Bentley Sewage Treatment Works (STW) Upgrade

Bentley Sewage Treatment Works (STW) has undergone a significant upgrade as part of long-term investment into wastewater infrastructure aimed at improving environmental performance and regulatory compliance. Completed following an investment of over £8 million, the scheme increased storm tank capacity to reduce the frequency of untreated sewage discharges during periods of heavy rainfall. In addition, process improvements were introduced to enhance treated effluent quality, including a reduction in phosphorus levels discharged to the receiving watercourse to below an average of 0.9 mg/l.

SRA Swift Trading’s Role: SRA Swift Trading provided site engineering support during the Bentley STW upgrade, assisting with the delivery of storm tank and treatment process improvements. The role focused on engineering coordination, quality assurance, and compliance within an operational wastewater treatment environment.

Project Details: Bentley Sewage Treatment Works, UK

Client: Water Utility Operator (via delivery partners)

Location: Bentley STW, UK

Project Value: Over £8 million

Completion: 2024–2025

SRA Swift Trading Role: Site Engineer

Project Gallery

Construction site with an orange excavator digging and moving dirt along a retaining wall with wooden panels, under a partly cloudy sky.
Construction site showing rebar reinforcement in foundation, with scaffolding and construction equipment in the background.
Construction site with steel rebar grid for concrete foundation, worker in orange safety gear working on rebar.
View of a construction site with freshly poured concrete slab, surrounded by a temporary metal fence, with soil and rocks at the edges and a rusted metal wall at the back, with trees and cloudy sky in the background.
Construction site with rebar grid preparing for concrete pour, surrounded by dirt walls and construction equipment in the background under a blue sky.
Construction site with metal rebar grid laid out on concrete foundation for future structure, with dirt and construction materials in the background and a clear blue sky.
Construction site foundation with rusted steel rebar grid prepared for concrete pouring, surrounded by dirt and construction equipment in the background.
Construction site with steel rebar framework and workers in orange safety gear working near a wooden wall.

The Bentley STW upgrade represents a substantial investment in wastewater infrastructure aimed at improving both storm resilience and effluent quality. Through its site engineering support role, SRA Swift Trading contributed to the successful delivery of a scheme that reduces pollution risk, enhances river water quality, and supports long-term environmental sustainability objectives.

Scope of Works

  • Provided site engineering support for storm tank capacity expansion, supporting civil construction activities associated with flood storage infrastructure.

  • Assisted with engineering coordination and setting-out for civil and process-related works within the treatment works.

  • Supported quality control processes to ensure works complied with design specifications and environmental performance requirements.

  • Liaised with contractor teams, supervisors, and client representatives to coordinate sequencing of works within a live operational facility.

  • Contributed to site documentation, as-built records, and health and safety file inputs as required.

Safety and Compliance

All works were carried out in line with stringent health, safety, and environmental procedures appropriate for an operational sewage treatment works. Particular care was taken to manage risks associated with live process assets, confined spaces, and interaction with operational staff.

Project Significance

  • Increasing storm tank capacity at Bentley STW significantly reduces the risk of untreated sewage discharges during storm events, supporting improved protection of the local river environment.

  • The upgrade also delivered enhanced phosphorus removal performance, reducing treated effluent phosphorus concentrations to below an average of 0.9 mg/l, contributing to improved river water quality and ecological health.

  • Phosphorus reduction is a key regulatory and environmental objective, helping to limit eutrophication and support biodiversity in downstream watercourses.

  • The project aligns with wider water industry commitments to improve river health, resilience to climate change, and long-term wastewater performance.

Environmental Considerations

The Bentley STW upgrade delivered direct environmental benefits by:

  • Reducing the frequency and volume of storm overflow discharges.

  • Improving treated effluent quality through enhanced phosphorus removal.

  • Supporting compliance with environmental permits and river quality objectives.

These measures contribute to long-term protection of local watercourses and improved outcomes for downstream ecosystems.

Technical Expertise

  • Strong site engineering coordination within complex wastewater treatment environments.

  • Support for the delivery of storm resilience and process improvement infrastructure, balancing construction activity with ongoing operational requirements.

  • Effective quality assurance practices to support both structural integrity and environmental performance targets.

  • Clear communication and collaboration with multidisciplinary delivery teams.

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