Project outline

Mutton Island Wastewater Treatment Plant is located in Galway serving the entire catchment area of Galway city and its environs. The original plant was constructed and commissioned by Murphy in 2003 and had been operated and maintained by Murphy since it entered service.

This design, build and operate (DBO) project saw Irish Water engage Murphy to refurbish the existing plant and deliver an expansion in capacity from a population equivalent 91,600 to 170,000 followed by a 20 year operation and maintenance period.

Mutton Island Wastewater Treatment Plant uses anaerobic digestion to renewable energy from organic waste and this project also entailed the installation of new combined heat and power (CHP) units to harness the biogas produced to power the operation of the plant.

Key challenges

Mutton Island is located in Galway Bay which is designated as a Special Area of Conservation and is a location of outstanding natural beauty, serving as an amenity to residents of Galway and tourists.

The key challenge which was met on this project was to ensure that we succeeded in delivering the upgrade of the plant without any interruption in either available capacity or performance, thereby ensuring that the project had a positive impact on Galway Bay and its environs.

Project delivery and innovations

Some key aspects of project delivery and innovations included:

• Delivery of a full upgrade of control system hardware infrastructure and software with a completely new SCADA system developed.
• Use of sludge disintegration technology to enhance biogas production.
• Design of new overflow catchment system to mitigate against overflows during storm flow conditions.

Key facts

• Murphy will continue to operate and maintain this plant for Irish Water until 2035.
• Upgrade delivered without interruption to operational capacity or performance.
• Mutton Island Wastewater Treatment Works handles up to 170 million litres of wastewater per day during storm conditions.