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

Abstract

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 6h, the ammonium decreased from 13.22±0.98mg N/L to 0.40±0.02mg N/L, and within 5h, the nitrate decreased from 72.41±1.34mg N/L to 0.10±0.02mg N/L.