Hexham Site Case Study

The project involved decommissioning two redundant trickling filters and constructing two new 28-metre units, complete with new wall units, tiles and media. Through smart material management and sustainable construction practices, the team ensured full environmental compliance and enhanced long-term treatment reliability – all delivered on programme and to exact client specification.

Case Study: Hexham STW Biofilter Refurbishment

Sector: Water / Wastewater
Media Handled: Sludge / Slurry / Sewage
Client: Northumbrian Water
Project Value: £4.9 million
Location: Hexham STW
Completion: December 2023

Bagnall Environmental was appointed to deliver asset upgrade works on a major refurbishment to Hexham Sewage Treatment Works. Commissioned by Northumbrian Water, aimed to improve treatment performance, ensure long-term asset resilience, and protect water quality in the River Tyne.

Our scope of works included the safe decommissioning of two redundant biological filters and the construction of two new 28-metre diameter biofilter structures, inclusive of all associated infrastructure and filter media.

Following mobilisation in September 2023, Bagnall carried out a series of integrated works, including:

Decommissioning: Removal of existing distributor for refurbishment and extraction of legacy filter media.

Material Management: Processing removed materials to facilitate a recycled product, with select materials diverted from landfill.

Structural Works: Demolition of redundant filter walls and preparation of retained foundations for reconstruction.

New Construction: Installation of new precast concrete walls, tiles, ventilations system and new ring beam cast around the external perimeter of the filters.

Filter Media Installation: Supply and installation of new filter media to the required specification, placed and levelled to optimise biological performance.

Environmental Measures: All water used in media handling processes was treated on site prior to controlled return to the works, minimising impact on existing treatment operations.

The refurbishment was completed in line with programme requirements and to full client specification. Through considered material reuse and careful sequencing, the project met environmental compliance targets while contributing to improved operational efficiency and long-term reliability of the treatment process at Hexham STW.