expenses in running a BFT system. In the current study, the amount of
carbon added to the BFT tanks was calculated based on the feeding
rate of the fish, and 0.9 kg of sucrose was consumed per kilogram of
fish produced.
In addition to carbon source, aeration is another major expense in
running a BFT system. Aeration is used to supply oxygen and mix the
components in the water (Hargreaves, 2013). In the current study,
one compressed air root blower (135 W) was used to maintain the
DO in the RAS tanks at over 6 mg L−1
. However, using two compressed
air root blowers was required in the BFT tanks tomaintain the same DO
level (N6mgL−1
). Approximately 11.22 kWof energy was consumed
to produce 1 kg of fish using RAS tanks,whereas 22.44 kWwas required
to produce the same amount using BFT tanks.
In the process of nitrification, 7.15 g of alkaline was consumed per
gram of TAN converted to NO3
−-N in the RAS, whereas in the BFT, TAN
was assimilated by microorganisms and converted into biofloc protein
and only 3.57 g of alkaline was consumed per gram of TAN converted
(Ebeling et al., 2006). During the experimental period, the amount of
NaHCO3 used to maintain a stable pH was less in the BFT tanks than in
the RAS tanks.