![]() ![]() Like terrestrial plants, marine microalgae require nutrients such as phosphorous and nitrogen – two of the most significant nutrient emissions from finfish aquaculture – to grow, and researchers have exploited this trait to remove excess nutrients from recirculated, nutrient-rich water. The team used a combined approach of using microalgae to bioremediate the recirculated water, and bio-harvesting of these algae by zooplankton to maximise resource recovery, with the zooplankton being a suitable live feed source, particularly for fish larvae. Using the algae, the researchers extracted 100 percent of the phosphorous and 70 percent of the nitrogen from recirculated water sourced from a freshwater RAS operation Photobioreactor equipment used to process the wastewater by algae This problem has been addressed in the past by using biofilters – living microbial colonies that remove excess nutrients, such as nitrogen and phosphorous – however, an interdisciplinary research team at the Technical University of Denmark has shown that the sustainability of these systems can be taken one step further. Whilst RASs can effectively eliminate environmental and public health concerns over farm nutrient emissions into the aquatic environment, the quality of recirculated water must be precise in order to maintain fish health. But it’s challenging to remove the excess nutrients – which would harm cultured fish – from the water before recirculation. ![]() The increasing implementation of indoor recirculating aquaculture systems (RASs) has been used as a solution to mitigate this issue for both marine and freshwater aquaculture. ![]() Just as the waste nutrients of terrestrial fertilisers can stimulate harmful blooms of microalgae when they wash into aquatic environments, the nutrient-rich wastewater from open-system aquaculture operations can stimulate similar harmful eutrophication events, when not properly managed. ![]()
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