Performance of a recirculating tank-based system utilizing floating and submerged filters with a denitrification column for the culture of barramundi (Lates calcarifer)

In the aquaculture industry as much as 90% of the water utilised can be recycled in specialized systems. In this study, a four-stage filtration system was designed which\ud harnessed mechanical and bacterial processes. The stages include flocculation and mixing, floating medium filter, sand filter and an activated carbon (AC) filter which acted as a denitrification column. The experiment duration was for 25 days with barrarnundi stocked at approximately 8 kg per m3 in a 300-litre system. The AC filter displayed an average\ud turbidity removal rate of 40% while the sand filter disp1ayed 19%. The sand filter exhibited an average nitrification rate of 57 g TAN/ m3/ day while the AC filter illustrated its potential as a denitrification filter with a mean nitrate removal rate of 71 g NO3/m3 /day with the addition of methanol as the organic carbon source. Over the duration of experiment, the system required 8.6 m3 of water for filter backwash. On the other hand, the water requirement for the semi-flow through control system (which did not have any water treatment) was 13.75 m3, which was used for water exchange. There was no significant difference in mean individual weights of fish between the control and treatment tanks at day 25