technical) external & internal services (water...

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E4E4--E5 CIVIL E5 CIVIL

((TECHNICAL)TECHNICAL)

External & Internal Services External & Internal Services

(Water Supply)(Water Supply)

WELCOME

• This is a presentation for the E4-E5 Civil Technical

Module for the Topic: External & Internal Services –

Water Supply.

• Eligibility: Those who have got the Up-gradation to from

E4 to E5.

• This presentation is last updated on 21-4-2011.

• You can also visit the Digital library of BSNL to see this

topic.



AGENDA

Quality of Water

Demand requirements

Design of Water Distribution System

Internal Water Supply

QUALITY OF WATER

• Absolute pure water is never found in nature.

• Impurities in the form of salts, gases, bacteria algae

etc.

• Potable water to be supplied in the water supply

scheme.

• Potable water is safe to drink, pleasant to the taste.

• Contaminated water contains micro-organisms,

chemicals, industrial or other waters, or sewage.


STANDARDS OF WATER

Physical

• Temperature - 100 c to 15.60 c

• Colour - 10 to 20 (platinum cobalt scale)

• Turbidity - 5 to 10 ppm (Silica scale)

Chemical

• Total Solids - upto 500 p.p.m.

• Hardness - 75 p.p.m. to 115 p.p.m.

(hardness expressed as caco3 equivalent)


STANDARDS OF WATER

Chemical Contd.

• Chlorides - upto 250 p.p.m.

• Iron and Manganese - upto 0.3 p.p.m.

• ph Value - 6.5 to 8

• Sulphate - upto 250 p.p.m.

• Dissolved Oxygen - 5 to 6 p.p.m.

• B.O.D. - Nil


STANDARDS OF WATER

Biological

• B- coli - No B- coli in 100 ml.

• Most Probable Number - One Number in 100 ml.

(M.P.N)

• Periodical chemical, physical and bacteriological

tests of water samples shall be got it done through

approved laboratory.

• Remedial measures based on test results shall be

taken.


Treatment Process

Treatments used for removing impurities:

Impurity Process used for

removal

1. Floating matters as leaves, Screening

dead animals etc.

2. Suspended impurities Plain Sedimentation

as silt clay, Sand etc.

3. Fine suspended matter Sedimentation with

coagulation


Treatment Process

Impurity Process used for

removal

4. Micro-organism and Filtration

colloidal matters

5. Dissolved gases, tastes Aeration and

and odours chemical treatment

6. Softening Permutit method

7. Pathogenic bacteria Disinfections


Methods of Disinfection

The disinfection of water can be done by the following common

methods.

a) By the boiling of water.

b) By ultra-violet rays.

c) By the use of ozone.

d) By treatment with silver or electro-Katadyn process.

e) By the use of Iodine and Bromine.

f) By the use of excess lime.

g) By using potassium permanganate.

h) By the use of chlorine.


Methods of Disinfection

• Disinfection by excess lime though kills the bacteria but

pH value of the water is increased. Hence this method

is not use for water works.

• Use of KMNO4 can be used in open well or in ponds.

• The usual dose is 1-2 mg/litre with contact period of 4 to

6 hours. But efficiency to kill the bacteria is only 98%.

Hence not used in water works.

• The cheap and most effective method of disinfection is

by the use of chlorine.


Disinfection by Chlorine

• Chlorine is very useful to kill Micro-Organisms

present in the water. When Chlorine is dissolved in

water, it hydrolysis immediately as :

Cl2 + H2O ----- HOCL + H+ + Cl-

( Hyprocholorous Acid)

• Hypochlorous Acid further ionizes as

HOCL ----- H+ + OCL-

( Hyprocholorite Icons)


Disinfection by Chlorine

• Two prevailing species HOCL (Hypochlorous Acid)

and OCL- (Hypochloritic Ion) are called “Free

Available Chlorine” and are responsible for the

disinfection of water.


Forms of Chlorine

Chlorine is available in the following forms:

A. In the forms of Liquid Chlorine.

B. In the forms of gaseous Chlorine.

C. In the form of Chlorine dioxide.

D. In the form Chloramines.

E. In the form of

Bleaching Powder (Calcium Hypochloride).


Forms of Chlorine

• Form of Chlorine (A) to (D) in the previous slide,

require treatment plants and are used in big water

works.

• For small colonies we commonly use Bleaching

Powder as a source of Chlorine for disinfection and

it is cheap and best source of chlorine.


Dosage of Chlorine

• In normal waters that are pre treated with settling

and filtration, a chlorine of about 0.2 to 1 ppm

(Particle Per Million) may be required to obtain the

desired results.

• The bleaching powder normally contains chlorine

which vary 25-30%.

• Bleaching powder should be stored in air tight

container.


Demand Requirement

• The daily requirement of the buildings is calculated on the

basis of the population (p) and per capita rate of supply (q).

• For residential buildings, population may be taken as five

members per family.

• For residential buildings, per capita rate may be taken as

200 lit/head/day.

• For non-residential buildings, the daily consumption (q)

given table ‘B’.

• Population of buildings, (p) may be taken from table ‘A’.

• Total demand (Q) = p x q


Demand Requirement

Table A

• The assessment of the population in occupancies

based on plinth area clause 6.2.1. part IX Plumbing

services – section I. Water supply and clause 7,5 or

part IV fire protection as given in * National Building

code of India 1970 *

i) Staff Quarters & residence:- Assume a family of

5 person per quarter or an area of 12.5m2/person

whichever is more.


Demand Requirement and General Principles

Table A

ii) Technical buildings such as 10.00m2/person

• Telephone Exchange Buildings,

• Telecom Factories

• And workshop.

iii) Post offices and Administrative 10.00m2/person

• Buildings


Demand Requirement

Table B

i) Staff Quarters 200 Litres/ head/ day

(Para 5.1.N.B.C. 1983)

ii) Technical buildings: 45 litres/ head/ day

• Tel. Exch. Buildings ( Para 3.2 IS-1172-1971)

• Telecom factories

iii) Post offices and 45 litres/ head/ day

Administrative Buildings (Para 3.2 IS-1172/ 1971)


Layout of Distribution System

Dead End System

• Pipes are to be laid as per layout of the roads.

• This system requires less number of valves and also

shorter pipe lengths, therefore it is cheap and simple.

• But since water can be reached to any place by only one

route, any damage and subsequent repair to the pipe

result in shutting downs the supply of a large area

ahead.

• In this system water remains stagnant resulting

contamination of water.



Grid Iron System

• Where the roads arranged in grid iron pattern the

pipe lines are laid similarly.

• Water reaches different places through more than

one route. Hence frictional losses are less, and the

sizes of the pipe get reduced.

• However the system requires more length of pipes

and number of sluice valves.



Grid Iron System Contd…

• If repairs are to be carried out to any pipe, only a

small portion in the vicinity gets effected, since

water can be supplied ahead by some other route.

• There is no stagnation of water. Hence no problem

of contamination.



The Ring Main System

• The capacity of grid iron can be enhanced and the

pressures can be improved by running a looped

feeder around the high demand section and

arranging grid over it.



• Till date no direct methods are available for design

of distribution pipes.

• While doing the design, diameter of pipes are

assumed. Terminal pressure are calculated, after

allowing the losses of head, when full peak flow

discharge is flowing.



The Hazen – william’s formula is widely used for

determining the velocity through pipes.

V = 0.85 CH.R0.63 S0.54

V = Velocity m/Sec.

S = Slope of the Energy Line.

R = Hydraulic Mean Depth

R = A/P = Cross section area/

Perimeter

CH = Coefficient of Hydraulic Capacity.


Design of Pipe Network

• To reduce the tedious calculations of calculating the

Head Losses in pipes, the Hazen – William’s

Nomogram is used. Hazen – William’s chart for

various materials of pipe are available in Public

Health Engineering departments of the state Govt.


Hazen-William’s Nomogram



General Guidelines for Planning of Internal Water

Supply System:-

• Water for drinking purpose should not be taken from

Distribution Pipe (from OHT) but it should be taken

directly from Service Pipe (to OHT) or separate pipe

should be provided to kitchen.

• Distribution pipe should be designed to avoid any

Air Lock. Vent should be provided at the highest

point.



General Guidelines for Planning of Internal Water

Supply System Contd…:-

• It is always preferable to provide unions at number

of places so as to enable for easiness in repairs.

• No reveres loop should be provided in the internal

water supply otherwise water supply will be blocked

by Air Lock.


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