Yorkshire Water planning £60m investment to improve wastewater treatment in Ilkley

Yorkshire Water has announced plans to invest in the region of £60m at its wastewater treatment works and storm overflows in Ilkley to reduce storm discharges to the river Wharfe, improving water quality at the designated bathing water in the town. 

The project, which is subject to regulator and local authority planning approval, will feature: 

• increased storage at storm overflows within 5km upstream of the bathing water 
• additional upgrades including 15,000m3 of storage and a new 4,000m2 aerated rush bed within the grounds of Ilkley treatment works to more than double its wastewater treatment capacity 
• a new tunnel under the river Wharfe to transport treated wastewater to a new 19,000m2 integrated constructed wetland (ICW) across the river from the existing treatment works 

The work will reduce discharges from each storm overflow within 5km upstream of the bathing water and Ilkley wastewater treatment works to one discharge to the river Wharfe per bathing water season (15 May-30 September) and no more than 10 discharges per year on average. 

Nicola Shaw, CEO of Yorkshire Water, said: “We have made significant investments in our network in the Ilkley catchment in recent years to improve water quality as we work to improve the bathing water classification. If approved, this project will take our total investment in infrastructure in the area to more than £75m and will be a step change in how we manage wastewater in Ilkley. 

“Once upgrades to the network are completed, the treatment works and our new wetland, which will be completed in 2026, will meet Government targets of one discharge per bathing water season nine years ahead of the 2035 deadline. 

“This project does not signal the end of investment in the area, and we will continue to look at ways of improving our operations and the way we manage wastewater to reduce discharges where possible. While our investment will reduce our impact on water quality in the Wharfe, it is important that other sources of pollution, such as agriculture, industry and highways drainage are investigated by the appropriate partners and their impacts on the river reduced if bathing water classifications are to be improved.” 

The work continues to build on the increased sewer capacity delivered this year to reduce discharges from Rivadale View storm overflow and includes additional storage being constructed within the sewer network in the catchment to reduce discharges from Low Mill Lane storm overflow, Addingham sewage pumping station storm overflow, Bridge Lane storm overflow and Ilkley Middleton sewage pumping station storm overflow upstream of the bathing water to one discharge  per bathing season and no more than 10 discharges per year on average.   

Once completed, the additional storage will hold excess wastewater flows during periods of prolonged and heavy rainfall, reducing discharges from the overflows into the Wharfe. The stored storm water will then be released to Ilkley wastewater treatment works once the rainfall event has passed and incoming flows have reduced. 

Upgrades to the treatment works include new primary settlement tanks and a 4,000m2 aerated rush bed. The rush bed will act as a natural solution for the secondary treatment of sewage flows during periods of heavy or prolonged rainfall, or when stored storm water is returned to the usual treatment process. The specially grown rushes are a sustainable and environmentally friendly way of removing pollutants and is resilient under a wide range of flow and loads.  

The upgrades will more than double the wastewater treatment capacity of the works, dramatically reducing the frequency and duration of storm overflows into the river Wharfe around the bathing water and improving water quality. 

Once wastewater has been through the upgraded Ilkley wastewater treatment works, it will be transferred across the river Wharfe via a newly constructed sewer, to the integrated constructed wetland for tertiary treatment. It will pass through six interconnected ponds which will provide further treatment through a wide range of carefully selected wetland plants and without the need for chemicals or powered equipment, before it is returned to the environment from a new outfall. 

The wetland will provide a biodiversity net gain and will be accessible to the public. 

If approved by Ofwat and local authority planning, work to increase storage at the storm overflows is expected to begin in summer 2024, with the treatment works and wetland projects delivered in 2026, nine years ahead of Government targets of one spill per year per bathing water season by 2035 

Yorkshire Water, alongside its contractor Groundworks, is also planning to install 150 leaky water butts in the gardens of properties in selected areas of Ilkley, Ben Rhydding and Addingham as part of its smart networks project. Flow monitors within the sewers have helped the utility identify properties in the catchment where slowing the flow of surface water into the combined sewer network would significantly reduce discharges into the Wharfe. 

Yorkshire Water held a drop-in session for local customers at the Ilkley Playhouse to outline the plans.  

The investment is the latest investment in the wastewater networks in Ilkley, following: 

• A new £15m sewer under the A65 to reduce discharges to the Wharfe 
• An extension of the tunnel to reduce discharges from Rivadale storm overflow to one per year per bathing water season in 2026 
• The addition of UV irradiation treatment at the Draughton, Grassington and Beamsley wastewater treatment works to improve water quality 
• Upgrades to screens at Rivadale storm overflow 
• A £1.4m investment at Ben Rhydding wastewater treatment works and Wyvil Crescent storm overflow to reduce discharges to the Wharfe