Eela Water WTW

Eela Water Treatment Works (WTW) was originally constructed in 1978 near Ollaberry in Shetland and supplies up to 4.3Ml/d of drinking water to approximately 5,400 people, as well as the Sullom Voe Oil Terminal.

The site has a long-standing history of microbiological and discolouration compliance challenges, largely driven by seasonal peaks in raw water manganese, impacting water quality at customers’ taps.

In response, Scottish Water commissioned a major upgrade to address 29 residual risks identified within the Drinking Water Safety Plan (DWSP) that exceeded action thresholds, including significantly enhancing water quality and strengthening long-term resilience for both the local community and industrial users, ensuring a reliable and future-proof water supply.

RSE was appointed as the Principal Designer and Principal Contractor on the project, delivering the full scope of civil engineering works, process engineering, MEICA, filtration, chemical dosing, clear water storage systems, and commissioning a new 5.7Ml/d ceramic membrane treatment facility, replacing the ageing infrastructure and strengthening resilience for the local community.

The project was delivered using an off-site modular build strategy, and RSE led the full delivery of civil, MEICA, process engineering, and commissioning of the works to replace the existing plant with a new 5.7Ml/d ceramic membrane treatment facility. The new works deploy PWNT’s C37 CeraMac® ceramic membrane system, which RSE has developed into a state-of-the-art modular solution that enhances water quality and operational resilience.

Delivered through RSE’s modular product range, the advanced PWNT C37 CeraMac® ceramic membrane technology, alongside the m-CTU®, m-BWU®, m-CIP®, m-NAC®, and m-NAL® units, were incorporated into the plant upgrade. The Eela Water WTW project was a significant step for RSE in the remote modular deployment of Transportable Treatment Units (TTUs), which house the water treatment technologies.

To minimise disruption and accelerate delivery, RSE applied its innovative Design for Manufacture and Assembly (DfMA) strategy, constructing 42 modular Transportable Treatment Units (TTUs) at its advanced manufacturing facility in Muir of Ord, before transporting them to Shetland. Each modular unit made a 24-hour sea journey via the Port of Cromarty Firth in Invergordon to the Sullum Voe Oil Terminal, before final road delivery and offload to the site.

RSE’s delivery team worked in close partnership with Scottish Water, heavy-lift and out-of-gauge cargo specialists, and logistics partner Malin Group, to oversee meticulous logistical planning, seamless coordination and maximum safety. This collaboration was fundamental to ensuring the efficient and safe delivery of the 42 modules from the fabrication facility to the rural site location.

The upgraded facility at Eela Water WTW included the installation of C37 CeraMac® ceramic membranes, delivered through RSE’s modular product range. RSE’s modular suite, including the m-CTU®, m-BWU®, m-CIP®, m-NAC®, and m-NAL® standard products, delivers consistency, scalability, and reduced environmental impact. These repeatable plug-and-play designs reduce design time, critical spares, and on-site disruption, while improving safety and quality assurance to afford savings in programme costs and carbon, ensuring significant benefits over bespoke site builds.

Through innovative design and applying the DfMA approach, RSE has achieved a reduction in embodied carbon across its modular ceramic treatment product range. This has been made possible by transitioning from welded to bolted structures and using green carbon and stainless steel. Much of the testing and commissioning is carried out in controlled factory conditions, helping us deliver higher-quality installations in shorter timeframes. Factory-based commissioning also allows early detection of defects to minimise rework and ensure higher quality control before deployment. Health and safety outcomes have also improved, thanks to the project teams’ growing familiarity with the product and the continuous refinement of designs to eliminate potential hazards. This combination of modular engineering and sustainable design is playing a key role in modernising water treatment infrastructure.

Raw water for the Eela Water Treatment Works (WTW) is supplied primarily by gravity from the Roer Water Reservoir, with supplementary abstraction pumped from the Eela Water Reservoir. Both sources are blended in an external mixing tank to provide a consistent influent before entering a multi-stage treatment process comprising pre-filtration, automated chemical dosing, coagulation and flocculation, ceramic membrane filtration, limestone contactor treatment, and on-site electrochlorination for final disinfection.

To ensure continuous compliance and operational resilience, the works incorporate more than 70 strategically located sampling points integrated into the SCADA system, providing real-time monitoring across all critical control points. Automated control logic continuously evaluates water quality, and any deviation from predefined limits triggers the immediate diversion of affected water to a dedicated waste handling system for controlled recycling or safe disposal.

This intelligent monitoring and automated response strategy safeguards water quality, minimises operational risk, and ensures only compliant treated water enters the distribution network.

Digital tools and BIM processes continue to play a central role in how RSE manages complex multi-disciplinary projects, like the modular delivery of 42 Transportable Treatment Units (TTUs) for the Eela Water WTW upgrade.

To support the programme works at Eela Water WTW, the RSE Business Information Modelling (BIM) team developed a 4D digital rehearsal using Autodesk products. The team applied the Autodesk Construction Cloud Federated Model to produce detailed 4D animations of the construction and installation sequence for the plant upgrade, enabling stakeholders to visualise the complete project delivery.

This visual planning tool supports transparent collaboration between project teams, stakeholders, and clients, ensuring every phase of delivery is fully coordinated and as efficient as possible. This approach improves coordination across project teams, helping to identify potential issues early and providing a shared reference point for data-driven planning and decision-making.

Embedding digital excellence at the heart of RSE’s project delivery enables collaboration, improves efficiency and reduces errors throughout the project’s design, construction and operational lifecycle phases.

The modular upgrade of Eela Water WTW demonstrates how RSE is driving industry innovation by implementing a highly innovative, productised approach to water treatment; combining advanced ceramic membrane technology with modular design and digital delivery.

Ceramic membranes are a transformative technology, offering durability, reduced energy consumption, and long-term operational benefits. The move beyond traditional bespoke construction by delivering repeatable, scalable solutions such as PWNT’s C37 CeraMac system and supporting integrated units, proves that quality can be improved while reducing programme time, cost and carbon. The treatment process is further enhanced through 70 integrated sampling points linked to a SCADA system, enabling real-time water quality monitoring.

Eela Water WTW embraces RSE’s off-site build approach, with modules manufactured and commissioned in controlled workshop environments. This enabled early identification of defects, streamlined quality assurance, and reduced delays during on-site commissioning.

By combining innovation, sustainability, and operational efficiency, the PWNT C37 CeraMac®   ceramic membrane system positions RSE at the forefront of modern water treatment and recycling technologies, contributing to the secure and sustainable growth of the UK’s water infrastructure.

RSE received the King’s Award for Enterprise in June 2025, in recognition of its contribution to innovation in the water industry. The award acknowledged the off-site build methodology, which was instrumental to the success of the Eela Water WTW project. RSE and Scottish Water were also shortlisted as finalists for the Water Industry Awards 2026, Drinking Water Initiative of the Year award, for the delivery of the Eela Water WTW project, highlighting the success of the modular application of ceramic membrane technology.

The Eela Water WTW project demonstrates a modern, sustainable approach to water treatment infrastructure through the adoption of off-site modular construction and low-carbon design principles. The project has achieved a 17% reduction in embodied carbon of the modular treatment units through the use of low carbon steel, produced using Electric Arc Furnaces and recycled material. The bolted design provides a further reduction compared with traditionally welded modules, due to its energy efficient process and promotes reuse at the end of life.

The modular design also incorporates automated fault detection systems that immediately divert non-compliant process streams to waste handling for recycling or safe disposal, minimising waste generation and supporting efficient environmental management.

From a customer perspective, the off-site manufacturing approach significantly reduces project lead times compared with traditional bespoke water treatment works. By moving construction activities into advanced manufacturing facilities, the project minimises on-site complexity, improves quality, and provides greater programme certainty.

Supported by focused research and development and close collaboration with clients seeking innovative, cost-effective, and sustainable water treatment solutions, the Eela  Water WTW project utilises RSE’s proven modular product range, including PWNT C37 CeraMac® ceramic membrane technology and modular treatment units such as the m-CTU®, m-BWU®, m-CIP®, m-NAC®, and m-NAL®. Together, these technologies provide a scalable, high-performance solution that addresses the evolving needs of the water sector while delivering measurable environmental and operational benefits.

The programme delivery at Eela Water WTW is the result of close teamwork across RSE’s design, construction, delivery, and commissioning teams.

The first modular units were transported and delivered to site in early September 2025, representing a significant milestone in the construction programme. Commissioning activities began on schedule in January 2026 to test and validate the installed systems. The final major milestone will be water into supply due in March 2027, signifying the completion of the project and readiness for operational service.

The combined expertise ensures that every stage, from initial design through to the final module being lifted into place, is delivered safely and to a high standard. As RSE moves into the water into supply phase of the project, the focus remains on maintaining quality, safety, and strong collaboration with Scottish Water.