Initial trails have been conducted in a pipe loop facility (non-temperature
controlled) confirming that material layers can be accumulated and
subsequent discolouration generated in a laboratory based pipe loop.
Issues remain over the practical applicability of these results
as the system operated at 20°C and hence the biological processes
involved may be considered non-representative.
Trials utilising a new temperature controlled pipe test loop facility
at the University of Sheffield are now underway. This is an internationally
unique facility, with the capability of fully recreating operational
pressures and flows and time vary patterns within a controlled environment.
The rig is comprised of 79mm internal diameter MDPE pipe, representative
of pipe currently installed in the UK. The rig comprises over 600m
of pipe, which can be run either as a complete length or as three
independent systems. The control of a laboratory facility will be
used to systematically investigate and quantify the relative impact
of different potentially influencing factors and mechanisms on material
accumulation rates. Only by testing influencing processes in isolation
can a true appreciation of their significance be derived.
Questions that it is proposed to investigate include:
o Is there a steady state self cleaning velocity?
o What are the effects of daily flow patterns? Does this change
if a stagnation period is present?
o Is there an ultimate layer strength for plastic pipes?
• Source water effects:
o What is the effect of changing concentrations of iron, manganese
and aluminium (the dominant metals species found consistently in
o What is the effect of pH, alkalinity, DO etc?
o What would be the influence of introducing a length of cast iron
pipe into the system?
The laboratory based studies will run throughout the programme,
with details of further study to be refined on an ongoing basis
through the steering group and with reference to the field results.
2. Field regeneration trials:
Field sites utilised during PODDS project trials will continue to
be tested in the same manner at determined intervals. This will
provide quantification of regeneration processes within live water
distribution systems, capturing the complex interaction of processes
and variables at each site. This data will provide:
• Confidence in the repeatability of regeneration processes
in sites where conditions do not change.
• Verification of the effects quantified through idealised
laboratory trials by comparison between the different sites and
with respect to changes to these sites.
3. Trunk mains:
Due to the criticality and political sensitivity of trunk mains,
work relating to trunk mains will be subject to change and adaptation
to suit individual company policies and strategies. However, due
to significant level of interest and need for practical tools relating
to discolouration in trunk mains as expressed by the PODDS Water
Company Consortium, the PODDS approach will continued to be developed
for prediction of trunk main response to changing hydraulic conditions.
Critically trials are planned to assess the regeneration of cohesive
material layers responsible for discolouration incidents when mobilised.
With this information strategic fiscal planning can be justified
for capital or operational investment. Trials will be conducted
on a site by site basis as opportunities arise within the companies
of the consortia.