Constructed Wetland Association

Resources

CWA Resources

UK & Ireland constructed treatment wetlands map

A compilation of treatment wetlands in the UK and Ireland, based on contributions from site owners and wetland designers. The map lets you filter by wetland type whilst also displaying key information including what it treats, how big it is and the dry weather flow.

Design Guidance for sewage application

Design guidance on the use of vertical flow wetlands following a septic tank, for small sewage discharges. The information is based on UK systems that can achieve 10:10:5 for BOD, solids and ammonia, on a 95%ile basis.

Treatment wetlands in the UK: Case studies of an established biological treatment technology

This CWA report summarises the use of treatment wetlands for biological wastewater treatment in the UK. It contains a simplified terminology diagram, showing alternative names for different wetland types (e.g., "reedbeds" in the UK, subsurface flow wetlands in global literature), and 17 case studies from the UK for secondary, tertiary, high flows and sewer overflow applications.

25 year anniversary CWA presentation: Four decades of UK treatment wetlands

In 2025, the CWA did a number of dissemination activities to celebrate 25 years since its foundation. These are the slides presented at a joint CWA & CIWEM webinar in October 2025, summarising what we've learnt over the years from research and implementation of the technology at scale.

Design resources

Title	Authors	Link
Biological Wastewater Treatment Series, Vol 7: Treatment Wetlands	Dotro, G., Langergraber, G., Molle, P., Nivala, J., Puigagut, J., Stein, O., von Sperling, M. (2017)	An open access (free to download) textbook summarising the design principles from Kadlec and Wallace (2009), aimed at undergraduate engineering students and/or practitioners without a background in treatment wetlands. The book has simple explanations of the underlying pollutant removal processes, the four main wetland types (horizontal, vertical, surface flow and French systems), and the design approaches typically used for each. It has worked out examples as well as information on emerging applications including intensified systems and floating wetlands.
Scientific and Technology Report, Wetland Technology: Practical Information on the Design and Application of Treatment Wetlands	Langergraber, G., Dotro, G., Nivala, J., Rizzo, A., Stein, O. (2020)	An open access (Free to download) report, summarising the latest knowledge and experience with different treatment wetland applications. It also contains a dedicated chapter on Common Pitfalls in wetland design and applications, and minimum information that needs to be included in any wetland reports to enable other professionals to interpret the data presented.
Treatment Wetlands, 2nd edition	Kadlec, R. and Wallace, S. (2009)	The most comprehensive book on treatment wetland technology. It includes detailed explanations of pollutant cycling processes, how they interact with each other and how to design for specific treatment objectives. Its main contribution is the development of the pKC* model - a combined hydraulics and microbial removal model derived based on two decades of wetland experience and monitoring across the globe. It contains tabulated model parameters based on specific applications as well as temperature correction factors and model uncertainty estimations for a variety of pollutants and wetland designs.
Treatment Marshes for Runoff and Polishing	Kadlec, R. (2019)	The last book written by Robert Kadlec, specifically focusing on surface flow systems. The books builds from Kadlec and Wallace (2009) and expands it with an additional decade of monitoring data and design experience, summarising best available knowledge for surface flow wetlands for polishing applications (runoff, tertiary sewage treatment).