Seedy Mill Water Treatment Works

Water Treatment Works


The accelators at the Seedy Mill Treatment Works were originally installed in the 1950s with their performance deteriorating over many years.

IWS engaged with Degremont (the intellectual property owners) to assess the possibility of refurbishing the accelators to improve their performance against current water quality requirements. The refurbishment cost was significantly less than the cost of replacement and provided the same level of serviceability and asset life.

Project Scope

The project scope involved the removal of the existing mild steel accelator and platform with new stainless steel, reverse engineered accelator.

Further areas of scope included:

  • Replacement of existing regulator; motor and gearbox with new inverter driven, motor and gearbox
  • Renovation of existing submerged mains within the accelator
  • Replacement of sludge hoppers, access plates and installation of new watertight door all in stainless
  • Installation of an actuated adjustable overflow
  • Replacement of sludge pipework and associated valves
  • Refurbishment of PAC dosing pump skid and conversion to inverter drive
  • Replacement of Sodium Hypochlorite Dosing
  • Pumps associated skids and pipework
  • Renewal of dosing line and installation of instrumentation
  • Replacement of 450mm flow meters and battery back-up actuated valves to all four accelators


The works involved regular working at height and within confined spaces. During the delivery of the project, several challenges arose with the environment. These included the discovery of asbestos, mercury and a weakened high-pressure site auxiliary water main contained within the main pipe trenches. This subsequently resulted in an overall delivery delay of six months.

IWS and SSW appointed specialist contractors for the removal of hazardous substances and the repair to the weakened main.


The accelator was commissioned in February 2014 and after it had ‘settled in’, we utilised the in-house expertise of Degremont to undertake site tests to optimise the operation of the refurbished accelator with a newly actuated adjustable skirt mechanism.

This commissioning was undertaken over several days and offered an insight into how the accelator should be operated to optimise efficiency. This provided IWS with the opportunity to deliver refresher training to the operators at Seedy Mill, ensuring their full appreciation and understanding of the functionality of the accelator.

Benefits Delivered

The newly refurbished accelator has exceeded expectations and has been operated up to 15 Ml/d successfully; the new accelator operates using 90% less of the power of the existing accelators, 5kW down to 0.5 kW.

Given the success of the project, it is the intention of SSW to replace the remaining 3 accelators, such that the base load of the site will absorbed by the accelators, nominally 50 Ml/d, which would equate to an electrical saving of 50kW or circa £35k per annum on electricity alone.

This work has been ‘bundled’ allowing sequential working and volumetric procurement to significantly reduce the overall refurbishment costs.

At present time IWS are replacing a further two accelators and it is hoped by SSW production that funding will be found for the final accelator within this AMP period.

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