Scheme of RAS used as a water source for the growth of experimental (individually housed) Nile tilapia: HIGH accumulation RAS (30 L/kg feed/day), MIDDLE accumulation
RAS (70 L/kg feed/day) and LOW accumulation RAS (1500 L/kg feed/day) used. At the HIGH and MIDDLE accumulation RAS water flows from culture tanks (1.80 m3) and
experimental tanks (0.77 m3) – drum filter (Hydrotech HDF 501-1P, 0.02 m3; mesh size 90 μm) – sump 1 (0.60 m3) – trickling filter (0.07 m3; water flow: 151.2 L/min; ventilators air
flow: 1.39 m/s; media Bionet 200 m2/m3, media volume 1.2 m3) – sump 2 (0.30 m3) – oxygen cone (0.05 m3) – culture tanks/experimental tanks. One parallel flow across the
denitrification reactor using only fecal carbon as energy source flows from the drum filter – buffer tank (0.02 m3) – denitrifying reactor (0.48 m3) – drum filter. At the LOW
accumulation RAS water flows from experimental tanks (0.77 m3) – tube settler (1.31 m3) – sump 1 (0.74 m3) – trickling filter (0.07 m3) – sump 2 (0.02 m3) – experimental tanks.
The flow rate across the culture tanks was approximately 26 L/min; across the experimental tanks was approximately 2 L/min and 0.6 L/min across the USB-reactor.