Broadwindsor STW - South West Water

Design and delivery of a new Bio-P final effluent polishing treatment plant to remove phosphorus without chemical aid. (February 2021)


Broadwindsor is a village in West Dorset, which is renowned for Lewesdon Hill (the highest point in Dorset), Pilsdon Pen (Iron Age Hill Fort) and the 13th century church, in which Thomas Fuller preached. Broadwindsor is two miles west of Beaminster and seven miles north of Bridport. The village square is much photographed, especially King Charles Cottage, the place where King Charles II is reputed to have stayed the night in 1651 after his flight from the battle of Worcester. The local village hall, known as Comrades Hall, is an active centre for all the members of the community, which hosts a variety of clubs and meetings as well as regular visits from Artsreach and Dorset Moviola. Dorothy Wordsworth wrote of Broadwindsor as being “the place dearest to my recollection in the whole surface of the island”.


Broadwindsor STW caters for a population equivalent of 480 and the project is the first to be undertaken by SWW in the AMP7 period, designed to remove Phosphorus from the tertiary waste stream from the outfall of the works without the use of chemicals.

The project has been jointly delivered for South West Water by I-Phyc and South West Water’s framework partner Nomenca.

Existing Works

The existing works treatment process has a screen in the inlet, a primary settlement tank followed by a stone percolating filter plus settlement tanks for carbonaceous removal, which is followed by a plastic percolating filter and settlement tanks to achieve nitrification.  Currently, the tertiary effluent is polished by a reed bed.

The outfall discharges into the Drimpton Stream part of the river Axe catchment. The lower reaches of the River Axe catchment (22.94Ha) have been designated as a Special Area of Conservation (SAC) due to some of its flora and fauna. Plus 13km of the River Axe (full length 35km) between the Blackwater River and Colyford Bridge are also designated as a Site of Special Scientific Interest (SSSI) for supporting exceptionally diverse aquatic and marginal flora.

Process Design

The process has been designed to operate and perform to the following effluent discharge outputs:

Scope of Supply

Scope of Equipment Supply

The I-Phyc Algal Biological Reactor is a novel P removal technology that does not use chemicals and is designed to remove P in the FE below/equal 0.5 mg/l.

The unit supplied by I-Phyc is factory built off site.