What to do about removing sludge and controlling fish diseases in an aquaculture facility was the topic of a recent day-long event, attended by about 30 fish farmers, politicians, company CEOs, and scientific researchers in Sønder Felding, Denmark. The theme of the meeting was water purification and disease control, a topic always on the minds of aquaculturists. The meeting was held at FREA, co-organized with KD Group, Aquamind, the University of Copenhagen, Aquapartners, and Eurofish. After a welcome and registration, attendees were given some background information on equipment for water purification, informed about FREA’s own experience with technology for managing sludge, and were shown the results from Copenhagen University’s work on the development of chips used for disease surveillance in aquaculture. After a lunch break, all were invited on a tour of FREA’s site for rainbow trout production, to get first-hand knowledge of the problems and solutions for active sludge management and disease control.
One challenge with sludge is water flow: with proper flow, sludge almost takes care of itself. Therefore, much of the work to solve the problem is optimising water flow, which is straightforward (if not easy) with recirculation systems. Biofiltration with algae/plant lagoons is another efficient technology for water purification. But local communities or natural environments often cannot absorb sludge from a fish farm, so the water must be purified before release. Much of the discussion at the event revolved round purification technologies, which differ by type of farm (e.g., intensive or extensive) but all types can be improved by these technologies. Fish farms can greatly reduce the amount of nitrogenous and phosphorous waste, reducing their environmental footprint.
The University’s work on chip technology focuses on important fish pathogens in Danish aquaculture. The chip is used to identify through DNA the level of the pathogens in the sludge, and by initiating water treatment diseases can be inhibited before they appear as clinical symptoms or mortality in the fish.