About this document
This is the final report of a desk-top study designed to provide ‘proof-of-concept’ for the use of the giant reed (Arundo donax) in constructed wetland systems designed to remove contaminants from dairy processing factory wastewater streams. Activities were therefore restricted to information collection, collation and evaluation. No field or laboratory activities were planned or have been conducted. The following conclusions and recommendations can be made with respect to the objectives of the project.
This is the final report of a desk-top study designed to provide ‘proof-of-concept’ for the use of the giant reed (Arundo donax) in constructed wetland systems designed to remove contaminants from dairy processing factory wastewater streams. Activities were therefore restricted to information collection, collation and evaluation. No field or laboratory activities were planned or have been conducted. The following conclusions and recommendations can be made with respect to the objectives of the project.
The giant reed is a perennial, herbaceous plant found in grasslands and wetlands over a wide range of climatic and habitat conditions. The giant reed is found in most parts of Australia, including in Victoria, but is not listed as a noxious or invasive weed Australia-wide, although it is locally declared in New South Wales (and thus its use is also prohibited in Western Australia). The giant reed is not a declared weed in Victoria, and is apparently readily available from a number of garden suppliers. However, A. donax has some traits, such as fast growth rate, diffusion via flood-mediated rhizome dispersion, rapid re-growth after fire, and invasion of riparian zones that make it a potential weed. Before A. donax is used in constructed wetlands in Victoria, South Australia, Queensland, the ACT, Northern Territory or Tasmania, consideration should be given to a detailed survey of its distribution within the relevant state. Such a survey should include an ecological assessment of local and/or regional adaphic and biotic factors that may constrain or promote its ability to become a weed.
Arundo donax has some characteristics that make it suitable for use in constructed wetlands for wastewater treatment. These include its fast growth rate, high water consumption, apparent salt tolerance (still to be confirmed), ease of propagation from rhizomes, limited reproduction from seed (reduced risk of off-site dispersal), limited number of pests, and the many potential uses for above-ground biomass. There is limited information on the use of A. donax in constructed wetlands, although the giant reed has been planted in several research and treatment wetlands (e.g. in Arizona and Crete). Very little treatment performance data is available for these wetlands, although the tendency for impenetrable stands of A. donax to rapidly dominate reed-bed systems has been noted.
Constructed wetlands are currently not able to remove sodium originating in factories and associated anaerobic water treatment plants. However, finding plants able to tolerate high salt loads could facilitate the use of constructed wetlands to ameliorate the organic and nutrient loads being discharged by factories. Insufficient detailed information on A. donax exists to adequately assess the advantages and limitations of A. donax compared with other common wetland plants (e.g. Phragmites australis). Consideration should be given to the establishment of pilot scale wetlands using A. donax to:
- examine the effectiveness of the giant reed (A. donax) in stripping nutrients and organic material from effluent by evaluating chemical transport, assimilation and release in pilot scale constructed wetlands, and in comparison with the common reed (Phragmites australis)
- assess the salt tolerance of A. donax
- examine options for the sustainable re-use of the biomass produced by A. donax
- investigate management techniques to minimise risk of escape of A. donax from constructed wetlands.