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ENVIRONMENT & HEALTH

BY

DR JASDEEP SINGH



ENVIRONMENT & HEALTH

We are surrounded by various living & non- living things,

that includes materials as well as non- materials.

our environment comprises of :

I. Physical Environment :

II. Biological Environment

III. Social Environment

IV. Cultural Environment

contd….



i) Physical Environment

This consists of non living things like;

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

ii) Biological Environment :

This consists of living things of animal &plant origin like; rodents, insects, microbes (bacteria, virus, rickettsiae, parasites, fungi )

iii) Social Environment

consists of occupation, literacy, income, religion, standardof 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 livingorganisms 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,

clear &

free from any colour and odour .



A safe water with unpleasant taste or appearance

may derive the consumer to other less safe

sources.

iv) Usable for domestic 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



Uses of Water

i) Domestic use Drinking

Cooking Washing

Bathing

Flushing of Toilets

Gardening etc

ii) Public purpose Cleaning streets Recreational

Swimming pools

Fountains

Ornamental ponds

Fire Fighting

Public Parks

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

It can eliminate diseases, promote development and improve quality of

life.

iii. IndustrialFor processing & cooling

iv. AgriculturalIrrigation

v. Power GenerationHydro power andSteam power

vi. For Carrying away wastes from establishments and

institutions.



Sources of water

i. Rain

ii. Surface water

Impounding Reservoir

Rivers & Streams

Tanks, Ponds & Lakes

iii . Ground Water

Shallow well Deep well

Artesian well

Tube well

Springs



i. Rain water is 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 automobiles using fossil fuel.

This results in acid rain.

Gibraltar depends 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–



# 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 such reservoirs. Purity of water in these reservoirs is good,

it is next to rain water.

However, prolonged storage leads to growth of algae and other microscopic organisms, which imparts bad

taste & odour to water.

If surrounding hills are covered with peat, the water

may acquire brownish colouration.



## Rivers

Cities like Delhi, Allahabad, Kolkata derive water from

rivers.

River water is grossly polluted &

is unfit for drinking unless subjected to

treatment.

Rivers have been described as a direct connection

between the alimentary canal of people living up steamsand the mouth of those staying down streams.

Rivers derive impurities from sewage,

sulla e ,



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 filteringmedia.

However, mineral contents may be high andvary from place to place.

This may render the water hard.



# Wells may be – Shallow

or Deep well

If the water is drawn from above the first

impervious layer , it is called as shallow well,

where as if the water is drawn from below the first

impervious layer , it is deep well.

Accordingly,water from shallow wells is grossly

contaminated, yield is

low and

is not constant











# 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.

# Springs

When ground 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

O O



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:

Sewage

Industrial & trade wastes Agricultural pollutants

Physical pollutants

Water and Disease



Water and Disease

WHO estimates that as much as 80 per cent of all diseases inthe world are associated with water .

These diseases can be grouped as under:Sewage pollution

Industrial pollution

Hazards from pipe material

Effects of soil contentsHardness of water

Diseases due to shortage of water

Other pollutants

fertilizers and pesticides

radioactive substances

.

i S ll i



i. Sewage pollution

Sewage pollution can cause variousgastrointestinal and other diseases likediarrhoea,

dysentery,

cholera,typhoid,

infectious hepatitis,

polio,

amoebiasis andother parasitic diseases due to roundworm,

threadworm, whipworm,

fish tapeworm,

do ta eworm,

ii Industrial pollution



ii. Industrial pollutionNumerous 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 concentrationshould not exceed maximum permissible levels.

.

H d f i t i l



iii. Hazards from pipe materialProblems may also arise from the distribution pipes.

Material used for water pipes should not contain any hazardous

metal.

Pipes and other fittings used in water supply system should be of

prescribed standards and should not contain any toxic element as an

impurity.

In this respect cooperation from the pipe manufacturers is of

utmost importance.

Stringent legislative measures should be adopted wherever necessary.

Tar coating, used in water pipes (concrete pipes), discharges certain

aromatic carcinogens and its use as coating should bestrictl forbidden in an water

i Eff t f il t t



iv. Effects of soil contents

Fluorides and iodine contents of soil can also affectthe health through drinking water.

Fluorosis, a crippling disease of the skeletal system

is due to the excessive intake of fluorides throughwater.

It is a public health problem in some areas of thePunjab, Andhra Pradesh and certain other states.

Whereas deficiency of fluorides has been associatedwith high incidence of dental caries.

Iodine deficiency in may result inGoitre



v. Hardness of water

Water hardness has some protective effect on certain heart

diseases.

Statistical association has shown that in areas supplied with soft

water, incidence of certain heart diseases like

degenerative heart disease,arteriosclerosis,

hypertension, etc. is high.

Based on these circumstantial and statistical evidences,softening of drinking water is discouraged.

Commission of the European Communities (CEC) symposium on the

hardness of drinking water and public health has recommended as a

conservative measure that softening of drinking water should not be

vi Diseases due to shortage of water



vi. Diseases due to shortage of water

Certain diseases result from chronic water shortage. Incidence

of scabies and trachoma 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

PURIFICATION OF WATER



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 anytreatment

exceptDisinfection,

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



The water purification plant comprises of one or more

of the following components :

i) Storage

ii) Filtration

iii) Disinfection



i) STORAGEwater drawn from the source is stored in natural or artificial reservoir.

Storage provides natural purification in the form of

Physical,

Chemical, andBiological contents of water :

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

About 90 per cent of the suspended impurities settle

down in 24hours by gravity. The water becomes clearer .

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

(b) Chemical:.

The aerobic bacteria oxidizes the organic matter present in thewater

with the help of dissolved

oxygen.As a result the uantit of free ammonia is reduced

(c) Biological:



(c) Biological:

1. A tremendous drop in bacterial count takes place duringstorage.

2. The pathogens gradually die out.

# It is found that when river water is stored, the totalbacterial count drops by as much as 90 per cent in the first5 -7 days.

This is one of the greatest benefits of storage.

## 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 develo ment of ve etable rowths

(ii) FILTRATION



(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



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.

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



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

** secondly, it provides waiting period of some hours (3 to12 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

2 Sand bed



2. Sand bed

# The most important part of the filter is the sand bed.

The thickness of the sand bed is about 1 metre.

The sand grains are carefully chosen so that they arepreferably rounded and have an “effective diameter”between 0.2 and 0.3 mm.

The sand should be clean and free from clay and organicmatter .

The sand bed is supported by a layer of graded gravel, 30 –

40 cm deep which also prevents the fine grains being carriedinto the draina e i es.

# The sand bed presents a vast surface area; one



# 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

Vital layer:



Vital layer:

When the filter is newly laid, it acts merely as amechanical strainer , and

it cannot truly be considered as“biological” filter .

But very soon, the surface of the sand bed

gets covered with a slimy growth known as“Schmutzdecke”,

vital layer, zoogleal layer or biological layer .

This layer is slimy and gelatinous and consists of threadlike

algae and numerous forms of life including plankton,diatoms and bacteria.

The formation of vital layer is known as “ripening” of thefilter .

It may take several days for the vital layer to form fully



It may take several days for the vital layer to form fully,

and

when fully formed it extends for 2 to 3 cm into the

top portion of the sand bed.

The vital layer is the “heart” of the slow sand filter.

Until the vital layer is fully formed, the first few daysfiltrate is usually run to waste

It removes organic matter,holds back and adsorbs bacteria from the

water and effects

purification

oxidizes ammonia into nitrates ,

3 Under drainage system



3. Under – drainage system

At the bottom of the filter bed is the under – drainage

system.

It consists of porous or perforated pipes,

which serve the dual purpose :

i. providing an outlet for filtered

water , and ii.supporting the filter medium above.

Once the filter bed has been laid, the under – drainage

system cannot be seen.



Filter box: The first 3 elements (e.g., supernatant water,

sand bed and under – drainage system) are contained in

the filter box.

The filter box is an open box, usually rectangular in shape,

from 2.5 to 4 metres deep and is built wholly or partly below

ground.

The walls may be made of stone, brick or cement.

The filter box consists from top to bottom:

Supernatant water 1 to 1.5 metreSand bed 1.2 metre

Gravel support 0.30 metre

Filter bottom 0.16 metre

4. Filter control



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 meter” which measures the bed resistance or

“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 the filter.



Filter cleaning: Normally the filter may run for weeks



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 cleanthe 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 sandlayer to a depth of 1 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.



The advantages of a slow sand filter are:

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 filteredwater

is very high.

• When working ideally, slow sand filters have shown toreduce total bacterial count by 99.9 to 99.99 per cent and

E.coli by 99 to 99.9 per cent.



•In recent years, a mistaken idea has grown that

biological or slow sand filtration is an old fashioned,

outdated method of water treatment which has beencompletely superseded by rapid sand filtration. This is

definitely not the case.

Slow sand filtration is still the chosen method in anumber of highly industrialized cities as well as in urban

areas.

In a number of cities in U.S. and Europe,

slow and filters have recently been constructed.

b) RAPID SAND or MECHANICAL FILTERS



b) RAPID SAND or MECHANICAL FILTERS

In 1885, the first rapid sand filters wereinstalled in the USA.

Rapid sand filters are of two types,the gravity type (e.g. Paterson‟s filter)

and the pressure type (e.g. Candy‟s

filter).Both the types are in use.



The following steps are involved in the purification of water by



g p p yrapid sand filters:

1. Coagulation: The raw water is first treated with a chemicalcoagulant such as alum, the dose of which varies from 5 – 40 mg or

more per litre, depending upon the turbidity, colour, temperature andpH 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 andthorough 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 of paddles 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, whiteflocculent precipitate of aluminium hydroxide.

Thicker the precipitate or flock diameter,

greater the settling velocity.

4. Sedimentation: The coagulated water is now led into



g

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.

At least 95 per cent of the flocculent precipitate needs to

be removed before the water is admitted into the rapid

sand filters. The precipitate or sludge which settles at the

bottom is removed from time to time without disturbing the

operation of the tank.

For proper maintenance, the tanks should be cleaned

regularly , otherwise it may become a breeding ground for

molluscs and sponges.

5. Filtration:

Filter beds:



Filter beds:

Each unit of Filter bed has a surface of about 80 to 90 m2

(about 900 sq. feet).

Sand is the filtering medium. The “effective size” of the sandparticles is between 0.4 – 0.7 mm, the depth of the sand bed is

usually about 1 metre (2 ½ to 3 feet).

Below the sand bed is a layer of graded gravel, 30 to 40 cm (1

– 1 ½ feet) deep. The gravel supports the sand bed and permitsthe filtered water to move freely towards the under – drains.

The depth of the water on the top of the sand bed is 1.0 to

1.5 m (5 – 6 feet).

The under – drains at the bottom of the filter beds collect thefiltered water.

The rate of filtration is 5 – 15 m3 /m2 /hour .







Filtration

As filtration proceeds, the suspended impurities and

bacteria clog the filters. The filters soon clog and begin

to lose their efficiency.

When the “loss of head” approaches 7 – 8 feet,filtration is stopped and the filters are subjected to a

washing process known as “back – washing”.

Back – washing



g

Rapid sand filter needs frequent washing daily or

weekly, depending upon the loss of head.

Washing is accomplished by reversing the flow of water through the sand bed, which is called “back-

washing”.

Back – washing dislodges impurities andcleans up the sand bed.

The washing is stopped when clear sand is visible

and the wash water is sufficiently clear.

The whole process of washing takes about 15

minutes.

In some ra id sand filters com ressed air is used

Advantages



g

The advantages of a rapid sand filter over the slow sand filter

are:

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

2. No preliminary storage is needed3. 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



Comparison between Rapid and Slow sand filtersParameter Slow sand filter Rapid sand

filter 1. Space: Occupies large area Occupies very l i t t le space

2. Rate of Filtration: 0.1 to o.4 m3 / m2 /hour 5 to 15 m3 / m2 /hour

3. Effective size of sand: 0.2 - 0.3 mm 0.4 – 0.7 mm

4. Preliminary treatment: Plain sedimentation Chemical coagulation

and sedimentation

5. Washing / maintenance By scraping the sand bed By back – washing

6. Operation: Less skilled Highly skilled

7. Loss of head allowed: 4 feet 6 – 8 feet

8. Removal of turbidity: Good Good

(III) DISINFECTION



(III) DISINFECTIONIn 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.



EFFECTS

i. Chlorine kills pathogenic bacteria,

but has no effect on spores and viruses

(e.g., polio, viral hepatitis) except in high

doses.

ii. Apart from its germicidal effect,

chlorine has several secondary properties in water

treatment:

* it oxidizes iron, manganese and hydrogen

sulphide;

* it destroys some taste and odour – producing

Mechanism of Action of chlorine:



• When chlorine is added to water ,

there is formation of hydrochloric acid and

hypochlorous acids.

*The HCl is neutralized by 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 thehypochlorite ion.



*Chlorine acts best when the pH of water is around

7.

*When the pH value exceeds 8.5

it is unreliable as a disinfectant

because about 90 per cent of the hypochlorous acid

gets ionized to hypochlorite

ions.

*It is fortunate thatmostly water has pH between 6 – 7.5.



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 free

from turbidity.

Turbidity impedes efficient chlorination

2 S dl



2.Secondly,

the “chlorine demand” of the water should be

estimated, usually by HORROCK‟s test.

“The chlorine demand of water is the difference

between the amount of chlorine added to the water, and

the amount of

residual chlorine remaining at the end of a specific period of

contact

(usually 60 minutes), at a given temperature and pH of the

water ”.

The point at which the chlorine demand of the water

is met is called the “break – oint”



3. Thirdly the contact period. The presence of freeresidual chlorine for a contact period of at least one hour is essential to kill bacteria and viruses.

It should be noted however, that chlorine has no effect onspores, protozoal cysts and helminthic ova, except inhigher doses.

4. the minimum recommended concentration of freechlorine is 0.5 mg / Ltr after one hour .

The free residual chlorine provides a margin of safetyagainst subsequent microbial contamination as may occur during storage and distribution.

5. The correct dose of chlorine is the sum of thechlorine demand of the specific water plus thefree residual chlorine of 0.5 mg / Ltr .

METHOD OF CHLORINATION



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 Iit is cheap,

quick in action, efficient and easy toapply.

Since chlorine gas is an irritant to the eyes and is poisonous, aspecial equipment known as “chlorinating equipment” is requiredto apply chlorine gas to water supplies. Paterson‟s chloronome isone such device for measuring, regulating and administering gaseouschlorine to water supplies.

2 hl i



2. In some water treatment plants, they use chloramines instead of chlorine gas.

Chloramines are loose compounds of chlorine and

ammonia.

They have a less tendency to produce chlorine

taste and

give a more persistent type of residualchlorine.

The greatest drawback of chloramines is that

they have a slower action than chlorine and

therefore they are not being used to any great extent in water

treatment.

3. Perchloron or Hi h Test H ochlorite H.T.H.

BREAK POINT CHLORINATION



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

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 it combines with ammonia

to form

chloramines.This is Combined Residual Chlorine ( CRC )

This is also bactericidal.

The peaking coincides with the oxidation of all organicmatters.

2. Addition of further chlorine, oxidizes ammoniacalcompounds.

3. Addition of next increments of chlorine



# The point at which the chlorine demand is met

and the Free Residual Chlorine starts appearing inthe water , is called “Break point chlorination”.

# The chlorine combined with ammonia is

“combined residual chlorine” (CRC

)and

chlorine released after breakpoint chlorination is

“free residual chlorine” (



Contact period:



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

For optimum disinfection, the presence of free chlorine for a contact period of one hour is essential.

The free chlorine that remains at the end of one hour is called “Free residual chlorine” (i.e. after breakpointchlorination).

The minimum concentration of free residual chlorine for drinking purposes (in drinking 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 thedrinking water is to provide a margin of safety against

further contamination of water which is likely to occur

Applied chlorine dosage:



It is the correct dose of chlorine required to disinfect water, so as

to get free residual chlorine of 0.5 mg per ltr ( 0.5 ppm ).

This is also called as “Marginal chlorination” (simple

chlorination).

It is the sum total of chlorine demand plus free residual chlorineof 0.5 mg per litre

(i.e. the dose required for break – point

chlorination +marginal

chlorination, so as to get FRC of

0.5 mg per litre)

* Super chlorination:



This is a process of chlorination, wherein double theusual dose of chlorine is added to water, so as to getFRC of more than 2 ppm at the end of contact period.

This is resorted to when the water is heavilycontaminated 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 andeyes. Therefore, super – chlorination is followed by dechlorination.

* De chlorination: This is removal of excess of chlorine

and is carried out by addition of reducing substances suchas sulphur dioxide, sodium sulphite, sodium bisulfphite,

sodium thiosulphate or activated carbon. FRC is reduced to

F ff i hl i i



For effective chlorination ,

the pH of the water should be maintained between 7.2and 7.6. Under no circumstances it should be allowed to fall

below 7 or

to exceed 8.

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

hourl intervals until the correct H is obtained.

ORTHOTOLUIDINE (OT) TEST



* Orthotoluidine test detects both

free and combined chlorine inwater. 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 colour varies with theconcentration of chlorine.

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

* 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



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 secondsafter the addition of the reagent to estimate free chlorine in water.

The colour that is produced after a lapse, say 15 – 20 minutes, is dueto 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 chlorineseparately.

## Further , the errors caused by the presence of interferingsubstances such as nitrites,

iron and

manganese all of them produce yellow

colour with o – tolidine, are overcome by the OTA test.



# Chlorine continues to be the most commonly used sterilizing

agent because of its germicidal properties and thecomparatively 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 “halogenatedcompounds”, some of them are either known or

suspected carcinogens.

Other Agents d f Chl i ti



Other Agents used for Chlorination

# As a result, many chlorine alternatives are receivingrenewed interest. This includes bromine,

bromine – chloride,

iodine and

chlorine dioxide – but these do not seem to be a viable alternative

to chlorine at the present time.

Ozone is showing the greatest promise,

and ultra – violet irradiation‟s limited

usefulness as complimentary agents for chlorine in water

disinfection.

a) OZONATION:The process involves passing ozonized air through the



The process involves, passing ozonized air through thewater .

* 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 producesundesirable 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, whereasminutes are required to inactivate them with either chlorine or iodine.

This has prompted many municipalities to consider ozone for otable water treatment.

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



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.

(b) ULTRAVIOLET IRRADIATION:# Germicidal property of UV rays have been recognized for



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

UV irradiation is effective against most microorganism

known to contaminate water supplies includingviruses.

# 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 lampsemitting 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

## The advantages are that the exposure is for short



## The advantages are that the exposure is for short

period,

no foreign matter introduced, no taste and

no odour produced.

Overexposure does not result in any harmful effects.

## The disadvantages are that no residual effect isavailable 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.

(i) Physical methods: These are Boiling,

ozonation andultraviolet irradiation.

(ii) Chemical methods: The different chemical substances employed

for purification of water for domestic use are Chlorine,Iodine andpotassium – permanganate.

(iii) 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 is made up of porcelain in the

P – C filter and of kieselgurh or infusorial earth in the Berkefeld filter and a coat of silver catalyst on



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 colour and

odour )

iii. It inactivates the pathogens by U V treatment in the U V

chamber.

## It has the in built electronic monitoring system

whereby it monitors the quality of purified water and



Reverse Osmosis treatment:



Invention of this technique is a milestone in creation of

drinking water resource.

Reverse osmosis is based on water reverse theory in

nature.

NASA in US first applied this theory in purifying

the astronaut's urine as a resource for drinking

water in space.





In this process, water is purified in 5 stagesf ll



as follows.

Stage 1: 5 u sediment filter .

This removes sand, silt, dust and rust particles

(i.e. removes suspended

impurities)

Stage 2: Activated carbon block filter

Removes chlorine, organic matter, and bleaches

colour

(Removes chemical impurities).

Stage 3: GAC filter (Granular Activated Carbon)

Removes harmful chemicals and

Stage 4: TF (Thin Film) composite membrane



g ( ) p

with 0.0001 mm

pore

(reverse osmosis

membrane).

Removes dissolved salts, organics, germs, bacteria,

virus, compound metals andminerals.

Allows only water molecules to pass

through.

Stage 5: Bacteriostatic silver impregnated activated

carbon.

Prevents rowth of bacteria at the oint of use and



Disinfection of Wells Wells constitute the main source of water supply in rural



Wells constitute the main source of water supply in ruralareas. Since most of the wells are shallow wells, liablefor contamination, need to be disinfected periodically,

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

Wells are best disinfected by bleaching powder.

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 h4The volume is expressed in cu. Metres. I cu metre 1000 litres.

Volume of water in cubic metres X 1000

= X litres

Which is derived fromπr 2 h, where π= 22 / 7 = 3.14

r= radius of well in mtrs.

= half of diametre

= d / 2

r 2= d/2 X d/2 = d2 / 4h= 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 aparticular well can be estimated by using “Horrock‟s

apparatus”.

Horrocks Apparatus

Contents: 6 white cups, each of 200 ml capacity, 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



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 isadded gradually and stirring till the level reaches the white circular mark. It isstirred 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 betested for „bleaching powder estimation‟ up to a cm below the brim.

With the help of the pipette, one drop of stock chlorine solution is

added to first white cup, two drops to second cup, three drops to third cup,and so 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 hour for the action of chlorine in the water (Chlorination).

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

Development of blue color indicates the presence of free residualchlorine.

The intensity of the blue color is directly proportional to the quantity of freeresidual chlorine in the water – suppose the first cup shows distinct bluecolor first, the intensity of color increases subsequently in second, third,

fourth, fifth and sixth cups.

Mechanism: When chlorine solution is added to thewhite cups, it is utilized by the organic and



p , y gammonical 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 setfree, which then acts upon the starch giving rise toblue color. So development of blue color indicates the release or presence of free residual chlorinein that cup.

Suppose blue color is not obtained even in 6th

cup,the first cup is considered as 7th cup and countedsubsequently as 8th, 9th, 10th cup and so on andthe test is continued by adding chlorine solution, 7

drops, 8 drops, so on respectively to all the

The first cup showing distinct blue color is noted



The first cup showing distinct blue color is noted.

That cup number indicates the number of level

spoonfuls of bleaching powder for disinfecting 455liters of water, 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 2gm) 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 WellThe 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



made into a thin paste by adding little water. Then more of water isadded till the bucket is three – fourths full. It is stirred well andallowed to sediment for one minute, so that lime settles down. Thesupernatant 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, belowthe surface of the water and agitated vertically and horizontally, sothat chlorine solution mixes with the well water uniformly.

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

To verify whether water has been properly chlorinated or not,orthotoluidine test is done. If free residual chlorine level is less than0.5 ppm after contact period of one hour, the chlorination procedureshould be repeated.

During the epidemics of water borne diseases, wells are super chlorinated everyday, preferably twice a day, once in the earlymorning and once in the late afternoon in case of heavily used wells.

Continuous Method of ChlorinationTo ensure a constant dose of chlorine to the well – water, under the

circumstances of epidemic of water borne disease the National



circumstances of epidemic of water borne disease, the NationalEnvironmental Engineering Research Institute, Nagpur hasrecommended “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 anopening 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 isput in the inner pot and moistened with water. It is then put inside theouter 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 15-20days, 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



The diseases transmitted through swimming pool water are

conjunctivitis,sinusitis,

otitis – media,

sore throat and

athlete‟s 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,

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 deep end of the pool, passingthrough a purification plant, (where it undergoesclarification, filtration and chlorination) and enters

the pool from the shallow end. The free residualchlorine is maintained at a level of about 0.5 ppm, asrecommended 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.The results of bacteriological examinations of samples of

water taken from the inlet and outlet of the purificationplant, gives an indication of the effectiveness of the

water treatment. The bacteriological quality of water

About 15 - 20 percent of the water of the pool should be

replaced by fresh water every day in order to remove the



replaced by fresh water every day in order to remove thenitrates, albuminoidal ammonia and organic substances derived fromthe 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 orificesshould enter the pool.

Before entry into the pool, the user should empty the bladder andbowel, and clean 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 chlorine solution) then only should enter the pool. Swimming costume should be worn.

Once inside the pool, spitting, blowing of the nose, gargling, urinationis forbidden.

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

HARDNESS OF WATERDefinition

A h d t i hi h d t dil f



A hard water is a one which does not readily formleather with soap (In other words, it is soap destroying

quality of water).CausesThe hardness of water is due to the presence of certain

mineral salts in the water such as bicarbonates,chlorides, sulphates and nitrates of calcium andmagnesium, which form insoluble, sticky precipitate withsoap.

TypesThere are two types of hardness of water. Temporary and

Permanent hardness. Temporary (or carbonate) hardness is due to the

presence of bicarbonates of calcium and magnesium.

Permanent (or non – carbonate) hardness is due to the

MeasurementHardness of the water is measured or estimated by using a

standardized titrant “Ethylene Diamine Tetra Acetic Acid



standardized titrant, Ethylene Diamine Tetra Acetic Acid(EDTA). The results are expressed as mg of CaCO3 per litreof 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 byWHO in its “International Standards of Drinking Water”.

Grading of Hardness of Water

Less than 1 mEq/L (i.e., <50 ppm) – It is soft water.

1 to 3 mEq/L (50 – 150 ppm) – It is moderately hard water.

3 to 6 mEq/L (150 – 300 ppm) – It is hard water.

More than 6 mEq/L (>300 ppm) – It is very hard water.Drinking water should be moderately hard (1-3 mEq/L). The

question of softening the water arises if the hardnessexceeds 3 mEq/L.

The degree of hardness can also be measured by “Clark‟smethod”. According to him, the same four grades areexpressed respectively as <10 percent, 10 – 15 percent, 15-

30 percent and >30 percent.

The hardness of water is not only dependant on the geology of theregion in which the water is found but also by the pollution withsewage and many other wastes. Limestone regions produce water

t i i id bl h d G it d ft t



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

Disadvantages of Hard – water

It causes great wastage of soap

It causes precipitation of carbonates and forms scales in the boilers,leading to greater 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 byprocesses like boiling of water,

addition of lime,

Sodium Carbonate and

Permutit process.

# Permanent hardness (due to chlorides and

sulphates of Ca and Mg) can be removed by lasttwo processes,

i.e. by addition of Sodium carbonate and

by Permutit process ( Base Exchange

A. Removal of temporary hardness



a. Boiling: By boiling the water CO2 gas is driven off,

precipitating the carbonates. The main principle is to removeCO2 gas. Water becomes soft. The reaction is as follows.

Ca (HCO3)2 ---- CaCO3 + CO2 + H2O

Since it is not practicable to boil the water on large scale, next

method is preferred.

b Addition of lime: For example calcium



b. Addition of lime: For example, calcium

hydroxide, when added to water, absorbs

carbon – dioxide and precipitates insolublecalcium carbonates, resulting in softening of

water.

Meanwhile it accomplishes magnesiumreduction.

Ca (OH)2 + Ca (HCO3)2 ---- 2CaCO3 + 2H2OCa (OH)2 + Mg (HCO3)2 ---- MgCO3 + CaCO3 +

2H2O

Ca (OH) + Mg CO ---- CaCO + Mg (OH)

c. Addition of Sodium carbonate (soda ash): Addition



of sodium carbonate not only removes the temporary

hardness but also permanent hardness, as follows.

Na2CO3 + Ca (HCO3)2 ---- 2 NaHCO3 + CaCO3

Na2CO3 + Ca SO4 ---- CaCO3 + Na2SO4

Na2CO3 + CaCl2 ---- CaCO3 + 2NaCl

d. Permutit process: Synonyms are Ionexchange process; base exchange process;zeolite softening In this process both temporary



zeolite softening. In this process both temporaryand permanent hardness are removed. Zeolite is a

mineral consisting of sodium, aluminium and silica.It is also called as sodium permutit (or sodiumzeolite) Na2Z. When this is added to hard water,the Ca and Mg ions exchange with Na2Z andforms Ca and Mg permutit and the water issoftened to zero hardness. The reaction is asfollows:

Ca (HCO3)2 Ca 2NaHCO3

Na2Z + SO

4------------ Z + Na

2SO

4Mg Cl2 Mg 2NaCl

Since the soft water of zero hardness has acorrosive property on pipes, so raw water is again

mixed to the soft water to secure the desired level

Wh ll th Z lit i tili d it b t d



When all the Zeolite is utilized, it can be regenerated

again by passing over a strong solution of sodium

chloride,so that it becomes ready to soften more of water , as

follows.

Ca Ca

2NaCl + Z -----------> Cl2 + Na2Z

Mg Mg

The operation can be made completely automatic.

WATER HARVESTING

CONSERVATION OF WATER RESOURCES



Industrialization, urbanization and deforestation, and

population explosion 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 mainly because of the dependency of irrigation on

tube wells.

Therefore, before it is too late, the underground

water resources should be conserved.The term “conservation” means

* protection of water

resources and *

# Conservation has thus 2 components:



* Protection of Water ResourcesThis can be done by preventing the wastage of water .

This requires extensive education of the public, about theeconomical use of water and to consume minimum requirement for daily use.

** Building up of Sub-soil Water ReservesThis 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 soakingpits or trenches, instead of drains, followed by filtrationusing 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

G d t i t l f ll ti l



Ground water, a precious natural resource, for all practical purposesis considered 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 therole of a public trustee.

A law that ensures that groundwater is treated as publicand

not private property is long overdue.

Thus water will be treated like any other natural resources extractedfrom the ground, like oil, gas and other minerals.

Presently, any one sinking a bore well on his or her territory is nottapping 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

** Laboratory examination report of the water samples.

Field Survey

This includes the collection of data on :i. the nature and source of water supply,

ii. likely sources of water pollution,

iii. mode of filtration,iv. mode of distribution

v. and such other information, as would be relevant

from the sanitary point of view

Laboratory Examination of Water

Samples



p

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 requirementof water are different for different types of analyses:

1. For routine physical, chemical and biologicalexamination,

2 litres sample should be collected in a clean glassbottle, recommended is Winchester Quart bottle.

2. For Bacteriological analysis, 200 cc of water should

be collected in a sterile bottle, sterilized in an

Sampling TechniqueThe sample of water must be thoroughly representative

f th t t b l d



of the water to be analysed.

1. In collecting water from a river, stream or lake, the

sample should be obtained from a mid – stream and not toonear the bank and the surface pollution should be avoided, byplacing 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 thencollected.

# 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

Laboratory Examination of water This includes the following:

1 Physical examination



1. Physical examination

2. Chemical examination

3. Biological examination4. Bacteriological examination

5. Radiological examination, and

6. Virological examination

.1. Physical Examination of Water

This is done to determine the presence of those substances inthe water which affect the physical or aesthetic quality of

water, such as odour, taste, colour and turbidity.

To sum up, from aesthetic point of view (Physical parameters), a clear,non smelling, highly aerated water is fit for human consumption.However, further examinations are necessary for complete

assessment.

2. Chemical Examination of Water The chemical components of water have been grouped into



4 groups, depending upon whether they lead to :

acute health problems or potentially hazardous or

hazardous after prolonged exposure or

have cumulative toxic properties.

i. Toxic substances.

ii. Substances affecting health after prolonged

exposure.

iii. Substances affecting the potability of water.

iv. Chemical indicators of pollution.

i. Toxic substances:



None of these elements are commonly found in natural

waters.

Their presence suggests pollution with mining, smelting

etc.

## It is better to reject the source of water

having toxic substances and search for

alternative safe source than to removetoxic substances from the water , since

methods to remove them will be more cumbersome.

* The toxic substances and their upper permissiblelimit

( / lit )



(mg / litre)

**Other toxic chemical substances are:

Barium, Beryllium, Cobalt, Molybdenum, Thio cyanate, Tin,Uranium, Vanadium, etc.

***Substances affecting health after prolongedexposure:

Fluorides, Nitrates and

Toxic substances Prescribed upper limit ( mg/L)

ppm

Arsenic

Cadmium

Cyanide

Lead

MercurySelenium

0.01

0.003

0.07

0.01

0.0010.01

i. Fluorides:

Exposure to fluoride consumption occurs not only through



Exposure to fluoride consumption occurs not only throughwater but also from food, tooth-paste, air pollution etc.

Fluorides are usually present in higher concentration

in ground waters than surface water.

Its concentration is closely related to dental and skeletalhealth.

Excess fluoride level results in dental and skeletal fluorosis

and decreased level in the water results in dental caries.Therefore, fluoride in water is often called as “A DoubleEdged 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.

–

ii. Nitrates and nitrites:



* Even though these are the naturally occurring ions of the nitrogen cycle, they

are considered as the indicators of pollution in water.

* 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 andnitrite 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 3months of age are most susceptible.

Concentration of nitrate Concentration of nitrite

---------------------------------------------------- + ------------------------------------= < 1Guide line value of nitrate Guide line value of nitrite

l

iii. Polynuclear Aromatic Hydrocarbons (PAH):



These are known to becarcinogenic.

They are benzene,

benz pyrene,

benz pyrelene,benz fluor anthene, etc.

## Since PAH are closely associated with suspended

solids,there fore, effective removal of turbidity will ensure the

removal of

PAH also.

Substances affecting the potability of water

Substances Prescribed upper limit



Substances Prescribed upper limit

Substances affecting the colour 5 units (by colorimeter) or

15 True Colour Units (TCU)

Substances affecting the odor 3 units (by threshold odour test)

Substances affecting the taste Unobjectionable

Optimum - pH 7.5 (range of pH = 7 to 8

Total dissolved solids (affecting

turbidity)

1000 mg / L (<600 mg / L is very safe)

Total hardness 3 mEq/L (1 to 3 mEq / L of CaCO3)

(50 to 150 mg of CaCO3 / L)

Iron 0.3 mg/L

Calcium 75 mg / L.

Magnesium 30 mg / L.

Sulphates 200 mg/L.

Chlorides 200 mg/L.

Zinc 5 mg / L.

Copper 0.05 mg/L.

Manganese 0.05 mg/L.

CHEMICAL INDICATORS OF POLLUTION



1. Chlorides:

All waters contain chlorides, more so in coastal areas,

thus chloride concentration varies from place to

place.

Hence presence of chlorides in water is a permanent

indicator of pollution (with sewage or sea water ).

The standard prescribed limit of chloride for drinking

purpose is 200 mg / litre.

The maximum permissible limit is 600 mg / litre.

2. Free and Saline Ammonia:



Ammonia is a result of decomposed organic matter ,

so its presence indicates organic pollution (sewagecontamination)

of recent origin.

The prescribed upper limit in drinking water is 0.05 ppm (mg /L).

3. Albuminoid Ammonia: (Organic ammonia)

It is a measure of decomposable organic matter

yet to be

oxidized

4. Nitrites:

Its presence indicates water pollution of recent origin



Its presence indicates water pollution of recent origin,

due to putrefaction of organic matter by the action of bacteria.

This should be “Zero” in potable waters.

However , in deep well waters,

nitrites may be found

as a result of reduction of nitrates by ferroussalts.

Therefore, water containing nitrites,

except in case of deep wells, (which contain ironalso),

must be viewed with suspicion.Nitrites are soon converted into nitrates and

therefore nitrites should never be resent in drinkin water

5. Nitrates:

Th th end products of oxidation f i l



These are the end products of oxidation of animal

wastes.

# If nitrates are present in large amount

and ammonia in very small amount

and nitrites being absent,

it indicates , remote contamination

(or of long standing, old contamination).

Nitrates in water should not exceed 1.0 mg/L (1 ppm).

.

6. Oxygen Absorbed:

This indicates the amount of oxygen in the water



This indicates the amount of oxygen in the water,

utilized for oxidizing the organic matter.

This should not exceed 1 mg / L (1 ppm).

However , iron salts,

sulphuretted hydrogen ( H2 S ) and

peat in waters also absorb oxygen.

Therefore, determination of “oxygen absorbed” alone is

not a reliable index of the real amount of pollution present.

It has to be considered along with the concentration of free

ammonia and albuminoid ammonia for assessing the purity of

water

7. Oxygen Dissolved:



This should not be less than 5 mg / L (5 ppm).

Depletion of dissolved oxygen encourages

conversion i.e.,

* reduction of nitrate to nitrite and

* sulphate to sulphide,

thus giving rise to odour

3. Biological Examination of Water



• This includes examination of water under the

microscope for the presence of microscopicsubstances (excluding bacteria) such as algae,

fungi, protozoa, ova, cyst, yeast, rotifers,

crustacea, small worms, insect larvae, etc. which

are all collectively called as “Plankton”.

These are responsible for the production of

objectionable colour, odour and taste in the

water.

4. Bacteriological Examination of Water

# Th b t i l i l i ti f t i



# The bacteriological examination of water is a

very delicate and sensitive test for detecting thecontamination of water by sewage or humanexcreta.

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

which consists of both faecal and non faecalorganisms.

# The typical example of faecal coliform group is

E.coli and non faecal coliform is klebsiellaaerogenes

## The supplementary bacterial indicatorsof faecal contamination are faecal Streptococci

and



and

Clostridiumperfringens.

These indicators also help in assessing theefficiency of water purification processes.

## Because of the difficulty in differentiation

between fecal and non – fecal coliforms ,

for all practical purposes ,

it is assumed that

all coliform group of organisms are of faecal

Reasons for exclusively choosing the coliform organisms (specially E coli) as an indicator of fecal pollutionare:



1. They are present in large numbers in the humanintestine

A person excretes on an average about 200 – 400 billion of these organisms per day.

2. They can be easily detected by cultural method –

as small as one bacteria in 100 ml of water can beisolated.

The methods for detecting other human intestinal organisms

like salmonella, shigella, etc are complicated and timeconsuming.

3. They tend to live longer than pathogens



If the coliform organisms are present in a water

sample, the assumption isthe probable presence of intestinal pathogens.

So consequently the assumption is justified , inthat

if coliform organisms have been eliminated from

water, the pathogens also have disappeared.

# Faecal StreptococciThis is considered as a supplementary indicator of faecal pollution of water because it also regularly occurs in faeces ,

but in much smaller numbers than



but in much smaller numbers thanE.coli.

Therefore, its presence in a water sample is considered as a confirmatory evidence of recent faecal pollution of water .

## Clostridium perfringens

They also occur regularly in faeces but in smaller numbers thanE.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 water suggests that contamination had occurred at some remotetime.

The bacteriological tests carried out are

Interpretation of Results of Disinfected



Interpretation of Results of Disinfected

Water

No coliforms in 100 cc. of water – Excellentwater

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 –

Unsatisfactorywater.

5. Radiological Examination of Water



Water

Pollutionof water

with radioactive materialscauses 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.

WHO has proposed the following standards asacceptable upper limit.

Gross alpha activity = 3 pci / L.

=

6. Virological Examination of Water



Water Enteroviruses, rheoviruses and adenoviruses have

been found in water, entero viruses 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 virusinactivation 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

Primary Secondary

Treatment ( ANAEROBIC ) Treatment ( AEROBIC)

CHLORINE

Grit Primary Biologica Secondary



CHLORINE

Sewage

Effluent

Disposal Activated

Sea OutfallRiver Outfall

Sewage Farm

Sludge

Oxidation Pond

Oxidation Ditches

Scree

n

Grit

Chamb

er

Primary

Sedimentation

Tank ( 6 - 8

Hrs )

g

l

Treatmen

t

y

Sedimentation

Tank ( 2 –3

Hrs)

MethaneGas

Sludge

Digeste

r (Incubated

) Temp,

pH

Sludge Drying Beds



Alternate

Sludge to

digester Excess

sludge to

digester

or

Excess sludge Return and excess sludge

thickener

Primary

Sedimentati

on ( 6-8 Hrs )

Aeration

Tank

6 – 8 hours‟

Detention

Final

setting Tank

( 2-3 Hrs )

R e t u r n

s l u d g e

2 0 – 3

0 %

Activated sludge

process







Trickling Filter



AIR

and

VENTILATION



Air and VentilationINTRODUCTION

Air constitutes the immediate physical environment



Air constitutes the immediate physical environment.

Life would not have existed without air .

## The public health importance of air is that

it is necessary for breathing 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 carbon dioxide (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

substances such as dust,

bacteria,

spores,

gases in excessiveconcentration,

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 dueto bacterial pollution.

1. The physical changes are:

i. Rise in the temperature due to release of bodyheat.

ii. Rise in the relative humidity due to expirationand perspiration.

iii. Decrease in the air movement.

iv. Occurrence of unpleasant odours arising from

expiration perspiration bad oral hygiene

2. The chemical changes are:



g

i. Increase in the CO2 concentrationii. Decrease in the O2 concentration.

The vitiated air affects the health,

comfort and

efficiency of

occupants, mainly due to physical changes in

the air .

3. Bacterial pollution by the infected droplets.

EFFECTS OF VITIATED AIRThey are divided into acute and chronic.



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

Death may occur in extreme cases.

## Chronic effects are anemia, debility, digestivedisturbances, nutritional and metabolic disorders,lowered vitality and decreased resistance to

infections.

**The working efficiency is decreased and

**the

output of the work falls.

INDICATORS OF THERMAL COMFORT

i. Air Temperature



i. Air Temperature

This alone is not adequate indicator.ii. Air Temperature and Humidity

This is a better indicator than air temperature alonebut still this is unsatisfactory.

iii. Air Temperature, Humidity and Air movementThese three together is called “Cooling Power” of the air,

which can be measured by a device called “Kata thermometer ”.

A dry kata reading of 6 and above and

a wet kata reading of 20 and above are regarded as anindex of thermal comfort.

KATA THERMOMETER



• Effective Temperature (ET)



It is the combined effect of

- air temperature,

- humidity and

- air movement (cooling power)

on the sensation of warmth or cold felt by the

human body.

But this does not include the effect of radiation

from the surrounding structures.

**Corrected Effected Temperature (CET)

I thi i d i t d f d b lb di f th



In this index, instead of dry bulb reading of the

temperature, the reading of Globe thermometer isemployed, which allows the radiant heat,

thereby all the 4 factors, namely

- air temperature,

- humidity,- air movement and

- radiant heat, are taken into

consideration.

. The index obtained from the revised nomogram is

termed as “Corrected Effective Temperature”, which

represents the impact of all the four meteorological



Comfort Zone

It is the range of corrected effective temperature in



It is the range of corrected effective temperature in

which the individual or the worker in an industry, feels

comfortable.

The criteria of comfort zone are

* Corrected Effective Temperature – 25-270C (77-

800F)

* Dry kata – 6 and above

* Wet kata – 20 and above* Relative Humidity – 30-65 percent

•Predicted Four hour Sweat Rate (P4SR) – 1-3 litres

METEOROLOGY

INTRODUCTION



INTRODUCTION

The components of meteorological environmentare:

Atmospheric pressure

Air temperature

Humidity

Air movement (Air velocity)

(Direction and speed of the

wind)

ATMOSPHERIC PRESSUREThe instrument used to measure atmospheric

pressure is called “Barometer”



pressure is called Barometer

“Kew Pattern” Station barometer is widely used.Others are Fortin‟s Barometer ,

Aneroid Barometer and

Barograph.Effects on Health

The influence of atmospheric pressure on health

is considered under two headings. Effects of diminished atmospheric pressure.

Effects of increased atmospheric pressure.





# 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. Chilblainsii. Frost Bite

iii. Trench Foot

### Effects of solar radiation

i. On Skin

ii. On Eyes

Effects of Increased Atmospheric Pressure

As we descend from sea level the atmospheric pressure



As we descend from sea level the atmospheric pressure

increases at the rate of one atmospheric pressure for every 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. Caisson‟s disease

AIR TEMPERATUREMeasurement Air temperature is recorded by using the following thermometers in

Fahrenheit scale / centigrade scale.

D b lb th t Thi i di i l th t



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

placed in Stevenson‟s screen to protect from, direct sun andrain, at a height of about 1.5 meters above the ground level. Itrecords the temperature of the air.

b. Wet bulb thermometer : It is similar to dry bulb thermometer, exceptthat 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 columncomes down. Thus the wet bulb thermometer shows a lower temperature reading in response to the heat lost by wet cloththrough evaporation, than the dry bulb thermometer.

Drier the air, lower the wet bulb reading.

If the wet and dry bulb thermometers record the same identicaltemperature, it means the air is completely saturated withmoisture, which is rare or never occurs.

The difference between the dry and wet bulb thermometers

increases with increasing dryness of air and vice versa



STEVENSON’S SCREEN



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



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

mercury thermometer is inserted such that the bulb is in thecenter of the globe.

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

The globe thermometer records a higher temperature than the

ordinary dry bulb thermometer because it is affected by boththe air temperature and the radiant heat of the surroundings.

Therefore, the difference between the reading of theglobe thermometer and the ordinary dry bulb

thermometer is a measure of the radiant heat.

i. The globe thermometer is also influenced by thevelocity of the air movement.



GLOBE THERMOMETER

HUMIDITY Atmospheric humidity means the moisture content of theair , which in turn depends upon the air temperature.

Lower the temperature of air, higher the moisture content



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

The temperature at which the moisture precipitates is called “Dewpoint”.

Humidity may be expressed as absolute humidity or relativehumidity.

Absolute HumidityIt is the actual amount of moisture (or water vapor) in anunit volume of air.

It is expressed as grams per cubic meter of air.

Relative Humidity (RH)

It is the percentage of moisture present in the air,complete saturation being taken as 100. Greater therelative humidity, the nearer the air to saturation.



Measurement The humidity of the air can be measured by an

instrument called “Hygrometer”, of which there



instrument called Hygrometer , of which there

are 2 kinds – namely Direct and Indirecthygrometers.

* Direct Hygrometers are Danniell‟s

Hygrometer,Regnault‟s Hygrometer and

Dine‟s Hygrometer .

**Indirect Hygrometers are- dry and wet bulb hygrometers,

- Sling psychrometer and



Sling Psychrometer This consists of 2 mercury thermometers dry and wet,

the latter bulb is covered with a thin muslin cloth and keptmoist 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 theinstrument is rotated or whirled rapidly, at the rate of 4revolutions per second, so as to obtain a desirable air speed of 5 meters per second, for about 15 seconds,stopped and wet – bulb reading is noted.

This is repeated several times till the two successivewet bulb readings are identical, showing that it hasreached its lowest temperature.

Now the dry bulb reading is also taken, which is the true

temperature of the air



SLING PSYCHROMETER



AIR MOVEMENT



AIR MOVEMENT

The best instrument used to record the velocity of

air and also the pressure of the wind is

Robinson‟s Wind Anemometer.



ANEMOMETER



WIND DIRECTION



RAIN GAUZE

AIR POLLUTION

Air pollution is a constant and menacing problem



Air pollution is a constant and menacing problem

throughout the world, due to man‟s ownactivities like industrialization and

urbanization.

It is increasing continuously during the past

few decades.

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

Air PollutantsThese may be physical, chemical or

biological



biological.

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

Although the Earth‟s atmosphere extends to several kmabove the surface, it is only the first 30 km that holdthe major portion of the atmospheric gases.

Man is concerned only with the first 8 – 10 km of theatmosphere



atmosphere.

FACTORS INFLUENCING Air Pollution

# Degree of air pollution is influenced bytopography, i.e. atmospherictemperature,

humidity,

atmospheric pressure and

air movement.

# Pollutants are also affected by

sunlight and

Sun Light

The U-V rays of the sun act on



The U-V rays of the sun act on

the oxides of nitrogen and

other hydrocarbons

and form photo

oxidants,

which are irritant to

conjunctiva,

nose,throat and

respiratory mucous membrane

Air Movement



Normally the air near the surface of the earth is

warmer than the air higher up.

So warmer air, being lighter, moves up, expands and

becomes cool.

Thus the pollution is diluted and dispersed,

while the air of the upper layer being cool and heavy,

comes down (turbulent flow).

Temperature Inversion

U d ti l diti i d ll



Under exceptional conditions, as in deep valleys,

the temperature gradient is reversed, i.e.

the air near the surface of the earth absorbs

infrared radiation and remains cool while upper layers are warm,

hence, the normal upward movement of air is

impeded.

Th P ll t t t d d i l k d

If Fog is present along with temperatureinversion,

water vapor condenses around the smoke particles and



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 of respiratory illness,suffocation and death.

Highly susceptible population groups are

young children,elderly people and

those suffering from lung diseases and

heart diseases.

The famous episodes of acute illness and deaths due to generalatmospheric pollution by temperature inversion are :

Muse valley disaster (Belgium) in Dec. 1930, lasted for 5 days,

killing 63 people and many cattle



killing 63 people and many cattle.

Donora (Pensyl – vania) disaster in 1948 took the life of 20

people and hundreds became ill.

London disaster in 1952 (England) was the deadliest smog history, due to domestic coal burning, when more than 40,000

people died.

Bhopal gas tragedy in India in 1984 killed thousands of people and it was due to leakage of Methyl Iso Cyanide gas ,

Phosgene, &

Carbon mono oxide in Uni Carbide

industry, an example of toxic pollution of air and







ii. Global warming:It is a phenomenon occurring in the troposphere.

Normally, the atmospheric gases have a “green-houseff t” i lik th l f h



effect”, i.e. like the glass of a green – house,

allow light and warmth to reach the earth

but they do not allow warmth to be lost,

thus maintaining life on earth

## In air pollution,

there is rise in gases like carbon dioxide,

methane and chlorofluorocarbons and accumulationof ozone, they elevate the global temperature

thus resulting in global warming and

ff ti th t

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



## Global Warming has resulted in following effects:

Increase in the dryness of the climate

Reduction in the world food productionMelting of polar ice caps

Rise in sea level and also resulting in floods

Smog formation

Increased incidence of skin cancer and

cataract

iii. Effects of depleted ozone shield:## Normally ozone layer of the earth, filters the harmful U-

V rays of the sun and prevents them from reaching thesurface of the earth



surface of the earth.

## Because of air pollution, ozone layer begins tothin out and results in the following effects :

* Inhibition of photosynthesis, (due to burning of

leaves, retardation of growth of plants, fall in the cropyield, ageing of plants etc, all due to air pollution).

* Disruption of marine food chain

* Impairment of human immune mechanisms,

predisposing for infections* Ocular damage (cataract)

* Skin Cancers (melanotic and non melanotic)

* U-V rays also cause damage of small forms of life

h l kt ll i d it if i il

iv. On animals: Cattle become weak andcachexic, 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 and stone (like

painting, carvings).

Repair costs millions of rupees.

(thus time, money and energy are

INDICATORS of Air PollutionFollowing indicators are employed for monitoring of air pollution.

i. Sulphur –dioxide index: This is estimated by lead –



p y

peroxide device.

ii. Smoke index (soiling index): A known volume of air

is filtered through a disc of filter paper. The

discoloration produced is measured against thestandards in photo electric meter .

Result is expressed as Coh units / 1000 linear feet

of air. ( Coefficient of Haze )

iii. Coefficient of haze: it is the amount of smoke or

other aerosol per cubic metre of air.

iv. Suspended particles (measurement of dust and

grit concentration):



The amount of dust particle present in the given volumeof air is measured by using an instrument, “Midget

impinger ” and is expressed in mgm per cubic meter of

air.

v. Other parameters are lead,

carbon monoxide,

nitrogen dioxide,oxidants.

Air pollution index: it is an arbitrary index,

considering one or more pollutants as a



measure of severity of pollution.

Example: (Employed in USA)

10 times SO2 concentration, plustwice CO concentration plus

twice the coefficient of haze.

It is considered as an alarming when this

value becomes more than 50.



c. Containment measures: such as



- * Controlling the production of dust by wet method.- * Prevention of the escape of dust into the

atmosphere by using enclosure

hood,- exhaust pipes for removal, and also

- * Increasing the height of smoke vent, etc.

-

.

ii. Legislations measures: To control air



ii. Legislations measures: To control air

pollution, Govt. of India has enacted some Acts,

Prevention and control of Air

Pollution Act,

Smoke nuisance Act, etc

iii. General measures:* Control of traffic by construction of by-passroads.

**Maintenance of vehicles by periodical servicing,



mixing of petrol and oil in proper proportions,use of unleaded petrol to the vehicles,

fitting the catalytic converter to the exhaustspipes of four wheelers, which convert the harmful

gas into harmless gas.***Establishment of “Green-belts”, i.e. growing

plants and trees between the industries and theresidential 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 andcontrol of air pollution.

*****P l ti t bili ti



VENTILATION



Ventilation is not only the replacement of vitiatedair (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.



Standards of Ventilation

# Fresh Air SupplyDe Chaumont has recommended 3000 cu ft of fresh air per hour per person,

based on a point that a person entering a room from outside should not



based on a point that a person entering a room from outside should not

perceive any smell or stuffiness.The stuffiness occurs in a room when the CO2 concentration exceeds 0.02 per

cent.

The amount of fresh air that should be delivered per hour to an occupied room,

can be calculated by the formula,

d = e/p, where d = amount of fresh air to be delivered to a room.e = CO2 exhaled per hour per person (A person at rest gives off 0.6 cu.ft of CO2

per hour)

p = limit of respiratory CO2 per cu. Foot of air (i.e. 0.02 cu.ft per 100 cu.ft of air

i.e. 0.0002 in one cu. Ft)

Therefore d = 0.6 / 0.0002= 3000 is the number of cu. feet of air required per person per hour, CO2 being

taken as an indicator.

A child requires about 200 cu. Feet of air per hour.

However, this standard of ventilation is no longer followed.



Systems of VentilationMainly there are two systems of ventilation, namely

Natural and Artificial, depending upon the motivepower, which originates them.



A. Natural ventilation: This depends upon 3factors.

i. Perflation and aspiration of the wind.

ii. Difference of temperatureiii. Diffusion of gases.

Natural ventilation helps considerably, if the buildings

are constructed with sufficient open space aroundand by having large number of windows, preferablyopening direct into the outside air. Cross ventilationmeans perflation between windows and other openings placed opposite to each other. Naturally

“



ii. Effects of difference of temperature:

Air always flows from high density to low density.



# Out side cool air is of high density, rushes in throughevery opening of the room (or through the inlets placedat 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 velocityof the incoming air, until the temperature of both outside andinside air becomes equal.

Since the incoming air gets warmed up, a constant current ismaintained. 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 keepthe inside air warm.

iii. Diffusion of gases:

this means passing of the air through the smallest



openings or spaces such as cracks andcrevices.

This is a very slow process and is very small.

As a ventilating agent, it is of little value.

B. Artificial ventilation: (Mechanical ventilation)

These are of the four types.

i. Vacuum system

ii. Plenum system



y

iii. Balanced system andiv. Air conditioning.

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

In this system foul, vitiated air is extracted or exhausted to theoutside by using exhaust fans, operated electrically, sothat vacuum is created and fresh air enters in and fill itsplace.

They are usually provided in large halls, auditorium, cinema

halls and are fixed near the roof, because vitiated air iswarmer and moves up.

Ventilation may be controlled by adjusting the speed of thefans. They are also employed in the industries to removedusts, fumes and other contaminants at their source.

ii. Plenum system (Propeller system):

In this type, fresh air is pushed or propelled or blown into the room

by



bycentrifugal fans or high pressure fans

.

This creates a positive pressure and displaces the vitiated air.

iii. Balanced system:

In this type, there is combination of both exhaust system

and plenum systems of ventilation. This is used in large halls

with extensive sitting capacity. This is also used in air – conditioning system.

iv. Air conditioning:

In this system, the outer air is “conditioned” or “controlled” with reference to physical and chemicalconditions such as cleaning (free from pathogens



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 ameasured rate and volume of flow without producing

draught and exhausted through ducts.

These are being increasingly used in operationtheatres of the hospitals, in hotels, restaurants,

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

When the temperature difference between theoutside air and air conditioned room is very

large, “transition rooms” are provided, so



as to prevent sudden exposure to high or lowtemperature.

The advantages of artificial methods of ventilationare the constancy and the facility with which

fresh air is supplied under all conditions,

whereas natural ones though less costly are notunder human control being subject to

atmospheric conditions.



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

Train, Aero plane engine – about 120 dB

Threshold of pain – about 140 dB

Jet plane – about 150 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 – indicateswhether 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

HAZARDS OF NOISE POLLUTION

Grouped into two groups –



Auditory and Non auditory.

Auditory Effectsa. Quantifiable ( Measueable )

i. Threshold shift (temporary, later on permanent).

ii. Auditory fatigue (associated with whistling and



buzzing).iii. Deafness (temporary or permanent)

(occupational deafness)

# The temporary hearing loss occurs in frequency

range between 4,000 to 6,000 Hz.# Repeated or continuous exposure to the noise

around 100 dB may result in permanent deafness.

# Exposure to noise above 160 dB may cause

rupture of tympanic membrane and cause

permanent deafness.

Non auditory Effects

Interference with speech communication.

Annoyance (such as irritability, short temperedness,impatience quarreling and decreased production in the



impatience, quarreling and decreased production in theindustries)

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.

PREVENTION AND CONTROL

1. Control of Noise at Source



By the following measures in the industries:

* Planned maintenance of the machines.

* Regulation of the speed of the machines

* Use of resilient materials (such as rubber betweenimpacting surfaces)

* Enclosure of the machines* Sound proofing of walls

* Replacement of equipment, insertion of silencer.

2. Increasing the DistanceThis is possible, if it is in the open field.If it is a closed room, it is made sound – proof by lining the walls

with adsorbent materials. Otherwise the reverberating sound will



add to the direct sound.

3. Reduction of Exposure Time

4. By Job Rotation.

5. Acoustic Barriers

They are of two types:

# Around the source: Like insulation, damping## By the receiver . Use of personnel protective devices like

ear muffs,



7. Health education of the people about the

necessity of reducing the harmful noise such as

prohibition of blowing of horns near the hospitals,



schools, officers, etc. about the use of horns that arefree from shrill and inharmonic overtones,

enforcement of speed limit of vehicles, about

restriction of use of loud – speakers, etc.

Thus, public are educated through all available medias.



LIGHT

LIGHT

INTRODUCTION



Light constitutes an important physical

environment of human beings. It is also a form

and a source of energy. Without light, living will

not be comfortable. It is essential for vision.Light may be from natural source or artificial

source.

Natural source of light is the Sun.

The visible rays of the sunlight constitutesthe solar spectrum “VIBGYOR”,

which can be seen in the rainbow.



The sun rays beyond the spectrum are

invisible.

The rays beyond the violet end are Ultraviolet rays

and the rays beyond the red end are Infra – red rays.

Both have got therapeutic uses.

## For efficient working ,

following “Day light factors” are essential :



i. Sufficient illumination of 15-20 foot candles

ii. Uniform distribution in the working place

iii. Absence of glare (i.e. Glare is excessive

contrast, e.g. headlight of a vehicle at night. Thesame light during day time does not cause glarebecause of absence of contrast)

iv. Absence of sharp – shadows

v. Steadiness of source of light

vi. White color of the light

vii.Contrast surroundings.

MEASUREMENT OF LIGHT

The luminous intensity or power of artificial light is

measured by the standard “Candle”.



yThe amount of light given off by the burning of a sperm wax

candle burning 120 grains per hour is called power.

The illumination received from one candle at a distance of 1 foot,

is known as 1 ft. candle.

The illumination is measured by an instrument called

photometer .

A minimum of at least 6 ft. candle illumination is

required

for clear visibility for performance of work.

The light is also measured by other parameterssuch as:



Luminous flux (flow of light), expressed inlumens

Illumination (amount of light reaching asurface) expressed as lux per unit area

Luminance (brightness i.e. amount of lightreflected from a surface) expressed as lamberts.

Natural Lighting

This is obtained not only from the sky but alsofrom reflection.

Natural lighting depends upon the time of the day,season, weather and atmospheric pollution.

Measures to Improve Natural Lighting

The buildings should be directed towards North and

South, so that there will be uniform lighting from



morning to evening.

Construction of windows must be properly planned.

Atall narrow window gives greater penetration of light and a broad window gives greater diffusion

of light.

Inside the rooms, the ceiling should be white,the upper portion of walls should be light coloured and

lower portion should be slightly dark colored

Artificial Lighting

Electric light is the best method of providingartificial illumination. There is no combustion, nor



there is any reduction in the oxygen content of atmosphere. It gives good, steady and bright light.

The different types of electric lights are :

# Filament lamps (Incandescent lamps):

In this type, the tungsten filament is heated and lightis emitted.

Only 5 percent of the current is available for lightingand remaining 95 percent is expended as heat.

## Fluorescent lamps (Vapour lamps): Differenttypes are :

Neon filled sodium discharge lamp: This givesyellow light.



Mercury vapour lamp: The lamp consists of aglass – tube, filled with mercury vapor and anelectrode fitted at each end. The inside of thetube is coated with flurorescent chemicals,which absorbs U V radiation and remits theradiation in the visible range.

Cold cathode neon lamps: they are used for

decorative purposes. Shadow less lights: They are specially

necessary in operation theatres.

Other Sources of Artificial Light



Gas light: In this type, there is burning of thecoal gas in an incandescent burner having a

mantle.

The light is steady and bright but it producestoo much heat and emits disagreeable smell.

Gas burner : Oil lamps, candle and

acetylene gas.

.

HEALTH HAZARDS

# Excessive bright light or glare results in

glaring,



blurring of vision,

discomfort

accidents

## Poor lighting results in

nystagmus,headache,

accidents,visual strain, etc.

### Biological Effects

The observation that

day light causes degradation of bilirubin is



employed as a therapeutic measure among prematurenewborns with physiological jaundice.

Other biological effects of light are

stimulation of melanin synthesis

and

synthesis of vitamin D in the skin

O



RADIATION

CONTENTS1. Types of Radiation

a. Non ionizing

b I i i El t ti



b. Ionizing – Electro magnetic

- Corpuscular

2. Sources of Ionizing Radiation

3. Health Hazards of Ionizing Radiation

4. Factors Influencing Radiation Hazards

5. Epidemiological Factors6. Prevention & Control

Radiation INTRODUCTION

R di ti l tit t i t t h i l



Radiation also constitutes an important physicalenvironment.

Radiation is defined as a form of energy, emitted from

a matter, in all directions, in the form of waves,

each wave carrying a quantum of energy or emitted inthe form of fast moving sub-atomic particles or

nucleotides.

Such energy is emitted from a matter as a result of electrical excitement or internal changes.

The energy that is emitted depends upon the wave

length

Shorter the wave – length,

t i it l d i



greater is its energy value and vice – versa.

Wave lengths are expressed as α.

Radiations are grouped into two groups –

namely

lonising and

Non ionising radiations,

depending upon the ability to penetrate the

NON IONISING RADIATIONS

These do not penetrate the body tissues ,

b t th b b d b th fi i l ti lik



but they are absorbed by the superficial tissues likeskin and eyes.Depending upon their increasing wave length (or decreasing frequency) they are classified as

follows: RaysWavelengths (in milli microns or

nanometer

1 nm = 1 / 1000

mm)

•Ultraviolet rays

•Visible light

•Infrared rays

•Microwaves

•Radiofrequency waves•Laser radiations

20 – 400 nm

400 – 700 nm

700 – 1000 nm (=1mm)

1 mm – 1 metre

1 metre – 1 km

Ultraviolet Rays Sources

i. Natural source is Sun.

A th i f S



As they are coming from Sun,maximum rays are absorbed by ozone .

Effects are more at higher altitudes than at sealevel and in summer than in rainydays.

ii. Artificial sources are many, such asmercury vapor tubes,

carbon – arc,

High –Risk Persons

i. For natural sources, are

f



farmers,shepherd,

sailors,

road builders,

fishermen and

those skating on snow.

ii. For artificial sources, areelectric welders,

cinema projector

Hazards

Since the UV rays do not penetrate the tissues but are

b b d th ff t i il th ki d



absorbed, the effects are primarily on the skin andeyes.

From the natural sources, the effects are more on the

skin & from the artificial sources, the effects are more on

the eyes.

The effect depends upon the duration of exposure,intensity of exposure

and

the individual

On the Skini. Short term effects: These are immediate

effects as follows:

a.Melanin pigment which is normally present



in malphigian layer migrates upwards intothe corneum causing darkening of the skin (Suntan)

b.Histamine is released resulting inerythema, oedema, blisters and even ulcers depending upon the quantity released.

c.Thickening of all layers of epidemics, aprotective mechanism

d.Synthesis of vitamin D takes place andrickets is prevented (the last two are useful

ii. Long – term effects:

These are delayed effects, as follows:

D ti f ki



Degeneration of skin

Decrease in elasticity

Cancer of the skin (squamous cell carcinoma,

rodent ulcer).

For all these effects, black individuals are less

susceptible than white persons.

On the Eyes

From the natural source, the effects are:

S bli d th



Snow – blindness: common among those

skating on the snow, because UV rays reflect

from the snow causing keratitis.

Burns – on the inside of the nose, commonamong skaters, because of the reflection from

the snow.

Eclipse blindness – due to direct gazing at thesun, specially on the solar eclipse.

From the artificial sources, the effects are:

Conjunctivitis, keratitis, photophobia

Flash burns (Welder‟s flash) from arc welding

Corneal ulcer (in later stages)



Corneal ulcer (in later stages).

Prevention

Education of workers about hazards and prevention

Personal protection by clothing, goggles, visors, etc.

Regulation of exposures.

Visible LightNatural source: Sun

Artificial sources: Bulbs, candles, neon – tubelights, oil lamps, etc.



## Hazards

Poor lighting: Result in eye strain, visual

fatigue, accidents, nystagmus (in the mines)

Bright light: Direct light results in glaring,blurring of vision and accidents.

Direct light from the sun on the eyes results in

scotoma, (a blind – spot),conjunctivitis, keratitis andphotophobia.

Infrared RaysNatural source: Sun

Artificial Sources: Fire, molten metal,

red – hot objects, etc.



High risk groups: Blast – furnace workers,

black – smith,

kiln workers, and stokers, etc.

## Hazards

On the skin, it causes flushing, burns and

even ulcers.

On the eyes, it may cause cataract.

Microwaves

These are used in radar communications in

ships and aeroplanes



ships and aeroplanes.

Prolonged exposure may result in cataract and

microwave sickness characterized by

headache, giddiness, loss of memory,

fatigue, etc.

Radiofrequency Waves

These are used for wireless transmission.They are also employed in radios, television stations

and from satellites



and from satellites.

They are not absorbed and

therefore they are harmless to the body.

Laser Radiations(LASER – Light Amplification of Stimulated Emission of

Radiation)

Laser is an instrument which generates extremely intense



Laser is an instrument, which generates extremely intense,monochromatic,

coherent light,

passing in an unidirectional

beam,

carrying

intense heat.

Skin and eyes are susceptible.

It causes thermal burns of the skin and corneal damage,

opacification of the lens and

IONISING RADIATIONSThese are capable of penetrating the body tissues, deposit the

energy and cause destruction of the tissues.

Such ionizing radiations are emitted from the atomic particles.

An atom is the smallest unit of an element, which cannot be

split further



split further.Such an atom has definite proportion of electrons and protonsand is then said to be a stable atom.

Such a stable atom, when subjected to the electrical excitementor fission or bombardment, the proportion of electrons and

protons become dissimilar and is said to have becomeunstable.

Such an unstable atom tries to attain stability.

In such an attempt, it emits energy in the form of rays andparticles, carrying intense energy, which have got ability to

penetrate the body tissues, deposit the energy resulting indestruction of the tissues.

This is called “Ionisation” or Ionising radiation”.

“At-risk” group are person working in

radiotherapy,

radiology



radiology,

nuclear medicine and

soldiers exposed to

nuclear explosions inthe war .

TYPE of ENERGY EMITTED

Depending upon the type of the energy emitted from an



Depending upon the type of the energy emitted from anunstable atom, whether it is in the form of waves or

subatomic particles, the ionizing radiations are of two

types:

a. Electromagnetic radiations (or photon

radiations)

b. Corpuscular radiations (or particulate

radiations).

a. Electromagnetic RadiationsIn this type, the energy is emitted in the form of very short

frequency waves, each wave length measuring one crorthof a mm, carrying intense energy. These are not liberated incontinuous waves but in discrete units called quanta. For examples X-rays and gamma rays



examples, X-rays and gamma rays.

X-rays are artificially produced, emitted from intact atoms,they are of lower intensity, capable of penetrating about 25cm into the tissues, used for diagnostic purpose.

Gamma rays (y-rays) are naturally produced, emittedspontaneously during disintegration by the atom, whichare more intense than X-rays and are capable of penetrating about 50 cm into the tissues,

used for sterilization of plastic materials,IUDs, catgut, sutures,

bandages, etc.However, electromagnetic, radiations are thousand times weaker than cor uscular radiations.

b. Corpuscular Radiations (ParticulateRadiations)

They are made up of sub atomic particles or



They are made up of sub-atomic particles or nucleotides.

Depending upon whether they are positively

charged or negatively charged or not chargedat all,

they are called as Alpha(α) particles,

Beta (β) particles andNeutrons respectively.

Alpha particles: They are made up of heliumnuclei, consisting of 2 protons and 2 neutrons.

They are positively charged.

They are the most intense form of ionizing radiations



They are the most intense form of ionizing radiations

They do not have the penetrating capacity

(hardly 0.05 mm) unlike that of electromagnetic

radiationsbut they are hazardous when inhaled,

ingested or implanted sub-cutaneously.

They are emitted spontaneously from an unstableradioactive elements such as uranium, thorium,

radium, plutonium.

Alpha particles are nearly

Beta particles: They are negativelycharged, consisting of electrons.

They have more penetrating capacity



They have more penetrating capacitythan alpha particles, i.e. 0.06 to 4 mm,

but the intensity of ionization is 1/100th

of alpha – particles.

They are also emitted spontaneously from the

radioactive elements.

Neutrons: they are neutrally charged, i.e.

uncharged.

Th d t t di tl



They do not act directly.

They impart energy to other atoms,

which then become unstable andrelease beta- particles causing ionization.

The period after-which the emitted power of

an atom is reduced to half , is called “Half-

life”



life .

Longer the half-life of an atom,

greater is its health hazard.

Some of the other ionizing radiations are photon

rays, meson rays. Proton-anti-proton collisions,

neutron-antineutron collisions, etc.

Radiation UnitsThe potency of radiation is measured in three ways:

Roentgen: That is the amount of energy absorbed in 1 mlof air.

Rad (Radiation absorbed dose): That is the amount of

energy absorbed by 1 gm of tissue



energy absorbed by 1 gm of tissue. Rem: (Roentgen equivalent man): That is the product of

rad and the modifying factors.

These radiation units are now being replaced by the

new international system of units,namely

Coulomb per kg – replacing roentgen.

Gray (Gy) – replacing Rad (1 Gy = 100 rads)

Joule per Kg (Sievert) – replacing Rem (1 Si = 100rems).

“Curie” is the unit of radioactive disintegrations per second.-

Sources of ionizing radiations: These are Natural and

Artificial A. Natural sources: These may be external or internal

a. External sources are Sun, Atmosphere and Earth.

i. Sun: The radiations coming from the sun are called

“Cosmic radiations” (Cosmos = sun) They originatefrom the s n the are positi el charged protons Their



Cosmic radiations . (Cosmos sun). They originatefrom the sun. they are positively charged protons. Their penetrating capacity is minimal. As they pass throughthe atmosphere, they are weakened. Their effect is 35m. rads per year. Maximum permissible limit is 5 rads

per year.ii. Atmosphere: These are called atmospheric or

environmental radiations. They originate from theatmospheric gases like radon and thoron. They havean impact of 2 m. rads per year. Their effect is minimal,Environmental pollution with these gases occur through the processes like processing of uraniumand thorium ores, operation of nuclear reactors, testingof nuclear weapons, etc.

iii. Earth: These are called “Terrestrial

radiations”. They originate from the radioactive

substances such as ores of radium, actinium,

uranium and thorium present in the earth‟s crust

(soil) or rocks and buildings Their effect is 50



(soil) or rocks and buildings. Their effect is 50m. rads per year. But in Kerala, it is about

2000 m.rads per year because of the

monozoite sand.

b. Internal sources:

They originate from the radioactive elements stored in

the body tissues such as radioactive isotopes K40 I131



the body tissues, such as radioactive isotopes K , I ,C14, Sr 90, Cs137, etc.

These internal radiations inflict about 25 m rads per

year . The last two, Sr 90 and Cs137 remain active for many years.

B. Artificial sources:

these are man-made sources.

These radiations are used for medical purposes



These radiations are used for medical purposessuch as X-rays, radioactive isotopes and

also for non – medical purpose

such as television and watch industries, agriculture, atomic power generation, nuclear explosions

(warfare), etc.

The radiations from the sources of non – medical

purposes are too small.

Health hazards of ionizing radiations:These are Acute and Chronic effects

A. Acute effects: These occur when the body is exposed to heavy (1Gy) or very heavy (1 to 9 Gy) doses of radiation for short period of time. This isusually accidental. The condition is called “Acute radiation syndrome”,

which occurs in the following four stages.



g g

i. Prodromal stage: Characterised by anorexia, nausea, vomiting,prostration, fatigue and sweating. Diarrhea and oliguria may occur infulminating cases. Lasts for 8 to 48 hours.

ii. Latent stage: This is an asymptomatic stage, lasts for 1 to 2 weeks.

iii. Stage of overt illness: Symptoms reappear characterized by fever,anemia, leukopenia, pancytopenia, thrombocytopenic purpura,diarrhea, paralytic ileus, parasthesia, motor disturbances, ataxia,disorientation, autonomic collapse indicating involvement or injury to

CNS. Lasts for 3 weeks.iv. Recovery stage: Lasts for about 15 weeks.

Exposure to massive doses of more than 10 Gy may cause death, in a day or two from cerebral edema or cardiac failure.

Treatment Strong supportive care by prophylactic antibiotics

Bone marrow

transplantation



transplantationIon exchange carriers or

chelating agents to be

applied to facilitate the excretion of inhaled or ingested

radioactive nucleotides.

B. Chronic effects: These are the delayed effects.

Grouped into two groups – Somatic and Genetic.

i. Somatic effects: Earliest effect is on theeyes, resulting in cataract. Skin lesions appear

late They include erythema edema blisters andulcers



late. They include erythema, edema, blisters andulcers.

Still later hyperkeratosis and atrophy of thesebaceous glands occur. Skin lesions are

common with β-particles and cataract withneutrons.

The other delayed somatic effects are cancer of thelung, skin, blood, aplastic anemia and tumor

induction. These delayed somatic effects areseen among those exposed to less than 1Gy over a long period of time.

ii. Genetic effects:

These occur when gonads are exposed and

chromosomes are injured.

Chromosomal mutations result in still – births,

congenital defects, neonatal deaths and even sterility



congenital defects, neonatal deaths and even sterility

Point mutations are due to injury to genes resulting in

Down‟s syndrome, Huntington‟s chorea, polycystic

kidney, Hemophilia.

Thus somatic effects are seen within the life – span

of the affected individual, whereas genetic effects

are seen in the next generation.

Factors influencing radiation hazards:i. Type of tissue involved: Tissues like gonads, lymph

nodes, bone marrow and thyroid glands are highly

susceptible.

ii. Type of ionizing radiation: Electromagnetic radiations



ii. Type of ionizing radiation: Electromagnetic radiations

are less harmful compared to corpuscular radiations, but

they are more frequently used than latter. Among the

electromagnetic radiations, X-rays are more commonly

used than gamma (y) rays.

iii. Area of the body exposed: Larger the surface area of

the body exposed, more will be bone marrow depression

and therefore severe will be the hazard.

iv. Protective clothing: Reduces the effect.

v. Other factors: these are intensity of the radiation,

duration of exposure and individual susceptibility are

Epidemiological Points

HIGH RISK Groups During pregnancy, both the mother and the foetus are at

risk

Children are ten times more susceptible than adults to

radiation hazardsM l i h d d d bilit t d i di id l t t



Malnourished and debilitated individuals are at a greater risk than the healthy counterpart

Drugs like metronidazole and brom-uridane increasesthe susceptibility to radiations

People living at high altitudes are at a greater risk thanthose at sea level

Keralites living in coastal area are at a greater risk becauseof monozoite sand

Persons working in the following occupations are at ahigher risk – uranium mines, atomic power generation,radiology department, watch and television factories, jetnavigation, nuclear submarines, laboratories of radioactiveisotopes, sterilization of drugs, bandages, sutures, etc.

PREVENTION AND CONTROL OF RADIATION

HAZARDSBy primary and secondary prevention.

Primary PreventionPrimary prevention: is by the following measures.

Safety of the machine, man, environment and other



Sa e y o e ac e, a , e o e a d o emeasures.

Safety of the Machine

Machine should be of approved quality and installed

properly Periodical servicing and proper maintenance

Use of efficient filters so that unwanted radiations areexcluded

Operated on high kilo – voltage with fast films and imageintensifier so that exposure is reduced to minimal dose

The machine is connected to the door in such a way thatit should stop functioning automatically, the moment thedoor is opened accidentally.

b. Safety of the Worker Pre placement examination of the worker to exclude

contraindications if any for fitting the job to the worker (ergonomics)

Health education about radiation hazards and avoiding unnecessaryexposure

Regulations of exposure so that exposure is limited, by provision

of holidays and recreation and also by rotation of the worker Personal protective clothing by wearing



y y Personal protective clothing by wearing

Filter respirators / masks,

Spectacles with reflecting mirrors; visors while doing are welding

Lead aprons, lead gloves, (lead reduces the intensity over 90%)

Pocket dosimeter . (This is a monitoring device, worn on the collar by the worker, same dosimeter to be worn by the same individual,which records the cumulative dose of the radiation received bythat individual. It is sent to Atomic Research Center, where it isanalysed and report is given about the dose of radiation received. If the individual has received radiation more than the permissible limit

of 5 rads per year , clinical examination and differential count isdone)

Use of long forceps to handle radium needles

Use of shield between the source and the recipient

By avoiding eating or drinking in the working room.

C. Safety of the Environment

Air, soil and water should be clean and pure.They should be free from pollution.

d. Other Measures

Such as specifications of the room of cobalt unit and X-ray

machine, and disposal of radioactive wastes.i Specifications of the room of cobalt unit and X-ray



, pi. Specifications of the room of cobalt unit and X-raymachine.

Walls must be thick and made of concrete

Roof must be high

Wet mopping of floor to be done (Good house keeping)vecuum cleaning of the room

Lead protected doors

Lead glasses to be used for windows

Exhaust system of ventilation Controlling machine should be as far away as possible from

the worker

Enclosure of the machine, ventilated hoods, splash-trayscontrol the release of dust in the environment

ii. Disposal of radioactive wastes:

By putting in a steel case and embedding deep in the

sea bed at 1800 mts deep

By putting it in an underground concrete seal



By putting it in an underground concrete seal

By burning in a special incinerator provided with filters

and very tall stacks.

Secondary Prevention

i. Early diagnosis / detection: It is done by

periodical analysis of dosimeter.



periodical analysis of dosimeter .

ii. Treatment

For leukemia: By predinsolone, vincristine,daunorubicin, arabinosylcytosine.

For bone marrow aplasia: By antibiotics and

blood transfusion. For bone sarcoma: By amputation followed

by chemotherapy.

# If the individual is accidentally exposed and the

radio active material has entered the system, thenthe person is immediately decontaminated as

follows:

* If implanted the skin is excised the radioactive



If implanted, the skin is excised, the radioactive

material is removed, wash the area with hot water

and soap followed by application of citric acid.

**If swallowed, give adsorbants such as Prussian blue

or

ion exchange agents followed by

emetics and salt purgatives.Di ethylene Tri amine Penta Acetic acid (DTPA) is

effective.

HOUSING



HOUSING

Housing INTRODUCTION

Housing is defined as a physical structure which



ous g s de ed as a p ys ca st uctu e cprovides safety, security and shelter to the

members living in and the environment

including services and facilities necessary for maintaining optimum health by those members.

Requirements of a House

A. Location:

The house should be located on dry, non caving

ground, having an independent unit and should be nearer to

shopping place, recreational facilities, educational centers,



pp g p , , ,

emergency services and transport system.

B. Construction: The house should be so strongly constructed

as to withstand the vagaries of nature such aslandslide, floods or earth – quake, etc. and also it

should be safe and secured.

C. Health &Sanitation:From the health & point of view of, there should be

sufficient light and ventilation,

sufficient water supply and

proper arrangements for drainage of liquid waste in the

house. Provision should be made for insect and rodent



house. Provision should be made for insect and rodent

proofing.

no over – crowding and

Cleanliness to be maintained in and around the house.

D. Comfort:For this, there must be separate kitchen,

store room,bed rooms,

toilets, wash rooms

a common livin room for the

The recommended standards in India are as follows:

Site selection: The site or the ground selected shouldbe high and only to drain the water. The soil should beof gravel nature. “Made-soil” (i.e. ground leveled by

dumping refuse) and damp-sites should be avoided. Itshould have proper approach roads and away from



g )p p pp ytraffic and industries.

Foundation: This must always be solid andsubstantial. The foundation is laid with a bed of cement

concrete over the stones to cover the trench. The objectis to prevent subsidence of the building. The width of thefoundation should never be less than 25 inches.

In addition to this bed of concrete, a layer of imperviousmaterial known as “damp proof course” should be laidhorizontally, along the entire thickness of each wallat plinth level. This prevents the upward progress of the moisture.

Walls: the walls are constructed with cement and bricks or

stones, with a minimum thickness of 9 inches, obtained bylaying the bricks lengthwise and cross – wise in alternatelayers.

The walls are then plastered so that it should neither absorbheat nor it should conduct the heat. Painting of the walls

renders the surface impervious and enables easy wash. Floor: Floor should be impervious (air and water tight)



Floor : Floor should be impervious (air and water tight),surface should be smooth, facilitate easy wash and shouldbe damp-proof. The concreted floor should be covered withpatent stone slabs or in better class houses, with marble

slabs or tiles. Roof : Flat roofs should have sufficient slope to drain rain

water. Height of the roof should not be less than 10 feet, asthe heat radiated from the roof is in inverse ratio to thesquare of its distance.

Sloping roofs may be either of tiles, slates, thatch, corrugatediron, asbestos, etc. A double roof with a space between willmake a very cool covering to a dwelling.

Rooms: The number of living rooms depends upon thesize of the family to prevent over – crowding.

Doors and windows:

Every living room should be provided with at least two

windows and one of them should open directly to the

open space.



Doors and windows should be so placed as to allow cross-

ventilation (i.e. air should pass through one end and come out at

the other).

The windows should be placed at 30‟‟ (2 ½ feet) above the floor

level (and not above 3 feet) and the window area should be

1/5th of the floor area of the room.

Doors and window combined should have 2/5th of the floor

area.

Ventilators should occupy 2 ercent of the floor area,

Floor area: the optimum floor area per person

in the living room should be 50 – 100 sq. feet.

But it should never be less than 50 sq feet (Av

= 75 sq. feet).

Lighting: the day light factor should exceed



g g y g

1 percent over half the floor area.

The room is said to be adequately lighted,

when one can read or write in the center of the

hall without the help of artificial light during day

time.

Kitchen:Every house should have separate kitchen room, should not benear a privy (toilet), nor so placed as to allow the smoke and

smell of cooking getting into the rest of the house ( exhaust /chimney ).

It should not be exposed to dust and impuritiestti i t it



getting into it.

It should have adequate light and ventilation.

There should be adequate storage for

grocery, vegetables& fruit, fuel (LPG cylinders) andutensils.

There should be sufficient water supply and drainage

facility.The floor of the kitchen must be impervious.

Utility:

Water closets or privies: Minimum one sanitary privy is a

must for every house, preferably on the lee-ward side.It should have good ventilation. It should always be clean and dry

Bathroom: this should also be on the lee ward side of the house

with drainage facilities for the sullage water.



Water supply: there must be sufficient supply of safe and

wholesome water. There may be individual water source for the

house with a tube well, during the time of scarcity of water supply.

Setback: there must be sufficient open space all around the

building for adequate lighting and ventilation.

This also prevents “back-to-back” houses.

Balcony should be provided in the multi-storied buildings.

The question of open space becomes more a luxury than

necessary in cities, where the value of land is very high.

Refuse and garbage: Refuse like ash, dust, waste

paper, rags and garbage like waste vegetable andanimal material, collected in metal receptacles at leasttwice daily and emptied into the public dust bin, atregular hours.

Liquid waste like wash water from the kitchen



Liquid waste like wash water from the kitchen,bathroom and other washing places like utility and alsothe human excreta must be drained by underground

drainage system. Other provisions: in the construction of houses, efficient

space utilization, storage for household goods andpersonal belongings and home safety measures should

be incorporated. Provisions must also be made for parking of vehicles. Provision must also be made for draining of rain water . Domestic animals if any must beaway from the living rooms ( cattle sheds)

HOUSING AND HEALTH

Poor standard of housing associated with

defective ventilation and over – crowding,

affects the health of the residents, physically,

mentally and socially, resulting in increased



y y gmorbidity and mortality.

Overcrowding is based on the following three

criteria:

i. Floor area: Person ratio

ii. Room: Person ratio

iii. Sex separation

i. On the basis of floor area,

the accepted standards are

110 sq ft or more – 2 persons

90 – 110 sq ft – 1 ½ person(A child between 1 to 10 years is



(A child between 1 to 10 years is

considered as half

person or half unit)

70 – 90 sq ft – 1 person50 – 70 sq ft – ½ person

(A child below one year is not

counted)

On the basis of room – Personratio,

the accepted standards are:



1 Room – 2 persons

2 Rooms – 3 persons



5 Rooms or more – 10 persons

(additional 2 for each further

room)

.

iii. On the basis of sex separation,

overcrowding is considered,

if 2 persons, over 10 years of age, of opposite sex,

unless husband and wife,



are obliged to sleep in the same room

Overcrowding associated with poor

ventilation

(and poor housing) causes

rise of temperature,

excessive humidity and air stagnation of the room



which lowers the vitality of the inmates and makes them

more susceptible to diseases.

Respiratory diseases spread by droplet infection

very fast such as tuberculosis, measles, influenza,

streptococcal throat infections, acute rheumatic fever, common

cold, diphtheria, whooping cough, bronchitis, etc.

contagious diseases like scabies, impetigo,

ringworm, leprosy, trachoma, conjunctivitis

also spread.

Overcrowding has a bad social effects especially



Overcrowding has a bad social effects especially

when persons of opposite sexes occupy the same

sleeping room.

On the other hand, isolation or loneliness felt

by the person, living alone in the house, may result

in

neurosis,



,

psychosis,

behavioral disorders and

also habits like alcoholism anddrug addiction.

Standards of Rural Housing

Built up area should be about 60% of the total site. There must be sufficient space around the house for

adequate lighting and ventilation.

The area of doors and windows should be about 25% of the floor area.

At least two living rooms.

S t kit h ith i i f hi f t il



Separate kitchen with provision for washing of utensils.

Provision for washing the clothes.

Soakage pit for disposal of sullage water coming form

bathroom and kitchen. House should be provided with a RCA latrine.

The source of water should be within the reach of about 400meters.

Live stocks like cattle, pigs, sheep, etc. should be awayfrom the human dwellings.

There must be manure pit arrangements for the disposal of kitchen waste and domestic refuse.

Di l f W t



Disposal of Wastes

DISPOSAL OF WASTES

The waste products of the community are refuse, human excretaand sullage.

Refuse



It is a solid waste. It is of the following types:

Street refuse – consists of leaves, straw, papers, animal dung andlitter of all kinds.

Market refuse – consists of putrid vegetables and animal matters. Domestic refuse – consists of ash, rubbish (pieces of papers,

clothes, wood, metal, glass and dust and dirt) and garbage (wastearising from the kitchen, such as peelings of vegetables, waste food,rotten fruits and vegetables, etc).

Industrial refuse – consists of wide variety of toxic chemical

compounds. Stable litter – consists of mainly animal dung and left over animal

feeds from animal stables.

Health HazardsPollution of water, soil,

Contamination of food and drinks through



dust and

flies,

Decomposed refuse favours propagation of house

files,

Attracts, rodents and vermin.

Nuisance b si ht and smell.

Storage of Refuse

Dustbins made of galvanized iron sheets are suitablereceptacles, placed at a fair distance from the house. If it iscovered with a lid, people will not open it but throw the refusearound it. If not covered, the dogs, pigs and other animalsscatter the contents, thus creating nuisance.

In the developed countries, the dustbins will have “paper sack”. When the paper sack is filled, it is removed from the



p pbin and a new sack is placed inside.

The municipal workers remove the refuse periodically.

Collection of Refuse

House to house collection of refuse is the best method but thatis not done. Dumping the refuse in the public dustbin is alsonot done properly. As a result, refuse is dispersed all alongthe street. The Environmental Hygiene Committee (1949)recommends.

House to house collection of refuse,

Open refuse carts should be replaced by enclosed vans,

Mechanical transportation is more practical andeconomical.

METHODS OF REFUSE DISPOSAL

There are many methods. But choice depends upon the cost

factor and the availability of land and labour. The different

methods are:

a. Dumping



b. Controlled tipping.

c. Composting.

d. Manure pits.e. Burial.

f. Incineration.

a. DumpingIn this method, the refuse is dumped in the low

lying areas and later reclamation is done and

used for cultivation purpose. Since it results inall the health hazards mentioned above the



all the health hazards mentioned above, the

land selected for dumping should be as far

away from human habitation or outside thelimits of the town.

WHO Expert Committee (1967) condemned

dumping as “a most insanitary method of disposal of refuse because of the health

hazards”, to be replaced by sound procedures.

b. Controlled Tipping (SanitaryLandfill)

This is nothing but dumping or burial of the refuse in a sanitary

way as to prevent the health hazards.The dumping site should be outside the city limits,



p g y ,

away from the human

habitation and away from

sources of water,so that water pollution due to leaching from refuse dumps is

avoided.

After dumping the refuse, it is covered with a layer of earthon the top daily, so that nuisance by sight and smell and also

breeding of flies is prevented.

There are three methods of controlled tipping

– the trench method, the ramp method and thearea method.

i. The trench method: This is preferred in thoseareas, where low lying area are not available. A

trench of about 2 – 3 mtr deep and 4 – 12 mtr wide is dug. The refuse is placed and covered



gwith excavated earth. It is estimated that one acreof land per year will be required for 10,000population.

ii. The ramp method: This is suitable in thoseareas

where theterrain is moderately sloping.

iii. The area method: this differs from trenchmethod in that the trench is not dug but landdepressions like dried ponds and clay pits are

After about one week of burial of refuse,temperature rises to about 600C, killing all the

pathogens followed by decomposition process.

After another 2 – 3 weeks, it cools down.



,

Within 4 to 6 months, all the organic matters

are decomposed to innocuous mass.

The “made-soil” is suitable for gardening.

It can also be utilized for construction purposes, but

after several years.

c. Composting

In this method the refuse is disposed off along with thenight-soil or sewage.

There are two methods – Biological and Mechanical i Biological: Thi i l ll d Bangalore method



i. Biological: This is also called as Bangalore method or

anaerobic method or hot fermentation process.

In this method, trenches are dug measuring 5 -10 mtr length, 2 mtr breadth and 1 mtr depth, away from the city limits.

Alternate layers of refuse and human excreta (night – soil) are put into the trench, in the thickness of 15 cm and 5 cmrespectively, the first and last layer being that of refuse. The trench is thencovered with excavated earth..

Within about a week intense heat is generated to about 600C, persisting

for about 2 to 3 weeks killing all the pathogens and the parasites. Thelignin and cellulose are broken down. The end products of decompositionare acted upon by fungi and anaerobic bacteria, resulting in harmless,odourless, innocuous humus mass, called “Compost”, which has highmanure value. It is sold as organic manure, without causing any nuisance.It is ready for application to the land.

ii. Mechanical:

This is also called as “Aerobic method”. In this

method, the refuse is first cleared of salvageable

materials such as rags, bones, pieces of metal,

wood, glass, etc. andthen powdered in a pulverizer



then powdered in a pulverizer .

It is then mixed with human night soil in a

rotating machine and incubated for 4 – 6 weeks,

entire process of composting is complete by the

action of temperature,

moisture,

pH andaerobic bacteria.

The mixture gets changed to compost.This method is in vogue in developed countries.

d. Manure Pits

This method is preferred in rural areas, where

collection and removal system of refuse is absent.

The individual householder should have a “manure

pit” where in the daily domestic refuse is dumpedand covered with earth after each day‟s dumping



and covered with earth after each day s dumping.

When one is filled other pit should be used.

After about 4 – 6 months, the refuse is converted intocompost,

which can be used to the field as manure.

This is a simple and effective method.

e. Burial

This is suitable for small camps.

This is also the same as trench method,

but in the trenches, only the refuse is buried and notthe human excreta.



At the end of each day, the refuse is covered with earth.

When the trench is filled, new trench is dug out.

After 4 – 6 months, the compost is removed and used

as manure.

f. IncinerationThis is the process of burning the solid waste and is the most sanitary

method of disposal of refuse, especially the hospital refusebecause of its dangers.

The incinerator consists of the following features.

A furnace or combustion chamber lined with fire – bricks, where the

fire is built with firewood or electricity. A platform for tipping the refuse.

St k (th h th i ) t b i th f t th f



Stokers (through the openings) to bring the refuse together for burning completely.

A baffle plate to drive of all the fumes.

By this process is burning the refuse the refuse is reduced to aboutone fourth of its original weight and the organic matter is transformed into innocuous vapors – carbon dioxide andnitrogen.

The residuum left after the combustion is a mass of hard materialcalled “clinkers”, which are utilized for making the roads. It is alsoused as cement by powdering the clinkers and mixing with lime.

This method is feasible in those city areas where considerable-





The incinerators built of mud or iron without bricks

do not give satisfactory results. However, theyare suitable for fairs and melas of shortduration. The “Beehive incinerators” havebeen found under such conditions.

The drawback in many incinerators is that the



draught is not sufficient.

Therefore they give off offensive smoke

creating nuisance.To overcome this, the temperature in the furnace

should be more than 12500F,

the chimney should be tall andwith adequate air .

Recycling of RefuseAll reusable materials are separated from the

refuse and used.

Paper and rags are used for paper production.

Plastics are sorted out by type and recycledseparately for the manufacture of plastic



p y pbuckets, pots, mugs, etc.

Glass, rubber, aluminium, copper, iron, brass,

etc. are melted and put to their respective uses.

Discarded tube lights are used for the manufactureof laboratory glassware.

Garbage and plant wastes are used for composting.

Animal excreta are separated and used for roducin bio as.

DISPOSAL OF EXCRETA



DISPOSAL OF EXCRETA

Human excreta is a source of pollution.

It causes pollution of the physical environment such as

food, water and soil.



This results in many diseases, such as typhoid, para –

typhoid, diarrhoeal diseases, dysenteries, amoebiasis,ascariasis, viral hepatitis, poliomyelitis, ankylostomiasis

and such other infections and infestations, all resulting in

increased morbidity and mortality in the community,

which is a threat to public health.

In India nearly 50 million people are suffering from such

diseases every year and nearly 5 million of them die.This is because of the following reasons:

80% of the population live in rural areas.

Rural people still go to the fields for open defecationbecause of the belief that fifth should not be inside thehouse.

Rural people have lack of knowledge about the



Rural people have lack of knowledge about theimportance of using sanitary latrines.

Excreta is an excellent breeding place for house flies.

Excreta is nuisance by sight and smell. Lack of sewerage system.

Non – availability of any kind of latrine whatsoever.

Ill maintained community latrines, so the filth over flows

on the street. Endemicity of water borne and soil borne disease,

often resulting in epidemics.







Sanitation Barrier Transmission of various gastro intestinal infections , which

are prevailing as endemic diseases in the country, can be

prevented and controlled, by preventing the contamination

of physical environment such as food, water and soil, by

construction of a barrier called “Sanitation barrier”, which is

nothing but construction and use of sanitary latrines



nothing but construction and use of sanitary latrines,

which prevents the access of the pathogens from

Faeces (F) through 6 Fs such as :

Fluid (Water and Milk),

Food, Fruits and Vegetables,

Fomites (utensils),

Flies (vectors)and

Fingers,

to the mouths of susceptible

The construction and use of sanitary latrines will be

more effective, when supplemented byprocedures such as :

chlorination of water ,

pasteurization of milk,adoption of food hygienic measures,



disinfection of fruits and vegetables,

disinfection of utensils,

control of house flies and

adoption of personal hygienic measures liketrimming of the nails and

washing the hands with soapbefore eating and after toilet.

Methods of Disposal of Excreta (Night Soil)

This depends upon the availability of underground

drainage system (sewerage system).

The collection and removal of night soil from the



bucket by the human agency is called “Service

type” and “conservancy system” which is not

consistent with human dignity and is no longer pardonable.

Therefore Environment Hygiene Committee

(1949) has recommended that in unsewered areas,

the service latrines (or bucket latrines) should be

replaced by sanitary latrines, in which the excreta

A Unsewered areas1. Service Type ( Conservancy

)

Night soil is collected in a pail /



g t so s co ected a pa /

bucket , and disposed off by:

Burial

Composting

2. Non - Service Type(Disposal is in

situ)

The different types of sanitary latrines are:

a. Bore hole latrine.

b. Dug well (pit) latrine.

c. Water seal type of latrine.

i. PRAI type.ii. RCA type



iii. Sulabh Shauchalaya

d. Septic tank latrine.

e. Aqua privy.f. Sanitary latrines for fair, mela, camp ( Temporary

Use )

i. Shallow trench latrine.

ii. Deep trench latrine.iii. Pit latrine.

iv. Bore hole latrine.

g. Biogas plant.













Sulabh Shauchalaya

It is a low cost, pour – flush, water-seal type of communitylatrines installed in public places.

It is an improved version of RCA type of latrines,consisting of especially designed pan and a water – sealtrap, connected to a pit of 1 meter square and 1 meter deep.

It is well lighted and ventilated, maintaining the privacy



g , g p yand cleanliness.

Such latrines are maintained through the nominal fee

collected from the users.“Sulabh International” are the investors of such

community latrines. They construct adjoining bathroomsalso and charge nominally.

These latrines are eco – friendly.These are now being used in all parts of our country.

It was first invented by Patna based firm.



Septic Tank

It is an ideal sanitary water seal latrine which can meet the requirementsof families in towns and cities having piped water supply but nosewerage system.

The tank is an underground, rectangular, cement concrete tank,having an inlet, outlet, cover and a vent pipe, into which thehousehold sewage, which is a mixture of night soil, urine and wash

water, is drained. As the sewage enters the septic tank through the inlet pipe, the non –

putrescible black semisolid particles settle down to the bottom of the



putrescible black semisolid particles settle down to the bottom of thetank to form “sludge” and the grease, fat and light solid matter floatson the surface to form “scum”, which is an air – tight layer and cutsoff air to the faecal matter. Under the scum the anaerobic bacteriaare actively at work breaking down the solid masses into simpler substances of fine suspension. The complex protein molecules arebroken down into amines, amino acids, evoluting gases likemethane,

carbon dioxide,

carbon – monoxide,hydrogen sulphide,

etc.

The colloids in suspension become crystalloids in solution and areready to take up oxygen. This is the first stage of purification.

In the next stage, the effluent (the liquid coming out of theoutlet pipe periodically) which contains numerous bacteria,ova, cysts and organic matter, is turbid but translucent with asickly but otherwise offensive smell.

Since the effluent still contains nitrogen as ammonia, shouldbe oxidized by aerobic bacteria present in the soil tonitrites andnitrates.Therefore it is subjected to further purification by the actionf bi b t i b b il i i ti i t th



of aerobic bacteria by sub – soil irrigation into thesurrounding earth through performed pipes. This is thesecond stage of aerobic oxidation.

The sludge is much reduced in volume as a result of anaerobic digestion. It becomes stable and inoffensive.When the sludge grows to a certain height it interferes withthe action of septic tank. It is time for removal. Meanwhile thescum is also removed. The sludge and the scum aredisposed off by trench method. Cleaning is done throughthe manhole.

Since septic tank is recommended for individual familiescleaning is required once in 5 years. However, in large

The following are the requirements for a septic

tank installation: There must be abundant supply of water , so as

to flush out the excreta to the tank.

No disinfectant or detergent to be used in thetank, because of the destruction of the putrefactivebacteriae



bacteriae.

There must be sufficient space, between the fluid

level and the cover to accommodate the “Scum”and the gas.

There should be a ventilator pipe to let off the foulgas.

The sludge to be removed periodically (i.e.desludging)



Biogas Plant

These are also popularly known as gobar-gas plant. In this method,not only the human night soil is disposed off but also animaldung and

left over animal feeds are also disposed. A suitable place in the courtyard near the cattle – shed is selected. A

well of about 3 meters is dug with variable diameter depending upon



well of about 3 meters is dug with variable diameter depending uponthe size of the live – stock. A small chamber called “mixingchamber” is constructed at one end of the cattle – shed near thewell, where animal dung after collection from the shed is mixed withwater. Urine of the cattle is also allowed in this chamber. The humannight soil, urine and wash – water of the sanitary latrine is alsodrained into the same digester.

An inverted dome shaped metallic gas holder is put in the well, whichholds gases produced in the digester, chiefly the methane.

As the gas collects, dome rises.The gas is utilized for lighting and cooking purposes.

The scum and sludge are periodically removed anddisposed in trenches, which later becomes an excellent organic

Merits of Biogas Plant

Human and animal excreta can be disposed simultaneously.

It is an excellent source of energy at a low cost.

Refuse can also be disposed



Refuse can also be disposed.

Provides an organic manure of high biological value.

It is eco friendly.

It involves active community participation.

It can be installed at family or community level.



Chemical Closet

This consists of a metal tank containing adisinfectant, placed underneath the pan of the

toilet.

The disinfectant used is a solution of caustic sodaand phenol and covered with a layer of crude oil.

The excreta falls into this solution where the alkali



The excreta falls into this solution, where the alkalidisintegrates and dissolves the excreta, phenol

kills the bacteria and the oil prevents odour .

Nothing except toilet paper should be thrown into thechemical closet.

When the tank becomes full, the contents are dischargedinto a sump hole.

Chemical closet is suitable for isolated houses, boats, air crafts motor caravans etc.

B. Sewered areas.

In this type, the night – soil is transported

by water carriage system to the point of

disposal.

Disposal of excreta starts with latrine, which is a provision made



p , p

for passing and collecting the excreta.

A sanitary latrine is a one which fulfils the following criteria:

The night soil should not contaminate the ground or surface water.

It should not pollute the soil.

It should not be accessible to house flies, rodents and animals likepigs, dogs, cattle, etc.

It should not create nuisance by sight and smell.

It should be cheap, easy to construct and acceptable to the

WATER CARRIAGE SYSTEM(SEWERAGE SYSTEM)

This system is adopted to transport human nightsoil and other liquid waste of the community.

The term “sewage” means liquid waste of thecommunity containing human night soil, street

hi d i d t i l li id t



washing and industrial liquid waste.

The term “Sullage” is the waste water of thehouses, excluding human excreta, i.e. wastewater coming from kitchens and bathrooms.

In this system, the liquid waste is carried away

through a system of drains and underground pipes(sewers) from the houses, industries andcommercial areas, through the agency of water tothe place of ultimate disposal.

Therefore, it requires an abundant water supply.

Even though the initial investment is heavy, it ischeaper in the long run and is the cleanest, quickest

and most sanitary method of removing night soil.

For successful operations



For successful operations,

the following conditions are essential:

An abundant supply of water.

Good drains and sewers with proper ventilation.

Sufficient slope to give the required velocity, to the

sewage.

There are two types of water carriage system –

the combined andseparate sewer system.

In the combined system, the sewers carry both the sewage and the surface water .

In the separate system, the surface water is not admittedinto sewers The separate system is the system of choice



into sewers. The separate system is the system of choice.

The water carriage system consists of the following elements:a. House drainage

b. Public sewer

c. Sewer appurtenances.

House Drainage

i. Water closetii. Soil pipes

iii. House drain.

DISPOSAL OF SEWAGE

(or SEWAGE TREATMENT)Sewage is a mixture of human excreta, urine, wash water,liquid waste coming from bathrooms and kitchen, surfacewater and industrial liquid waste.

It is a dirty water with unpleasant sight and smell, which if

not drained and disposed off, can contaminate sourcesof water and also food and vegetables resulting indiseases and deaths.



diseases and deaths.

Objectives of Sewage Treatment Protection of water sources from contamination.

Protection of soil against pollution.

Protection of fish and aquatic life.

Protection of human food, which are eaten raw. Prevention of hazards to live – stocks.

Prevention of nuisance by sight and smell.

Therefore, from hygienic and aesthetic

considerations, sewage treatment is essential.The economic aspect of sewage treatment is also far and wide.

Valuable recoveries are possible from a completely

treated sewage such as nitrates, phosphates,grease, vitamin B12, methane gas for lighting andcooking purposes, etc.



g p p ,

The aim of the sewage treatment is to stabilize the

organic matter by bacterial action, to utilize theinnocuous products without risk to human healthand to produce an effluent which can be disposedoff into land, river or sea without causing danger.

Stabilization means breaking the organic matter intosimpler substances, which cannot be decomposedfurther.

The quality or strength of the sewage isexpressed in terms of

Biochemical oxygen demand (BOD),

Chemical oxygen demand (COD)and

suspended solids.



These indicators are required

to know the amount of water neededto dilute the sewage during its final

disposal.

Biochemical Oxygen Demand (BOD)

It is the amount of dissolved oxygen required

by the living organisms in the sewage, during 5 days

incubation

at 200C for aerobic oxidation of the organic matter.



It is expressed as mg per litre of sewage (i.e. ppm).

If BOD is 100 ppm the sewage is said to “Weak” and

if it is 300 ppm, the sewage is said to be “Strong”.

After complete treatment of sewage, the BOD is reduced to nearly90%.

Chemical Oxygen Demand (COD)

It is the amount of organic matter in the sewage

that is susceptible to oxidation by a strong

chemical oxidizer .

Suspended Solids



Suspended Solids

If the amount of suspended solids is 100 ppm, the

sewage is said to be “weak” and if more than 500ppm, the sewage is said to be “strong”.

After treatment of the sewage, it should become weakwith reference of BOD and suspended solids.

MODERN SEWAGE TREATMENT



Primary Secondary

Treatment ( ANAEROBIC ) Treatment ( AEROBIC)

CHLORINE

Sewage

Effluent

Scree

n

Grit

Chamb

er

Primary

Sedimentation

Tank ( 6 - 8

Hrs )

Biologica

l

Treatmen

t

Secondary

Sedimentation

Tank ( 2 –3

Hrs)

Sludge

Digeste



Disposal Activated

Sea Outfall

River Outfall

Sewage FarmSludge

Oxidation Pond

Oxidation Ditches

Methane

Gas

Digeste

r (Incubated

) Temp,pH

Sludge Drying Beds

Alt t

PrimarySedimentati

on ( 6-8 Hrs )

Aeration

Tank

6 – 8 hours‟

Detention

Final

setting Tank

( 2-3 Hrs )



Alternate

Sludge to

digester Excesssludge to

digester

or

Excess sludge Return and excess sludge

thickener

R e t u

r n

s l u d g e

2 0 – 3

0 %

Activated sludge

process









Trickling Filter



Activated Sludge

Process

MODERN SEWAGE TREATMENT

Modern sewage treatment plants are based onbiological principles of sewage purification, where

the purification is brought about by the action of

anaerobic and aerobic bacteria.The treatment of sewage may be divided into two

stages primary treatment and secondary



stages, primary treatment and secondary

treatment.

# In primary treatment, the solids are separated

from the sewage partly by screening and partly

by sedimentation and subjected to anaerobic

digestion which is the first stage in purification;## in secondary treatment, the effluent is

subjected to aerobic oxidation, which is the

PRIMARY TREATMENT

1. ScreeningSewage arriving at a disposal work is first passedthrough a metal screen which intercepts largefloating objects such as pieces of wood, rags,

masses of garbage and dead animals.Their removal is necessary to prevent clogging of

the treatment plant



the treatment plant.

The screen consists of vertical or inclined steel barsusually set 5 cm (2 inches) apart.

In some plants, the screens are of the fixed typewhile in others, the screens are of the movingtype.

The screenings are removed from time to timeeither manually or mechanically, and disposedoff by trenching or burial.

2. Grit chamber

Sewage is then passed through a long narrowchamber called the grit chamber or detrituschamber.

This chamber is approximately 10 to 20 metres inlength; it is so designed as to maintain a constantvelocity of about 1 foot per second,



with a detention period of 30 seconds to 1

minute.The function of the grit chamber is to allow the

settlement of heavier solids such as sand andgravel, while permitting the organic matter to

pass through.The grit which collects at the bottom of the chamber

is removed periodically or continuously,

3. Primary sedimentation

Sewage is now admitted into a huge tank called theprimary sedimentation tank.

It is a very large tank, holding from ¼ to 1/3 the dryweather flow.

There are various designs in primary sedimentation tank.By far the commonest is the rectangular tank.

Sewage is made to flow very slowly across the tank at avelocity of 1 2 feet per minute



velocity of 1 – 2 feet per minute.

The sewage spends about 6 -8 hours in the tank.

During this long period of relatively still conditions in thetank, a very considerable amount of purification takesplace mainly through sedimentation of suspendedmatter . Nearly 50 – 70 per cent of the solids settle

down under the influence of gravity.A reduction of between 30 to 40 per cent in the number of coliform organisms is obtained

The organic matter which settles down iscalled sludge and is removed by

mechanically operated devices, without

disturbing the operation in the tank.



While this is going on, a small amount of

biological action also takes place in which themicro-organisms present in the sewage

attack complex organic solids and

break them down into simpler solublesubstances and ammonia.

A certain amount of fat and grease rise to thesurface to form scum which is removed from

time to time and disposed of .

When the sewage contains organic trade



g g

wastes, it is treated with chemicals such as

lime, aluminium sulphate and ferroussulphate. Addition of one of these chemicals

precipitates the animal protein material quickly.

SECONDARY TREATMENT

The effluent from the primary sedimentation

tank still contains a proportion of organic matter

in solution or colloidal state, and numerousliving organisms.



It has a high demand for oxygen and can

pollution of soil or water.

It is subjected to further treatment, aerobicoxidation, by one of the following methods:

a. Trickling Filter Method

b. Activated Sludge Process

a. TRICKLING FILTER

The trickling filter or percolating filter is a bed of crushedstones or cinker,

1 to 2 m (4-8 ft.) deep and 2 to 30 m (6-100 ft.) in diameter,depending upon the size of the population.

The effluent from the primary sedimentation tank is sprinkled

uniformly on the surface of the bed by a revolving device.The device consists of hollow pipes each of which have a row

of holes.



The pipes keep rotating, sprinkling the effluent in a thin film onthe surface of the filter.

Over the surface and down through the filter, a very complexbiological growth consisting of algae, fungi, protozoa andbacteria of many kinds occurs.

This is known as the “zoogleal layer”.

As the effluent percolates through the filter bed, it getsoxidized by the bacterial flora in the zoogleal layer.

The action of the filter is thus purely a biological one, and notone of filtration as the name suggests.

The term “filter” is a misnomer .

The trickling filters are very efficient in purifyingsewage.

They do not need rest pauses, because wind

blows freely through the beds supplying theoxygen needed by the zoogleal flora.

The biological growth or zoogleal layer lives



The biological growth or zoogleal layer lives,grows and dies.

The dead matter sloughs off, breaks away andis washed down the filter. It is a light green,flocculent material and is called “humus”.

The oxidized sewage is now led into thesecondary sedimentation tanks or humustanks.

b. ACTIVATED SLUDGE PROCESS Activated sludge process is the modern method of purifyingsewage, in place of the trickling filter.

The “heart” of the activated sludge process is the aerationtank.

The effluent from the primary sedimentation tank is mixedwith sludge drawn from the final settling tank (alsoknown as activated sludge or return sludge; this sludge is ai h lt f bi b t i )



rich culture of aerobic bacteria).

The proportion of activated sludge to the incoming effluent is of the order of 20 to 30 per cent.

The mixture is subjected to aeration in the aerationchamber

for about 6 to 8 hours.

The aeration is accomplished either by mechanical agitationor

by forcing compressed air continuously from thebottom of the aeration tank.

.

During the process of aeration, the organic matter of the

sewage gets oxidized into carbon dioxide,

nitrates and

water with the help of

the aerobic bacteria in the activated sludge.

Th t h id d h l i d fi it l



The typhoid and cholera organisms are definitely

destroyed, and the coliforms greatly reduced.

Activated sludge plants occupy less space, require

skilled operations.

One acre of activated sludge plant

does the work of 10 acres of percolating filter .Activated sludge process is therefore, best suited for

larger cities and the percolating filter for smaller towns

Secondary ( Final ) Sedimentation

The oxidized sewage from the trickling filter or aeration chamber is led into the secondarysedimentation tank where it is detained for 2 – 3hours.

The sludge that collects in the secondarysedimentation tank is called „aerated sludge‟ or activated sludge because it is fully aerated



activated sludge, because it is fully aerated.

It differs from the sludge in the primarysedimentation tank in that it is practicallyinoffensive and

is rich in bacteria, nitrogen and phosphates.

It is a valuable manure, if dehydrated.Part of the activated sludge is pumped back into

the “aeration tanks” in the activated sludge

Sludge digestion

One of greatest problems associated with

sewage treatment is the treatment and

disposal of the resulting sludge.



p

One million gallons of sewage produces 15 –

20 tons of sludge.

The sludge is a thick, black mass containing 95

per cent of water , and it has a revolting

There are a number of methods of sludge disposal:

a. Digestion: Modern sewage treatment plants employdigestion of sludge as the method of treatment.

If sludge is incubated under favourable conditions of temperature and pH, it undergoes anaerobic auto –

digestion in which complex solids are broken downinto water, carbon dioxide, methane and ammonia.

The volume of sludge is also considerably reduced.



It takes 3 – 4 weeks or longer for complete sludge

digestion.The residue is inoffensive, sticky and tarry mudwhich will dry readily and form an excellent manure.

Sludge digestion is carried out in special tanks known

as “sludge digestion tanks”. Methane gas, which is a by – product of sludgedigestion, can be used for heating and lighting

ur oses.

b. Sea Disposal:

Sea coast towns and cities can dispose of

sludge by pumping it into the sea

c. Land:



Sludge can be disposed of by composting

with town refuse.

Disposal of effluent

a. Disposal by dilution:

Disposal into water courses such as rivers and streams is called„disposal by dilution‟.

The effluent is diluted in the body of water and the impurities areoxidized by the dissolved oxygen in water.

The diluting capacity of the river or the receiving body of water andits dissolved oxygen contents are important considerations before



its dissolved oxygen contents, are important considerations beforedischarging the effluent into a river or any body of water.

Since people use river water for drinking purpose, the effluentmust be rendered free from pathogenic organisms by adequatechlorination.

During the past few years, industry has developed hundreds of newchemicals which are released into the sewerage system.

Some of these chemicals are not removed by biological treatment.Consequently, the effluent may contain substances toxic to man, or substances that can kill fish, damage agriculture or interfere with thenormal functioning of a stream.

The Royal Commission in England in its Fifth Report

(1908) recommended that an effluent from asewage treatment plant should not have more

than 30 mg / litre of suspended solids and

the 5 day B.O.D. of the effluent including the

suspended matter, should not exceed 20 mg/litre.

These standards assumed that the river or body



These standards assumed that the river or body

of water into which the effluent passed would

provide an 8:1 dilution.

These standards have been the backbone of

subsequent work on the purity of sewage effluent.

In many places in the UK, effluent standards have

been raised from the original RoyalCommission values of 30 mg per litre of

suspended solids and 20 mg per litre of B.O.D.

to 10 mg per litre of each.The World Health Organization is seized with this

problem and is fostering research in “tertiary”



problem, and is fostering research in tertiary

methods of treatment or “polishing” theeffluent further.

(b) Disposal on Land: If suitable land is

available the effluent can be used for irrigationpurposes (e.g., the Okhla Sewage Treatment

Plant in Delhi).

Other Methods of Sewage Disposal

1. Sea Outfall

2. Sewage dilution and

River Outfall



River Outfall

3. Land TreatmentSewage farming.

4. Oxidation Ponds

5. Oxidation Ditches6. Sewage lagoon

Sewage DilutionThis consists of discharging the sewage directly into a large body of

water such as river (river outfall) or sea (sea outfall).This is an age old practice still prevalent in many cities which are

located on the banks of rivers and on sea – shores.

Natural purification takes place in the water to some extent.

River outfall is hygienically not safe.

Discharging the industrial waste may even lead to dangerousconsequences.



However, discharging the sewage beyond the habitation area, in adownstream, will reduce the public health hazard.

Sea outfall is also good, because of large body of water available for dilution and solids get oxidized.

But the drawback is that the offensive solid matter maybe

washed back to the shore and create nuisance.It may affect the aquatic life.

So to overcome this, the sea outfall is designed to discharge thesewage into deep water at many points.

Sewage Lagoon

This is also called as “Oxidation Pond”. It is so called becausein this lagoon (pond) the sewage organic matter are oxidizedinto inorganic substances including CO2, Ammonia and water and thus the sewage is purified.

The oxidation pond is a shallow pool of about 20 acres area,constructed in open areas, about 1.5 meter deep, having aninlet in the middle of the pond to allow the wind and waveaction for the uniform mixing and distribution of the sewageand an outlet for the effluent. Better if the sewage issubjected for screening and grit removal and then let into the



subjected for screening and grit removal and then let into thelagoon.

The sewage lagoon stabilize the sewage by a complexinterdependent mechanisms involving

algae,

aerobic bacteria,

oxygen and

sunlight.

The aerobic bacteria, which feed on decaying organic matter,oxidize the organic matter and convert it into CO2, ammoniaand water. Hence the name “Oxidation ond”.

The algae, with the help of sunlight, carry out photosynthesis,by utilizing CO2, water and inorganic materials and liberate

oxygen. Thus oxygen required by the aerobic bacteria for oxidation, is obtained mainly from the algae and partly fromthe atmosphere.

Sunlight provides the necessary energy to algae to thrive bycarrying out photosynthesis. Algae cannot thrive in the

absence of sunlight. Consequently sunlight is an importantfactor for proper functioning of the oxidation pond.

Cloudy weather definitely lowers the efficiency of theprocess



process.

The other synonyms are “Waste stabilization pond”, and

“Redox pond”.

The effluent may then be let into the land for irrigation purposeor into a water course after treatment.

The lagoons require periodic servicing for optimum functioning.

The luxurious growth of marginal vegetation and other weedsover a period of time, should be eliminated periodically todiscourage breeding of the mosquitoes.

Such ponds are the established method of disposal of sewage

Sewage FarmingIt is also called as “Broad irrigation”. It is also an age old method of

sewage treatment. It suits in those areas where porous land isavailable in the vicinity of the habitation. An acre of land would berequired to dispose the sewage of about 300 persons. Beforeadmitting the sewage in the farm, it is subjected for screening and gritremoval.

The land (farming area) is first laid in the form of ridges and furrows.Sewage is allowed in the furrows and crops are grown on the ridges.Only such crops are grown which do not come in direct contact withsewage or not likely to be eaten raw. Folder grass and potatoes seem to be the most paying crops.



p y g p

But tomato, cucumber, sugar cane, coriander and such others are

not recommended to be grown.Sewage farming can remove 90% of the suspended organic matter by the activity of the aerobic soil bacteria. Continuous feeding of sewage farms without any interruption leads to stinking andsoddenness of the soil, a condition called as “Sewage sickness”,due to lack of sufficient aeration of the land. Such badly managed

farms can be hazardous. Therefore maintenance of sewage farmsdeserves special attention.

However, during the rainy season, it may not be possible tooperate the sewage farms. Alternate methods may have to beprovided then.





Thank You

&

Best Wishes

SEWAGE TREATMENT

The treatment of sewage is done in two stage – namely primary and secondary treatment:

A. Primary Treatment (Preliminary treatment)In this stage, the suspended matters like the floating

objects, settle able organic matter and inorganicti l ll d



particles are all removed by employing simple

physical methods – such as screening, gritchamber and primary sedimentation ( i.e.anaerobic digestion )

B. Secondary Treatment In this stage, the effluent is subjected to bacterial

action for stablilization (i.e. aerobic oxidation).

A. Primary Treatment

a, Screening: The sewage is allowed to pass

through metal screens to hold back the floating

objects.

S b fi C i t



Screens may be coarse or fine. Coarse screens consist

of metallic bars placed vertically or inclined, set 5 cmapart. The fine screens have meshes. Screening

removes leaves, pieces of wood, rags, vegetable

garbage, waste paper, polythene bags, dead animals

and various other floating objects. The screenings areremoved periodically and disposed off by burning or

by burial.

b. Grit removal:

Grit consists sand, gravel, ash, clay etc.

These are removed by allowing the sewage to

pass through a 15 – 20 mtr long, narrow

chamber, called Grit chamber or Detrituschamber (after passing through the screens)

where the sewage passes at a velocity of 0 3



where the sewage passes at a velocity of 0.3

mtr per second, which is just sufficient to permitthe grit to settle down and the organic matter

to pass over. The grit is removed periodically

and disposed off by dumping or trenching.

C. Primary sedimentation:

After clearing the sewage from the floating objects and grittymatter, It is subjected to sedimentation in a tank for the removal of

settle able suspended matter.

The rectangular sedimentation tanks provide horizontal flow and

circular tanks radial flow, where the sewage is detained for

about 6 hours.

All the suspended organic matter settle as sludge.The sludge of the primary sedimentation tank is highly organic



The sludge of the primary sedimentation tank is highly organic

and offensive.

It is removed periodically to control nuisance and to prevent

interference in the sedimentation process (i.e. desludging).

Such a sludge should not be disposed off directly

but , transferred to sludge digestion tank

for appropriate treatment.

B. Secondary Treatment

The sewage after primary treatment is subjectedfor the complete or final treatment by biological

action / treatment followed by secondary

sedimentation and sludge digestion.The biological treatment is of two types –

Bi filt ti d



a. Biofiltration and

b. Bioaeration.

Biological action (aerobic oxidation) is

necessary for stabilization of unsettleable

organic matter.

a. Biofiltration:

In biofiltration, the sewage, (after primary

treatment) or the effluent from the septic tank is

allowed to „filter‟ through a medium supporting the

aerobic bacteria that carry out the biologicaltreatment.



Biofiltration can be done by either of the three

methods:

i. Trickling filters,

ii. Intermittent Contact beds and iii. Intermittent sand filters.

i. Trickling filters:

These are also called as“Percolating filters” or “Sprinkling filters” or “Streaming

filters”. The filter consists of water – tight,concrete, enclosure tank, circular in shape, of about 25

meters diameter and 2.5 meters depth, filled with afilter medium consisting of pieces of 2 – 10 cm of coarse materials like stones, coke, clinker (hardbrick) or cinder (burned coal) etc arranged loosely to



brick) or cinder (burned coal) etc arranged loosely toprovide oxygen to the aerobic bacteria resting on them.

Such a tank is provided with a sewage sprinklingsystem, which consists of a pipe carried above the tankand fitted with rotator arms, usually four in number,each arm having a series of spray nozzles, where from

the sewage trickles down on the filter medium.This ensures uniform distribution with alternate dosingand resting periods.

The sprinkling system is operated by a motor.

As the sewage/effluent passes through the filter, a sling Jelly film

called

“zoogleal layer”is formed over the filtering

medium, which will absorb the organic matter and oxidizeit with the help of aerobic bacteria.

This jelly like layer consists of living flora including algae,fungi, protozoa, planktons, diatoms, aerobic bacteria etc.

as the organic matters are oxidized, nitrification takesplace.

The intermittent application of sewage permits good



pp g p gcirculation of air through the bed during the rest period,

thus encouraging the growth of aerobic organisms.The oxidized sewage which leaves the trickling filter

is passed on to secondary sedimentation tank for further treatment.

These filters practically require no attention.

It is cheaper, more efficient and requires less



ii. Intermittent contact beds:

These are also watertight, rectangular shaped, masonry tanks, filled with

granular materials like gravel, crushed stones, bricks, etc up to a depth of about 2 meters.

Drainage pipe is placed at the bottom of the bed, drains the effluent.

The sewage after preliminary treatment or effluent from the septic tank isdistributed over the bed and allowed to remain for a fixed period of about 6hours.

During this time the aerobic bacteria convert the nitrogenous matter intonitrates.

A working period of 6 hours is interrupted by a rest period of another 6hours.

Th th filt b d i l d d t i d il ith



Thus the filter bed is loaded twice daily with sewage.

During the rest period, the bed is emptied, air comes in and the bed is re-aerated. This should be done within half an hour.

A series of contact beds is needed to allow intermittent use of beds withoutcausing interruption in the process of sewage treatment.

The effluent from these beds is not as good as that from the trickling filtersbecause it contains considerable suspended solids.

Another disadvantage of contact bed is that it needs the services of an operator and needs number of such persons. Such contact beds are used now adays.

iii. Intermittent sand filter : A bed of sand,

supported by earth embankments and an under drainage system is also used for the purpose. Thesewage is intermittently spread on the surface of the sand bed by distribution pipes lying inside the

earth embankment. Two loadings of sewage, of about 10 cm thickness, are permitted in a 24 hour cycle with intervening rest period, during which thesewage is fed to other beds As it passes through



sewage is fed to other beds. As it passes through

the sand – bed, there will be nitrification of thesewage by the aerobic bacteria. The effluent isreasonably fit to be discharged into a natural water course. The beds become clogged after several

months of use. It is the time to scrape off theaccumulated deposit over the sand bed and thesand is loosened by racking. The beds become fit

b. Bioaeration:

This is also called as “Activated sludge process”.

This is the most modern method and satisfactory

method of purifying the sewage, better than trickling filter method.



The bioaeration plant consists of two chambers,

a mixing chamber, in which the sewage coming after

preliminary treatment is mixed with “activated sludge” (or return sludge) obtained from the secondary sedimentation,tank, in the ratio of 70:30% and then let into the nextchamber i.e. aeration chamber, where it is subjected tocompressed air aeration for a period of about 6 hours, from

the bottom of the tank. Aeration is continued till all theammonia of the sewage is oxidized into nitrates. Aeration isthen stopped and allowed to settle. The settled sludge iscalled “Activated sludge” or “Aerated sludge”.



It differs from the sludge of primary sedimentation tank in that it

is inoffensive and is an aerobic “bacterial culture”, whichis not only employed in activated sludge process but also hasa high manure value.

The purification of sewage occurs in two stages.

During the first stage, organic matters are broken down and

carbon is converted into CO2. the liquid becomes more or less stable.

During the second stage, nitrates are formed.

Advantages of Activated Sludge Process

The effluent is fully oxidized; it is clear and

free from colloids.

Purification is rapid and perfect.

The system is free from smell and flies.



The sludge is inoffensive and has high

manure value.

Only a small area of land and a skilled

attendant is enough to manage the work.

Secondary Sedimentation

The effluent coming from the trickling filter or aeration chamber isdirected to secondary sedimentation tank, where it is detained

for about 3 hours.

The sludge that collects at the bottom of the secondary

sedimentation tank is fully aerated and practically inoffensive,rich in bacteria, nitrogen and phosphates, thus differing from

the sludge of primary sedimentation tank which is

ff i



highly organic and offensive.

Desludging of the tank is done periodically to avoidinterference in the process of sedimentation.

The sludge of the secondary sedimentation tank if dehydrated,

becomes manure.

Part of it is pumped back into aeration tank for activated sludge process and the rest is pumped into

sludge digestion tanks for further treatment and disposal (i.e. for

The effluent leaving the secondary

sedimentation tank is inoffensive and fullystabilized. It is almost free from suspended

impurities and does not show putrefactive

changes even on long storage. Its BOD isreduced to minimum. But still it is better to

chlorinate it and let into water course.



Since the river water is used for drinkingpurposes, the BOD of the effluent should be

lesser than 30 ppm and

5 day BOD should be less than 20 ppm,

according to Royal Commission of England.

Sludge Digestion

The sludge obtained from primary and secondary

sedimentation tanks consists of 95% water.

It is a thick, black mass with a revolting odour and is apotential source of nuisance.



It is therefore further rendered innocuous by appropriate

treatment with the help of anaerobic bacteria.

The sludge digestion is carried out in a cylindrically shapedconcrete tank with a hopper bottom and a leak-proof cover. The tank is provided with heating arrangement inthe form of hot water circulating coils, a mixingarrangement in the form of propeller pump, a gascollecting arrangement in the form of floating cover with

a central gas dome and a disposal arrangement in theform of liquor and sludge outlets.

In this tank, the sludge is incubated at favorablediti f t t d H Th l d



conditions of temperature and pH. The sludge

undergoes anaerobic autodigestion (i.e. liquefaction)and water is removed. Solid, liquid and gaseous endproducts are formed.

The solid product is called digested sludge.

It settles at the bottom. It is an innocuous granular massi.e. it is inoffensive, sticky, tarry mud which is removedand on drying becomes an excellent manure and is used

The liquid product is called tank liquor , which is

removed at various levels of the tank via liquor outlets. It is returned to the sludge treatment

plant ahead of the primary sedimentation tank.

The gaseous product is composed of 65%methane, which is used for heating and lighting

purposes 30% CO and other gases

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