Working with Southern Water at Isle of Grain WwTW


Southern Water's Isle of Grain treatment works is situated at the very tip of the Kent coast. Until 2018, the site featured a screen & macerator configuration struggling to keep up with operational demands and in need of refurbishment or replacement.



  • Very flat site presented hydraulic challenges
  • Increased flow rates 
  • Potential costly civil adjustments to channel width
  • Minimal disruption to operations

Isle of Grain Old Screen Macerator Configuration

M&N was initially approached by Southern Water's nominated contractor Barhale Trant Utilities (BTU) to supply replacement screening equipment. However, the increasing flow rate and hydraulic challenges of the Isle of Grain WwTW gave the M&N design team the perfect opportunity to demonstrate their innovative thinking and problem solving approach. 


Rather than simply supplying replacement screening equipment, M&N's design team put forward a modular pre-fabricated ‘Turn Key’ Inlet Works package that could be brought to site ready for installation by the contractor; eliminating the need for costly civil adjustments to the channel width.

Isle of Grain SolidWorks Design

By simply removing a section of the existing concrete channel, M&N was able to design a fabricated steel structure, housing all elements required of a functioning Inlet Works. This could then be fitted directly into the channel. 

Featuring two MNSS5 Combined Spiral Brush Screens, a handrake bypass screen and dedicated control panel, this 'lift & fit' unit was able to deliver: screening, washing, transport, compaction and de-watering in a single ‘stand alone’ package.

Isle of Grain MNSS5 Screens

Isle of Grain Hand Rake Bypass Screen

Isle of Grain Control Panel Faceplate

Isle of Grain Discharge

The MNSS5 Combined Spiral Brush Screens were supplied with 6mm perforations. Individually, each screen is capable of handling clean water flow rates of up to 120 litres/sec with a screenings handling capacity of 0.5 cubic metres per hour; achieving the highest average screening capture ratios in their category. 

The packaged solution features many key operational benefits that provide both OPEX and TOTEX savings; including low power consumption, hard wearing components and easy access for routine maintenance as both screens were mounted to pivotal frames. 

Isle of Grain MNSS5 Maintenance

Isle of Grain MNSS5 Pivoted Viewpoint

Isle of Grain Access For Routine Maintenance

Weighing just 1300KGs, the fabricated Isle of Grain inlet channel structure was manufactured at M&N’s Portland headquarters and delivered to site alongside the screening & control equipment ready for installation by the nominated contractors.

Isle of Grain Channel Overview

Isle of Grain’s ‘Turn Key’ Inlet Works package was operational in just 8 weeks and is an excellent example of M&N’s innovative thinking.