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North Wales Sludge


Scope challenge,

technological innovation & standard products

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The North Wales Sludge Strategy is the implementation of DCWW’s visionary strategy for disposal of treated sewage sludge. It brings together all the sludge from centres across North Wales and Cheshire to a centralised facility at Five Fords Wastewater Treatment Works.

It provides a greater amount of biogas to heat homes, a more resilient asset base, and a high quality soil conditioner for agriculture. 

The project was made possible by a dedicated team committed to achieving a challenging programme, using innovative ideas and best practice, to bring the best possible outcome for the client via connected thinking and holistic standardisation of assets.


Strategy review

Through workshop consultations and detailed analysis of exported and incoming sludge numbers, we challenged the original proposal for two Advanced Anaerobic Digestion (AAD) sites in North Wales including: 

  • Early engagement with the supply chain and the latest technological advances giving early visibility to solutions and refinement of OPEX calculations.

  • Consultation with logistics staff gave greater detail to transport options including vehicle sizes and routes, to better inform OPEX calculations.

  • Considering availability of landbank to ensure the AAD sites had sufficient opportunity to export treated cake to agriculture.

The key findings were:

  • The volume of sludge generated was estimated at 14,300 - 17,200 tDS/an, significantly less than proposed

  • Reduction in the number of satellite sites from eight to seven 

  • Key equipment to be sized to accommodate future growth.

This meant only one new AAD facility was required, giving a multi-million pound saving for both capital and whole life cost estimates when compared with the original two-site solution.

A further workshop allayed operational concerns, and confirmed standby plant and processes. The satellite sites sludge numbers were then confirmed as a basis of design, pinpointing where investment was required to ensure a high quality sludge fuel.


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Five Fords Innovation

Incorporating the latest BIM tools and survey data in a Revit 3-D model, we achieved a layout that aligned sludge processes with sufficient space for operational activities whilst minimising OPEX costs associated with pumping sludge long distances. This was critiqued and verified by operations and capital client staff in the Igloo - an immersive 360-degree 3D model projection facility. VR headsets also helped give site tours for training and induction. Further innovations included:

  • £1m saved by challenging client standards for sludge storage and re-purposing existing assets to providing sufficient resilience.

  • A conveyor system was selected for cake reception; removing the maintenance challenge of having cake pumps in a deep pit.

  • The existing cake building was re-purposed to save the construction of a new building.

  • A Hybas reactor, an Ammanox Liquor Treatment Plant (LTP) – a UK first – was built to deal with high strength ammonia liquors. This aerated treatment considerably reduces OPEX and chemical dosing compared with traditional processes. 

  • New boiler house fully-assembled off-site.

  • During LTP commissioning, a ‘proof-of-concept’ digital twin, combining real-time data with dynamic wastewater modelling, provided predictive insight into plant performance.

Satellite Sites and standardisation

Despite variances in space and process, we adopted a ‘design once, use many times’ approach to the seven satellite sites due to the commonality in scope of works across all locations. 

We concluded on an ideal standard sized solution for each to meet ALM specifications, and collaborated with the client on defining a process size suitable for all satellite sites.

Early supply chain collaboration saw us agree a solution to efficiently roll out across eight projects; we created a product that achieved a DfMA installation with no on-site fabrication.


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BIM enabled further efficiencies to be realised: each project was developed in 3D using Revit, with components tagged with data exported using Bentley Openplant Intelligent Piping & Instrumentation Diagram software. Once the data was entered into the database, it informed schedules for procurement, testing, commissioning, and eventual client handover to the client (informing O&M requirements and obligations for statutory maintenance).

Want to learn more? Speak to Chris Bolton @ MMB 

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