Inorganic nitrogen dynamics in sequencing batch reactors using biofloc technology to treat aquaculture sludge

Inorganic nitrogen dynamics in a sequencing batch reactor (SBR) using biofloc technology (BFT) to treat suspended solids (SS) in a recirculating aquaculture system (RAS) stocking jade perch (Scortum barcoo) were explored in the current study. One group was dosed with glucose (SBR-glu) as an organic carbon source, and the other group had no added carbon source (SBR-con). The results showed that ammonium released from aquaculture SS was assimilated by heterotrophic bacteria to form bioflocs with sufficient additions of a carbon source. Autotrophic nitrification was also observed, perhaps due to the shortcomings of the carbon source. The 5-min floc volume index (FVI-5) was lowest on the 8th day, when the dissolved oxygen was also at its lowest level. The crude protein content of the flocs from SBR-glu was 30.42 +/- 0.55%, whereas that of SBR-con was 26.32 +/- 0.78% during the first 33 days. Sharp reductions in ammonium and nitrate in SBR-glu were found: within 6 h, the ammonium decreased from 13.22 +/- 0.98 mg N/L to 0.40 +/- 0.02 mg N/L, and within 5 h, the nitrate decreased from 72.41 +/- 1.34 mg N/L to 0.10 +/- 0.02 mg N/L. (C) 2012 Elsevier B.V. All rights reserved.