Assessing the fate of antibiotics and heavy metals in biofloc systems: Removal efficiency and bioaccumulation risk

The intensification of aquaculture has led to concerns over the use of antibiotics and the accumulation of heavy metals in aquaculture systems, posing risks to environmental security and food safety [1]. Biofloc Technology (BFT), a sustainable aquaculture approach, is renowned for its ability to maintain water quality through microbial conversion of nitrogenous wastes². However, its role in mitigating chemical contaminants like antibiotics and heavy metals remains complex and inadequately synthesised. This comprehensive review assesses the dual role of BFT systems in influencing the fate of these pollutants. We examine the mechanisms of removal, primarily through biosorption, bioaccumulation, and biodegradation facilitated by the rich microbial community and extracellular polymeric substances (EPS) of bioflocs. Evidence indicates that BFT can significantly reduce antibiotic concentrations and sequester heavy metals from the water column, enhancing overall system water quality. Conversely, this very efficiency presents a significant risk: the bioaccumulation of these contaminants within the biofloc biomass and their subsequent transfer into the tissues of cultured species, potentially amplifying exposure. This review synthesises current literature on removal efficiencies for various antibiotics and metals, analyses the factors affecting their fate (e.g., C/N ratio, floc maturity, pH), and evaluates the associated bioaccumulation risks. We conclude that while BFT shows promise as a bioremediation tool, its implementation necessitates careful management to prevent it from becoming a reservoir and vector for contaminants. Future research directions should focus on understanding the microbial degradation pathways, the long-term stability of sequestered metals, and the development of safety standards for the reuse of biofloc biomass.