The role of the submergent macrophyte Triglochin huegelii in domestic greywater treatment

Conventional reedbed systems, which are used in wastewater treatment, are l ittle more than monocultures of Phragmites, Baumea, Water Hyacinth (Eichhor nia crassipes), Typha or Schoenoplectus. Pond systems, employing a wider ra nge of species, are a means to recycle more nutrients, improve treatment po tential and mirror natural ecosystems in ways to sustain the ecosystem. Spe cies of Triglochin, commonly known as water ribbons throughout coastal Aust ralia, are fast-growing submergent macrophytes which seem to be adapted to high nutrient concentrations. In Western Australia, Triglochin huegelii is mainly a submergent plant but its leaves tend to float on the surface in sh allow waterways and it has been found seasonally in some ephemeral swamps a nd lakes. As water receedes, the leaves become emergent. Initial studies us ing T. huegelii in wastewater treatment experiments has shown that Trigloch in has consistently higher concentrations of nitrogen and phosphorus than S choenoplectus validus, an emergent commonly used for wastewater nutrient st ripping, in all parts of the plant - leaves, tubers and roots. In some case s, such as in the leaves, twice as much nitrogen and one and a half times m ore phosphorus is assimilated in the Triglochin tissue. It is also likely t hat T. huegelii will remove nitrogen and phosphorus at a greater rate than many other types of aquatic macrophytes. The implication is that instead of only planting the perimeter of lagoons, artificial wetlands and constructe d basins we should be planting the bulk of the waterway with submergent spe cies such as Triglochin spp. which may be far more effective in stripping n utrients than emergents currently used for that purpose. (C) 1999 Elsevier Science B.V. All rights reserved.