Vertical flow reed bed systems are more effective than horizontal flow reed beds in not only reducing organics and suspended solid levels, but also in nitrifying ammonia nitrogen to nitrate. Hybrid reed bed systems, normally incorporating one or two stages of vertical flow followed by one or more stages of horizontal flow in series, may be designed to achieve higher treatment efficiency and in particular target total nitrogen removal, as well as organic reduction and pathogen removal. Free water surface based constructed reed bed need to be much larger than their subsurface counterparts to achieve the same level of treatment as the surface of the wastewater is at or above the surface of the soil support media. These systems however, can promote superior ecological diversity and aesthetics. There is a scarcity of reliable long-term performance data relevant to Ireland and its climate for such systems, and reluctance exists amongst some local authorities to permit the use of reed bed as stand-alone secondary treatment syatem.