Water supply slides (1).pptx

UNIT 1:IMPORTANCE AND NECESSITY OF
PLANNED WATER SUPPLY
Importance:
•Basic needs are air, water, heat, light, food, shelter and clothes.
•Plants have basic needs others than shelter and clothes.
•After air, plants and animals need water and they can’t survive without it.
•Human can survive without food, shelter and clothes for several days but
can’t without water.
Water is needed for following purposes:
•cooking and drinking
•bathing and washing
•watering lawns and gardens
•growing crops
•street washing
•fire fighting
•swimming pools,fountains
•power generation and various industrial purposes

Necessity of Planned Water Supply
• Ancient civilization developed along the riverbanks due to the
availability of water for domestic and irrigation purpose.
• Every family was responsible to arrange water.
• Later people started to live at distant places from river ,spring, wells
etc and water became insufficient.
• Community size also increased. Hence to sustain large community,
planned large scale supply system became essential.
• For large scale supply communities started to collect water from
distant large source.
• As passage of time sources near some communities started to
pollute. Hence need of planned and treated water also felt.
• Systematic and well-arranged water supply schemes to supply
adequate quantity of safe water to consumers for drinking and
other purposes was felt.

History of Planned Waer Supply System in
Nepal
• Dhungedhara and inar were constructed with with the
construction of pati, pauwa, math, mndir, durbar etc
from Lichhavi period. They were developed in Malla
period.
• Provision of protected water supply was started after
those periods.
• Now in Nepal more than 75 % of people in rural area
are getting drinking water schemes.
• UNICEF ( United Nation’s Children’s Emergency Fund),
WB (World Bank) , ADB ( Asian Development Bank) ,
JICA( Japan International Co-operation Agency) etc are
working in the field of water supply.

Impact of Water Supply( Long Term and Short
Term Impact)
Short Term Impact
• Fetching time ( long go and bring) is saved so that this time can be
used for other productive works
• Improves hygienic condition so that time and money expenses for
medicine are saved. Women health and public health improves.
• Safe (reliable) adequate and effective supply is gained.
• Street washing and household sanitation improves environment.
Long Term Impact
• Increases socio-economic activities of individuals, family and then
community.
• Increases the living standard of the people.
• Helps in the economic growth of whole nation

Components of Water Supply System
• Components of Rural Water Supply System
• Transmission line: Pipeline from intake to reservoir tank.
• Distribution Line: The pipeline from reservoir tank to tapsands.

Components of Urban Water Supply System
• Collection Works: May include intake works and storage. If river is not
consisting a large discharge and is not a perennial type then storage is
needed but if the size of river is large and perennial, then direct intake
chamber can be made.
• Transmission Works: In many cases water supply schemes are far away
from the city and water should be conveyed to it through transmission
works. It is the connection between the collection and purification works
through conduits, pipes, canal aqueducts etc.
• Purification Works: It is required to treat water for required quality. The
process depends upon the quality at source and quality required.
• Distribution System: It is required to convey purified water from clear
water reservoir to the users by any system of distribution such as grid iron
pattern or dead end pattern.

UNIT 2: SOURCES OF WATER SUPPLY
Hydrological Cycle
• T is also known as water cycle. It explains the circulation of water of the
earth and its atmosphere.
• Water in the sea , damp places, lakes, river etc evaporate and convert into
cloud.
• Cloud or the water vapour is also formed by the evapo-transpiration of
vegetation.
• The moist air or cloud moves to higher altitude where it cools and form s
water which falls down to the earth surface . This process of rainfall is also
called precipitation.
• Precipitation or or water fell in high altitude convert into snow.
• Water after precipitation moves down to lower levels mixing in streams
,rivers, lakes etc.
• Due to rain, seepage of water inside earth also occur which comes out in
form of spring and mixes to rivers and streams.
• Water in rivers, streams, lakes again evaporate.
• Evapo-transpiration from vegetation again takes place.
• Again cloud is formed and precipitation takes place.
• The cycle of forming cloud, precipitation , increase in water flow and again
occurring evaporation and transpiration takes place and this cycle is
known as water cycle or hydrological cycle.

Surface Sources
Streams
• Discharge is maximum in rainy season and may dry up in summer
season. If streamdries up in summer season it is called ‘rainy
stream’ or non-perennial stream. Streams may be formed by snow
melting or by collection of spring sources in its path.
Rivers
• Rivers are formed by combination of the springs and streams from
hill to the low land and sea. So in hills they are small and larger in
the low land due to the increment of collection . Rivers may be
snow fed or non- snow fed. Rivers may also be of perennial or non-
perennial type.
Ponds
• Ponds may be formed as temporary or permanent. These are not in
the large quantity. If water collects in excavation made for road,
building etc. it is temporary. If water collects in other low land with
springs inside they are permanent.

Surface Sources
Lakes
• Natural basins with impervious bed in the mountainous region is a lake. It
is the permanent type surface source formed in high altitude in between
mountains eg. Phewa, Rara, Begnas,TschoRolpa lakes.
Sea
• Rivers move to the areas of low altitude where a very large mass of water
collects which is called sea. Sea of very large mass is called ocean.
Impoounded Reservoir
• These are the artificial reservoir constructed to store water to meet
demend at the dry seasons. The water is stored by constructing weir or
dam across the river. Larger collection is possible by dam but for smaller
collection we use weir.

Ground Sources
1. Springs
Gravity Spring
• When impermeable formation or strata intersects water bearing
strata at the surface of ground slope as shown in the above figure
then there is formation of spring called gravity spring. (Ground
water table is above impervious strata, water flows in gravity).

Artesian Spring
• This spring is formed on the ground surface if there is pressure of
the water bearing layer in the case that water gets way to come out
at the surface.

Wells
Shallow Well (Shallow Open Well)
• It is the open well which rests on the top water bearing
strata.
• It is cheap in construction and used in rural areasand small
towns.
• In this well , quantity of water is very smaller than in deep
wells because it yields water from the top water bearing
strata only.
• This well should be disinfected frequently to avoid the risk
of contamination.
Deep Well (Deep Open Well)
• It is the open well which rests on impervious strata and
draws the supplies from the pervious formation lying below
the impervious strata through bore holes made in the
impervious strata.

Wells
Artesian Well
It is the well from where water flows automatically under pressure. Mostly they are found
in the valley portion of the hills where aquifers on the both sides are inclined towards
valley. The hydraulic gradient line passes much above the mouth of well, which causes flow
under pressure. The water flows out in the form of fountain upto a height depending upon
hydrostatic pressure.

Tube Wells
Strainer Type Tube Well
• It is the most used tube well, which has internal diameter 25 to 90
cm.
• It consists of a combination of strainer pipes in all water bearing
strata and blind pipes in the hard strata only.
• The gravel is packed around the pipe which checks the entry of soil
particles .
• For construction of this tube well, first boring is done by lowering a
casing pipe of 5 to 10 cm larger than diameter of well pipe and the
record of strata during boring is noted and blind and perforated
pipes are joined as per the result then inserted into the casing.
• The gravel packing is done during removal of casing pipe.

Tube Wells
Cavity Type Tube Well
• It consists of blind pipe throughout its length and rests on hard
stratum hence it can draw water from the lower stratum only.
• At beginning, just after construction , fine sand, silt come out along
with the water and causes cavity at the bottom.
• When area of the cavity increases the flow area increases forming
spherical part and increases the yield.

Tube Wells
Slotted Type Tube Well
• If sufficient no. of water bearing strata is not available to make
strainer type tube well even upto 100 m, slotted type tube
wells are used if at least 1m water bearing strata is found
below ground.
• It consists slotted wrought iron pipe passing through water
bearing strata.
• The slotted portion of pipe is surrounded by gravel which is
called shrouding.
• Shrouding is filled between casing pipe and slotted pipe
during withdrawing of casing.
• Shrouding helps to restrict soil particles to enter to the tube
through slotting. (Pulling of casing pipe and filling gravel
simultaneously)

Tube Wells
Perforated Type Tube Well
• It is used if water table is shallow and for obtaining water for short
duration such as in construction sites. Pipes are drilled to make
perforations and these holes are covered by jute ropes which act as
strainer for preventing flow of sand particles.

Infiltration Galleries
• An infiltration gallery is a horizontal drain made from perforated
pipes which are laid below the water table and collects ground
water.
• The gallery should be surrounded with a gravel pack to improve
flow towards it and to filter any large particles that might block the
perforations.
• Water is taken to a collection well or sump and then either
withdrawn directly or pumped to a storage tank.
Procedure of Construction
• Excavate a trench to at least one metre below the water table ,
supporting the sides to prevent collapse.
• Lay graded gravel on the base of the trench.
• Lay the pipe on top of the gravel. Cover the top and sides with
graded gravel.
• Cap the gravel with an impermeable layer of clay to prevent surface
water entering the gallery.
• This method is most appropriate when galleries are laid alongside
rivers where the ground water is close to the surface.

Alternative Water Sources
a)Rain Water Harvesting
• It is the accumulation and deposition of rain water for reuse on-site
,rather than allowing it to run-off.
• Rainwater can be collected from rivers or roofs and in many places
the water collected in this way is re-directed to a deep pit or a
reservoir.
• Water harvested has uses including water for gardens , livestock,
irrigation, domestic use including drinking with proper treatment
and indoor heating for houses etc.
System Setup:
• It includes systems that can be installed with minimal skills to
advanced setup and installation.
• Large systems to meet the water demand throughout the dry
season to support daily water consumption are also constructed.
• The rainfall capturing area such as a building roof must be large
enough.
• The water storage tank size should also be large enough to contain
the captured water for larger collections throughout rainy period.

b) Conservation Pond (Conserve for Dry Season)
• During the pre-monsoon season between March and May , some
areas experience water shortage.
• On the other hand , during the monsoon, water excess causes
regular floods and landslides.
• In this situation activities such as agriculture as well as the
availability of drinking water and women’s workload are deeply
affected.
• Water requirement through year needs to be achieved.
• Because there is conservation of rain water directing to
conservation pond it protects hill sides from landslide during rainy
season.
• Water in rainy season can be conserved in rainy season and can be
used in dry period.

c) Fog Collection
• Two mesh fabric plates opened and closed slowly converting fog
into water droplets which is ultimately collected which drops down
to the collector from the plates.
• Large fog collectors to provide clean water for villages in some of
the world’s driest environments are used.
• Presently there are operational fog collection projects in the world
in many countries.
• Most fog collection is done using mesh fabrics.

Conservation and Protection of Sources
• Water sources should not be allowed to be polluted by sewerage
and other pollutants like chemicals of the industries,vegetations
etc. Hence water quality should be conserved.
• Quantity of flow should be constantly enough throughout the year.
It should not be captured in its upstream side.
• Sources should not be damaged by landslides etc.
• It should be fenced well to protect from animals and other external
bodies.
• Retaining structures should be constructed if needed.

Selection of Sources
The selection of sources of water depends upon the following factors.
a)Location
• It should be near to the consumer’s area or town as far as possible.
• If there is no river, stream or reservoir in the area ground source
proves to be economical.
• For hilly area source selected should be at sufficient height for
gravity flow.
b)Quantity of Water
• It should have sufficient quantity of water to meet the demand for
that design period in the wet and dry seasons also. Two or mor
sources can be joined for required quantity.
c)Quality of Water
• The water should be safe and free from pathogenic bacteria, germs
and pollution and so good that water can be cheaply treated.

d)Cost
• It should be able to supply water of good quality and quantity at the
less cost.
• The cost depends upon difference in ground level and distance
between source and the city to supply.
• Gravity system of flow is generally cheaper than pumping.
• Lesser the impurities, lesser is the treatment and cost is reduced.
• Cost analysis is necessary for various options and suitable one is
selected.

e)Non-conflict among Water Users ( Water Right Problem)
• The upstream of a river or stream may be claimed by the people of
higher elevation and if people of lower elevation take water from
downstream of that source the supply may become insufficient or
completely dry in case upstream users use the source to launch
their own project.
• Hence the possibility of use by the upstream users should be
studied formerly before formulating a project.
• This problem of lack of source supply is called water right problem

UNIT 3: QUANTITY OF WATER
Types of Water Demand
a) Domestic Demand
• It is the demand of water for home use including drinking, cooking,
bathing, washing and house sanitation.
• It depends upon the habit, social status, climatic condition etc.
• This demand is 135 and 200 lpcd for small and large towns respectively.
• WHO standard for domestic demand is minimum 45 lpcd.
Domestic demand (lpcd) for small towns
• Drinking : 5
• Cooking: 5
• Bathing: 55
• Clothes washing: 20
• Utensils washing: 10
• Home washing: 10
• Flushing latrines: 30
Total = 135 lpcd

b)Livestock Demand
• The quantity of water required for domestic animals is called
livestock demand.
• It is generally considered in rural water supply.
• In practice, upto 20% of domestic demand may be taken as
livestock demand.
c) Commercial and Institutional Demand
• It includes the demand for office building, stores, hotels, schools,
hospitals, theaters, clubs etc.
• For commercial and institutional purpose 45 lpcd can be taken.
d) Industrial Demand
• It is commonly considered in urban areas.
• This demand depends upon the type of the industry.
• Normally 20 to 25% of the total demand is taken for industrial
demand.

e) Public Demand
• It includes washing and sprinkling on road, cleaning sewers,
watering public parks,gardens etc.
• Generally 20 to 25% of the total demand is taken as this demand.
f) Firefighting Demand
• During outbreak of fire , water is used for firefighting called fire
demand.
• This demand is not fixed so it is difficult to calculate this demand.
• Fire hydrants of 15 to 25 cm diameter are provided on water mains
100 to 150 apart to extract through water for firefighting.
g) Losses and wastages
• It includes losses due to defective pipe joints, cracked and broken
pipes, faulty valves and fittings, unauthorized connection (theft)
,allowance for keeping taps open etc .
• Losses and wastages is about 50 % in Kathmaandu valley.

Factors Affecting Water Demand
a)Size and Type of Community
• Bigger size, higher the demand due to lots of public places of utility and
recreation such as parks, lawn, ponds, fountains etc.
b) Living Standard of People
• Higher is the living standard higher is the demand.
c) Climatic Condition
• Hotter the climate higher is the demand.
d) Quality of Water
• Good quality higher is the demand.
e) Pressure in the Supply
• Higher the pressure loss is more and higher is the demand.
f) Metering
• Use of water meter lesser is the demand.
g) System of Supply
• Demand is lesser in intermittent and higher for continuous supply.
h) Water Rates
• Higher the rate lesser is the demand.
i) Education and Awareness of people
• This changes behavior of people in health care which leads to use more water.

Socio-economic Factors Affecting Water
Demand
• Public Versus Private Tap stand: Public tap, lower is the demand
• Habits of People: Frequency and bathing habits of people also
affect the demand.
• Rich family will use more water for washing clothes and bathing.
• Distance to Tapstand: Nearer the tapstand demand is the higher.
• Urban versus Rural: Lower demand in rural area due to habit and
living standard etc.

Variation in Water Demand
Fluctuation of Water with respect to time is called variation of
demand.
Seasonal Variation:
• In summer the demand is higher because of more bathing,
lawn watering,street sprinkling etc. but lesser in winter
Daily Variation:
• Water demand is higher in Saturday than in other days.
Demand is more in the feasts and festivals.
Hourly Variation:
• Demand is more in morning and evening due to cooking,
bathing etc.

Average Demand
• Average demand may be seasonal average which can be obtained
by taking average from different seasons.
• It may be daily average which can be obtained by taking average
from days of a week.
• It may be hourly average which can be obtained taking average of
hours of a whole day.
• Average annual daily consumption is that demand which is
calculated for average consumption per day for whole population
considering whole year.
• AADC= P*q, where P is population and q is average per capita
demand ( whole year average).

Peak Demand and Peak Factor
Peak demand is maximum hourly demand at the
maximum day of maximum season so it is obtained
from:
Peak demand= PFH x PFD x PFS x Qav
Qav= average daily consumption
= Pxq where P= population
q= average lpcd.
Hence ,
Peak demand= 1.4 x 1.8 x 1.3 x Qav
=3.5 x Qav
= PF x Qav
where PF = peak factor = 3.5

Design Period
• Any water supply project is planned to meet the present
requirements of a community as well as the requirement for a
reasonable future period taken in design is called as design
period.
• If design period is long, construction becomes heavy and
there is financial overburden.
• If design period is short the project will leave to function in
short time and hence it will not be economical.
• In Nepal design period for rural areas is 15-20 years and for
urban areas it is 25-30 years.

Factors Affecting Design Period
(Selection Basis)
Design period should be fixed after considering the following:
• Fund available: More fund, higher is the design period.
• Life of the pipes and construction materials: Design period should
not be greater than the life of pipes and constructional materials.
• Rate of interest of loan: If more the rate of interest, lesser will be
the design period.
• Anticipated expansion rate of the town: If growth rate (r) is high,
design period is less.
If r≥2, design period is 15 years.
If r<2, design period is 20 years.

Population Forecasting
• Necessity: Population forecasting is needed to determine the
growth rate (r) of a city or village.
• After determining growth rate we can fix the design period
considering other factors also such as interest rate of loan, fund
available, age of pipes and constructional materials etc.
Methods of Population Forecasting
• Arithmetic Increase Method
• Geometrical Increase Method
• Incremental Increase Method

Population Forecasting
Arithmetic Increase Method : This method is based on the
assumption that average rate of increase in population per
time unit 'c' is constant.
i.e, P1 = P0 + C = P0 + 1C
P2 = P1 + C = P0 + 1C + C = P0 + 2C
P3 = P2 + C = P0 + 2C + C = P0 + 3C
Hence, Pn = P0 + nC
Where, P0 = no. of known population
n = no. of time unit, year or decade

Arithmetic Increase Method
Example
From the following data, forecast the population in the year 2070, 2080 and 2090 from the
Arithmetic increase method.
We have formula
Pn= P0 + nC
Here, P0 = last known popn = 47,000
C = average increase in population
= (28000-25000) + (34000-28000) + (42000-34000) + (47000-42000)
4
= 3000 + 6000 + 8000 + 5000
4
= 22000
4
= 5500

Arithmetic Increase Method
Then
Pop. for 2070 = Pn = P0 + nC
= 4700 + 1 * 5500
= 52500
Pop. for 2080 = Pn = P0 + nC
= 47000 + 2 * 5500
= 47000 + 11000
= 58000
Pop. for 2090 = Pn = P0 + nC
= 47000 + 3 * 5500
= 47000 + 16500
= 63500

Geometrical Increase Method
This method is based on assumption that % increase in the
population per time unit remains constant for each time
unit. It is also known as uniform growth method.
P1 = P0 + r% of P0 = P0 (1 + r/100)1
P2 = P1 + r% of P1 = P1 (1 + r/100) = P0(1 + r/100)( 1+ r/100)
=P0 (1+ r/100)2
P3 = P2 + r% of P2 = P2 (1+ r/100) = P0 ( 1 + r/100)2 (1 + r/100)
= P0 (1 + r/100)3
Generalizing;
Pn = P0 (1 + r/100)n

Example:
From the following data forecast the population in the year 2070, 2080 and 2090 from the geometrical
increase method.
Here, P0 = 47,000
r = average% increase in population
• Here, P0 = 47,000
• r = average% increase in population
•
r1 = (28000-25000) X 100 = 3000 X100 = 12 %
25000 25000
r2 = (34000- 28000) X 100 = 6000 X 100 = 21.4%
28000 28000
r3 = (42000 – 34000) X 100 = 8000 X100 = 23.5%
34000 34000
r4 = (47000 – 42000) X 100 = 5000 X 100 = 11.9%
42000 42000
r = r1 + r2 + r3 + r4 = 17.2 %
4

From the formula,
For 2070,
or, P1 = 47000 (1 + 17.2/100)1
Pn = P0(1 + r/100)n
Hence ; P1 = 55084 = population
For 2080,
Pn = P0(1 + r/100)n
or, P2 = 47000 (1 + 17.2/100)2
Hence; P2 = 64558 = population
For 2090,
Pn= P0(1 + r/100)n
or, P3 = 47000 (1 + 17.2/100)3
Hence; P3 = 75663 = population

Incremental Increase Method
P1 = P0 + ( c + i) = P0 + 1c + 1(1+1)i/2
P2 = P1 + ( c + 2i) = ( P0 + c +i ) + (c + 2i)
= P0+ 2c +3i
= P0 + 2c + 2(2+1)i/2
P3 = P2 + ( c + 3i) = P0 + 2c + 3i + (c +3i)
= P0 +3c + 6i
= P0 + 3c + 3(3+1)i/2
Generalizing,
Pn = P0 + n c + n (n+1)i/2
Where ,
P0 = last known population
c= average increase in population
i = average of incremental increase

Example
From the following data ,forecast the population in the year 2070, 2080 and 2090 for a VDC from the
incremental increase method.
c = average increase in population
= (28000 - 25000) + (34000 – 28000) + (42000-34000) + (47000- 42000)
4
= 3000 + 6000 + 8000 + 5000
4
= 22000/4
= 5500
i = average of incremental increase
= (6000 – 3000) + ( 8000 -6000) + ( 5000 – 8000)
3
= 3000 + 2000 – 3000
3
= 2000/3
= 666.67
= 667 (say)

For 2070;
Pn = P0 + nc + n ( n+1) i /2
P1 = 47000 + 1* 5500 + 1(1+1)*667/2
= 47000 + 5500 + 667
= 53167
For 2080;
Pn = P0 + nc + n ( n+1) i /2
= 47000 + 2*5500 + 2(2+1) * 667/2
= 47000 + 11000 + 3* 667
= 60001
For 2090:
Pn = P0 + nc + n ( n+1) i /2
= 47000 + 3* 5500 + 3(3+1)*667/2
= 47000 + 16500 + 6*667
= 67502

Calculate Present Population
Example
If the discharge of a spring source is 3.9 litres per second ,
calculate the no. of present population if it can serve for the
design period of 15 years. The population growth over 15
years is 35%.
Solution
Here,
Discharge Q = 3.9 l/s = 3.9 * 60 * 60 *24 l/day = 336960 l/day
Design period from present time (n) = 15 years
Overall population growth (r) = 35% for 15 years
Present population (P0) = ?
We have ( from geometrical increase method) ;
Pn= P0 (1 + r/100)n where r is in % for 15 years; hence,

Calculate Present Population
Then;
Population after 15 years P = P0 (1 + 35/100)1 where n =1
because r (35%) taken for 15 years.
= 1.35 P0.
Let, per capita demand (q) = 45 lpcd (for village)
For serving 15 years,
Q = q * p = 45 * 1.35 P0
or, 336960 = 45 * 1.35 P0
Hence, P0 = present population = 336960/(45*135)
= 5547 nos.

Calculate Total Water Demand
Example
Calculate the total water demand in the design year 2021
AD for a village . The data collected during survey is as
follows:
Survey year 2010 population = 2320
Population growth rate = 1.5% per year
No. of cows = 4030
No. of goats = 1530
No. of chickens = 5500
No. of students = 200 boarders and 1020day scholars
No.of VDC offices = 5

Solution
Survey year (2010) population (P0) = 2320
Design year = 2021
Total water demand in design year 2021 (Q) =?
Population growth rate (r) = 1.5 % per year.
Then,
No. of years for design year, n = 2021-2010 = 11 years
We have;
Pn = P0( 1 +r/100)n
P11 = 2320 ( 1 + 1.5/100)11
Hence , P11 = 2733 nos.

Calculation of demand is as under:
a) Domestic demand = P11 * rate = 2733 * 45 lpcd = 122985 l/d
b) Livestock demand :
For cows = 4030 nos. @ 45 lpad = 181350 l/d
For goats = 1520 nos. @ 20 lpad = 30400 l/d
For chickens = 5500 nos. @ ( 20 l/100) chickens per day = 1100 l/d
Total livestock demand = 212850 l/d
c) Institutional demand;
For day scholar students = 1020 nos.@ 10 lpcd = 10200 l/d
For boarders = 200 nos. @ 60 lpcd = 12000 l/d
For VDC offices = 5 nos @ 350 l/ office/day = 1750 l/d
Total institutional demand = 23950 l/d
Total water demand = Total of all demands
= 122985 + 212850 + 23950
= 359785 l/d

UNIT 4 : INTAKES
What Is Intake?
• An intake is the device or structure placed in the water
source in order to help in safely withdrawal of water by
settling or by using strainer in intake conduit.
• Water can be flown under gravity from intake conduit.
• Water may be flowing under gravity or pumped to the
treatment plant or it may be directly supplied to
reservoir without supplying to treatment plant.

Site Selection For Intake Works
1. It should be located in that place where quality of water is good
and upstream of the sewage disposal point, also not in high slope
not to extract silt.
2. Intake should be deeper so that water is available also in dry
period and cost of impounding dams or barrage is reduced.
3. Location should be such that future expansion ( ie size of intake
increase) is possible if needed.
4. It shouldn’t be located in such places where river is possible to
change its track by meandering.
5. Intake should be located in such places which is less affected by
scouring, silting and flooding and location should be free from
attack of heavy water currents.
6. The site of intake should be well connected by good approach
roads. (or footpath in case of gravity flow rural schemes)
7. Site should be stable and safe from landslides, rock fall etc.

Types of Intake
1. Spring Intake
2. Reservoir Intake
3. River Intake
Spring Intake:
• An intake constructed at the spring source to withdraw water is
called spring intake.
• It is generally constructed in small rural water supply schemes.
• Spring intake should be impervious and provided around the
source to prevent the source contamination and physical damage
by runoff water.
• Simply one or more springs can be joined for greater discharge and
all the sources should be protected from animals, runoff, bathing
etc.
• Protection work is done by fencing, digging ditch drain, planting
hedge etc.

Types of Intake
Reservoir Intake:
• There is a large variation in the discharge of river during monsoon
and summer.
• When there is no sufficient water in the dry period the water in
monsoon is collected in impounded reservoir by constructing weirs
(also overflow excess water) or dams (all water collection) across the
river.
• The intake tower used in such cases is called reservoir intake.
• In case of RCC masonry dams (mostly dams are RCC), intake is
constructed inside the dam itself and only intake pipes are provided
at various levels with control values as in figure above.

Types of Intake
River Intake:
• An intake tower constructed at the bank or inside of the river to withdraw
water is called river intake.
• In a river intake a pump is connected at the bottom of sump well with a
pipe.
• At the end of the pipe a strainer is connected which helps to draw water
without some impurities like pebbles or vegetation.
• To draw water of river to the sump well strainer screens are connected.
• Thus connected water from river in the sump well is pumped to supply to
higher elevation in a reservoir which is ultimately delivered to the users.

Protection Measures For Intake Works
• Intake works should be protected from landslide in its upper
or lower area.
• For this we have to construct retaining walls of gabion,
concrete or stone masonry.
• Drainage ditch in the upper part to collect surface run-off
should be constructed if required by site condition.
• In there is slopy land in upper and lower part of the intake,
bio engineering, i.e..surfing or vegetation can provide stability
to soil to resist it from erosion and landslide.

UNIT 5: QUALITY OF WATER
Wholesome Water
• The water which is not chemically pure ( ie water may contain some
chemicals ) but does not contain anything that may be harmful to
human health is called wholesome water.
• Our body requires certain chemicals and if they are present in water
, their removal is not required.
Requirements of Wholesome Water
• It should be free from bacteria and other pathogenic organism.
• It should be colourless and odour free.
• It should be tasty and cool.
• It should not corrode pipe.
• It should be free from iron, manganese, lead, arsenic and other
poisonous metals and objectionable gases.
• PH should be balanced.(6.5 to 8)
• If it is soft, clothes washing becomes easy.
• It should contain dissolved oxygen.

Potable Water
• Water that is drinkable is called potable water.
• There is no content of those excess minerals that may not be
harmful to health.
Contaminated Water
• Contaminated water is that water whose sources like rivers,
lakes and seas has become impure by fertilizers , pesticides,
sewage, oil or toxic waste from households, lands, ships and
factories.

Impurities in Water
All undesirable substances containing in water in any form is called
impurities in water.
Suspended Impurities
• The suspended impurities in water are because of the presence of
bacteria, algae, clay, silt etc.
• These are those impurities which remain in suspension.
• Some types of bacteria cause disease.
• Suspended impurities cause turbidity in water.
• Besides turbidity presence of algae, protozoa may cause odour and
colour.

Impurities in Water
Colloidal Impurities (not dissolved)
• These are small and non-visible with naked eye which remain
in continuous motion.
• These minerals generally contain organic matters containing
bacteria.
• Their size is between 10-3 mm to 10-6 mm. The organic matters
may be vegetable waste and dead animals.
• Vegetable cause colour , taste and acidity and also bacteria.
• Dead animals produce harmful disease germs.

Impurities in Water
Dissolved Impurities
• Some solid , liquid and gas dissolve in water when it moves
over the rocks and soil etc because water is the good solvent.
• Non-visible organic compounds, inorganic salts and gases are
dissolved in water.
• It makes bad taste, hardness and alkalinity.
• Its concentration is measured in ppm or mg/l.

Hardness of Water
• Hardness is the chemical property of water which is caused by
the presence of bicarbonates, sulphates, chlorides and
nitrates of calcium and magnesium.
• Iron, manganese, strontium salts also may cause hardness
but their presence in most of water is negligible.
Types of Hardness
There are two types of hardness;
1. Carbonate or Temporary Hardness
• The hardness caused by the presense of bicarbonate of
calcium and magnesium is called carbonate or temporary
hardness.
• Since it can be removed by boiling or by adding lime so it is
called temporary hardness.

Hardness of Water
Heating
Mg(HCO3)2 + Heat ⟶MgCO3 + CO2 + H2O
Ca(HCO3)2 + Heat⟶CaCO3 + CO2 + H2O
Addition of Lime Water
Mg(HCO3)2 + Ca(OH)2 ⟶ MgCO3 + CaCO3 + 2H2O
Ca(HCO3)2 + Ca(OH)2⟶2CaCO3 + 2H2O

Hardness of Water
2.Permanent Hardness or Non Carbonate Hardness
• The hardness caused by the presence of sulphates, chlorides
and nitrates of Ca or Mg is called non-carbonate hardness.
• Such hardness from water can’t be removed by simple boiling
but requires special treatment of softening hence it is called
permanent hardness.

Alkalinity in Water
• When PH of water is more than 7, it is said to be alkaline.
• If PH =14 , maximum alkalinity is achieved.
• Generally, alkalinity is caused by hydroxides, carbonates and
bicarbonates but most natural alkalinity is due to
bicarbonates.
• Alkalinity caused by hydroxides is called hydroxide alkalinity
or caustic alkalinity, caused by carbonate is carbonate
alkalinity and caused by bicarbonate is called bicarbonate
alkalinity.
• Mostly drinking water is alkaline due to sweeping of salts
during the flow and decaying of organic matter in water.
• Alkaline water is harmful if taken directly for public water
supply.
• Drinkable range of water is in between 6.5 to 8.

Living Organisms in Water
• The natural water contains various types of living organisms.
• Some organisms are born in water and remain in it due to their
natural habitat.
• Some organisms are introduced in water by man during disposal of
sewage etc in water.
Virus
• It is an unicellular organism.
• It can be plant as well as animal.
• Most of virus are harmful and communicate disease from one
person to another.
• Water may contaminate with virus due to sewage disposal in water
source.
• All viruses are parasitic and grow in the body another living
organisms.
• Viruse cause infections such as hepatitis, yellow fever and variety of
gastro- intestinal disease.

Algae
• It is a photosynthetic plant life with unicellular organs of
reproduction.
• Their nutrients are phosphorus, sulphates etc.
• In fresh water they are generally microscopic size but in salty
waters algae may be several hundred meters in length.
• Sometimes they occur in form of cells and sometimes they grow in
numbers and cover the surface of body of water.
• It develops color, odor, turbidity and taste in water and clogs the
filter and can trouble in treatment plant.
• Hence prevention should be taken for not to clog the filter plants
and other treatment plants.

Worms
• They are organisms of animal life both unicellular as well as
multi-cellular.
• They are visible to naked eyes but ova (eggs) and larva may
not be visible.
• Worms are parasitic in nature and hence create different
problems if inside the human body.
• Round worms, hook worms, tape worms etc. are examples of
worms.
• For prevention from worms care should be taken for
cleanliness of living yards and washing hands before meal and
after toilet.

Bacteria
• Bacteria are unicellular micro-organisms with a simple nucleus.
• They can multiply outside the body also.
• Bacteria present in water may vary from 0.15 to 60 microns in size.
• Bacteria may be harmful and beneficial also. It spreads in optimum
temperature in household disposal.
• For prevention from bacterial diseases care should be taken in sewage
disposal.
On the basis of oxygen consumption, bacteria is classified into (a) aerobic
bacteria ( b) anaerobic bacteria and (c) facultative bacteria.
• Aerobic bacteria is that bacteria which need oxygen for survival.
• Anaerobic bacteria is that bacteria which survives without oxygen and
facultative bacteria is that bacteria which survives in presence or absence
of oxygen.
According to shape, bacteria is classified into (a) spherical (cocci) (b) straight
(bacilli), (c) curved (vibrio), (d) spiral (spirilla) and (e) trichobacteria (flat
and hooked)

According to food consumption, bacteria is classified into (a) parasite and (b)
saprophyte.
• Parasite is that bacteria which survives within the body of living organisms
and also causes disease.
• Saprophyte is the bacteria that does not develop in the living organism
but feed on the waste generated by them or get energy from dead organic
matter like decaying pieces of plants and animals.
According to Causing Disease bacteria is classified into (a) pathogenic
bacteria and (b) non-pathogenic bacteria.
• Pathogenic bacteria is that bacteria which is capable of causing disease.
• Non-pathogenic bacteria is that bacteria which does not cause disease.
According to Temperature bacteria is classified into (a) sychrophilicbacteria ,
(b) mesophilic bacteria and (c) thermophilic bacteria.
• Sychrophilic bacteria is the bacteria which survives in 10 to 20 °C.
• Mesophilic bacteria is the bacteria which survives in 20 to 40 °C.
• Thermophilic bacteria is the bacteria which survives in 40 to 65°C.

Water Related Diseases, Causes and
Prevention
• Some diseases are due to consumption of impure water, some are due to
infection transmitted through aquatic animals and pathogens, some are
transmitted through biting of mosquitoes and some are due to lack of
sufficient water or cleanliness.
• They can be categorized into following types.
Water Borne Disease
• The diseases due to consumption of impure water are known as water
borne diseases.
• They are due to chemicals in water or presence of micro-organism in
water.
• Hence for the prevention of water borne disease water should be free of
germs and it should be wholesome or it should be drinkable.
• Examples of the water borne diseases are Cholera, Typhoid, Paratyphoid,
Diarrhoea, Dysentery etc.

Water Related Diseases, Causes and Prevention
• Water Based Disease
• Disease or infection transmitted through aquatic animals and
pathogens which spend their lifecycle in water is called water
based disease.
• For the prevention of this type of water related disease, we
should avoid the collection of rain water and dirty water near
to our vicinity.
• Water bodies near to our living place should be clean.
• Moreover, we should not be in contact of dirty water where is
possibility of disease causing animals and pathogens.
• Common diseases to this group are Bilharzia, Guinea worm,
Lung flukes, schistosomiasis etc.

Water Related Diseases, Causes and Prevention
Water Vector Transmitted Disease
• It is transmitted through biting of mosquitoes etc., those are
developed near water bodies.
• We should avoid the collection of rain water and we should not
make the near water bodies be dirty to avoid the growth of
mosquitoes etc. in damp places and near to dirty water bodies.
• Disease in this group are malaria, yellow fever, dengue, sleeping
sickness, filariasis etc.
Water Wash Disease
• These are also called water hygiene disease.
• They are due to lack of sufficient water or cleanliness.
• Common diseases in this group are trachoma (eye inflammation),
scabies, fungal infection, lice infection etc.
• For prevention awareness and quantity of water should be
increased.

Transmission Routes
• Water is a mean of transmitting diseases.
• The major diseases that are responsible for most of death in
developing countries are form of fecal-oral group.
• Fecal oral infections may be water born and water washed.
• Organisms from the urine and faeces reach to the water
sources from sewage disposal or any other ways and then this
water is transmitted in the human body orally from the food
or contaminated water and called faecal-oral transmission.
• The pathways of faecal oral transmission are as shown below.

Preventive Measures
Following are the preventive measures for the transmission of diseases
through the faecal oral way.
• Proper arrangement of faeces should be done by making and using
toilets. It should be prevented from mixing in water.
• Hand cleaning should be done properly before meal, after works
and after toilet.
• Food and water should be kept covered.
• There should be arrangement of water in sufficient amount.
• There should be awareness development programmes to make
people aware about their health and hygiene.

Analysis of Water
• Water should be analysed for its physical and chemical qualities.
• In physical analysis it should be tested for temperature, color, turbidity,
taste and odour.
• Water is analysed chemically for determination of total solids,
determination of total dissolved solids and determination of total
suspended solids.
• Similarly the chemical analysis involves taste for PH value and chlorine
content.
• For all these tests sample of water should be taken and the sample should
be stored for certain period.
Water sampling and storing
• For any of tests as physical test, chemical test or biological test , first the
sample water is collected.
• The collection of water follows some simple rules which when not taken
into account may vary the result.
• The water from any source is collected such that it represents the whole
water from that source.

Analysis of Water
Following are the points to be remembered for collecting
and storing water samples.
• In case of rivers , streams, lakes water the surface water
should be avoided because it contains the suspended
matter, so the water should be collected from 40 to 60
cm below the surface.
• For the ground water , sufficient quantity of water should
be pumped out so that floating matter can be removed.
• After the sampling is done the sample water should not
be stored for long time specially for the biological test.
The test should be performed within 24 hours and should
be kept in cool place before test.

Physical Analysis
• Following tests prevail for physical analysis of water sample.
Test for Temperature
• Temperature of water can be measured by digital or ordinary
thermometer.
• For domestic water, temperature should be controlled at about
10°C to 16°C.
• Although , the most desirable temperature is 4.4°C to 10°C, the
water above 26°C is undesirable and more than 35°C is unfit for
drinking purpose.

Physical Analysis
Test for Color
• Colour in water is due to organic matters in colloidal
condition and mineral and dissolved impurities of iron,
manganese etc, decayed vegetable matter, weeds, humus,
plankton ( unicellular plant or animal which are aquatic)
and industrial wastes.
• It makes water in undesirable appearance which is disliked
by the people and it may spoil clothes and affect industrial
process.

Physical Analysis
Platinum cobalt method.
• In this method various standard solutions are made by dissolving various
amount of platinum cobalt in distilled water and the color of water sample
is compared with these solutions using tintometer.
• A tintometer consists of an eyepiece with two holes inside. In one hole
tube of color of standard solution and in other hole tube of color of water
sample are inserted.
• The standard coloured solution is changed until the color of two tubes
matches and the scale of color of the sample becomes same as that of
colored solution where the scale is such that 1 platinum cobalt scale
means 1ppm or 1mg/l. which is the color imparted by 1 mg of platinum
cobalt in 1 litre of water.
• Hence while preparing sample of one platinum cobalt scale we have to
put 1 mg of platinum cobalt in 1 litre of water and required amount of this
is taken in the tube to compare with the sample.

Physical Analysis
Another method
• The platinum cobalt method is not convenient for field use
therefore another method is used in the field.
• In this method the water sample to be tested is compared with
glass colour discs with color compatible to different platinum cobalt
scale.
• For domestic water 5 unit of platinum cobalt scale is permissible.
• However it should not exceed 25 units.
• Color is removed by sedimentation, filtration, aeration and use of
chemicals.

Physical Analysis
Test for Turbidity
• Turbidity is the resistance for light to pass through the water
sample.
• Turbidity is created due to presence of suspended matters such as
clay, silt, finely divided organic and inorganic matters etc.
• Filtration of water is more difficult and costly with the increase in
turbidity.
• If turbid water contain sewage solids these sewage solids may be
incased with matters of turbidity and disinfection may not become
effective.
• It is measured in the terms of ppm or mg/l, NTU ( Nephelometric
Turbidity Unit) or JTU ( Jackson Turbidity Unit).

Nephelometer and digital turbidity meter
These are the modern commercial turbidity meters , which give turbidity
value directly in digital display after calibration with standard turbidity
solutions.

Physical Analysis
Turbidity Rod or Tape
• It is a simple and reliable method for the measurement of turbidity
of a water sample.
• It is the graduated aluminium or steel rod of 203 mm long which is
graduated to give turbidity in ppm.
• One platinum needle of 25 mm long and 1mm diameter is fixed at
the lower end .
• The eye is kept constant at the eye mark and the rod is emerged in
the water sample under standard light conditions.
• As soon as needle disappears the corresponding reading is noted
which is turbidity of water sample in ppm.

Physical Analysis
Turbidity Tube
• A tube is calibrated from 0 to 120 cm.
• A painted disc is placed at the bottom of the tube and the bottom is
covered with a PVC cap.
• Water is poured from top of the clear tube and observed for light from
the top.
• The level of water at which the image of the color disc ceases to be seen
is noted in cm.
• Different levels of turbidity can be observed for different sources of water.
• Standard level of water in cm which has been defined earlier by practice
for allowable turbidity should not be exceeded by the water sample.

Turbidity tube and turbidity comparasion

Physical Analysis
Jackson Turbidity Meter
• It is most commonly used method for the measurement of turbidity above
50 ppm.
• It consists of a graduated glass tube or a turbidity tube placed in a metal
cylindrical container or an annular tube which is supported in standard
stand and a standard candle is placed in the candle holder as shown in
figure.
• To measure the turbidity, candle is lighted, some quantity of water is
placed into the glass tube or the turbidity tube and image of candle is
observed from the top of this glass tube.
• The depth of the water is increased by adding sample to the tube till the
image of the candle ceases to be seen.
• The depth of water at this stage is noted and turbidity with respect to this
height is determined from standard table.

Physical Analysis
Test for Taste
• Taste and odor are closely related and they may be in water due to the
action of dead and living micro-organisms, dissolved gases like hydrogen
sulphide, methane, carbon dioxide, minerals (Iron compounds, sodium
chlorides, sulphates) and so on.
• Taste and odor in water sample is very difficult to find out by any
experiment . However, smelling and tasting may be the effective method
to find out contamination.
• The taste and odor is measured in terms of threshold number.
• The taste of water is measured by flavor threshold test. In this test the
water sample to be tested is diluted with water free from taste to such
extent that the mixture becomes taste free. Then flavor threshold number
(FTN) can be defined as
FTN = (A + B)/A (always more than 1, the amount in which there
is no taste)
Where,
A = volume of water sample in ml.
B = volume of water free from taste added to sample in ml.
Hence less the FTN purer is water. Thus FTN should be very low.

Physical Analysis
Test for Odor
• The odor of water is measured by threshold odor test.
• In this test the water sample to be tested is diluted with water free
from odor to such extent that the mixture becomes odor free.
• Then threshold odor number (TON) can be defined as
TON = (A + B)/A (always more than 1, the
amount in which there is no odor)
Where,
A = volume of water sample in ml.
B = volume of water free from odor added to sample in ml.
Hence less the TON purer is water. Thus TON should be very low.

Chemical Analysis
In chemical analysis we determine total solids that consists the solids in
suspension, colloidal and dissolved forms. We also determine the total
dissolved solids and the total suspended solids in separate tests.
Determination of Total Solids (TS)
• Total solids mean the solid in suspension , colloidal and dissolved form.
• Place 100 to 300 ml of water in a crucible and it is evaporated to dryness
in an oven at 105°C. Weight of dry residue left in the crucible is taken.
• Total solid can be determined by dividing weight of dry residue left in
crucible in mg
by volume of water sample taken in crucible in litre
Determination of Total Dissolved Solids (TDS)
• Whatman filter paper of no. 44 is taken and measured volume of filtered
water through this filter paper is taken in a crucible. Then it is evaporated
to dryness in an oven at 105°C. Weight of dry residue in the crucible is
taken.
• Total dissolved solid is determined by dividing weight of residue left in
crucible in mg by volume of water sample taken in crucible in liter.

Chemical Analysis
Determination of Total Suspended Solids (TSS)
• We can determine total suspended solids by using the relation
TSS = TS –TDS.
Or alternatively ;
• Whatman filter paper of no. 44 is taken and the known
volume of water is filtered. Weight of dry residue left on the
filter paper is taken.
• Then total suspended solids can be determined by dividing
weight of dry residue left in filter paper in mg by volume of
water sample filtered in liter.

Chemical Analysis
Test for PH Value
• PH value indicates the acidity or alkalinity of water. Neutral
water has PH value 7.If PH value is less than 7 the sample will
be acidic otherwise it will be alkaline.

Chemical Analysis
PH is determined by the calorimetric or the electrometric method.
Colorimetric Method
• In colorimetric method , the color of water sample is compared
with standard color disc of different PH value after addition of
indicator such as methyl orange, methyl red etc in the sample.
• The color disc corresponding to different indicators with different
PH value is available.
Electrometric Method
• In this method the instrument measures the PH and displays in the
digital display in the range of 0 to 14.This method is more fast and
reliable.
For drinking purpose we have to try to bring PH value near to 7. PH
value 6.5 to 8 allowable.

Calorimetric and Electrometric Test Set

Chemical Analysis
Test for Chlorine
• Chlorine may be present in water in form of disinfectant.
• Some amount of chlorine remains in water after the treatment
process or the chlorination.
• This remaining chlorine in water is called residual chlorine which is
useful to destroy pathogenic organisms which still remain.
• The residual chlorine is very important for drinking water whose
range should be in between 0.05 to 0.2 ppm.
• Its content is calculated with the help of starch iodide test.

Chemical Analysis
Test for Dissolved Oxygen
• Winkler test is used to determine the concentration of dissolved oxygen
in water samples.
• In this test an excess of manganese salt, iodide (I-) and hydroxide (OH-)
ions are added to a water sample causing a white precipitate of Mn(OH)2
to form.
• This precipitate is then oxidized by the oxygen that is present in the water
sample into a brown manganese.
• A strong acid (HCl or H2SO4) is added to acidify the solution.
• Trivalent manganese is produced on acidifying the brown suspension.
• Trivalent manganese is directly reacted with EDTA (
ethylenediaminetetraacetic acid) to give a pink colour.
• This pink colour is compared with color discs since more the dissolved
oxygen in water more is formation of brown manganese , more the
formation of trivalent manganese on acidifying and more the formation of
pink color on adding EDTA to the trivalent manganese.

UNIT 6: TREATMENT OF WATER
Objectives of Water Treatment
Raw water may contain suspended, colloidal and dissolved
impurities. The purpose of water treatment is to remove all those
impurities which are objectionable either from health point of view
or from colour, odour and taste point of view. Following are the
needs for the water treatment.
• Water treatment is needed to reduce the objectionable colour,
odour, turbidity, hardness and taste.
• Treatment is needed to kill pathogens harmful to human health.
• Water treatment is needed to make water safe and potable for
drinking.
• Treatment is needed to eliminate corrosive nature of water to avoid
corrosion of pipes and boilers.
• Water treatment is needed to make water suitable for a wide
variety of industrial purpose.
• It is needed to remove harmful gases dissolved in water.
• It is needed to make water suitable for a wide variety of industrial
purpose.

Screening
The process followed by passing water through screens to remove large
suspended matters like sticks, branches of tree, leaves, dead animal body,
pebbles, ice etc. and other small suspended matters is called screening.
There are two types of screens which are used for the process of screening.
1) Coarse Screen
• Coarse screens are generally placed in front of the fine screens at the inlet
to remove large suspended and floating matters from surface sources.
• These screens are generally called trash rack or bar screen and consists of
bar grills of 25 mm diameter.
• If openings are of 50mm to 150mm it is called as coarse screen and if it is
20mm to 50mm it is called medium screen.
• Mostly bar screens are kept inclined so that they can be cleaned easily
with a rake and to increase flow area of water.
• The slope of inclined bars is 3 to 6 vertical to 1 horizontal.
• The bars are supported at the bottom by base support and by support
beam at the top. The sketch of bar screen is provided as under.

section and plan of bar screen

Screening
2) Fine Screen
• It is used to remove smaller suspended impurities at the surface or ground
water intakes, sometimes alone or sometimes following a bar screen.
• Fine screens are usually drums perforated with holes of about 6mm
diameter and called drum strainers.
• Fine screens normally get clogged and are to be cleaned frequently.
• So they are avoided nowadays for surface intakes and fine particles are
separated in sedimentation.

Plain Sedimentation
Purpose
• To remove suspended particles such as silt, sand, clay etc.
• To reduce load in subsequent treatment plants.
• To reduce load in pipes and fittings.
Ideal Sedimentation Tank
A sedimentation tank is ideal if the length and depth of tank is
enough to settle down all moving suspended particles in its
way and breadth also enough to contain the whole discharge.

Plain Sedimentation
Types of Sedimentation Tank
Depending upon the method of operation there are two types.
1) Fill and Draw Type Sedimentation Tank
2)Continuous Flow Type Sedimentation Tank
Depending upon the shape there are three types.
1)Rectangular tank
2)Circular tank
3)Hopper bottom tank ( bottom length and breadth are less than top
length and breadth )
Depending upon the direction of flow of water.
1)Horizontal flow tanks (length more than depth)
2)Vertical flow tanks (depth more than length)

Plain Sedimentation
Fill and Draw Type Sedimentation Tank
• This tank is normally rectangular in plan.
• The water is first filled and then allowed to some detention period
of normally 24 hours for sedimentation of particles.
• The clear water is drawn from outlet and tank is then made empty
and cleaning of sediment is done.
• After cleaning, again the filling and emptying process is similarly
repeated.
• These tanks need long detention period, more labor and
supervision.

Plain Sedimentation
Continuous Flow Type Sedimentation Tank
• In continuous flow type sedimentation tank raw water is
continuously admitted into the tank and allowed to flow slowly in
the tank during which the particles in suspension settle down and
clear water flows out continuously from the tank.
• These tanks work on the principle that by reducing the velocity of
flow of water a large amount of suspended particles present in
water can be made to settle down.
• The velocity of flow of water in these tanks is reduced by providing
sufficient length of travel for water in tank.
• Time taken by a particle of water to move from inlet to outlet is
slightly more than that required for settling of a suspended particle
in water.
• The continuous flow type sedimentation tanks may be rectangular,
square or circular in shape.

Plain Sedimentation
Design of Horizontal Flow Sedimentation Tank
Here,
Time of settling of suspended particle = ts = time of horizontal flow or time of
discharge to flow distance L ie. sludge zone = td
We have,
velocity of discharge Vd= Q/ BH
Also; Vd = L/ td
Then td = L/ Vd = LBH/Q.

Plain Sedimentation
For settling of suspended particles, the particles should take time not
less than td.
ie. td should be more than ts
So, let; ts= td.
= LBH/Q
Again,
Vs.= H/ ts
ie. ts.= H/ Vs
Equating; H/ Vs = LBH/Q
Hence; Vs = Q/LB = Q/A
The suspended particles having velocity more than Q/A will settle
before discharge reaches to outlet zone or flows from the
sedimentation tank.Vs is known as surface overflow rate (SOR)
which is taken 15-30 for design.

Plain Sedimentation
If Vs = 20 is taken;
Vs = Q/LB
Or; 20 = Q/LB
L and B can be found from L/B≤ 5 = 3 to 5.
Let L/B =4
Or; L=4B
Then; 20= Q/ 4B*B
Since Q is known; B can be found.
Once B is found; L can be found.
H is taken = 3- 3.5 m which is standard for any discharge.

Sedimentation with Coagulation
• If sedimentation is done by adding certain chemicals to accelerate settling
of fine suspended particles as well as to allow settling of colloidal particles
then it is known as sedimentation with coagulation.
• Very fine suspended clay particles are not removed by plain sedimentation
explained earlier. Particle of 0.06 mm size requires 10 hours to settle in 3
m deep plain sedimentation and 0.002 mm particle will require 4 days for
settling.
• This settling time is impracticable. Therefore we need sedimentation with
coagulation.
• Colloidal particles being charged particles and in continuous motion do
not get sediment in plain sedimentation.
• The detention time required in sedimentation, coagulation will greatly
reduce.
• The size of tank required is also smaller.
• In rural water supply projects it is not feasible to apply chemicals regularly
but in urban water supply system sedimentation with coagulation may be
necessary .

It removes following types of impurities
1) fragments of animal and vegetable matters
2) Plankton
3) finely divided matter including colloidal matter
4) organic coloring matter
5)some bacteria and viruses and
6)also turbidity, odour and taste producing substances

Process of Coagulation
1. Feeding of Coagulant
Coagulant may feed to water in dry or wet form known as dry feeding or wet
feeding. Wet feeding means feeding after making solution.
2. Mixing of Coagulant
After the addition of coagulants to raw water it is thoroughly (whole part) and
vigorously (with great speed) mixed so that the coagulants get fully
dispersed into the entire mass of water.
Mixing basin with baffle walls
For mixing process basins with baffle walls are used. These basins may be
horizontal or vertical with proper arrangement of baffle walls. The
disturbance created by the presence of baffle walls in the path of flowing
water cause vigorous agitation of water which thoroughly mixes water
with coagulant.

2 types of mixing with baffles

3. Flocculation
• From the mixing basin, water is taken to flocculator for flocculation.
• In a flocculator slow stirring of water is brought about to permit
build up of floc particles.
• There are various types of flocculators but the mechanical
flocculators are most commonly used.
• It consists of a tank provided with paddles for stirring water hence
it is called paddle flocculator.
• It may be longitudinal flow flocculator or vertical flow flocculator.

4. Sedimentation
• The water from the flocculator is taken to the sedimentation tank also
called coagulation tank or clarifier.
• It consists of floc chamber and sedimentation tank.
• The depth of floc chamber is usually kept about half the depth of
sedimentation tank.
• The cleaning period for this tank is usually 3 to 6 months.

Types of Coagulant
Following are the commonly used coagulants .
1. AluminiumSulphate or Alum .Al2(SO4)3.18H2O
• It is available in powder or liquid form.
• Its dose is 10 to 30 mg per litre of water.
• It is cheap, effective and widely used.
• If raw water contains no alkalinity we have to add it by adding
lime or soda ash since to use alum and form floc it is
necessary that water should have some alkalinity.

If water already contains bicarbonate alkalinity,
Al2(SO4)3.18H2O + 3Ca(HCO3)2 →2Al(OH)3↓ + 3CaSO4 + 18H2O +
6CO2↓
If lime is added,
Al2(SO4)3.18H2O + 3Ca (OH)2→2Al(OH)3↓+ 3CaSO4 + 18H2O
If soda ash is added,
Al2(SO4)3.18H2O + 3Na2CO3→2Al(OH)3↓ + 3Na2SO4 + 18H2O +3CO2
Al(OH)3 settle in clarifier and CaSO4 and Na2SO4 are not harmful to
health though it remains in water.
Amount of alum required depends upon turbidity and color of raw
water. Usual dose is 5 mg/l for relatively clear water to 30mg/l for
high turbid water.

2.Iron Salts
Ferrous Sulphate .FeSO4.7H2O
It is also called copperas and used with lime. Amount depends
on turbidity, alkalinity and free carbondioxide.
FeSO4.7H2O + Ca (OH)2→Fe(OH)2↓ + CaSO4 + 7H2O.
The ferrous hydroxide Fe(OH)2 is an efficient floc which soon
oxidize by dissolved oxygen in water forming more amount
which settle down and taken as sludge from bottom of the
clarifier.
Fe(OH)2 + O2 + 2H2O→ 4Fe(OH)2↓

Ferric Chloride. FeCl3
It may be used with or without lime.
2FeCl3 + 3Ca(OH)2→ 2Fe(OH)3 ↓ + 3CaCl2
Fe(OH)3 ie ferric hydroxide is a floc which settle at the bottom of
the clarifier and taken as the sludge.
Ferric Sulphate.Fe2(SO4)3
Fe2(SO4)3 + 3Ca(OH)2→3CaSO4↓ + 2Fe(OH)3
CaSO4 ie. Calcium sulphate settle as a floc and this can also be
taken away from the bottom of the clarifier.

3. Chlorinated Copperas. FeCl3. Fe2(SO4)3
The mixture of ferric chloride and ferric sulphate is called
chlorinated copperas and prepared by 1part chlorine and 7.8
parts ferrous sulphate.
6(FeSO4.7H2O) + 3Cl2 → 2( FeCl3. Fe2(SO4)3) + 42H2O.
It when added to water forms a tough floc which is removed in
sedimentation from the bottom of the clarifier.

4.Sodium Aluminate. Na2Al2O4
It is sometimes used as coagulants. When it is mixed in water it
reacts with salts of calcium and magnesium and forms the
precipitate of calcium and magnesium aluminate which can
be taken out as sludge from the bottom of the clarifier.
Na2Al2O4+Ca(HCO3)2→CaAl2O4↓ + Na2CO3 + CO2↑ + H2O
Na2Al2O4+ CaCl2→CaAl2O4↓ +2NaCl
Na2Al2O4+ CaSO4→CaAl2O4↓ + Na2SO4
This removes temporary and permanent hardness also.

Factors Affecting Coagulation
Following are the factors which affect coagulation
(i) Kind of coagulant
(ii) Quantity of coagulant
(iii) Amount, type of color and turbidity of water.
(iv) The PH value of water.
(v) Time period of mixing and flocculation
(vi) Temperature
(vii) Violence of agitation

Determination of Optimum Dose of Coagulant
• Jar test is conducted for determining optimum dose of coagulant.
• In jar test there are commonly 6 number of jars or beakers which
are placed in their places to which light is given from the bases of
them.
• There are movable blades which are dipped into the beakers
containing same samples of water and different dozes of coagulants
those described earlier.
• The rotation of blades agitates the samples and the dose of
coagulant which gives the most clear water is selected to be the
optimum dose.
• If clear water couldn’t be obtained in first trial, repeated trials
should be done.

Filtration
• The process of passing the water through a bed of filtering media is
called filtration. Sedimentation process removes the large particles
only which can settle down at the bottom.
• There are some particles which never settle down and thus for
removing such particles, bacteria, colour, dissolved minerals,
filtration is used.
Theory of Filtration
The process of filtration is explained by experts in different ways which
can be classified and explained in the following ways.
Mechanical Straining
• It states that the larger particles cannot pass through the pores in
between sand.
• The pore size continuously becomes smaller due to use and hence
the smaller particles are also checked in the sand layer.
• The floc which does not settle in the coagulation tank is checked by
the layers of filtering media in the filter.

Filtration
Sedimentation
• The interstices between the sand grains act as a small
sedimentation tank where the suspended matters and very small
particles like bacteria and colloidal particles settle.
Biological Action
• The organic impurities in the water become food for the micro-
organisms.
• These micro-organisms decay the organic matters and form a layer
at the top of sand bed which is called dirty skin.
• Micro-organism feeding on the dirty skin remains at the top layer
and act on the incoming organic matters.

Filtration
Electrolytic Action
• As per ionic theory, when two substances of opposite charges come
into contact, the charge is neutralized and in doing so, new
chemical substances are formed.
• Sand particles in filter media also have charges of some polarity
which attracts the suspended , colloidal and dissolved matters of
opposite polarity.
• In neutralizing new, heavy chemicals are formed which settle down.
• After a long use charges in sand grains get exhausted by coating of
new chemicals and thus it becomes necessary to clean filter for
regeneration of charges.

Filtration
Types of Filter
• There are three types of filter which are classified according to design and
time period required for filtering water. They are classified as slow sand
filter, rapid sand filter and pressure filter. Slow sand filter and rapid sand
filter are called gravity filters.
Slow Sand Filter
• This filter is called slow sand filter because rate of filtration is slow in slow
sand filter.
• Bed cleaning needs a lot of labours and hence this filter is very costly.
Working and Cleaning of Slow Sand Filter
• Water from sedimentation tank enters the filter through inlet, then passes
through filter media (sand and gravel) and then the purified water is
collected from under the filter media and comes out from outlet to clear
water reservoir
• The top layer of sand is scrapped after long use and needs washing. The
washed sand can be used again.
• Cleaning of slow sand filter is done after 1 to 3 months.

Filtration
Filter Media for Slow Sand Filter
• It consists 90 to 110 cm thick sand layer with size of sand 0.25
to0.35 mm.
• Finer the sand better will be the removal of turbidity and
bacterial removal efficiency but lowers the filtration rate.
• The sand layer is supported on base material of 30 to 75 cm
thick gravel bed.
• Gravel bed has four layers with 3 to 6 mm, 6 to 20 mm, 20 to
40 mm and 40 to 65 mm size gravel.
• Each layer is about 15 cm thick.

Filtration
Rapid Sand Filter
Working of Rapid Sand Filter
• Watercollects in inlet chamber and enters the filter through inlet valve.
• Water enters the gutters which are laterally placed and then enters to fine
sand filter media.
• Water infiltrates through coarse sand to the layer of pebbles. In this step
water is fully filtered.
• There are holes to enter water in the lower part of the CI collecting pipe
through which filtered water goes out through the outlet valve. Lateral
pipes are connected to this main filter water collecting pipe.
• Compressed air pipe is connected to the layer of coarse sand with lateral
and longitudinal pipes to clean the filter media.
• Suspended and other organic matters collect above the filter media,
hence washing frequently is needed.
• By opening the wash water valve the collected dirty particles pass through
the wash water pipe collecting in the wash water channel.
• Continuous filtering of water is possible because cleaning or washing of
dirty particles above the filter media and cleaning the coarse sand by
compressed air is possible whenever needed to function the filter
continuously.

Filtration
Filter Media For Rapid Sand Filter
• Free from dirt and clay, filter media consists 60 to 90
cm thick sand layer with effective size of sand 0.35 to
0.60 mm.
• The sand layer is supported on base material of 45 to
60 cm thick gravel bed.
• There are four layers for gravel bed with each layer
maximum 15 cm thick and layers have sizes of gravel as
2 to 6 mm, 6 to 12 mm, 12 to 20 mm and 20 to 50 mm
from the top

Filtration
Pressure Filter
• It is a rapid sand filter consists of a closed steel cylindrical tank
in which water is passed under pressure of 3-7 kg/cm2
through pumping.
• Pressure is controlled with the help of pressure gauge.
• Raw water with coagulant commonly alum is fed directly to
this tank where coagulation also directly takes place inside it.

Filtration
• Raw water enters from inlet valve which passes through sand
and gravel bed and it enters to central drain through lateral
drains.
• Lateral drains have perforations in their under part and these
are connected to central drain.
• These drain pipes are covered with a perforated steel plank
from which filtered water from gravel media passes to the
lateral drains and the central drain.

Filtration
Filter Media For Pressure Filter
• Free from dirt and clay, filter media consists 60 to 90 cm thick sand layer
with effective size of sand 0.35 to 0.60 mm.
• The sand layer is supported on base material of 45 to 60 cm thick gravel
bed. There are four layers for gravel bed with each layer maximum 15 cm
thick and layers have sizes of gravel as 2 to 6 mm, 6 to 12 mm, 12 to 20
mm and 20 to 50 mm from the top
Portable Filter in Emergency
• Water if not purified and filtered in the supply we use portable and
potable water filtration.
• For this various types of filters are available which can be used homely.

Disinfection
The meaning and purpose of disinfection is to kill bacteria and micro
organism which cause disease and make water safe for drinking.
Methods of Disinfection
• There are different methods of disinfection; some are applicable
only for small scale and some for large scale.
Boiling
• Boiling of water kills pathogenic bacteria and makes water safe to
drink.
Excessive lime Treatment
• Lime is usually used for reducing hardness of water. If extra lime is
added then it will disinfect the water while removing the hardness.
• Excess lime in water increases PH value of water. If PH value
increases more than 9.5, all the bacteria are killed.

Iodine and Bromine Treatment
• Addition of Iodine and Bromine in water kills all the pathogenic
bacteria. The quantity of Iodine and Bromine should not exceed 8
ppm (mg/l) and they can kill bacteria in minimum contact period of
5 minutes. These are found in form of pills and very handy.
Ozone Treatment
• Ozone is used in gaseous form, blue in colour. It is unstable form of
oxygen containing 3 atoms of oxygen.
• First ozone should be prepared by
.
•This ozone is unstable and breaks down liberating nascent oxygen in
normal condition
Disinfection

Disinfection
• Nascent oxygen kills all the bacteria.
• Water enters a chamber containing ozone gas through the inlet and
comes out from outlet where it is disinfected.
• Ozone dose is 2 to 3 ppm. It also removes colour, odour and taste.
Ozone generators

Disinfection
Potassium Permanganate Treatment
• This is most common disinfectant used in village for disinfection of
dug well water, pond water or private source of water.
• In addition to the killing of bacteria it also reduces the organic
matters by oxidizing them.
• A small amount of KMnO4 is dissolved in a bucket of water and
mixed it in water of well frequently to kill the bacteria.
• Dose of KMnO4 is 1-2 mg/litre of water. Contact period is 4 to 6
hours. It kills only 98%of pathogenic bacteria.
Silver Treatment or Electro-Katadyn Process
• Metallic silver ions are introduced into water by passing the ions
through silver electrode tubes by passing the current through 1.5 V
DC battery.
• The introduction of silver ions in water is highly effective and kills
100% bacteria.

Disinfection
Ultraviolet Ray Treatment
• Water is allowed to pass in thickness not exceeding 10 cm
before the ultraviolet rays. These rays penetrate the water
and kill the bacteria.

Disinfection
• Ultraviolet ray is produced in the ultraviolet germicidal
lamp.
• The intensity of ray is controlled by the ultraviolet
intensity moniter.
• Frequent cleaning of the lamp is needed and is done by
tube cleaner.
• There is provision of outer shell pressure vessel to
entrap the ultraviolet rays inside the chamber.
• Untreated water enters the tube from inlet and is taken
from outlet in other end.

Disinfection
• Bottles filled with water can be placed in places coming direct
sunlight where u-v rays coming together with sunlight penetrates
the water in the bottle and treated by u-v rays and kills bacteria.
• The bottles should have diameter less than 10 cm.
• This method is known as sodis method.
sodis method

Disinfection
Chlorination
• Chlorine in its various forms is the most widely and universally adopted
product for disinfecting water. It is reliable, cheap and not very difficult to
handle. The chlorine reacts with water and forms hydrochloric acid and
hypochlorous acid.
Cl2 + H2O →HCl + HOCl
HOCl→ H+ + OCl-
• The HOCl ionizes into hydrogen ions (H+) and hypochlorite ions (OCl-). Thus
the hypochlorous acid and the hypochlorite ions accomplish the
disinfection. The disinfection is rapid when the PH value is about 7 or
slightly more.
• The chlorine is added to the water in pipe leading from the filtered water
reservoir to the distribution mains so that the sufficient contact period is
ensured.
• However; if the water is highly polluted it will be more advantageous to
add some chlorine into the suction pipes of raw water pumps before any
other treatment is given. This is called pre-chlorination.

Disinfection
Chlorination contd…..
• The storage of chlorine should be sufficiently cured because it forms a
very explosive gas when mixed with CO. Also since it is poisonous,
sufficient ventilation should be provided to take care of leakage of
chlorine.
• Adding of chlorine in water in large volume treatment is possible and is
termed as chlorination.
• The quantity of chlorine required to be added to water to leave 0.2 mg/l
or ppm of freely available residual chlorine after 10 minutes of contact
period is called optimum dose of chlorine.
• This is generally of about 1 ppm but for surface water it is 0.5 to 1.5 ppm
and it may be as high as 3 ppm for highly polluted waters.
• In lab, various doses of chlorine are added to some quantity (equal
volume for all doses) of water and tested after 10 minutes of contact
period.
• The dose which leaves 0.2 ppm of free residual chlorine is taken as the
optimum dose of chlorine.
• The presence of this residual chlorine in water ensures check for further
presence or entering of bacteria in water and hence makes water
sustainably pure or treated.

Disinfection
Chlorination contd….
• Generally, the chlorine is supplied in steel cylinders compressed into liquid
form (i.e.liquefied gas).
• A number of dosing apparatus are available for applying chlorine either by
manual control or to give a fixed dose etc.
• The chlorine is generally allowed to come in contact with water at least
for 10 to 15 minutes and water is thoroughly agitated.
• Usually it takes 30 to 45 minutes to kill the bacteria. The application of
chlorine depends upon the type of water we are dealing with.
• If water has no chlorine demand, any chlorine added to such water will
appear as residual chlorine and hence relation between applied and
residual chlorine will be as indicated by line A having slope of 45°.

Disinfection
• However, water generally has some chlorine demand and when
chlorine is added it first reacts with compounds such as ammonia,
proteins, chloramines and hence residual chlorine is obtained then
only (increased amount of chlorine) it performs the function of
killing of bacteria ,therefore more addition of chlorine suddenly
drops the amount of residual chlorine and further addition of
chlorine again produces the residual chlorine.
• Any further addition now produces residual chlorine completely in
water.
• The sudden increasing point of residual chlorine is called break
point chlorine and if this volume is applied then known as break
point chlorination (or no further chlorination needed).

Disinfection
Chlorination contd…..
• This can be enterpreted in graph.
• The line OAB shows increase of residual chlorine in addition of
chlorine to water upto application of dose to point 4.
• Upto application to point 4 the volume is not sufficient to react
with bacteria but sufficient even more for reaction with ammonia,
protein, chloramines etc.
• After application is further increased chlorine starts reacting with
bacteria and chlorine residual drops down quickly upto point C.
• Since there is no function of chlorine after any addition this point is
called break point chlorination.

chlorination contd…..
break point chlorination
In the above curve
O to A : Initial stage, total residual chlorine.
A to B : less residual chlorine because chlorine reacts with compounds as
ammonia, proteins, chloramines etc.
BC : sudden decrease in residual chlorine because chlorine reacts with bacteria
or kills it.
CD : full residual chlorine – equal amount as applied dose.

Disinfection
Chlorination Contd…
Effects of Break Point Chlorination
• It removes taste, odour and manganese.
• It kills all bacteria.
• Desired amount of residual chlorine can be kept after break point.
• It completes oxidation of other compounds such as ammonia, proteins etc
Super Chlorination
• Application of chlorine beyond the break point chlorination is called super
chlorination which increases residual chlorine.
• Generally 2 to 3 ppm beyond the break point is applied as super
chlorination thus increased residual chlorine may be effective to kill all
pathogens during epidemics.
De-chlorination
• The process of removing excessive chlorine (residual chlorine) from water
before distribution to the consumers to avoid chlorine taste is known as
de-chlorination and for this aeration or adding some chemicals can be
done.

Disinfection
Factors Affecting Chlorination
1) Turbidity
More the turbidity, less the bacterial efficiency of chlorine ie. more chlorine is
needed.
2) Presence of metallic compound
More chlorine is needed if there are metallic compounds.
3) PH value of water
If PH is high in water or there is alkalinity then alkalis react with chlorine
forming HOCl and this delays affecting bacteria.
e.g.2NaOH + Cl2 →2HOCl + 2Na.
4) Type, condition and concentration of micro organism
Efficiency becomes low if the favourable condition for bacteria is available
and concentration of bacteria is high. For virus more volume of chlorine is
needed.
5) Time of Contact
For effective chlorination, the time of contact should be at least 30 minutes.

Water Softening
• If water contains some chemicals ie. bicarbonates of calcium and
magnesium that causes hardness in water which is called
temporary hardness.
• If water contains sulphate and chloride of calcium and magnesium
the hardness thus developed is termed as permanent hardness.
• Removal of both of the hardnesses is called softening of water.
Hardness in water causes difficulty in washing.
Removal of Temporary Hardness
1) Boiling
• Temporary hardness can be removed by boiling the hard water.
Bicarbonates of Ca and Mg change into insoluble carbonates which
can be removed by sedimentation process in sedimentation tank.
For large scale it is costly.
Mg(HCO3)2 + heat→ MgCO3 + CO2 + H2O
Ca(HCO3)2 + heat → CaCO3 + CO2 + H2O.

Water Softening
2) Lime Treatment
• Temporary hardness can also be removed by adding lime in water. Hence
Mg(HCO3)2 + Ca(OH)2→ MgCO3 + CaCO3 + 2H2O
Ca(HCO3)2 + Ca(OH)2→ 2CaCO3 + 2H2O
Removal of Permanent Hardness
1) Lime Soda Process
Permanent hardness of water which is caused by sulphates and chlorides of
Ca and Mg canbe removed by adding lime ie. Ca(OH)2 and soda ie. Na2CO3.
The chemical reactions are as under.
MgSO4 + Ca(OH)2→Mg(OH)2 ↓ + CaSO4 .
MgCl2 + Ca(OH)2→Mg(OH)2 ↓ + CaCl2.
MgCl2 + Na2CO3→MgCO3 ↓+ 2NaCl.
CaSO4 +Na2CO3→CaCO3↓+ Na2SO4
CaCl2.+ Na2CO3→CaCO3↓+ 2NaCl.
Mg(OH)2 , CaCO3 and MgCO3 are insoluble in water and removed by
sedimentation. Other products are soluble and do not impart in hardness.

Water Softening
• Raw water is entered to the chamber from one side of the
rectangular tank.
• Similarly lime and soda are entered to the chamber from another
side of the chamber.
• Then water with these chemicals are agitated with the help of
blades.
• Blades are connected to the central shaft and the end of the shaft
outside the chamber is provided with a stirrer.
• Chemicals are mixed thoroughly in water while rotating the shaft by
the stirrer. Mg(OH)2 , CaCO3 and MgCO3 which are settled at the
bottom of the chamber and are taken out as sludge.

Water Softening
lime soda process

Water Softening
Zeolite or Base Exchange or Ion Exchange or Ionization Process.
• It also removes temporary hardness and is commonly used process.
• Zeolite is a natural or artificial granular substance. Natural zeolite is
green in colour and artificial is white and the zeolite is also called
permutit.
• The commonly used permutit is sodium aluminium silicate
(SiO2.Al2O3.Na2O).
Hence;
2SiO2Al2O3Na2O + Ca(HCO3)2→2SiO2Al2O3CaO + 2Na(HCO3).
2SiO2Al2O3Na2O + CaSO4→2SiO2Al2O3CaO + Na2SO4.
2SiO2Al2O3Na2O + CaCl2→2SiO2Al2O3CaO + 2NaCl
2SiO2Al2O3Na2O + Mg(HCO3)2→2SiO2Al2O3MgO + 2NaHCO3
2SiO2Al2O3Na2O + MgSO4→2SiO2Al2O3MgO + Na2SO4.
2SiO2Al2O3Na2O + MgCl2→2SiO2Al2O3MgO + 2NaCl.

Water Softening
Here the compounds of 2SiO2Al2O3CaO and 2SiO2Al2O3MgO are insoluble and
settle inside the chamber above the permutit. Hence permutit should be
regenerated by adding NaCl.
Hence
2SiO2Al2O3CaO + 2NaCl →2SiO2Al2O3Na2O + CaCl2
2SiO2Al2O3MgO +2NaCl→2SiO2Al2O3Na2O + MgCl2
zeolite process

Water Softening
ZeoliteProcess
• In this process hard water is entered from top of the chamber from
the inlet.
• There is provision of gravel packing above a certain height from the
bottom of the chamber.
• Above the gravel bed zeolite bed is provided.
• Compounds of 2SiO2Al2O3CaO and 2SiO2Al2O3MgO formed after
reaction of bicarbonates, sulphates and chlorides of calcium and
magnesium with zeolite are insoluble and settle inside the chamber
above the zeolite bed.
• Softened water infiltrates below the gravel bed and passes through
the soft water outlet.
• Some floating impurities formed in the process are removed from
the outlet to the sink.
• There is storage of brine solution ie. the solution of common salt
side by side.
• Aftera log use zeolite ceases to function and brine solution is
injected from the tank to the softening chamber where the
regeneration of zeolite takes place.

Miscellaneous Treatments
Aeration
• Aeration is a method used to bring the water into contact with the
atmospheric air so that oxygen is absorbed from air and
objectionable gases, odour, taste etc are released in atmosphere.
• Iron, manganese and other organic impurities are also removed by
aeration.
• Excessive aeration causes excessive oxygen absorption which
further increases corrosion of pipes.
Methods of Aeration
• Aerators can be categorized as gravity aerators, spray aerator and
diffuse aerator.
• Gravity aerators can be further classified as cascade aerator,inclined
aerator, salt tray aerator and gravel bed aerator.

Free Fall or Gravity Aerators
1.Cascade Aerator
• Water is allowed to fall 1 to 3 m height over a series of 4 to 6 concrete
steps in thin film.
• During falling, water is mixed with air and gets aerated. It removes 20 to
45% carbon dioxide and 35% of hydrozen sulphide.

2.Inclined Aerator ( inclined apron with riffle plate aerator)
• In this aerator, water is allowed to fall in inclined plane with riffle plates.
• Riffle plates help to produce effervescence in water and hence there is
absorption of oxygen.
Inclined aerator

3. Salt Tray Aerator
• It consists a cylindrical encloser containing wooden trays kept one
above another with some vertical gap between them.
• Water falls through the trays absorbing oxygen.
• Water so aerated is taken away to the pure water reservoir from
the lower end.
salt tray aerator

4. Gravel Bed Aerator
• In this method gravel is packed in a container and water is passed from the
top.
• Air is blown from the bottom to the gravel packing thus water becomes
aerated and thus obtained water is collected from the bottom.
5. Spray Aerator
• In this aerator water flow is divided into fine streams and small droplets
which come into contact with air and aeration takes place.
• It can remove 70 to 90% of carbon dioxide.

6. Diffuse Aerator
• In this aerator, perforated pipe network is installed at the bottom of
aeration tank and compressed air is blown through these pipe networks.
• The air bubbles travel upward through water which causes aeration.
• Air diffuser tanks have a retention period of about 15 minutes and a
depth of 3 to 5 metres.(Length and breadth may be different.).
• Aerator pipes may be of different numbers depending upon length and
breadth.

Removal of Iron and Manganese
a) By Aeration
Iron
4Fe + O2 + 10 H2O ⟶ 4Fe(OH)3↓ + 8H
Ferrous Bicarbonate: Fe(HCO3)2
Fe(HCO3)2 + 2H2O ⟶ FeO + 2CO2 + 3H2O
4FeO + O2⟶ 2Fe2 O3
Fe2O3 + 3H2O ⟶ 2Fe (OH) 3↓
Manganese
6Mn + 3O2 + 6H2O⟶ 6MnO2↓ + 12 H

Domestic Purification Process
• Filter cylinders are used for domestic purification.
• Boiling is effective method for domestic ourification.
• Treatment with Iodine and Bromine can be done. These
chemicals should not exceed 8 ppm. Contact period is 5
minutes. These are easible in pills and are very handy.
• Potassium Permanganate :KMnO4 : In rural areas it is
common practice to dissolve a small amount of KMnO4 in a
bucket of water and mix it with the water of well frequently
to kill the bacteria.

UNIT 7 : DISTRIBUTION SYSTEM
Method of Distribution System
1. Gravity system
2. Pumping system
3. Dual system
Gravity System
• When the pure water reservoir is located at certain higher elevation
than the target community then the water can be supplied with
gravity flow.
• This is possible when the river is at further higher elevation than
the reservoir.
• This system has minimum leakage since water flow under gravity.
• Pipe size of distribution system is designed as to have the
remaining head equal to the head required for a tapstand.

Method of Distribution System
Pumping system
• In this system water has to be pumped and then directly sent to the
public.
• Size of pump depends on water demand or there may be numbers of
pumps and only some of them are operated at every time.
• Others are used for emergency cases like fire hazard etc. In case of areas
where electricity is not reliable, diesel pumps are used.
Dual system
• This method is also called combined gravity and pumping system.
• In this method of distribution, water is collected in the elevated water
reservoir and water is supplied from there.
• One pump to directly distribute to the community and other to elevate to
the reservoir can be installed and hence this system is called dual system
of distribution.
• This system is most reliable and economical. Even at the power failure, at
least the gravity flow is always there in the distribution line.

Reservoir
Types of reservoir
According to use
1. Clear water reservoir: It is used to store the filtered water or treated
water until it is pumped or conveyed into the service reservoirs for
distribution.
2. Service reservoir/ Distribution reservoir: It is used to store the
filtered water or treated water from clear water reservoir and
constructed before distribution system. It may be constructed of
masonry or RCC or ferrocement.
According to location or position
1. Surface/ground/non-elevated reservoir
2. Elevated reservoir

Reservoir
According to materials used
1. Earthen reservoir
2. RCC reservoir
3. Masonry reservoir
4. Steel reservoir
According to shape
1. Circular reservoir
2. Rectangular reservoir
3. Spherical reservoir
4. Elliptical reservoir

Layout of Distribution System
Dead end or tree system
In this system, one main pipeline through the centre of the
area to be served and from both sides of the main, the
submains takes off.
The submains are further divided into several branches from
which service connection are given to the consumers.
So, the network of pipelines covers the entire area as like a
tree and various dead ends are available.
This system is mostly adapted in towns or within cities
developed in haphazard way, e.g. Kathmandu valley.

Grid Iron System
• This system is called reticulated system and most convenient for
towns having rectangular layout or roads. Water circulates freely
throughout the system whole.

Circular or Ring system
• In this system each locality is divided into square or circular blocks
and the water mains are laid around the four sides of the square or
round the circle.
• The branches and submains are laid along the inner roads.
• All the mains, submains and branches are interconnected as in the
figure.

Radial system
• In this system water flows towards outer periphery from one
central point.
• Water lines are laid radially from the centre.
• This gives quick and satisfactory water supply.

Methods of water supply
Continuous system
• This is the best method and the water is supplied to the city during
all 24 hours of a day.
• It is possible when there is adequate quantity of water in the
source and the target community is small.
• In this system enough water is always available for meeting the
demand and due to the continuous water flow, water always
remains fresh.
Intermittent system
• If water is supplied to the consumers only during fixed hours of a
day from a system of supply, it is called intermittent system.
• It is the most common system and adopted in Nepal.
• The timing are fixed normally at the morning and evening.

Pressure in Distribution system
• Although the water is supplied to the public with greater pressure,
a lot of its head will be lost in the way of distribution.
• The head losses may occur due to friction in the pipeline, at the
reducers, valves, bends, meter etc.
• So the net head available at the consumer's tap is very important
since it is the head available that raises the water to upper floors.
• So considering these losses, the head at the supply point must be
maintained such that constant head is always available at the
consumer's tap.
• In the multistorey city the average pressure in the distribution
mains in different floor is listed below.
Up to 3 storey – 2.1 kg/cm2
3 to 6 storey - 2.1 to 4.1 kg/cm2
6 to 10 storey – 4.2 to 5.27 kg/cm2
Above 10 storey – up to 7 kg/cm2

UNIT 8: GRAVITY WATER SUPPLY SYSTEM
Concept of Gravity Water Supply
• Water source should be at a place having more elevation than that
of distribution reservoir.
• Distribution reservoir should be at higher elevation than that of
tapstands i.e. the community to serve.
• Small schemes and effectively used in rural areas.
• Flow by gravitational force only; no pumping.
• Collects water from springs or stream.
• In rocky area and crossing of rivers (above the river or at the bed of
river); GI pipes are used, otherwise HDP pipes are used.

Schematic Diagram of a Typical Gravity w/s system

Pipeline Design & Hydraulic Grade Line
• Standard tables are available for selection of pipes with different internal
diameters and different strength for a defined discharge.
• Hence we can select type of pipe (smaller or larger) from the table which
is the designed pipe or the pipe of fixed diameter and strength.
• In the table, percentage of headloss is available i.e. loss of head per 100
meter length of pipe.
• We will have different sections of pipeline with change in gradient from
survey.
• Loss of head for each pipeline section can be calculated from percentage
headloss for selected pipe from table.
• Difference in head between start and end of a pipe section can be
calculated adding headlosses at end of each section for downward slope
and deducting headloss for upward slope so to calculate the head
difference from intake to reservoir by calculation from survey data.

Water supply slides (1).pptx

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Water supply slides (1).pptx