Water utilities are currently at different stages of progressing AMP7 feasibility designs of treatment wetlands (TWs) for phosphorus (P) removal applications. The regulatory agencies are open to supporting TW implementation, considering the long list of additional co-benefits they can deliver in terms of natural and social capital.

Whilst there are a few flagship schemes, the majority of the experience with passive phosphorus removal with TWs is being extrapolated based on schemes in Ireland, where the technology is implemented as “integrated constructed wetlands” (ICWs). However, unresolved concerns include uncertainties on TW effluent water quality and quantity fluctuations, seasonal variations, and lowest effluent concentrations achievable for solids and P.

This project (stage I) aims to deliver a summary of the available evidence base to act as common ground for industry-wide evaluation of TWs for P removal. Future experimental work (stage II) to address data gaps and testing of risk management strategies will be re-assessed once a better understanding of the feasibility of TW for P removal within the UK water industry is established.

  • Dates2021
  • SponsorAnglian Water, Dwr Cymru Welsh Water, Environment Agency, Irish Water, Northumbrian Water, Severn Trent Water, South West Water, Southern Water, Thames Water, United Utilities, Wessex Water, Yorkshire Water
  • Funded£56,000

Impact and findings

In total, 85 wetland system datasets were collected for this project, where 59 systems from practitioners have extensive P data (i.e. outlet P concentration over two years at a minimum), and 26 systems from published literature have informative data (e.g. average inlet/outlet P concentration). The systems are from 18 countries, where 16 systems come from the UK and Ireland. The size of the systems ranges from 0.0025 to 482 ha.

The oldest and newest systems were built in 1978 and 2020, respectively. The quantity and quality of the dataset are comparable to published review studies, with this work containing the largest sewage treatment SF wetlands assessment.

This project will deliver 1) an open-access Position Paper, where the raw data will be available online and benefit academic research and industry implementation, 2) an executive summary video to summarise the key messages, and 3) an infographic to present the main findings. The documents will be updated on the website shortly.