Location : Ballajura, WA
A few years ago, Emu Lake was brown, smelly and unhealthy with very little bird life and was over-run with feral fish. While the Lake had been popular with the locals, the Local Government responsible for the area recognised that to improve the water conditions and quality of the environment they needed to take a multi-staged approach to clean up the problem. This 5-year program would encompass removal of feral fish species, reintroduce native fresh water fish and run an education program to prevent re-occurrence.
The popularity of Emu Lake with the local people had led to a number of problems with the quality of the water that needed to be addressed. These included:
Reduce Nutrient Load and Removal of Feral Fish:
Feral species such as koi-carp, goldfish, yabbies and ornamental cichlids, released into the environment by ill-informed pet owners, have a devastating impact on wetland habitats, by stirring up lake sediments and uprooting aquatic vegetation which in turn leads to increased nutrient concentrations and potentially toxic algal blooms. These introduced species are usually more aggressive and breed more frequently than native fish species, easily out-competing them for food and habitat. They also have the potential to bring exotic diseases to native fish populations.
Locals were used to feeding the local bird population – a harmful practice to both the water, the bird population and the fish who lived in the lake. Introduced food matter to the water body through not being eaten, as well as the waste produced by the animals breaks down in the water causing nutrient overload. When the level of organic material is excessive in a lake, available dissolved oxygen may be consumed and depleted as decomposers break down the organic plant and animal material. This process may have a negative effect on other oxygen dependent aquatic organisms such as zooplankton, fish and insects. If levels of oxygen become too low, only a few species tolerant of low oxygen conditions will be able to decompose organic matter. Decomposers which do not need oxygen are anaerobic bacteria, and although helpful, they produce noxious gases as a by-product of their metabolism.
Water quality was also affected by nutrient run off from surrounding gardens from over fertilisation which causes algal blooms.
Reducing nutrient load is vital to the success of the project. However, to ensure the success of the project, oxygen needed to be pumped back into the water to counter the depletion caused by algal blooms. The project also required the re-introduction of plant life suitable to the ongoing clean up of the Lake.
The team responsible for the remedial work on the lake had undertaken research throughout the consultation phase and had shortlisted several companies who had systems that could assist with the clean up of the lake. Further investigation into features, benefits and costings was conducted before Allied Pumps was approached to put forward a proposal for the Floating Treatment Wetland.
The client had strict requirements for their new Floating Treatment Wetland.
“Due to the environmental nature of this project floating panels manufactured from recycled materials are preferred. The floating panels must provide an optimum environment to allow for the establishment of rushes and sedges or other wetlands species. The panels shall provide a media so that plants roots systems can penetrate the panel and form extensive root structures within the water column underneath.”
The Floating Treatment Wetland System is made from 100 per cent recycled polyethylene
terephthalate, commonly known as PET which is used in plastic drink bottles. The recycled plastic is made into a non-woven, non-toxic durable matrix of fibres. The FTW can be used in any water environment requiring treatment provides a fertile base for plants and vegetation to grow. These wetland sedges, rushes and grasses grow through the biofilm creating superior root structures within the water to provide an increased surface area. It is within these biofilms which microbes and bacteria trap and digest organic matter and nutrients, including total suspended solids, biochemical oxygen demand, nitrogen and phosphorous.
In calculating the area needed to be cleaned and remediated 33 standard modules 330m2 (4m x 2.3m each module) of SPEL Floating Treatment Wetland (FTW) was recommended and supplied.
In addition to the FTW and recognising the poor oxygen quality of the water a pump was installed to ensure water flowed through the Floating Treatment Wetland promoting growth and health of the water, which was an essential requirement of the project.
The Floating Treatment Wetland was packed into a large sea container and delivered to site ready for installation by the client.
The Floating Treatment Wetland were assembled on site and anchored in place. The newly introduced plants are becoming established and have begun their job of cleaning the water.