Influence of loosely bound extracellular polymeric substances (EPS) on the flocculation, sedimentation and dewaterability of activated sludge

Li, X.Y.; Yang, Shu-Fang

doi:10.1016/j.watres.2006.06.037

Cited by 1,729 publications

(564 citation statements)

References 25 publications

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“…Murthy and Novak (1999) suggested that high proteins/polysaccharide ratio was detrimental for sludge dewatering performance. Recent years, EPS was found to have double layers including the loosely bound EPS (LB-EPS) which is diffused from the tightly bound EPS (TB-EPS) that surrounds the cells (Li and Yang, 2007;Poxon and Darby, 1997;Ramesh et al, 2006). Moreover, some researchers reported that only the LB-EPS was related to the sludge dewaterability (Li and Yang, 2007;Ramesh et al, 2006;Raynaud et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Recent years, EPS was found to have double layers including the loosely bound EPS (LB-EPS) which is diffused from the tightly bound EPS (TB-EPS) that surrounds the cells (Li and Yang, 2007;Poxon and Darby, 1997;Ramesh et al, 2006). Moreover, some researchers reported that only the LB-EPS was related to the sludge dewaterability (Li and Yang, 2007;Ramesh et al, 2006;Raynaud et al, 2012). Yu et al (2008) suggested that sludge floc was composed by five fractions: supernatant, slime, LB-EPS, TBEPS, and pellet, and the sludge dewatering performance was mainly influenced by soluble EPS characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation

et al. 2016

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a b s t r a c tThe effects of combined calcium peroxide (CaO 2 ) oxidation with chemical re-flocculation on dewatering performance and physicochemical properties of waste activated sludge was investigated in this study. The evolutions of extracellular polymeric substances (EPS) distribution, composition and morphological properties were analyzed to unravel the sludge conditioning mechanism. It was found that sludge filtration performance was enhanced by calcium peroxide oxidation with the optimal dosage of 20 mg/ gTSS. However, this enhancement was not observed at lower dosages due to the absence of oxidation and the performance deteriorated at higher dosages because of the release of excess EPS, mainly as proteinlike substances. The variation in soluble EPS (SEPS) component can be fitted well with pseudo-zero-order kinetic model under CaO 2 treatment. At the same time, extractable EPS content (SEPS and loosely bound EPS (LB-EPS)) were dramatically increased, indicating sludge flocs were effectively broken and their structure became looser after CaO 2 addition. The sludge floc structure was reconstructed and sludge dewaterability was significantly enhanced using chemical re-flocculation (polyaluminium chloride (PACl), ferric iron (FeCl 3 ) and polyacrylamide (PAM)). The inorganic coagulants performed better in improving sludge filtration dewatering performance and reducing cake moisture content than organic polymer, since they could act as skeleton builders and decrease the sludge compressibility.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation

et al. 2016

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“…This observation was in agreement with Murtgy and Novak's findings (1999). Recently, Li and Yang (2007) suggested that the spatial distribution and chemical compostion of EPS had more significant effects on sludge dewatering property, and sludge dewatering performance was mainly dependent on content of loosely-bound EPS (LB-EPS) rather than that of tightly bound EPS (TB-EPS). Furhter, Yu et al (2008) demonstrated that soluble EPS also played an important role in sludge dewatering process.…”

Section: Introductionmentioning

confidence: 99%

Improvement of wastewater sludge dewatering performance using titanium salt coagulants (TSCs) in combination with magnetic nano-particles: Significance of titanium speciation

et al. 2017

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a b s t r a c tIn this study, the effects of chemical conditioning using titanium salt coagulants (TSCs) of different hydrolysis speciation in combination with magnetic nano-particles on dewatering performance of waste activated sludge were evaluated by means of specific resistance to filtration (SRF) and capillary suction time (CST). The morphological and extracellular polymeric substances (EPS) properties under chemical conditioning were investigated in detail to understand the reaction mechanisms involved. The results showed that the TSC with basicity of 0.5 performed better in improving sludge dewatering performance than other TSCs. Sludge floc formed by TSC 0.5 treatment was characterized by larger floc size and higher floc strength than that conditioned by other TSCs. EPS compression and densification were the major mechanisms of sludge conditioning, and TSC 0.5 had better performance in compressing EPS structure. In addition, reduction of soluble EPS concentration, especially protein-like substances contributed to improvement of sludge filterability under conditioning. Furthermore, addition of Fe 2 O 3 nanoparticles could further improve dewatering performance and decrease compressibility of sludge system by acting as skeleton builders and enhancing floc strength. The sludge particles aggregation efficiency was effectively improved with addition of nano-Fe 2 O 3 . They also were able to bind with protein-like substance in EPS component, which might contribute to promotion of sludge filterability.

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“…The microorganisms are embedded in a matrix of extracellular polymeric substances (EPS) can be regarded as key constituents in the dewatering process of sludge (Mikkelsen and Keiding, 2002). EPS (EPS and water held within the EPS structure) accounts for 80% of the mass of waste activated sludge, and it has double layers including the loosely bound EPS (LB-EPS) which is diffused from the tightly bound EPS (TB-EPS) that surrounds the cells, and it was found sludge dewaterability was only associated with LB-EPS fraction (Li and Yang, 2007;Ramesh et al, 2006). Moreover, the water retained in the EPS-structure is bound mainly by the polysaccharides (PS) and proteins (PN) of the EPS in the activated sludge.…”

Section: Introductionmentioning

confidence: 99%

Wastewater sludge dewaterability enhancement using hydroxyl aluminum conditioning: Role of aluminum speciation

et al. 2016

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a b s t r a c tChemical conditioning is one of the most important processes for improve the performance of sludge dewatering device. Aluminum salt coagulant has been widely used in wastewater and sludge treatment. It is generally accepted that pre-formed speciation of aluminum salt coagulants (ASC) has an important influence on coagulation/flocculation performance. In this study, the interaction mechanisms between sludge particles and aluminum salt coagulants with different speciation of hydroxy aluminum were investigated by characterizing the changes in morphological and EPS properties. It was found that middle polymer state aluminum (Al b ) and high polymer state aluminum (Al c ) performed better than monomer aluminum and oligomeric state aluminum (Al a ) in reduction of specific resistance to filtration (SRF) and compressibility of wastewater sludge due to their higher charge neutralization and formed more compact flocs. Sludge was significantly acidified after addition Al a , while pH was much more stable under Al b and Al c conditioning due to their hydrolysis stability. The size of sludge flocs conditioned with Al b and Al c was small but flocs structure was denser and more compact, and floc strength is higher, while that formed from Al a is relatively large, but floc structure was loose, floc strength is relatively lower. Scanning environmental microscope analysis revealed that sludge flocs conditioned by Al b and Al c (especially PAC 2.5 and Al 13 ) exhibited obvious botryoidal structure, this is because sludge flocs formed by Al b and Al c were more compact and floc strength is high, it was easy generated plentiful tiny channels for water release. In addition, polymeric aluminum salt coagulant (Al b , Al c ) had better performance in compressing extracellular polymeric substances (EPS) structure and removing sticky protein-like substances from soluble EPS fraction, contributing to improvement of sludge filtration performance. Therefore, this study provides a novel solution for improving sludge dewatering property by controlling aluminum speciation.

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Influence of loosely bound extracellular polymeric substances (EPS) on the flocculation, sedimentation and dewaterability of activated sludge

Cited by 1,729 publications

References 25 publications

Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation

Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation

Improvement of wastewater sludge dewatering performance using titanium salt coagulants (TSCs) in combination with magnetic nano-particles: Significance of titanium speciation

Wastewater sludge dewaterability enhancement using hydroxyl aluminum conditioning: Role of aluminum speciation

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