Environment & Health

7/28/2019 Environment & Health

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ENVIRONMENT & HEALTH

ENVIRONMENT & HEALTH

* We are surrounded by various living & non- living things, that includesmaterials as well as non- materials.

our environment comprises of:

* Physical Environment :


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* Biological Environment

*Social Environment

* Cultural Environment

contd.

i) Physical Environment

This consists ofnon living things like;

water, air, soil, housing, radiation, light, noise, vibration, refuse and other

wastes

ii) Biological Environment :

This consists ofliving things ofanimal & plant origin like; rodents, insects,

microbes ( bacteria, virus, rickettsiae, parasites, fungi )


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iii) Social Environment

consists of occupation, literacy, income, religion, standard of living, life

style, availability of health services.

iv) Cultural Environment

Consists of knowledge, attitude, beliefs, practices, traditions, culture,

customs, habits.

WATER

* Water is essentially required for life by all living organisms including plants.

* Water intended for human consumption should be safe andwhole some i.e.

i) Free from pathogens and

ii) harmful chemicals

iii) Water should be potable (acceptable) i.e.

pleasant to taste,


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clear&

free from any colourand odour.

Contd.

A safe water with unpleasant taste or appearance may derive the consumer to

other less safe sources.

iv) Usable fordomestic purpose.

Water is said to be polluted or contaminated, if it does not

fulfill above criteria.

Water Requirement

Requirement of water depends upon climatic conditions, standard of living and

habits of people.

However, 150 200 Ltr of water per head(per capita) is considered adequate to

meet daily requirement of a urban citizen.

Uses of Water

* Domestic use


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* Drinking

*Cooking

* Washing

* Bathing

* Flushing of Toilets

* Gardening etc

ii) Public purpose

* Cleaning streets

* Recreational

* Swimming pools

* Fountains

* Ornamental ponds

* Fire Fighting

* Public Parks


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Water is essential for economic, social and cultural development of community.

It can eliminate diseases, promote development and improve quality of life.

Sources of water

i. Rain

ii. Surface water

* Impounding Reservoir

* Rivers & Streams

* Tanks, Ponds & Lakes


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iii . Ground Water

* Shallow well

* Deep well

* Artesian well

* Tube well

* Springs

i. Rain wateris purest form of water

However, as rain water passes through the atmosphere, it picks up microbes

(pathogens) and also gases (SO2, CO2,NO2) emitted by power plants and

automobilesusing fossil fuel.

This results in acid rain.

Gibraltardepends upon rains as its source of water supply.

ii. Surface water:

* Rain, when comes to ground becomes surface water .

* Surface water gets contaminated from human and animal activities,therefore,

it is never safe for human consumption unless subjected to protection ,purification & treatment.


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# Impounding reservoirs are artificially constructed lakes to store huge quantity

of water.

The area draining into these reservoir is called Catchment area.

* cities like Mumbai, Chennai, Nagpur derive their water supply from suchreservoirs.

* Purity of water in these reservoirs is good, it is next to rain water.

* However, prolonged storage leads to growth of algae and othermicroscopic organisms, which imparts bad taste & odourto water.

*If surrounding hills are covered with peat, the water may acquire brownishcolouration.

## Rivers

* Cities like Delhi, Allahabad, Kolkata derive water from rivers.

* River water is grossly polluted & unfit for drinking unless subjected totreatment.


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* Rivers have been described as a direct connection between thealimentary canal of people living up steams and the mouth of those

staying down streams.

* Rivers derive impurities from sewage, sullage, Industrial & trade wastes.

iii. Ground water

* Rain water percolates down the earth and forms ground water.

* Ground water is superior to surface water

because strata of soil provides effective filtering media.

* However, mineral contents may behigh and vary from place to place.

This may render the water hard.


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# ARTESIAN WELL

When the water is held under pressure between two imperious layers , and

rises above the ground at its own, it is called Artesian well.

* These are not common in India.

# Tube wells are successful source of water in many parts of India. Chandigarh

draws its water from tube wells.

Quality of water and yield is very high.


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#Springs

Whenground water comes to the surface and

flows freely under natural pressure, it is called spring.

Depending on the source, springs also may be

shallow or deep spring.

WATER POLLUTION

** Water during its course of flow picks up impurities

from the atmosphere, catchment area and the soil.

** In routine these impurities may not be dangerous,

however, more serious pollutions may be added by the human activities;

these include:


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* Sewage

*Industrial & trade wastes

* Agricultural pollutants

* Physical pollutants

Water and Disease

WHO estimates that as much as 80 per cent of all diseases in the world are

associated with water.


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These diseases can be grouped as under:

Sewage pollution

Industrial pollution

Hazards from pipe material

Effects of soil contents

Hardness of water

Diseases due to shortage of water

Other pollutants

fertilizers and pesticides

radioactive substances

.

ii. Industrial pollution


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Numerous known and unknown toxic chemicals are being discharged into water

courses along with many industrial wastes.

Poly Aromatic Hydrocarbons ( PAH) are carcinogenic.

Certain metals like mercury, arsenic, cadmium, cyanide, lead, selenium,

manganese, copper, etc., are harmful and their concentration should not

exceed maximum permissible levels.

.

iv. Effects of soil contents

Fluorides and iodine contents of soil can also affect the health through drinking

water.

Fluorosis, a crippling disease of the skeletal system is due to the excessive

intake of fluorides through water.

It is a public health problem in some areas of the Punjab, Andhra Pradesh and

certain other states.


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Whereas deficiency of fluorides has been associated with high incidence of

dental caries.

Iodine deficiency in may result in Goitre

vi. Diseases due to shortage of water

* Certain diseases result from chronic water shortage. Incidence ofscabies andtrachoma is high under these situations.

These diseases flourish under poor hygienic standards.

* vii. Other pollutants

= fertilizers and pesticides used in the field of agriculture is one such group.

= Much more serious pollution can result from

radioactive substances, (Uranium in Bhatinda belt,

Thorium in Kerala)

which have carcinogenic and genetic effects


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PURIFICATION OF WATER

Purification of water may be carried out:

i. On large scale i.e. for community

ii. On small scale i.e. for domestic purposes

i. Purification of water on large scale

The treatment to be employed depends upon :

- the nature of raw water, and

- standard of water quality desired.

For example ,

Ground water(wells, springs) may not need any treatment

except Disinfection,

where as Surface water(river) which tends to be turbid & polluted

requires extensive treatment.


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* The water purification plant comprises of one or more of the followingcomponents :

i) Storage

ii) Filtration

iii) Disinfection

i) STORAGE

water drawn from the source is stored in naturalorartificialreservoir.

Storage provides natural purification in the form of

Physical,

Chemical, and

Biological contents of water :

(a) Physical: By mere storage, the quality of water improves.

About 90 per cent of the suspended impurities settle down in

24 hours by gravity.


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The water becomes clearer.

This allows penetration of light, and reduces the work load on the filters,

(b) Chemical:

.

The aerobic bacteria oxidizes the organic matter present in the water

with the help of dissolved

oxygen.

As a result, the quantity of free ammonia is reduced ,

and there is rise in nitrates .

(c) Biological:

1. A tremendous drop in bacterial count takes place during storage.

2. The pathogens gradually die out.

# It is found that when river wateris stored, the total bacterial count drops by as

much as 90 per cent in the first 5 -7 days.

This is one of the greatest benefits of storage.


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## The optimum period of storage of river water is considered to

be about 10 14 days.

# If the water is stored for long periods, there islikelihood of development ofvegetable growths such as algae which impart a

bad smell and colourto water.

(ii) FILTRATION

Filtration is the second stage in the purification of water, and quite an important

stage because

98 99 per cent of the bacteria are removed by filtration, apart from other

impurities.

Two types of filters are in use,

- the biological or slow sand filters and - the rapid sand or

mechanical filters.

a) SLOW SAND or BIOLOGICAL FILTERS

Slow sand filters were first used for water treatment in 1804 in

Scotland and subsequently in London.

During the 19th century their use spread throughout the world.

Even today, they are generally accepted as the standard method of

water purification.


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Elements of a slow sand filter

elements of a slow sand filter consists of:

* i. Supernatant (raw) water

* ii. A bed of graded sand

* iii. An under-drainage system; and

* iv. A system of filter control valves

1. Supernatant water

The supernatant water above the sand bed,

whose depth varies from 1 to 1.5 metre,

serves two purposes:

* Firstly,it provides a constant head of water

so as to overcome the resistance of the filter bed and

thereby promote the downward flow of water through the sand bed; and


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**secondly, it provides waiting period of some hours (3 to 12 hours, depending

upon filtration velocity) for the raw water, wherein, it to undergo partial

purification by

sedimentation,

oxidation &

particle agglomeration.

## The level of supernatant water is always kept constant.

2. Sand bed

* # The most important part of the filteris the sand bed.

* The thickness of the sand bed is about 1 metre.

*The sand grains are carefully chosen so that they are preferably

rounded and have an effective diameter between 0.2 and 0.3 mm.

* The sand should be clean and free from clay and organic matter.


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* The sand bed is supported by a layer of graded gravel, 30 40 cm deepwhich also prevents the fine grains being carried into the drainage pipes.

# The sand bed presents a vast surface area; one cubic metre of filter sand

presents some of 15,000 sq. metres of surface area.

*Water percolates through the sand bed very slowly

(a process taking two hours or more), and as it does so,

it is subjected to a number of purification processes :

* i. mechanical straining,

* ii. sedimentation,

* iii. adsorption,

* iv. oxidation and

* v. bacterial action, all playing their part.

# The designed rate of filtration of water normally lies between

0.1 and 0.4 m3 / hour/per square metre of sand bed surface.

Vital layer:


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3. Under drainage system

At the bottom of the filter bed is the under drainage system.

It consists ofporous or perforated pipes,

which serve the dual purpose :dual purpose :

i. providing an outlet for filtered water, andii. supporting the filter medium above.

Once the filter bed has been laid, the under drainage system cannot be seen.

4. Filter control

The filter is equipped with certain valves and devices which are incorporated in

the outlet pipe system.

The purpose of these devices is to maintain a constant rate of filtration.

* An important component of the regulation system is the Venturi meterwhich measures the bed resistanceor


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loss of head.

When the resistance builds up, the operator opens the regulating valve so as to

maintain a steady rate of filtration.

* When the loss of head exceeds 1.3 metre it is uneconomical to run thefilter.

Filter cleaning: Normally the filter may run for weeks or even months without

cleaning.

When the bed resistance increases to such an extent that the regulating valve

has to be kept fully open, it is time to clean the filter bed, since any further

increase in resistance is bound to reduce the filtration rate.

At this stage, the supernatant water is drained off, and the sand bed is cleaned by

scraping off the top portion of the sand layer to a depth of1 to 2 cm.

This operation may be carried out by unskilled labourers using hand tools or by

mechanical equipment.

After several years of operation, and say 20 to 30 scrapings, the thickness of the

sand bed is reduced to about 0.5 to 0.8 metre.

Then the plant is closed down and a new bed is constructed.


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The advantages of a slow sand filterare:

1. simple to construct and operate

2. the cost of construction is cheaper than that of rapid sand filters

3. the physical, chemical and bacteriological quality of filtered water

is very high.

* When working ideally, slow sand filters have shown to

reduce total bacterial count by 99.9 to 99.99 per cent and

E.coli by 99 to 99.9 per cent.

b) RAPID SAND or MECHANICAL FILTERS

In 1885, the first rapid sand filters were installed in the USA.


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Rapid sand filters are oftwo types,

the gravity type (e.g. Patersons filter) and the pressure type

(e.g. Candys filter).

Both the types are in use.

The following steps are involved in the purification of water by rapid sand filters:

1. Coagulation: The raw water is first treated with a chemical coagulant such as

alum, the dose of which varies from 5 40 mg ormore per litre, depending

upon the turbidity, colour, temperature and pH of water.

2. Rapid mixing: The treated water is then subjected to violent agitation in a

mixing chamber for a few minutes. This allows a quick and thorough

dissemination of alum throughout the bulk of the water, which is very necessary.

3. Flocculation: The next phase involves a slow and gentle stirring of the treated

water in a flocculation chamber for about 30 minutes. The mechanical

type of flocculation consists of a number ofpaddles which rotate at 2 to 4 rpm

with the help of motors. This slow and gentle stirring results in the formation of a

thick, copious, white flocculent precipitate ofaluminium hydroxide.

Thicker the precipitate or flock diameter,

greater the settling velocity.

4. Sedimentation: The coagulated water is now led into sedimentation tanks

where it is detained for periods varying from

2 6 hours when the flocculent precipitate together with impurities and bacteria

settle down in the tank.


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*The whole process of washing takes about 15 minutes.

* In some rapid sand filters, compressed airis used

as part of the back washing processes.

Advantages

The advantages of a rapid sand filterover the slow sand filter are:

1. rapid sand filter can deal with raw water directly.

2. No preliminary storage is needed

3. the filter beds occupy less space

4. Filtration is rapid, 40 50 times that of a slow sand filter

5. the washing of filter is easy

6. there is more flexibility in operation


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Comparison between Rapid and Slow sand filters

(III) DISINFECTION

In water works ,

the term disinfection is synonymous with chlorination.

# CHLORINATION

Chlorination is one of the greatest advances in water purification.

* It is supplement,

not a substitute to sand filtration.

Mechanism of Action of chlorine:


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* When chlorine is added to water,

there is formation ofhydrochloric acid and

hypochlorous acids.

*The HCl is neutralizedby the alkalinity of the water.

*The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions,

as follows: -

H2O + Cl2 = HCl + HOCl

HOCl = H + OCl

*The disinfecting action of chlorine is

mainly due to the hypochlorous acid, and

to a small extent due to the hypochlorite ions. *

The hypochlorous acid is more effective (70 80 times) than the hypochlorite

ion.


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Principles of chlorination:

The mere addition of chlorine to water is not chlorination.

There are certain rules which should be followed to ensure proper chlorination:

1, Firstly, the water

should be clear and freefrom turbidity.

Turbidity impedes efficient chlorination

cond

3. Thirdly the contact period. The presence of free residual chlorine for a contact

period of at least one houris essential to kill bacteria and viruses.


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It should be noted however, that chlorine has no effect on spores, protozoal cysts

and helminthic ova, except in higher doses.

4. the minimum recommended concentration offree chlorine is 0.5 mg / Ltr after

one hour.

The free residual chlorine provides a margin of safety against subsequent

microbial contamination as may occur during storage and distribution.

5. The correct dose of chlorine is the sum of the chlorine demand of the specific

waterplus the free residual chlorine of 0.5 mg / Ltr .

METHOD OF CHLORINATION

For disinfecting large bodies of water, chlorine is applied either as

1. chlorine gas or

2. chloramines or

3 Perchloron

1. Chlorine gas is the first choice, because I

it is cheap,

quick in action, efficient and easyto apply.


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Since chlorine gas is an irritant to the eyes and is poisonous, a special equipment

known as chlorinating equipment is required to apply chlorine gas to water

supplies. Patersons chloronome is one such device for measuring, regulating

and administering gaseous chlorine to water supplies.

BREAK POINT CHLORINATION

Breakpoint chlorination is the point at which the chlorine demand is met.

If chlorine is added beyond the break point, it remains in the free state as free

chlorine (or free residual chlorine; FRC).

STEPS

1.As the chlorine is added itcombines with ammonia

to form chloramines.

This is Combined Residual Chlorine ( CRC )

This is also bactericidal.

The peaking coincides with the oxidation ofall organic matters.

2. Addition of further chlorine,oxidizes ammoniacal compounds.

3. Addition of next increments ofchlorine

results in destruction of chloramine,

resulting in the release of Free Residual Chlorine.

( FRC )


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Contact period:

* it is the period (time) required for the chlorine to disinfect the water.

* For optimum disinfection, the presence of free chlorine for a contact period ofone houris essential.

* The free chlorine that remains at the end of one hour is called Freeresidual chlorine (i.e. after breakpoint chlorination).

* The minimum concentration of free residual chlorine for drinking purposes (indrinking water) should be 0.5 mg per litre. (i.e. 0.5 ppm = part per million of

water)

(1 mg of chlorine in 1 litre of water provides 1 ppm concentration of chlorine).

* The purpose of providing free residual chlorine in the drinking water is toprovide a margin of safety against further contamination of water which is

likely to occur during storage and distribution.


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* Super chlorination:

This is a process of chlorination, wherein double the usual dose of chlorine is

added to water, so as to get FRC of more than 2 ppm at the end of contact

period.

This is resorted to when the water is heavily contaminated or when there is

threatening outbreak of water borne epidemic.

But the disadvantage is that such super chlorinated water has the smell of chlorine

and it irritates nose, throat and eyes. Therefore, super chlorination is followed

by de chlorination.

* De chlorination: This is removal of excess of chlorine and is carried out by

addition ofreducing substances such as sulphur dioxide, sodium sulphite,

sodium bisulfphite, sodium thiosulphate or activated carbon. FRC is

reduced to less than 2 ppm.

For effective chlorination ,

the pH of the water should be maintained between 7.2 and 7.6. Under no

circumstances it should be allowed to fall below 7 or

to exceed 8.


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when the pH is less than 7,

sodium carbonate is added and

when it is higher than 8,

Hydrochloric acid is added.

In either case only small quantities are added periodically at hourly intervals until the

correct pH is obtained.

ORTHOTOLUIDINE (OT) TEST

* Orthotoluidine test detects both

free and combined chlorine in water. The test was

developed in 1918. the reagent consists of analytical grade O toluidine,

dissolved in 10 per cent solution of hydrochloric acid.

* The apparatus used is called Chloroscope.

* When the reagent is added to water containing chlorine,

it turns yellow and the intensity of the colourvaries with the concentration of

chlorine.

* The reagent reacts with free chlorine within 10-15 seconds ,


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* while combined chlorine reacts slowly and yellow colour appears and deepens in

15 to 20 minutes.

The test is carried out by adding 0.1 ml of the reagent to 1 ml of water.

The yellow colour produced is matched against suitable standards or colour discs.

Commercial equipment ( Chloroscope ) is available for this purpose. It is

essential to take the reading within 10 seconds after the addition of the reagent

to estimate free chlorine in water. The colour that is produced after a lapse, say

15 20 minutes, is due to the action of both free and combined chlorine

.ORTHOTOLIDINE-ARSENITE (OTA) TEST

# This is a modification of the OT test

to determine free and combined chlorine separately.

## Further, the errors caused by the presence of interfering substances such

as nitrites,

iron and

manganese all of them produce yellow colourwith o

tolidine, are overcome by the OTA test.


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# Chlorine continues to be the most commonly used sterilizing agent because of its

germicidal properties and the comparatively low cost and ease of application, its

pre-eminence in water disinfection is being seriously challenged because of the

discovery that chlorination of water can lead to the formation of many

halogenated compounds, some of them are either knownorsuspected carcinogens.

a) OZONATION:

Theprocess involves, passing ozonized air through the water.

* Ozone is a relatively unstable gas.

* It is a powerful oxidizing agent.

* It destroys the pathogens including viruses and

also destroys the phenolic compounds which produces

undesirable odour, taste and colour, and

* removes the entire chlorine from the water.

Most importantly, ozone has a strong virucidal effect.

It inactivates viruses in a matter of seconds , whereas minutes are required

to inactivate them with either chlorine or iodine.

This has prompted many municipalities to consider ozone for potable water

treatment.

More than 1000 municipal water treatment plants around the world are using

ozone, the oldest of these is in France, which has been in operation since

1906.


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# Drawback of ozone is that it has no residual germicidal effect.

# The current thinking is that ozone should be used as a pre treatment of

water to destroy viruses and bacteria, and also organic compounds that

are precursors for undesirable chloro organic compounds that are formed

when chlorine is added.

# A carefully controlled minimum dose of chlorine is added to the water before

water is pumped into the distribution system.

# Thus ozone is usually employed in combination with chlorine.

# In this combined treatment, the two methods complement each other taking

advantage of the best features of each.

# The ozone dosage required for potable water treatment varies from 0.2 to 1.5

mg per litre.

(b) ULTRAVIOLET IRRADIATION:

# Germicidal property of UV rays have been recognized for many years.


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UV irradiation is effective against most microorganism known to contaminate

water supplies including viruses.

# The method of disinfection involves the exposure to a

film of water, up to about 120 mm thick,

to one or several quartz mercury vapour arc lamps emitting ultraviolet

radiation at a wavelength in the range of 200 to 295 nm applications are

limited to individual or institutional systems.

# For efficient disinfection water should be free from turbidity and

suspended or

colloidal constituents.

## The advantages are that the exposure is forshort period,

* no foreign matter introduced,

* no taste and

* no odour produced.


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Overexposure does not result in any harmful effects.

## The disadvantages are that no residual effect is available and there is a lack of

a period field test for assessing the treatment efficiency;

moreover, the apparatus needed is expensive.

Purification of Water on Small Scale

* Household purification of water

** Disinfection of wells

A. Household Purification of Water

Household purification of water is by three methods Physical, Chemical and

Mechanical.

* Physical methods: These are Boiling,

ozonation and

ultraviolet irradiation.


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* Chemical methods: The different chemical substances employed

for purification of water for domestic use are Chlorine,

Iodine and

potassium permanganate.

* Mechanical methods:

This consists of using the ceramic filters, such as

Pasteur Chamberland filter,

Berkefeld filter,

Katadyn filter,

carbon and pad filter,

aqua guard and

reverse osmosis treatment.

The essential part of the first three filters, is called Candle, or Tube, which ismade up ofporcelain in the

P C filter and ofkieselgurh or infusorial earth in the Berkefeld filter and a coat of

silver catalyst on the candle in Katadyn filter.

AQUA GUARD domestic filter

This purifies the water in three stages:

i. It filters physical impurities

(i.e. traps the dirt, mud and such other turbid impurities.)

ii. It removes the organic impurities

(thereby remove the colourand odour)

iii. Itinactivates the pathogens by U V treatment in the U V chamber.


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## It has the in built electronic monitoring system whereby it monitors the

quality of purified waterand stops the flow ,

if the purification level falls below the predetermined levels.

* Reverse Osmosis treatment:

* Invention of this technique is a milestone in creation of drinking waterresource.

* Reverse osmosis is based on water reverse theory in nature.

* NASA in US first applied this theory in purifying the astronaut's urine as aresource for drinking water in space.


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* In this process, water is purified in 5 stages as follows.

Stage 1: 5 u sediment filter.

This removessand, silt, dust and rust particles

(i.e. removes suspended impurities)

Stage 2: Activated carbon block filter

Removeschlorine, organic matter, and bleaches colour

(Removeschemical impurities).

Stage 3: GAC filter (Granular Activated Carbon)

Removesharmfulchemicals and

color, taste and odour producing substances

Disinfection of Wells

Wells constitute the main source of water supply in rural areas. Since most of the

wells are shallow wells, liable for contamination, need to be disinfected

periodically, more so during epidemics of acute gastro enteritis, cholera, etc.

Wells are best disinfected by bleaching powder.


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The various steps of disinfection of wells are

* Finding the volume of water in the well

* Estimating the quantity of bleaching powder required

* Preparation of the chlorine solution

* Delivery of the chlorine solution

* Contact period

* Orthotoludine test

a. Finding the volume of water:.

* If it is rectangular well. The formula is I X b X h X 1000 = X litres

* if it is circular well, by using the formula

3.14 X d2 X h

4

The volume is expressed in cu. Metres. I cu metre 1000 litres.


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Volume of water in cubic metres X 1000

= X litres

* Which is derived from

r2 h, where = 22 / 7 = 3.14

r= radius of well in mtrs.

= half of diametre

= d / 2

r2

= d/2 X d/2 = d2

/ 4

h= height of water column in metres.

Where I = length of well in mtrs.

b= breadth of well in mtrs.

h= height of water column in mtrs.

b. Estimation of quantity of bleaching powder required:

The quantity of bleaching powder required to disinfect a particular well can be

estimated by using Horrocks apparatus.

Horrocks Apparatus

Contents:

* 6 white cups, each of 200 ml capacity,


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* 1 black cup with a white circular margin inside, near the brim,

*2 metal spoons, each level spoonful holds 2 gm of bleaching powder,

* 7 glass stirring rods,

* 1 special pipette,

* 2 droppers,

* Starch Iodide indicator.

Procedure

Preparation of stock (standard) chlorine solution:

One level spoonful (2 gm) of bleaching powder is taken in the black- cup and

made into a thin paste by adding little water. Then more of water is added

gradually and stirring till the level reaches the white circular mark. It is stirred

well and allowed to settle, so that calcium of the bleaching Powder settles

down. This is the stock chlorine solution.

Procedure :

* All the six white cups are now filled with water from the well , to be tested forbleaching powder estimation up to a cm below the brim.


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* With the help of the pipette, one drop of stock chlorine solution is added tofirst white cup, two drops to second cup, three drops to third cup, andso on

and six drops to sixth cup.

* The water in each cup is stirred well with separate stirrers for each cup.

* Wait for half an hourfor the action of chlorine in the water (Chlorination).

* Thenthree drops of Starch iodide indicator is added (Starch Cadmium /Potassium iodide) for all the six cups and stirred again.

* Development ofblue color indicates the presence of free residual chlorine.

The intensity of the blue color is directly proportional to the quantity of free

residual chlorine in the water suppose the first cup shows distinct blue

colorfirst, the intensity of color increases subsequently in second, third, fourth,

fifth and sixth cups.

Mechanism: When chlorine solution is added to the white cups, it is utilized by the

organic and ammonical substances for oxidation purposes. Once the oxidation

process is over, free chlorine is left. This is acted upon by starch Cadmium /

Potassium- iodide, resulting in the formation of Cadmium / Potassium chloride

and iodine is set free, which then acts upon the starch giving rise to blue color.

So development of blue color indicates the release or presence of free

residual chlorine in that cup.

Suppose blue color is not obtained even in 6 th cup, the first cup is considered as 7 th

cup and counted subsequently as 8 th, 9th, 10th cup and so on and the test is

continued by adding chlorine solution, 7 drops, 8 drops, so on respectively to all

the remaining cups (i.e. 6 drops to each of the cups in second round).


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The first cup showing distinct blue color is noted. That cup number indicates

the number of level spoonfuls of bleaching powder for disinfecting 455 liters ofwater, so as to give 0.5 ppm of free residual chlorine concentration.

Suppose 1st cup turn blue, then one (the number of the first cup showing distinct

blue color) level spoonful (or 2 gm) of bleaching powder is required to

disinfect 455 litres of water of that particular well, for simple or marginal

chlorination.

For X liters of water in the well, quantity of bleaching powder is estimated.

C. Procedure of Disinfection of Well

The estimated amount of bleaching powder is taken in a bucket and made into a thin

paste by adding little water. Then more of water is added till the bucket is three

fourths full. It is stirred well and allowed to sediment for one minute, so that

lime settles down. The supernatant chlorine solution is transferred to another

bucket and the chalk or lime is discarded and not poured into the well,

because it increases the hardness of well water.

The bucket containing chlorine solution is lowered into the well, below the surface

of the water and agitated vertically and horizontally, so that chlorine solution

mixes with the well water uniformly.

Then contact period of one hour is allowed before the water is drawn for use.

To verify whether water has been properly chlorinated or not, orthotoluidine test is

done. If free residual chlorine level is less than 0.5 ppm after contact period ofone hour, the chlorination procedure should be repeated.

During the epidemics of water borne diseases, wells are super chlorinated everyday,

preferably twice a day, once in the early morning and once in the late afternoon

in case of heavily used wells.


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Continuous Method of Chlorination

To ensure a constant dose of chlorine to the well water, under the circumstances of

epidemic of water borne disease, the National Environmental Engineering

Research Institute, Nagpur has recommended Double Pot Method (Double

jar diffusion method) of chlorination of wells.

This method consists of 2 cylindrical pots, one placed inside the other. The size of

the cylinders being 30 cm height and 25 cm diameter for the outer pot and 28

cm height and 16 cm diameter for the inner pot. Both the pots have an opening

on the side. The outer pot has an opening of about 1 cm diameter near the

bottom and the inner pot has the opening near the brim.

A mixture of 2 kg of coarse sand and 1 kg of bleaching powder is put in the

inner pot and moistened with water. It is then put inside the outer pot. The

surface is then closed with a polythene foil.

The double pot is then lowered into the well by means of a rope, for about 1 metre

below the water surface, to prevent the damage caused by the buckets used by

the public. The water from the outer pot enters into the inner pot, mixes with

bleaching powder mixture. The chlorine solution comes out slowly over a long

period of time, thus ensuring constant chlorination over a long period of about

15-20 days, for a well containing about 4500 liters of water, having a draw off

rate of about 400 ltr per day. After 15-20 days, it needs to be removed,

emptied, refilled and replaced for further chlorination.

Sanitation of Swimming Pool


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The diseases transmitted through swimming pool water are

conjunctivitis,

sinusitis,

otitis media,

sore throat and

athletes foot.

Rarely diseases like typhoid, dysentery, vulvo vaginitis, trachoma have also

been traced.

All these diseases occur due to the contamination of the swimming pool

water from the skin, naso pharynx, urination by the users.

The regulations regarding the construction of the pool, its use, disinfection

procedures, and instructions to the users should be strictly adhered.

Sanitation Measures

* Construction: It should be away from the traffic and dusty roads.

* Area: it should be 2.2 sq m per person swimming.

* Water: There must be continuous circulation of water, coming out from deepend of the pool, passing through a purification plant, (where it undergoes

clarification, filtration and chlorination) and enters the pool from the

shallow end. The free residual chlorine is maintained at a level of about 0.5

ppm, as recommended for drinking water. More than 1.0 ppm of FRC results

in smarting of the eyes. The pH of water is maintained around 7.5.


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The results of bacteriological examinations of samples of water taken from the inlet

and outlet of the purification plant, gives an indication of the effectiveness of the

water treatment. The bacteriological quality of water should be that of pure

drinking water.

About 15 - 20 percent of the water of the pool should be replaced by fresh

water every day in order to remove the nitrates, albuminoidal ammonia and

organic substances derived from the users, because they reduce the

effectiveness of chlorination. Entire water is changed once a week.

Maintenance / Cleanliness

For this purpose, following instructions are strictly enforced.

* No one with cutaneous lesions or discharges from body orifices should enterthe pool.

* Before entry into the pool, the user should empty the bladder and bowel, andclean the nose and throat.

* This is followed by thorough scrub bath with soap and water.

* After the bath, the user should dip his feet in foot bath (consisting of chlorinesolution) then only should enter the pool.

* Swimming costume should be worn.

*Once inside the pool, spitting, blowing of the nose, gargling, urination isforbidden.


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* After leaving the pool, thorough bath should be taken again.

HARDNESS OF WATER

Definition

A hard water is a one which does not readily form leather with soap (In other

words, it is soap destroying quality of water).

Causes

The hardness of water is due to the presence of certain mineral salts in the water

such as bicarbonates, chlorides, sulphates and nitrates of calcium and

magnesium, which form insoluble, sticky precipitate with soap.

Types

There are two types of hardness of water. Temporary and Permanent hardness.

*Temporary (or carbonate) hardness is due to the presence ofbicarbonates ofcalcium and magnesium.

* Permanent (or non carbonate) hardness is due to the presence ofsulphates, chlorides and nitrates of calcium and magnesium.

Measurement


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Hardness of the water is measured or estimated by using a standardized titrant,

Ethylene Diamine Tetra Acetic Acid (EDTA). The results are expressed as mg

of CaCO3 per litre of water, i.e. milli Equivalents per litre (mEq/L). 1 mEq / L of

hardness is equal to 50 mg of CaCO3 (calcium carbonate) (or 50 ppm) per

litre of water, as suggested by WHO in its International Standards ofDrinking Water.

Grading of Hardness of Water

* Less than 1 mEq/L (i.e., 300 ppm) It is very hard water. Drinking water shouldbe moderately hard (1-3 mEq/L). The question of softening the water arises if

the hardness exceeds 3 mEq/L.

The degree of hardness can also be measured by Clarks method. According tohim, the same four grades are expressed respectively as 30 percent.

The hardness of water is not only dependant on the geology of the region in which

the water is found but also by the pollution with sewage and many other wastes.

Limestone regions produce water containing considerable hardness. Granite

areas produce soft waters.

Advantages of Hard water

Recent studies have shown an inverse correlation between the hardness of water

supplied to the community and its cardiovascular mortality rate. The areas

supplied with soft drinking water showed a higher prevalence rate ofcardiovascular mortality rate proving that hard water is cardio -protective.


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Disadvantages of Hard water

* It causes great wastage of soap

* It causes precipitation of carbonates and forms scales in the boilers, leading togreater fuel consumption, loss of efficiency and even explosions of boilers

resulting in industrial economic loss.

* It affects cooking adversely

* It causes irritation of skin and gastrointestinal system

* It reduces the life of clothes washed with soap in hard water.

Removal of Hardness

# Temporary hardness (due to carbonates and bicarbonates of Ca and Mg) can be

removed by processes like boiling of water,

addition of lime,

Sodium Carbonate and

Permutit process.


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# Permanent hardness (due to chlorides and sulphates of Ca and Mg) can be

removed by last two processes,

i.e. by addition ofSodium carbonate and

by Permutit process. ( Base Exchange Process )

b. Addition of lime: For example, calcium hydroxide, when added to water,

absorbs carbon dioxide and precipitates insoluble calcium carbonates,

resulting in softening of water.

Meanwhile it accomplishes magnesium reduction.

Ca (OH)2+ Ca (HCO3)2 ---- 2CaCO3 + 2H2O

Ca (OH)2 + Mg (HCO3)2 ---- MgCO3 + CaCO3 + 2H2O

Ca (OH)2 + Mg CO3 ---- CaCO3 + Mg (OH)2


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d. Permutit process: Synonyms are Ion exchange process; base exchange

process; zeolite softening. In this process both temporary and permanent

hardness are removed. Zeolite is a mineral consisting of sodium, aluminium and

silica. It is also called as sodium permutit (or sodium zeolite) Na2Z. When

this is added to hard water, the Ca and Mg ions exchange with Na2Z and formsCa and Mg permutit and the water is softened to zero hardness. The reaction

is as follows:

Ca (HCO3)2 Ca 2NaHCO3

Na2Z + SO4 ------------ Z + Na2SO4

Mg Cl2 Mg 2NaCl

Since the soft water of zero hardness has a corrosive propertyon pipes, so raw

water is again mixed to the soft water to secure the desired level of hardness,

i.e. 1 to 3 mEq/L.

WATER HARVESTING

CONSERVATION OF WATER RESOURCES

* Industrialization, urbanization and deforestation, and populationexplosion has resulted in the shrinkage of surface waters (rivers, ponds,

lakes etc). People are meeting their demand for water, by resorting to tapping

sub soil resources of water.

* This has resulted in alarming fall in the ground water resources mainlybecause of the dependency of irrigation on tube wells.

*Therefore , before it is too late, the underground water resources shouldbe conserved.


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The term conservation means

* protection of water resources and

*further building up the reserves.

# Conservation has thus 2 components:

* Protection of Water Resources

This can be done by preventing the wastage of water.

This requires extensive education of the public, about the economical use of water

and to consume minimum requirement for daily use.

** Building up of Sub-soil Water Reserves

This is also called as Water harvesting.

This can be done by draining the rain water using PVC pipes, from top of the

buildings and courtyards into soaking pits or trenches, instead of drains,

followed by filtration using sand and gravel and then letting into existing tube

wells or wells.

Various economic designs have been suggested by agencies like UNICEF,

Central Ground Water Board, etc.

Ground Water set to be made Public Property


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*Ground water, a precious natural resource, for all practical purposes isconsidered as private property in our country.

Any one can bore and extract water with few rules to restrict over-exploitation.

But this could soon change.

Plans are afoot to alter laws and regulations to make ground water a common

property resource, whereby communities will manage underground aquifers

and the Govt will regulate their use in the role of a public trustee.

A law that ensures that groundwater is treated as public and

not private property is long overdue.

Thus water will be treated like any other natural resources extracted from the

ground, like oil, gas and other minerals.

Presently, any one sinking a bore well on his or her territory is not tapping into water

only under his or her plot but from the common water table. (Times of India,

18 July 2012)

SANITARY ANALYSIS OF WATER

Information is obtained from two sources, i.e.,

* Field surveys of the water source and


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**Laboratory examination report of the water samples.

Field Survey

This includes the collection of data on :

i. the natureandsource of water supply,

ii. likely sources ofwaterpollution,

iii. modeof filtration,

iv. mode of distribution

v. and such other information, as would be relevant from the sanitary point of

view.


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Laboratory Examination of Water Samples

Examination indicates whether the collected sample of water contains harmful or

undesirable substances.

Collection of Sample of Water

The method of collection of sample and quantity requirement of water are different

for different types of analyses:

1. For routine physical, chemical and biological examination,

2 litres sample should be collected in a clean glass bottle,

recommended is WinchesterQuart bottle.

2. For Bacteriological analysis, 200 cc of water should be collected in asterile bottle, sterilized in an autoclave.

3. For Radiological analysis, polythene bottle is preferred.

Sampling Technique

The sample of water must be thoroughly representative of the water to be

analysed.

1. In collecting waterfrom a river, stream or lake, the sample should be obtained

from a mid stream and not too near the bank and the surface pollution

should be avoided, by placing the bottle well under the surface of the water.

2. If the water has to be collected from the taps, the water is allowed to run to

waste for a few minutes and then collected.


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# Source of water, the temperature of the water at the time of collection, is also

recorded on the proforma.

## The bottle containing water sample is closed with stopper

and sealed.

## # It is sent preferably in an ice box to the laboratory for examination

purpose, shorter the time elapsing between collection and analysis, more

reliable are the results.

Laboratory Examination of water

This includes the following:

1. Physical examination

2. Chemical examination

3. Biological examination

4. Bacteriological examination

5. Radiological examination, and

6. Virological examination

.

1. Physical Examination of Water

This is done to determine the presence of those substances in the water which affect

the physicaloraesthetic quality of water, such as odour, taste, colourand

turbidity.


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* Fluorides are usually present in higher concentration

in ground waters than surface water.

* Its concentration is closely related to dental and skeletal health.

* Excess fluoride level results in dental and skeletal fluorosis anddecreased level in the water results in dental caries. Therefore, fluoride in

water is often called as A Double Edged Weapon.

* The optimum concentration for drinking purpose is

0.5 to 0.8 mg / L (ppm)

but the upper permissible limit is 1.5 mg / L (1.5 ppm).

The methods recommended for estimation of fluorides in water are

* Colorimetric method, using zirconium alizarin reagent,

* Electrochemical method using Orion electrode.

* SPANDS colorimetric method.

ii. Nitrates and nitrites:

* Even though these are the naturally occurring ions of the nitrogen cycle, they areconsidered as the indicators of pollution in water.


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* Maximum Recommended Limits in water are as under:

Nitrate ( as NO3 ) - 50 mg/Ltr

Nitrite ( as NO2 ) - 3 mg/Ltr (provisional)

* Because of the possibility of simultaneous occurrence of nitrate and nitrite in drinking water , the sum of the ratios of the concentration of each

to the guide line value should not exceed one . Guide line value for nitrates & nitrites in

drinking water is solely to prevent methaemoglobulinaemia, since bottle

fed infants of less than 3 months of age are most susceptible.

Concentration of nitrate Concentration of nitrite

---------------------------------------------------- + ------------------------------------ = < 1

Guide line value of nitrate Guide line value of nitrite

l


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Substances affecting the potability of water

3. Biological Examination of Water

* This includes examination of water under the microscope for the presence ofmicroscopic substances (excluding bacteria) such as algae, fungi, protozoa,

ova, cyst, yeast, rotifers, crustacea, small worms, insect larvae, etc. which

are all collectively called asPlankton.

* These are responsible for the production of objectionable colour, odourand taste in the water.

* Therefore, their presence is an index of pollution or sewage contamination.

4. Bacteriological Examination of Water


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# The bacteriological examination of water is a

very delicate and sensitive test fordetecting the contamination of waterby

sewageorhuman excreta.

# The bacterial indicator of contamination of water, is the coliform group of

organisms,

which consists of both faecal and non faecal organisms.

# The typical example of faecal coliform group is E.coli and non faecal coliform

is klebsiella aerogenes

(or Enterobacter aerogenes).

# Non faecal type is found in soil, fruits, leaves, grains, etc.

## The supplementary bacterial indicators

offaecal contamination are faecal Streptococci and

Clostridium perfringens.

These indicators also help in assessing the efficiency of water purification

processes.

## Because of the difficulty in differentiation

between fecal and non fecal coliforms ,


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for all practical purposes ,

it is assumed that

all coliform group of organisms are of faecal origin, unless the

non faecal origin is proved.

Reasons for exclusively choosing the coliform organisms (specially E coli) as

an indicator of fecal pollution are:

1. They are present in large numbers in the human intestine

* A person excretes on an average about 200 400 billion of these organismsper day.

2. They can be easily detected by cultural method

as small as one bacteria in 100 ml of watercan be isolated.

* The methods for detecting other human intestinal organisms like salmonella,shigella, etc are complicated and time consuming.

3. They tend to live longer than pathogens


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4. They have greater resistance to the forces of natural purification than other

pathogens.

* If the coliform organisms are present in a water sample, the assumption is

the probable presence of intestinal pathogens.

* So consequently the assumption is justified , in that

if coliform organisms have been eliminated from water, the pathogens also

have disappeared.

# Faecal Streptococci

This is considered as a supplementary indicator of faecal pollution of water

because it also regularly occurs in faeces ,


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but in much smaller numbers than E.coli.

Therefore, its presence in a water sample is considered as a confirmatory

evidence ofrecent faecal pollution of water.

## Clostridium perfringens

They also occur regularly in faeces but in smaller numbers than E.coli.

The spores of Cl. perfringens are capable of surviving for a longer period than

E.coli and are resistant to chlorine.

** Their presence in the absence of E.coli in a sample of watersuggests that

contamination had occurred at some remote time.

The bacteriological tests carried out are

* Plate count

* Standard tests

* Tests for the presence of fecal Streptococci and Cl. perfingens.

Interpretation of Results of Disinfected Water


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*No coliforms in 100 cc. of water Excellent water

* 1 2 coliforms in 100 cc. of water Satisfactory water

* 3 10 coliforms in 100 cc. of water Suspicious water

* More than 10 coliform in 100 cc. of water Unsatisfactory water.

* However ,

there should be no E. coli in any 100 ml sample

5. Radiological Examination of Water

Pollution of water with radioactive materials

causes health hazard.

The radioactivity is expressed as micro micro curies (i.e. picocuries pci) per

liter of water.

1 pci = 2.22 radioactive disintegrations per minute.


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WHO has proposed the following standards as acceptable upper limit.

Gross alpha activity = 3 pci / L.

Gross beta activity = 30 pci/L.

6. Virological Examination of Water

Enteroviruses, rheoviruses and adenoviruses have been found in water, enteroviruses are more resistant to chlorination.

If, Entero viruses are absent from chlorinated water,

it can be assumed that water is safe to drink.

An exponential relationship exists between the rate of virus inactivation and the

redox potential. A redox potential of 650 mV (measured between platinum and

calomel electrodes) will cause almost instantaneous inactivation of even high

concentration of virus. Such a potential can be obtained even with a lowconcentration of free chlorine of 0.5 mg / L for 1 hour, to inactivate the viruses.

WHO has fixed the upper limit for viruses as 1 PFU (Plaque Forming Unit) per

liter of water.

Primary Secondary

Treatment ( ANAEROBIC ) Treatment

( AEROBIC) CHLORINE

Sewage


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Effluent

Disposal

Activated Sea Outfall

River Outfall

Sewage Farm

Sludge

Oxidation Pond Oxidation

Ditches

Alterna

te

Sludge to

digester Excess sludge

to

digester or

Excess sludge Return and excess sludge

thickener


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AIR

and

VENTILATION

Air and Ventilation

INTRODUCTION

* Air constitutes the immediate physical environment.

* Life would not have existed without air .

## The public health importance of air is that


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it is necessary forbreathing purposes,

cooling of the body,

hearing and

smelling

more importantly air acts as a

vehicle for transmission of diseases.

* Air is a mixture of gasses, mainly nitrogen (78%), oxygen (21%) and carbondioxide (0.03%), remaining are other gasses such as argon, neon, helium,

xenon, etc.

* Truly speaking, there is no pure air.

Air always contains foreign substances in the form of solid, liquid (moisture) and

gasses, at all times.

* Air is said to be polluted when it contains foreign substancessuch as dust,

bacteria,

spores,


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gases in excessive concentration,

so as to affect the health of human beings and animals and causes damage to

plants and properties.

Changes in the Air Due to Human Occupancy

in the room are physical and chemical, and

also due to bacterial pollution.

1. The physical changes are:

i. Rise in the temperature due to release of body heat.

ii. Rise in the relative humidity due to expiration and perspiration.

iii. Decrease in the air movement.

iv. Occurrence ofunpleasant odours arising from expiration, perspiration, bad oral

hygiene,

dirty clothes and other sources.


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EFFECTS OF VITIATED AIR

They are divided into acute and chronic.

# Acute effects are lassitude, head ache, nausea, vertigo, vomiting and evencollapse.

Death may occur in extreme cases.

## Chronic effects are anemia, debility, digestive disturbances, nutritional and

metabolic disorders, lowered vitality and decreased resistance to

infections.

**The workingefficiency is decreased and

** the output of the work falls.

The effects of vitiation of air was first observed by Sir Leonard Hill.

INDICATORS OF THERMAL COMFORT

i. Air Temperature

This alone is not adequate indicator.


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ii. Air Temperature and Humidity

This is a better indicator than air temperature alone but still this is

unsatisfactory.

iii. Air Temperature, Humidity and Air movement

These three together is called Cooling Power of the air, which can be

measured by a device called Kata thermometer.

A dry kata reading of6 and above and

a wet kata reading of20 and above are regarded as an index of thermal comfort.


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Kata thermometer

* Effective Temperature (ET)

It is the combined effect of

- air temperature,

- humidity and

- air movement (cooling power)

on the sensation ofwarmth orcold felt by the human body.

But this does not include the effect of radiation from the surrounding

structures.

McArdles Maximum Allowable Sweat RATE


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It is recorded as

Predicted four hour sweat rate (P4SR).

It is the rate at which a person sweats in hot environment and is expressed for four

hours.

It is an indicator of heat stress.

The upper limit of P4SR is 3 litres.

Range is 1-3 Ltr, Average 2 litres

(i.e. A sweat rate of 2 liters in 4 hours in considered optimal for a man working in a

hot environment).

METEOROLOGY

INTRODUCTION

The components of meteorological environment are:

* Atmospheric pressure

* Air temperature


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* Humidity

*Air movement(Air velocity)

(Directionandspeedof the wind)

ATMOSPHERIC PRESSURE

The instrument used to measure atmospheric pressure is called Barometer

Kew Pattern Station barometer is widely used. Others are Fortins Barometer,

Aneroid Barometerand Barograph.

Effects on Health

The influence of atmospheric pressure on health is considered under two headings.

* Effects ofdiminished atmospheric pressure.

* Effects ofincreased atmospheric pressure.

aneroid Barometer fortins Barometer

* Effects of Diminished Atmospheric Pressure


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As we ascend atmospheric air becomes rarefied with diminished pressure and

oxygen contents.

For instance atmospheric pressure at Mumai is 760 mm of Hg,

at Leh(12000 ft.) it is less than 500, &

at Khardung La (18380 ft) it is less than 400.

Similarly, temperature also decreases roughly at the rate of 0.650C per 100 m

ascend till it reaches & stabilizes at minus 550 C.

# Effects of diminished atmospheric pressure are:

i. Acute Mountain Sickness

ii. High Altitude Pulmonary Oedema (HAPO)

iii. High Altitude Cerebral Oedema (HACO)

iv. High Altitude Pulmonary Hypertension

## Effects of diminished temperature are:

i. Chilblains

ii. Frost Bite

iii. Trench Foot


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### Effects of solar radiation

i. On Skin

ii. On Eyes

* Effects of Increased Atmospheric Pressure

As we descend from sea level the atmospheric pressure increases at the rate of one

atmospheric pressure forevery 33 ft descent.

That is to say that at 33 ft descent the atmospheric pressure will be equivalent to

two atmospheric pressure (760 x 2 mm Hg) &

At 66 ft depth it will be equivalent to 3 atmospheric pressure (760 x 3 mm Hg)

# Increased atmospheric pressure causes:

i. Caissons disease

AIR TEMPERATURE

Measurement

Air temperature is recorded by using the following thermometers in Fahrenheitscale / centigrade scale.


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a. Dry bulb thermometer: This is an ordinary mercurial thermometer, placed in

Stevensons screen to protect from, direct sun and rain, at a height of about

1.5 meters above the ground level. It records the temperature of the air.

b. Wet bulb thermometer: It is similar to dry bulb thermometer, except that the bulb

is kept wet by means of a muslin cloth, fed by water, from a bottle through

a wick.

As the water from the muslin cloth evaporates, the mercury column comes

down. Thus the wet bulb thermometer shows a lower temperature reading in

response to the heat lost by wet cloth through evaporation, than the dry bulb

thermometer.

Drier the air, lower the wet bulb reading.

If the wet and dry bulb thermometers record the same identical temperature,

it means the airis completely saturated with moisture, which is rare or never

occurs.

The difference between the dry and wet bulb thermometers increases with

increasing dryness of air and vice versa.

Stevensons screen

c. Maximum thermometer

d. Minimum thermometer

e. Sixs maximum and minimum thermometer

f. Vacuum or solar radiation thermometer

g. Terrestrial thermometer

h. Silvered thermometer


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i. Globe thermometer


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Globe thermometer:

This consists of a hollow sphere, made up of copper, 15 cm in diameter coated with

black paint on the surfaces.

The hollow sphere has an opening at the top through which a mercury thermometer

is inserted such that the bulb is in the center of the globe.

Due to globe, the thermometer absorbs radiant heat from the surroundings.

The globe thermometer records a higher temperature than the ordinary dry bulb

thermometer because it is affected by both the air temperature and theradiant heat of the surroundings.

Therefore, the difference between the reading ofthe globethermometerand the

ordinary dry bulb thermometer is a measure of the radiant heat.

*The globe thermometer is also influenced by the velocity of the airmovement.

Globe thermometer

HUMIDITY

Atmospheric humidity means the moisture content of the air, which in turn

depends upon the air temperature.

Lower the temperature of air, higher the moisture content (Humidity) and vice versa.

The temperature at which the moisture precipitates is called Dew point.


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Humidity may be expressed as absolute humidity or relative humidity.

Absolute Humidity

It is the actual amount of moisture (or water vapor) in an unit volume of air.

It is expressed as grams per cubic meterof air.

Relative Humidity (RH)

It is the percentage of moisture present in the air, complete saturation being taken

as 100. Greater the relative humidity, the nearer the air to saturation.

This is more commonly employed to express the humidity.

# Even though humidity has no effect on the health of the individual, definitely it

has an effect on the comfort.

# If RH is more than 65 percent, air feels sticky and uncomfortable.

# RH can be lowered by ventilation.

# RH below 30 per cent over long period results in drying of nasal mucosa

predisposing for infection. Thus it is also uncomfortable.

# So the RH between 30 to 65 percent constitutes Comfort zone to the worker

in the working place.


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Measurement

The humidity of the air can be measured by an instrument called Hygrometer, of

which there are 2 kinds namely Direct and Indirect hygrometers.

* Direct Hygrometers are Danniells Hygrometer,

Regnaults Hygrometer and

Dines Hygrometer.

**Indirect Hygrometers are

- dry and wet bulb hygrometers,

- Sling psychrometerand

- Assmann psychrometer.

Dry and Wet Bulb Hygrometer

This consists of two thermometers a dry bulb thermometer and a wet bulb

thermometer.

Both are alcohol thermometers, mounted side by side on a stand. The former

measures the air temperature. The latter is so called because the bulb is always

kept moist by covering with a thin muslin cloth, kept moist with water. So the

wet bulb reading is always lower than the other.


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The difference between the two thermometer readings is referred to psychrometric

chart orslide rule and the relative humidity can be found.

Greater the difference, greater is the RH.

If both the readings are the same, it indicates that the atmosphere is cent percentsaturated with moisture, which never occur in reality.

For effective readings, the air should pass over the bulb with a speed of about 5

meters per second. The sling psychrometer achieves this when rotated rapidly.

Sling Psychrometer

This consists of 2 mercury thermometers dry and wet,

the latter bulb is covered with a thin muslin cloth and kept moist with water. Both the

thermometers are identical and mounted side by side on a wooden frame,

which is provided with a handle to whirl rapidly.

Principle: By rotating, both the bulbs are exposed to air at definite velocity.

Procedure: At the time of use, the muslin covering should be thoroughly saturated

with distilled water and the instrument is rotated orwhirled rapidly, at the rate

of 4 revolutions per second, so as to obtain a desirable air speed of5 meters

per second, for about 15 seconds, stopped and wet bulb reading is

noted.

This is repeated several times till the two successive wet bulb readings are

identical, showing that it has reached its lowest temperature.

Now the dry bulb reading is also taken, which is the true temperature of the air.

Sling psychrometer


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The difference between the two readings (dry and wet bulb) is referred to the

psychrometric chart and the percentage of RH is obtained.

Greater the difference, greater is the RH.

# The difference between the two readings helps us to obtain - relative

humidity,

- dew point and

- vapor pressure of the air.

AIR MOVEMENT

The best instrument used to record the velocity of air and also the pressure of the

wind is Robinsons Wind Anemometer.

Anemometer

Wind direction


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Rain gauze

AIR POLLUTION

Air pollution is a constant and menacing problem throughout the world, due to

mans own activities like industrialization and urbanization.

It is increasing continuously during the past few decades.

Air pollution is not only a public health problem but also an economic problem.

Air Pollutants

These may be physical, chemical orbiological.

1.Physical Pollutants

. Particulate matters: Dust, smoke, soot, sand, grit

2. Chemical Pollutants

Gases: CO, CO2, H2S, CH4, NO2, SO2,

Chloro Fluoro Carbons etc.

Metals: As, Be, Cu, Zn, Pb,

Carcinogens

2. Biological Pollutants

Pathogens (microbes), spores, etc.


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Although the Earths atmosphere extends to several km above the surface, it is only

the first 30 km that hold the major portion of the atmospheric gases.

Man is concerned only with the first 8 10 km of the atmosphere.

FACTORS INFLUENCING Air Pollution

# Degree of air pollution is influenced by topography, i.e. atmospheric

temperature,

humidity,

atmospheric pressure and

air movement.

# Pollutants are also affectedby

sunlight and

temperature inversion.

Air Movement


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Normally the air near the surface of the earth is warmerthan the air higher up.

So warmer air, being lighter, moves up, expands and becomes cool.

Thus the pollution is dilutedanddispersed,

while the air of the upper layerbeing cool and heavy,

comes down (turbulent flow).

* If Fog is present along with temperature inversion,

water vapor condenses around the smoke particles and forms Smog. (Water

vapor + Smoke = Smog).

Intense smog is lethal.

Such temperature inversion often persists for several days, resulting in acute

episodes ofrespiratory illness, suffocation and death.

Highly susceptible population groups are

young children,


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elderly people and

those suffering from lung diseases and

heart diseases.

Sources of Air Pollution

i. Domestic : Burning of fire wood, kerosene oil, coal, etc.

ii. Industrial : Factories of iron and steel, paper, cement, fertilizers, thermal

power plant, petroleum refineries, etc.

iii. Automobiles: Motor vehicles, railways, ships,

aero planes, etc.

iv. Miscellaneous: Tobacco smoking, nuclear explosions, forest fires,

volcanoes, burning of refuse, dust storm, ocean spray, etc.

.

Hazards of Air Pollution

# Immediate and Acute Effects

These are due to photochemical oxidants.


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These are irritation of conjunctiva, nose, throat and respiratory mucous membrane

resulting in conjunctivitis, allergic rhinitis, acute pharyngitis, acute

bronchitis and episodes ofbronchial asthma (acute attacks).

It may result in suffocation and death.

For example, London disaster in England and Bhopal gas tragedy in India

## Delayed and Chronic Effects

These are chronic bronchitis, bronchiectasis, emphysema, chronic

obstructive pulmonary disease (COPD), bronchial asthma and even lung

cancer.

Global Effects of Air Pollution

i. Acid rain:

* It is the end result of several processes occurring in the atmosphere.

* Sulphur dioxide emitted from combustion of coal produces sulphuric acid by

getting dissolved in water vapor of the atmosphere.

* Similarly carbon-dioxide produces carbonic acid and nitrogen dioxide

produces nitric acid.

* Thus the rainfall containing sulphuric acid, carbonic acid and nitric acid produces

devastating ecological effect by causing acidification ofsoilandwater.

* Trees killed by acid rain results in deforestation, desertification and erosion of

soil, thus disturbing the ecosystem.

* Acidification of water bodies destroys aquatic life including fish.

* Destruction of food crops effects food production also.


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ii. Global warming:

It is a phenomenon occurring in the troposphere.

Normally, the atmospheric gases have a green-house effect, i.e. like the glass

of a green house,

allowlight andwarmth to reach the earth

but they do not allow warmthto be lost,

thus maintaining life on earth

## In air pollution,

there is rise in gases like carbon dioxide, methane and

chlorofluorocarbons and accumulation of ozone, they elevate

the global temperature

thusresulting in global warming and

affecting the ecosystem.

In the past 10 years, a rise of 0.3 to 0.6 degree Celsius has been noticed.

## Global Warming has resulted in following effects:

* Increase in the dryness of the climate


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* Reduction in the world food production

*Melting ofpolar ice caps

* Rise in sea level and also resulting in floods

* Smog formation

* Increased incidence ofskin cancerand cataract

* Spread oftropical diseases to temperate regions.

iii. Effects of depleted ozone shield:

## Normallyozone layer of the earth, filters the harmful U-V rays of the sun

and prevents them from reaching the surface of the earth.

## Because of air pollution, ozone layer begins to thin out and results in thefollowing effects :

* Inhibitionof photosynthesis, (due to burning of leaves, retardation of growth of

plants, fall in the crop yield, ageing of plants etc, all due to air pollution).

* Disruption ofmarine food chain

* Impairment ofhuman immune mechanisms, predisposing for infections

* Ocular damage (cataract)


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* Skin Cancers (melanotic and non melanotic)

* U-V rays also cause damage ofsmall forms of life such as plankton, pollen

grains and nitrifyingsoilbacteria.

iv. On animals: Cattle become weak and cachexic, Yield of animal products

become less.

v. Miscellaneous : (Socio economic hazards)

* Damage to buildings, like old monuments,

* Damage to metals, alloys, textile, rubber and works on wood, bronze andstone (like painting, carvings).

* Repair costs millions of rupees.

(thus time, money and energy are wasted).


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* Air pollution index: it is an arbitrary index, considering one or more pollutantsas a measure of severity of pollution.

Example: (Employed in USA)

10 times SO2concentration, plus

twice CO concentration plus

twice the coefficient of haze.

It is considered as an alarming when this value becomes more than

50.

Prevention and Control of Air Pollution

By 3 measures:

i. Engineering technology

ii. Legislations and

iii. General measures.

i. Engineering technology:

a. Location of the industries: Industries must be located away from the human

habitations and where topography of the soil is favourable.

b. Replacement measures: Within the industries, the processes causing air

pollution should be replaced by the processes preventing air pollution.

For example: Using electricityinstead of fuels,

Using LPG (smokeless fuel) in the place of coal.


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c. Containment measures: such as

* * Controlling the production of dust by wet method.

* * Prevention of the escape of dust into the atmosphere byusing enclosure hood,

* exhaust pipes for removal, and also

* * Increasing the height of smoke vent, etc.

*

.

iii. General measures:

* Control of traffic by construction ofby-pass roads.


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**Maintenance of vehicles by periodical servicing, mixing of petrol and oil in

proper proportions,

use ofunleaded petrol to the vehicles,

fitting the catalytic converter to the exhausts pipes of four wheelers, whichconvert the harmful gas into harmless gas.

***Establishment of Green-belts, i.e. growing plants and trees between the

industries and the residential areas, so that the leaves absorb carbon

dioxide and give out oxygen.

****Health education of the people about hazards of air pollution and their role in

the prevention and control of air pollution.

*****Populationstabilization.

VENTILATION

Ventilation is not only the replacement of vitiated air (stagnant, warm and moist

air) by the drier, cooler and moving air but it also control the quality of

incoming air

so as to have adequate control over the temperature, humidity and purity with

a view to provide a comfortable environment without the risk of infection.


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## Air change: For a person to get 3000 cu ft of air per hour and occupying a room

of 100 cu.ft. the air should be changed thirty times per hour or

if he occupies a room of 1000 cu.ft. air requires to be changed only three times.

This causes a disagreeable draught specially in cold weather. Otherwise it does

not cause any perceptible draught.

## Floor area:

This is an important standard of ventilation.

The optimum floor area per person in a house recommended is 50 100 sq. feet.

Lesser than 50 sq. feet results in over crowding favoring spread of droplet

infections.

In general hospital it should be 150 sq ft and

In infectious disease hospital, it should be 200 sq ft per person.

Systems of Ventilation

Mainly there are two systems of ventilation, namely Natural and Artificial, depending

upon the motive power, which originates them.

A. Natural ventilation: This depends upon 3 factors.

i. Perflation and aspiration of the wind.

ii. Difference of temperature

iii. Diffusion of gases.


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Natural ventilation helps considerably, if the buildings are constructed with sufficient

open space around and by having large number of windows, preferably

opening direct into the outside air. Cross ventilation means perflation

between windows and other openings placed opposite to each other.

Naturally cross ventilation becomes impossible in back to back houses.

ii. Effects of difference of temperature:

Air always flows from high density to low density.

# Out side cool airis of high density, rushes in through every opening ofthe room

(or through the inlets placed at lower level).

Inside air of the room being of lower density moves up.

The greater the difference of temperature between the outer cooler air and the inner

warmer air, greater will be the velocity of the incoming air, until the temperature

of both outside and inside air becomes equal.

Since the incoming air gets warmed up, a constant current is maintained. This is the

basis of natural ventilation.

# The reverse process takes place in the tropics, where the outside air is better

than the inside air.

But in cold countries, fire is used inside the room to keep the inside air warm.


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B. Artificial ventilation: (Mechanical ventilation)

These are of the four types.

i. Vacuum system

ii. Plenum system

iii. Balanced system and

iv. Air conditioning.

i. Vacuum system: (Exhaust system or extraction system).

In this system foul, vitiated air is extracted or exhausted to the outside by using

exhaust fans, operated electrically, so that vacuum is created and fresh air

enters in and fill its place.

They are usually provided in large halls, auditorium, cinema halls and are fixed near

the roof, because vitiated air is warmer and moves up.

Ventilation may be controlled by adjusting the speed of the fans. They are also

employed in the industries to remove dusts, fumes and other contaminants at

their source.

iv. Air conditioning:


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In this system, the outer air is conditioned or controlled with reference to

physical and chemical conditions, such as cleaning (free from pathogens, dirt

and dust), adjustment of temperature (to cool it or warm it), adjustment of

humidity, which will be most comfortable and then letting into the room at a

measured rate and volume of flow without producing draught and exhaustedthrough ducts.

These are being increasingly used in operation theatres of the hospitals, in hotels,

restaurants, offices, commercial firms, cinemas, aero planes, railways, etc.

When the temperature difference between the outside air and air conditioned room is

very large, transition rooms are provided, so as to prevent sudden exposure

to high or low temperature.

The advantages of artificial methods of ventilation are the constancy and the facility

with which fresh air is supplied under all conditions,

whereas natural ones though less costly are not under human control being subject

to atmospheric conditions.

NOISE


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Noise

INTRODUCTION

Noise is an unwanted sound, causing disturbance or annoyance to the hearer.

Therefore, noise is a nuisance.

The term Noise pollution signifies the cacophony of sounds that are being

produced in the modern life, leading to health hazard.

## Noise has two measurable properties

- Frequency and

- Intensity.

Noise Level Values

Whispering 20 to 30 dB

Normal conversion 30 to 65 dB

(Maximum upper limit is 85 dB)

Street traffic 60 to 80 dB

Shouting about 100 dB

Motor car horn, boiler factories about 120 dB


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Train, Aero plane engine about 120 dB

Threshold of pain about 140 dB

Jet plane about 150 dB

Mechanical damage 150 160 dB

Instruments used in the Study of Noise

i. Sound level meter measures the intensity of sound in

decibel (dB).

ii. Octave band frequency analyzer indicates whether the intensity is high

pitched or low pitched. - Hz

iii. Audiometer measures the hearing ability.

Zero line at the top of the audiogram represents normal hearing


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Non auditory Effects

* Interference with speech communication.

* Annoyance (such as irritability, short temperedness, impatience, quarreling anddecreased production in the industries)

* Decreased efficiency in the work

* Lack of concentration

* Physiological changes such as

interference with sleep,

rise in blood pressure,

rise in intracranial pressure,

increase in heart-rate and breathing rate,

increase in sweating,

headache, giddiness, nausea, fatigue,

visual disturbances, etc.

PREVENTI

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Environment & Health