Kilcoole, Kilpedder & Redcross WwTPs: extensive design and
installation upgrade package to trio of Irish Water treatment
by Duncan Wildgoose CEng CWEM FCIWEM, Liam Partridge & Ivan
the lift-out aeration grid system at Kilcoole and Redcross -
Courtesy of FLI Water
Wicklow is situated on the east coast of Ireland, south of
Dublin. Kilcoole WwTP is located off Sea Road and the
surrounding topography is agricultural farmland. The WwTP at
Kilpedder is a bordered by woodlands and private dwellings,
while access to Redcross WwTP is by a caravan park in Redcross.
All three sites are under the control of the Local
Authority/Irish Water (LA/IW) and serve a combined population
equivalent (PE) of 4400. FLI Water was commissioned by Irish
Water to undertake a €550,000 programme of work. The expansive,
thorough contract included assessment, design, supply,
installation, testing and commissioning. At all three sites the
work carried out was within the boundaries of the existing
wastewater treatment plant.
The three wastewater
treatment plants serve population equivalents ranging from
Kilcoole WwTP: The existing facility comprised 2
(No.) 6mm fine screens, followed by secondary treatment in a
867m3 aeration tank and humus settlement in 2 (No.) 167m3
concrete tanks. The design criterion was initially 3,000 PE with
a 20/30 (BOD:SS) effluent standard and the treatment plant was
initially designed for carbonaceous BOD removal only. A
phosphorus removal plant was installed in 2013. The main
components of the WwTP were:
Phosphorus removal plant.
2 (No.) final settlement
1 (No.) RAS/WAS pumping
1 (No.) picket fence
Control panel and HMI
system in the existing control building.
Lift-out grid at Kilcoole
Courtesy of FLI Water
walkway at Redcross
Courtesy of FLI Water
The existing works featured a 6mm fine screen, followed by
secondary treatment in a 138m3 packaged aeration and humus
settlement tank. The design criterion was 600 PE with a 20/30 (BOD:SS)
effluent standard. The main components of the existing WwTP
225mm gravity inlet
1 (No.) Haigh ACE 490
screen, capacity 20l/s.
1 (No.) Forward feed
1 (No.) 138m3 aeration
1 (No.) brush aerator.
1 (No.) 15m3 final
Control panel, in the
existing control building.
Flow enters the plant via
a sewer network from the village. Two 2.2kW pumps discharge into
a DN80 rising main. There was no stormwater holding tank
installed on-site. Stormwater overflows from the existing inlet
works through a chamber directly to the adjacent river.
The existing works comprised a 6mm fine screen followed by
secondary treatment in a 239m3 aeration tank and humus
settlement in 71.6m3 concentric final clarifier. The design
criterion was 800 PE with a 20/30 (BOD:SS) effluent standard.
The main components of the existing WwTP were:
Control panels, and HMI
system in the existing control building and tertiary treatment
There is a stormwater
holding tank currently installed at the site. Stormwater
overflows from the existing inlet works and flow enters the
plant via the village’s sewer network.
Sludge return pipework at Kilpedder - Courtesy of FLI
Scope of work
FLI had to collaborate
with both the client (Irish Water) and operator (Wicklow County
Council) to understand the challenges and develop the agreed
solution. Work commenced on 7 March 2016 and took over nine
months. All three projects required a diverse range of
upgrading, to achieve compliance and meet increased capacity
flows. In each site, FLI Water and its subcontractors undertook
all electrical, mechanical, automation/control, building, civil
engineering work and any other work necessary for the successful
completion, commissioning and testing of the finalised works.
The key participants involved in the projects were:
FLI Water Ltd (Main
David Dunne Controls (MCC
& electrical installation)
FLI Water assessed the
existing system and installed and commissioned new solutions at
each of the sites.
At Kilcoole, the project included removing the existing 6mm
automatic screen from the inlet works and modifying the inlet
works itself, to form a continuous channel. A new GRP flume
meter was installed in the inlet works and upgrades were made to
the existing aeration system.
The corroded mild steel
access decking on the walkway over final sedimentation tanks was
replaced and safety hand railings were included on the walkways.
The corroded hydrostatic pipework in the sedimentation tanks was
also renewed. A permanent GMS access stairway was installed to
the picket fence thickener.
There were also
modifications to the control panel, HMI and PLC. Controls,
alarms and interlocks were installed to tie in to the existing
On the Kilpedder project, enhancements included refurbishing the
existing inlet works, which consisted of decommissioning the
existing screen and replacing it with a new stainless steel
inlet chamber with automatic spiral screen rated for 100l/s and
25mm manual bypass screen.
A new RAS/WAS system was installed which consisted of the sludge
return pumps and 36m3 sludge holding tank and associated
pipework. The packaged plant was drained down to seal the sludge
return slot in the clarifier and install four penetrations for
sludge draw off pipework.
screen and sludge tank at Kilpedder - Courtesy of FLI
Further enhancement such
as stormwater handling and ferric dosing system were installed.
The stormwater handling system consisted of 36m3 precast
concrete storage tank, storm pump and interconnecting pipework.
The ferric dosing consisted of 1,200l bunded tank, dosing pumps
and emergency shower unit.
The existing control
panel was removed and a new panel was installed to incorporate
the existing and new equipment. New flow monitoring equipment
was installed at the inlet, RAS, WAS and outlet which further
improved the plants automation capabilities.
At Redcross, part of the refurbishment works was similar to
Kilpedder. Work on the existing inlet works consisted of
decommissioning the existing screen and replacing it with a new
stainless steel inlet chamber with automatic spiral screen rated
for 100l/s and 25mm manual bypass screen.
Also, the existing
control panel was removed and a new panel was installed to
incorporate the existing and new equipment. New flow monitoring
equipment was installed at the inlet, RAS, WAS and outlet which
further improved the plants automation capabilities.
The main part of the
works was to improve the plants process by upgrading the
existing aeration system and installing a new sludge return
system. The existing jet venture aerator was removed and a new
fine bubble diffuser lift-out grid system was installed. The
sludge return system consisted of sludge turn pump, scum removal
system and commissioning of the existing precast concrete sludge
Lift-out aeration grid
As part of the Wicklow
Bundle upgrading work, FLI Water designed and manufactured
off-site a bespoke, lift-out aeration grid system for both the
Kilcoole and Redcross sites. The lift out aeration system was
employed to assist with operation and future maintenance within
the single ASP tank. In this way, it was easy to keep the two
plants on-line throughout the process.
An off-site build
solution helped reduce health and safety risks, with less time
spent on site during installation and associated programme
Example of the
lift-out aeration grid system at Kilcoole and Redcross -
Courtesy of FLI Water
New stairs at
Kilcoole - Courtesy of FLI Water
FLI Water’s technical
team also designed a stormwater handling system in Kilpedder.
This had to be incorporated into the existing system in a very
small footprint, which made the solution challenging in terms of
value and operational efficiency. As a standard, energy
efficient blowers and pumps on VSDs were deployed as part of the
projects. FLI also set up a temporary treatment system, when
draining down the aeration tanks.
operational sites itself presented working issues, including
health and safety coordination and a reduced treatment capacity.
Throughout the work, all three sites remained operational and
achieved required standards.
The three projects
successfully delivered the client’s outcomes. By working
collaboratively with Irish Water and the operators Wicklow CC,
the challenges of working on operational constrained assets with
single stream treatment capacity were overcome. FLI Water was
able to utilise its engineering capability to solve the issues
and then implement a range of off-site solutions including lift
out aeration systems with new high efficiency aeration and PLC
controls to deliver improved process control and energy
During the agreed upgrade
programme, additional works were required. These were delivered
and the contracts were completed in January 2017, with all
plants consistently achieving the client’s licensed
This was FLI Water’s
first project in Ireland and these works have proved to be
useful in developing a relationship and understanding of Irish
Water’s delivery requirements. Irish Water is pleased with the
projects’ results and their success has resulted in FLI securing
future work, in a larger scheme at Enniskerry in Wicklow.
and publishers would like to thank Duncan Wildgoose,
Director, and Liam Partridge, Project Manager, both with FLI
Water, and Ivan Corcoran, Capital Programme Regional Lead at
Irish Water, for providing the above article for