As part of the Yorkshire Water AMP6 Medium Treatment Framework, Sweco (as part of MS2JV) were appointed by Yorkshire Water to investigate and resolve issues at Clayton West Sewage Treatment Works.


Client: Yorkshire Water

Location: Clayton West, West Yorkshire

Date: 2016 - 2018

Value: £5.3 million 


In 2014 Yorkshire Water undertook investigations and an options appraisal for the works required on the site and developed a notional solution for the works. The outline design / notional solution included modifications to the existing primary tank desludge system, a new ASP (Activated Sludge Plant), including new final tanks, a new river outfall, a sludge storage and thickening facility.

Yorkshire Water commissioned MS2JV to undertake Investigation, Risk and Value assessment on the business risk and proposed notional solution.

MS2JV identified additional scope required to enable the proposed notional solution to be implemented and comply with the client’s Specifications and Asset Standards.

MS2JV produced a cost proposal for the client’s notional solution which was above the client’s budgetary constraints.

Furthermore, it was confirmed by MS2JV that the proposed notional solution would not address their business risks.

A detailed Risk and Value process, led by MS2JV, was undertaken to identify possible alternative solutions.


Clayton West is a Sewage Treatment Works located in West Yorkshire between Huddersfield and Barnsley. The site receives flows from a population of approximately 30,000.

Works were required in relation to a change in the ammonia consent limit, as confirmed by the Environment Agency.

The solution included the construction of a new two stream, four reactor, Moving Bed Biolfilm Reactor (MBBR) with a working volume of 542m3.

Primary services:

• Feasibility Study
• Process Design
• Optioneering
• Geotechnical Investigations
• Environmental Surveys
• Environmental permit applications
• Stakeholder Management
• Hydraulic Analysis
• Civil & Structural Engineering Design
• MEICA Design
• Cost Assessments

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The Risk and Value process concluded that an MBBR (Moving Bed Biolfilm Reactor) process is capable of meeting the 3mg/l ammonia consent.
MS2JV process study of the existing treatment works confirmed that the existing treatment processes on site were consistently meeting an ammonia level of around 5mg/l. With agreement by the client that any risks associated with the existing treatment plant were acceptable the revised, notional solution proposed by MS2JV is the addition of the MBBR plant between the humus settlement tanks and tertiary treatment lagoon. The new solution at Clayton West STW is:

• New MBBR feed pumping station complete with duty/assist/standby variable speed pumps
• A new MBBR distribution chamber
• A new two stream, four reactor, MBBR with a working volume of 542m3
• Associated ancillaries, MCC, instrumentation, etc.
• Duty/standby primary sludge RAM pumps

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