Enhanced performance of aerobic granular sludge-membrane system through the utilization of different iron-based nano-metal oxides for mitigating membrane fouling

Fe 3 O 4 , γ-Fe 2 O 3 , and α-Fe 2 O 3 nanoparticles play a crucial role in influencing the adsorption capacity and pretreatment efficacy as iron-based nano-metal oxides due to their distinct structural and physicochemical properties. However, the impact of these adsorbents on membrane filtration efficiency remains unexplored. This study aimed to investigate the influence of these three adsorbents on membrane fouling in an aerobic granular sludge–membrane system (AGSMS) used for municipal wastewater reuse treatment. The results demonstrated that under optimal conditions, γ-Fe 2 O 3 exhibited superior effectiveness in removing low and medium molecular weight contaminants from wastewater, resulting in a higher normalized flux (0.59) and reduced total fouling resistance (2.66 × 10 11  m −1 ). It also showed the highest removal rate for organic matter and suspended solids, making it particularly effective in mitigating AGSMS membrane fouling. However, excessive addition (2 g/L) of Fe 3 O 4 , γ-Fe 2 O 3 , and α-Fe 2 O 3 could potentially hinder the proper operation of the AGSMS. Pre-adsorption facilitated the formation of a porous cake layer while inhibiting standard blocking behavior. Additionally, the extended Derjaguin–Landau–Verwey–Overbeek theory analysis revealed a substantial energy barrier between membrane-foulant interactions (125.65 kT) as well as foulant-foulant interactions (62.06 kT) within the γ-Fe 2 O 3 system, confirming its exceptional antifouling characteristics. This study offers valuable insights into the selection of iron oxide adsorbents for membrane fouling mitigation and wastewater reuse.