Constructed wetlands are human-made wastewater treatment systems which are gaining in popularity due to their acceptance as being economical, green, and efficient and which require relatively little maintenance and monitoring compared with the more conventional alternative. They have several advantages in comparison with the latter.

Requiring lower operation and maintenance costs

They are a sustainable, green system requiring lower operation and maintenance costs. In addition, the vegetation in constructed wetlands assists in many important pollutant removal mechanisms including sedimentation, filtration and plant uptake of metals and nutrients. Constructed wetlands are also important habitats for aerial invertebrates, including marsh flies, which are predominantly wetland specialists. Marsh fly species are known bio-indicators in wetlands, making them a useful group to assess the wider dipteran community in wetlands. The use of constructed wetlands for the treatment of domestic, municipal, agricultural and industrial wastewaters is gaining in popularity. This is due to the fact that although the domestic wastewater of approximately one-third of the population of Ireland is treated by on-site domestic wastewater treatment systems, such as septic tanks, a large proportion of the country is inappropriate for such treatment, and alternative methods need to be used. It is also due to the population distribution in Ireland, which outside of urban areas, is low density and diffuse. In these areas, municipal wastewater is conventionally treated using activated sludge treatment plants, which often use constructed wetlands as a polishing step. It is estimated that there are more than 140 constructed wetlands used for the treatment of municipal, industrial and agricultural wastewater in Ireland. Over the years various attempts have been made, with varying levels of success, to compile a database of the performance of constructed wetlands in Ireland (Harty and Otte, 2003; Babatunde et al., 2008; Healy and O’ Flynn, 2012) and to review their performance (Hickey et al., 2018). [caption id="attachment_43167" align="alignright" width="300"] Figure 1: The home page of the constructed wetlands database[/caption]

To date, relatively little has been done in Ireland

The fact that such data was not centrally compiled and was often not even available in digital format, mitigated against any potential success. Other countries in Europe and elsewhere have successfully compiled performance databases of constructed wetlands, but to date relatively little has been done in this regard in Ireland. This means that an evidence-based picture of the performance of constructed wetlands in Ireland’s temperate maritime climate has been impossible to determine. Moreover, design modifications to constructed wetlands to optimise their performance under Irish climatic conditions have not been made. This could be very significant, as constructed wetlands have traditionally been designed in accordance with empirical equations that were developed for climates quite different to Ireland’s. Therefore, there is the possibility that constructed wetlands may not be optimally sized. As part of an EPA-funded project, NUI Galway researchers Drs Collette Mulkeen, Mark Healy and Prof Mike Gormally identified a need for a coherent, comprehensive and an up-to-date database of constructed wetlands performance in Ireland.

Reference point for constructed wetland designers, engineers, scientists and researchers

This will hopefully help in the development of design criteria, guidelines and operation methodology for constructed wetlands in the country, and provide an evidence-based reference point for designers, engineers, scientists and researchers. Using a mixture of published and unpublished data from local authorities, Irish Water, and the EPA, with the help of a DCU-based web developer, Sean Healy, the NUI Galway researchers set about compiling a database that would capture this data. It is now available at To use the database, the user first selects the county and wastewater type of interest (Figure 1). Three options for wastewater type are given: municipal, agricultural and industrial. After selection of county and wastewater type, another page is presented in which the user selects a wetland location within the county. If available, the data from this wetland is presented (Figure 2). [caption id="attachment_43168" align="alignright" width="300"] Figure 2: An example of a performance data sheet of a constructed wetland on the database[/caption]

Range of inlet and outlet water quality parameters

All of the wetland datasheets have the same format and list a range of inlet and outlet water quality parameters by sampling date. These databases may be downloaded (as an Excel worksheet) by clicking the ‘download’ button on the right-hand side of the screen (Figure 2). At the time of writing, there are more than 100 wetlands in the database. However, the database is far from complete. Those involved in the monitoring of wetlands are invited to submit any further constructed wetland locations or data they may have (in whatever format they choose) by clicking on the ‘Submit wetlands data’ button at the top right-hand side of the home page. This information is then compiled and uploaded on the website by the site administrator. In addition, a list of Irish constructed wetlands literature is available by clicking the ‘Publications’ button on the home screen. As there is a very vibrant community researching various aspects of constructed wetlands from a variety of perspectives (engineering, ecological and so on), they are encouraged to submit their publications to the website. This database should be seen as a centralised repository of performance data from constructed wetlands in Ireland. As the data is entirely user generated, engineers, technicians, or those sampling inlet and outlet water data in constructed wetlands in Ireland, are encouraged to engage with the website and submit data to it. The website is in its infancy and currently functions solely as an archive for research and performance data. However, in time, more information and interactive features will be added to it.


Babatunde, A.O., Zhao, Y.Q., O’Neill, M., O’Sullivan, B., 2008. Constructed wetlands for environmental pollution control: a review of developments, research and practice in Ireland. Env. Int. 34, 116-126. Harty, F., Otte, M.L. 2003. Constructed wetlands for treatment of waste water, in: Otte, M.L. (Ed.), Wetlands of Ireland: distribution, ecology, uses and economic value. University College Dublin Press, pp. 182-190. Healy, M.G., O’ Flynn, C.J. 2011. The performance of constructed wetlands treating primary, secondary and dairy soiled water in Ireland (a review). J. Environ. Manage. 92, 2348-2354. Hickey, A., Arnscheidt, J., Joyce, E., O’Toole, J., Galvin, G., O’ Callaghan, M., Conroy, K., Killian, D., Shryane, T., Hughes, F., Walsh, K., Kavanagh, E. 2018. An assessment of the performance of municipal constructed wetlands in Ireland. Journal of Environmental Management 210: 263 – 272. Authors: Collette Mulkeen, Mike Gormally, Sean Healy, and Mark Gerard Healy