Ephyra® Anaerobic Digestion Process at Ringsend

As part of Uisce Éireann’s commitment to environmental protection and as part of its broader effort to increase the plant’s capacity to serve a population equivalent of 2.4 million, an advanced Anaerobic Digestion (AD) technology, Ephyra®, has been retrofitted into the existing Digestors at the Ringsend Wastewater Treatment Works and has been operating, successfully, for over 6 months by CAW as the Existing Operator of the Works.  The installation of the Ephyra®  Advanced Anaerobic Digestion (AD) technology marks the first installation of its kind in Ireland, using innovative technology developed by Haskoning.

The new installation was formally handed over to CAW to manage its operation and maintenance at the Ringsend WwTW in June 2025.

What is Ephyra® and how does it work?

Ephyra® is a high-rate, plug-flow anaerobic digestion process designed to maximise biogas production and improve sludge treatment efficiency. Unlike conventional digesters, Ephyra® enables digestion at a significantly shorter sludge retention time, typically around 6 to 8 days, which increases throughput on a compact footprint.

At Ringsend, the system uses a series of digesters working in sequence, which:

• Enhances waste breakdown.
• Reduces energy and chemical consumption.
• Increases biogas output while maintaining consistent, reliable performance.

Why Ephyra® was selected for Ringsend

Ringsend WWTP is Ireland’s largest wastewater treatment facility, serving over 40% of the national population. With the planned capacity increase to 2.4 million population equivalent (PE), space constraints and the need for sustainable solutions were key considerations in selecting Ephyra®.

Rather than constructing new digester tanks, Uisce Éireann opted to retrofit the existing digesters with Ephyra® technology - the first retrofit of conventional mesophilic digesters using this technology. This approach allowed for a significant increase in digester throughput without the requirement to expand the sludge treatment plant’s physical footprint, aligning with both environmental goals and cost-efficiency targets.

Managing the Ephyra® treatment process

CAW has been responsible for operating and maintaining the new Ephyra® treatment process since its installation in June 2025. During the retrofitting phases, CAW continued to act as the plant operator, facilitating the smooth integration of the new Ephyra digestors whilst simultaneously ensuring that the highest standards of safety were maintained, including:

• Coordinating major plant shutdowns and isolations to enable safe execution.
• Ensuring compliance with safety standards at all times.

Operational Excellence Post-Installation

Operating an AD plant requires specialist skills to ensure safety and optimise gas production. Our team provides 24/7 operation and optimisation, working closely with RHDHV and Uisce Éireann. To manage the process effectively, we:

• Monitor system health via KPIs (gas production, alkalinity, solids loading).
• Use advanced instrumentation for real-time feedback and continuous review.
• Maintain a proactive approach to optimisation based on data-driven insights.

Performance Outcomes

The upgrade and proactive operational management have delivered measurable improvements, including:

• Biogas yield and quality have increased significantly.
• Volatile solids (VS) destruction improved from 45% to 54%.
• Loading rate capacity increased to 120 TDS/day, enabling higher throughput.
• Additional biogas now powers a fifth combined heat and power (CHP) unit.
• Reduced biosolids volume, lowering disposal costs and environmental impact.