Adsorption/desorption between nanoparticles and aerobic granular sludge: influences of sludge concentration, granule...

The global concern regarding nanopollutant pollution stems from its long-term threat to ecosystems and public health. This study systematically investigated the effect of key parameters on nanoparticles (NPs) adsorption in aerobic granular sludge (AGS) systems, such as mixed liquid suspended solids (MLSS), granule size, aeration/mechanical mixing intensity, and the fate of NPs in Nereda® process were also investigated. The results showed that NPs adsorption by AGS followed the first-order kinetics during aeration, the NPs adsorption capacity was negatively correlated with MLSS and granule size (r = -0.510, r = -0.405), but positively correlated with mechanical mixing intensity (r = 0.320). Fourier-transform infrared spectroscopy analysis revealed that the outer and inner surface of AGS mainly consisted of lipid and protein groups, which affected the adsorption performance. When the NPs were adsorbing by sludge mixture, the flocs and small granules would take the adsorption effect firstly, but the final adsorption performance was not affected. When the influent NPs was 143.79 μg L^-1, 94.60-98.67 % NPs would be adsorbed by sludge mixture in each Nereda® cycle, and desorption efficiencies were smaller than 5.0 % during both plug-flow feeding and aeration phases. This study revealed how operational parameters affect NPs adsorption by AGS and evaluated the interception rate of NPs in Nereda system, providing insights into NPs management for further wastewater treatment.