AlgalBLOCK

The initial impetus for AlgalBLOCK originated from the Earth Systems collaborative work with the Water Studies Centre, Monash University, Australia (Professor Barry Hart) and the research centre Karlsruhe (FZK), Karlsruhe, Germany to develop an active barrier of calcium carbonate (CaCO3) to prevent phosphorus release from lake sediments, and therefore reduce the risks of algal blooms. A proposed name for the CaCO3 barrier is AlgalBLOCK.

Many water bodies in Australia and elsewhere in the world are experiencing an increased number of algal blooms, which can reduce the amenity value and ecological health of the water body and clog filters, increasing maintenance costs. If the algae are predominantly cyanobacteria (blue-green algae), they can also be toxic. Of the number of factors required for an algal bloom to occur, perhaps the most important is an excess of nutrients (particularly phosphorous and nitrogen).

Limestone was favoured by the researchers due to its status as a natural and environmentally benign mineral. After significant research, it was established that while natural limestone was not effective in phosphorous control, a manufactured form of limestone, precipitated calcium carbonate (PCC), was highly effective. Additional collaborative research confirmed the effectiveness of the PCC. The results of the research have been published in a series of scientific journals.

The initial research was conducted with high quality imported PCC and a lower-cost variety of PCC that was synthesised by Earth Systems. PCC is not currently made in Australia. Small quantities are imported from Malaysia, China and Germany to meet the requirements of other applications (eg. whitener, filler for paper, paint and plastics). Imported varieties can be very expensive, with some materials costing up to a$ 2,500 per tonne. In order to improve the market potential and profitability of AlgalBLOCK installations, Earth Systems identified an industrial by-product that can be readily converted into PCC. Collaborating with the company that routinely sells the by-product, Earth Systems produced several kilograms of PCC to assist with the initial laboratory testwork. Both the imported and locally manufactured materials performed well in controlling phosphorous release from sediments and lowering concentrations in the water column.

Initial field trials produced mixed results, with efficacy of the treatment appearing to be affected by salinity. Earth Systems Technologies requires further funding to conduct additional independently monitored field demonstrations. Earth Systems has significant expertise and a track record of dosing large water bodies with reagents having already developed and commercialised specialised dry reagent dosing systems for large water bodies that will be ideal for many AlgalBLOCK installations.

PCC barriers will be effective until they are saturated with phosphorous. This will be a function of sediment phosphorous load, the phosphorous release rate and the thickness of the installed barrier. Further dosing will then be required.

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