Sustainable removal of phosphorus investigated

Wessex Water has begun a project to remove phosphorus from waste water in a sustainable way.

The method has been developed by scientists in Somerset who have modified traditional reed beds to conduct the experiment in phosphorus removal.

The project is taking place at Somerton sewage treatment works and aims to prove the unique reed beds are a sustainable solution to preventing phosphorus entering water courses where it causes eutrophication which can seriously harm aquatic life.

Currently the company uses traditional chemical dosing to remove phosphorus from waste water and are looking at ways to make this process more environmentally sustainable.

Wessex Water's environmental regulation manager, Ruth Barden said: "We see chemical dosing as fundamentally unsustainable as iron used during the process has to be sourced from South America or Europe.

"The process has a high carbon footprint, requires a lot of energy to complete, and increases sludge volumes by up to 20 per cent.

"However we believe these unique reed beds could provide a long term solution to one of the biggest issues in watercourses. They typically contain waste materials which can be easily obtained and require no electricity to run effectively".

Six reed beds have been developed for the trial each containing reeds growing in different media which are being tested to see which removes phosphorus most effectively.

The six materials involved in the trial are limestone chips, locally sourced from Cheddar in Somerset, steel slag - a waste product from the steel industry, crushed and standard blast furnace slag media, Xylit sourced from Germany, Bauxsol and a gravel bed to act as a control.

The reed beds are all around 75 cm deep and contain several sample points so scientists can test how much phosphorus has been removed at different stages throughout the beds.

Over next three years the project will be used to determine the most effective media and the optimum level of phosphorus it can remove.

The study will look into the optimum maintenance regime and flow conditions and the cost and carbon footprint of each of the beds.

It is hoped that the half a million pound project will help the company meet the new Water Framework Directive which comes into force in 2015 and could potentially require more phosphorus removal facilities to be installed more widely at sewage treatment works. Alison Brown



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