Supply Chain - Treatment Process Technologies - Nature-based Solutions

Dearne Reach is a 4.3-hectare Integrated Constructed Wetland (ICW) in Clayton West, Huddersfield, designed to enhance water quality along 4km of the River Dearne. Delivered by Mott MacDonald Bentley on behalf of Yorkshire Water, this ICW will reduce levels of un-ionised ammonia and improve storm flow treatment in line with the salmonid fundamental intermittent standards. To deliver this nature-based solution, Mott MacDonald Bentley excavated 13 wetland cells covering over 44,000m2 (equivalent of 7 football pitches!), creating space to house more than 350,000 wetland plants. Project background

As an alternative to the traditional grey infrastructure solution, which initially would have entailed 7,000m3 of additional storm storage and a 4.5km diversion of final effluent to a lower river reach, the Dearne Reach ICW offers a sustainable approach to pollution mitigation. Funded by Yorkshire Water as part of their capital delivery programme, it is currently the largest ICW developed in the UK to improve water quality while increasing storm storage resilience.

Aligning with Yorkshire Water’s WFD drivers and net zero ambitions, this project pioneers an ICW tailored for intermittent storm overflows, distinguishing itself from conventional ICWs that require constant inflow. Its innovative design ensures effective management of stormwater variability and will contribute to driving continuous innovation in nature-based solutions across the water industry.

[caption id="attachment_25943" align="alignnone" width="1200"] Construction of the first cells - Courtesy of MMB[/caption] Integrated constructed wetlands

Constructed wetlands are engineered ecosystems that harness natural processes to treat wastewater, stormwater, and industrial effluents. Sometimes described as ‘nature’s kidneys’ because of their ability to filter and clean wastewater by mimicking natural wetlands, these systems use porous media beds and emergent plants to remove contaminants through physical, chemical, and biological mechanisms.

Various treatment wetland types exist, including free water surface wetlands - also known as integrated constructed wetlands (ICWs).

ICWs allow water to flow above the soil through aquatic plants, enabling the removal of suspended solids, nutrients, and pathogens. These passive systems, closely resembling natural wetlands, rely on processes such as adsorption, precipitation, sedimentation, and filtration to improve water quality.

[caption id="attachment_25944" align="alignnone" width="1200"] Cell construction - Courtesy of MMB[/caption] Advantages for Dearne Reach

The ICW at Dearne Reach offers numerous advantages:

Water quality improvement: Effective removal of nutrients, heavy metals, pathogens, and organic pollutants. Carbon sequestration: Capturing carbon within plant biomass and soil, contributing to achieving net zero goals. Biodiversity enhancement: Providing habitats for birds and other wildlife, supporting ecological balance. Community benefits: Creating green spaces for public enjoyment and research opportunities. Versatility: Adapting to varying wastewater loads and flows, making it highly efficient at stormwater management. Low operational costs: Passive systems with minimal maintenance and no chemical requirements over decades, unlike conventional treatment plants. Plantings

At Dearne Reach, 52 different species of plants have been designed to sit in 13 adjacent cells in which over 350,000 plants adsorb nutrients from storm overflow discharges and wastewater flowing out of the Clayton West Wastewater Treatment Works.  These have been specifically selected for the treatment capacity, and alongside the enhancement of existing hedgerows across the site, has enabled a staggering 38% biodiversity net gain in terrestrial habitats.

[caption id="attachment_25945" align="alignnone" width="1200"] Liner installation - Courtesy of MMB[/caption] Variable stormwater discharges

The project introduced an ICW specifically designed to treat intermittent storm overflows. Unlike traditional ICWs, which are effective only with constant inflow, this innovative design can handle the variability and unpredictability of stormwater discharges. The wetland is divided into multiple cells, each optimised for maximum retention time and pollutant removal.

Advanced hydraulic controls and computational fluid dynamics (CFD) simulations were employed to model and optimise the flow through the wetland, ensuring effective treatment of fluctuating volumes and pollutant loads.

Pumping station & rising main

A new wetland pumping station has been designed to raise up to 350 l/s of flows from Clayton West WwTW to the ICW through a new rising main constructed using HDD trenchless methods. Once the water reaches the head of the wetlands, the entire system is passively flowing through two precast concrete distribution chamber structures and fourteen 1.4m wide cascades to transfer the water through each of the 13 cells.

Harnessing solar power

The innovative design harnesses solar power to operate a level sensor and flow meter chamber to successfully manage stormwater variability whilst achieving a passive system ICW with no additional power requirements. The introduction of the solar panels mean that the flow monitoring chamber could be installed to provide future quantity and quality monitoring data, which can be shared to support the evidence base of these emerging infrastructures.

As the largest ICW developed in the UK, its unique design and successful results will contribute to driving continuous innovation in nature-based solutions for storm management across the water industry. It stands as an excellent example of the power of collaboration between civil engineering and nature-based solutions to mitigate the impacts of climate change and promoting sustainable development.

[caption id="attachment_25941" align="alignnone" width="1200"] All cells constructed - Courtesy of MMB[/caption] Collaborative approach

To successfully design and build a wetland on the scale of Dearne Reach it was clear from the project outset that a collaborative design approach would be key to both a successful programme and commercial output. Therefore, collaboration between the design team, digital delivery team and geotechnical experts was fundamental. The challenges facing the site included, high shallow perched groundwater, sandy, gravelly clay requiring high degrees of compaction, and a requirement for over 13,000m3 of material for topsoil reuse. Alongside construction on a complex site within a coal mining legacy area, with archaeological potential and intersecting with a public right of way.

Dearne Reach ICW: Supply chain: key participants Principal designer & contractor: Mott MacDonald Bentley Outline design: Stantec UK Pressure testing: Ant Hire Groundworks: Lowthers Groundwater treatment: Siltbuster Group HDD rising main: Joseph Gallagher Ltd Liner suppliers: SIG Construction Accessories Precast structures: Craven Concrete Ltd Headwalls: Althon Ltd Treatment works package: HB Tunnelling Electrical package: Circle Control & Design Systems Ltd MCC installation: Technical Control Systems Ltd Communications instruments: Churchill Controls Ltd Wetland plant suppliers: Salix River and Wetland Services Grass & flower seed: Hurrells & Mclean Seeds Ltd Erosion protection: Geogrow Gate valves: Affco Flow Control (UK) Ltd Actuators: Glenfield Invicta Ltd Instrumentation: Marlec Instrumentation: IFM Electronic Ltd Flow meter: SIRIS Environmental Pipework: Aquaspira Ltd [caption id="attachment_25946" align="alignnone" width="1200"] Planting completed in all the cells - Courtesy of MMB[/caption] HDPE pipework & couplers: Westwood Pipelines Ltd HDPE pipework & couplers: Radius Systems DI pipework: George Green (Keighley) Ltd DI pipework: Electrosteel Castings (UK) Ltd DI pipework: UTS Engineering Ltd Metalwork: Fabtek Duct pits: Advanced Infrastructure Systems Pipe supports: Midland Fixings Ltd Drainage pipework: Wolseley UK ltd Drainage pipework: Myers Building Supplies Drainage pipework: Keyline Civils Specialist Ltd Pumps: Xylem Water Solutions Lifting gantry: Peter Cassidy (Leeds) Ltd Welfare cabins: Nixon Hire | Wernick Group Bolt-sets: BAPP Industrial Supplies Bolt-sets: VULCAN Industrial Fasteners RoadCem access roads: DNS Aggregates: Hague Plant ltd Concrete: Heidelberg Materials Plant hire: Lynch Plant Hire Plant hire: Grantham Industries Ltd Plant hire: Flannery Plant Hire (Oval) Ltd [caption id="attachment_25937" align="alignnone" width="1200"] Filling the first cells with water - Courtesy of MMB[/caption] Construction achievements

During construction, several notable achievements were made:

Groundwater management: As a result of high groundwater levels on the site, the system hydraulics were analysed, and cell height adjusted. This optimised the cut-fill balance and ensured no material import would be required to construct the embankments, ultimately preserving resources and reducing material waste whilst ensuring there would be no flotation risk

Bypass pipework reductions: Through the development of robust future access and maintenance plans, an opportunity was realised to eliminate unnecessary bypass pipework infrastructure. Initially, this had been proposed to allow each cell to be isolated for future maintenance. The removal of this pipework scope significantly reduced the carbon footprint and project costs.   

Sustainable lining solution: As the existing ground did not have a suitable impermeability to protect the underlying groundwater, the ICW had to be lined. To avoid the use of extensive plastic on site, a geosynthetic clay liner was used to create a self-sealing, resilient hydraulic barrier while minimising environmental impact.

Archaeological and geological integrity: The team ensured the coal mining legacy areas remained undisturbed, with archaeological trenching conducted site-wide to ensure any potential pre medieval features were not disturbed during construction.

RoadCem technology for sustainable access: Traditional concrete access roads were replaced with Roadcem soil stabilisation technology to reduce the required material import and associated carbon footprint with use of extensive artificial concrete.

Biodiversity commitment: 350,000 locally sourced plants were installed, arranged in seven planting zones, achieving a 38% biodiversity net gain in terrestrial habitats.

Public right of way enhancements: Social value was equally important to the project and the team collaborated with the local council to enhance the public right of way, improving accessibility with a wheelchair-friendly, 2m-wide footpath along the perimeter of the ICW, featuring timber fencing for optimal wetland viewing points to support community health and well-being.   

Carbon savings: The project has achieved a 60% reduction in embodied carbon and 40% reduction in operational carbon across its lifecycle – delivering a more environmentally friendly solution in comparison to the original grey infrastructure solution.

[caption id="attachment_25940" align="alignnone" width="1200"] Fully planted wetland - Courtesy of MMB[/caption] Innovative digital construction

From the outset, early collaboration with Mott MacDonald Bentley’s digital delivery team identified an opportunity to pilot the use of intelligent plant machinery, alongside a ‘Smart Construction Dashboard’ during the build.

Prior to mobilisation on site, the model and delivery programme was shared for upload into the Smart Construction/Earthbrain software. These platforms initially use Artificial Intelligence to generate an efficient delivery output, detailing size, type and number of machines required. They also generate a powerful earth shifting model, highlighting the most efficient distribution workflow for the cut/fill material to travel and be placed.

This was most useful to compare the tendered assumptions and check for any oversights in the planning phases. This approach improved accuracy, efficiency, and most importantly, improved health and safety standards on site. This marked a first-of-its-kind trial for deploying intelligent plant in the construction of a nature-based solution.

The site team reported significant benefits, particularly given the scale of the excavation, such as:

Model-driven excavation optimised material use, eliminating unnecessary cutting/filling and promoting a right-first-time methodology. Automated systems reduced manual surveying and minimised plant-people interaction, ensuring safer site operations. Precision excavation reduced material waste while moving 65,000m3 (117,000 tonnes) of soil, limiting reliance on imported fill. [caption id="attachment_25939" align="alignnone" width="1200"] Wetland plants developing - Courtesy of MMB[/caption] Successes & summary

The Dearne Reach ICW Project exemplifies sustainable development by delivering a low-carbon stormwater management solution. Leveraging natural processes such as sedimentation, filtration, and biological uptake, the wetland effectively removes pollutants and reduces the ammonia levels in stormwater in line with the salmonid fundamental intermittent standards. This enhances water quality and strengthens local biodiversity, aligning with global climate adaptation efforts.

The project’s innovative approach to managing stormwater discharges aligns with Yorkshire Water’s efforts to mitigate and adapt to the effects of climate change. It stands as an excellent example of the power of collaboration between civil engineering and nature-based solutions to mitigate the impacts of climate change and promoting sustainable development.

This first-of-its-kind trial has set a new benchmark for future wetland and nature-based solution projects across the water industry, with lessons learned shared to inspire continuous innovation in sustainable construction.

Everton Water Recycling Centre (WRC) is a small treatment works in Bedfordshire, serving around 200 homes and a population of roughly 600. Located downslope from Everton village (220 ft above sea level), the works benefits from a 14% gradient, allowing wastewater to flow to the site by gravity before being treated and discharged to the River Ivel. To meet the Environment Agency’s AMP7 requirements, Everton WRC needed to significantly reduce phosphorus in its discharge. Without action, the site would fail to comply with Environmental Permitting Regulations (EPR). Anglian Water was required to meet new consent limits of 1 mg/l phosphorus and 8,000 µg/l iron under the Water Industry National Environment Programme (WINEP). Solution

Anglian Water tasked its @one Alliance with identifying an effective and innovative solution to this issue. The conventional approach, iron dosing, would have needed major civil works, a new concrete base, modifications to the existing process, and an ongoing supply of iron chemicals. This would create ongoing costs, increased carbon emissions from deliveries, and higher operational complexity.

Instead, the team chose to challenge convention by developing Anglian Water’s first Integrated Constructed Treatment Wetland (ICTW) as a nature-based alternative. The final design created a three‑cell wetland covering 18,320m² (around 2.5 football pitches).

[caption id="attachment_28098" align="alignnone" width="1200"] Start of turf stripping - Courtesy of@one Alliance[/caption]

To build a wetland of this size, Anglian Water purchased the required land from a local farmer who owned the field downstream of the existing works. The existing outfall pipeline ran parallel to the farmer’s field and Tempsford Road, carrying the treated wastewater out towards the River Ivel. To feed the wetland, the team bypassed the start of that pipeline, diverting the water through the gravity-fed wetland before cutting back into the existing pipeline at the new wetland outfall location.

Planting

Over a six-month construction and planting period, the team excavated the three wetland cells and planted more than 110,000 native plants, including:

Emergent wetland plant species

Lesser pond sedge (Carex acuitiformus) Reed Sweet Grass (Glyceria maxima) Lesser reedmace (Typha angustifolia) Yellow flag (Iris pseudacorus)

Marginal wetland plant species

Water mint (Mentha aquatica) Purple loosestrife (Lythrum salicaria) Brooklime (Veronica beccabunga) Flowering rush (Butomus umbellatus) Gipsywort (Lycopus europaeus) Marsh cinquefoil (Potentilla palustris) Marsh marigold (Caltha palustris) Meadowsweet (Filipendula ulmaria) Water forget-me-not (Myosotis scorpioides) [caption id="attachment_28094" align="alignnone" width="1200"] View of site accommodation, Everton WRC, and the wetland site - Courtesy of@one Alliance[/caption] Challenges

Like many capital projects, the Everton Integrated Constructed Treatment Wetland faced several challenges, including:

Land acquisition & planning: Securing land and planning approval took longer than anticipated and fell largely outside the delivery team’s control, creating uncertainty in the programme. Seasonal working: To avoid winter working risks, construction was strategically rescheduled to start in April 2025, enabling safer and more predictable delivery during drier months. Stakeholder coordination: The scheme involved multiple parties landowners, local authorities, and environmental regulators, requiring strong communication and alignment throughout. First-of-its-kind risks: As Anglian Water’s first ICTW, the solution carried natural risks around design validation and achieving stringent phosphorus and iron limits without chemical dosing. International appeal

As the UK’s first ICTW, the project has drawn international attention. In November 2025, Anglian Water hosted officials from the Mexican Embassy and Government during a UK trade mission exploring innovative water management approaches. Grant Tuffs, Regional Engagement Manager, noted that the visit strengthened international collaboration and highlighted the value of nature‑based solutions in modern water infrastructure.

The wetland has also been visited throughout the earlier stages of the project by Richard Fuller, local Bedfordshire Conservative MP, showcasing the positive and widespread attention this project has received throughout its lifecycle.

[caption id="attachment_28091" align="alignnone" width="1200"] Preparing the wetland cells - Courtesy of@one Alliance[/caption] Everton Wetlands: Supply chain - key participants Project delivery: @one Alliance Principal contractor: Skanska Wetland designers: Binnies Wetland designers: VESI Environmental Ltd Flood risk assessment: SWECO Topography surveys: Randall Surveys LLP Archaeological mitigation work: Headland Archaeology Ground investigation work: AF Howland Associates Specialist wetland construction: William Morfoot Ltd Wetland plants & planting: Salix River and Wetland Services Landscape planting & ecological surveys: Greenwillows Associates Ltd Enabling civil works: DLO (@one Alliance Direct Labour) Drone surveys & video footage/stills: Dronesmart Global Site security & construction timelapse: Wireless CCTV Ltd Flow meter supplier: Metasphere Ltd Flow meter installation: Dodd Group OSM chamber: SIRUS Security fencing & gate: Burn Fencing Ltd

Because no new dosing plant was needed, the existing site infrastructure and power usage remained unchanged. The planning and land acquisition process took three years, reflecting the complexity of delivering a first‑of‑its‑kind solution. This allowed the team to develop a robust, repeatable design for future wetlands planned across AMP8.

[caption id="attachment_28095" align="alignnone" width="1200"] Wetland cells prior to planting - Courtesy of@one Alliance[/caption] Successes

The Everton Integrated Constructed Treatment Wetland Project eliminated the need for chemical dosing, reducing lorry movements, operational carbon, and long‑term chemical costs. A deeper pond area was also created to encourage biodiversity and support local wildlife.

The Everton Wetland was completed in October 2025. With planting now established, full growth and system maturity are expected by Spring 2027. The plants have an indefinite lifespan but is likely to be between 30 and 50 years or more.

Overall, the project achieved an 84% reduction in carbon emissions, cutting the carbon footprint from 654 tCo2e to 104 tCo2e, largely due to balanced cut‑and‑fill earthworks that avoided imports and exports and the removal of 99% of anticipated concrete use.

[caption id="attachment_28097" align="alignnone" width="1200"] Wetland plants - Courtesy of@one Alliance[/caption] Conclusion

The Everton Wetland Project demonstrates how nature-based design can deliver regulatory compliance while providing long-term environmental, operational, and carbon benefits. By replacing chemical dosing with an ICTW, Anglian Water has reduced costs, cut emissions, increased biodiversity, and created a blueprint for future schemes.

As part of the £37m wetland programme, the lessons from the Everton Integrated Constructed Treatment Wetland Project will shape the next generation of wetlands to be delivered across AMP8. This project represents a significant milestone in the UK water industry’s shift toward sustainable, resilient infrastructure.

Located near New Inn, South Wales, this innovative nature-based solution (NbS) project addresses the water quality impact from a storm overflow (SO) discharging into the Afon Lwyd during wet weather. Water quality modelling classified the existing high spilling asset as having a ‘Severe Impact’ on the river which under the Storm Overflow Assessment Framework (SOAF), prompted investigation, optioneering and construction of the most cost-effective solution to deliver a ‘No Impact’ outcome. Using a multi capitals assessment, the team evaluated cost, carbon and long term value to both nature and society. This showed that prioritising a nature-based solution delivered substantial a cost saving (£43m) and carbon savings (half the embodied carbon) against its grey equivalent solution, a 33,500m3 storage tank, alongside wider community and environmental benefits. Root cause and optioneering stage

During the optioneering stage, a range of interventions were assessed to address the storm overflow impact, including catchment‑scale rainfall disconnection, increased pass‑forward flow, nature‑based treatment and conventional storage. Catchment disconnection was discounted due to the high levels of customer disruption required, while increasing pass‑forward flow was not feasible due to downstream hydraulic constraints. Given the overflow’s location adjacent to open land by the river, a nature‑based solution was identified as the most effective and deliverable option.

[caption id="attachment_29039" align="alignnone" width="1200"] The field pre-construction used for occasional grazing, with the existing storm overflow situated within the trees to the right - Courtesy of Arup[/caption]

A two-stage approach was chosen to maximise success, with an aerated reed bed providing initial intensive solids capture followed by two Integrated Constructed Wetland (ICWs) in series, providing effluent polishing and an opportunity for the industry to research wetland treatment in this application.

The favourable topography enabled a gravity system, eliminating the need for lifting flows and in turn, reducing operational energy demands. The field’s proximity to New Inn’s residents also allowed for place-making features for the local community, such as footpaths, an outdoor classroom and natural play areas, enhancing community engagement and educational opportunities.

The indirect monetary value of these wider benefits was captured in the decision-making stage via the use of CIRIA’s B£ST estimation tool, which estimated £12m in realised benefits over the next 40 years across social, natural and other capitals; something none of the grey solutions offered.

[caption id="attachment_28938" align="alignnone" width="1200"] Site layout - Courtesy of Arup[/caption] Design stage: New compound

The existing storm overflow (SO) was located amongst trees on the edge of the field. The incoming pipe laid in the eastern corner of the field meant the SO could be relocated into a new compound, which will contain the following chambers and plant:

Screening chamber: The screening chamber houses an orifice flow control and a new mechanical screen that removes solids from excess flows. Only flows above the permitted pass‑forward rate are diverted to the reed bed, ensuring that the treatment process receives appropriate, pre‑screened volumes. Bypass chamber: This chamber is designed to divert the highest flows from the catchment before they enter the nature‑based solution. The flow threshold is set so that around 95% of the total discharge volume still passes through the NbS, with the bypass only operating during the most dilute, peak‑flow conditions. MCC kiosk: New kiosk to house the motor control centre. Aeration blower kiosk: An acoustically insulated kiosk to house the blowers for the aerated reed bed.

Design for Manufacture and Assembly principles were adopted to several elements of the compound. The screening and bypass chamber were fabricated off site by FP McCann Ltd, reducing the need to cast these chambers in situ.

Both the kiosks were prefabricated off-site by Morgan Marine Ltd to save time and reduce on-site activities in the construction phase.

[caption id="attachment_28921" align="alignnone" width="1200"] The new compound (March 2025) - Courtesy of Welsh Water[/caption] Design stage: Reed bed & integrated constructed wetlands

The design team carried out a catchment Flow & Load Survey to ensure a better understanding of the design parameters required to achieve the ‘No Impact’ outcome. The survey gave insight into the challenges around pollutant loads in intermittent discharges, with varying concentrations of biochemical oxygen demand (BOD) and ammonia found in the excess diluted sewage; especially the difference between accommodating the ‘first flush concentration’ and weaker dilutions as a storm event continued.

Working collaboratively with the reed bed and ICW suppliers early in this stage, increased confidence in achieving the necessary pollutant removal in the final effluent.

A Flood Consequence Assessment (FCA) was completed as part of the planning application and the findings required the reed bed and wetlands to be moved further away from the river, reducing the size of the originally allocated footprint. The revised layout however, still provided sufficient treatment area (3,000m2 for the reed bed and a combined ICW treatment area of 2,400m2) and created additional space for the public to enjoy.

Planning & stakeholder engagement

The planning application was critical to the success of this project, which was well received by local councillors and relevant bodies, in part, due to the extensive up-front work done by Arup’s planning team. Arup specialist teams carried out predictive odour and noise modelling of the solution to address concerns raised by the planning authority. The project team also engaged extensively with the local community through both in-person and online events, ensuring the design met local needs and preferences.

To align with the Sustainable Approval Body (SAB) requirements as part of planning approval, the design team implemented sustainable drainage features across the site. The maintenance track and vehicle areas in the compound were constructed from permeable TruckCell™ paving, made from recycled plastic, whilst vegetated swales and depressions were incorporated alongside the impermeable access track and footpaths. This reinforced the project’s low‑carbon and sustainable design ethos.

[caption id="attachment_28924" align="alignnone" width="1200"] Maintenance track constructed out of TruckCellTM - Courtesy of Arup[/caption] Pont-y-felin Lane: Supply chain - key participants Main designer/contractor: Morgan Sindall Infrastructure Lead designer & planning team: Arup Reed bed: Natural Wastewater Solutions (NWS) Integrated constructed wetland: Salix River and Wetland Services Vesi Environmental Ltd Aeration blowers: AERZEN Machines Precast screening & bypass chambers: FP McCann Ltd Chamber covers: Steelway Brickhouse Mechanical screens: Huber Technology Mechanical installation: Industrial Pipework Services MCC: Lloyd Morris Electrical Ltd MCC kiosk: Morgan Marine Ltd TruckCell™ paving: ABG Geosynthetics Construction stage

Construction started in January 2024, with Morgan Sindall Infrastructure mobilising to bring the nature-based solution system online before the regulatory deadline of 31 March 2025. The team navigated challenges including invasive species within the compound area and persistent groundwater during the large excavations, requiring an extensive dewatering activity (under approved Abstraction Licences).

Working with the sub-contractors, Natural Wastewater Solutions (NWS) for the reed bed, and Salix River and Wetland Services and Vesi Environmental Ltd for the integrated constructed wetland, 33,904 tonnes of soil were removed and the ground re-profiled. 30,000 tonnes was re-used off site, whilst 3,000 tonnes was recycled and re-used on site, with the final 904 tonnes taken to landfill, due to the presence of Japanese knotweed.

[caption id="attachment_29040" align="alignnone" width="1200"] Site drone photos throughout construction (January 2024 - June 2025) - Courtesy of Welsh Water[/caption]

Due to the impermeable nature of the soil, the reed bed and constructed wetland both required under-draining to minimise the impact on the groundwater table. Once the under-drains were installed, the basins were constructed, which included the following:

12,000 plants throughout the three basins, including: Phragmites planted for the reed bed and; Lesser pond sedge, reed sweet grass, lesser reedmace and water mint for the ICWs. 6,100m2 of liner across the three basins. 17,500m of aerated pipeline installed. 3,710 tonnes of stone.

The site team pushed to see the first flows through the system just 12-months later, ahead of the 31 March deadline and handled the heavy rainfall from Storm Eowyn on 24 January without any issue.

Monitoring

A robust sampling regime is currently underway to understand the performance of the individual stages and final effluent from the nature-based solution. This will inform future permitting of these types of solutions in cooperation with the environmental regulator, Natural Resources Wales (NRW).

The initial sampling results are promising, with significant reductions in BOD, ammonia, total suspended solids (TSS) and phosphorus in the final effluent. River water quality sampling upstream and downstream of the outfall is also being carried out to understand the impact of the scheme on the Afon Lwyd.

[caption id="attachment_28926" align="alignnone" width="1200"] Integrated constructed wetlands (October 2025) - Courtesy of Arup[/caption] Research

Welsh Water is participating in the Chemical Investigation Programme (2025–2030) with UKWIR, where samples from the wetlands are currently being used to help understand bio-accumulation of emerging substances such as pharmaceuticals in intermittent discharges.

Conclusion

With the site due to open to the public soon, Pont-y-felin Lane exemplifies a paradigm shift in storm overflow management, demonstrating how nature-based solutions can deliver technical excellence, environmental restoration, and community enrichment, all while setting a precedent for low-carbon infrastructure in the water sector. The forward‑thinking optioneering, combined with the client’s commitment to selecting a nature-based solution, over traditional ‘grey’ options, has resulted in a scheme that proves natural solutions can deliver more sustainable outcomes, for less.

Thurleigh Water Recycling Centre (WRC) is located just outside the village of Thurleigh in North Bedfordshire, around six miles from Bedford. The site plays a vital role in Anglian Water’s water recycling network, helping protect local waterways and maintaining environmental compliance. This project forms part of Anglian Water’s Water Industry National Environment Programme (WINEP), a national initiative focused on improving water quality and ecological health. WINEP supports the UK Government’s Water Framework Directive, which requires water companies to achieve good ecological status in rivers and water bodies. Problem To meet the Water Framework Directive, Thurleigh WRC needed to significantly reduce phosphorus levels in its final effluent. Excess phosphorus can cause algal blooms, oxygen depletion and damage to aquatic ecosystems. Thurleigh’s consent limit was set at a stringent 0.5 mg/l - beyond what existing assets could consistently achieve. Failure to meet this requirement risked breaching Anglian Water’s AMP7 commitments, potentially leading to regulatory penalties and reputational impact. Environmentally, reducing phosphorus was essential for improving river quality and supporting biodiversity. Solution Anglian Water tasked the @one Alliance with delivering the scheme. The team adopted an innovative £3.2m biological algae treatment system (I-Phyc) in place of traditional chemical dosing. The I‑Phyc system uses algae’s natural ability to absorb nutrients. Key components included: 11 process tanks and eight conditioning tanks with LED lamps and automated wipers. A new cloth filter for efficient algae harvesting. An air‑mixing system with dual blowers to maintain optimal oxygen levels. A new PLC‑controlled kiosk for real-time monitoring. Dual-channel phosphate monitors for accurate compliance tracking. Feed and backwash pumping stations. A DNO power upgrade for resilient electrical supply. This integrated solution not only meets regulatory targets but also sets a new benchmark for sustainable, low‑carbon water treatment; reflecting Anglian Water’s values of Always Exploring, Do the Right Thing and Build Trust. [caption id="attachment_28297" align="alignnone" width="1200"] The Thurleigh WRC biological algae treatment system from Industrial Phycology Ltd - Courtesy of @one Alliance[/caption] Thurleigh WRC: Supply chain - key participants Successful delivery relied on strong collaboration across the supply chain. The combined expertise of the project partners ensured high-quality design, compliance, and installation of a first-of-its-kind system: Project delivery: @one Alliance Principal contractor: Barhale MEICA & civils design: RSE (Ross-shire Engineering) Archaeology survey: Dalcour Maclaren Ltd Ecological survey: Greenwillows Associates Ltd I-Phyc algal reactor design & supply: Industrial Phycology Ltd Site electrical & mechanical delivery: RSE (Ross-shire Engineering) I-Phyc reactor electrical & mechanical delivery: Advanced Process Air blowers: Aerzen Machines MCC: Paktronic Engineering Co. Ltd Telemetry equipment: Dodd Group (Eastern) Ltd Safety shower: Hughes Safety Showers Ltd Civils works: DLO (@one Alliance Direct Labour) Challenges Introducing Anglian Water’s first algae-based phosphorus removal system brought several challenges: Supplier integration: Working with new technology required onboarding suppliers unfamiliar with @one Alliance processes. Close collaboration ensured alignment with standards and successful delivery. Operational transition: Adopting a biological alternative to chemical dosing required training, operational changes and robust risk management to ensure a smooth handover. Archaeological delays: Archaeological investigations during enabling works caused delays, but were essential to protect local heritage and meet statutory obligations. Despite these challenges, the project team maintained strong collaboration and proactive planning to keep the programme on track. [caption id="attachment_28298" align="alignnone" width="1200"] Completed biological algae treatment system - Courtesy of @one Alliance[/caption] Carbon savings Construction generated 205 tCO2e of capital carbon. However, the I‑Phyc system absorbs 46 tCO2e annually, meaning the project will offset its carbon footprint within four years. Further operational carbon savings include: The need for chemical transport and storage is removed. Lower sludge handling and disposal. Once fully optimised, the algae will absorb carbon equivalent to 2,190 trees per year. Conclusion The Thurleigh WRC I-Phyc Phosphorus Removal Project showcases how the @one Alliance and Anglian Water collaborate with the supply chain to bring new sustainable technologies to site. As Anglian Water’s first chemical‑free, algae‑based phosphorus removal system, Thurleigh provides a scalable model for future AMP8 schemes; achieving regulatory compliance while reducing carbon and operational costs.