Membrane types are known to have a decisive effect on the operational efficiency of membrane-bound reactors. The gas-permeable membrane, serving as the biofilm growth and oxygen transfer medium, plays a vital role in the membrane-aerated biofilm reactor (MABR). However, few studies have thoroughly investigated how membrane types affect MABR performance. Four parallel MABRs were equipped with different membrane types: microporous PTFE (R1), dense silicone (R2), composite A (R3), and composite B (R4) membranes. Results showed that the R3 and R4 exhibited comparable and superior COD and nitrogen removal efficiency relative to R1, maintaining stable transmembrane pressure. XDLVO theory was used to assess the interfacial interaction energy between sludge flocs and membrane surfaces. Polar forces were crucial for sludge adhesion, affecting biofilm formation and growth. Composite B exhibited the lowest energy barrier (2529 KT), leading to the fastest biofilm formation and thicker biofilms, which enhance nitrogen removal. PTFE exhibited the highest energy barrier (9655 KT), resulting in the most extended biofilm cultivation period and the thinnest biofilm. Based on fluorescent in-situ hybridization (FISH), membrane types significantly affect the distribution of nitrogen-removing microbial communities. As the biofilm thickened, the stratification of the nitrifying bacterial population became increasingly pronounced, forming distinct layers within the biofilm. Nitrosomonas and Nitrobacter dominated the biofilm near the membrane, while Nitrospira was most abundant in the outer biofilm. The outermost biofilm layer was predominantly composed of heterotrophic denitrifying bacteria (HDB). The research has shown that different biofilm types exhibit heterogeneity stratification in nitrifying bacteria and HDB. 16S rRNA genes sequencing revealed that Nitrospira was the predominant nitrifying genus within the heterotrophic/autotrophic biofilm.
To investigate the effect of oil droplets surface film type and droplets size on the physicochemical properties and digestibility of thermally induced ovalbumin–oil emulsion gels, Tween 80 and ovalbumin were selected as individual emulsifiers for the emulsification of sunflower oil at different homogenization speeds (6000, 8000, and 10000 rpm), and the formed emulsions were mixed with ovalbumin matrix solution and then heated to form heat-induced ovalbumin emulsion gels (OEG). The OEG with ovalbumin as emulsifier had higher hardness, water holding capacity (WHC), and surface hydrophobicity, and lower digestibility, spin−spin relaxation time ( T 2 ) and free sulfhydryl content than those of the OEG with Tween 80 as the emulsifier ( p < 0.05). As the oil droplets size decreased, the hardness increased, WHC increased, the amide A band shifted to lower wavenumbers, digestibility decreased, T 2 decreased, free sulfhydryl content decreased, and surface hydrophobicity increased for both OEG ( p < 0.05). These results collectively indicated that the physicochemical properties of the OEG are influenced by the property of the oil interfacial film and the size of the oil droplets. The oil droplets surrounded by the interfacial protein film improved the performance of the OEG greatly, and the proteins within its OEG formed a dense gel network structure through hydrophobic aggregation, disulfide bond crosslinking, and hydrogen bonding. The oil droplets with smaller sizes favored the enhancement in the physicochemical properties of the OEG. Changes in the size of oil droplets and the type of film wrapped around them regulated the digestibility of the OEG.
危险品化学品经营许可证（带存储）