Nitrogen Dynamics and Biofloc Composition using Biofloc Technology to Treat Aquaculture Solid Waste Mixed with Distillery Spent Wash

Abstract Distillery spent wash (DSW) and aquaculture solid waste were homogeneously mixed and treated using biofloc technology to use DSW as a component of the substrate for biofloc production. The proportions of DSW, expressed as the proportion of the total chemical oxygen demand (COD), contributing to the total substrate content in the control group (GC) and treatment groups (G1/3 and G2/3) were 0, 1/3, and 2/3, respectively. The initial COD contents were statistically similar among all groups. During the experiment, the nitrogen dynamics process was consistent among all groups, and a higher content of dissolved inorganic nitrogen and less total organic nitrogen accumulated in the treatment reactors than in the GC reactors. The nitrogen recycling rate for G2/3 was 44.2%, which was significantly less than that for G1/3 (59.0%) or GC (69.7%). The biofloc production (considered as mixed liquor volatile suspended solid) in G2/3 was 1,237.3 mg/L, which was significantly less than that for G1/3 (1,662.3 mg/L) and GC (2,237.0 mg/L). Higher proportions of DSW in the substrate led to higher values of crude protein and crude lipid in the biofloc. There were no significant differences between the GC and G1/3 for linoleic acid, linolenic acid, total polyunsaturated fatty acids (PUFAs) or n‐6 PUFAs. However, the higher proportion of DSW (G2/3) significantly decreased the values of these fatty acids. The addition of DSW also decreased the settling ability of the biofloc.