Plans that will improve river water quality at a designated bathing site in the UK town of Ilkley include an aerated bed of rushes and a wastewater treatment plant upgrade.

Yorkshire Water says some £60 million would be invested in the town's wastewater treatment works and storm overflows to reduce storm discharges to the River Wharfe. The multi-project plan is subject approval from the regulator and local authority, and would feature increased storage at storm overflows upstream of the bathing waters.

Further measures include storage for 15,000m3 of wastewater and stormwater, and a 4,000m2 aerated rush bed, which would more than double capacity at Ilkley wastewater treatment works. A new tunnel would be built under the Wharfe to transport treated wastewater to a new 19,000 m2 integrated constructed wetland.

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, with no more than 10 discharges per year on average.

Nicola Shaw, chief executive 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 builds on the increased sewer capacity delivered this year. 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 stormwater 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 waters and improving water quality.

Once wastewater has been processed at the upgraded Ilkley wastewater treatment works, it will be transferred beneath the river Wharfe via a newly constructed sewer, to the specially constructed wetland, where it will undergo a third treatment stage, passing through six interconnected ponds

A range of carefully selected and managed wetland plants will naturally remove pollutants, without the need for chemicals or powered equipment, before it is returned to the environment from a new outfall. The wetland will provide a boost to nature and wildlife, and will be accessible to the public.

If approved, 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 UK 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 sewer network, which also carries stormwater, would significantly reduce discharges into the Wharfe.