Thames Water has been working in collaboration with Cranfield University on a project  to develop a more sustainable and non-chemical treatment process using an innovative reed bed treatment for the removal of phosphorus from treated effluent.

Tighter environmental standards under the Urban Waste Water Treatment Directive will see many small sites have a P consent for the first time – meaning that Thames Water will have to remove phosphorus (P) from its treated effluent at more than 60 of its small sewage treatment works between now and 2025.

The smaller sites are usually unmanned, with limited access for tankers, limited power and limited potable water supply for emergency showers. This means that the conventional solution for P removal of chemical dosing followed by a filtration step may not be the most suitable or most sustainable solution.

The project, which is being funded by Thames Water’s eight2O alliance partners, uses P-reactive media instead of conventional gravel - two different media (basic oxygen furnace steel slag and apatite)are currently being tested at four full-scale reed beds at Easthampstead Park STW.

Thames Water is also looking at solutions to reuse the spent media, which are expected to last for around seven years before they need replacement,  as fertiliser to close the phosphorus loop.

Eight2O technical lead Narinder Sunner said the approach could have environmental benefits making it easier to manage compliance risk as it eliminates the possibility of overdosing chemicals.”

The work is now being accelerated by a steering group of five water companies that have asked to collaborate in the trials.

Dr Nick Mills, Thames Water’s head of innovation, commented:

“My team’s common objective is to save a substantial amount of TotEx in AMP6 and to demonstrate how to halve the cost of wastewater operation in the future.”