Sustainability of water supply: a risk-based approach for distribution networks

1. Sustainability of water supply: a risk-based approach for distribution networks Rehan Sadiq Associate Professor Okanagan School of Engineering University of British Columbia Canada-Mexico Industry-Science Workshop for Innovation in Water Sustainability Technologies March 29–30, 2010 Chihuahua, Mexico

2. Sustainability Sustainable development refers to the development that meets the needs of the present without compromising the ability of future generations to meet their own needs

3. Sustainability Matrices

4. Sustainability Assessment Frameworks

5. Linkage-based Frameworks DPSIR

6. Linkage-based Frameworks DPSEEA Driving Force Pressure State Exposure Effect • Population growth • Economic development • Technology • Water quantity • Water quality • Continuity • Condition of infrastructure • System reliability • Contamination Water quality failure Hydraulic failure Structural failure • Well-being • Morbidity • Mortality Proactive Preventive Hazard Management Protective Corrective Action Water distribution networks Waheed et al. (2009)

7. Human Health Risk Assessment Framework ToxicityAssessment Risk Acceptance Risk Control Risk Characterization Hazard Identification Risk Communication Exposure Assessment Risk Assessment Risk Management

8. Risk vs. Sustainability Sustainability Assessment Risk Assessment 1.0 1.0 Acceptable value of Sustainability index Decision actions Control strategies Interventions Estimated value of Risk index Estimated value of Sustainability index Acceptable value of Risk index 0.0 0.0

9. Water Quality Management • Multiple barrier approach – Precautionary principle • Total water quality management (TWQM) • Hazard analysis critical control points (HACCP) Source water protection Disinfection O&M of water distribution Water treatment Public awareness Monitoring Physical barriers Virtual barrier

10. Water Quality Management Ranking of major water quality issues

11. WRF-NRC Project • WRF-NRC joint study (FYs 2003-2009) • Identify the multiple sources, pathways and causes of water quality failure (WQF) in distribution networks • Develop a framework for integrating effects of various contributory factors to quantify risk of WQF as a function of aging water mains  water quality can be a decision driver for renewal of distribution mains

12. ‘Aging’ Water Distribution Systems • Deteriorated pipes • increased breakage frequency • leaks, softening • leaching, internal corrosion • tuberculation

13. Disastrous Consequences Europe

14. Physical model • Material properties • Pipe dimensions • Internal pressure • Temperature changes • Loss of bedding support… Factor of safety 1 Time (years) Deterioration model • probability of failure • time to failure Failure of System Integrity and Decision-making Distress Indicators Failure consequence (cost of failure) Interpretation and Condition Assessment • Size of corrosion pit • # broken wires, damaged • Coating • Delamination • Tuberculation … • Failure modes • Current factor of safety … • Direct • Indirect and social Decision-making: risk vs. renewal or inspection Failure risk Condition rating Inspection Corrosion initiation

15. Water Main Renewal:Failure Criteria System sustainability

16. Water Main Renewal:Failure Criteria

17. Water Quality Deterioration Mechanisms Water treatment deficiency Leaching Internal corrosion Contaminant intrusion Permeation Biofilm formation Disinfectant loss &THMs formation

18. Water Quality Modelling • Hydraulic simulators (e.g. EPANET) • Residual chlorine, Disinfection byproducts (DBPs) • Organics • Water age • Regression & kinetics-based models • Residual chlorine, DBPs • Biofilm • Corrosion • GIS-based display models

19. Water Quality Modelling Age Pipe materialBreakage frequencySoil propertiesPressureResidual chlorine… Attributes layers Risk map Risk inferencing through scoring methods or MCDA

20. Pipe attributes Site-specific factors (Environs) Water main Pipe deterioration mechanisms Operational and hydraulic factors Water quality deterioration mechanisms Water quality indicators Potential for WQF Mitigative decision actions Risk-based Conceptual Framework

21. Complexity in Evaluating Impacts of Pipes on Water Quality • Pipes of different ages, materials, sizes under varying environmental conditions • Variations in operational and hydraulic conditions • Difficult and expensive to collect data on performance and deterioration • Some factors/ processes affecting pipe performance are not fully understood

22. Complexity in Evaluating … • causes and effects are not well understood… • highly non-linear in behavior… • requires methods that combine human knowledge, experience, expert judgment … • low probability & high consequences… Fuzzy Cognitive Maps (FCMs)

23. wij Cj Ci Ci Cj Ci + 1  Cn Fuzzy Cognitive Maps (FCMs)

24. Potential for Contaminant Intrusion Condition of Potential for leaks Potential for cross- Time to response appurtenances connection Leakage from M6 appurtenances S1 Pressure M8 Contamination M9 M7 Contaminant distance intrusion M1 Leakage from pipes Pipe age M4 Pipe diameter M5 Load level Breakage rate External corrosion Pipe material M M 3 2 GWT fluctuation Burial depth Type of soil

25. Predicting Water Quality Failures (WQF) Supervisory FCM Modular FCMs Physico-chemical WQF Potential for contaminant intrusion  Potential for Internal corrosion Microbiological WQF Potential for leaching  Potential for water quality deterioration mechanisms Potential for Biofilm formation Aesthetic WQF Potential for disinfectant loss and THMs formation   Potential for permeation Potential for WQF

26. V. low V. low Medium Low Low Low V. low Low Low V. low Medium Low Medium V. low Low Medium High V. low Medium Medium Medium V. low V. high Medium V. low V. low Medium V. low V. low V. low Low V. low V. low V. low V. low Predicting WQF…

27. Outputs Potential for water quality deterioration mechanisms Potential for water quality failures Decision Support Tool Q-WARP Inputs Pipe attributes Water quality indicators Environs Operational/ Hydraulic factors Pipe age Pipe diameter Pipe material … pH Res. disinfectant Organic content … Pressure Water age Velocity … Soil type GWT fluctuations Contaminant source …

28. Predict risk of WQF in a given segment of pipe under given set of conditions • Use qualitative/ quantitative input data • Accommodate missing input data • Generate multiple scenarios for different decision actions to facilitate decision-making

30. Basic information about the user and the pipe under investigation is provided. Analysis for the existing condition of water quality in a pipe under investigation. Analysis to identify the key input factors under given conditions. Final report to print and document the results of a scenario. The input data provided in this sheet facilitates subsequent analyses. Water quality analysis for the proposed decision actions for the pipe under investigation. Summary of results

31. Baseline analysis

32. Decision analysis Sensitivity analysis

33. Stanley Street - Philadelphia • A comprehensive study was conducted on the deterioration of water quality in a 540-feet 6" unlined cast iron main in Philadelphia • The pipe was installed in 1874 on Stanley Street. Stagnant conditions of the main’s dead-end configuration caused water quality deterioration • Pipe flushing resulted only in short-term improvement. Though the water main replacement in 1987 has produced acceptable turbidity levels and higher disinfectant residuals, the dead-end configuration still caused poor water quality

34. Stanley Street - Philadelphia

35. Stanley Street… • Scenario 1 (before pipe replacement ~ 1983-1987) • Scenario 2 (after pipe replacement ~ 1987-1988) • Scenario 3 (~ 2002-2005)

36. Scenario 1 – Location 2 Baseline analysis

37. Scenario 1 – Location 2 Decision analysis

38. Scenario 1 – Location 3 Baseline analysis

39. Scenario 1 – Location 3 Decision Analysis

40. Stanley Street - Summary • The water quality is deteriorated due to stagnant conditions at location 3 • Flushing can improve water quality on temporary basis but does not provide a long-term solution. Though the water main replacement has in general improved the water quality at location 2, it had no significant impact on location 3 (especially related to potential for biofilm formation and disinfectant loss) • The looping of water main is an ideal solution to permanently achieve an acceptable water quality in the Stanley Street

41. Stanley Street - Summary • Additional measures may include: • More frequent water quality sampling at location 3 • Installation of smaller diameter pipes – to reduce residence time (water age) • Extension of the dead end well beyond the last point of consumption and installation of a fire hydrant at the very end of the line • Installation of an automatic bleed valve at the end of the dead end to reduce residence time.

42. Summary & Conclusions • Sustainability and risk assessment frameworks can be jointly developed for water supply systems • Proposed approach can be extended to develop a decision support tool for integrated water resource management • Water quality can be used as a main decision driver for rehabilitation/ maintenance/ replacement of water mains, treatment plants, storage reservoirs etc. • Soft computing methods (e.g., FCM) can be used for robust decision-making for complex sustainability problems

43. Thanks for listening You always got to be prepared, but you never know for what - Paradox of risk management Financial supports from Water Research Foundation (US) and the Institute for Research in Construction (NRC-IRC) of the National Research Council of Canadaare acknowledged.