Rwss (rural water supply and sanitation)

This is the pdf notes about the rural water supply and sanitation. This pdf sis related to the cicil engineering. This pdf is for quick revision of this topic.

1. Village community in India and source of water

Introduction
Rural water supply and sanitation is a promise to provide a good quality of water to the villages. Over 80% of the
India live in the villages. There are about 6 lakhs villages. It is well known that India is the country of villages and an
identity of India from its village community.

About India and its village community
India is the second largest nation in the world with the population of 1.21 billion but it does not have an enough
resource in place to monitor its water quality. India facing a sharp contrast between its increasing population and
available service and resource.
Water supply is one such service where India has an enormous gap to fill. The current water supply service is
inefficient.

Importance of village community in India
There are some following major importance of village community:-
1. Preserver of ancient culture of the community – from the sociological point
of view, the villages are important because they preserve the ancient culture of the society. India is an
agricultural country. The life of the villages depend upon the natural process due to their occupation. The
villages in India still faith in the doctrine of karma, a fundamental principle in Indian culture.
2. Backbone of natural economy – Indian economy also based upon the natural sector.
Today economic seen is different in villages due to education, migration and change in cropping pattern,
irrigation, and contact with towns and cities. Indian government has accept the importance of the
development of rural industries and rural construction.
3. Ideal democracy – in ancient time, the Indian villages was an ideal democracy. Life in each
villages is self-dependent. The framers are quite capable of handling the work generally done by carpenter,
blacksmith, wood cutter and sometimes even a weaver.
4. Unit of society – India has always been a country of villages. 76% of the Indian population lives
in villages. Thus, in every respect, the future of India depend upon villages. Thus, the importance attributed
to the villages is far greater than the importance which may attributed to the towns of India.
5. Simple and economical life – the life of the villages is simple and economical. They have
very limited needs. The spirit of ambition and competition is generally absent.

2. Condition of Indian villages in various aspects
Economic
Indian villages still contribute about 51% of the national income. Most of it is secured from agriculture. Apart from
it, the government revenue i.e. rent in the form of land revenue, irrigation taxes, stamp fee and registration fee
etc. is earned from the villages.
India ranked second worldwide in farm output. Indian states Uttar Pradesh, Punjab, Haryana, Madhya Pradesh,
Bihar, West Bengal, Gujarat and Maharashtra are key agricultural contributing states of India.
Textile and handicraft manufacturing is the second largest source of employment after agriculture. Rajasthan is in
the third rank on milk production followed by Uttar Pradesh and Andhra Pradesh. This is also play a major role in
economic field in India.
Social
This country has already divided into two types of societies: - rural and urban society. Rural society presents a clear
picture of what India is but it should be kept in mind that rural society and its traditions are not uniform throughout
the country.
Rural society of the country is differ from place to place, according to the geographical condition and tradition of
the states. There are villages where most of the people take to cattle breeding or poultry farming. On the other
hand, there are certain states, where in villages people mostly take to agriculture with the growth of science and
technology.
In India, approximately 6000 dowry murders are committed every year. Since those giving as well as those accepting
dowry are punishable under the existing low, no one is willing to complain. It is only after a dowry death that’s the
complaints become public.
Health
Some facts about rural health
 42% of Indian children below the age of 3 are malnutrition.
 As more than 122 million households have no toilets.
 Only 26% of the slum population has to access to safe drinking water.

Traditional source of water in rural areas
There are mainly three source of the water which are following:-
1. Rain water
 The purest form of water.
 It becomes impure when comes in contact of dust, gases etc.
 Rain water is collected and stored carefully for drinking purpose. Rain water collected on the earth in
the form of surface water and underground water.
 The average rainfall received by different regions in the country in under 20 to 800cm.

3. 2. Surface water
This is vast source for rural areas, it is further classified as:-
a. Pond
 It is safe and comparatively less safe than lake.
 It is the main source of water in rural areas but not safe for drinking and cooking.
 Main source of pond water pollution are washing, bathing.
 A pond is a body of standing water, either natural or artificial, that is usually smaller than a lake.
b. Rivers
 It is the important source of water supply.
 Water from river stream is generally more variable in quality.
 Source of pollution of river water are wastage and drainage from agricultural land and habit of people
such as bathing, washing along the river bank.

c. Stream
 This is formed by runoff system. This channel feed their water to the lakes or river.
 These are useful as a source of water only for small villages.

d. Lakes
 A lake is the area of variable size filled with water that is surrounded by the land. Lakes lies on land
and are not a part of ocean, and are also larger and deeper than ponds.
 Many lakes are artificial and are constructed for industrial and agricultural use, for hydroelectric
power generation or domestic water supply.
 The majority of lakes on earth are fresh water and most lie in the northern hemisphere at higher
latitudes.

3. Ground water
Some of the rain water seeps through the soil on to the non-porous rocks below. This is the underground water.
This is the most safe source for domestic use of rural areas, it can be lifted up by well.
Well: - a well is the small hole dug in the earth surface from which subsoil water is taken out for irrigation and
drinking purpose. Water from well are lifted by four method – lever method, inclined plane method, Persian
wheel method, and power driven pump.
a. Open well – open well are generally open masonry wells having comparatively bigger diameter,
and suitable for low discharge of the order of 18 cubic metre per hour. The diameter of the open well
generally vary from 2 to 9 m and they are generally less than 20m in depth. The wall of the open well
may be built of precast concrete or brick or stone masonry. The thickness generally varies from 0.5 to
0.75 m, according to the depth of well. This arrangement will not give a structural support to the open
well but will also considerably increase its yield.

4. The open well may be classified into following types:-
i. Shallow well - a shallow well is that well which goes below the water table without meeting
mota formation.
ii. Deep well – a deep well is that well which goes below the water table and finally finds its
foundation in the mota formation. It is clear that mota formation is impervious. To derive water
from the soil a bore has to be drilled in mota formation. The water which enter the well through
the bore brings fine sand along with it in initial stage because of high velocity and pressure of
incoming water. Sometimes more than one bore holes are drilled to derive more water from the
underlying pervious rock.

Diagram from book
b. Tube well – a tube well is a water well consisting of a long tube bored into the ground and sunk to
the depth of water table. A small reservoir of water is made at the outlet of the tube well. This reservoir
is used for different usage of water by the local population. In the past, the pump was typically driven
by a large diesel engine. Today electric motor are more commonly used on account of economy.
Types of tube well
i. Cavity type tube well – this drawn water from the bottom of well and not from the sides. The
flow in the cavity well is spherical. In cavity type tube well, cavity is formed at the bottom and the
water from the aquifer enter the well pipe through the cavity.
ii. Screen type tube well – this is particularly used for irrigation purpose in our country. The flow
in the tube well is radial. This drawn water from the sides of the well.
This is further divided into the following two types –
 Strainer tube well
 Gravel pack slotted pipes tube well


Diagram from book

Water harvesting system
 It has been practised in many places without knowing the terms, but in accordance to their need. Such as
water supply in Mumbai from several decades based on this concept.
 Water harvesting is the highly economical and sustainable method of making water available for domestic
and community purpose.
 Water harvesting is the accumulating and storing of rainwater for reuse before it reaches the aquifer.

5. Need of water harvesting system
 To reduce soil erosion
 The gathered rain water can be used for agricultural purpose.
 The ever increasing the demand of water can be satisfied.
 The quantity of subterranean water can be increased.
 To conserve surface water runoff during monsoon.

Quantity of rainwater harvesting
1. Urban scenario – the total amount of water that is received in the form of rainfall over an area is
called rainwater endowment of the area. Out of this, the amount that can be harvested is called water
harvesting potential.
Water harvesting potential = rainfall * collection efficiency
The collection efficiency is account for the fact that all the rainwater falling over an area cannot be harvested
because of evaporation, spillage etc.

2. Rural scenario – they harvested water in the number of ways:-
 They harvested the rain drop directly. From rooftop, they collected water and stored it in the tank
built in their courtyards.
 They harvested monsoon runoff by capturing water from swollen streams during the monsoon
season and stored it various form of water bodies.
 They harvested water from the flooded river.

Different ways of harvesting rainwater
1. Surface runoff harvesting – in urban areas, rain water flows as surface runoff. This runoff could
be caught and used for recharging aquifers by adopting appropriate method.
2. Roof top rainwater harvesting – roof top harvesting is a simple technique that store larger
amount of water during rainy seasons that can be used during dry seasons. In this, rainwater is collected
from the roof of the building. It can be stored in a tank. The raised tank just below the roof level have high
head of pressure and the level of water in more in the tank. This method is less expensive and very effective.

Components of rooftop rainwater harvesting
1. Catchment – the surface that receive rainfall directly is the catchment of rainwater harvesting system.
It may be terrace, courtyard, or paved or unpaved open ground. The terrace may be flat roof or sloping
roof.

6. 2. Transportation – rainwater from the rooftop should be carried down by water pipes or drains to the
storage system. Water pipes should be UV resistant of required capacity. At terrace, the mouth of each
drain should have wire mesh to avoid the floating material.
3. First flush – first flush is a device used to flush off the water received in first shower. It will help in
removing silt and other material deposited on roof during dry seasons.
4. Filter – filter are used for treatment of water to effectively remove turbidity, colour, and
microorganisms. After first flush of rain water, water should be pass through filters. There are different
types of filter to purify water are as follows:-
 Sand gravel filter
 Charcoal filter
 PVC pipe filter
 Sponge filter

7. Quality of water and communicable disease

Disease
Communicable disease
A disease is said to be a communicable if it transfer from one person to the other person. It is also known
as infectious disease. Communicable disease is spread through air, water, food and contact.
Communicable disease such as a cold that can be transmitted from one person to the other person.
In other word, communicable disease is refer as a disease that can be transmitted and make the person
ill. In serve cases, they may lead to death.

Chain of infection
Infective agent – source of infection – mode of transmission – host
Infective agent – an infective agent is a microorganism such as bacteria, virus, fungi and parasite that
will cause an infection.
Source of infection- this refer to the environment in which infective agent live. The source of infection
will normally form the basis for the infective agent to infect human.
Mode of transmission - this refer to a method by which infective agent is moved from one place to
the other place. Some communicable disease have more than one mode of transmission.
Mode of transmission Sub types of transmission
Direct Touching
Sexual intercourse
Direct projection of droplet
Indirect Air borne
Vehicle borne
Vector borne

Host – some people are more prone to infection and become host.

Source of communicable disease
1. Water – drinking water must be taken from the safe source. The water which you taken from the
taps is safe to the drink. This is because the taps water is cleaned by the certain methods that kills

8. the germs before it is sent to our house. But water from the wells, ponds, and even hand pumps
is generally unsafe and may contains disease causing germs.
2. Milk – in this, disease is transferred from cattle to the human. Milk also serve as a growth medium
for some agent of bacterial disease.
3. Food- any food can act as a vehicle for infection especially if it raw or inadequately cooked or
improperly refrigerated after cooking.
4. Air – it is a vehicle for common cold, influenza, whooping cough, and chicken pox. Discharge from
the mouth, nose, throat and lung that takes the form of droplets which remain suspended in air.
5. Soil- it can be vehicle for tetanus, hookworm and some wound infection.
6. Insects – many disease are spread from the insects. Flies carry germs from rubbish and garbage
on their bodies and infect the food on which they are sit. They cause disease.

Mode of transmission of some communicable disease
Mode of transmission process Example of communicable
disease
Contact transmission Through direct body contact
with the infected person
Chicken pox
Droplet transmission Contact of droplet from the
infected person through the
sneezing, coughing and
speaking.
Pneumonia
SARS
Air borne transmission The infective agent float into
the air for sometimes and
enter into the body through
the respiratory tract.
Chicken pox
Food borne / water borne
transmission
Through injection of
contaminated food or
water
Food poisoning
Hepatitis A
Hepatitis E
Norovirus infection
Vector borne transmission Through vector usually
insect.
Dengue fever
malaria
Blood / body fluid
transmission
Through blood transfusion Hepatitis B
AIDS


Communicable disease control
1. Communicable disease can be avoided by washing hand regularly, washing fruits or vegetable
before eating, drinking treated water etc.
2. The person belonging to the disease whose clothes, utensils is kept separately.
3. Keep the water at home in the clean covered container. Boil the water for 10 min. to ensure it
become free of germs. Boil milk before using it.

9. 4. All the food, vegetable, fruits, milk etc. is kept covered.
5. Wash all the utensils before using them for storing food, milk or water.
6. All the children should be given the proper vaccination before birth in order to protect them from
many disease.
7. Keep your house and surrounding clean. See that all the doors and windows have wire mesh to
prevent the entry of flies and mosquitoes.


Immunity
We know that when a person is exposed to the germs, it get disease. Some people do not become ill even
when exposed to germs. Your body defence system consists of white blood cells which acts as a soldiers
to fight germs. In the fight of antibodies and germs, if the antibodies are able to resist and destroys the
germs then the disease get prevented.
Immunity is the ability of the body to resist the particular disease.

Types of immunity

Natural immunity – natural immunity is present at birth and is only toward the particular disease.
1. Naturally acquired immunity – when you suffered from the disease, the germs are present
in the body. So the antibodies are developed which remain the blood cell after the disease has
been recovered and help you fight against the future attack of that disease. Thus you have
acquired immunity naturally. The acquired immunity may be for short period or long life.
2. Artificial acquired immunity – when the weakened germs are introduced in your body
through the vaccination, the antibodies are developed in the blood cell to prevent the attack
of particular type of disease.

10. Guinea worm disease (drancunculiasis)
Guinea worm disease is an infection by the guinea worm. A person become infected when they drink
water that contain water fleas infected by the guinea worm larvae. Initially there are no symptoms. After
one year, the person develops a painful burning feeling as the female worm form a blister in the skin
usually on the lower limb. The worm then comes out of skin over a course of few weeks. During this time,
it may difficult to walk. It is very uncommon for a disease to cause death.
Human and dogs are only the two animal that guinea worm infect.

Symptoms of the disease
People usually do not have symptoms until about one year after they get infected. A few days to hours
before the worm comes out of skin, the person may develop a fever, swelling and pain in the area. More
than 90% of the worms comes out of leg or foot, but worm can also be appear on the other parts of body.
People in rural communities who have guinea worm disease do not have access to health care. When the
adult female worm comes out of skin, it can be very painful, slow and disabling. Sometimes, permanent
damage occurs if the person’s joint are infected and become locked.

Causes of disease
Guinea worm disease is caused by the drinking water contaminated with water fleas. Larvae develop for
approximately 2 weeks inside the copepods. At this stages, the larvae can cause guinea worm disease if
the infected copepods are not filtered from the drinking water. Once inside the body, the stomach acid
digest the water fleas, but not the guinea worm larvae. These larvae find their way to the body cavity
where female mates with the male guinea worm. This take place approximately 3 months after infection.
The male worm dies after mating and is absorbed.
Approximately one year after. The worm create a blister in the human skin usually on the legs. This blister
cause a very painful burning sensation as the worm emerges. Once the blister is submerged in water, the
adults female release hundreds of thousands of guinea worm larvae, contaminating the water supply.
During the next few days, the female worm is capable of releasing more larvae whenever it comes in
contact with water. Infection do not create immunity, so people can repeatedly experience guinea worm
disease throughout their lives.

Prevention
Guinea worm disease can be prevented by avoiding unsafe drinking water. Teaching people to follows the
simple control can completely prevent the spread of the disease:-
 Drink water only from the protected source that are free from contamination.

11.  Prevents people with swellings and wounds from entering ponds and other water used for
drinking.
 Always filter drinking water from unsafe source using a cloth filter or pipe filter to remove tiny
water fleas that carry the guinea worm larvae.
 Treat unsafe drinking water source with an approved larvicide. This will kills the tiny water fleas.
 Developing new source of drinking water that lacks the parasites.

Treatment
There is no drug to treat guinea worm disease and no vaccine to prevent infection. Once part of the worm
begins to come out of the wound, the rest of the worm pulled out a few centimetre each day. Sometimes
the whole worm can be pulled out within a few days, but this process usually takes weeks. Once the guinea
worm begin emerging, the first step is to do a controlled submersion of the affected area into the bucket
of water. This causes the worm to discharge many of its larvae, making it less infection. The water is then
discarded on the ground far away from the water source. It is of great importance not to break the worm
when pulling it out. Medicine such as aspirin can help to reduce pain and swelling. The worm can also be
surgically removed by a trained doctor in a medical facility before a blister forms.

12. Water treatment and scheme of rural water supply


Difference between slow sand filter and horizontal roughing
filter
Item Slow sand filter Roughing sand filter
Filter sand Sand range between 0.2 to 0.4 mm Sand range between 0.4 to 0.6 mm
Size of filter Large size Small size
Rate of filtration 100 to 150 litre/hr./sqm 6000-7000litre/hr./sqm
Economy Uneconomical Economical
Efficiency More efficient Less efficient
Depreciation cost Low More
Flexibility Not flexible Flexible
Skilled supervision Not required Required
Post treatment Not required Required
Ease in construction Simple Complicated
Filtration type Physical process Biological process



Horizontal roughing filter
Roughing filtration is an important pre-treatment of water so that fine particle can be removed from water and
decrease the load on treatment plant. This technique is mostly used for saline water by removing excess salt
content.
Components
1. Filter channel – this filter is constructed with three uniform components. Filter media are gravel,
coarse sand with decreasing size from 25 to 4 mm. the length of the filter depend upon the area and amount
of water to be treated.
2. Sump – it is the storage facility in which filtered water is collected from the tank.

Types of roughing filters
1. Vertical flow roughing filter – this types of filter work in two direction: down flow or up flow.
Water is supplied from top or bottom of the filter. It has a simple and self-cleaning mechanism. Top layer
is covered by coarse stone to prevent the entry of algal growth.
Diagram from book

13. 2. Horizontal flow roughing filter – this main advantages of this filter is unlimited filter length.
It has large storage capacity. The solid particle is settle at the top of the filter media. This type of filter is
less sensitive to flow rate change.
Diagram from book

Advantages of HRF
 It does not require any chemical.
 The cheapest technology.
 90-99% reduction in solid content.
 Suitable for rural areas.
 Remove solid matter from water more efficiently.

Disadvantages of HRF
 Colour removal is not efficiently done.
 Need large area for treatment.
 It can only handle low strength water.
 It has low hydraulic load.

Disinfection of rural water source
Disinfection is a process of destroying or inactivating disease causing organisms in water supplies. Although it is not
as thorough as sterilization, which completely destroys all living organism. Disinfection makes the water safe for
drinking and cooking
The world Health Organisation estimate that 1.2 billion people are affected by polluted water worldwide. About
400 children below the age of 5 die per hour in the developing world from water borne diarrheal disease. It is
estimated that 80% of all sickness and disease in developing countries are caused by the unsafe water. The single
most important requirement of drinking water is that it should be free from any microorganism that could transmit
disease to the consumer.
Necessity of disinfection
 Disinfection ensure safe distribution of water till it reaches to the consumer.
 Disinfection destroys all the pathogenic bacteria which may causes water borne disease.
 Disinfection secure the life of citizen.

Method of disinfection of rural water resources

14. 1. By boiling – boiling is the very simple method of water disinfection. Water should be boiled at 100
o
C
for 3-4 min before used in order for boiling most effective, the water must boil for at least 20 minute. This
method cannot be used on large scale but only in household. Water should be cooled before use.


All the other method see in the book


Fluoride and fluoride removal
Fluoride is a natural trace element which can be easily found in soil and water. It is one of the most powerful
oxidizing agent. Fluoride compound is about 0.08% of earth crust.
Fluoride salt are used for manufacturing various product like cryolite – a pesticide, 5- fluorouracil – an anticancer
drug and for preventing tooth decay if it is 1 mg/L. fluoride allow teeth damaged by acid to repair or remineralize
them. Fluoride cannot repair cavities, but prevent new cavities from forming.

Heath problem from excess fluoride
 Dental


Fluoride removal and control
Fluoride can be controlled by
 Transporting water from distant place.
 Mixing or diluting water till it is in allowable limit.
 Rain water harvesting

DE fluoridation
DE fluoridation refers to method of water treatment that reduce the concentration of fluoride in the water,
normally, in order to make it safe for human consumption. Defluoridation is used to characterise method that
reduce the fluoride ion specifically, without major other changes to the quality of the treated water.
1. Chemical method – various chemical are added to remove fluoride like magnesium, aluminium
salt. Use of alum in small amount in defluoridation was done in the Nalgenda district of Andhra Pradesh in
India using the process of coagulation. Nalgonda techniques was adopted by many countries like China and
Tanzania.

Nalgonda technique
The nalgonda process was adopted and developed in India by the National Environment Engg. Research
institute. Defluoridation of water by the Nalgonda technique is a commonly used household process.

15. Aluminium salts may be added as aluminium sulphate or aluminium chloride or the combination of these
two. It is responsible for the removal of fluoride from water. We found that the removal of fluoride from the
potable water is not adequate when the initial concentration of fluoride in the water is very high and the pH
of the untreated water is alkaline. The dose of the aluminium salt increase with the increase in the fluoride
and alkalinity level of the raw water. Bleaching powder is added to the raw water at the rate of 3mg/l for
disinfection.
Silent feature of nalgonda techniques
 No regeneration of media.
 Adaptable to domestic use.
 Applicable in batch and continuous operation.
 Local skill could be readily employed.
 Highly efficient in removal of fluoride from 1.5 to 20 mg/l to desirable levels.
 Removal of colour, odour, turbidity, bacteria, and organic contaminants.
 Little wastage of water and least disposal problem.
 Needs minimum of mechanical and electrical equipment.
 No energy except muscle power for domestic equipment.
 Economical.

Diagram from mobile

2. Precipitation techniques – it is cheap and extensively used in India. Method involved the
addition of alkali, chlorine and aluminium sulphate or aluminium chloride or both was developed. Fluoride
removal is accomplished with the separation of solids from liquid. Limestone can remove the fluoride from
water through the combination of adsorption and precipitation processes and magnesium oxide also act as
precipitating agent.

3. Contact precipitation – it is the technique by which fluoride is removed from the water through
the addition of calcium and phosphate compounds and then bringing the water in contact with an already
saturated bone charcoal medium. Bone charcoal is used as supporting medium and as a catalyst for the
precipitation of fluoride. It has been found that water containing 10mg/l fluoride can be treated with 95%
efficiency.

Diagram from mobile
4. Ion exchange method – synthetic chemical, namely, anion and cation exchange resins have been
used for fluoride removal. These resin have been used in chloride and hydroxyl form. The fluoride exchange
capacity of resin depend upon the ratio of fluoride to total anions in water. The capacity increased with
increasing ratio. The proportional quantity of fluoride as compared to other anions is very small, the
effective capacity of such resins work out quite low. The cost of anion resin is Rs. 20 to 35 per litre. The
results indicate that anion exchange resins are not economical for removing fluoride from water. Some of
these are polyanion (NCL), deacdite FF (IP).

16. 5. Tamarind gel – the concentration of fluoride from of solution of sodium fluoride of 10mg/l could be
brought down to 2 mg/l by the addition of tamarind gel alone and to 0.05 mg/l by the addition of small
quantity of chloride with the tamarind gel.

6. Nano filtration – Nano filtration is the process which takes in the upper end

7. of reverse osmosis, and lower end of ultra-filtration. Permeability of Nano filtration membrane is higher
than those of RO. It require less pressure and capital than Ro. It is widely applicable especially for drinking
and waste water treatment.

Rural water supply programs
The provision of safe drinking water supply sanitation facilities is a basic necessity of life. Provision of safe drinking
water and sanitation is the primary responsibilities of the states. Thus, various policies have been given by Indian
government.

1. Rajiv Gandhi National Drinking Water Mission (RGNDWM) – the
Accelerated Rural Water Supply Programme (ARWSP) currently implemented through the Rajiv Gandhi
National Drinking Water Mission. It was launched by the Govt. of India to resolve the drinking water
problem, and accelerated the working speed of states and union. The key objectives are:-
 To ensure permanent drinking water security in rural India.
 To improve the performance, cost effectiveness of the on-going programme
 To ensure that all school and anganwadis have access to safe drinking water.

2. National Water policy, 1987 – since water is the basic need of human beings. As the
industrialization, there is ever increasing demand for agriculture, hydropower, navigation etc. and
simultaneously our population has reached 1000 million by the century. The objective of the policies:-
 To transfer water to water storage area.
 To recycle and reuse water.
 To study the environmental impacts.
 To develop ground water.
 To estimate the time and cost of project.
 To plan, develop and manage river basin.
 Adequate drinking water facility.
 Planning of irrigation.
 Flood control and management.
 Promoting awareness about water conservation.
 Drought management.

17. 3. National Water Policy, April 2002 – the some basic principle and objectives are:-
 Encourage the participation of private sector.
 Resettlement and rehabilitation of population.
 Maintenance and modernization.
 Improvement of facilities.

Treatment of water
Water treatment is that which make the water more acceptable for an end use which may be drinking, industry or
medicine.

1. Coagulation – during coagulation, alum is added to untreated water. When it mixed with water,
this cause the tiny particle of dirt in the water to stick together to form larger heavier particle called flocs
which are easier to remove by settling or filtration.
2. Sedimentation – as the water and floc particle is move through the sedimentation basins where
the water moves slowly, causing the heavy floc particle to settle to the bottom. Floc which collected on the
bottom of basin is called sludge.
3. Filtration – water flows through a filter designed to remove the particle in the water. The filter are
made of layer of sand and gravel. Filtration collects the suspended impurities in the water and enhance the
effectiveness of disinfection. The filter are cleaned by back washing.
4. Disinfection – water is disinfected before it enter into the distribution system to ensure that any
disease causing bacteria, viruses and parasites are destroyed. Chlorine is used because it is a very effective
disinfectant.
5. Fluoridation – water fluoridation is the treatment of community water supplies for the purpose of
adjusting the concentration of the free fluoride ion to the optimum level.
6. pH correction – lime is added to the filtered water to adjust the pH and stabilize the naturally soft
water in order to minimize corrosion in the distribution system.

18. Food sanitation and mosquitoes control

Pasteurization of milk
The Pasteurization of milk is a process invented by the French scientist Louis Pasteur during the 19
th

century. He discovered that the heating of beer and wine is enough to kill the most of the bacteria. The
Pasteurization of milk is used to destroy the disease causing of bacteria in the milk. Unlike the sterilization, the
Pasteurization is not use to kill the all the pathogens but it use to control the growth of bacteria that cause the
disease. The commercial scale sterilization of food is not used because it affect the taste and quality of food. In the
olden days, the urban densities is increasing and the transportation of milk from the country to city make the milk
is unsafe for drinking and as a source of disease. The developed countries used the Pasteurization of milk to make
the milk safe for drinking and to prevent disease and loss of life. And as result now the milk is widely considered as
a safe food.
The entrance of dust and manure and at the high temperature affect the growth of bacteria and large number of
bacteria causing quick souring and bad tasting of milk. Essential of dairy farm and cattle shed has two object:-
1. the production of safe milk
2. the production of clean milk
The essential to attain these two object are:-
1. Healthy cow – all the cows from which the milk is obtained and transported to the cities is need
to be tested in every six years.
2. Clean and healthy workmen – the workmen should be practically examined. The workmen should
be healthy, clean and disinfect during the milking.
3. Dairy barn and surrounding – the barn should be clean to obtain the milk in it. The least dust is
comes into the barn from the surrounding during the milking. The surrounding should remain
clean and free from the bacteria.
4. The milk house – the milk house should not be used for the other purpose rather than the handling
and processing of milk.
5. Pasteurization of milk – the Pasteurization of milk is done by heating the milk at the temperature of 100oC
to destroy most of the micro-organism present in the milk.. The milk can be remain safe for the 2 or 3 days
after milking

Life cycle of mosquitoes
The mosquitoes goes through a 4 distinct stages of its life cycle: Egg, Larva, Pupa and Adult. Each of these stages
can recognised by its special appearance.

Diagram

19. Egg: - egg are laid one at a time or attached together to form raft. They float on the surface of water. Most eggs
hatch into larvae within 48 hours. Water is necessary part of their habitat.
Larva: - the larva lives in the water and comes to the surface to breathe. The larva molt their skins 4 times,
growing larger after each molt. The larva feed on microorganism and organic matter in the water. During 4
th
molt
the larva changed into the Pupa.
Pupa: - the pupal stage is the non-feeding stage of development. This is the time after that mosquitoes changed
into the adult. When development is complete, the pupal skin splits and the adult mosquito emerges.
Adult: - the newly emerges adult rests on the surface of the water for some time to allow itself to dry and all
its body part to harden. The wings has to be spread out and dry it properly before it can fly.

Mosquito control
In order to prevent the malaria and other disease caused by mosquitoes, the following method must be adopted:-
1. elimination of breeding place
2. Destruction of larvae and pupa – larvae and pupa may be killed by covering or spraying the
surface of water with petroleum, crude oil or kerosene oil.
3. Destruction of adult mosquito – mosquito should be driven out of houses or killed by spraying
with DDT or other insecticides.
4. Defence against mosquitos – houses are affected by mosquitoes and those should be kept
mosquitoes free. Door and windows should be screened with mosquito jalis.

20. Sanitation and awareness

Bio gas
Biogas typically a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen.
Biogas can be produced from the raw material such as agricultural waste, municipal waste, plant material, manure,
green waste or food waste. It is a renewable energy source. Biogas is primarily methane and carbon dioxide and
contain a small amount of hydrogen sulphide, moisture and siloxanes. Biogas can be used for heating purpose such
as cooking. Biogas can be compressed in the way the natural gas is compressed to CNG which is used for the motor
vehicles. Biogas can be cleaned and upgrade to natural gas standards.

Working of biogas plant
Organic input material such as foodstuff, fat or sludge can be fed into the biogas plant as a substrate. The renewable
resource such as corn, or grass serve as a feed for the animal such as cows and pigs as well as for the microorganism
in the plant. The manure and dung are also fed into the biogas plant. The substrate has been decomposed by the
micro-organism under the exclusion of light and animal. The final product of the fermentation is biogas with
methane as the main ingredient. The hydrogen sulphide is also contained in the biogas.
Once the substrate has been fermented, it is transported into the fermentation residue end storage tank and can
be retrieved from there for further utilization. The residue can be utilized as a high quality fertilizer.
The temperature of the product is quite important because the methane producing bacteria do their best work at
the temperature between 30-40oC and 50-60oC. It takes from 2 to 8 weeks to digest the load of waste depending
upon the temperature. The biogas generated is collected at the top of the tank and from there it is taken by the
pipe to the user.

Diagram from the book

Use of biogas
The biogas burnt very clearly with the flame as compared to LPG. The biogas can be used for the variety of other
purpose such as lighting, refrigeration, engine operation or generation of electricity.

Advantages of the biogas
1. Biogas burnt very clearly and produce less pollutant during cooking than any other fuel except electricity.
2. The by-product of the biogas plant can be used for the fertilizer.
3. Saving in the cost of disposal and treatment of waste and wastewater.
4. Every domestic biogas plant can save about 4 tonnes of fuel wood per year.
5. It can be used for the lighting.

21. 6. Conservation of trees and reduction in the soil erosion.

Disadvantages of biogas
1. It require a continuous supply of water, which is problem in the arid area.
2. The continuous supply of dung is require.
3. It will increase the workload that is feeding the raw material into the plant.