Constructed in the 1970s to serve a population of 3,000, Kilrea Wastewater Treatment Works was selected for reinvestment under PC21 due to capacity pressures. The project was designed to improve compliance with NIEA standards and futureproof it against stricter environmental consents. Secondary drivers included improving operational efficiency, reducing energy consumption, and eliminating health and safety risks associated with ageing infrastructure.
The Farrans Glanua JV solution involved the construction of an activated sludge process (ASP) treatment works with a design population equivalent of 4,400, compliant with NIEA discharge standards of 30:50 (BOD:SS). The upgraded facility provides 363m3 of storm capacity, between CSO, Blind and Online Storm Tanks, that previously would have gone straight to the River Bann without storm attenuation. Constructed beside the existing operational works, the project maintained continuous treatment throughout delivery, minimising disruption to service.
Key elements included a Formula A flume and package inlet works, two aeration lanes, dry installed RAS and SAS pumping stations, Delta Hybrid High Efficiency Air Blowers, storm storage tanks, two final settlement tanks, a sludge consolidation tank, and the repurposing of existing final effluent tanks. The site is operated through a new Motor Control Centre (MCC) kiosk. Through collaborative delivery and innovative problem-solving, the project team successfully overcame significant technical and operational challenges while maintaining a strong focus on quality, safety, and long-term resilience.
Client
Northern Ireland Water
Kilrea Wastewater Treatment Works is a strong example of collaborative engineering, delivering a high-quality, fully completed upgrade that improved treatment performance, increased resilience and created capacity for future growth within the catchment.
Working within a constrained live operational site, the team developed practical, innovative solutions that balanced buildability, safety and long-term value for the client and end users.
Limited space and the need to maintain treatment operations throughout construction demanded a carefully considered approach. Our team adopted an in-situ circular concrete construction methodology for the new final settlement tanks, using a sunk shaft approach that reduced excavation, temporary works and interfaces with live assets. Existing infrastructure was also repurposed wherever practical, including adaptation of the original final settlement tanks for final effluent storage and pumping, reducing waste, material use and construction time.
The needs of the end user remained central from concept to completion. Early contractor involvement enabled Farrans Glanua and NI Water to shape the design around operational requirements, maintainability and whole-life efficiency. The ECI process afforded Farrans Glanua the opportunity to assess the load data from the catchment and to select a robust and appropriate treatment process for the nature of the influent after a rigorous and thorough optioneering phase. The completed works improved compliance performance, resilience to treat shock industrial loading, increased treatment capacity and enhanced network resilience, delivering direct benefits to both the operator and the local community by supporting future residential and commercial development. Continuous engagement through workshops, progress meetings and collaborative reviews ensured the client was fully involved in decision-making, helping to secure confidence in both the process and the final outcome.
Buildability was a defining feature of the project. Construction was carefully phased to allow the existing treatment works to remain live, with weekly sludge tanker movements maintained throughout the programme and no loss of service to the community. This sequencing required disciplined project management and close supply chain coordination, ensuring the works were delivered despite the complexity of operating adjacent to live process infrastructure. The quality of finish is reflected not only in the completed structures but in the strong operational performance achieved during commissioning, with the new process significantly outperforming the required discharge standard during the 28-day test period.
Health and safety were prioritised at every stage, with robust controls implemented for excavation works, confined spaces and interfaces with live treatment assets. The chosen construction methods helped minimise risk exposure while supporting efficient delivery.
Sustainability performance was equally strong. Redundant blast furnace slag from the former filter beds was retained for reuse rather than sent to landfill, cutting waste, transport and associated carbon emissions. Sourcing key materials locally also reduced transport impacts and supported the regional supply chain. By extending the life of existing assets instead of replacing them unnecessarily, the team achieved a lower-carbon, resource-efficient outcome without compromising performance.
Public impact was managed sensitively throughout delivery, with the team maintaining essential wastewater services and minimising disruption to local residents and road users while work progressed on the live site. Local knowledge within the delivery team also helped support efficient working and responsive communication during construction.
Now complete, the project stands as a well-managed, high-performing and sustainable infrastructure investment that demonstrates engineering excellence, strong client collaboration and lasting value for the community it serves.
