water supply systems lecture 2

8/10/2019 Water Supply Systems Lecture 2

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Water Supply Systems

Lecture notes 2

dr Patryk Wjtowicz

Monday 1 December 14


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Contents

Design considerations - key parameters Water demand calculations:

estimation of base water demand

water demand forecasting

peaking factors

leakage and unaccounted-for water water for fire protection



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Design considerations

The design considerations of water supply systems involve topographicfeatures of terrain and economical parameters (restrictions)

Some essential parameters for network sizing are: the projection of residential, commercial and industrial water

demand per capita water consumption

peak flow factors

minimum and maximum pipe sizes pipe material

system safety and reliability requirements

selection of optimal design periodof a water distribution system

in a pre-decided time horizon



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Water demand

The estimation of water demand for the sizing of any watersupply system or its components is the most important part ofthe design methodology

Water demands (water duties) are generated from:

residential industrial and commercial developments community facilities and services

firefighting demand account for system losses (unaccounted-for water or UFW) periodical flushing

treatment facility water demand

Customerdemand



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Water demand

Water demandis not constant, and is affected by a number of factors:

climate economic and social factors

water pricing, completeness of meterage, system management

land use resort to private supplies population and type of a city

standard of living, extent of sewage system industrialization of the area (size and type)...

A comprehensive study should estimate water demand considering all thesite-specific factors

Variations of water demand are observed in different time horizons (i.e. year,month, day, hour)



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Historical water consumption in Poland

1965-2005



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Historical water consumption in households in

Poland 1953-2005



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Monthly water consumption variations

(for a selected Polish city)



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Example of average daily water consumption

variations throughout a year




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Diurnal water variation in water demand




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Single FamilyBusinesses

RestaurantFactory

Deman

dMu

ltiplier

Deman

dMu

ltiplier

Deman

dMu

ltiplier

Deman

dMu

ltiplier

Time Time

Time Time



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Water demand forecasting

Forecasting is made for different time horizons: current (actual) water demand - prepared for

existing water networks, based on trends in

historical data average-term forecast

long-term forecast

Average- and long-term forecasts are mainly basedon unit water demands (index method)

Time, year

PeakDayDemand,

MGD

Annual Demand Data

204020302020201020001990198019701960

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Constant Percent Growth

Growth to Buildout

Economic Downturn

Linear Growth

Different methods for projecting future demands



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Population projection formulas

Arithmetic (recommended for cities up to 20 000):P

f= P

c1+

i + t

100

!"#

$%&

Geometric (recommended for cities up to 20 000):P

f= P

c1+

i

100

!"#

$%&

t

Exponential (recommeded for cities from 20 000):

Pf= P

c+ e

i+t

100

!"#

$%&

Pf - future population

Pc- current population

i - growth rate in %

t - time in years



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Water demand forecasting

To capture variability of water demand there are severalcharacteristic parameters describing water consumption

and usage

Average day water demandQavdexpressed in m3/d:

Maximum day water demandQmaxd(m3/d)

Qavd =Qyear

365, m 3 /d

Qmaxd

= Qavd

! Nd

where: Nd- daily peaking factorMonday 1 December 14


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Daily and hourly peaking factors(Polish regulations)



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Calculation of water demand (cont.)

Peak hour water demandQmaxh(typically expressed in dm3/s or m3/h):Q

maxh = N

h!

Qmaxd

24

where: Nh- hourly peaking factor



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Water demand

The residential forecast of future demandis usually based on house count, census records andpopulation projections

The industrial and commercial facilitieshave a wide range of water demand

This demand can be estimated based on historicaldata from the same or comparable other system

Planning guidelines provided by engineeringbodies, governmental and regulatory agencies

should also be considered



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Water demand

The firefighting demandcan be estimated using equations(Kuichling or Freeman formula) or according to local guidelinesor design codes in national firefighting regulations

Estimation of water lossesis not straightforward anddepends on a number of factors:

age of system minimum prescribed pressure

maximum pressure in the system pipeline material quality of pipeline materials and maintenance works

specific local conditions (mine damages, earthquakes) ...Monday 1 December 14


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Calculation of residential water demand(Polish regulations)



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Typical water duties in USA

T LE 3 3 T ical Rates of Water Use for Various Establishments

T LE 3 2 Typical Water Duties

Land

Use

Low-density residential

Medium-densityresidential

High-density residential

Single-family residential

Multifamily residential

Office commercial

Retail commercial

Light industrial

Heavy industrial

Parks

Schools

Water

Duty,

gal/day/acre)

Low

High verage

400

3300

1670

900 3800 2610

2300

12000

4160

1300 2900 2300

2600 6600 4160

1100

5100

2030

1100 5100 2040

200

4700

1620

200 4800 2270

400

3100 2020

400

2500

1700

Source

Adapted fromMontgomery Watson study of data of 28 western U.S.

cities.

ote

gal X 3.7854 = L.


T i l t f t f if f


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Range of Flow

User (l/person or unit/day) (gal/person or unit/day)

Airport, per passenger 1020 35

Assembly hall, per seat 610 23

Bowling alley, per alley 60100 1626

Camp

Pioneer type 80120 2132

Childrens, central toilet and bath 160200 4253

Day, no meals 4070 1118

Luxury, private bath 300400 79106

Labor 140200 3753

Trailer with private toilet and bath,

per unit (2 1/2 persons)

500600 132159

Country clubs

Resident type 300600 79159

Transient type serving meals 60100 1626

Dwelling unit, residential

Apartment house on individual well 300400 79106

Apartment house on public water supply,unmetered

300500 79132

Boardinghouse 150220 4058

Hotel 200400 53106

Lodging house and tourist home 120200 3253

Motel 400600 106159

Private dwelling on individual well or

metered supply

200600 53159

Private dwelling on public water

supply, unmetered

400800 106211

Factory, sanitary wastes, per shift 40100 1126

Table extracted from Ysuni, 2000 based on Metcalf and Eddy, 1979

Typical rates of water use for variousestablishments (USA)

Typical rates of water use for various

establishments in USA



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Fairground (based on daily attendance) 26 12

Institution

Average type 400600 106159

Hospital 7001200 185317

Office 4060 1116

Picnic park, with flush toilets 2040 511

Restaurant (including toilet)

Average 2540 711

Kitchen wastes only 1020 35

Short order 1020 35

Short order, paper service 48 12

Bar and cocktail lounge 812 23

Average type, per seat 120180 3248

Average type, 24 h, per seat 160220 4258

Tavern, per seat 60100 1626

Service area, per counter seat (toll road) 10001600 264423

Service area, per table seat (toll road) 600800 159211

School

Day, with cafeteria or lunchroom 4060 1116

Day, with cafeteria and showers 6080 1621

Boarding 200400 53106

Self-service laundry, per machine 10003000 264793

Store

First 7.5 m (25 ft) of frontage 16002000 423528

Each additional 7.5 m of frontage 14001600 370423

Swimming pool and beach, toilet and shower 4060 1116

Theater

Indoor, per seat, two showings per day 1020 35

Outdoor, including food stand, per car

(3 1/3 persons)

1020 35

Range of Flow

User (l/person or unit/day) (gal/person or unit/day)

Table extracted from Ysuni, 2000 based on Metcalf and Eddy, 1979

Typical rates of water use for various establishments

in USA (cont.)



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Unit (average) water demand for industrial facilities

according to the population (Poland)


Average rates of nonresidential water use from


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Category SIC Code Use Rate(gal/employee/day)

SampleSize

Construction 31 246

General building contractors 15 118 66

Heavy construction 16 20 30

Special trade contractors 17 25 150

Manufacturing 164 2790

Food and kindred products 20 469 252

Textile mill products 22 784 20

Apparel and other textile products 23 26 91

Lumber and wood products 24 49 62

Furniture and fixtures 25 36 83

Paper and allied products 26 2614 93

Printing and publishing 27 37 174

Chemicals and allied products 28 267 211

Petroleum and coal products 29 1045 23

Rubber and miscellaneous plastics products 30 119 116

Leather and leather products 31 148 10

Stone, clay, and glass products 32 202 83

Primary metal industries 33 178 80

Fabricated metal products 34 194 395

Industrial machinery and equipment 35 68 304

Electronic and other electrical equipment 36 95 409

Transportation equipment 37 84 182

Instruments and related products 38 66 147

Miscellaneous manufacturing industries 39 36 55

Transportation and public utilities 50 226

Railroad transportation 40 68 3

Local and interurban passenger transit 41 26 32

Trucking and warehousing 42 85 100

U.S. Postal Service 43 5 1

Water transportation 44 353 10

Transportation by air 45 171 17

Transportation services 47 40 13

Communications 48 55 31

Electric, gas, and sanitary services 49 51 19

Wholesale trade 53 751

Wholesale tradedurable goods 50 46 518Wholesale tradenondurable goods 51 87 233

Table from Dziegielweski, Opitz, and Maidment, 1996


establishment-level data in USA (according to SIC

code)

(SIC) Standard Industrial Classification



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Retail trade 93 1044Building materials and garden supplies 52 35 56

General merchandise stores 53 45 50

Food stores 54 100 90

Automotive dealers and service stations 55 49 498

Apparel and accessory stores 56 68 48

Furniture and home furnishings stores 57 42 100

Eating and drinking places 58 156 341

Miscellaneous retail 59 132 161

Finance, insurance, and real estate 192 238

Depository institutions 60 62 77

Nondepository institutions 61 361 36

Security and commodity brokers 62 1240 2

Insurance carriers 63 136 9

Insurance agents, brokers, and service 64 89 24

Real estate 65 609 84

Holding and other investment offices 67 290 5

Services 137 1878

Hotels and other lodging places 70 230 197

Personal services 72 462 300

Business services 73 73 243

Auto repair, services, and parking 75 217 108

Miscellaneous repair services 76 69 42

Motion pictures 78 110 40

Amusement and recreation services 79 429 105

Health services 80 91 353

Legal services 81 821 15

Educational services 82 110 300

Social service 83 106 55

Museums, botanical, zoological gardens 84 208 9

Membership organizations 86 212 45

Engineering and management services 87 58 5

Services, NEC 89 73 60

Public administration 106 25

Executive, legislative, and general 91 155 2

Justice, public order, and safety 92 18 4

Administration of human resources 94 87 6

Category SIC CodeUse Rate

(gal/employee/day)

Sample

Size

Environmental quality and housing 95 101 6

Administration of economic programs 96 274 5

National security and international affairs 97 445 2

Table from Dziegielweski, Opitz, and Maidment, 1996


establishment-level data (cont.)


A d d f l d i l f ili i


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Average water demand for selected commercial facilities

(Poland)



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Unaccounted-For Water (UFW)

Ideally, if individual meter readings are taken for every customer,

they should exactly equal the amount of water that is measured

leaving the treatment facility

In practice not all of the outflows are metered. These lostflowsare referred to as unaccounted-for water (UFW)

The most common reasons for discrepancies are: leakage

overflows at tanks

errors in flow measurement (under-register at low flow rates) unmetered water usage (illegal connections, usage of fire

hydrants, blow-offs and other maintenance appurtenances)



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Leakage

Leakage is commonly the largest component of UFW and includes:

distribution losses from supply pipes distribution and trunk mains services up to the meter

connections to tanks

The amount of leakage varies from system to system, but there is a generalcorrelation between the age of a system and the amount of UFW. Projections ofleakage must include special areas (mine damages, earthquakes etc.)

New and well maintained systems may have as little as 5% leakage, while oldersystems may have 40% leakage or even higher

Other factors affecting leakage include: system pressure (the higher the pressure, the more leakage) burst frequencies of mains and service pipes

leakage detection and control policiesMonday 1 December 14


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Estimating water leakage

For existing networks made of traditional materials(cast iron) properly maintained leakage index may beestimated from 0.5 m3/h km to 0.3 m3/h km

For new networks (after renovation), properly built

and maintained leakage index should not be higher

than 0.3 - 0.2 m3/h km

For water demand forecasting leakage should be

between 5% to 10% of average daily water demand



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Estimating water leakage


Leak Losses for Circular Holes Under Different Pressures*


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Leak Losses for Circular Holes Under Different Pressures*

Diameter

of Hole,

in.

Area of

Hole,

in.2

Leak Losses, gpm

Water Pressure, psi

20 40 60 80 100 120 140 160 180 200

0.1 0.007 1.067 1.510 1.850 2.136 2.388 2.616 2.825 3.021 3.204 3.337

0.2 0.031 4.271 6.041 7.399 8.544 9.522 10.464 11.302 12.083 12.816 13.509

0.3 0.070 9.611 13.593 16.648 19.224 21.493 23.544 25.430 27.186 28.835 30.395

0.4 0.125 17.087 24.165 29.597 34.175 38.209 41.856 45.209 48.331 51.263 54.036

0.5 0.196 26.699 37.758 46.245 53.399 59.702 65.400 70.640 75.518 80.098 84.431

0.6 0.282 38.477 54.372 66.593 76.894 85.971 94.176 101.721 108.745 115.341 121.5810.7 0.384 52.331 74.007 90.640 104.662 117.010 128.184 138.454 148.014 156.993 165.485

0.8 0.502 68.350 96.662 118.387 136.701 152.840 167.424 180.839 193.325 205.052 216.144

0.9 0.636 86.506 122.338 149.833 173.012 193.434 211.896 228.874 244.676 259.519 273.557

1.0 0.785 106.798 151.035 184.979 213.596 238.807 261.600 282.561 302.070 320.394 337.725

1.1 0.950 129.225 182.752 223.825 258.451 288.957 316.536 341.898 365.505 387.676 408.647

1.2 1.131 153.789 217.490 266.370 307.578 343.882 376.704 406.887 434.981 461.367 486.323

1.3 1.327 180.488 255.249 312.615 360.977 403.584 442.104 477.527 510.498 541.465 570.755

1.4 1.539 209.324 296.028 362.559 418.648 468.062 512.737 553.819 592.057 627.972 661.941

1.5 1.767 240.295 339.829 416.203 480.590 537.317 588.601 635.762 679.658 720.886 759.880

1.6 2.011 273.402 386.649 473.547 546.805 611.347 669.697 723.355 773.299 820.208 864.575

1.7 2.270 308.646 436.491 534.590 617.292 690.153 756.025 816.600 872.983 925.938 976.024

1.8 2.545 346.025 489.353 599.333 692.050 773.736 847.585 915.496 978.707 1,038.070 1,094.220

1.9 2.836 385.540 545.237 667.776 771.081 862.095 944.378 1,020.040 1,090.470 1,156.620 1,219.180

2.0 3.142 427.191 604.140 739.918 854.383 955.230 1,046.400 1,130.240 1,208.280 1,281.570 1,350.890

* Calculated using Greeleys formula (see equation on following page).

Leak Losses for Joints and Cracks*

Area of Joint

or Crack Leak Losses, gpm

Length, Width, Water Pressure, psiin. in. 20 40 60 80 100 120 140 160 180 200

1.0 132 3.2 4.5 5.5 6.4 7.1 7.8 8.4 9.0 9.6 10.1

1.0 116 6.4 9.0 11.0 12.7 14.2 15.6 16.9 18.0 19.1 20.1

1.0 18 12.7 18.0 22.1 25.5 28.5 31.2 33.7 36.0 38.2 40.3

1.0 14 25.5 36.0 44.1 51.0 57.0 62.4 67.4 72.1 76.5 80.6

* For leaks emitted from joints and cracked service pipes, an orice coefcient of 0.60 is used

in the following equation:

Q= (22.796)(A)( P )

Where: Q=ow, in gpm;A= area, in in.2; P= pressure, in psi

43,767

,Q A P1 440 # #

Where:

! = ow, in gpm

" = the cross-sectional area of the leak, in in.2

# = pressure, in psi

Greeleys formula (used for leakages from pipes orbroken taps, assuming an orifice coefficient of 0.80)



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Fire protection

Fire storageis the amount of stored water requiredto provide a specified fire flow for a specified duration

The rate of flow to be provided for fire flow is typicallydependent on the land use and varies by community

The fire flow criteria are usually given in national orlocal regulations (e.g. fire marshall)


Fi i d d


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Fire protection water demands(USA and Poland)

Table 4.5 Needed fire flow for residences two stories and less

Distance Between Buildings

(ft)

Fire Flow

(gpm)

More than 100 500

31-100 750

11-30 1,000

Less than 11 1,500

T LE

3 4

TypicalFire

Flow

Requirements

Land

Use

Single-family residential

Multifamilyresidential

Commercial

Industrial

Central business district

Note:

gal X

3.7854

= L.

Fire

Flow

Requirements, gal/m

500-2000

1500-3000

2500-5000

3500-10,000

2500-15,000

Typical fire flow requirements (USA)

Polish fire flow requirements for communities



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Supplementary reading

CH3 Introduction to Water Sources. AlaskaDepartment of Environmetal Conservation.

water supply systems lecture 2

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