Integrated degradation of bacteria, organic pollutants, total phosphorus, and antibiotics in food wastewater through immobilization of Bacillus velezensis on polyethylene glycol-polyvinyl alcohol/sodium alginate/nano-TiO2 microspheres.

Food wastewater is characterized by complex composition and a wide range of pollutants. Existing treatment methods are often inefficient for single pollutants and new, environmentally friendly, and integrated treatment methods are needed. This study aimed to construct a novel polyethylene glycol (PEG)-polyvinyl alcohol (PVA)/sodium alginate (SA)/nano-TiO2 hydrogel microsphere-immobilized Bacillus velezensis system for the integrated degradation of complex pollutant components in food wastewater. SEM, FT-IR, XRD, mechanical, rheological, and swelling properties of the microspheres were tested, which confirmed the presence of nano-TiO2 in the microspheres and effectively improved the physical properties of the microspheres. The results showed that the microspheres containing 0.5 g/L nano-TiO2 in the preformed gel solution 1 had the best morphology, mechanical strength, physical stability, and 57.5 % bacterial carrying capacity. The microspheres inhibited Escherichia coli and Staphylococcus aureus and did not affect the growth and reproduction of Bacillus velezensis. The system achieved integrated degradation of chemical oxygen demand (COD), total phosphorus (TP), and antibiotics in food wastewater with degradation rates of 71.85 %, 36.84 %, and 40.52 %, respectively, and remained highly efficient after five times reuse. This method is environmentally friendly, efficient, and economical, which provides a new idea for wastewater treatment by immobilized microbial technology.