## 4 Discussion  
The variations in water quality parameters (SS, BOD, TOC, TN, and TP) observed in this study demonstrate a strong correlation with the characteristics of each treatment stage. Notably, the coagulation-sedimentation stage resulted in a substantial reduction of SS, achieving a high removal rate of 92.2%, indicating effective sedimentation of particulate matter through floc formation. Previous research indicates that the optimal alum concentration varies depending on the characteristics of the wastewater. Studies on abattoir and livestock wastewater have reported a 99% removal efficiency of SS at an alum concentration of approximately 1000 mg/L. Furthermore, these studies suggest that increasing the alum  
Figure 5: Correlation heatmap matrix illustrating the relationships between water quality parameters, antibiotics, and ARGs. [PERSON]’s rank correlation coefficient was employed to evaluate the correlation matrix. The significance levels are denoted as \(p\) < 0.05 for \({}^{*}\), \(p\) < 0.01 for \({}^{**}\), and \(p\) < 0.001 for \({}^{***}\). dosage beyond this level does not significantly improve removal efficiency [43; 44]. In this stage, TP was also reduced by 96.9%, confirming that inorganic phosphorus components can be effectively removed by coagulation-sedimentation. Conversely, the removal rates of BOD (33.6%) and TN (3.1%) were relatively low. While aluminum sulfate is generally regarded as the most effective additive for floc formation, its capacity for TP removal is limited and contingent upon factors such as sedimentation time, pretreatment methodology, and the characteristics of the wastewater itself [45]. The activated carbon stage led to some improvements in the removal of BOD and TOC; however, the ozonation reactor yielded only marginal changes. This suggests that most organic matter and particulate material have already flocculated, leaving primarily dissolved substances [46]. Notably, the TN concentration decreased by 95.9% compared to the initial concentration in the final degassing process, indicating that nitrogen removal primarily occurred through degassing. In coagulation and sedimentation processes, nitrogen removal in swine wastewater has often been limited since nitrogen is predominantly in the form of ammonium nitrogen rather than organic nitrogen, making air stripping a more effective removal method [47; 48]. Therefore, while physicochemical processes offer limited nitrogen removal capabilities, ammonia stripping or degasification processes can effectively eliminate nitrogenous components [49]. The concentration profiles of the residual antibiotics throughout the treatment train underscore the pivotal role of coagulation-sedimentation in removing certain antibiotic compounds. Sulfamethazine experienced a 52.5% reduction after coagulation-sedimentation, suggesting that adsorption to SS and floc formation were critical mechanisms in reducing its concentration. Tetracyclines are removed via coagulation, whereas sulfonamides are removed through adsorption onto the surface of coagulant hydrolysis products and subsequent interparticle bridging [50]. However, oxytteracycline, chlortetracycline, and fenbendazole were rapidly reduced to below detection limits immediately following flocculation. This observation aligns with previous reports indicating their short half-lives and low persistence in wastewater treatment facilities, highlighting the need for further detailed studies [51]. Interestingly, the concentrations of some antibiotics (e.g., sulfamethazine, tiamulin) rebounded slightly after sand filtration or reappeared in trace amounts in later stages. This \"rebound\" phenomenon could arise from the desorption of compounds that had temporarily accumulated in the filter media; hydraulic fluctuations could lead to the release of adsorbed antibiotics. Alternatively, microbial community shifts could cause partial biodegradation and subsequent byproduct formation [52].