pollution. Odour Pollution has entirely different characteristics but can be compared to noise pollution.

Nuisance is the primary effect of odour on people similarly like noise pollution. The features are:

1) Odour moves downwind 2) People can smell at a distance. 3) In presence of strong odour, weak odour cannot be perceived.

4) Two or more odours neutrals the smell of each other. 5) Odour is liked and disliked is based on the scent with pleasant or unpleasant

experience 6) Substances made of similar or dissimilar chemical contribution may have same odour. 7) Strength and nature of odour may change on dilution.

8) Most animals have keener sense of olfaction as compared to humans. 9) When same strength of odour is combined it may produce a combination that on eor

both may not be unrecognizable. 10) An individual quickly loose it awareness of sensation when constant intensity of

odour is perceived.

2. EFFECTS OF ODOUR

Odour affects living beings and humans in numerous ways. When the Smell is strong,

unpleasant or offensive it ruins a person’s enjoyment of life more when the smell is frequent or persistent. There are many factors related to perceive nuisance are:

1) Odour occurrence frequency

2) Duration of exposure to odour 3) Offensiveness

4) Expectation and tolerance of the receptor Toxic stimulants of odour can cause respiratory symptoms or ill health but foul smell may not cause not direct damage to the body. The secondary effects of odour are insomnia, nausea

and discomfort. The odour with strong smell can cause nasal irritation, breathing problem or asthma. Offensive odour has made environment odorous and loss of property value near

odour causing industries and plants.

3. ODOUROUS COMPOUNDS

Odorous compounds include organic or inorganic molecules. The two major inorganic odours are hydrogen sulphide and ammonia. Organic odours are usually the result of biological

activity that decomposes organic matter and forms a variety of extremely malodorous gases including indoles, skatoles, mercaptans, and amines.

Hydrogen sulphide: Hydrogen sulphide is the chemical compound with the formula H2S It is a colourless gas with the characteristic foul odour of rotten eggs.

Ammonia: Ammonia or azane is a compound of nitrogen and hydrogen with the formula NH3. The simplest pnictogen hydride, ammonia is a colourless gas with a

characteristic pungent smell.

Indole: Indole is an aromatic heterocyclic organic compound with formula C8H7N. It

occurs naturally in human feces and has an intense fecal odour. At very low concentrations, however, it has a flowery smell.

Skatoles: Skatole or 3-methylindole is a mildly toxic white, crystalline organic

compound belonging to the indole family. It occurs naturally in feces (it is produced from tryptophan in the mammalian digestive tract) and coal tar and has a strong

fecal odour.

Mercaptons: mercapton is an organosulfur compound with the chemical

formula CH3SH. It is a colourless gas with a distinctive putrid smell.

4. SOURCES OF ODOROUS COMPOUNDS

The major sources for odorous compounds include agricultural waste, food processing

industries, composting of municipal solid wastes, livestock production industries, semiconductor industries, and the incomplete combustion of hydrocarbon fuels in a range of

industries. The use of ethanol in industries also results in the release of odorous carbonyl compounds into the atmosphere. Odour sources can be classified as follows.

Sources of Odours are:

Point Sources: Point sources are confined emissions from vents, stacks and exhausts.

Area Sources: Area sources may be unconfined like sewage treatment plant, waste water treatment plant, solid waste landfill, composting, household manure spreading,

settling lagoons etc.

Building Sources: Building sources of odour like pig sheds and hog confinement

chicken.

Fugitive Sources: In this source of odour, emissions are of fugitive nature like odour

emissions from soil bed or bio-filter surface.

5. MEASUREMENT AND CONTROL TECHNIQUES OF ODOUR

Odor measurement is essential for odor regulation and control.[19] An odor emission often

consists of a complex mixture of many odorous compounds. Analytical monitoring of

individual chemical compounds present in such odor is usually not practical. As a result, odor

sensory methods, instead of instrumental methods, are normally used to measure such odor.

Odor sensory methods are available to monitor odor both from source emissions and in the

ambient air. These two diverse circumstances require different approaches for measuring odor.

The collection of odor samples is more easily accomplished for a source emission than for an

odor in the ambient air.

Field measurement with portable olfactometer seems more effective, but the use of field

olfactometer is not regulated in Europe so far, while it is popular in the U.S. and Canada, where

several States set limits at the receptor sites or along the perimeter of odor emitting plants,

expressed in units of dilution to threshold (D/T)

Different aspects of odor can be measured through a number of quantitative methods, such as

assessing concentration or apparent intensity. Initial entry into a room provides the most

accurate sensing of smell, before habituation begins to change perception of odor.

Sensation of odor has 4 properties related to threshold and tolerance: odor concentration, odor

intensity, odor quality, and hedonic tone.

5.1. MEASURING CONCENTRATION

Odor concentration is an odor's pervasiveness. To measure odor sensation, an odor is diluted

to certain amounts to reach a detection or recognition threshold. The detection threshold is the

concentration of an odor in air when 50% of a population can distinguish between the odorous

sample and an odor free blank. The recognition threshold is the concentration of an odor in air

in which 50% of a population can discern from an odorous sample and odor free blank.The

recognition odor threshold is usually a factor of 2 to 5 times higher than the detection threshold

The measurement of odor concentration is the most widespread method to quantify odors. It is

standardized in CEN EN 13725:2003. The method is based on dilution of an odor sample to

the odor threshold (the point at which the odor is only just detectable to 50% of the test panel).

The numerical value of the odor concentration is equal to the dilution factor that is necessary

to reach the odor threshold. Its unit is the European Odour Unit, OUE. Therefore, the odor

concentration at the odor threshold is 1 OUE by definition.

To establish the odor concentration, an olfactometer is used which employs a group of

panelists. A diluted odorous mixture and an odor-free gas (as a reference) are presented from

sniffing ports to a group of panelists. In comparing the odor emitted from each port, the

panelists are asked to report if they can detect a difference between the ports. The gas-dilut ing

ratio is then decreased by a factor of 1.4 or two (i.e., the concentration is increased accordingly).

The panelists are asked to repeat their judgment. This continues until the panelists respond

certain and correct twice in a row. These responses are used to calculate the concentratio n of

the odor in terms of European odor units (OUE/m3).

The test persons must fulfill certain requirements, for example regarding their sensitivity of

odor perception. The main panel calibration gas to verify this requirement used is n-Butanol (as

1 OUE/m3≡40 ppb/v n-butanol).

To collect an odor sample, the samples must be collected using specialized sample bags, which

are made from an odor free material e.g. Teflon. The most accepted technique for collecting

odor samples is the lung technique, where the sample bag is placed in a sealed drum, and a

vacuum is placed on the drum, which fills the sample bag as the bag expands, and draws the

sample from the source into the bag. Critically, all components which touch the odor sample,

must be odor free, which includes sample lines and fittings.

A human's odor detection threshold is variable. Repeated exposure to an odorant leads to

enhanced olfactory sensitivity and decreased detection thresholds for a number of different

odorants. It was found in a study that humans that were completely unable to detect the odor of

androstenone developed the ability to detect it after repeated exposure.

Humans can discriminate between two odorants that differ in concentration by as little as 7%.

There are a number of issues which have to be overcome with sampling, these include: – If the

source is under vacuum – if the source is at a high temperature – If the source has high humid ity

Issues such as temperature and humidity are best overcome using either pre-dilution or dynamic

dilution techniques.

5.2. INTENSITY

Odor intensity is the perceived strength of odor sensation. This intensity property is used to

locate the source of odors and perhaps most directly related to odor nuisance.

Perceived strength of the odor sensation is measured in conjunction with odor concentration.

This can be modeled by the Weber-Fechner law: I = a × log(c) + b

I is the perceived psychological intensity at the dilution step on the butanol scale, a is the

Weber-Fechner coefficient, C is the chemical concentrations, and b is the intercept constant

(0.5 by definition)

Odor intensity can be expressed using an odor intensity scale, which is a verbal description of

an odor sensation to which a numerical value is assigned

Odor intensity can be divided into the following categories according to intensity:

0 – no odor

1 – very weak (odor threshold)

2 – weak

3 – distinct

4 – strong

5 – very strong

6 – intolerable

This method is applied by in the laboratory and is done so by a series of suitably trained

panelists/observers who have been trained to appropriately define intensity.

5.3. HEDONIC TONE ASSESSMENT

Hedonic assessment is the process of scaling odors on a scale ranging from

extremely unpleasant via neutral up to extremely pleasant. It is important to note that intens ity

and hedonic tone, whilst similar, refer to different things. That is, the strength of the odor

(intensity) and the pleasantness of an odor (hedonic tone). Moreover, it is important to note

that perception of an odor may change from pleasant to unpleasant with increasing

concentration, intensity, time, frequency, and previous experience with a specific odor; all

factors determining a response

The overall sets of qualities are sometimes identified as the "FIDOL factors", (short

for Frequency, Intensity, Duration, Offensiveness and Location).

5.4. CHARACTER

The character of an odor is a critical element in assessing an odor. This property is the ability

to distinguish different odors and is only descriptive. First a basic description is used such as

sweet, pungent, acrid, fragrant, warm, dry, or sour. The odor is then referenced to a source such

as sewage or apple which can then be followed by a reference to a specific chemical such as

acids or gasoline

Most commonly, a set of standard descriptors is used, which may range from fragrant to sewer

odor. Although the method is fairly simplistic, it is important for the FIDOL factors to be

understood by the person recording the character. This method is most commonly used to

define the character of an odor which can then be compared to other odors. It is common for

olfactometry laboratories to report character as an additional factor post sample analysis.

5.5. INTERPRETING DISPERSION MODELING

In many countries odor modeling is used to determine the extent of an impact from an odor

source. These are a function of modeled concentration, averaging time (over what time period

the model steps are run over (typically hourly) and a percentile. Percentiles refer to a statistica l

representation of how many hours per year, the concentration C may be exceeded based on the

averaging period.

5.6. SAMPLING FROM AREA SOURCES

There are two main odor sampling techniques, the direct odor sampling and the indirect odor

sampling technique. Indirect refers to collecting samples from the air stream which has already

passed over the emitting surface.

5.7. DIRECT SAMPLING

Direct refers to the placement of an enclosure on or over an emitting surface from which

samples are collected, and an odor emission rate is determined.

The most commonly used direct methods include the flux chamber and wind tunnels which

include the UNSW wind tunnel. There are many other available techniques, and consideration

should be given to a number of factors before selecting a suitable method.

A source which has implications for this method are sources such as bark bed biofilters, which

have a vertical velocity component. For such sources, consideration needs to be given as to the

most appropriate method. A commonly used technique is to measure the odor concentration at

the emitting surface, and combine this with the volumetric flow rate of air entering the biofilter

to produce an emission rate.

5.8. INDIRECT SAMPLING

Indirect sampling is often referred to as back calculation. It involves the use of a mathematica l

formula to predict an emission rate.

Many methods are used, but all make use of the same inputs which include surface roughness,

upwind and downwind concentrations, stability class (or other similar factor), wind speed, and

wind direction.

6. ODOUR CONTROL TECHNOLOGIES

Odour control depends on type of sources and is discussed below:

6.1. ODOUR CONTROL FROM AREA SOURCES

For large area sources following methods can be used to reduce odour complaints.

i) Excluding development close to the site

Development close to the site is to be excluded. A reasonable “buffer zone” around the area

sources has to be determined. The actual size of the zone depends upon a number of factors,

including the size of the area from which odour emanates, the intensity of the odour being

emitted, the duration and frequency of the odour emissions, the actual process being

undertaken, the topography of the site, the weather conditions that prevails at the site. Green

belt development in the buffer zone may help at least partially to mitigate / obfuscate the odour.

ii) Ensuring that the operation is carried out under the best management practices

Best management practices (BMP) vary depending upon the industry producing the odour. For

all new developments, BMPs starts with the site selection and the building of the facilities.

iii) Nozzles, sprayers and atomizers that spray ultra-fine particles of water or chemica ls

can be used along the boundary lines of area sources to suppress odours.

Rotary atomizer is one such technique widely recommended for effective control of odour in

case of area sources. The Atomizer uses centrifugal action by a spinning inner mesh to force

droplets on to an outer mesh which "cuts" the water into atoms. The rotary atomizer produces

millions of microscopic droplets of water -- up to 238 billion from single little droplets that are

thinner than a human hair and a fine spray which covers up to 30 metres. This creates a fine

mist, which is more effective with minimal use of water and electricity. There are a large

number of chemicals and proprietary products that claim to reduce odour when they are applied

to area sources. Atmospheric odour that is contained in a restricted area can be oxidized by

atomization of the chlorine dioxide. Odour from sources such as holding ponds, lagoons, and

sewage pre or post treatment effluent can be controlled by atomized spray of chlorine dioxide.

To reduce odour, chemicals have to be applied over very large area, the cost of materials and

labour would be very high. The large quantity of these compounds required could cause

pollution. The spray / atomizer techniques are used to conceal / mask odour also from building

and fugitive sources.

6.2. ODOUR CONTROL FROM POINT SOURCES

In case of point sources such as that of industries, the odour-causing gas stream can be

collected through piping and ventilation system and made available for treatment. Dispersion

method is the simplest of the methods that can be adopted for odour abatement. This is nothing

but to release odorous gases from tall stack. It results in normal dispersion in the atmosphere

and consequent decrease in ground-level concentration below the threshold value. Dispersal by

stacks requires careful consideration of the location & meteorological parameters, etc. In

general, dispersion of odour emissions via chimneys is not a recommended method. An array

of treatment technologies is available for control of odour from gas streams collected through

process ventilation systems. These include :

i) Mist filtration

ii) Thermal oxidation/ Incineration

iii) Catalytic oxidation

iv) Biofiltration

v) Adsorption

vi) Wet scrubbing/Absorption

vii) Chemical treatment

viii) Irradiation

ix) Masking

x) Condensation

xi) Green belt development

The choice of the technology is often influenced by the following factors:

• The volume of gas (or vapor) being produced and its flow rate

• The chemical composition of the mixture causing the odour

• The temperature

• The water content of the stream

7. INTERNATIONAL STANDARDS, LEGISLATIONS AND REGULATIONS W.R.T. ODOUR

Many Countries have adopted measurements for controlling odour pollution, some of which is given below:

Canada Here the responsibility lies with the provinces. Different provinces have their own odour

policy. Since 1976 Ontario has a regulations called Agriculture Code of Practice that quotes the distance to be kept with the livestock facilities.

In Alberta, there are guidelines for air quality as H2S of 10 ppb/v on an hour average is taken for the purpose of Odour Impact mangemnet. This leads to 20/ou m3 on the basis of the smell

of H2S only, with the threshold limit of 0.5ppb/v. Denmark

Here the ground level concentration is to not exceed 5 – 10 ou m3, it depends upon the location whether its redential or non- residential at 99%, with the average time of 1 min

New Zealand. Here the Ministry of Environement, suggest that the air quality should be of 5 – 10 ou m3 at

99.5% to 99.9 % Japan

Japanese Offensive Odour control law represents the odour intensity in terms of Odour Index, that is: Odour Index = 10 Log (Odour Unit)

Intensity value from 2.5 – 3.5 is acceptable. The intensity scale used is given below:

0 – Not Percentile

1 – Detectable Smell (faint)

2 – Recognition ( Weakly quality perceptible)

3 – Easily Quality perceptible

4 – strong

5 – Very strong

Germany

VDI3940 Method is applied by Germany, It is also called Determination of Odorants in Ambient Air by Field Inspections.

< 10 percent of odour hours of residential areas

<15 percent of odour hours of non – residential areas

United Kingdom

They Implement the Environment Protection Act which covers IPC (Integrated pollution and control) and LAAPC (Local authority pollution control). IPC policy covers the control for

the complex polluting processes with emission to water, land and air while LAAPC covers the control for small process with emission restraining to air only.

8. RECOMMENDATION

I. There is requirement for data based information on the magnitude of odorous chemicals or gases at the ambient environment as well as at point source

II. The report provided by the expert committee should be followed as guidelines for

odour control. III. Management practices or Pilot practices should be done to control odour pollution and

should be sector wise. Additionally, such practices should be financially assisted if required.

IV. Green belts should be adopted to control the odour pollution created near waste

disposal sites and industrial processing areas. The green belts should be equipped with suitable species of trees and plants and other physical methods can also be adopted if

required. V. The Human Resource working in this sector should be exposed to international Odour

pollution control and should provide assistance for the same

VI. According to the source of the odour emission, standards should be formed for example, Pesticides, Chemical, Fertilizer, Drugs & Pharmaceuticals, Waste water

treatment etc. VII. For developing an effective control system on odour pollution, it is vital that the

measurement on odour is done in such a way that it is accurate, acceptable and

precise. VIII. The areas where there is more pollution related to odour should be tackled first with

the technology and knowledge presently held by the country IX. The standards for pollution should be updated from time to time X. Efforts should be exerted to maintain and operate the dump sites, treatment plants, air

pollution control device etc. so as to reach an optimal reduction in odour pollution

9. BIBLIOGRAPHY

www.epd.gov.hk/epd/english/greenproperty/poll_pro/poll_pro_rec.html

www.eolss.net/sample-chapters/c09/e4-11-02-00.pdf

www.sinia.cl/1292/articles-55384_Strategy_Odors_Management_2014_2017.pdf

cpcb.nic.in/upload/NewItems/NewItem_141_package_odourreport_2.12.08.pdf