Tremeirchion - Integrated Constructed Treatment Wetland (ICTW)
Currently, the process of cleaning wastewater in Tremeirchion wastewater treatment works (WWTW) is a traditional method used at most of our wastewater treatment sites.
In Spring 2025, we will be creating a new nature-based process in Tremeirchion wastewater treatment works, known as an Integrated Constructed Wetland Treatment, this is the very first to be set in North Wales, which uses wetland ponds (or “cells”) to clean the water before returning it to the environment.
Most of the Afon Clwyd has been classified, under the updated 2021 Water Framework Directive classifications, as ‘moderate’ status. Treated water from Tremeirchion wastewater treatment works flows into the Nant Pen Isa’r Waen, which feeds into the Afon Bach a tributary of the Clwyd, ~800 m downstream of Tremeirchion wastewater treatment works. The reason for not achieving ‘good’ status is due to high levels of phosphate in the catchment, and the regulator Natural Resources Wales (NRW) has set a total phosphate target of 2mg/l for Tremeirchion wastewater treatment works, which needs to be achieved by 2029. The proposed ICTW has been designed to reduce phosphate levels in the Afon Clwyd to the level set by NRW.
We are actively looking at options to use innovative green solutions instead of traditional ‘grey’ solutions as part of our commitment over the next 5 years to cut our carbon footprint and increase biodiversity at our wastewater sites, and also meeting the phosphate target set by NRW. The wetland trial proposed at Tremeirchion wastewater treatment works has evolved through working closely with NRW on sampling programmes and consenting, and we hope that the trial will be a blueprint for future green solutions within the wider waste sector.
The nature-based approach is a sustainable management of wastewater, which provides the opportunity for environmental and biodiversity enhancement across the site and the wider area.
A planning application has recently been submitted to Denbighshire County Council for the proposed Integrated Constructed Treatment Wetland. Information about our planning application can be found here.
The Integrated Constructed Treatment Wetland process involves creating and connecting three new ponds(“cells”) next to our existing wastewater treatment works. To do this we will purchase part of the field next to our site.
The three ponds will be lined with clay already present in the ground at the site, and each pond will be connected to each other with an underground pipe.
We will plant 30,000 emergent native wetland plants at the bottom of the ponds. These specific plants are designed to clean the wastewater as it passes through each pond.
Before any wastewater reaches the ponds, the wastewater will go through a filtering system to remove any rags and large debris. The water will then slowly travel through the three ponds, and the wetland plants will clean the water at each stage, when the water reaches the third pond it will be clean and ready to be returned to the river.
As well as the planting within the ponds themselves, we will also improve the land around the wetland to a species rich traditional meadow, and most of the soil and clay we dig up to create the wetland pond will be reused and landscaped within the new site, creating an ideal opportunity to enhance biodiversity by planting grasses and wildflowers. This will create habitat suitable for a range of invertebrates, amphibians and reptiles.
Our traditional Wastewater Treatment Works will remain on the site for three years while we trial the new Integrated Constructed Treatment Wetland process. Should the trial be successful, we will then remove the old treatments works and create a meadow area which blends into the ICTW and the landscape of the surrounding area.
What are the benefits of using the nature-based process (SMNR) at Tremeirchion?
- Improved water quality within the Afon Clwyd, reducing Phosphate levels
- Provide biodiversity enhancements
- Reduce carbon impact
The Integrated Constructed Wetland Treatment process:
Our Plans
Should everything go to plan, we will start the construction work on the wastewater treatment works in Spring 2025, and we aim to have the work finished by the end of 2025, but we’ll do our best to finish as soon as we can.
Our contract partners Eric Wright Water will be carrying out this work on our behalf. As all the work will be carried out on private land, it shouldn’t cause too much disruption, but you may notice an increase in vehicles coming and going to the site, as well as some construction noise while we work during the day, but we’ll make sure to keep this to a minimum. This work will not affect your water or wastewater services.
Where are we working?
What will the process look like?
