INTRODUCTION TO URBAN WATER DISTRIBUTION - CHAPTER 7 (end) ppt

At the same time, the collectedrevenue is 6,000,000 US$, at an average water tariff of 0.5 US$/m3.Determine: a the delivery on an average consumption day, b the percentage of unaccounted

Workshop Problems

A1.1 WATER DEMAND

PROBLEM A1.1.1Determine the production capacity of a treatment installation for a citywith a population of 1,250,000 Assume a specific consumption per capita

of 150 l/d, non-domestic water use of 30,000,000 m3/y and UFW of 12%

Answer:

Qavg 112 million m3/y or 3.6 m3/sPROBLEM A1.1.2

A water supply company delivers an annual quantity of 15,000,000 m3to

a distribution area of 100,000 consumers At the same time, the collectedrevenue is 6,000,000 US$, at an average water tariff of 0.5 US$/m3.Determine:

a the delivery on an average consumption day,

b the percentage of unaccounted-for water,

c the specific consumption per capita per day, assuming 60% of the totaldelivery is for domestic use

A family of four pays for annual water consumption of 185 m3.Determine:

a the specific consumption per capita per day,

b the instantaneous peak factor at a flow of 300 l/h

Answers:

a q 127 l/c/d

b pfins 14

PROBLEM A1.1.4

An apartment building of 76 occupants pays for an annual waterconsumption of 4770 m3 Determine:

a the specific consumption per capita per day,

b the instantaneous peak factor during the maximum consumption flow

of 5.5 m3/h

Answers:

a q 172 l/c/d

b pfins 10PROBLEM A1.1.5

A residential area of 1200 inhabitants is supplied with an annual waterquantity of 63,800 m3, which includes leakage estimated at 10% of thetotal supply During the same period, the maximum flow registered bythe district flow meter is 25.4 m3/h Determine:

a the specific consumption per capita per day,

b the maximum instantaneous peak factor

Note:

a Specific consumption should not include leakage

b Peak factors include leakage unless the flow is measured at the serviceconnection

Answers:

a q 131 l/c/d

b pfins 3.5PROBLEM A1.1.6

A water supply company delivers an annual volume of 13,350,000 m3.The maximum daily demand of 42,420 m3was observed on 26 July Theminimum, observed on 30 January, was 27,360 m3 The followingdelivery was registered on 11 March:

b the diurnal peak factor diagram,

c the expected annual range of peak flows supplied to the area

Answers:

a Qavg 36,575 m3/d; pfsea 0.75–1.16

b Qavg 1435.6 m3/h

Hour 1 2 3 4 5 6 7 8 9 10 11 12

Note that 11 March is not an average consumption day The average flow

derived from the annual quantity is Qavg 1524 m3/h

c Qmax 2563 m3/h; Qmin 343 m3/hPROBLEM A1.1.7

Estimated leakage in the area from Problem 1.6 is 20% of the daily supply.The leakage level is assumed to be constant over 24 houes Calculate thehourly peak factors for the actual consumption on 11 March

100 m3/h, between 8 a.m and 4 p.m

a Determine the hourly peak factors for the domestic consumptioncategory

b Assuming the industrial and commercial consumption to be constantthroughout the whole year, calculate the average consumption percapita if there are 150,000 people in the area

PROBLEM A1.1.9The registered annual domestic consumption is presently 38.2 million m3.Determine:

a the consumption after the first 10 years, assuming an annual tion growth of 3.8%,

popula-b the consumption after the following 10 years (11–20) assuming anannual population growth of 2.2%

Compare the results of the Linear and Exponential models discussed inParagraph 2.4

Answers:

a In 10 years from now: Qlin 52.7 million m3; Qexp 55.5 million m3

b In 20 years from now: Qlin 64.3 million m3; Qexp 69.0 million m3

PROBLEM A1.1.10The following annual consumptions were registered in the period1990–1995 (in million m3):

Make a forecast for the year 2005

Answer:

Q2005 260.7 million m3(exponential growth of 5%)

A1.2 SINGLE PIPE CALCULATION

PROBLEM A1.2.1

A pipe of length L  500 m, diameter D  300 mm and absolute ness k  0.02 mm transports a flow Q  456 m3/h Determine thehydraulic gradient by using the Darcy–Weisbach formula The watertemperature may be assumed to be 10 C Check the result by using thehydraulic tables in Appendix 4

rough-Answer:

By using the Darcy–Weisbach formula, S 0.0079

From the tables for k  0.01 mm, S  0.007 if Q  434.1 m3/h If

S  0.010, Q  526.9 m3/h By linear interpolation: S 0.0077, which

is close to the calculated result

PROBLEM A1.2.2

A pipe of length L  275 m, diameter D  150 mm and absolute roughness k  0.1 mm transports a flow Q  80 m3/h Determine thehydraulic gradient by using the Darcy–Weisbach formula The water

temperature may be assumed to be 15 C Check the result by using thehydraulic tables in Appendix 4.

a by using the Darcy–Weisbach formula for k 0.2 mm,

b the Hazen–Williams formula for Chw 130,

c the Manning formula for N 0.010 m1/3s

The water temperature may be assumed to be 10 C

Answers:

a S 0.0055

b S 0.0054

c S 0.0049PROBLEM A1.2.4

Determine the maximum capacity of a pipe where D 400 mm and

k  0.5 mm at the maximum-allowed hydraulic gradient Smax 0.0025.The water temperature equals 10 C Check the result by using thehydraulic tables in Appendix 4

Answer:

Qmax 429.8 m3/h

From the tables for k  0.5 mm, Q  384.9 m3/h if S 0.002 and473.2 m3/h for S  0.003 By linear interpolation: Qmax 429.1 m3/h.PROBLEM A1.2.5

Determine the maximum capacity of a pipe where D 200 mm at the

maximum-allowed hydraulic gradient Smax 0.005:

Determine the maximum capacity of a pipe where D 1200 mm and

k 0.05 mm at the maximum-allowed hydraulic gradient:

a Smax 0.001,

b Smax 0.005

The water temperature equals 10 C.

Answers:

a Qmax 5669 m3/h

b Qmax 13,178 m3/hPROBLEM A1.2.7

Determine the maximum capacity of a pipe where D 100 mm and

k  0.4 mm at the maximum-allowed hydraulic gradient Smax 0.01.Use the Moody diagram The water temperature equals 10 C

Answer:

Qmax 22.6 m3/hPROBLEM A1.2.8

Determine the pipe diameter that can transport flow Q 720 m3/h at the

maximum-allowed hydraulic gradient Smax 0.002 The pipe roughness

k 0.05 mm Assume the water temperature to be 12 C Check theresult by using the hydraulic tables in Appendix 4

A pipe, L  450 m, D  300 mm and k  0.3 mm, conveys flow

Q 100 l/s An increase in flow to 300 l/s is planned Determine:

a the diameter of the pipe laid in parallel to the existing pipe,

b the pipe diameter if, instead of laying a second pipe, the existing pipe

is replaced by a larger one,

c the pipe diameter if the existing pipe is replaced by two equal pipes

For all new pipes, k 0.01 mm Assume the water temperature to be 10 C

L  850 m and k  0.05 mm, in the following cases:

a D1 D2 200 mm; Q1 Q2 20 l/s,

L1 460 m, L2 240 m, in the following cases:

that k 1 mm and the water temperature is 10 C

PROBLEM A1.3.2The minimum pressure criterion for the branched system shown in

Figure A1.3 is 25 mwc Determine the surface level of the reservoir

in node 1 that can supply a flow of 50 l/s What will be the water level inthe second tank in this scenario? Calculate the pressures and flows in the

system Assume for all pipes that k
0.5 mm and the water temperature

330/1 50 10

9 6

5

4

3 2

8

7

265/100 Figure A1.1 Network

layout – Problem A1.3.1.

52.5

Nodes: p (mwc) Pipes: Q (l/s)

10.8

31.6

34.5 31.2

31.5

28.7

20.3 31.8

30.1

29.3

3.3Figure A1.2 Pipe flows

and nodal pressures –

Problem A1.3.1.

3 2

Nodes: p (mwc) Pipes: Q (l/s)

34.3

25.1 33.2

32.9

32.0

9.3

Figure A1.4 Pipe flows

and nodal pressures –

Problem A1.3.2.

flows if the demand in node 8 has increased for 10 l/s and in node 10for 20 l/s.

Answer:

See Figure A1.5

Due to the increase in demand, the minimum pressure point hasmoved from node 3 to node 10

PROBLEM A1.3.4Determine the pipe diameters for the layout shown in Figure A1.6, if

the maximum-allowed hydraulic gradient Smax 0.005 Determine the

52.8 53.6

Nodes: p (mwc) Pipes: Q (l/s)

33.4

24.1 31.4

22.3

23.6

19.3

Figure A1.5 Pipe flows

and nodal pressures –

Problem A1.3.3.

? 1

10

9

265

Figure A1.6 Network

layout – Problem A1.3.4.

surface level of the reservoir at the supply point, which can maintain a

minimum pressure of 20 mwc Assume for all pipes that k 0.05 mmand the water temperature is 10 ... A1.8.Nodes to 10 have pressure below 20 mwc To satisfy the designpressure and hydraulic gradient, pipes 3-2 , 2-9 , 9-1 0, 9-8 , 8-6 and 8 -7 have to be enlarged (see Figure A1.9)

respec-A1.4 LOOPED... L 78 0 m,

D  200 mm and k  0.05 mm.

Note:

Remove the branches and add their demand to the nodes of the loop 9-6 A ‘dummy’ loop, 1-2 - 3-5 , should be formed to. ..

b the 24-hour water level variation in the tank, assuming the tank has across-section area of 1650 m2and there is provision for all other pur-poses of 70 % of the total volume,