The Broad Oak development in Canterbury, comprising of 456 new homes, presented a unique challenge: meeting stringent Nutrient Net Neutrality (NNN) regulations for wastewater treatment while managing highly variable water inflow. Variable water levels can compromise the effectiveness of traditional constructed wetlands, bypassing the treatment process.

At Broad Oak, the unpredictable nature of stormwater runoff combined with the consistent, but separate, flow from the treatment plant required a integrated treatment model as well as a dynamic solution

The project involved a collaboration between Biomatrix, RSE, Barratt Homes, David Wilson Homes, Kingsheath Construction and ICOSA with process input from WET Systems, Mott MacDonald and NNN oversight from Marian Cameron Consultants. The solution involved an innovative hybrid constructed wetland system, incorporating Floating Ecosystems which can adapt to variable water levels to maintain wetland treatment functionality.

The process involved a series of three interlinked constructed wetland basins. Over 2300 native aquatic plants were carefully selected and planted, acting as a highly effective natural bio-filter.

The Broad Oak project offers a useful case study, showcasing how innovative wetland design can effectively address the challenges of variable water flows and limited space. It is an example of integrating engineering and ecology within modern development, to achieve both effective wastewater treatment and positive ecological impact.