## 4 Hybrid Technology
### Microalgae Technology  
The primary mechanisms by which microalgae remove antibiotics include bioadsorption, bioaccumulation, and biodegradation. Bioadsorption refers to the strong adhesion of organic pollutants to the surface of algae, which can subsequently be removed through photolysis [146; 147]. The efficiency of bioadsorption in microalgae is highly dependent on the structural characteristics of the target antibiotic, such as its hydrophobicity and the presence of functional groups that facilitate chemical adsorption, as well as the specific species of microalgae acting as adsorbents and the prevailing environmental conditions [148]. Consequently, species with a high affinity for target antibiotics, such as Chlorella and Scenedesmus, can be identified for their potential in antibiotic degradation [149]. Additionally, bioadsorption is influenced by pH; variations in pH can affect the ionization or dissociation of antibiotics in aqueous media, as well as the surface charge of the bioadsorbent, whereby microalgal cells uptake antibiotics, which can bind to intracellular proteins or other compounds. Moreover, the accumulation of antibiotics in microalgal cells may lead to the excessive production of reactive oxygen species (ROS). For instance, microalgae effectively remove sulfamethoxazole and levofloxacin through accumulation followed by intracellular biodegradation [150; 151]. Biodegradation has been demonstrated to be the most effective mechanism for the removal of antibiotics mediated by microalgae [152]. This process typically involves both extracellular and intracellular biodegradation, or a combination of the two, where the initial degradation occurs extracellularly, and the resulting degradation products may be further metabolized intracellularly [153]. Algal cells possess complex enzyme systems that catalyze various chemical reactions to degrade antibiotics. For instance, carbohydrate-active enzymes, redox enzymes, and hydroxyl radicals play particularly significant roles in the biodegradation of sulfonamides [154]. To improve the degradation efficiency of antibiotics by microalgae, researchers have proposed various innovative methods, including adaptive cultivation, co-metabolism, and microbial consortium systems. Adaptive cultivation improves the tolerance and degradation capacity of microalgae by pre-exposing them to antibiotic environments. For example, pre-adapted Chlorella increased its removal rate of levofloxacin from 16% to 28. Co-metabolism facilitates the synergistic degradation of antibiotics by introducing exogenous carbon sources. For instance, following the addition of sodium acetate, the removal rate of sulfamethoxazole by Chlorella vulgaris significantly increased from 6.05%to 99.3% [155]. Microbial consortium systems leverage the synergistic effects of microalgae and bacteria to enhance degradation efficiency; for example, a microalgae-activated sludge combined system achieved a removal rate of up to 97.91% for cephalosporiorin antibiotic [156]. Additionally, immobilized microalgae technology streamlines the harvesting process and improves the tolerance to antibiotics by embedding microalgae in carriers. For instance, [PERSON] et al. established a microalgae-biochar composite system, first cultivating Chlorella to the stable phase and then adding biochar, which further increased the removal rate of SMX to 45.7%. This is significantly higher than the removal rate of SMX by Chlorella alone at 34.4% and by biochar alone at 20.0% [157]. These methods provide substantial support for the practical application of microalgae technology. Despite the excellent performance of microalgae technology in antibiotic degradation, its large-scale application still faces numerous challenges. Firstly, the degradation efficiency of microalgae for antibiotics is significantly influenced by environmental conditions such as pH, temperature, and the properties of the target compounds. For example, the adsorption efficiency of tetracycline in Scenedesmus obliquus varies significantly with changes in pH [158].