PDL Screen Installation to improve P-Removal at Ringsend WwTW
Uisce Éireann
Design, Build and Operate
Dublin, ROI
In 2024, a new Phosphorus Recovery P-Fixation Plant was installed at the Ringsend Wastewater Treatment Plant (WwTP). The P-Fixation Plant receives liquors from the Sludge Treatment Facility, including the Thermal Dryers, and a dedicated Wet Well Pumping Station was constructed to transfer these liquors from the Sludge Dryers to the P-Fixation Plant.
Shortly after completion, CAW recognised that a significant level of solids were being transferred in the Dryer Liquor stream, which was being returned to the P-Fixation Plant.
To reduce the level of solids being transferred, CAW, in consultation with Uisce Éireann, agreed to fit a Huber RoK4 screen in the Wet Well of the Dryer Liquor Transfer Pumping Station, which would significantly reduce the level of solids being returned whilst simultaneously improving the performance and reliability of the P-Fixation process.
To facilitate the installation of the new Huber screen, the chamber and cover were redesigned, a water supply was added for washing, and existing instruments were relocated to ensure smooth integration.
Project Highlights
Project Scope and Delivery
This project involved the comprehensive design, fabrication, and installation of key structural and process elements to enhance the integrity and functionality of the chamber and screening system. The scope of work included:
- Structural Reinforcement: Design, fabrication, and installation of a stainless-steel support structure to enhance structural integrity.
- Water Supply System: Provision of a dedicated water supply to the screen, including appropriate lagging, cladding, and a controlled operational system.
- Chamber Modifications: Creation of a new chamber cover opening for the screen installation and instrumentation relocation, involving precise concrete breaking, cutting, and removal.
- Piping and Instrumentation: Installation of pipework from the chamber inlet to the screen inlet, including supports, and the relocation of sensors and probes for functionality.
- Electrical Integration: Design and implementation of electrical installation requirements.
- Screen Installation and Commissioning within the chamber, integrating with the water and electrical supply, including programming and commissioning.
- Cover and Support Framework: Design, fabrication, and installation of a robust screen cover and support system to ensure long-term stability, efficiency, and odour control.
This project created a structurally sound and optimally functioning system, enhancing process reliability and operational efficiency within the phosphorous fixation facility.
Value Engineering In Action
CAW recently completed the installation of a new Huber RoK4 Pre-Dryer Liquor Screen at Ringsend WwTP, delivering a highly optimised engineering solution that avoided significant civil rework and programme impacts.
Initially, it was proposed that the existing reinforced concrete chamber cover would be fully removed together with the surrounding ground slab to accommodate the installation of a new screen. While technically straightforward, this approach would have involved extensive demolition works, the fabrication and fitting of a new precast cover, and full reinstatement works, resulting in substantial cost, schedule disruption, and interface risks within the live wastewater treatment environment.
A Low-Intervention Solution
Through detailed structural assessment and collaborative value engineering, the CAW team developed a minimised-intervention solution. Instead of full slab removal, a precisely defined cut-out was formed in the existing cover, supported by a purpose-designed stainless steel sub-frame installed beneath the slab. This structural retrofit maintains load-bearing capacity, ensures safe long-term operation, and reduces both installation time and project cost.
Enabling the New Wash-water Supply
A similar engineering-led approach was applied to the new wash-water supply. Rather than installing a dedicated boosted supply requiring pumps, extensive stainless-steel pipework, and cladding/ trace heating services, CAW identified an opportunity to re-route an existing water line using underground HDPE pipework through recently installed duct infrastructure. This solution delivers full hydraulic performance while significantly reducing capital expenditure and above-ground congestion.
Overcoming Space Constraints
In addition, the interface between the new screen inlet and the existing pipework presented a spatial constraint, with a connection point too small for standard fittings. A bespoke removable coupling was designed and fabricated, enabling a secure connection while ensuring the assembly can be easily dismantled for maintenance without operational disruption.
This re-engineered installation strategy not only enhanced constructability and reduced whole-life costs but also demonstrates the technical capability and practical innovation CAW brings to complex retrofit projects in critical infrastructure environments.
Talk to us about your next project
.png)