A major cross-border project, which aims to improve water quality in the shared waters between Northern Ireland and Ireland through enhanced wastewater treatment, has been launched.

The Shared Waters Enhancement & Loughs Legacy (SWELL) project, which has been awarded €35m under the EU’s INTERREG VA Programme, managed by the Special EU Programmes Body, will see the construction of new wastewater treatment works as well as upgrades to sewerage networks on both sides of the border to enhance the quality of water in Carlingford Lough and Lough Foyle.

The improvements to the wastewater assets will help contribute to raising the current EU Water Framework Directive (WFD) status of ‘moderate’ to ‘good’.

Collaborative working

The four-year project – which is being led by NI Water working in partnership with Irish Water, the Agri-Food & Biosciences Institute, Loughs Agency and East Border Region – will culminate in the development of a unique environmental legacy model that can be used to identify how further water quality improvements can be made in these shared waters.

Match-funding for the SWELL project has been provided by the Department of Housing, Planning and Local Government in Ireland and the Department of Agriculture, Environment and Rural Affairs in Northern Ireland.

Strategic approach

Compliance with the WFD requires an integrated approach to the sustainable management and protection of water resources across multiple sectors and national boundaries. SWELL adopts a cross-border management strategy to ensure provision of the necessary water quality improvements within the shared waters.

The desired improvement to water quality will be implemented by means of increasing the quality and/or decreasing the quantity of wastewater discharging to receiving water bodies deemed to be impacting on the shared transitional waters. This ‘end of pipe’ pollutant load is the only mechanism by which the project can be considered to have met its INTERREG VA programme output indicators, since many other external factors have an impact on achieving ‘good’ WFD status.

Infrastructure upgrades

The SWELL project involves a total of eight wastewater infrastructure upgrades, as well as catchment studies and ecosystem modelling within the Carlingford Lough drainage basin and the Lough Foyle drainage basin.

The majority of upgrades involve constructing new wastewater treatment works to deliver a higher quality discharge as well as providing storm storage to protect the receiving watercourses – and ultimately the shared waters – from stormwater spills.

The capital projects are being undertaken on both sides of the border by NI Water and Irish Water working in partnership. The investment under the SWELL project will ensure wastewater is treated and discharged in compliance with EU regulations.

A brief description of the planned work is detailed below:

Warrenpoint Wastewater Treatment Works (Carlingford Lough)

Upgrade of the existing treatment works to address potential loss of untreated wastewater to Carlingford Lough.

Current operational problems at Warrenpoint are due to excessive flows being pumped to the inlet works. This problem is exacerbated by network infiltration/tidal ingress and inadequate flow balancing at the WwTW. A new inlet works, activated sludge process, attenuation tank and aeration tanks are among the new assets being constructed to improve inlet flow management and provide effective use of storm storage facilities during periods of heavy/prolonged rainfall.

Water quality within Carlingford Lough will also be improved through enhancement of the treated effluent.

Newpoint Wastewater Pumping Station (Carlingford Lough)

Newpoint WwPS is currently equipped with three wastewater pumps that transfer flow (approximately 500 litres per second) 1km to Newry WwTW, as well as four storm pumps that pump storm water flows to two storage tanks within the WwPS site. Under the SWELL project, new coarse screening equipment will be provided to protect the existing pumps from blockages and potential loss of wastewater to the adjacent Newry River. Fine screening apparatus will also be provided on the storm tank overflow to provide further protection to the river during periods of prolonged heavy rainfall.

Construction of underground chambers to house the new mechanical screening equipment represents a significant engineering challenge given the restricted site area, extremely poor ground conditions and the need to deal with existing high wastewater flows. Early contractor involvement was utilised to develop appropriate temporary and permanent works designs. These include for the application of sophisticated construction techniques such as sheet piling cofferdams, dewatering systems and piling installations to overcome the challenging conditions.

Omeath Network Improvements
(Carlingford Lough)

Under the SWELL project the capacity of the sewer network in Omeath will be upgraded to transfer more wastewater to a new treatment plant that is currently being designed by Irish Water (separate to the SWELL project). This will involve surface water separation and redirection of storm flows.

Sewer relining and repairs will also take place on the network along with the rehabilitation of 60 manholes, including replacing covers and making structural repairs.

Killea Wastewater Treatment Plant
(Lough Foyle)

Construction of a new 850 PE wastewater treatment plant providing secondary treatment with nitrification and phosphorus removal. Included will be a new inlet works, stormwater holding tank, secondary biological treatment process, final settlement tanks and new control building.

Carrigans Wastewater Treatment Plant
(Lough Foyle)

The upgrade at Carrigans will involve the decommissioning of the existing Carrigans WwTP septic tank – converting this to a storm tank – and constructing a new pumping station at the site. A new 3,500m long rising main will transfer the full Carrigans load to St. Johnston WwTP for treatment.

Donemana Wastewater Treatment Works (Lough Foyle)

A modern replacement WwTW comprising inlet works, two new primary settlement tanks, three new rotating biological contactors, two new final settlement tanks, a refurbished storm tank and a new sludge holding tank.

To facilitate the phased demolition of the existing works and construction of the new works, a compact temporary treatment plant has been set up to maintain treatment capabilities in line with current consent standards. Work is progressing well with the three new RBCs recently installed.

Strabane Wastewater Treatment Works
(Lough Foyle)

The upgrade of Strabane WwTW includes the construction of a new inlet reception chamber with new screw pumps to lift Formula ‘A’ flows to the existing preliminary treatment works. During periods of prolonged heavy rainfall, flows greater than storm flows will be screened to 6mm and pumped to the receiving watercourse. A new inlet balance tank will be constructed at a high level, sized to deal with normal operational flows. During storm events additional flows will be diverted via the overflow weir to the existing storm tanks with screenings caught in a new 6mm side weir screen and returned back to the inlet works for treatment.

Lifford Wastewater Treatment Plant
(Lough Foyle)

Construction of a new 2,500 PE wastewater treatment plant, providing secondary treatment. The upgrade works will consist of a new inlet works, stormwater holding tank, secondary biological treatment process and final settlement tanks as well as a new control building. Upgrades to the network will also form part of the work.

The solutions outlined are being implemented to serve catchment needs over a 25-year projection horizon.

Unique ‘legacy’ model

Setting it apart from other wastewater schemes, the SWELL project includes for an ambitious modelling strategy that seeks to develop a unique ecosystem ‘legacy’ model for both the Lough Foyle and Carlingford Lough drainage catchments. This ecosystem modelling approach with built-in source apportionment, represents a first-time integration of urban drainage, river, coastal and ecology models on a catchment-wide cross-border basis.

Through extensive catchment investigations and the use of innovative modelling techniques, the SWELL ecosystem models can be used to track the pathways of nutrients and contaminants from wastewater, industrial or agricultural sources to determine their impact on the environment within both sea loughs.

The models will be used by the water utilities to facilitate water quality compliance assessments with respect to the EU Water Framework Directive and will inform sustainable asset planning through the apportionment of bacterial and nutrient loading contributions from wastewater and diffuse agricultural sources.

Once the SWELL capital wastewater asset upgrades have been completed, the models can validate that the required INTERREG VA programme outputs and results indicators have been achieved.

Subsequently, on completion of the SWELL project at the end of 2022, the ecosystem models will be held in public ownership to provide a sustainable legacy tool for cross-border use by water utilities, environmental regulators and other stakeholders.

Ultimately, these legacy models will provide a useful platform for future engagement and the progression of an evidence-based decision-making approach to legislative compliance that builds on the skills, relationships and investment planning techniques developed by the SWELL project.