In September 2014, a one-year design and build project to almost double the capacity of the Mutton Island Waste Water Treatment Plant was completed. Murphy is currently operating and maintaining the facility on a 20-year contract.
The project brief was to increase the capacity of the plant by more than 85 per cent to serve a population of 170,000, while maintaining operation of the existing plant without any outage. The upgraded plant is operated as a non-nitrifying plant, which allows additional aeration capacity, increasing the load that can be treated at Mutton Island.
The project was significantly constrained by Mutton Island sitting within Galway Bay, which is a Natura 2000 site with a Special Protection Area (SPA), designated under the Birds Directive 79/409/EEC and a Special Area of Conservation (SAC), designated under the Habitats Directive 92/43/EEC. It is also a Ramsar Convention Wetlands site and in regular public use for bathing, sailing, fishing and other water-based leisure uses.
A new Combined Heat & Power plant was installed, fired by waste gas released during the treatment process and across the whole installation a new System Control Acquisition of Data and Analysis (SCADA) system was designed and installed by Murphy engineers.
Because of the imperative of maintaining the water quality in the bay, a new overflow catchment system was designed and installed to prevent any noxious discharge in to the bay.
The €5.7m design and build element of the work was completed on time and on budget.
Continued, uninterrupted operation of the existing plant, whilst new facilities were built alongside, was an absolute imperative. At the same time, reliability problems with the existing plant had to be addressed.
In total, five major elements of the existing plant had to replaced or upgraded to ensure the future reliability of both the new and existing plants. These included:
As a result of the upgrade and expansion of the facility by Murphy, the plant has been in continuous operation without any blockage or other failure since July 2015, handling flows in excess of 170,000m3/day in storm conditions.
Conversion of two primary settlement tanks to final clarifiers and a switch to a non-nitrifying process allowed an increase in capacity sufficient to serve 170,000 people’s needs every day.
A thorough review of plant layout and logistics led to a redesign of plant in to a more efficient configuration which requires less intensive use of plant and is designed for in-line maintenance without loss of operating capacity.
Design and construction in-house of innovative overflow screen incorporating a weir for flow measurement.
Integration of stand-alone sludge disintegration units to increase the bio-gas production, improving the efficiency of the on-site CHP facility.
Use of GRP composite and high grade stainless steel components to ensure no degradation of the highly sensitive environment in Galway Bay.
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