Integrated constructed wetlands (ICWs) for the removal of micropollutants and climate change control

Water Quality, Groundwater and Land Contamination in the Environment Agency’s Environment and Business Directorate are implementing a delivery plan to support the work to mitigate against and adapt to climate change. One of the actions within the delivery plan is considering the use and promotion of integrated constructed wetlands (ICW). ICWs, also named ‘surface flow treatment wetlands’, have been widely applied around the world in treating sewage and other sources of wastewater as well as delivering multi-benefits as a nature-based solution. However, more evidence is needed to inform the sound management of chemicals and decrease the risk of pollution in a changing climate.

Therefore, To better identify opportunities and propose a framework for robust design and implementation of the technology in a changing world, the Environment Agency has commissioned this work to develop a concise literature review to summarise the evidence base for the use of ICWs for sewage treatment beyond nutrient removal, which includes 1) the removal of Environmental quality standards (EQS) defined priority substances and other micropollutants, and 2) the interaction of climate change and ICW functions.

The result of the project indicates that ICWs have the potential to be an effective barrier for micropollutants entering into natural waters. However, the current evidence base provides a partial picture due to the relatively low number of studies. No quantitative study is available to understand the impacts of climate change on micropollutants removal in ICWs, although it is anticipated that removal will be enhanced due to the impacts of climate change. In order to provide an updated benchmark of using ICWs for micropollutants removal, additional research is required to focus on the un-investigated compounds and more field-scale long-term investigations are needed for the studied compounds.