Constructed wetlands for domestic wastewater treatment
In separate situations where a conventional septic tank installation is considered unsuitable, some form of secondary treatment system may have to be installed to improve the quality of the effluent before discharge to subsoil. Reed bed treatment systems are one such technology which has seen significant growth recently, being deemed an effective and low-cost alternative treatment system used for either secondary or tertiary treatment applications in place of the percolation area. However, local councils in Ireland to date are still reluctant to permit the use of reed beds as stand-alone secondary treatment systems given the scarcity of reliable long-term performance data relevant to Ireland and its climate, and their apparent poor winter treatment performances.
An ongoing project, funded by the EPA, is investigating the performance of three horizontal flow subsurface reed beds used as secondary or tertiary treatment processes for on-site wastewater effluent. The reed beds are being intensively studied for a period of two years during which their treatment performance for chemical and microbiological parameters is being measured across different climatic conditions (Figure - Reed bed being used as tertiary treatment for domestic on-site effluent).