Antibiotic resistance genes (ARGs) are emerging contaminants that pose a potential threat to human health worldwide. Urban wastewater treatment plants (WWTPs) are a main source of both antibiotic-resistant bacteria and ARGs released into the environment. Nevertheless, the propagation of ARGs and their underlying mechanisms and the dynamics of mobile genetic elements (MGEs) in WWTPs have rarely been investigated in South Korea. In this study, shotgun metagenomic analysis was used to identify comprehensive ARGs and their mechanisms, bacterial communities, and MGEs from 4 configurations with 2 activated sludge (AS) and 2 anaerobic digestion sludge (ADS) samples. A total of 181 ARG subtypes belonging to 22 ARG types were broadly detected, and the ARG abundances in the AS samples were 1.3–2.0 orders of magnitude higher than in the ADS samples. Multidrug and bacitracin resistance genes were the predominant ARG types in AS samples, followed by ARGs against sulfonamide, tetracycline, and β-lactam. However, the composition of ARG types in ADS samples was significantly changed. The abundance of multidrug and β-lactam resistance genes was drastically reduced in the ADS samples. The resistance genes of MLS were the predominant, followed by ARGs against sulfonamide and tetracycline in the ADS samples. In addition, plasmids were the dominant MGEs in the AS samples, while integrons (intI1) were the dominant MGEs in the ADS samples. These results provide valuable information regarding the prevalence of ARG types and MGEs and the difference patterns between the AS and ADS systems.

In the present study, organic waste materials, like coconut shell, orange peels, and banana peels were used to produce activated carbon. Chemical activation was carried out using phosphoric acid (H₃PO₄). The activation temperatures were selected at the range of 200–300 °C. Surface morphology of the different activated carbon derived from the different waste materials was investigated using scanning electron microscope. Pollution removal efficiency of different activated carbons was carried out by Jar test. The jar test was carried out at 120 rpm, at 20 °C temperature for 1 h. Three different sizes; 75 μm, 150 μm and 425 μm, and three concentration; 100 mg/l, 200 mg/l and 500 mg/l of the activated carbon were selected for the pollution removal experiments. Water quality parameters like pH, TSS, and COD were analyzed using standard AWWA/APHA methods to know the pollution removal efficiency. COD removal varies from 48 to 99% in different activated carbon at different size and concentration. TSS removal varies from 43 to 100% by different activated carbon. The highest adsorption was observed by 75 µm activated carbon. Among all the experimented materials activated carbon made from orange peels performed better than others possibly due to the formation of more C–O and C=O functional groups due to the presence of more carbon and oxygen elements than others. This study opens a new way of wastewater treatment in Oman by using low-cost activated carbon made from locally available organic waste and at the same time, it shall help in managing organic waste.

Bacterial communities in wastewater treatment plants (WWTPs) affect plant functionality through their role in the removal of pollutants from wastewater. Bacterial communities vary extensively based on plant operating conditions and influent characteristics. The capacity of WWTPs can also affect the bacterial community via variations in the organic or nutrient composition of the influent. Despite the importance considering capacity, the characteristics that control bacterial community assembly are largely unknown. In this study, we discovered that bacterial communities in WWTPs in Korea and Vietnam, which differ remarkably in capacity, exhibit unique structures and interactions that are governed mainly by the capacity of WWTPs. Bacterial communities were analysed using 16S rRNA gene sequencing and exhibited clear differences between the two regions, with these differences being most pronounced in activated sludge. We found that capacity contributed the most to bacterial interactions and community structure, whereas other factors had less impact. Co-occurrence network analysis showed that microorganisms from high-capacity WWTPs are more interrelated than those from low-capacity WWTPs, which corresponds to the tighter clustering of bacterial communities in Korea. These results will contribute to the understanding of bacterial community assembly in activated sludge processing.