Ringsend WWTP: boosting capacity and performance on a constrained site

On a highly constrained site serving over 40% of Ireland’s wastewater, we helped Uisce Éireann increase capacity, improve effluent quality and strengthen resilience—while keeping the plant fully operational throughout construction.

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Overview of the Ringsend wastewater treatment plant at sundown in Dublin, Ireland

Project facts

Client: Uisce Éireann
Location: Dublin, Ireland
Date: 2014–2025
Challenge: Expand wastewater treatment capacity and effluent quality improvement on a constrained operational site
Solution: Adaptive consultancy using integrated Nereda and Ephyra technologies for capacity increase and nutrient removal

The challenge: Making a major upgrade fit a live, land-constrained plant

Ringsend receives more than 40% of Ireland's wastewater and is central to sanitation across greater Dublin. Demand was growing, discharge requirements were becoming more stringent, and the existing plant was approaching its practical limits.

Yet the peninsula site offered almost no space for conventional expansion. Its 24 stacked SBRs, each with a volume of 13,500 m3, also had to remain in service while contractors worked alongside the operator.

The project therefore needed a way to add biological and sludge-treatment capacity, improve nitrogen and phosphorus removal, and sequence construction without jeopardising day-to-day treatment.

The solution: Using existing assets differently, not simply building more

Rather than depend on a large new footprint, the biological upgrade paired Nereda aerobic granular sludge with Nereda Hybrid. Working for Uisce Éireann, Haskoning, T.J. O'Connor & Associates and Egis Engineering Ireland developed the upgrade with the plant operator.

Additional treatment was delivered through stacked Nereda reactors, while 12 lower-deck SBRs were upgraded with the hybrid concept instead of being completely reconstructed.Piloting and process proving guided each stage of integration with the operating plant.

The wider treatment train was upgraded at the same time: Ephyra increased sludge-digestion capacity by 50% in the existing digesters, supported by improvements to thermal hydrolysis, struvite recovery, UV disinfection, UF water treatment, sludge thickening, biogas treatment and energy generation.

This project was built on trust and collaboration over many years. Haskoning and their partners worked alongside us to deliver a complex upgrade safely, efficiently and without interrupting critical services

Andy O'SullivanProject Manager Ringsend upgrade project, Uisce Éireann

The result: Capacity and nutrient performance increased within the same site

The completed upgrade raised the plant's design capacity from 1.64 million PE to 2.4 million PE, with a hydraulic capacity of 13.8 m3/s.

Effluent performance now meets targets of total nitrogen below 10 mg/L and total phosphorus below 1 mg/L. Reusing existing SBRs and digesters limited the need for major new structures, while phased delivery kept Ringsend operational throughout construction - even with up to 300 people on site at peak.

Dublin now has a more resilient treatment facility that can support growth and better protect Dublin Bay.

Why Ringsend is a landmark Nereda reference

2.4 million PE within a constrained footprint

Nereda aerobic granular sludge helped lift Ringsend's design capacity to 2.4 million PE without relying on a conventional site expansion. The stacked arrangement makes efficient use of every available square metre at a plant serving greater Dublin.

Nereda Hybrid reuses 12 existing SBRs

Nereda Hybrid was applied to the 12 reactors on the lower deck, improving their performance without complete reconstruction. The retrofit retained valuable civil assets and reduced the amount of new infrastructure required.

Designed for stringent nutrient limits

The biological process was configured to support total nitrogen below 10 mg/L and total phosphorus below 1 mg/L. Nereda's granular sludge performance helped the upgraded plant meet stringent effluent requirements while increasing throughput.

Conversion completed around live operations

Ringsend remained operational throughout the works. Piloting, process proving and carefully phased integration allowed the operator and multiple contractors to work safely around live treatment processes, including periods with up to 300 people on site.

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How we Enhance Society Together

SDG 6

Clean Water and Sanitation: The Ringsend WWTP upgrade strengthens sustainable wastewater management for the greater Dublin area by increasing treatment capacity, improving nutrient removal and effluent quality, and helping the plant meet stringent EU wastewater standards. By protecting Dublin Bay and supporting reliable sanitation services, the project contributes directly to cleaner water and healthier communities.

SDG 7

Affordable and Clean Energy: The project supports more efficient and sustainable plant operations through improved sludge digestion, biogas treatment and energy recovery. By optimising existing assets and increasing sludge processing capacity with Ephyra technology, the upgrade helps make better use of resources already available on site and contributes to cleaner, more reliable energy use within the treatment process.

SDG 9

Industry, Innovation and Infrastructure: The upgrade demonstrates how innovative, resilient infrastructure can be delivered on a highly constrained live site. By applying Nereda Aerobic Granular Sludge, Nereda Hybrid and Ephyra technologies, the project increased capacity and performance without extensive new-build infrastructure, showing how advanced engineering can modernise essential wastewater assets safely and efficiently.

SDG 11

Sustainable Cities and Communities: By expanding wastewater treatment capacity for Dublin’s growing population, the project supports a more resilient and sustainable city. The plant remained operational throughout construction, ensuring continuity of essential services while creating the capacity needed to support future urban growth and protect the surrounding environment.

SDG 12

Responsible Consumption and Production: The project makes more responsible use of existing infrastructure by increasing water and sludge treatment capacity within the current site footprint. Through process optimisation, phosphorus reuse via struvite crystallisation, and reduced need for major new construction, the upgrade supports circular resource use and more sustainable production patterns within wastewater treatment.

SDG 13

Climate Action: Climate Action: The upgrade contributes to climate action by improving the efficiency and resilience of critical wastewater infrastructure while reducing the need for large-scale new construction. Enhanced sludge treatment, biogas utilisation and compact treatment technologies help lower resource intensity and support a more sustainable, future-ready wastewater system for Dublin.

Award recognition for innovation and collaboration

The upgrade of the Ringsend Wastewater Treatment Plant was shortlisted for the Global Water Awards' Wastewater Project of the Year 2026, recognising Uisce Éireann’s visionary leadership in delivering a landmark programme that successfully expanded one of Europe’s largest wastewater treatment facilities. At Haskoning, we are honoured to have contributed to a project of such scale and significance, and we are immensely proud of this recognition. This achievement highlights what can be accomplished when a utility works closely with stakeholders to implement innovative technologies and deliver lasting value for customers, communities, and the environment.

Ringsend WWTP was shortlisted for the GWI Wastewater Project of the Year Award 2026

Case study

Increasing capacity and effluent quality at Ringsend WWTP

Deep expertise and advanced technologies come together to transform one of Europe’s largest plants and secure a sustainable future for Ireland’s wastewater treatment.

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