Effect of nano-zinc oxide concentration on nutrient and antibiotics removal performance by microalgae-bacteria-fungi consortia system treating aquaculture wastewater

In the context of the booming global aquaculture industry, the discharge of aquaculture wastewater containing nutrients and antibiotic residues has led to serious environmental problems. This study explored the effect of nano-zinc oxide (nZnO) concentration on the nutrient and antibiotics removal performance of microalgae-bacteria-fungi consortia systems. Four different algae treatment technology systems were established. The results showed that Strain 3 (Chlorella ellipsoidea + S395–2 + Clonostachys rosea) had the best performance. A concentration of 40 mg/L nZnO was most beneficial for the growth of the consortia, enhancing photosynthetic performance and promoting the removal of nutrients such as COD, TN, and TP. The growth rates of all strains reached the maximum, and Strain 3 had the highest removal efficiencies of COD (88.52 ± 8.19 %), TN (86.44 ± 8.05 %), and TP (86.51 ± 8.25 %) among the four strains under this concentration. For antibiotics removal, a 40 mg/L nZnO concentration was optimal. Strain 3 showed the highest removal rates for various antibiotics. The removal rates of tetracycline (TC) and oxytetracycline (OTC) by Strain 3 at 40 mg/L nZnO reached 99.08 ± 0.62 % and 96.45 ± 2.63 % respectively. The removal mechanisms involved the synergistic effects among microalgae, bacteria, and fungi, as well as the influence of nZnO on the metabolic activities of microorganisms. The optimized symbiotic system and nZnO concentration regulation strategy proposed in this study not only efficiently treat aquaculture wastewater but also reduce chemical usage through natural microbial metabolism, providing a cost-effective and eco-friendly sustainable solution for wastewater remediation.