A trial of this new method of saline wastewater treatment was successfully conducted at the Bullock Creek Prawn Farm in 2007.
While the trial was conducted at an experimental scale, it has proven that the system can operate in a commercial environment using wastewater from earthen ponds.
The trial involved filtering prawn pond wastewaters through constructed sand beds where cultured sea worms were also growing.
Water handling rates were scaled so that a 1 ha sand bed could treat the water from 10 ha of prawn ponds with 10% exchange per day.
The results are currently being compiled but have shown excellent solids and chlorophyll removal and some very encouraging worm biomass production.
When the worms were harvested at an age of 20 weeks, about 50% of the biomass was immediately suitable for use as bait. A very broad range of fatty acids have been found in this worm biomass, suggesting that worms too small for sale as bait are useful for use as prawn or fish broodstock conditioning diets.
Innovation funding from the National Landcare Program has supported this year’s proof of concept work. Future work currently being planned aims to enable larger scale operations to proceed by integrating these systems into whole-of-farm models that have greater nutrient use effciency and diversity of product.
Assessment of lotus lilies for wastewater treatment:
This project aims to determine whether lotus lilies (Nelumbo nucifera)—a native freshwater plant—will trap sediment and improve water quality in a treatment pond that recycles water from a production pond full of fish (barramundi being the test species).
It also aims to increase water use effciencies and farm production effciencies by allowing concentrations of fish in particular areas—thus improving feeding, harvesting and bird protection procedures.
Although this project was initially hampered by many issues, they appear to have been resolved. The modification of using a pioneer native species of aquatic plant (Hydrilla sp.) in the pond has assisted greatly with the establishment of the lotus plants. Hydrilla established the pond area rapidly, improving the soil and water, which allowed the lotus to follow.
The lotus then sends out runners through the Hydrilla, shading and out-competing the Hydrilla plants. The lotus then becomes the dominant species in the pond. Preliminary results indicate that the two plants work well together in establishing the pond and assimilating nutrients from the water.
Meanwhile, the industry partner component of the project is progressing well. Preliminary assessment of the capabilities of lotus lilies in extensive fish production systems suggests a high potential to assimilate nutrients. The industry partner has also been successful in marketing the lotus pod to the local florist.
This project is supported by the Rural Industry Research Development Corporation (RIRDC) that will run for one production cycle and is due to finish in 2008. It was developed with support of the AAQ and works in conjunction with an industry partner (Daintree River Barramundi Farm). This project uses the pond facilities of the FFAC, Walkamin.
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