Mayflower Water Treatment Works

A £60M state-of-the-art water treatment works (WTW), Mayflower, was required to replace Plymouth’s outdated Crownhill WTW. The new works can treat a wider range of raw water quality from most sources. This is important as early impacts of climate change are visible, affecting water quality; this is a problem impacting Northern Europe.

Mayflower utilises cutting-edge treatment processes, designed and developed by the leading Dutch water technology company, PWN Technologies.

What we did

The £60M project included a range of infrastructure and non-infrastructure asset groups including raw water mains, intake pump stations and the water distribution system. Pell Frischmann was responsible for the majority of the Geotechnical Design, Structural Design, MEICA Design and the Civil Design of the offsite pipelines, including the waste gravity main.

Pell Frischmann and Arcadis formed a 50/50 partnership to deliver the project. This was due to the scheme’s size and complexity. Therefore, to ensure the scheme was a success, both companies undertook an extremely open and refreshing approach to the delivery of the project. By changing behaviours and working as one entity, the team was able to provide the very best of both companies in terms of global expertise, local specialists, IT and technology. This ethos was recognised and shortlisted for the 2017 British Construction Industry Award: Partnership Initiative of the Year.


Crownhill WTW was built in the 1950s, long before automation, modern water quality standards and operational best practice. Since then, the city of Plymouth has grown significantly and hence replacing this works has been a long-term, hard-fought part of South West Water’s strategic plans for developing the water supply network.

Mayflower WTW is recognised as SWW’s flagship project and Ofwat accepted the ‘exceptional item’ Business Case without challenge and commended the innovative approach to the project. The project benefits include:

  • Good, safe drinking water that has the trust of consumers at all times;
  • Improved resilience in the face of increasing risk of extreme environmental operating conditions;
  • Robust and very efficient process based on an absolute physical barrier to particles and pathogens;
  • Reduced chemical use and waste production;
  • Highly automatable and very compact efficient design.


We’d love to hear from you!

To find out more about Mayflower Water Treatment Works, please contact us through our form here.


  • icon-arrow The new works will be capable of producing up to 90Ml of drinking water every day, with an average of 55Ml a day;
  • icon-arrow The new works will serve around 250,000 customers in Plymouth and the surrounding area and more than 6,000 businesses, including Her Majesty’s Naval Base Devonport and Derriford Hospital;
  • icon-arrow Over the course of the project approximately 4,500mcb of concrete, 410 tonnes of steel reinforcement, 7km of off-site pipeline, 2km of on-site pipe work and 3km of cable ducts were used.
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