Sustainability Issues inWater Distribution Systems

Tom Walski, Ph.D., P.E., D. WRESenior Product Manager

Water• WaterGEMS

• WaterCAD

• HAMMER

• SCADAConnect

Sewer• SewerGEMS

• SewerCAD

Storm• CivilStorm

• PondPack

• StormCAD

• CulvertMaster

• FlowMaster

Haestad Methods Solutions

Bentley product portfolio

Sustainability – Water Distribution

• Decaying Infrastructure–Breaks–Leaks

• Energy Use–Excessive Head Loss–Pump Stations

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Finances, Water Quality and Utilities’Reputation Can Suffer

WATER LOSS EFFECTS

Revenue impactSocietal impact

Water quality

(Courtesy Christos Iordanou)

Regulatory effectsSource: Societal Impact picture from “WaterGEMS and HAMMER help Manila Water to improve the reliability and efficiency of the Antipolo Water Supply System”, BE Award finalist 2008

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Saving 50% of Water Loss Worldwide, Utilities Could Supply 228 Million Additional People

32.7 billion m3treated water lost annually through leakage

15.9 billion m3treated water lost annually throughtheft / meter inaccuracy

US$ 14 billion

Sources: World Bank Discussion Paper No. 8, Dec. 2006. Table fromAsian Water magazine: World Health Organization, IB-Net, & author’s estimates

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Developed Countries

Eurasia (CIS)

Developing Countries

Supplied population,

millions (2002)

System input

L/capita/day

Estimates of NRW (Non Revenue Water)

NRW as share of

system input (%)

Ratio (%) Volume, billion m3/year

Reallosses

Apparentlosses

Reallosses

Apparentlosses Total NRW

744.8

178.0

937.2

300

500

250

15

30

35

80

70

60

20

30

40

9.8

6.8

16.1

2.4

2.9

10.6

12.2

9.7

26.7

Estimates of worldwide NRW volumes (billions of cubic meters/year)

Total 32.7 15.9 48.6

utilities’ estimated annual cost

Leak Reduction

• Find and fix leaks

• Leak tracking – Understand causes– Map– Asset management

• Pressure management

• Hydraulic analysis

• District metered areas (DMA)

• Impact of breaks (criticality)

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Leak Records

• Most utilities keep leak records

• Many forms– Paper records– Databases– Spreadsheets– Shapefiles– Work orders

• Import to GIS

• Need x-y coordinates – (georeference)

View Leak Locations

Find bad pipes

Analyze Patterns

Diameter,in.

Breaks Break Rate,break/yr/mi

6 25 0.105

8 15 0.082

12 8 0.062

16 2 0.041

24 3 0.056

Look for Relationships

Circumferential breaks

Longitudinal breaks

Corrosion holes

Cast iron 73 7 4

Ductile iron 2 2 15

PVC 23 17 0

Steel 2 1 12

Part of Asset Management

• Leak history feeds into asset management decision making

• Rational, quantifiable basis for decisions

• Nice graphical displays

Darwin Leak Calibration

• Uses differences between known flows and actual flow to suggest leakage “hot spots”

• Needs good data

• Focuses leak detection

AuthorizedDemand

SystemInflow Loss/Theft

Where is the Loss?

DarwinLeak

Leak Test Case

• United Utilities, UK

• Significant leakage was known to be present

• Wanted more than sonic leak detection

• Small demand management areas (DMA) with good flow and pressure data

• Darwin successfully found leak “hot spots”

Lessons Learned

• Need plenty of good data– System flow – Multiple pressure points– Good metered demand estimate

• Best to use nighttime data – Less impact of uncertainty in roughness

• May need additional data collection

Active Leakage Control Using Transient Analysis

• Reduce pipe breakages caused by high pressure transients

• Find areas where breakage is likely

• Water quality impacts

• Design surge protection devices

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(Courtesy HKM Engineering, and Hughes

Supply, Inc. Utility Services Group)

HAMMER is based on technology originally created by GENIVAR (EHG)

Current AnnualReal Loss Volume

Economic Level Real Loss

UnavoidableReal Loss

ActiveLeakage Control

Pressure Management Using Hydraulic Model

• Reduce real water losses through planned pressure reduction

• Used for leaks that can’t be found or fixed in the near future

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Pres

sure

Man

agem

ent

Current AnnualReal Loss Volume

Economic Level Real Loss

UnavoidableReal Loss

Water Loss – Pressure Relationship

• ~ 30 billion cubic m lost each year

• Leakage loss is f(pressure)

• Lower pressure means less leakage

• Must plan pressure management

• Estimate potential savings

• Use model to plan

Estimating Leakage Reduction

n

i

fif P

PQQ ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

Where Qf = final leak rate, Qi = initial leak rate, Pf = final pressure, Pi = initial pressure, n = exponent

What is n?

Literature nReference Values Conditions

Ogura (1979) 1.39-1.72 Slits

Hikki (1981) 0.5 Drilled holes

May (1994) 0.5 fixed area1.5 size = f(P)2.5 long

Fixed areaSize = f(Pressure)Longitudinal

Lambert (2001) 0.52-2.79 Literature

Farley and Throw (2003) 0.70-1.680.63-2.120.52-2.79

UK (1977)Japan (1979)Brazil (1999)

Thornton and Lambert (2005) 0.5-1.6 Function of ILI

Walski et al. (2005) 0.66-0.76 Drilled holes

Greyvenstein and VanZyl (2007) 0.521.38-1.850.79-1.040.41-0.530.67-2.3

Round HoleLongitudinal PVCLongitudinal ACCircumferentialCorrosion steel

Noack and Ullanicki (2007) 0.5 – 1.0 f(soil permeability)

Actual Leaks

Simulated leaks

50 mm PVC Slit

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20 25 30

Pressure, m

Flow

, L/s

37 mm50 mm75 mm100 mm150 mm

Pressure Control Works When

• Zone fed by PRV, variable speed pumps or multiple different pumps

• There are no tanks floating on system

• Leakage is large

• Area is flat

• May only be able to control at night

Reliability Example

16”

12”

12”6”

X 6”

= Valve

Distribution Segments

• Smallest portion of system isolated by valves

• May be – Part of a pipe– One or more pipes plus junctions

• Not consistent with model topology

J-1 P-1 J-2

S-101 S-102S-103

V-21 V-22

Analysis Steps

• Existing model

• Place isolating valves

• Identify distribution segments

• Identify outage segments

• Assess criticality of segments– Connectivity– Hydraulics

Outage Segment

How can you tell your pumps are stealing from you?

• Pumps don’t call out that they are robbing you

• Power company is happy to bill you

• Must look for inefficiency

• Calculating expected energy costs is tedious

• Models can help

Plenty of money at stake

If we use:120 ft$0.10/kwhr65% wire-to-water efficiency

$60/MG$16/ML

10 MGD station~ $220,000/yr

Energy Cost

dteee

kQhpCT

dmp∫=0

γ

dmp eeehpQTkC )(

=

Case studies

• Changing system without changing pump

• Small dead end system

Changing System

• Abandoned old large, uncovered tank

• Installed new tank 20 ft lower• Installed some new (larger) piping• Kept the old pumps• System head curve changed

System Head Curves

Original Improved

3 Cases

• Original pumps – original system

• Original pumps – upgraded system

• New pumps – upgraded system

Efficiency Comparison

Cost Summary

$/MG $/yr

Old System-Original Pump 144 31,147

Upgrade System-Original Pump 138 29,808

Upgrade System-New Pump 118 25,660

dmp eeehpQTkC )(

=

Small Dead End Systems

• Pump sized for peak• Operate below BEP• Is variable speed pump

justified?

Low Flow Comparison

Constant vs. Variable

Comparison - $/MG

High Q Low Q

Variable 51 77

Big Constant 61 107

2 Small Constant 53 64

For lower flow, 2 small constants better

dmp eeehpQTkC )(

=

Thank you

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Strategy: A Long-term Approach with Immediate [Near-term] BenefitsImplement IWA best practices

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Current AnnualReal Loss Volume

Economic Level Real Loss

UnavoidableReal Loss

Replacing pipes with least impact on

customers

Speed and Qualityof Repairs

Detecting and fixing leaksReplacing/installing meters (DMAs)

ActiveLeakage Control

Pres

sure

Man

agem

ent

Managing assets for maximum return In

fras

truc

ture

Man

agem

ent

Source: The “4 Component” diagram promoted by IWA’s Water Losses Task Force (Thornton and Lambert, 2005)

Background: Water Loss Related Terms

System input volume

Authorized consumption

Billed authorized consumption

Billed water exported

Revenue waterBilled metered consumption

Billed unmetered consumption

Unbilled authorized consumption

Unbilled meter consumption

Non revenue water

Unbilled unmetered consumption

Water losses

Apparent lossesUnauthorized consumption

Customer meter inaccuracies

Real losses

Leakage on transmission and distribution mains

Leakage and overflows at storage tanks

Leakage on service connections up to point of

customer meter

Source: IWA “best practice” standard water balance

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