Exploring single-stage oxic process for simultaneous rapid recovery of phosphate and nitrate via bioflocs to promote circular economic

Intensive aquaculture systems often contain high concentrations of nitrate and phosphate, leading to environmental and economic burdens. Bioflocs technology, a novel approach in aquaculture, addresses these issues by removing these nutrients and producing protein rich microbial biomass. This study explored a novel single stage oxic process for simultaneous rapid recovery of phosphate and nitrate using different carbon addition strategies in bioflocs growth reactors. Our findings revealed that bioflocs rapidly and effectively assimilated nutrients from high concentration environments. The phosphate removal mechanism involved biomass formation, achieving simultaneous removal efficiencies of 5.5 ± 0.2 mgP/gTSS/d for phosphate and 41.8 ± 2.0 mgN/gTSS/d for nitrate, harvesting biofloc concentrations of 3599 ± 33 mg/L. The crude protein content of the bioflocs exceeded 50 %, with essential amino acid indices over 0.9, indicating potential for high quality aquafeed. Actinobacteriota and Bacteroidota were dominant during the phosphorus removal process, with significant proliferation of Nakamurella. Additionally, gene amplification related to assimilation, aerobic denitrification and inorganic phosphate transport was observed, suggesting biofloc technology is a promising method for efficient phosphate and nitrate removal. This research promotes the circular economy by recovering nutrients, reducing reliance on traditional feed sources, and minimizing environmental contamination.