In recent years, there has been increased interest in alternative and
innovative technologies which are used in the treatment of wastewaters, with
the aim of developing efficient systems which are low-cost and lowmaintenance.
However, greywater reuse from domestic houses appears to
have received very little attention and the role of indigenous wetland plants,
especially submergents, in contributing to nutrient reduction in wastewater
is largely unknown.
Species of Triglochin, commonly known as water ribbons, are fast growing
submergent macrophytes. In Western Australia, Triglochin huegelii is
mainly a submergent plant but as water recedes, the leaves become
emergent. Triglochin huegelii can tolerate a range of water regimes and high
nutrient concentrations, and this is useful in wastewater treatment
applications. The aims of this present study were to examine the use of
Triglochin huegelii for domestic greywater treatment, to compare the
effectiveness of this plant with other better known, and more frequently used,
emergent macrophytes, and to investigate why Triglochin huegelii is so
successful in nutrient accumulation.
A series of investigations using Triglochin huegelii in greywater treatment
experiments showed that Triglochin has consistently removed more nitrogen
and phosphorus, in all parts of the plant - leaves, tubers and roots, than most
other indigenous emergent macrophyte species, including those of
Schoenoplectus, Baumea and Juncus which are commonly used for wastewater nutrient-stripping. In some cases, such as in the leaves, twice as
much nitrogen (N) and one and a half times more phosphorus (P) is
assimilated in the Triglochin tissue. In all parts of the plant there has been
an increase in Total N and Total P.
Investigations were conducted using different environmental conditions for
the plants. A comparison was made between root zone (substrate-only) and
complete pond conditions, with some changes to loading rate and retention
times. Triglochin huegelii has many practical applications in wastewater
management, especially if the level of influentlwastewater can be controlled,
thus allowing sufficient time for Triglochin huegelii to respond with changed
structure and morphology. Proline, a substance known to be produced by
plants under stress (such as changing water levels), was detected in
Triglochin huegelii.
In a pond, the leaves of Triglochin can be directly involved in nutrient
absorption and assimilation. A study of leaf structure and other aspects of its
biology showed that nutrients can easily pass into leaf tissue and then into
other regions in the plant. In Triglochin huegelii, nitrogen was primarily
stored or found in leaves then tubers then roots, while levels of phosphorus
were higher in tubers then roots then leaves.
The above-ground:below-ground (AG:BG) ratio of Triglochin huegelii also
depends on the water regime. For all samples, whether pond or substrateonly,
the ratio was 0.84. However, when consideration is given to pond
conditions the ratio increases to 1.11. It appears that in pond conditions, and especially with long retention times, proportionally more above-ground
growth (leaves) occurs and in substrate-only conditions, proportionally more
biomass is found below-ground, with the number and size of leaves reduced
in these plants.
The highest nutrient levels recorded for Triglochin huegelii were 11.74 mgP/g
and 35.7 mgN/g dry weight. Triglochin huegelii has been found to have a
protein content of at least 1.7 g/100 g wet weight in the leaves, and less in roots
and tubers. Triglochin huegelii could have potential as a fodder source
because of its high protein content, similar to that of lucerne.
Triglochin huegelii seems to remove nitrogen and phosphorus at a greater
rate than many other types of aquatic macrophytes. Other parameters such
as BOD, Suspended Solids and fecal coliforms were also examined, with
reductions of up to 90%, 84% and 99% respectively. 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. In
addition, systems need to be designed that mimic natural ecosystems, and yet
are economical and functional.
This current research can be used as a basis for further study to establish the
extent of nutrient removal by Triglochin huegelii and its interactions with
other macrophytes in polyculture systems.
| Identifer | oai:union.ndltd.org:ADTP/221878 |
| Date | January 2001 |
| Creators | Ross Mars |
| Publisher | Murdoch University |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.murdoch.edu.au/goto/CopyrightNotice, Copyright Ross Mars |
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