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Using submergent macrophytes for domestic greywater treatment

Mars, R., Mathew, K. and Ho, G. (1996) Using submergent macrophytes for domestic greywater treatment. In: Mathew. K. & Ho, G. (eds) Workshop on wetland systems for wastewater treatment, 25 September, Perth, Western Australia pp. 105-117.

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Abstract

Aquatic plants offer a technically simple, low cost, energy-efficient method of treating domestic greywater. Aquatic plant systems require little technical back-up and are easy to maintain. Certain rooted aquatic plants have bacteriocidal properties and the ability to breakdown chemical pollutants, and submerged aquatics are also important as oxygenators.

Reeds and rushes take up and store nutrients themselves, provide a growing area for micro-organisms, stimulate the soil activity by root excretions and reduce the volume of effluent by transpiration. Effluent passes through various stages and the wastewater is gradually stripped of nutrients and pollutants.

However, conventional reedbed systems are little more than monocultures of Phragmites, Baumea, Water Hyacinth, Typha or Schoenoplectus. Pond systems, employing a wider range of species, is a means to recycle more nutrients, improve treatment potential and mirror natural ecosystems - in ways to sustain the ecosystem.

Species of Triglochin, commonly known as water ribbons throughout coastal Australia, 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 shallow waterways and it has been found seasonally in some ephemeral swamps and lakes. As water recedes, the leaves become emergent.

Initial studies using Triglochin huegelii in wastewater treatment experiments has shown that Triglochin has consistently more nitrogen and phosphorus than Schoenoplectus validus, an emergent commonly used for wastewater nutrient stripping, in all parts of the plant - leaves, tubers and roots. In some cases, such as in the leaves, twice as much nitrogen and one and a half times more phosphorus is assimilated in the Triglochin tissue.

One prediction is that Triglochin 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 constructed basins we should be planting the bulk of the waterway with submergent species such as Triglochin spp which are far more effective in stripping nutrients than emergents currently used for that purpose.

Publication Type: Conference Paper
Murdoch Affiliation: School of Environmental Science
Publisher: Murdoch University
URI: http://researchrepository.murdoch.edu.au/id/eprint/23658
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