WASTEWATER SOLUTION
readily through careful control, using
different parameters and design.”
Commissioning a new process such
as that at Davyhulme demands a vast
operational undertaking, of course. Lee
Donnellan, who was UU’s operations
readiness manager for the duration of
the modernisation project, explains: “We
had to consider the start period where
it doesn’t treat. In order for a treatment
process to do its job, it requires a certain
recipe of activated sludge to ensure the
FM ratio is correct. By switching on the
lanes in pairs and in a controlled way,
we introduced the correct recipe from the
well-established activated sludge process
on site. This is what we call ‘seeding’: we
seed the new process with the right type
of micro-organisms that quickly establish
treatment. It’s also acclimatised to the
Manchester home-grown sewage as well.”
Davyhulme new ASP3 plant. Thermal hydrolysis plant.
Throughout this six-month commissioning
process, a combination of on-site testing
and samples taken to the accredited lab
was implemented. On-site testing was
a combination of the in-line instruments
measuring key process parameters, such
as dissolved oxygen, ammonia levels in
and out of the plant, and levels of sludge
in the process at different stages.
Quality tests were also carried out
to conrm the in-line instruments’
accuracy. These results were backed up
by the results taken in United Utilities’
accredited labs at Warrington.
The civils were constructed using
Design for Manufacture and Assembly
(DfMA). It meant most of the concrete
fabrication happened in the factory in
precisely controlled conditions, then the
sections were assembled on site. It’s
faster, cheaper and gives much improved
quality control.
“The use of DfMA and Digital
Engineering was identied as a key
efciency strategy from the tender design
stage to nal construction,” comments
Laing O’Rourke’s project leader David
Marsh. “By using 4D visualisation though
BIM (Building Information Modelling), we
could review each construction activity
to ensure constraints were mitigated.
It provided a representation of changes
and highlighted problems before they
physically occurred on site.
“Compared to traditional on-site
construction, the use of precast elements
and off-site manufacture has saved
6,800 on-site working days, generated
signicant savings and reduced health
and safety risks.”
UU’s Donnellan says one of the
biggest challenges faced was integrating
the old assets with the new ones. “We
cannot stop the ow coming into the
works and, as we turned the new plant
on, we had to carefully manage how we
turned off the old plant. As the process is
a biological one, you have to allow time for
the process to mature.
“The ops readiness role helped to
ensure that the operational team were
involved in the design phase, which
includes risk management and input into
the future operational design,” he points
out. “We used a system called Building
Information Management, which allows a
CGI 3D model of the new works to be built
during the design process.
“It enabled the engineering team and
operators to use a virtual reality headset
to walk through the plans and use their
real-life experience – not theory – to
reduce issues relating to access and
introduce simple, yet effective, ideas,
such as moving sample points, access
platforms, stairways, pump control etc.”
A plan was also devised to ensure
training was t for purpose and that all
the EO&M manuals were in a format
suitable for operations.
All in all, this has been a massive
undertaking that now stands as clear
testament to sewage treatment, and
sludge management and disposal, at
its most effective and surely a guiding
light for the future.
FACTFILE
Davyhulme wastewater treatment works
can treat up to 714 Mld (million litres a day)
during storm conditions
The onsite Manchester Bioresources
Centre produces around 33 million cubic
metres of biogas per annum
Each gas bag contains 9,000 cubic
metres of biogas
CHP engines on site can generate up to
60 GWh of electricity per annum
The site can inject 450 cubic metres of
biomethane per hour into the gas supply grid.
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