Role Mechanism of Extracellular Polymeric Substances in the Formation of Aerobic Granular Sludge
胞外多聚物在好氧颗粒污泥形成中的作用机制

During the aerobic granulation of activated sludge in SBR, the changes in the key components of sludge EPS (extracellular polymeric substances) and surface characteristics, and the correlation between them were analyzed. The SDS-PAGE results of exopolymeric protein for different sludge samples indicated that the distribution of bands for protein molecular weight was in the range of 31.0 x 10(3) - 97.4 x 10(3). Compared with seed sludge, some new protein bands increased with the aerobic granulation, and the color of the bands were enhanced, indicating the species and contents of exopolymeric protein gradually increased with the granulation. Moreover the quantitative determination indicated that the protein excreted increased from 49.4 mg x g(-1) to 148.3 mg x g(-1) with the granulation. There was no obvious increase in the polysaccharide content. The PN/PS ratio was increased from to 2.3 to 4.9 accordingly. The cell hydrophobicity of aerobic granular sludge was 1 time higher than that of seed sludge. The changes in cell hydrophobicity were positively correlated with PN/PS values, and the related coefficient was 0.969. The average Zeta potential of seed sludge and granular sludge was -28.5 mV and -13.2 mV, respectively. Obviously, the surface negative charges of granular sludge decreased. From the protein characteristics, we speculate the increase in exopolymeric protein content may enhance cell relative hydrophobicity and reduce negative surface charges, thus contributing to aerobic granulation.