ch 1 quantity of water m.m.ppt 2008

8/18/2019 Ch 1 Quantity of Water M.m.ppt 2008

1/63

&

HAPTER ONE

WATER SUPPLY

TREATMENT

DBU, Institute of

College of

Department of Civil

Abra


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DBU Cha ter one Quantit

Sources of water supply

The water cycle

Types of water sources

Water quality considerations

Source siting and selection

Reservoirs

Catchment areas and reservoir sites

Volume of reservoirs

Impounded reservoirs

Catchment protection

ourse ontent ont……

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GroundwaterGroundwater flow

Hydraulics of water wells

Well construction and maintenance

Collection and distribution of water

Surface water intakes

Water conveyance systems

Pipes and appurtenances

Distribution systems


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Layout of distribution systemsDistribution reservoirs

Design of distribution systems

Construction and maintenance of distribution systems

Pumps and pumping stations

Purpose and types of pumps

Centrifugal pumps

Pump terms

Selection of pumps


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6

Troubles and maintenancePumping stations

Waste water and storm water collection system

General introduction

Sources and quantities of wastewater

Fluctuations in sewage flow

Sewerage system

Sewer materials and appurtenancesDesign of sanitary sewer systems


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Design of storm sewersSewerage system construction and maintenance

Water Treatment

Coagulation and Flocculation

Filtration

Disinfection

Softening


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References

Textbook: Elements of water supply Engineering by Tesfaye Nigussie

M.Hammar, Water and Wastewater Technology

E.W.Steel, Water Supply and Sewerage

A.C. Panchdhari, Water Supply and Sanitary Installation

Evaluation Mechanism

Assignments(Group and Individual),Quiz(s),

Attendance(participation) and Project…..…………………......................................................

Mid exam……………………………………………………………………………………

Final exam…………………………………………………………………………………

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Chapter One:

QUANTITY OF WATER


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Body composition Body, 65% water; blood, 83%; bones, 25%

Basic requirements for safe water

Drinking: 2–3 liters/day

Minimum acceptable standard for living (WHO) 20–50 liters/capita/day for cooking and basic hygiene

Introduction


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The estimated water supply coverage for Ethiopia is 41.2% forand 78.8 % for urban and the country’s water supply cove

47.3%.

Access to water-supply services is defined as the availability

least 20 liters per person per day from an improved source w1 kilometer of the user's dwelling.

Introduction


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“improved” source is one that is likely to provide "safe" water, sas a household connection, a borehole, etc.

An improved water supply is defined as:

Household connection

Public standpipe Borehole

Protected dug well

Protected spring

Rainwater collection

“improved” source


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deals with Planning, design, construction, operation and

maintenance of water supply systems.

Planning should be economical, socially acceptable, and

environmentally friendly that meet the present as well as futu

requirement.

Water Supply Engineering


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Safe and wholesome(healthy) water

Adequate quantity

Readily available to encourage person

and household hygiene

Water Supply System Objectives


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Water supply system planning involves

identification of service needs

evaluation of options

determination of optimal strategy to meet services

development of implementation strategies

The planning exercise involves

collection of pertinent data(Geological data, Hydrological data, Sanitary condithe area, topography of the area, Legal requirements, public openion,Level of water

existing water supply system)

consideration of relevant factors, and

preparation of project documents and cost estimates

Water Supply System Planning


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Population.

Factors affecting the future increase in the population are to be studied.

Per capita Requirement . the various factors and living standard and the numbertype of industries, number and type of the commercial establishments in the town etc.

Public places, parks, institutions etc . Water is required for the developmenparks, fire fighting and so many other purposes at public places.

Industries. existing industries as well as future industries should be thoroughly determined.

Sources of water. Detailed survey of the various sources of water available in the

vicinity of the area should be made.

Conveyance of water. from source to water treatment units depend on the relativof the two points. It may flow directly by gravity, if source is at higher elevation. In case pumrequired, then the capacity of the pumps should be determined.

Factors to be considered

(during preparation of the water supp ly design project)


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Quality of water. The analysis of the raw water quality should be made to know the vaimpurities present in it, and to decide on the required treatment processes.

Treatment works. The various sizes and number of treatment units in the water workson the quality and quantity of raw water and the limiting water quality standards.

Pumping units for treated water . The pump-house is designed by considering the

population water demand. The required number of pumps is installed in the pump house fopresent water pumping requirement, with provision of 50% stand-by pumps for emergency.

Storage. The entire city or town should be divided into several pressure zones and storagshould be provided in each zone.

Distribution system . The distribution system should be designed according to the masof the town, keeping in mind the future development.

Economy and reliability. should be economical and reliable. It should draw sufficient of water from the source at cheapest cost and the purification should meet desired limits.

Factors to be considered


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Population Forecasting


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Every country conducts an official enumeration of the populationcalled census every ten-years time (decennial census).In Ethiopia,

the available census data are collected from the Central Statistical

Authority (CSA). The data is then used for the projection of the

future population of the area under consideration at the end of th

design period.

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21

Following are factors responsible for changes in population: Birth rate

Death rate

Migration rate

There are various methods of projecting population. The methods utilize

different assumption and give different results Selection of method depen

amount of data available, past population history and length of design per


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Arithmetic method:

the rate of population growth is constant. Mathematically the hypothesis may be expressed a

k is determined graphically of from successive population figures.

And the future population is given by


k dt

dP

t K P P ot * Where Pt = Future Population after t years

Po = Present Population (Base Population)

K = Arithmetic Growth constant

t= Period of Projection 12

12

t t

P P

dt

dP K


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Geometric or uniform percentage method:

rate of increase which is proportional to the population.

Integrating yields

Where Pt = Future Population after t years

Po = Present Population (Base Population)

K = Geometric Growth constant

t= Period of Projection


kP dt

dP

t K P P ot *lnln

12

12 lnln

,*t t

P P K P K

dt

dP


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Simple Graphical Method

In this method, a graph is plotted from the available data, between time and population. The

is then smoothly extended up to the desired year.

Comparative Graphical Method

In this method, the cities having conditions and characteristics similar to the city whose futur

population is to be estimated are selected. It is then assumed that the city under consider

will develop, as the selected similar cities have developed in the past.

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Decreasing Rate of Increasing

Population is assumed to reach some limiting value or saturation point

Following formula is used to estimate the population

Where: Z = Saturation Population and is calculated as:

P1, P2 and P3 = Population at times t1, t2 and t3 respectively.

K = Rate and calculated as:

26

P Z K dt

dP *

21*22t t K

t e P Z P P

2

12

2

2

1212

P P P

p P P P P P Z

o

oo

1

2

12

ln1

P Z

P Z

t t

K


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Logistic Curve Fitting Method

Population growth follows a logistic or mathematical relationship .the most common relationsh

S-Curve.

Following formula is used to estimate the population

Where: Z = Saturation Population and calculated as above

a, b = Constants and are calculated as follow

and

n = Constant interval b/n years

27

ot t bt

ae

Z P

1

o

o

P

P Z a

o

o

P Z P

P Z P

nb

1

1ln

1


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Arithmetic Increase

Increase in present and first decade 50000 – 47100 = 2900

Increase in first and second decade

47100 - 43500= 3600

Increase in second and third decade

43500 – 41000 = 2500

Average increase = (2900+3600+2500)/3 = 3000

Population after 1st decade = 50000 + 3000 = 53000

Population after 2nd decade = 50000 + 6000 = 56000

Population after 3rd decade = 50000 + 9000 = 59000

Solution


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Geometric Increase

Percent increase in present and first decade (2900/ 47100)*100 = 6.16 %

Percent increase in first and second decade

(3600/ 43500 )*100 = 8.26 %

Percent increase in second and third decade

(2500/ 41000)*100 = 6.09 %

Average increase = (6.16 + 8.26 + 6.09)/3 = 6.84 %

P after 1st decade = 50000 (1 + 6.84/100)1 = 50342

P after 2nd decade = 50000 (1 + 6.84/100)2 = 53786

P after 3rd decade = 50000 (1 + 6.84/100)3 = 57465

Solution


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The Annual Growth Rate of a town in Ethiopia is 3.5%. Assumithe present population of the town (in 2015) is 4500, what wou

be the population in 2030?

Solution:

AGR = 3.5 ; P

o

= 4500

n = 2030-2015 = 15

P

n

= P

o

(1+AGR/100)

n

P

15

= 4500(1+3.5/100)

15

=7540

Example 1.2.


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The following data shows the variation in population of a

from 1944 to 2004. Estimate the population of the city in the

2014 and 2019 by arithmetic and geometric increase methoarithmetic increase method by your own.)

Example 1.3.

Year 1944 1954 1964 1974 1984 1994

Population 40185 44522 60395 75614 98886 124230 1


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Solution 1.3.

Year 1944 1954 1964 1974 1984 1994 2

Population 40185 44522 60395 75614 98886 124230 15

Change 4337 15873 15219 23272 25344 34

% Change 10.79 35.65 25.20 30.78 25.63 27

Average change = (4337+15873+15219+23272+25344+34570)/6 =19770 per decade

Average change = (10.79+35.65+25.20=30.78+25.63+27.83)/6 = 25.98 per decade

Using Arithmetic Method

P

2014

= P

04

+ 1 x 19770 = 158800 + 19770 = 178570

P

2019

= P

04

+ 1.5 x 19770 = 158800 + 1.5 x 19770 =188455

Using Geometric Method

P

2014

= P

04

(1 + i/100)

1

= 158800 (1 + 25.98/100)=200057

P

2019

= P

04

(1+ i/100)

1.5

=158800 (1 + 25.98/100)

1.5

=224545


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Estimate the population at 2000 using the following census resu

Exercise

34

Year Population

1970 10,000

1980 15,000

1990 18,000


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It is information regarding the physical distribution of the

population.

It is important to know in order to estimate the flows and to de

the distribution network.

Population density varies widely within a city, depending on theland use.

May be estimated from zoning master plan.

Population Density


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Water demand is defined as the volume of water required by us

to satisfy their needs.

Demand is the theoretical while consumption is actual.

Design of a water supply scheme requires knowledge of water

demand and its timely variations.

Various components of a water demand are

residential, commercial, industrial, public water uses, fire deman

and unaccounted for system losses.

Components of Water Demands


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Water Demand

Components

Domestics Non domestic

Commercial

Industrial

Institutional

Agricultural

Public uses

Losses and

leakage Fire


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This includes the water required in residential buildings

drinking,cooking, bathing, lawn sprinkling, gardening, san

purposes, etc.

The amount of domestic water consumption per person v

according to the living standards of the consumers.

In most countries the residential demand constitutes 50 to 60

the total demand.

Residential (Domestic)Water Demand


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Commercial water demand: as hotels, shopping centres, sstations, movie houses, airports, etc.

The commercial water demand may vary greatly depending o

type and number of establishments.

Industrial water demand: tanning, brewery, dairy, etc. The quantity of water required for commercial and ind

purposes can be related to such factors as numb

employees, floor area of the establishment, or units produced

Commercial and Industrial Water Demand


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The quantity of water required for public utility purposes

Includes water for public institutions like schools, watering of

public parks, washing and sprinkling of roads, use of public

fountains, clearing wastewater conveyance, etc.

Usually the demand may range from 2-5 of the total demand.

Public Water Use


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Typical Public Water Demands

Category

Typical rate of water use

per day

Day schools 5 l/pupil

Boarding schools 50 l/pupil

Hospitals 100 l/bed

Hostels 80 l/bed

Mosques 5 l/visitor

Cinema houses 5 l/visitor

Offices 5 l/person

Public baths 100 l/visitor

Hotels 100 l/bed

Restaurant/Bar 10 l/seat

Camp 60 l/person

Prison 30 l/person


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This is the quantity of water required for extinguishing fires an

always stored in storage reservoirs.

This demand is, therefore, taken care of by increasing the volum

the storage tanks by 10 .

Quantity of water required for fire fighting can be calculated baon the following formula.

Fire Fighting Water Demand

43


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National Board of Fire Underwriters (NBFU) (For communitie

than 200, 000)

Fire Fighting Demand

)01.01(6.231 P P Q F

Where, Q F = is fire demand (m3/hr); P = Population in 1000’s.


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reeman’s ormula

Where: Qf = Fire flow rate in m3/hr

P = Population in thousands

45

105

*57 P

Q f

Kuichling’s Formula

Where: Qf = Fire flow rate in m3/hr

P = Population in thousands

P Q f 159


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All the above formula are literature recommendations based on

standard of the concerned country and they are not recommendto be applied for Ethiopian case.

This demand is generally taken care of by increasing the volumthe storage tanks by 10 .

Considered to be met by stopping supply to consumers anddirecting it for fire fighting purpose.

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This includes water losses in the water supply system due to ba

plumbing, illegal connections and others.

The amount is usually expressed in percentage of the sum of

domestic demand, public demand and the industrial demand

covered from the water supply system. And it usually varies fro

15 to 50 depending on the age of the pipelines in the systemand the size of the distribution network.

Unaccounted system losses and leak

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For a town having population of 60,000 estimate average

demand of water. Assume industrial use 10%, institutiona

commercial use 15 %, public use 5% and live stock 10% of dom

demand. Take per capita domestic consumption of 50 l/day

leakage to be 5%.

Example 1.4


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P = 60,000

Domestic = 50 x 60,000 = 3000000 l/day= 3000 m3/day

Industrial = 0.10 x 3000 m3/day = 300 m3/day,

Inst & com. = 0.15 x 3000 m3/day = 450 m3/day

public = 0.05 x 3000 m3

/day = 150 m3

/day live stock = 0.10 x 3000 m3/day = 300 m3/day

leakage = 0.05 x 3000 m3/day = 150 m3/day

Total average daily demand = 4350 m3/day

Solution 1.4


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Climatic conditions:Rate of water consumption increases with the increase in temperature-

consumption in summer is higher than in winter.

Cost of water:The existence of meters and high costs of water limits the water consumption.

Living Standards: Rate of water consumption increase with higher standard of living.

Industries:

Metering water lines

Quality of water supply: water is consumed when quality of water is better.

Size of city: The bigger size of community makes an in-increase in industrial and municipal demands which

Increase rate of water consumption.

Factor Affecting Water Use


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Water Use Variation

0

500

1000

1500

2000

2500

3000

3500

4000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Sunny day

Rainy day


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Annual average day demand (Qday-avg

) the average daily demand over

period of one year. For economical calculations and fire fighting.

Maximum day demand (Qday-max

) the amount of water required durin

the day of maximum consumption in a year. Important for water

treatment plants and water storages.

Peak hour demand (Q

hr-max

) the amount of water required during themaximum hour in a given day. Important for design of distribution

systems.

Coincident draft (Qcd

). the sum of maximum daily demand, Qday-max, a

the fire demand (QF).

Variations in water demand


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Typical Peak Factors

PopulationMaximum Day

FactorPeak Hour Fa

0 to 20,000 1.30 2.00

20,001 to 50,000 1.25 1.90

50,001 and above 1.20 1.70


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Water Supply Components

Source

LLP

Treatment

Plant

HLP

Storage

Distribution system

Pipe I Pipe II

Pipe I

Water Supply System Components


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Component

Special

characteristics

Design period

Design capacity

Source:

Groundwater

Surface sources

Easy to expand

Uneasy to expand

5-10

20-50

Qday-max

Pipe mains (Type I

and Type II)

Long life

Cost of materialis only a small

portion of the

cost of

construction

>25

Qday-max

Suitable velocities uall anticipated flow

conditions

Treatment plant Expansion is

simple 10-15Qday-max or 1.6Qday-avg wh

is greater

Water Supply System Components


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Component

Special

characteristics

Design

period

Design capacity

Pumping units Easy to modify

and expand10

LLP: 2Qday-avg or 4/

whichever is greater

HLP: 3Qday-avg or 4/

whichever is greater

Service reservoir

Long life Easy to construct

Relatively

inexpensive

Very long

Design should consider:

Hourly fluctuations of fl

The emergency reserve

The provision require

pumps satisfy the ent

demand in less than 24

The fire demand.

Type III pipe anddistribution pipes

Long life

Replacement is

very expensive

IndefiniteQhr-max or Qday-max+QF , whichgreater (calculated for antici

maximum growth)


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The pumping station is called “low-lift” or “low-service” because

function of the pumps is to raise the water from the surface wa

supply to the treatment facility. “High-service” pumps that supp

water to the distribution system are selected with the objective

providing a high enough pressure to make water flow at a high

through service connections at various elevations throughout thdistribution system.

58

Design Period


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Water supply system is generally designed to serve the needs of future population

Design Year: year when the facility is expected to reach its full design capacity and th year at which future expansion may become necessary.

Selecting design period needs sound judgment and skills in developing future populagrowth estimate from the past social and economic trends

Different factors considered to decide a design period for a water supply project

1.

useful time of different units2. convenience of future expansion

3. anticipated changes in drinking water quality requirements

4. anticipated changes in raw water quality

5. growth pattern of the community, service area and region

6. trends in interest rate

7. present and future construction costs

8. availability of funds

59

Example 1.5


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Calculate the water requirements for a community that will rea

population of 120,000 at the design year. The estimated mun

water demand for the community is 300 l/c/d. Calculate the

flow, design capacity of the water treatment plant, and d

capacity of the water distribution system. Use NBFU formula for

flow.

Solution 1.5


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P = 120,000

Qday-avg = 300 x 120,000 =36000000 L/d = 36000 m3/d

Take PF for Q day-max = 1.6 and 2.0 for Qpeak-hr

Q day-max =1.2 x 36000= 57,600 m3

Qpeak-hr= 1.7 x 36000 = 72,000 m3

Fire flow rate = )01.01(6.231 P P Q F

13.2259)12001.01(1206.231 F Q m3/hr = 54219 m3

Design capacity of treatment plant = 57,600 m3/day

Distribution system Design capacity = max(72,000 or 57600 + 54219) = 111819

END of


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END of Chapter 1

END of

chapter

1:Quantity

of Water

By:Abraham


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END of Chapter 1

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chapter 1y:Abraham

ch 1 quantity of water m.m.ppt 2008

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