Algae–Bacteria Symbiosis Enhances Treatment Efficiency and Microbial Resilience in Livestock Wastewater Containing Metal–Antibiotic Complexes

Livestock and poultry farming wastewater contains a large number of antibiotics and heavy metals, and the complexation reaction between them increases the toxicity of the original wastewater. However, there is still a lack of research on the treatment of compound polluted wastewater. This experiment demonstrated the feasibility of utilizing algal–bacterial symbiosis to treat wastewater contaminated with compounds. The results showed that the complexation reaction between heavy metal ions and antibiotics in compound pollution was more damaging to the algal–bacterial symbiosis system, while the presence of bacteria greatly facilitated the growth of microalgae, which have a biomass yield of 0.397–0.438 g/L in pollutant-containing wastewater. In addition, it was found that SM2 removal in composite polluted wastewater relies mainly on the bacterial community, and the removal rate reached 17.4–31.3%. In contrast, the adsorption of heavy metal Cu2+ relies mainly on algal cells, and its adsorption removal rates were 63.0, 56.2, and 49.2%. This study traced the transport route of SM2, and its degradation mainly included ·OH hydroxylation, rearrangement formation, and S–N bond cleavage. In addition, the complexation reaction between Cu2+ and SM2 was analyzed, and three complexation structures were proposed. The research bridged the gap in the technology of algal–bacterial symbiosis for the treatment of compound polluted wastewater.