A positive impact on everything we touch
Over 2000 dedicated people nationwide
Providing critical infrastructure for the UK
A positive impact on everything we touch
Over 2000 dedicated people nationwide
Providing critical infrastructure for the UK

South West Water

Leading the way with new technology at Mayflower WTW


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Conceptual, outline and detailed design of the process plant with South West Water’s new 90ML/day WTW.

The new, state-of-the-art Mayflower Water Treatment Works (WTW) at Roborough, just north of Plymouth, will replace the outdated treatment works at Crownhill in Plymouth, which was built in the 1950s and is reaching the end of its useful life.

South West Water appointed PWNT, a leading water technology company based in the Netherlands, to use a revolutionary new process. It incorporated a suspended ion exchange with resin regeneration system, inline coagulation and ceramic membrane microfiltration. This was a UK first, and a world second and involved:

1) SIX – Suspended Ion Exchange (comprising of streams of civil contactor tanks with a reusable resin added and regenerated)

2) ILCA – Inline Coagulation

3) Cermac – Ceramic membrane vessels with backwash and ozone washing.

These three separate processes linked together to treat a wide variety of inlet water qualities.

nmcn were awarded the M&E design and build contract to work closely with PWNT. This formed part of our H50 alliance and assisted us to develop the conceptual design from scratch.

nmcn used an in-house 3D Laser surveying team with a FARO laser scanner to carry out a scan of the existing site, which captured all existing asset information. The scan provided a degree of accuracy of +-1mm over 120m and the ability to take measurements from within the scan.

We then created a 3D Federated model of the existing site and the proposed new treatment process works. The federated model allowed full collaboration with all stakeholders and enabled effective change control, this was an integral part of the design.

A 3D model was developed for Mayflower WTW. We integrated models from H5O and checked them against the laser scan, along with the manufacturers’ details and pipework to highlight any clash detection. This provided us with a detailed development and included control panel locations and cabling support systems.

The model elements were BIM Level 2 compliant, which were ready to be used in conjunction with intelligent P&IDs produced for the scheme.

We utilised the latest database driven CAD software. nmcn provided efficient design outputs by populating the Valve, Instrument and Equipment schedules directly from the P&IDs. These contained over 1800 items which were updated throughout the project as further information was provided, which enabled us to develop the process leanly.

Key Information


Leading the way with new technology at Mayflower WTW


South West Water




June 2016 - Ongoing

Benefits at a Glance

Fully integrated production control team
Automated valve and instrument schedules from 3D Model
Pipework reduced by 40%


nmcn self-delivered the majority of the installation at Mayflower with subcontractors only involved for specific work packages. In this instance, subcontracting remained limited to the installation of specialist equipment by the manufacturing company and specialist service providers.

Through management team supervision and monitoring, we ensured that work carried out was in accordance with relevant policies, legislation, approved codes of practice and guidance notes. nmcn operated under the control of a Quality Plan, an Environmental Plan and a Health & Safety Plan, (in accordance with the Construction Design & Management Regulations 2015).

nmcn kept internal and external stakeholders informed by collaborative weekly meetings, design reviews, weekly client progress reports, and weekly project meetings.


nmcn utilised smart P&IDs to develop the process design leanly. This enabled accurate information and removed the manual process of creating valve and instrument schedules.

3D collaborative modelling was an integral part of the design with Integration of:

  • nmcn structural detailed TEKLA models
  • Client civil and building models
  • nmcn laser scan point clouds to minimise differences from the civil as designed
  • nmcn plant 3D pipework data exports for estimating pipework costs
  • Supplier equipment and tank models

nmcn provided a package of 300 drawings for suppliers and the installation team as well as regularly updated 3D models. This allowed adjustment of the design to prevent rework of known issues on site.

The simplification of Ozone pipework was redesigned to sit below the steel platform, which reduced the amount of pipework by 40%. This also increased safety by moving it away from the gantry crane.

Quality: 3D collaborative modelling provided accurate information which removed the manual process of creating valve and instrument schedules.

Regular auditing was carried out to ensure compliance with requirements;

  • Weekly SHE inspection
  • Monthly internal QESH audit
  • Weekly site inspection by Site Manager
  • Monthly H&S inspection by Hurst Setter
  • Monthly Environmental inspection by Hurst Setter
  • Quarterly Hurst Setter QESH audits
  • Regular quality testing by Site Manager
  • Targets for waste arising set
  • Keeping records
  • Regular meetings/exchange of information between client, Principal Designer, Designers, Principal Contractor and Contractors


We were able to assist PWNT to deliver the plant adhering to an overseas contract, within an extremely challenging contract programme. The successful delivery of this project, within such a tight timeframe, was only possible due to our close relationship with the design team.

Mayflower WTW operates a revolutionary new process which nmcn helped drive through the conceptual stage, deliver at the construction phase and support at the commissioning phase.

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