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.
It is proposed to conduct trials utilising a new temperature controlled
pipe test loop facility at the University of Sheffield. 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 will comprise ~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 II 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,
any work proposed 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, current uncertainty
and need for practical tools relating to discolouration in trunk
mains as expressed by the PODDS II Water Company Consortium, it
is proposed to attempt development of the PODDS approach for prediction
of trunk main response to changing hydraulic conditions. This will
be conducted on a site by site basis as opportunities arise within
the companies of the consortia.