EDITOR’S CHOICE
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A major collaborative study into alternative approaches to phosphorus removal at rural wastewater treatment works has delivered promising results, with one new method already in use by a UK water company.
The ALT-P project was led by United Utilities, with project partners Southern Water, Wessex Water, University of Portsmouth, Power & Water, Kolina, Hydro Industries and Evergreen. Spring Innovation was the knowledge-sharing partner.
Due for completion in November 2025, ALT-P aims to provide the water industry with a holistic view of the cost, capability, operation, maintenance and carbon impact of sustainable phosphorus removal approaches. The project’s goal is to help companies reduce reliance on chemicals, in particular metal- based coagulants such as ferric sulphate.
After receiving funding through Ofwat’s Water Breakthrough Challenge in 2021, researchers focused on three alternative phosphorus removal methods – electrocoagulation, natural coagulation and reactive media. A range of different technologies from various providers were explored in lab tests and onsite trials.
Findings from each study were shared during United Utilities’ ALT-P project day on 17 September 2024 and have also been published on the Spring knowledge-sharing platform. In summary, these are the findings:
Electrocoagulation
The electrocoagulation process uses electrical reactions to bind particles together. Four electrocoagulation systems were trialled over 14 months at United Utilities’ Woolton wastewater treatment works (WwTW) in Liverpool.
The trials showed that electrocoagulation effectively removed phosphorus without requiring liquid chemical dosing. Two technologies showed particular promise when compared to chemical dosing. The benefits of using electrocoagulation included a reduced impact on alkalinity, removal of health and
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safety risks associated with chemical storage and a potential to reduce carbon impact.
Natural coagulants
The use of natural bio-based coagulants is predicted to become more widespread in the coming years, as technology providers discover more natural materials that can offer sustainable phosphorus removal. Extensive laboratory research into extracts of materials including plants, algae and tree bark was undertaken by ALT-P researchers.
A six-month trial followed in a test lane at Woolton WwTW to compare the standard solution, ferric sulphate dosing, with natural coagulants. The research found that there is a viable method of phosphorus removal using natural coagulants, dosed in combination with ferric sulphate.
In a key outcome for the project, United Utilities has already started using natural coagulants at sites in Cheshire as part of their AMP7 investment programme.
Reactive media Reactive media are a range of adsorptive materials which
The ALT-P project has achieved fantastic outcomes, which can
directly support the water sector’s drive to embed more sustainable treatment processes.“
Phosphorus project finds
alternatives to chemical treatment Promising findings shared across UK water sector
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