Cog Moors

The Cog Moors wastewater treatment works which treats wastewater for Dinas Powys, Sully, Penarth, Barry and the West of Cardiff is receiving an upgrade.

What is the Cog Moors Waste Treatment Works?

Cog Moors is a wastewater treatment works which treats wastewater for Dinas Powys, Sully, Penarth, Barry and the West of Cardiff.

Cog Moors Wastewater Treatment Upgrade

As part of our upgrade of the treatment works, we will be investing over £50 million to install an Advanced Anaerobic Digestion (AAD) plant along with other improvements to the existing site. Our AAD investment once completed will enable us to achieve an energy neutral wastewater site by recovering energy from the waste we process onsite. This will help manage the effects of climate change, reduce our running costs and carbon footprint and help keep your bills low.

Artist impression of the new Advanced Anaerobic Digestion plant once completed.

Here are figures for the new AAD plant once completed:

  • 1.5GWh capacity
  • Will produce 2.028MWh of electricity a year
  • Equivalent of power required to power 3,750 homes per year
  • Help meet Welsh Water renewable energy target.

What is Advanced Anaerobic Digestion (AAD)?

An AAD plant is part of a combined heat and power facility consisting of 2 engines that use biogas from the anaerobic digestion of sewage sludge collected from waste in our sewer system to produce biogas (mainly a mixture of around 60% methane and 40% carbon dioxide) and a biosolid “cake” (a sustainable fertiliser that can be recycled on farmland).

How Does It Work?

The biogas is created by the anaerobic digestion of sewage sludge which is then used in gas powered engines to generate electricity which will be used to power the plant. The left over sludge becomes a biosolid “cake” and is collected and used as a sustainable soil enhancer and environmentally friendly alternative to chemical fertilisers.

Here is a diagram explaining how Advanced Anaerobic Digestion works:

Project Update

August 2019

  • Refurbishment of existing concrete digesters and installation of new digesters begins.

September 2019 – June 2020

  • Delivery and installation AAD plant

October 2020 

  • Start the commissioning of the new AAD plant. 

November 2020 

  • Complete the construction of the new AAD plant. 

February 2021

  • Complete the testing the new AAD plant. Once testing is complete the new AAD plant will become fully operational.
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Developing the AAD plant

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Here is a link to pictures outlining progress made in developing the AAD plant since the summer of 2019.

Engagement with the Community


As part of the development of the works, we will be keeping you informed of developments to the AAD plant through bi-monthly newsletters.

Here is a link to the current newsletter.

Projects Funded In The Community 

The Community Fund is a chance for communities to boost fundraising efforts for good causes in their area. If you live in an area where work is taking place – and you’re fundraising for projects to benefit the community – you could receive funding from Welsh Water up to a value of £1,000. Find out more here
Over the last year, several groups within the Dinas Powys and Sully areas have successfully been awarded funding through Welsh Water’s Community Fund.  


Dinas Powys Tennis Club: Dinas Powys Tennis Club received funding in August to increase the number of young people playing tennis by rejuvenating the junior hard courts and developing the Dinas Powys Tennis Academy. 
Dinas Powys Art Group: Dinas Powys Art Group obtained funding in August for art equipment to improve their art techniques and encourage art throughout the community.  
Dinas Powys Library and Activity Centre (DPLAC): DPLAC received funding in August to buy new children’s seating for them to sit, read and do activities at the library.   
1st Dinas Powys Scout Group:
1st Dinas Powys Scout Group received funding in April to renovate their scout hall by installing a new wood floor in the main community room.  
Murch Bowling Club: Murch Bowling Club secured funding in February. The money will be used to convert an outside grassed area which will include outside tables and chairs and provide an area where members and friends can watch the activities taking place on the bowling green.  


Civil Aid Voluntary Rescue Association (C.A.V.R.A.): In August, C.A.V.R.A. obtained funding to go towards training to expand its expertise into rescue from weirs. 
Sully Village Group: In February Sully Village Group obtained funding to install beach clean stations as part of their beach clean project.  
Sully and Lavernock Library Trust: Sully and Lavernock Library Trust successfully secured funding in February to install a bookshelf mural sign which will help promote the library.  

Lavernock NR Volunteer (part of The Wildlife Trust S Wales): Lavernock NR Volunteer secured funding in February. The money secured will be used to improve the local footpath network and purchase tools which will help volunteers with their work.  

Want to find out more?

If you would like to find out more about our Community Fund and how you can apply, visit Community-Fund

Events and School Visits

As part of the scheme we aim to hold or attend several community engagements events to keep you informed of developments in Cog Moors. Please click here to find out more about the engagement events Welsh Water have attended so far. We have also visited local primary schools in Sully and Dinas Powys to teach children about the work of Welsh Water and our work at Cog Moors.

If you have a community event which Welsh Water could attend or interested in a school visit, please contact Tomos Davies on 07866818183.

Want To Know More?

If you have any queries regarding work on the site, please contact Tomos Davies, Community Engagement Officer on 07866818183. Alternatively, you can call the Welsh Water Call Centre on 0800 085 3968 and ask for Danielle Thomas or Camille Valmalle.

Additional information on the scheme is also available on the In Your Area section of our website.

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Frequently Asked Questions

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We have also produced a Frequently Asked Questions page to answer additional questions.