Tactical and strategic discolouration management
Tactical and strategic discolouration management
The discolouration issue
Within water distribution systems there is a continuous cycle of hydraulically mediated particulate material layer generation and mobilisation from the pipe wall. Discolouration as the foremost customer observed water quality failing is principally a result of flows exceeding the conditioned state of the material layers present. This leads to rapid uncontrolled mobilisation of accumulated material from the pipe wall into the bulk fluid. Thus it is critical to have knowledge of the current layer state and be able to predict the discolouration response for possible hydraulic scenarios. From this, intervention strategies, both tactical and strategic, can be designed and implemented to manage the discolouration risk.
Through a nationally coordinated set of scientific drinking water distribution system (DWDS) trunk main studies involving a consortium of water suppliers, discolouration behaviour will be investigated and evidence based pro-active tactical and strategic operational tools and strategies developed and validated. Individual site study results will be directly applicable and of benefit to those specific sites, whilst co-ordinating results across the consortium will allow development of a nationwide database to help understand the factors influencing regeneration.
Two independent but complementary computing techniques will be explored and developed for analysis and interpretation of turbidity response to operational changes in flow. These complementary novel approaches will allow the practical and operational effectiveness of tactical and strategic flow/turbidity control to be planned and assessed. The techniques will also allow investigation of regeneration factors between sites including seasonal (temperature?) variation, hydraulic conditions and organic and in-organic water characteristics.
In addition it is hoped that at some selected sites different maintenance strategies may be applied and changed over the period of study, such as short weekly flow increases or longer interval, longer duration flow increments. This will inform development of optimum longer term operational strategies, potentially including information on downstream impacts from the different strategies to mitigate discolouration risk.
To undertake field studies to evidence a framework such that tactical and strategic DWDS management policies can be planned and implemented to mitigate for discolouration incidents.
To investigate the use, application and operational requirements of tactical smart alarms developed through machine-learning techniques based on measured flow data to predict discolouration response in trunk mains.
To validate PODDS VCDM (Variable Condition Discolouration Model) modelling tool and parameters, with particular emphasis on movement to continuous modelling with improved predictive capabilities.
To perform a detailed quantification of asset deterioration rates in trunk mains based on PODDS VCDM calibration. This will inform strategic distribution and operation maintenance strategies.
Improve understanding of DWDS discolouration processes and factors influencing asset deterioration rates enabling best intervention decision making for managing discolouration risk within a TOTEX framework.
Contacts at the University of Sheffield
PODDS related company publications:
June 2016 – Scottish Water Vision magazine, '... £15 million saving...'
September 2016 – Northumbrian Water in Water and Wastewater Treatment, '... 90% capital cost saving...'
PODDS+ proposal. A two-year PODDS Club membership is proposed to enable the ongoing development of research led industry benefits in discolouration management supporting AMP delivery. The aim of the club is to enable participating Companies to continue and enhance reported benefits, including significant cost savings, improved water quality, regulatory compliance and reduced customer contacts. This will be achieved by ongoing technical support that will include provision of discolouration risk analysis, network planning and delivery, monitoring and modelling and leading of a specialist group. A copy of the collaboration agreement is here.
Phosphate dosing: investigating water quality impact in distribution systems. As the water sector progresses towards lead pipe free distribution and premises systems it was suggested that the internationally unique pipe loop system at the University of Sheffield is ideally suited to investigate the impacts of phosphate dosing in real systems, including the microbiological and associated water quality aspects such as discolouration. This document sets out initial thoughts on what could be done.
Understanding and managing metals and organics through reservoirs and their impact on distributed water quality. This project proposal aims to understand the fate and transport of metals and organics from the treatment works through the water distribution network so that appropriate and cost effective management strategies can be implemented. Specifically, the study seeks to identify how and when different source and sink behaviours occur and how final treated water quality influences these behaviours.
Discolouration and chlorine research in drinking water distribution systems. This report details the research developed in conjunction with the PODDS V project by the University of Sheffield and Dwr Cymru Welsh Water (DCWW). The primary aim of this project was to explore in detail the impact of chlorine concentrations upon biofilm structure, accumulation and mobilisation behaviour in drinking water distribution systems (DWDS). This was to be undertaken in the University of Sheffield's internationally unique pipe-loop research facility. In addition field trials were conducted to compliment the laboratory work with a view to investigating disinfectant residual impact upon material accumulation/regeneration rates in trunk mains.
Regulating discolouration in the UK. This document has been produced to stimulate discussion regarding the current regulation of discolouration related issues in the UK. It attempts to capture some key aspects that have arisen during PODDS events. The questions raised are substantive and potentially controversial.
PODDS VI project proposal, August 2015. Tactical and strategic discolouration management. Through a nationally coordinated set of scientific drinking water distribution system (DWDS) trunk main studies involving a consortium of water suppliers, discolouration behaviour will be investigated and evidence based pro-active tactical and strategic operational tools and strategies developed and validated. Individual site study results will be directly applicable and of benefit to those specific sites, whilst co-ordinating results across the consortium will allow development of a nationwide database to help understand the factors influencing regeneration. This project officially commenced 1 December 2016.
PODDS V project summary 2015. The PODDS V research project has been hugely successful in bringing together multiple aspects of research. Increased scientific knowledge from nationwide and laboratory studies has resulted in cost effective and efficient operational strategies that improve asset performance in water distribution systems with regards to safeguarding water quality. The work and subsequent impact has been recognised academically, by water practitioners internationally and the Drinking Water Inspectorate (DWI). This has only been possible with the active participation of project members helping organise trials that consistently demonstrate the hydraulically manageable and predictable discolouration behaviour whilst facilitating identification of governing processes.
DWI presentation, June 2015. The DWI invited the PODDS group to London to present our research. It was commented by the organisers that 29 (out of 40+ staff including clerical) was best turnout to date for this type of dissemination event.
REF 2014 The Research Excellence Framework (guide). REF is the new system for assessing UK Universities' research. PODDS was submitted as an Impact Case Study and subsequently showcased (one of only five from 514 case studies) as an excellent example of contributions by engineering research to the better provision of public services in a report prepared by Technopolis with the EPSRC, Royal Academy of Engineering and overseen by Professor John Fisher CBE FREng – 'Assessing the economic returns of engineering research and postgraduate training in the UK'.
NTU equivalence – set of plots that demonstrate how turbidity correlates with iron and manganese from national and international PODDS trials.
PODDS flow cytometry protocol. A protocol has been written (by Kat Fish and Stewart Husband) that uses sodium ascorbate for dechlorinating. Sodium ascorbate has been selected as it is basically vitamin C so is safer to handle, store, AWWA approved and not an oxygen scavenger like sodium thiosulphate.
PODDS guiding principles. Based on over a decade of industry leading international research. Includes key innovative priorities for developing efficient, cost-effective pro-active discolouration management strategies and a flowsheet methodology for identifying and prioritising trunk main conditioning.
Some examples of PODDS mediated savings are highlighted in table above (click table to get the PDF document).
PODDS Epanet model parameters can be seen here.
Steering group meetings
Fourth meeting 3 August 2016, University of Sheffield: agenda, presentation and minutes. Additional presentation from Atkins (on behalf of Severn Trent Water) detailing a very large and intensively monitored successful conditioning exercise increasing flows from 25ML/d to 40ML/d as part of the Birmingham Resilience Project. Scottish Water June 2016 'Vision' customer magazine, including a report on PODDS.