Study of advanced treatment of low concentration tetracycline wastewater in two-stage MBBR system

In this research, a two-stage reaction system was developed, incorporating a moving bed biofilm reactor (MBBR) and a photocatalytic reactor. This was based on the preparation of suspended graphitic carbon carriers, with the aim of investigating the system's efficacy in removing low-concentration tetracycline wastewater. Initially, the preparation conditions for the novel floating composite photocatalyst were optimized. Then the photocatalytic reaction system was constructed using this photocatalyst to remove convective dynamic tetracycline wastewater. The maximum degradation rate of tetracycline wastewater, with an influent concentration of 50 mg L⁻¹, achieved in the photocatalytic reaction system was 99.32%. Subsequently, the working conditions of the bio-MBBR reaction system were optimized, including chemical oxygen demand (COD) and filler feeding rate. The optimal reaction conditions were then selected and combined with the photocatalytic reaction system to investigate the treatment effect on tetracycline wastewater of varying concentrations. The results indicated that even when the concentration of tetracycline (TC) in the influent water remained at 3 mg L⁻¹ for 11 days, the average removal rates of TC, COD, total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (NH₄⁺-N) were still 92.25%, 87.43%, 87.49%, 66.81%, and 95.72%, respectively. This suggests that the MBBR coupled photocatalytic reactor has a significant removal effect on wastewater containing low concentrations of antibiotics.