Characteristics of extracellular polymeric substances (EPS) fractions from excess sludges and their effects on bioflocculability |
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Authors: | Guang-Hui Yu Pin-Jing HeLi-Ming Shao |
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Institution: | State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China |
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Abstract: | Extracellular polymeric substances (EPS) of biological origin are ubiquitous in excess sludges and can be applied as an underlying bioflocculant, owing to their high content of macromolecules and cations. However, low flocculating activity limits the feasibility of their practical applications. This study provides a novel EPS fractionation approach to improve their flocculability by extracting an active EPS fraction and removing the others with low flocculability. The results showed that for two excess sludges (called sludge A and sludge B), the tightly bound EPS (TB-EPS) fraction possessed a high flocculating rate to kaolin suspension compared with the other EPS fractions i.e., supernatant, slime, and loosely bound EPS (LB-EPS) fraction] (>54.1 ± 1.4% vs <7.8 ± 1.6%). High bioflocculability of TB-EPS fraction could be attributable to high contents of macromolecules (330–1200 kDa) and trivalent cations (Fe3+ and Al3+). Further investigation reveals that the TB-EPS fraction caused aggregation of particles by bridging and sweep flocculation. |
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Keywords: | Bioflocculant Excess sludges Extracellular polymeric substances Flocculability Fractionation |
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