Phase one
Prediction of discolouration in distribution systems

Introduction

Historically, a repeated concentration of discoloration events has been used to justify rehabilitation in the form of pipeline replacement or relining. This is no longer an acceptable management strategy, serviceability should be maintained to customers at least cost. Pipe renewal is unlikely to be justified by a sole driver, for example the potential for discoloration events. The development and realisation of proactive management and operation practices is therefore imperative. However, understanding of the detailed mechanisms that lead to discoloration events is limited and hence control is difficult.

Flushing programs have been identified as a means by which discoloration events may be managed. Hydrants are opened to create the hydraulic forces required to remove material that contributes to discoloration events from the localised distribution network.

Flushing is predominately carried out as a reactive measure in response to customer complaints. Accurate predictive modelling would allow the formulation of proactive flushing strategies within network operational management schemes, improving water quality and reducing customer complaints.

Modelling

It has can be shown that once in suspension the materials collected during flushing activities are unlikely to deposit in water distribution networks. Therefore, the modelling situation is not one of erosion, transport and deposition, as for larger cohesionless sediments.

The scenario that requires modelling in distribution systems is the generation, development and erosion of cohesive layers and subsequent material transport as a permanently suspended wash load or solute. These model concepts can be accommodated by consideration in conjunction with calibrated network hydraulic models.

Project objectives

Specific project objectives are to:

• Develop a model to predict discoloration events. The model will operate in conjunction with the EPANET distribution network simulation freeware.

• Collect hydraulic, temperature, continuously monitored turbidity and colour field data and concurrent water samples for the analysis for colour, turbidity, iron content and other water quality parameters in the laboratory.

• Analyse the field and water sample data with the aid of the model in order to further understand the chemical and physical mechanisms associated with discoloration in response to network operational events.

• Utilise the model in a sensitivity analysis to investigate the influence on discoloration of

  1. 1. network make up (eg pipe material, diameter)

     2. hydraulic regime

     3. water quality

     4. temperature

• Undertake ongoing refinement of the model based on the findings of the fieldwork and analysis.

• Investigate the transferability of the model between areas of different water quality and between seasons.

• Derive an end of pipe model to describe the release of sediment build up from dead end mains upon hydrant operation during flushing.

• Investigate hydrant behaviour during flushing operation.

• Derive a basic computational routine/model to identify areas of most likely deposition of larger bed load type particles.

Journal and conference papers

Boxall, J B, and Saul, A J (2005)
Modelling discolouration in potable water distribution systems. Journal Environmental Engineering ASCE, vol. 131, no. 5.

Boxall, J B, Saul, A J and Skipworth, P J (2004)
Modelling for hydraulic capacity. Journal of the American Water Works Association, vol. 96, no. 4, pp. 161–169.

Boxall, J B, Skipworth, P J and Saul, A J (2003)
Aggressive flushing for discolouration event mitigation in water distribution networks. Water Science and Technology – Water Supply, vol. 3, part 1/2 pp. 179–186.

Boxall, J B, Unwin, D M, Husband, P S, Saul, A J, Dewis, N and Gunstead, J D (2003)
Water quality in distribution systems: rehabilitation and maintenance strategies. Proceedings of the International CCWI conference, Advances in Water Supply Management, 15–17 September 2003, Imperial College London, UK.

Boxall, J B, Saul, A J, Gunstead, J D and Dewis, N (2003)
Regeneration of discolouration in distribution systems. Proceedings of the ASCE, EWRI, World Water and Environmental Resources Conference, 23–26 June 2003, Philadelphia, USA.

Seth, A, Bachmann, R T, Boxall, J B, Saul, A J and Edyvean, R (2003)
Characterisation of materials causing discolouration in potable water systems. Water Science and Technology, vol. 49, no. 2, pp. 27–32

Boxall, J B, Skipworth, P J and Saul, A J (2001)
A novel approach to describing sediment movement in distribution mains, based on measured particle characteristics. Proceedings of the International CCWI Conference, 3–5 September 2001, De Montfort University, UK.

In press (not yet publicly available)

Boxall, J B and Prince, R A
Application of a discolouration model to a Melbourne (Australia) potable water system’. Journal of Water Supply: Research and Technology – AQUA, IWA. Under review.

IWA World Water Congress – September 2004

The poster presentation based on the PODDS project presented as part of this conference is provided here (for members only, password required).

Model code

The EPANET code modified to include turbidity propagation water quality modules is not readily available on this web site but can be obtained by personal request. This is due to developmental nature and the lack of help/support documentation.

The latest standard release of EPANET can be downloaded here.

Project base

• University of Sheffield

• Department of Civil Engineering

• Water Research Group

Project sponsor

EPSRC sponsored project under the WITE initiative.

Project collaborators

• Anglian Water – project sponsor, providing operational experience, field sites and assistance

• Yorkshire Water – project sponsor, providing operational experience, field sites and assistance

• Advantica – project collaborator, providing access to software and experience

• Seven Technologies – project collaborator, providing software and experience

• US EPA – project collaborator, providing support and experience with model coding

• Ewan Associates – project collaborator, providing consultancy experience

Note: all documents and files here are for members only. Password required to access.

EPSRC final report, June 2004

The findings from the PODDS project, detailed to the EPSRC in the final report, June 2004.

PODDS seminar – AWS and YWS, 19 August 2004

The findings from the PODDS project as presented at the Discolouration Seminar held near Newark on 19 May 2004 for Anglian Water Services and Yorkshire Water Services are provided here.

PODDS seminar – UKWIR, 25 May 2004

The findings from the PODDS project as presented at the Discolouration Seminar held in London on 25 May 2004 are provided here.

A poster has been produced to help explain the aims and objectives of this research, including the companies involved and initial work.

Mid-project report

A report providing details of the major findings from the first half of this research project, providing specific details for industrial tools that can be distilled from the knowledge gained.

Minutes from steering group meetings

Preliminary meeting 30 November 2000, minutes.

First meeting 10 April 2001, minutes, presentation.

Second meeting 17 July 2001, minutes, presentation.

Third meeting 27 November 2001, minutes, presentation.

Fourth meeting 2 May 2002, minutes, presentation.

Fifth meeting 14 August 2002, minutes, presentation.

Sixth meeting 3 December 2002, discussion document, minutes, presentation.

Seventh meeting 5 March 2003, minutes, presentation.

Eighth meeting 3 July 2003, minutes, presentation.

Ninth meeting 23 September 2003, minutes, presentation.

Tenth meeting 9 January 2004, minutes, presentation.

Final project meeting 1 April 2004, minutes, presentation, draft seminar proposal, Lewis Rossman communication.

Publications

In press

CCWI 2001 conference. Model mathematics and justification.

IWA 2002 World Water conference. Hydraulic interpretation of results from preliminary fieldwork.

IWA Scale and Corrosion conference 2003. Interpretation of physical results from early fieldwork.

ASCE EWRI conference 2003. Results from regeneration study, and comparison to roughness growth rates.

CCWI 2003 conference. Rehabilitation and maintenance strategies.

Journal AWWA 2004. Hydraulic calibration, diameter and roughness relationships.

Journal of Environmental Engineering ASCE 2005. Initial validation of the modelling approach for prediction of discolouration.

Journal of Water Supply: Research and Technology – AQUA. Transfer of PODDS model to an Australian system.

Reports

Laboratory testing of C&T meters.

Fieldwork and subsequent modelling from Sandy, 5 November 2001 AW01A and discrete sample analysis AW01B.

Fieldwork and subsequent modelling from Keighley K709, 17–19 October 2001 YW01A and discrete sample analysis YW01B.

Fieldwork and subsequent modelling from Sandy, 5 February 2002 AW02A and discrete sample analysis AW02B.

Fieldwork and subsequent modelling from Sandy, 16 May 2002 AW03A and discrete sample analysis AW03B.

Fieldwork and subsequent modelling from Sturton-by-Stow, 23 May to 6 June 2002 AW04A and discrete sample analysis AW04B.

Fieldwork and subsequent modelling from Sandy, 8 August 2002 AW05A and discrete sample analysis AW05B.

Fieldwork and subsequent modelling from Sheffield J796, 20 August 2002 YW02A and discrete sample analysis YW02B.

Fieldwork and subsequent modelling from Sandy, 5 November 2002 AW06A.

Fieldwork and subsequent modelling from Thorpe Audlin M277, 29 October 2002 YW03A and discrete sample analysis YW03B.

Fieldwork from Ipswich East, Rushmere, 15 May 2003 AW07A.

Fieldwork and subsequent modelling from Wortley, 2 October 2002 YW04A.

Fieldwork and subsequent modelling from Fakenham, 18 and 24 February 2003 AW08A.

Fieldwork and subsequent modelling from Sheffield J796, 19 August 2003 YW05A.

Fieldwork and subsequent modelling from Sturton-by-Stow, 25 September to 1 October 2003 AW09A.

Fieldwork and subsequent modelling from Wortley, 8 October 2003 YW06A.

Fieldwork and subsequent modelling from Sandy, 5 November 2003 AW10A.

Fieldwork and subsequent modelling from Fakenham, 19 and 24 March 2004 AW11A.

Other documents

Project timetable.

Contacts list, last updated 3 December 2001.

Responsive letter to phase three serviceability indicators.

Comment on UKWIR particle sizing report.