Management of discolouration in drinking water distribution systems
Submitting InstitutionUniversity of Sheffield
Unit of AssessmentCivil and Construction Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Mathematical Sciences: Statistics
Information and Computing Sciences: Computer Software
Economics: Applied Economics
Summary of the impact
Research, undertaken at the University of Sheffield since 2001, into the
discolouration of drinking water occurring within distribution systems has
had economic, policy and professional practice impacts on the water supply
sector since 2008. This has resulted in improved levels of service, has
safeguarded water quality delivered to the public and has delivered
substantial economic savings. For example, in one of the few cases where
monetary value is available, Wessex Water made 63% savings on two trunk
main schemes with an initial estimated cost in excess of £1M. The 4 and 7
km lengths of these trunk mains represent less than 1% of the trunk mains
being impacted by our research. Our research has resulted in a step change
in the concept and approach to the management of discolouration in water
Discolouration is the single biggest cause of customer contacts related
to drinking water quality. Research undertaken exclusively at the
University of Sheffield since 2001 has proposed, developed, validated and
applied a novel approach to the conceptual and practical understanding of
discolouration in drinking water distribution networks. This has led to
new operational and management strategies and has seen the development of
the PODDS model for the Prediction and management Of Discolouration in
Distribution Systems. The research initially proposed a unique concept for
understanding discolouration in potable water distribution networks.
Rather than considering gravity driven sediment transport processes, as in
river environments, PODDS considers the build-up of discolouration
material on pipe walls as cohesive layers and describes how these layers
interact with hydraulic conditions to dictate material behaviour. This
step change has its basis in the analysis and characterisation of material
responsible for discolouration undertaken by Saul, Skipworth and Boxall.
This initial analysis was fundamental to the 3-year PODDS 1 project funded
by the EPSRC in 2001 (GR/R14101/01). Subsequently, a consortium of water
companies has funded, in the form of `club contracts', a further 3 rounds
of completed research PODDS II — IV, thereby illustrating the importance,
timing and impact of the research to industry.
PODDS 1, 2001-2003, included detailed research into material
characterisation, model formulation and initial validation through
fieldwork, as presented in [R1]. From 2002 onwards Boxall led the research
supported by Husband. Following the completion of PODDS 1, the benefit and
practical potential of the new approach and modelling tools were
recognised by industry and this led to PODDS II, `Realising the potential
of the PODDS model for the UK water industry', 2004-2006. This research
resulted in a national validation of the conceptual approach through
extensive field studies and the initiation of supporting controlled
laboratory based experiments to fully verify the approach [R2].
Subsequently, PODDS III, `Managing Discolouration: Research informing
practice', 2007-2009, enabled the development of risk based computational
tools, repeat testing of field sites to explore the impact of asset
deterioration, the development of an internationally leading full scale
temperature controlled laboratory facility and initial exploration of
discolouration issues associated with trunk mains. Key practical results
were published in [R3] and later these and further deterioration studies
were reported in [R4].The role and importance of discolouration in trunk
mains was recognised and led to PODDS IV, `Discolouration in trunk mains'.
2010-2013. Here attention was firmly focused on trunk main applications
with further fieldwork to understand and predict long term performance and
to inform management decisions, as reported in [R5].
When the original PODDS EPSRC funding proposal was written, the decision
was made that any software developed with public funding should be open
source. Hence there is no revenue stream associated with the software. The
PODDS modelling tool was developed and incorporated into the United States
Environmental Protection Agency freeware software, EPANET. The calculation
engine and functionality of EPANET are recognised as internationally
leading, globally applied in research and practice and provided the ideal
opportunity to ensure that the discolouration research was recognised as
world leading and internationally relevant. For example, [R6] provides
evidence of application to Australian networks.
|| Affiliation / position and
| Boxall, J B
|| UoS - PDRA 2001-02; L 2002-07; SL 2007-09; Prof.
| Husband, P S
|| UoS - RA 2002-10; PDRA 2010-current
| Saul, AJ
|| UoS - Prof. 2001-current
| Skipworth, P J
|| UoS - PDRA 2001-02
| Whitehead, J
|| United Utilities – co-author, acknowledging industrial
input and support
| Prince, R A
|| Swinburne Uni. Australia - co-author, acknowledging
References to the research
In total 10 leading peer reviewed journal publications and over 20
presentations at international conferences have been made. * denotes best
indicator of quality of research.
R1. * Boxall, J.B., and Saul, A.J. (2005) `Modelling discolouration in
potable water distribution systems'. Journal Environmental Engineering
ASCE. Vol 131, No. 5. pp 716-725. doi: 10.1061/(ASCE)0733-9372(2005)131:5(716)
R2. Husband P.S., Boxall J.B. and Saul A.J. (2008) `Laboratory studies
investigating the processes leading to discolouration in water
distribution networks' Water Research Vol. 42, No. 16, pp 4309-4318. doi:
R3. * Husband, P.S. and Boxall J.B. (2010) `Field Studies of
Discolouration in Water Distribution Systems: Model Verification and
Practical Implications' J. Environmental Engineering, ASCE, Vol. 136. Vol.
136, No.1, pp 86-94. doi: 10.1061/(ASCE)EE.1943-7870.0000115
R4. Husband, P.S. and Boxall J.B. (2011) `Asset deterioration and
discolouration in water distribution systems' Water Research, Vol. 45, No.
1, pp 113-124 doi: 10.1016/j.watres.2010.08.021
R5. * Husband, P.S., Whitehead, J. and Boxall, J.B. (2010) `The Role of
Trunk Mains in Discolouration' Proc. of the Institution of Civil
Engineers, Water Management, Vol. 163 Issue WM8 pp 397-406. doi: 10.1680/wama.900063
R6. Boxall, J.B. and Prince, R.A. (2006) `Modelling discolouration in a
Melbourne (Australia) potable water distribution System' Journal of Water
Supply: Research and Technology — AQUA. Vol. 55, No. 3, pp. 207-219. doi:
Details of the impact
The application of PODDS research has had economic impact and has
promoted efficient and effective asset management. It has also had an
impact on policy and practice within the water sector. The impact is based
on a fundamentally new concept to describe the processes of discolouration
in drinking water distribution systems, together with the delivery of
operational management tools. The impact of the research has been well
appreciated by [text removed for publication], as evidenced by the
"...the conceptual approach and resulting tools and techniques from
the discolouration research from the University of Sheffield have
contributed to a step change in culture and practice in the [text
removed for publication]" [S1, [text removed for publication]].
"...provide testimonial to the impact of the University of Sheffield
discolouration research... ranging from a shift in general perception of
the processes and mechanisms involved to full scale adoption of the
PODDS modelling approaches and tools. Impacts from day to day
operational practice and the on-ground to long term strategic.
Improvements to overall levels of customer service and serviceability
levels, leading to reduced levels of discolouration contacts.
Improvements to operational efficiencies. Particularly evident through
application of PODDS for trunk main applications." [S1, [text
removed for publication]].
Delivering impact from PODDS has been a long process, but has been a key
ambition from the outset. Organisations in the water sector have been
actively engaged with a view to influencing both policy and practice,
including running bespoke dissemination and training events. Notably in
2004 and 2007 invited presentations were made at UK Water Industry
Research (UKWIR) technology transfer workshops. The former was
instrumental in gaining UK water supply sector support, the latter to set
best practice standards for inclusion in Distribution Operation and
Maintenance Strategies submissions in water company Asset Management Plans
2009. Perhaps the single most influential factor in ensuring impact has
been the strategy for, and success of, industry consortium funding. This
has ensured the generation of knowledge, tools and techniques that are
practicably applicable and include wide spread programmes of fieldwork for
Impact on practice and policy:
The PODDS concept, tools and techniques feature in the majority of water
companies `Distribution Operation and Maintenance Strategies', submitted
as part of their 5 year Asset Management Plans to OFWAT. These sensitive
strategy documents are highly confidential and hence cannot be directly
referred to here [S1], however:
"PODDS research has had an impact on all Distribution and Operation
Maintenance Strategies (DOMS) and Asset Management Plan (AMP) documents"
[S1, [text removed for publication]].
This indicates that there has been a consequential change in culture,
planning and practice. Engineering consultancy companies use PODDS to
facilitate the design and planning of operational and maintenance
activities and for strategic asset management planning. For example [S2]
provides exemplar evidence of the use of PODDS modelling by [text removed
for publication] to help [text removed for publication] provide resilient
supply options following the flood risk to [text removed for publication]
when 350,000 customers were without mains water supplies for up to ten
"Application of PODDS-style strategies, typically by controlled flow
increases, enables networks to remain operational thereby minimising
both operational costs and discolouration risk" [S2]
[S3] provides evidence of the development and review of a strategic
discolouration investment model by [text removed for publication] also for
[text removed for publication]. [S3] is based on the PODDS concepts, with
Boxall acting as a consultant.
Commercial software used to model distribution networks has also been
impacted. For example Infoworks®, one of the most used
commercial packages in the international water industry, now calculates
and provides shear stress as per the PODDS model [S4].
When substantial undertakings with potential water quality implications
are necessary, or when `major' events occur, water companies are required
to report to the Drinking Water Inspectorate (DWI),demonstrating planning
and due diligence. PODDS has been a feature in such reports since 2005.
[S5] provides an example of the use of PODDS modelling to defend and
explain a recent major discolouration incident occurring in [text removed
for publication] to the DWI; 760 discolouration contacts were received
over three days, covering an area of approximately 60 square kilometres.
Initially such application of PODDS research was directly facilitated by
the researcher team. However, the knowledge and tools, with support from
bespoke training given by the PODDS research group, are now embedded
within water companies. PODDS has become part of the usual business
process within many water companies [S1, 5, 6, 7, 8, 9]. [S6] provides an
example of the use of PODDS modelling and fieldwork (using PODDS based
equipment) by [text removed for publication] modelling team to plan major
trunk main operational activities. This work forms the basis of reports to
the DWI for undertakings relating to 20 particularly strategically
important and high risk trunk mains.
"PODDS model was initially run so that the operational conditioned
state of the system could be determined.... Modelled discolouration
responses were then produced" [S6].
One of the few examples where a water company, Wessex Water, has been
able to make monetary saving figures available shows immediate one-off
saving of £0.6M on two schemes; one with an initial estimated cost of over
£1M, a 63% saving, and one where an estimated spend of £2M was deferred
indefinitely by operations costing only £0.04M [S7]. The 4, 7 and 6 km
lengths of the trunk mains in these examples represent a tiny percentage
of the trunk main in Wessex Water. Extrapolation of the values suggests
multi million pound savings as well as service improvements and risk
reduction [S7]. These figures relate solely to large trunk mains; economic
impacts associated with local distribution infrastructure are
un-quantified. Equivalent savings and benefits are being made by other
PODDS consortium member companies and beyond [S1, 7, 8, 9].
"PODDS has changed the way Wessex Water thinks about managing the risk
of discoloured water... providing alternative cost effective options..."
"...led to a fundamental change in the way [text removed for
publication] understands and now operates our strategic and distribution
networks in relation to the identification of risk and, therefore,
prevention of discoloured water... a key business and regulatory
driver... a key measure of the quality of service we deliver to our
"PODDS theory has also created a change in mind-set in our asset
strategy...directly supports the delivery of OFWATS serviceability
The UK water sector is widely regarded as internationally leading and
customer focused due to its privatised nature, as recognised by [text
removed for publication].
"[text removed for publication] are internationally leading and I am
aware of international interest in and impact from the research from
countries as diverse as the Netherlands to China" [S1, [text removed for publication]].
The adoption of PODDS concepts can be viewed as a critical factor in
helping water companies improve the service they provide to customers, by
ensuring water is clean and safe to drink. The extent and scope of
adoption of the PODDS concepts, and the implementation of tools and
management approaches that use the approach, has been a key factor in
ensuring that the quality of this essential service is delivered at least
cost. Over the five year water industry review period since 2006 the
number of consumers contacting their water supplier to report a problem
with the quality of drinking water, comprising 80% discolouration issues,
in their home or workplace has fallen by one- third [S10]. While many
factors contribute to this reduction, PODDS is recognised as one of the
most influential factors, through its widespread application and inclusion
in water company Distribution Operation and Maintenance Strategies.
Sources to corroborate the impact
S1. [text removed for publication] testimonial to impact of PODDS.
S2. "[text removed for publication] Resilience; Conditioning Plan — Phase
1. [text removed for publication]" (2013) Consultancy report from [text
removed for publication] for [text removed for publication].
S3. "Model Review and Enhancements Specification, [text removed for
publication] — Phase 1 — Discolouration" (2011) Consultancy report from
[text removed for publication] For [text removed for publication].
[accessed 14/6/13]. Web site listing shear stress functionality [text
removed for publication] as an integral part of the international industry
leading hydraulic network modelling software.
S5. [text removed for publication] Document prepared by [text removed for publication] explaining and defending a major recent discolouration
incident by making extensive use of PODDS.
S6. [text removed for publication] Detailed report evidencing internal
water company use of PODDS modelling tools in planning major operational
activities. One in a series of 20 such undertakings by [text removed for
S7. Distribution Risk Manager at Wessex Water testimonial to impact on
trunk main activities including numerical data for 3 trunk mains and key
details for a further 8.
S8. Research and Development Manager at [text removed for publication]
testimonial to impact on business process, practice and overall
S9. Research and Development Manager at [text removed for publication]
testimonial to impact on business process, practice and overall
[accessed 14/6/13]. DWI chief inspectors report providing data on overall