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Minworth Thermal Hydrolysis Plant, Severn Trent


Minworth STW Severn Trent’s largest sewage treatment plant, serving a population equivalent of 1.75 million. The works treats sludge from a population equivalent of 2.3 million made up of indigenous sludge plus imported sludge from various works in south Staffordshire and North Warwickshire. Minworth is Severn Trent’s largest renewable energy facility with 8MW CHP capacity and Biogas to Grid which produces 30% of their green energy.  MWH Treatment was awarded the Minworth THP project in February 2016, after a two stage ECI project. The initial project cost was £37m, with a 35 month programme. Through our early delivery Severn Trent enjoyed increased revenue from exporting gas on 13th June 2018, 4 weeks ahead of schedule, netting them a further £200k.


Minworth was Severn Trent’s first THP and a MWH Treatment Conversion project. Delivering the plant involved full utilisation of the MWHT digital delivery toolbox and off-site construction techniques. These helped save 50,000 work hours on the project. Approximately 70% of the equipment was manufactured and assembled off-site (DfMA) to improve project efficiency, quality and shorten the program. Laser-scanning of assets, 3D models and fly-throughs, and 4D scheduling enhanced the quality and efficiency of the design and construction process from concept through to commissioning.

A key strategic intent of the project has been to increase the amount of renewable energy generated. This included the gas production performance of the 16 digesters and enhanced the output of the existing site renewable power generating station. Exceeding expectations through plant availability greater than 95%.


  • TOTEX benefit from revenue increase and OPEX savings.
  • Enhanced status sludge cake (pathogen free).
  • Reduced carbon footprint (Minworth delivers a third of STW’s 10% AMP 6 reduction target).
  • Improved dewaterability of the sludge to increase cake dry solids and reduce volume.
  • Increased capacity for sludge treatment from existing assets avoiding CAPEX investment.

Innovative approaches

Conversion Project

Minworth THP was identified early as a Treatment Conversion project. MWH Treatment use Conversion projects as vehicles to drive improvement in the way we, our clients and our supply chain deliver innovative change and redefine construction.


Lessons Learnt

The project team, including the client design and operational teams and our critical supply chain, undertook a substantial review of several previous Treatment THP schemes, including ongoing operational feedback. The learning proved invaluable in terms of improving many areas of the Minworth plant, particularly regarding asset integration, access and operation ergonomics.


Digital Toolbox

Our delivery strategy involved the full range of MWH Treatment’s digital toolbox, from visual project initiation, digital scanning, supply chain collaborative planning, digital rehearsal and digital commissioning.

Engagement & integration

Design for Manufacture and Assembly (DfMA)

Since AMP 4, MWH Treatment has been at the forefront of DfMA through its strategic joint venture with EPS (MEPS). An early team objective was to target 70% of the scope to be delivered as DfMA packages. The resulting benefit, in terms of reduced health and safety risk, improved ‘’right first time’’ quality and outperforming the programme, were key factors in the successful delivery of Minworth.


Collaborative Planning / Integrated Working / Early Supply Chain Engagement

A critical factor in all successful MWH Treatment projects, is the early identification and meaningful engagement of our critical supply chain. On Minworth, 80% of our critical supply chain were on board within the first quarter of the design activity. When this was aligned with integrated working and collaborative planning with MWH Treatment and the client, we saw significant additional supply chain value add developed and the programme substantially improved.


Asset Optimisation and Integration Management

A significant portion of the new project would rely on interfacing with existing assets. Integration had to have been achieved with minimum disruption to the existing plant operation. A joint team undertook a risk-based review of existing asset conditions and critical interface activity and scheduling. This resulted in creating the role of a dedicated Interface Manager, to plan, communicate and manage all interface activity.


Health and Safety

Minworth’s delivery involved 110,000 man hours without a single safety injury or significant near miss. It recorded a total of 1,200 positive interventions.


Ahead of Schedule

Minworth THP started exporting gas on 13th June 2018, 4 weeks ahead of schedule, increasing the planned revenue by £200k.



The project was delivered within the initial £37 million budget.



Minworth consistently produces the target 8MW of renewable electricity with 95%+ availability.


Enhanced Quality

Throughout the Minworth project, we recorded 83 non-conformances proactively, avoiding defects at hand-over. The site was awarded a Considerate Constructors Gold Award in 2018.


Operator Satisfaction

“The project achieved transformational operator buy-in’ by employing digital delivery tools”
Jane Simpson, Head of Non-Infrastructure Asset Creation, Severn Trent Water.

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Project installed in 24 months (Traditional Schedule: 48 Months)

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Cost reduction due to digital delivery

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Reduction in design cost through field applications