Download - Environment & Health
-
7/28/2019 Environment & Health
1/185
ENVIRONMENT & HEALTH
ENVIRONMENT & HEALTH
* We are surrounded by various living & non- living things, that includesmaterials as well as non- materials.
our environment comprises of:
* Physical Environment :
-
7/28/2019 Environment & Health
2/185
* Biological Environment
*Social Environment
* Cultural Environment
contd.
i) Physical Environment
This consists ofnon living things like;
water, air, soil, housing, radiation, light, noise, vibration, refuse and other
wastes
ii) Biological Environment :
This consists ofliving things ofanimal & plant origin like; rodents, insects,
microbes ( bacteria, virus, rickettsiae, parasites, fungi )
-
7/28/2019 Environment & Health
3/185
iii) Social Environment
consists of occupation, literacy, income, religion, standard of living, life
style, availability of health services.
iv) Cultural Environment
Consists of knowledge, attitude, beliefs, practices, traditions, culture,
customs, habits.
WATER
* Water is essentially required for life by all living organisms including plants.
* Water intended for human consumption should be safe andwhole some i.e.
i) Free from pathogens and
ii) harmful chemicals
iii) Water should be potable (acceptable) i.e.
pleasant to taste,
-
7/28/2019 Environment & Health
4/185
clear&
free from any colourand odour.
Contd.
A safe water with unpleasant taste or appearance may derive the consumer to
other less safe sources.
iv) Usable fordomestic purpose.
Water is said to be polluted or contaminated, if it does not
fulfill above criteria.
Water Requirement
Requirement of water depends upon climatic conditions, standard of living and
habits of people.
However, 150 200 Ltr of water per head(per capita) is considered adequate to
meet daily requirement of a urban citizen.
Uses of Water
* Domestic use
-
7/28/2019 Environment & Health
5/185
* Drinking
*Cooking
* Washing
* Bathing
* Flushing of Toilets
* Gardening etc
ii) Public purpose
* Cleaning streets
* Recreational
* Swimming pools
* Fountains
* Ornamental ponds
* Fire Fighting
* Public Parks
-
7/28/2019 Environment & Health
6/185
Water is essential for economic, social and cultural development of community.
It can eliminate diseases, promote development and improve quality of life.
Sources of water
i. Rain
ii. Surface water
* Impounding Reservoir
* Rivers & Streams
* Tanks, Ponds & Lakes
-
7/28/2019 Environment & Health
7/185
iii . Ground Water
* Shallow well
* Deep well
* Artesian well
* Tube well
* Springs
i. Rain wateris purest form of water
However, as rain water passes through the atmosphere, it picks up microbes
(pathogens) and also gases (SO2, CO2,NO2) emitted by power plants and
automobilesusing fossil fuel.
This results in acid rain.
Gibraltardepends upon rains as its source of water supply.
ii. Surface water:
* Rain, when comes to ground becomes surface water .
* Surface water gets contaminated from human and animal activities,therefore,
it is never safe for human consumption unless subjected to protection ,purification & treatment.
-
7/28/2019 Environment & Health
8/185
# Impounding reservoirs are artificially constructed lakes to store huge quantity
of water.
The area draining into these reservoir is called Catchment area.
* cities like Mumbai, Chennai, Nagpur derive their water supply from suchreservoirs.
* Purity of water in these reservoirs is good, it is next to rain water.
* However, prolonged storage leads to growth of algae and othermicroscopic organisms, which imparts bad taste & odourto water.
*If surrounding hills are covered with peat, the water may acquire brownishcolouration.
## Rivers
* Cities like Delhi, Allahabad, Kolkata derive water from rivers.
* River water is grossly polluted & unfit for drinking unless subjected totreatment.
-
7/28/2019 Environment & Health
9/185
* Rivers have been described as a direct connection between thealimentary canal of people living up steams and the mouth of those
staying down streams.
* Rivers derive impurities from sewage, sullage, Industrial & trade wastes.
iii. Ground water
* Rain water percolates down the earth and forms ground water.
* Ground water is superior to surface water
because strata of soil provides effective filtering media.
* However, mineral contents may behigh and vary from place to place.
This may render the water hard.
-
7/28/2019 Environment & Health
10/185
-
7/28/2019 Environment & Health
11/185
# 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.
-
7/28/2019 Environment & Health
12/185
#Springs
Whenground water comes to the surface and
flows freely under natural pressure, it is called spring.
Depending on the source, springs also may be
shallow or deep spring.
WATER POLLUTION
** Water during its course of flow picks up impurities
from the atmosphere, catchment area and the soil.
** In routine these impurities may not be dangerous,
however, more serious pollutions may be added by the human activities;
these include:
-
7/28/2019 Environment & Health
13/185
* Sewage
*Industrial & trade wastes
* Agricultural pollutants
* Physical pollutants
Water and Disease
WHO estimates that as much as 80 per cent of all diseases in the world are
associated with water.
-
7/28/2019 Environment & Health
14/185
These diseases can be grouped as under:
Sewage pollution
Industrial pollution
Hazards from pipe material
Effects of soil contents
Hardness of water
Diseases due to shortage of water
Other pollutants
fertilizers and pesticides
radioactive substances
.
ii. Industrial pollution
-
7/28/2019 Environment & Health
15/185
Numerous known and unknown toxic chemicals are being discharged into water
courses along with many industrial wastes.
Poly Aromatic Hydrocarbons ( PAH) are carcinogenic.
Certain metals like mercury, arsenic, cadmium, cyanide, lead, selenium,
manganese, copper, etc., are harmful and their concentration should not
exceed maximum permissible levels.
.
iv. Effects of soil contents
Fluorides and iodine contents of soil can also affect the health through drinking
water.
Fluorosis, a crippling disease of the skeletal system is due to the excessive
intake of fluorides through water.
It is a public health problem in some areas of the Punjab, Andhra Pradesh and
certain other states.
-
7/28/2019 Environment & Health
16/185
Whereas deficiency of fluorides has been associated with high incidence of
dental caries.
Iodine deficiency in may result in Goitre
vi. Diseases due to shortage of water
* Certain diseases result from chronic water shortage. Incidence ofscabies andtrachoma is high under these situations.
These diseases flourish under poor hygienic standards.
* vii. Other pollutants
= fertilizers and pesticides used in the field of agriculture is one such group.
= Much more serious pollution can result from
radioactive substances, (Uranium in Bhatinda belt,
Thorium in Kerala)
which have carcinogenic and genetic effects
-
7/28/2019 Environment & Health
17/185
PURIFICATION OF WATER
Purification of water may be carried out:
i. On large scale i.e. for community
ii. On small scale i.e. for domestic purposes
i. Purification of water on large scale
The treatment to be employed depends upon :
- the nature of raw water, and
- standard of water quality desired.
For example ,
Ground water(wells, springs) may not need any treatment
except Disinfection,
where as Surface water(river) which tends to be turbid & polluted
requires extensive treatment.
-
7/28/2019 Environment & Health
18/185
* The water purification plant comprises of one or more of the followingcomponents :
i) Storage
ii) Filtration
iii) Disinfection
i) STORAGE
water drawn from the source is stored in naturalorartificialreservoir.
Storage provides natural purification in the form of
Physical,
Chemical, and
Biological contents of water :
(a) Physical: By mere storage, the quality of water improves.
About 90 per cent of the suspended impurities settle down in
24 hours by gravity.
-
7/28/2019 Environment & Health
19/185
The water becomes clearer.
This allows penetration of light, and reduces the work load on the filters,
(b) Chemical:
.
The aerobic bacteria oxidizes the organic matter present in the water
with the help of dissolved
oxygen.
As a result, the quantity of free ammonia is reduced ,
and there is rise in nitrates .
(c) Biological:
1. A tremendous drop in bacterial count takes place during storage.
2. The pathogens gradually die out.
# It is found that when river wateris stored, the total bacterial count drops by as
much as 90 per cent in the first 5 -7 days.
This is one of the greatest benefits of storage.
-
7/28/2019 Environment & Health
20/185
## The optimum period of storage of river water is considered to
be about 10 14 days.
# If the water is stored for long periods, there islikelihood of development ofvegetable growths such as algae which impart a
bad smell and colourto water.
(ii) FILTRATION
Filtration is the second stage in the purification of water, and quite an important
stage because
98 99 per cent of the bacteria are removed by filtration, apart from other
impurities.
Two types of filters are in use,
- the biological or slow sand filters and - the rapid sand or
mechanical filters.
a) SLOW SAND or BIOLOGICAL FILTERS
Slow sand filters were first used for water treatment in 1804 in
Scotland and subsequently in London.
During the 19th century their use spread throughout the world.
Even today, they are generally accepted as the standard method of
water purification.
-
7/28/2019 Environment & Health
21/185
Elements of a slow sand filter
elements of a slow sand filter consists of:
* i. Supernatant (raw) water
* ii. A bed of graded sand
* iii. An under-drainage system; and
* iv. A system of filter control valves
1. Supernatant water
The supernatant water above the sand bed,
whose depth varies from 1 to 1.5 metre,
serves two purposes:
* Firstly,it provides a constant head of water
so as to overcome the resistance of the filter bed and
thereby promote the downward flow of water through the sand bed; and
-
7/28/2019 Environment & Health
22/185
**secondly, it provides waiting period of some hours (3 to 12 hours, depending
upon filtration velocity) for the raw water, wherein, it to undergo partial
purification by
sedimentation,
oxidation &
particle agglomeration.
## The level of supernatant water is always kept constant.
2. Sand bed
* # The most important part of the filteris the sand bed.
* The thickness of the sand bed is about 1 metre.
*The sand grains are carefully chosen so that they are preferably
rounded and have an effective diameter between 0.2 and 0.3 mm.
* The sand should be clean and free from clay and organic matter.
-
7/28/2019 Environment & Health
23/185
* The sand bed is supported by a layer of graded gravel, 30 40 cm deepwhich also prevents the fine grains being carried into the drainage pipes.
# The sand bed presents a vast surface area; one cubic metre of filter sand
presents some of 15,000 sq. metres of surface area.
*Water percolates through the sand bed very slowly
(a process taking two hours or more), and as it does so,
it is subjected to a number of purification processes :
* i. mechanical straining,
* ii. sedimentation,
* iii. adsorption,
* iv. oxidation and
* v. bacterial action, all playing their part.
# The designed rate of filtration of water normally lies between
0.1 and 0.4 m3 / hour/per square metre of sand bed surface.
Vital layer:
-
7/28/2019 Environment & Health
24/185
-
7/28/2019 Environment & Health
25/185
3. Under drainage system
At the bottom of the filter bed is the under drainage system.
It consists ofporous or perforated pipes,
which serve the dual purpose :dual purpose :
i. providing an outlet for filtered water, andii. supporting the filter medium above.
Once the filter bed has been laid, the under drainage system cannot be seen.
4. Filter control
The filter is equipped with certain valves and devices which are incorporated in
the outlet pipe system.
The purpose of these devices is to maintain a constant rate of filtration.
* An important component of the regulation system is the Venturi meterwhich measures the bed resistanceor
-
7/28/2019 Environment & Health
26/185
loss of head.
When the resistance builds up, the operator opens the regulating valve so as to
maintain a steady rate of filtration.
* When the loss of head exceeds 1.3 metre it is uneconomical to run thefilter.
Filter cleaning: Normally the filter may run for weeks or even months without
cleaning.
When the bed resistance increases to such an extent that the regulating valve
has to be kept fully open, it is time to clean the filter bed, since any further
increase in resistance is bound to reduce the filtration rate.
At this stage, the supernatant water is drained off, and the sand bed is cleaned by
scraping off the top portion of the sand layer to a depth of1 to 2 cm.
This operation may be carried out by unskilled labourers using hand tools or by
mechanical equipment.
After several years of operation, and say 20 to 30 scrapings, the thickness of the
sand bed is reduced to about 0.5 to 0.8 metre.
Then the plant is closed down and a new bed is constructed.
-
7/28/2019 Environment & Health
27/185
The advantages of a slow sand filterare:
1. simple to construct and operate
2. the cost of construction is cheaper than that of rapid sand filters
3. the physical, chemical and bacteriological quality of filtered water
is very high.
* When working ideally, slow sand filters have shown to
reduce total bacterial count by 99.9 to 99.99 per cent and
E.coli by 99 to 99.9 per cent.
b) RAPID SAND or MECHANICAL FILTERS
In 1885, the first rapid sand filters were installed in the USA.
-
7/28/2019 Environment & Health
28/185
Rapid sand filters are oftwo types,
the gravity type (e.g. Patersons filter) and the pressure type
(e.g. Candys filter).
Both the types are in use.
The following steps are involved in the purification of water by rapid sand filters:
1. Coagulation: The raw water is first treated with a chemical coagulant such as
alum, the dose of which varies from 5 40 mg ormore per litre, depending
upon the turbidity, colour, temperature and pH of water.
2. Rapid mixing: The treated water is then subjected to violent agitation in a
mixing chamber for a few minutes. This allows a quick and thorough
dissemination of alum throughout the bulk of the water, which is very necessary.
3. Flocculation: The next phase involves a slow and gentle stirring of the treated
water in a flocculation chamber for about 30 minutes. The mechanical
type of flocculation consists of a number ofpaddles which rotate at 2 to 4 rpm
with the help of motors. This slow and gentle stirring results in the formation of a
thick, copious, white flocculent precipitate ofaluminium hydroxide.
Thicker the precipitate or flock diameter,
greater the settling velocity.
4. Sedimentation: The coagulated water is now led into sedimentation tanks
where it is detained for periods varying from
2 6 hours when the flocculent precipitate together with impurities and bacteria
settle down in the tank.
-
7/28/2019 Environment & Health
29/185
-
7/28/2019 Environment & Health
30/185
-
7/28/2019 Environment & Health
31/185
*The whole process of washing takes about 15 minutes.
* In some rapid sand filters, compressed airis used
as part of the back washing processes.
Advantages
The advantages of a rapid sand filterover the slow sand filter are:
1. rapid sand filter can deal with raw water directly.
2. No preliminary storage is needed
3. the filter beds occupy less space
4. Filtration is rapid, 40 50 times that of a slow sand filter
5. the washing of filter is easy
6. there is more flexibility in operation
-
7/28/2019 Environment & Health
32/185
Comparison between Rapid and Slow sand filters
(III) DISINFECTION
In water works ,
the term disinfection is synonymous with chlorination.
# CHLORINATION
Chlorination is one of the greatest advances in water purification.
* It is supplement,
not a substitute to sand filtration.
Mechanism of Action of chlorine:
-
7/28/2019 Environment & Health
33/185
* When chlorine is added to water,
there is formation ofhydrochloric acid and
hypochlorous acids.
*The HCl is neutralizedby the alkalinity of the water.
*The hypochlorous acid ionizes to form hydrogen ions and hypochlorite ions,
as follows: -
H2O + Cl2 = HCl + HOCl
HOCl = H + OCl
*The disinfecting action of chlorine is
mainly due to the hypochlorous acid, and
to a small extent due to the hypochlorite ions. *
The hypochlorous acid is more effective (70 80 times) than the hypochlorite
ion.
-
7/28/2019 Environment & Health
34/185
Principles of chlorination:
The mere addition of chlorine to water is not chlorination.
There are certain rules which should be followed to ensure proper chlorination:
1, Firstly, the water
should be clear and freefrom turbidity.
Turbidity impedes efficient chlorination
cond
3. Thirdly the contact period. The presence of free residual chlorine for a contact
period of at least one houris essential to kill bacteria and viruses.
-
7/28/2019 Environment & Health
35/185
It should be noted however, that chlorine has no effect on spores, protozoal cysts
and helminthic ova, except in higher doses.
4. the minimum recommended concentration offree chlorine is 0.5 mg / Ltr after
one hour.
The free residual chlorine provides a margin of safety against subsequent
microbial contamination as may occur during storage and distribution.
5. The correct dose of chlorine is the sum of the chlorine demand of the specific
waterplus the free residual chlorine of 0.5 mg / Ltr .
METHOD OF CHLORINATION
For disinfecting large bodies of water, chlorine is applied either as
1. chlorine gas or
2. chloramines or
3 Perchloron
1. Chlorine gas is the first choice, because I
it is cheap,
quick in action, efficient and easyto apply.
-
7/28/2019 Environment & Health
36/185
Since chlorine gas is an irritant to the eyes and is poisonous, a special equipment
known as chlorinating equipment is required to apply chlorine gas to water
supplies. Patersons chloronome is one such device for measuring, regulating
and administering gaseous chlorine to water supplies.
BREAK POINT CHLORINATION
Breakpoint chlorination is the point at which the chlorine demand is met.
If chlorine is added beyond the break point, it remains in the free state as free
chlorine (or free residual chlorine; FRC).
STEPS
1.As the chlorine is added itcombines with ammonia
to form chloramines.
This is Combined Residual Chlorine ( CRC )
This is also bactericidal.
The peaking coincides with the oxidation ofall organic matters.
2. Addition of further chlorine,oxidizes ammoniacal compounds.
3. Addition of next increments ofchlorine
results in destruction of chloramine,
resulting in the release of Free Residual Chlorine.
( FRC )
-
7/28/2019 Environment & Health
37/185
Contact period:
* it is the period (time) required for the chlorine to disinfect the water.
* For optimum disinfection, the presence of free chlorine for a contact period ofone houris essential.
* The free chlorine that remains at the end of one hour is called Freeresidual chlorine (i.e. after breakpoint chlorination).
* The minimum concentration of free residual chlorine for drinking purposes (indrinking water) should be 0.5 mg per litre. (i.e. 0.5 ppm = part per million of
water)
(1 mg of chlorine in 1 litre of water provides 1 ppm concentration of chlorine).
* The purpose of providing free residual chlorine in the drinking water is toprovide a margin of safety against further contamination of water which is
likely to occur during storage and distribution.
-
7/28/2019 Environment & Health
38/185
* Super chlorination:
This is a process of chlorination, wherein double the usual dose of chlorine is
added to water, so as to get FRC of more than 2 ppm at the end of contact
period.
This is resorted to when the water is heavily contaminated or when there is
threatening outbreak of water borne epidemic.
But the disadvantage is that such super chlorinated water has the smell of chlorine
and it irritates nose, throat and eyes. Therefore, super chlorination is followed
by de chlorination.
* De chlorination: This is removal of excess of chlorine and is carried out by
addition ofreducing substances such as sulphur dioxide, sodium sulphite,
sodium bisulfphite, sodium thiosulphate or activated carbon. FRC is
reduced to less than 2 ppm.
For effective chlorination ,
the pH of the water should be maintained between 7.2 and 7.6. Under no
circumstances it should be allowed to fall below 7 or
to exceed 8.
-
7/28/2019 Environment & Health
39/185
when the pH is less than 7,
sodium carbonate is added and
when it is higher than 8,
Hydrochloric acid is added.
In either case only small quantities are added periodically at hourly intervals until the
correct pH is obtained.
ORTHOTOLUIDINE (OT) TEST
* Orthotoluidine test detects both
free and combined chlorine in water. The test was
developed in 1918. the reagent consists of analytical grade O toluidine,
dissolved in 10 per cent solution of hydrochloric acid.
* The apparatus used is called Chloroscope.
* When the reagent is added to water containing chlorine,
it turns yellow and the intensity of the colourvaries with the concentration of
chlorine.
* The reagent reacts with free chlorine within 10-15 seconds ,
-
7/28/2019 Environment & Health
40/185
* while combined chlorine reacts slowly and yellow colour appears and deepens in
15 to 20 minutes.
The test is carried out by adding 0.1 ml of the reagent to 1 ml of water.
The yellow colour produced is matched against suitable standards or colour discs.
Commercial equipment ( Chloroscope ) is available for this purpose. It is
essential to take the reading within 10 seconds after the addition of the reagent
to estimate free chlorine in water. The colour that is produced after a lapse, say
15 20 minutes, is due to the action of both free and combined chlorine
.ORTHOTOLIDINE-ARSENITE (OTA) TEST
# This is a modification of the OT test
to determine free and combined chlorine separately.
## Further, the errors caused by the presence of interfering substances such
as nitrites,
iron and
manganese all of them produce yellow colourwith o
tolidine, are overcome by the OTA test.
-
7/28/2019 Environment & Health
41/185
# Chlorine continues to be the most commonly used sterilizing agent because of its
germicidal properties and the comparatively low cost and ease of application, its
pre-eminence in water disinfection is being seriously challenged because of the
discovery that chlorination of water can lead to the formation of many
halogenated compounds, some of them are either knownorsuspected carcinogens.
a) OZONATION:
Theprocess involves, passing ozonized air through the water.
* Ozone is a relatively unstable gas.
* It is a powerful oxidizing agent.
* It destroys the pathogens including viruses and
also destroys the phenolic compounds which produces
undesirable odour, taste and colour, and
* removes the entire chlorine from the water.
Most importantly, ozone has a strong virucidal effect.
It inactivates viruses in a matter of seconds , whereas minutes are required
to inactivate them with either chlorine or iodine.
This has prompted many municipalities to consider ozone for potable water
treatment.
More than 1000 municipal water treatment plants around the world are using
ozone, the oldest of these is in France, which has been in operation since
1906.
-
7/28/2019 Environment & Health
42/185
# Drawback of ozone is that it has no residual germicidal effect.
# The current thinking is that ozone should be used as a pre treatment of
water to destroy viruses and bacteria, and also organic compounds that
are precursors for undesirable chloro organic compounds that are formed
when chlorine is added.
# A carefully controlled minimum dose of chlorine is added to the water before
water is pumped into the distribution system.
# Thus ozone is usually employed in combination with chlorine.
# In this combined treatment, the two methods complement each other taking
advantage of the best features of each.
# The ozone dosage required for potable water treatment varies from 0.2 to 1.5
mg per litre.
(b) ULTRAVIOLET IRRADIATION:
# Germicidal property of UV rays have been recognized for many years.
-
7/28/2019 Environment & Health
43/185
UV irradiation is effective against most microorganism known to contaminate
water supplies including viruses.
# The method of disinfection involves the exposure to a
film of water, up to about 120 mm thick,
to one or several quartz mercury vapour arc lamps emitting ultraviolet
radiation at a wavelength in the range of 200 to 295 nm applications are
limited to individual or institutional systems.
# For efficient disinfection water should be free from turbidity and
suspended or
colloidal constituents.
## The advantages are that the exposure is forshort period,
* no foreign matter introduced,
* no taste and
* no odour produced.
-
7/28/2019 Environment & Health
44/185
Overexposure does not result in any harmful effects.
## The disadvantages are that no residual effect is available and there is a lack of
a period field test for assessing the treatment efficiency;
moreover, the apparatus needed is expensive.
Purification of Water on Small Scale
* Household purification of water
** Disinfection of wells
A. Household Purification of Water
Household purification of water is by three methods Physical, Chemical and
Mechanical.
* Physical methods: These are Boiling,
ozonation and
ultraviolet irradiation.
-
7/28/2019 Environment & Health
45/185
* Chemical methods: The different chemical substances employed
for purification of water for domestic use are Chlorine,
Iodine and
potassium permanganate.
* Mechanical methods:
This consists of using the ceramic filters, such as
Pasteur Chamberland filter,
Berkefeld filter,
Katadyn filter,
carbon and pad filter,
aqua guard and
reverse osmosis treatment.
The essential part of the first three filters, is called Candle, or Tube, which ismade up ofporcelain in the
P C filter and ofkieselgurh or infusorial earth in the Berkefeld filter and a coat of
silver catalyst on the candle in Katadyn filter.
AQUA GUARD domestic filter
This purifies the water in three stages:
i. It filters physical impurities
(i.e. traps the dirt, mud and such other turbid impurities.)
ii. It removes the organic impurities
(thereby remove the colourand odour)
iii. Itinactivates the pathogens by U V treatment in the U V chamber.
-
7/28/2019 Environment & Health
46/185
## It has the in built electronic monitoring system whereby it monitors the
quality of purified waterand stops the flow ,
if the purification level falls below the predetermined levels.
* Reverse Osmosis treatment:
* Invention of this technique is a milestone in creation of drinking waterresource.
* Reverse osmosis is based on water reverse theory in nature.
* NASA in US first applied this theory in purifying the astronaut's urine as aresource for drinking water in space.
-
7/28/2019 Environment & Health
47/185
* In this process, water is purified in 5 stages as follows.
Stage 1: 5 u sediment filter.
This removessand, silt, dust and rust particles
(i.e. removes suspended impurities)
Stage 2: Activated carbon block filter
Removeschlorine, organic matter, and bleaches colour
(Removeschemical impurities).
Stage 3: GAC filter (Granular Activated Carbon)
Removesharmfulchemicals and
color, taste and odour producing substances
Disinfection of Wells
Wells constitute the main source of water supply in rural areas. Since most of the
wells are shallow wells, liable for contamination, need to be disinfected
periodically, more so during epidemics of acute gastro enteritis, cholera, etc.
Wells are best disinfected by bleaching powder.
-
7/28/2019 Environment & Health
48/185
The various steps of disinfection of wells are
* Finding the volume of water in the well
* Estimating the quantity of bleaching powder required
* Preparation of the chlorine solution
* Delivery of the chlorine solution
* Contact period
* Orthotoludine test
a. Finding the volume of water:.
* If it is rectangular well. The formula is I X b X h X 1000 = X litres
* if it is circular well, by using the formula
3.14 X d2 X h
4
The volume is expressed in cu. Metres. I cu metre 1000 litres.
-
7/28/2019 Environment & Health
49/185
Volume of water in cubic metres X 1000
= X litres
* Which is derived from
r2 h, where = 22 / 7 = 3.14
r= radius of well in mtrs.
= half of diametre
= d / 2
r2
= d/2 X d/2 = d2
/ 4
h= height of water column in metres.
Where I = length of well in mtrs.
b= breadth of well in mtrs.
h= height of water column in mtrs.
b. Estimation of quantity of bleaching powder required:
The quantity of bleaching powder required to disinfect a particular well can be
estimated by using Horrocks apparatus.
Horrocks Apparatus
Contents:
* 6 white cups, each of 200 ml capacity,
-
7/28/2019 Environment & Health
50/185
* 1 black cup with a white circular margin inside, near the brim,
*2 metal spoons, each level spoonful holds 2 gm of bleaching powder,
* 7 glass stirring rods,
* 1 special pipette,
* 2 droppers,
* Starch Iodide indicator.
Procedure
Preparation of stock (standard) chlorine solution:
One level spoonful (2 gm) of bleaching powder is taken in the black- cup and
made into a thin paste by adding little water. Then more of water is added
gradually and stirring till the level reaches the white circular mark. It is stirred
well and allowed to settle, so that calcium of the bleaching Powder settles
down. This is the stock chlorine solution.
Procedure :
* All the six white cups are now filled with water from the well , to be tested forbleaching powder estimation up to a cm below the brim.
-
7/28/2019 Environment & Health
51/185
* With the help of the pipette, one drop of stock chlorine solution is added tofirst white cup, two drops to second cup, three drops to third cup, andso on
and six drops to sixth cup.
* The water in each cup is stirred well with separate stirrers for each cup.
* Wait for half an hourfor the action of chlorine in the water (Chlorination).
* Thenthree drops of Starch iodide indicator is added (Starch Cadmium /Potassium iodide) for all the six cups and stirred again.
* Development ofblue color indicates the presence of free residual chlorine.
The intensity of the blue color is directly proportional to the quantity of free
residual chlorine in the water suppose the first cup shows distinct blue
colorfirst, the intensity of color increases subsequently in second, third, fourth,
fifth and sixth cups.
Mechanism: When chlorine solution is added to the white cups, it is utilized by the
organic and ammonical substances for oxidation purposes. Once the oxidation
process is over, free chlorine is left. This is acted upon by starch Cadmium /
Potassium- iodide, resulting in the formation of Cadmium / Potassium chloride
and iodine is set free, which then acts upon the starch giving rise to blue color.
So development of blue color indicates the release or presence of free
residual chlorine in that cup.
Suppose blue color is not obtained even in 6 th cup, the first cup is considered as 7 th
cup and counted subsequently as 8 th, 9th, 10th cup and so on and the test is
continued by adding chlorine solution, 7 drops, 8 drops, so on respectively to all
the remaining cups (i.e. 6 drops to each of the cups in second round).
-
7/28/2019 Environment & Health
52/185
The first cup showing distinct blue color is noted. That cup number indicates
the number of level spoonfuls of bleaching powder for disinfecting 455 liters ofwater, so as to give 0.5 ppm of free residual chlorine concentration.
Suppose 1st cup turn blue, then one (the number of the first cup showing distinct
blue color) level spoonful (or 2 gm) of bleaching powder is required to
disinfect 455 litres of water of that particular well, for simple or marginal
chlorination.
For X liters of water in the well, quantity of bleaching powder is estimated.
C. Procedure of Disinfection of Well
The estimated amount of bleaching powder is taken in a bucket and made into a thin
paste by adding little water. Then more of water is added till the bucket is three
fourths full. It is stirred well and allowed to sediment for one minute, so that
lime settles down. The supernatant chlorine solution is transferred to another
bucket and the chalk or lime is discarded and not poured into the well,
because it increases the hardness of well water.
The bucket containing chlorine solution is lowered into the well, below the surface
of the water and agitated vertically and horizontally, so that chlorine solution
mixes with the well water uniformly.
Then contact period of one hour is allowed before the water is drawn for use.
To verify whether water has been properly chlorinated or not, orthotoluidine test is
done. If free residual chlorine level is less than 0.5 ppm after contact period ofone hour, the chlorination procedure should be repeated.
During the epidemics of water borne diseases, wells are super chlorinated everyday,
preferably twice a day, once in the early morning and once in the late afternoon
in case of heavily used wells.
-
7/28/2019 Environment & Health
53/185
Continuous Method of Chlorination
To ensure a constant dose of chlorine to the well water, under the circumstances of
epidemic of water borne disease, the National Environmental Engineering
Research Institute, Nagpur has recommended Double Pot Method (Double
jar diffusion method) of chlorination of wells.
This method consists of 2 cylindrical pots, one placed inside the other. The size of
the cylinders being 30 cm height and 25 cm diameter for the outer pot and 28
cm height and 16 cm diameter for the inner pot. Both the pots have an opening
on the side. The outer pot has an opening of about 1 cm diameter near the
bottom and the inner pot has the opening near the brim.
A mixture of 2 kg of coarse sand and 1 kg of bleaching powder is put in the
inner pot and moistened with water. It is then put inside the outer pot. The
surface is then closed with a polythene foil.
The double pot is then lowered into the well by means of a rope, for about 1 metre
below the water surface, to prevent the damage caused by the buckets used by
the public. The water from the outer pot enters into the inner pot, mixes with
bleaching powder mixture. The chlorine solution comes out slowly over a long
period of time, thus ensuring constant chlorination over a long period of about
15-20 days, for a well containing about 4500 liters of water, having a draw off
rate of about 400 ltr per day. After 15-20 days, it needs to be removed,
emptied, refilled and replaced for further chlorination.
Sanitation of Swimming Pool
-
7/28/2019 Environment & Health
54/185
The diseases transmitted through swimming pool water are
conjunctivitis,
sinusitis,
otitis media,
sore throat and
athletes foot.
Rarely diseases like typhoid, dysentery, vulvo vaginitis, trachoma have also
been traced.
All these diseases occur due to the contamination of the swimming pool
water from the skin, naso pharynx, urination by the users.
The regulations regarding the construction of the pool, its use, disinfection
procedures, and instructions to the users should be strictly adhered.
Sanitation Measures
* Construction: It should be away from the traffic and dusty roads.
* Area: it should be 2.2 sq m per person swimming.
* Water: There must be continuous circulation of water, coming out from deepend of the pool, passing through a purification plant, (where it undergoes
clarification, filtration and chlorination) and enters the pool from the
shallow end. The free residual chlorine is maintained at a level of about 0.5
ppm, as recommended for drinking water. More than 1.0 ppm of FRC results
in smarting of the eyes. The pH of water is maintained around 7.5.
-
7/28/2019 Environment & Health
55/185
The results of bacteriological examinations of samples of water taken from the inlet
and outlet of the purification plant, gives an indication of the effectiveness of the
water treatment. The bacteriological quality of water should be that of pure
drinking water.
About 15 - 20 percent of the water of the pool should be replaced by fresh
water every day in order to remove the nitrates, albuminoidal ammonia and
organic substances derived from the users, because they reduce the
effectiveness of chlorination. Entire water is changed once a week.
Maintenance / Cleanliness
For this purpose, following instructions are strictly enforced.
* No one with cutaneous lesions or discharges from body orifices should enterthe pool.
* Before entry into the pool, the user should empty the bladder and bowel, andclean the nose and throat.
* This is followed by thorough scrub bath with soap and water.
* After the bath, the user should dip his feet in foot bath (consisting of chlorinesolution) then only should enter the pool.
* Swimming costume should be worn.
*Once inside the pool, spitting, blowing of the nose, gargling, urination isforbidden.
-
7/28/2019 Environment & Health
56/185
* After leaving the pool, thorough bath should be taken again.
HARDNESS OF WATER
Definition
A hard water is a one which does not readily form leather with soap (In other
words, it is soap destroying quality of water).
Causes
The hardness of water is due to the presence of certain mineral salts in the water
such as bicarbonates, chlorides, sulphates and nitrates of calcium and
magnesium, which form insoluble, sticky precipitate with soap.
Types
There are two types of hardness of water. Temporary and Permanent hardness.
*Temporary (or carbonate) hardness is due to the presence ofbicarbonates ofcalcium and magnesium.
* Permanent (or non carbonate) hardness is due to the presence ofsulphates, chlorides and nitrates of calcium and magnesium.
Measurement
-
7/28/2019 Environment & Health
57/185
Hardness of the water is measured or estimated by using a standardized titrant,
Ethylene Diamine Tetra Acetic Acid (EDTA). The results are expressed as mg
of CaCO3 per litre of water, i.e. milli Equivalents per litre (mEq/L). 1 mEq / L of
hardness is equal to 50 mg of CaCO3 (calcium carbonate) (or 50 ppm) per
litre of water, as suggested by WHO in its International Standards ofDrinking Water.
Grading of Hardness of Water
* Less than 1 mEq/L (i.e., 300 ppm) It is very hard water. Drinking water shouldbe moderately hard (1-3 mEq/L). The question of softening the water arises if
the hardness exceeds 3 mEq/L.
The degree of hardness can also be measured by Clarks method. According tohim, the same four grades are expressed respectively as 30 percent.
The hardness of water is not only dependant on the geology of the region in which
the water is found but also by the pollution with sewage and many other wastes.
Limestone regions produce water containing considerable hardness. Granite
areas produce soft waters.
Advantages of Hard water
Recent studies have shown an inverse correlation between the hardness of water
supplied to the community and its cardiovascular mortality rate. The areas
supplied with soft drinking water showed a higher prevalence rate ofcardiovascular mortality rate proving that hard water is cardio -protective.
-
7/28/2019 Environment & Health
58/185
Disadvantages of Hard water
* It causes great wastage of soap
* It causes precipitation of carbonates and forms scales in the boilers, leading togreater fuel consumption, loss of efficiency and even explosions of boilers
resulting in industrial economic loss.
* It affects cooking adversely
* It causes irritation of skin and gastrointestinal system
* It reduces the life of clothes washed with soap in hard water.
Removal of Hardness
# Temporary hardness (due to carbonates and bicarbonates of Ca and Mg) can be
removed by processes like boiling of water,
addition of lime,
Sodium Carbonate and
Permutit process.
-
7/28/2019 Environment & Health
59/185
# Permanent hardness (due to chlorides and sulphates of Ca and Mg) can be
removed by last two processes,
i.e. by addition ofSodium carbonate and
by Permutit process. ( Base Exchange Process )
b. Addition of lime: For example, calcium hydroxide, when added to water,
absorbs carbon dioxide and precipitates insoluble calcium carbonates,
resulting in softening of water.
Meanwhile it accomplishes magnesium reduction.
Ca (OH)2+ Ca (HCO3)2 ---- 2CaCO3 + 2H2O
Ca (OH)2 + Mg (HCO3)2 ---- MgCO3 + CaCO3 + 2H2O
Ca (OH)2 + Mg CO3 ---- CaCO3 + Mg (OH)2
-
7/28/2019 Environment & Health
60/185
d. Permutit process: Synonyms are Ion exchange process; base exchange
process; zeolite softening. In this process both temporary and permanent
hardness are removed. Zeolite is a mineral consisting of sodium, aluminium and
silica. It is also called as sodium permutit (or sodium zeolite) Na2Z. When
this is added to hard water, the Ca and Mg ions exchange with Na2Z and formsCa and Mg permutit and the water is softened to zero hardness. The reaction
is as follows:
Ca (HCO3)2 Ca 2NaHCO3
Na2Z + SO4 ------------ Z + Na2SO4
Mg Cl2 Mg 2NaCl
Since the soft water of zero hardness has a corrosive propertyon pipes, so raw
water is again mixed to the soft water to secure the desired level of hardness,
i.e. 1 to 3 mEq/L.
WATER HARVESTING
CONSERVATION OF WATER RESOURCES
* Industrialization, urbanization and deforestation, and populationexplosion has resulted in the shrinkage of surface waters (rivers, ponds,
lakes etc). People are meeting their demand for water, by resorting to tapping
sub soil resources of water.
* This has resulted in alarming fall in the ground water resources mainlybecause of the dependency of irrigation on tube wells.
*Therefore , before it is too late, the underground water resources shouldbe conserved.
-
7/28/2019 Environment & Health
61/185
The term conservation means
* protection of water resources and
*further building up the reserves.
# Conservation has thus 2 components:
* Protection of Water Resources
This can be done by preventing the wastage of water.
This requires extensive education of the public, about the economical use of water
and to consume minimum requirement for daily use.
** Building up of Sub-soil Water Reserves
This is also called as Water harvesting.
This can be done by draining the rain water using PVC pipes, from top of the
buildings and courtyards into soaking pits or trenches, instead of drains,
followed by filtration using sand and gravel and then letting into existing tube
wells or wells.
Various economic designs have been suggested by agencies like UNICEF,
Central Ground Water Board, etc.
Ground Water set to be made Public Property
-
7/28/2019 Environment & Health
62/185
*Ground water, a precious natural resource, for all practical purposes isconsidered as private property in our country.
Any one can bore and extract water with few rules to restrict over-exploitation.
But this could soon change.
Plans are afoot to alter laws and regulations to make ground water a common
property resource, whereby communities will manage underground aquifers
and the Govt will regulate their use in the role of a public trustee.
A law that ensures that groundwater is treated as public and
not private property is long overdue.
Thus water will be treated like any other natural resources extracted from the
ground, like oil, gas and other minerals.
Presently, any one sinking a bore well on his or her territory is not tapping into water
only under his or her plot but from the common water table. (Times of India,
18 July 2012)
SANITARY ANALYSIS OF WATER
Information is obtained from two sources, i.e.,
* Field surveys of the water source and
-
7/28/2019 Environment & Health
63/185
**Laboratory examination report of the water samples.
Field Survey
This includes the collection of data on :
i. the natureandsource of water supply,
ii. likely sources ofwaterpollution,
iii. modeof filtration,
iv. mode of distribution
v. and such other information, as would be relevant from the sanitary point of
view.
-
7/28/2019 Environment & Health
64/185
Laboratory Examination of Water Samples
Examination indicates whether the collected sample of water contains harmful or
undesirable substances.
Collection of Sample of Water
The method of collection of sample and quantity requirement of water are different
for different types of analyses:
1. For routine physical, chemical and biological examination,
2 litres sample should be collected in a clean glass bottle,
recommended is WinchesterQuart bottle.
2. For Bacteriological analysis, 200 cc of water should be collected in asterile bottle, sterilized in an autoclave.
3. For Radiological analysis, polythene bottle is preferred.
Sampling Technique
The sample of water must be thoroughly representative of the water to be
analysed.
1. In collecting waterfrom a river, stream or lake, the sample should be obtained
from a mid stream and not too near the bank and the surface pollution
should be avoided, by placing the bottle well under the surface of the water.
2. If the water has to be collected from the taps, the water is allowed to run to
waste for a few minutes and then collected.
-
7/28/2019 Environment & Health
65/185
# Source of water, the temperature of the water at the time of collection, is also
recorded on the proforma.
## The bottle containing water sample is closed with stopper
and sealed.
## # It is sent preferably in an ice box to the laboratory for examination
purpose, shorter the time elapsing between collection and analysis, more
reliable are the results.
Laboratory Examination of water
This includes the following:
1. Physical examination
2. Chemical examination
3. Biological examination
4. Bacteriological examination
5. Radiological examination, and
6. Virological examination
.
1. Physical Examination of Water
This is done to determine the presence of those substances in the water which affect
the physicaloraesthetic quality of water, such as odour, taste, colourand
turbidity.
-
7/28/2019 Environment & Health
66/185
-
7/28/2019 Environment & Health
67/185
-
7/28/2019 Environment & Health
68/185
* Fluorides are usually present in higher concentration
in ground waters than surface water.
* Its concentration is closely related to dental and skeletal health.
* Excess fluoride level results in dental and skeletal fluorosis anddecreased level in the water results in dental caries. Therefore, fluoride in
water is often called as A Double Edged Weapon.
* The optimum concentration for drinking purpose is
0.5 to 0.8 mg / L (ppm)
but the upper permissible limit is 1.5 mg / L (1.5 ppm).
The methods recommended for estimation of fluorides in water are
* Colorimetric method, using zirconium alizarin reagent,
* Electrochemical method using Orion electrode.
* SPANDS colorimetric method.
ii. Nitrates and nitrites:
* Even though these are the naturally occurring ions of the nitrogen cycle, they areconsidered as the indicators of pollution in water.
-
7/28/2019 Environment & Health
69/185
* Maximum Recommended Limits in water are as under:
Nitrate ( as NO3 ) - 50 mg/Ltr
Nitrite ( as NO2 ) - 3 mg/Ltr (provisional)
* Because of the possibility of simultaneous occurrence of nitrate and nitrite in drinking water , the sum of the ratios of the concentration of each
to the guide line value should not exceed one . Guide line value for nitrates & nitrites in
drinking water is solely to prevent methaemoglobulinaemia, since bottle
fed infants of less than 3 months of age are most susceptible.
Concentration of nitrate Concentration of nitrite
---------------------------------------------------- + ------------------------------------ = < 1
Guide line value of nitrate Guide line value of nitrite
l
-
7/28/2019 Environment & Health
70/185
Substances affecting the potability of water
3. Biological Examination of Water
* This includes examination of water under the microscope for the presence ofmicroscopic substances (excluding bacteria) such as algae, fungi, protozoa,
ova, cyst, yeast, rotifers, crustacea, small worms, insect larvae, etc. which
are all collectively called asPlankton.
* These are responsible for the production of objectionable colour, odourand taste in the water.
* Therefore, their presence is an index of pollution or sewage contamination.
4. Bacteriological Examination of Water
-
7/28/2019 Environment & Health
71/185
# The bacteriological examination of water is a
very delicate and sensitive test fordetecting the contamination of waterby
sewageorhuman excreta.
# The bacterial indicator of contamination of water, is the coliform group of
organisms,
which consists of both faecal and non faecal organisms.
# The typical example of faecal coliform group is E.coli and non faecal coliform
is klebsiella aerogenes
(or Enterobacter aerogenes).
# Non faecal type is found in soil, fruits, leaves, grains, etc.
## The supplementary bacterial indicators
offaecal contamination are faecal Streptococci and
Clostridium perfringens.
These indicators also help in assessing the efficiency of water purification
processes.
## Because of the difficulty in differentiation
between fecal and non fecal coliforms ,
-
7/28/2019 Environment & Health
72/185
for all practical purposes ,
it is assumed that
all coliform group of organisms are of faecal origin, unless the
non faecal origin is proved.
Reasons for exclusively choosing the coliform organisms (specially E coli) as
an indicator of fecal pollution are:
1. They are present in large numbers in the human intestine
* A person excretes on an average about 200 400 billion of these organismsper day.
2. They can be easily detected by cultural method
as small as one bacteria in 100 ml of watercan be isolated.
* The methods for detecting other human intestinal organisms like salmonella,shigella, etc are complicated and time consuming.
3. They tend to live longer than pathogens
-
7/28/2019 Environment & Health
73/185
4. They have greater resistance to the forces of natural purification than other
pathogens.
* If the coliform organisms are present in a water sample, the assumption is
the probable presence of intestinal pathogens.
* So consequently the assumption is justified , in that
if coliform organisms have been eliminated from water, the pathogens also
have disappeared.
# Faecal Streptococci
This is considered as a supplementary indicator of faecal pollution of water
because it also regularly occurs in faeces ,
-
7/28/2019 Environment & Health
74/185
but in much smaller numbers than E.coli.
Therefore, its presence in a water sample is considered as a confirmatory
evidence ofrecent faecal pollution of water.
## Clostridium perfringens
They also occur regularly in faeces but in smaller numbers than E.coli.
The spores of Cl. perfringens are capable of surviving for a longer period than
E.coli and are resistant to chlorine.
** Their presence in the absence of E.coli in a sample of watersuggests that
contamination had occurred at some remote time.
The bacteriological tests carried out are
* Plate count
* Standard tests
* Tests for the presence of fecal Streptococci and Cl. perfingens.
Interpretation of Results of Disinfected Water
-
7/28/2019 Environment & Health
75/185
*No coliforms in 100 cc. of water Excellent water
* 1 2 coliforms in 100 cc. of water Satisfactory water
* 3 10 coliforms in 100 cc. of water Suspicious water
* More than 10 coliform in 100 cc. of water Unsatisfactory water.
* However ,
there should be no E. coli in any 100 ml sample
5. Radiological Examination of Water
Pollution of water with radioactive materials
causes health hazard.
The radioactivity is expressed as micro micro curies (i.e. picocuries pci) per
liter of water.
1 pci = 2.22 radioactive disintegrations per minute.
-
7/28/2019 Environment & Health
76/185
WHO has proposed the following standards as acceptable upper limit.
Gross alpha activity = 3 pci / L.
Gross beta activity = 30 pci/L.
6. Virological Examination of Water
Enteroviruses, rheoviruses and adenoviruses have been found in water, enteroviruses are more resistant to chlorination.
If, Entero viruses are absent from chlorinated water,
it can be assumed that water is safe to drink.
An exponential relationship exists between the rate of virus inactivation and the
redox potential. A redox potential of 650 mV (measured between platinum and
calomel electrodes) will cause almost instantaneous inactivation of even high
concentration of virus. Such a potential can be obtained even with a lowconcentration of free chlorine of 0.5 mg / L for 1 hour, to inactivate the viruses.
WHO has fixed the upper limit for viruses as 1 PFU (Plaque Forming Unit) per
liter of water.
Primary Secondary
Treatment ( ANAEROBIC ) Treatment
( AEROBIC) CHLORINE
Sewage
-
7/28/2019 Environment & Health
77/185
Effluent
Disposal
Activated Sea Outfall
River Outfall
Sewage Farm
Sludge
Oxidation Pond Oxidation
Ditches
Alterna
te
Sludge to
digester Excess sludge
to
digester or
Excess sludge Return and excess sludge
thickener
-
7/28/2019 Environment & Health
78/185
AIR
and
VENTILATION
Air and Ventilation
INTRODUCTION
* Air constitutes the immediate physical environment.
* Life would not have existed without air .
## The public health importance of air is that
-
7/28/2019 Environment & Health
79/185
it is necessary forbreathing purposes,
cooling of the body,
hearing and
smelling
more importantly air acts as a
vehicle for transmission of diseases.
* Air is a mixture of gasses, mainly nitrogen (78%), oxygen (21%) and carbondioxide (0.03%), remaining are other gasses such as argon, neon, helium,
xenon, etc.
* Truly speaking, there is no pure air.
Air always contains foreign substances in the form of solid, liquid (moisture) and
gasses, at all times.
* Air is said to be polluted when it contains foreign substancessuch as dust,
bacteria,
spores,
-
7/28/2019 Environment & Health
80/185
gases in excessive concentration,
so as to affect the health of human beings and animals and causes damage to
plants and properties.
Changes in the Air Due to Human Occupancy
in the room are physical and chemical, and
also due to bacterial pollution.
1. The physical changes are:
i. Rise in the temperature due to release of body heat.
ii. Rise in the relative humidity due to expiration and perspiration.
iii. Decrease in the air movement.
iv. Occurrence ofunpleasant odours arising from expiration, perspiration, bad oral
hygiene,
dirty clothes and other sources.
-
7/28/2019 Environment & Health
81/185
EFFECTS OF VITIATED AIR
They are divided into acute and chronic.
# Acute effects are lassitude, head ache, nausea, vertigo, vomiting and evencollapse.
Death may occur in extreme cases.
## Chronic effects are anemia, debility, digestive disturbances, nutritional and
metabolic disorders, lowered vitality and decreased resistance to
infections.
**The workingefficiency is decreased and
** the output of the work falls.
The effects of vitiation of air was first observed by Sir Leonard Hill.
INDICATORS OF THERMAL COMFORT
i. Air Temperature
This alone is not adequate indicator.
-
7/28/2019 Environment & Health
82/185
ii. Air Temperature and Humidity
This is a better indicator than air temperature alone but still this is
unsatisfactory.
iii. Air Temperature, Humidity and Air movement
These three together is called Cooling Power of the air, which can be
measured by a device called Kata thermometer.
A dry kata reading of6 and above and
a wet kata reading of20 and above are regarded as an index of thermal comfort.
-
7/28/2019 Environment & Health
83/185
Kata thermometer
* Effective Temperature (ET)
It is the combined effect of
- air temperature,
- humidity and
- air movement (cooling power)
on the sensation ofwarmth orcold felt by the human body.
But this does not include the effect of radiation from the surrounding
structures.
McArdles Maximum Allowable Sweat RATE
-
7/28/2019 Environment & Health
84/185
It is recorded as
Predicted four hour sweat rate (P4SR).
It is the rate at which a person sweats in hot environment and is expressed for four
hours.
It is an indicator of heat stress.
The upper limit of P4SR is 3 litres.
Range is 1-3 Ltr, Average 2 litres
(i.e. A sweat rate of 2 liters in 4 hours in considered optimal for a man working in a
hot environment).
METEOROLOGY
INTRODUCTION
The components of meteorological environment are:
* Atmospheric pressure
* Air temperature
-
7/28/2019 Environment & Health
85/185
* Humidity
*Air movement(Air velocity)
(Directionandspeedof the wind)
ATMOSPHERIC PRESSURE
The instrument used to measure atmospheric pressure is called Barometer
Kew Pattern Station barometer is widely used. Others are Fortins Barometer,
Aneroid Barometerand Barograph.
Effects on Health
The influence of atmospheric pressure on health is considered under two headings.
* Effects ofdiminished atmospheric pressure.
* Effects ofincreased atmospheric pressure.
aneroid Barometer fortins Barometer
* Effects of Diminished Atmospheric Pressure
-
7/28/2019 Environment & Health
86/185
As we ascend atmospheric air becomes rarefied with diminished pressure and
oxygen contents.
For instance atmospheric pressure at Mumai is 760 mm of Hg,
at Leh(12000 ft.) it is less than 500, &
at Khardung La (18380 ft) it is less than 400.
Similarly, temperature also decreases roughly at the rate of 0.650C per 100 m
ascend till it reaches & stabilizes at minus 550 C.
# Effects of diminished atmospheric pressure are:
i. Acute Mountain Sickness
ii. High Altitude Pulmonary Oedema (HAPO)
iii. High Altitude Cerebral Oedema (HACO)
iv. High Altitude Pulmonary Hypertension
## Effects of diminished temperature are:
i. Chilblains
ii. Frost Bite
iii. Trench Foot
-
7/28/2019 Environment & Health
87/185
### Effects of solar radiation
i. On Skin
ii. On Eyes
* Effects of Increased Atmospheric Pressure
As we descend from sea level the atmospheric pressure increases at the rate of one
atmospheric pressure forevery 33 ft descent.
That is to say that at 33 ft descent the atmospheric pressure will be equivalent to
two atmospheric pressure (760 x 2 mm Hg) &
At 66 ft depth it will be equivalent to 3 atmospheric pressure (760 x 3 mm Hg)
# Increased atmospheric pressure causes:
i. Caissons disease
AIR TEMPERATURE
Measurement
Air temperature is recorded by using the following thermometers in Fahrenheitscale / centigrade scale.
-
7/28/2019 Environment & Health
88/185
a. Dry bulb thermometer: This is an ordinary mercurial thermometer, placed in
Stevensons screen to protect from, direct sun and rain, at a height of about
1.5 meters above the ground level. It records the temperature of the air.
b. Wet bulb thermometer: It is similar to dry bulb thermometer, except that the bulb
is kept wet by means of a muslin cloth, fed by water, from a bottle through
a wick.
As the water from the muslin cloth evaporates, the mercury column comes
down. Thus the wet bulb thermometer shows a lower temperature reading in
response to the heat lost by wet cloth through evaporation, than the dry bulb
thermometer.
Drier the air, lower the wet bulb reading.
If the wet and dry bulb thermometers record the same identical temperature,
it means the airis completely saturated with moisture, which is rare or never
occurs.
The difference between the dry and wet bulb thermometers increases with
increasing dryness of air and vice versa.
Stevensons screen
c. Maximum thermometer
d. Minimum thermometer
e. Sixs maximum and minimum thermometer
f. Vacuum or solar radiation thermometer
g. Terrestrial thermometer
h. Silvered thermometer
-
7/28/2019 Environment & Health
89/185
i. Globe thermometer
-
7/28/2019 Environment & Health
90/185
Globe thermometer:
This consists of a hollow sphere, made up of copper, 15 cm in diameter coated with
black paint on the surfaces.
The hollow sphere has an opening at the top through which a mercury thermometer
is inserted such that the bulb is in the center of the globe.
Due to globe, the thermometer absorbs radiant heat from the surroundings.
The globe thermometer records a higher temperature than the ordinary dry bulb
thermometer because it is affected by both the air temperature and theradiant heat of the surroundings.
Therefore, the difference between the reading ofthe globethermometerand the
ordinary dry bulb thermometer is a measure of the radiant heat.
*The globe thermometer is also influenced by the velocity of the airmovement.
Globe thermometer
HUMIDITY
Atmospheric humidity means the moisture content of the air, which in turn
depends upon the air temperature.
Lower the temperature of air, higher the moisture content (Humidity) and vice versa.
The temperature at which the moisture precipitates is called Dew point.
-
7/28/2019 Environment & Health
91/185
Humidity may be expressed as absolute humidity or relative humidity.
Absolute Humidity
It is the actual amount of moisture (or water vapor) in an unit volume of air.
It is expressed as grams per cubic meterof air.
Relative Humidity (RH)
It is the percentage of moisture present in the air, complete saturation being taken
as 100. Greater the relative humidity, the nearer the air to saturation.
This is more commonly employed to express the humidity.
# Even though humidity has no effect on the health of the individual, definitely it
has an effect on the comfort.
# If RH is more than 65 percent, air feels sticky and uncomfortable.
# RH can be lowered by ventilation.
# RH below 30 per cent over long period results in drying of nasal mucosa
predisposing for infection. Thus it is also uncomfortable.
# So the RH between 30 to 65 percent constitutes Comfort zone to the worker
in the working place.
-
7/28/2019 Environment & Health
92/185
Measurement
The humidity of the air can be measured by an instrument called Hygrometer, of
which there are 2 kinds namely Direct and Indirect hygrometers.
* Direct Hygrometers are Danniells Hygrometer,
Regnaults Hygrometer and
Dines Hygrometer.
**Indirect Hygrometers are
- dry and wet bulb hygrometers,
- Sling psychrometerand
- Assmann psychrometer.
Dry and Wet Bulb Hygrometer
This consists of two thermometers a dry bulb thermometer and a wet bulb
thermometer.
Both are alcohol thermometers, mounted side by side on a stand. The former
measures the air temperature. The latter is so called because the bulb is always
kept moist by covering with a thin muslin cloth, kept moist with water. So the
wet bulb reading is always lower than the other.
-
7/28/2019 Environment & Health
93/185
The difference between the two thermometer readings is referred to psychrometric
chart orslide rule and the relative humidity can be found.
Greater the difference, greater is the RH.
If both the readings are the same, it indicates that the atmosphere is cent percentsaturated with moisture, which never occur in reality.
For effective readings, the air should pass over the bulb with a speed of about 5
meters per second. The sling psychrometer achieves this when rotated rapidly.
Sling Psychrometer
This consists of 2 mercury thermometers dry and wet,
the latter bulb is covered with a thin muslin cloth and kept moist with water. Both the
thermometers are identical and mounted side by side on a wooden frame,
which is provided with a handle to whirl rapidly.
Principle: By rotating, both the bulbs are exposed to air at definite velocity.
Procedure: At the time of use, the muslin covering should be thoroughly saturated
with distilled water and the instrument is rotated orwhirled rapidly, at the rate
of 4 revolutions per second, so as to obtain a desirable air speed of5 meters
per second, for about 15 seconds, stopped and wet bulb reading is
noted.
This is repeated several times till the two successive wet bulb readings are
identical, showing that it has reached its lowest temperature.
Now the dry bulb reading is also taken, which is the true temperature of the air.
Sling psychrometer
-
7/28/2019 Environment & Health
94/185
The difference between the two readings (dry and wet bulb) is referred to the
psychrometric chart and the percentage of RH is obtained.
Greater the difference, greater is the RH.
# The difference between the two readings helps us to obtain - relative
humidity,
- dew point and
- vapor pressure of the air.
AIR MOVEMENT
The best instrument used to record the velocity of air and also the pressure of the
wind is Robinsons Wind Anemometer.
Anemometer
Wind direction
-
7/28/2019 Environment & Health
95/185
Rain gauze
AIR POLLUTION
Air pollution is a constant and menacing problem throughout the world, due to
mans own activities like industrialization and urbanization.
It is increasing continuously during the past few decades.
Air pollution is not only a public health problem but also an economic problem.
Air Pollutants
These may be physical, chemical orbiological.
1.Physical Pollutants
. Particulate matters: Dust, smoke, soot, sand, grit
2. Chemical Pollutants
Gases: CO, CO2, H2S, CH4, NO2, SO2,
Chloro Fluoro Carbons etc.
Metals: As, Be, Cu, Zn, Pb,
Carcinogens
2. Biological Pollutants
Pathogens (microbes), spores, etc.
-
7/28/2019 Environment & Health
96/185
Although the Earths atmosphere extends to several km above the surface, it is only
the first 30 km that hold the major portion of the atmospheric gases.
Man is concerned only with the first 8 10 km of the atmosphere.
FACTORS INFLUENCING Air Pollution
# Degree of air pollution is influenced by topography, i.e. atmospheric
temperature,
humidity,
atmospheric pressure and
air movement.
# Pollutants are also affectedby
sunlight and
temperature inversion.
Air Movement
-
7/28/2019 Environment & Health
97/185
Normally the air near the surface of the earth is warmerthan the air higher up.
So warmer air, being lighter, moves up, expands and becomes cool.
Thus the pollution is dilutedanddispersed,
while the air of the upper layerbeing cool and heavy,
comes down (turbulent flow).
* If Fog is present along with temperature inversion,
water vapor condenses around the smoke particles and forms Smog. (Water
vapor + Smoke = Smog).
Intense smog is lethal.
Such temperature inversion often persists for several days, resulting in acute
episodes ofrespiratory illness, suffocation and death.
Highly susceptible population groups are
young children,
-
7/28/2019 Environment & Health
98/185
elderly people and
those suffering from lung diseases and
heart diseases.
Sources of Air Pollution
i. Domestic : Burning of fire wood, kerosene oil, coal, etc.
ii. Industrial : Factories of iron and steel, paper, cement, fertilizers, thermal
power plant, petroleum refineries, etc.
iii. Automobiles: Motor vehicles, railways, ships,
aero planes, etc.
iv. Miscellaneous: Tobacco smoking, nuclear explosions, forest fires,
volcanoes, burning of refuse, dust storm, ocean spray, etc.
.
Hazards of Air Pollution
# Immediate and Acute Effects
These are due to photochemical oxidants.
-
7/28/2019 Environment & Health
99/185
These are irritation of conjunctiva, nose, throat and respiratory mucous membrane
resulting in conjunctivitis, allergic rhinitis, acute pharyngitis, acute
bronchitis and episodes ofbronchial asthma (acute attacks).
It may result in suffocation and death.
For example, London disaster in England and Bhopal gas tragedy in India
## Delayed and Chronic Effects
These are chronic bronchitis, bronchiectasis, emphysema, chronic
obstructive pulmonary disease (COPD), bronchial asthma and even lung
cancer.
Global Effects of Air Pollution
i. Acid rain:
* It is the end result of several processes occurring in the atmosphere.
* Sulphur dioxide emitted from combustion of coal produces sulphuric acid by
getting dissolved in water vapor of the atmosphere.
* Similarly carbon-dioxide produces carbonic acid and nitrogen dioxide
produces nitric acid.
* Thus the rainfall containing sulphuric acid, carbonic acid and nitric acid produces
devastating ecological effect by causing acidification ofsoilandwater.
* Trees killed by acid rain results in deforestation, desertification and erosion of
soil, thus disturbing the ecosystem.
* Acidification of water bodies destroys aquatic life including fish.
* Destruction of food crops effects food production also.
-
7/28/2019 Environment & Health
100/185
ii. Global warming:
It is a phenomenon occurring in the troposphere.
Normally, the atmospheric gases have a green-house effect, i.e. like the glass
of a green house,
allowlight andwarmth to reach the earth
but they do not allow warmthto be lost,
thus maintaining life on earth
## In air pollution,
there is rise in gases like carbon dioxide, methane and
chlorofluorocarbons and accumulation of ozone, they elevate
the global temperature
thusresulting in global warming and
affecting the ecosystem.
In the past 10 years, a rise of 0.3 to 0.6 degree Celsius has been noticed.
## Global Warming has resulted in following effects:
* Increase in the dryness of the climate
-
7/28/2019 Environment & Health
101/185
* Reduction in the world food production
*Melting ofpolar ice caps
* Rise in sea level and also resulting in floods
* Smog formation
* Increased incidence ofskin cancerand cataract
* Spread oftropical diseases to temperate regions.
iii. Effects of depleted ozone shield:
## Normallyozone layer of the earth, filters the harmful U-V rays of the sun
and prevents them from reaching the surface of the earth.
## Because of air pollution, ozone layer begins to thin out and results in thefollowing effects :
* Inhibitionof photosynthesis, (due to burning of leaves, retardation of growth of
plants, fall in the crop yield, ageing of plants etc, all due to air pollution).
* Disruption ofmarine food chain
* Impairment ofhuman immune mechanisms, predisposing for infections
* Ocular damage (cataract)
-
7/28/2019 Environment & Health
102/185
* Skin Cancers (melanotic and non melanotic)
* U-V rays also cause damage ofsmall forms of life such as plankton, pollen
grains and nitrifyingsoilbacteria.
iv. On animals: Cattle become weak and cachexic, Yield of animal products
become less.
v. Miscellaneous : (Socio economic hazards)
* Damage to buildings, like old monuments,
* Damage to metals, alloys, textile, rubber and works on wood, bronze andstone (like painting, carvings).
* Repair costs millions of rupees.
(thus time, money and energy are wasted).
-
7/28/2019 Environment & Health
103/185
* Air pollution index: it is an arbitrary index, considering one or more pollutantsas a measure of severity of pollution.
Example: (Employed in USA)
10 times SO2concentration, plus
twice CO concentration plus
twice the coefficient of haze.
It is considered as an alarming when this value becomes more than
50.
Prevention and Control of Air Pollution
By 3 measures:
i. Engineering technology
ii. Legislations and
iii. General measures.
i. Engineering technology:
a. Location of the industries: Industries must be located away from the human
habitations and where topography of the soil is favourable.
b. Replacement measures: Within the industries, the processes causing air
pollution should be replaced by the processes preventing air pollution.
For example: Using electricityinstead of fuels,
Using LPG (smokeless fuel) in the place of coal.
-
7/28/2019 Environment & Health
104/185
c. Containment measures: such as
* * Controlling the production of dust by wet method.
* * Prevention of the escape of dust into the atmosphere byusing enclosure hood,
* exhaust pipes for removal, and also
* * Increasing the height of smoke vent, etc.
*
.
iii. General measures:
* Control of traffic by construction ofby-pass roads.
-
7/28/2019 Environment & Health
105/185
**Maintenance of vehicles by periodical servicing, mixing of petrol and oil in
proper proportions,
use ofunleaded petrol to the vehicles,
fitting the catalytic converter to the exhausts pipes of four wheelers, whichconvert the harmful gas into harmless gas.
***Establishment of Green-belts, i.e. growing plants and trees between the
industries and the residential areas, so that the leaves absorb carbon
dioxide and give out oxygen.
****Health education of the people about hazards of air pollution and their role in
the prevention and control of air pollution.
*****Populationstabilization.
VENTILATION
Ventilation is not only the replacement of vitiated air (stagnant, warm and moist
air) by the drier, cooler and moving air but it also control the quality of
incoming air
so as to have adequate control over the temperature, humidity and purity with
a view to provide a comfortable environment without the risk of infection.
-
7/28/2019 Environment & Health
106/185
## Air change: For a person to get 3000 cu ft of air per hour and occupying a room
of 100 cu.ft. the air should be changed thirty times per hour or
if he occupies a room of 1000 cu.ft. air requires to be changed only three times.
This causes a disagreeable draught specially in cold weather. Otherwise it does
not cause any perceptible draught.
## Floor area:
This is an important standard of ventilation.
The optimum floor area per person in a house recommended is 50 100 sq. feet.
Lesser than 50 sq. feet results in over crowding favoring spread of droplet
infections.
In general hospital it should be 150 sq ft and
In infectious disease hospital, it should be 200 sq ft per person.
Systems of Ventilation
Mainly there are two systems of ventilation, namely Natural and Artificial, depending
upon the motive power, which originates them.
A. Natural ventilation: This depends upon 3 factors.
i. Perflation and aspiration of the wind.
ii. Difference of temperature
iii. Diffusion of gases.
-
7/28/2019 Environment & Health
107/185
Natural ventilation helps considerably, if the buildings are constructed with sufficient
open space around and by having large number of windows, preferably
opening direct into the outside air. Cross ventilation means perflation
between windows and other openings placed opposite to each other.
Naturally cross ventilation becomes impossible in back to back houses.
ii. Effects of difference of temperature:
Air always flows from high density to low density.
# Out side cool airis of high density, rushes in through every opening ofthe room
(or through the inlets placed at lower level).
Inside air of the room being of lower density moves up.
The greater the difference of temperature between the outer cooler air and the inner
warmer air, greater will be the velocity of the incoming air, until the temperature
of both outside and inside air becomes equal.
Since the incoming air gets warmed up, a constant current is maintained. This is the
basis of natural ventilation.
# The reverse process takes place in the tropics, where the outside air is better
than the inside air.
But in cold countries, fire is used inside the room to keep the inside air warm.
-
7/28/2019 Environment & Health
108/185
B. Artificial ventilation: (Mechanical ventilation)
These are of the four types.
i. Vacuum system
ii. Plenum system
iii. Balanced system and
iv. Air conditioning.
i. Vacuum system: (Exhaust system or extraction system).
In this system foul, vitiated air is extracted or exhausted to the outside by using
exhaust fans, operated electrically, so that vacuum is created and fresh air
enters in and fill its place.
They are usually provided in large halls, auditorium, cinema halls and are fixed near
the roof, because vitiated air is warmer and moves up.
Ventilation may be controlled by adjusting the speed of the fans. They are also
employed in the industries to remove dusts, fumes and other contaminants at
their source.
iv. Air conditioning:
-
7/28/2019 Environment & Health
109/185
In this system, the outer air is conditioned or controlled with reference to
physical and chemical conditions, such as cleaning (free from pathogens, dirt
and dust), adjustment of temperature (to cool it or warm it), adjustment of
humidity, which will be most comfortable and then letting into the room at a
measured rate and volume of flow without producing draught and exhaustedthrough ducts.
These are being increasingly used in operation theatres of the hospitals, in hotels,
restaurants, offices, commercial firms, cinemas, aero planes, railways, etc.
When the temperature difference between the outside air and air conditioned room is
very large, transition rooms are provided, so as to prevent sudden exposure
to high or low temperature.
The advantages of artificial methods of ventilation are the constancy and the facility
with which fresh air is supplied under all conditions,
whereas natural ones though less costly are not under human control being subject
to atmospheric conditions.
NOISE
-
7/28/2019 Environment & Health
110/185
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
-
7/28/2019 Environment & Health
111/185
Train, Aero plane engine about 120 dB
Threshold of pain about 140 dB
Jet plane about 150 dB
Mechanical damage 150 160 dB
Instruments used in the Study of Noise
i. Sound level meter measures the intensity of sound in
decibel (dB).
ii. Octave band frequency analyzer indicates whether the intensity is high
pitched or low pitched. - Hz
iii. Audiometer measures the hearing ability.
Zero line at the top of the audiogram represents normal hearing
-
7/28/2019 Environment & Health
112/185
Non auditory Effects
* Interference with speech communication.
* Annoyance (such as irritability, short temperedness, impatience, quarreling anddecreased production in the industries)
* Decreased efficiency in the work
* Lack of concentration
* Physiological changes such as
interference with sleep,
rise in blood pressure,
rise in intracranial pressure,
increase in heart-rate and breathing rate,
increase in sweating,
headache, giddiness, nausea, fatigue,
visual disturbances, etc.
PREVENTI