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Dynamic Membrane Formation in Anaerobic Dynamic Membrane Bioreactors: Role of Extracellular Polymeric Substances.

Yu H, Wang Z, Wu Z, Zhu C - PLoS ONE (2015)

Bottom Line: Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis.Further investigations by confocal laser scanning microscopy (CLSM) analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM.The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.

ABSTRACT
Dynamic membrane (DM) formation in dynamic membrane bioreactors plays an important role in achieving efficient solid-liquid separation. In order to study the contribution of extracellular polymeric substances (EPS) to DM formation in anaerobic dynamic membrane bioreactor (AnDMBR) processes, EPS extraction from and re-addition to bulk sludge were carried out in short-term filtration tests. DM formation behaviors could be well simulated by cake filtration model, and sludge with EPS re-addition showed the highest resistance coefficient, followed by sludge after EPS extraction. The DM layers exhibited a higher resistance and a lower porosity for the sludge sample after EPS extraction and for the sludge with EPS re-addition. Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis. Further investigations by confocal laser scanning microscopy (CLSM) analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM. The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

No MeSH data available.


Related in: MedlinePlus

Fouling resistance with time at different TMPs.(A) 10 kPa, (B) 20 kPa, (C) 30 kPa. Error bars represent standard deviations of triplicate tests.
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pone.0139703.g001: Fouling resistance with time at different TMPs.(A) 10 kPa, (B) 20 kPa, (C) 30 kPa. Error bars represent standard deviations of triplicate tests.

Mentions: DM forming behaviors were investigated in short-term filtration tests, and fouling resistances of sludge samples at various TMPs are shown in Fig 1. The evolution of fouling resistance was well fitted by Eq (6) (Table 1). All the R2 values in the fitting results of cake filtration model were higher than 0.90, and regression analysis was significant at 0.05 level, demonstrating that all the DM formation behaviors in our study can be simulated by cake filtration model on the mesh surface. At each TMP, fouling resistances of sludge samples increased with time (Fig 1), indicating that cake layers kept growing during the filtration. Hwang et al. [31] observed that particle fouling behaviours in dead-end filtration using MF membrane changed with filtration time. In their case, particle fouling was caused by pore blocking at the first stage and cake formation at the second stage. The DM formation mechanisms in our study were different from microfiltration membrane fouling mechanisms. Based on one-way ANOVA, fouling resistances of AS0 (raw sludge) and AS1 exhibited no notable differences at each TMP (p = 0.832, 0.215 and 0.807 at 10, 20 and 30 kPa, respectively), indicating sludge after supernatant decantation had no obvious distinctions in DM formation. However, for the rest sludge samples, fouling resistances under the same TMP and filtration time, followed the order of AS3 > AS2 > AS1, suggesting that sludge after bound EPS extraction had a higher fouling rate. After EPS re-addition, the fouling rate appeared even higher. Meanwhile, similar results were observed in terms of resistance coefficient (k) values (Table 1). The differences of k values between AS0 and AS1 are also not significant according to t-test (p = 0.736), and k values of different sludge samples (Table 1) follow the order of AS3 > AS2 > AS1. In DM formation, higher fouling rate and resistance coefficient led to higher DM formation efficiency. Fouling potential of sludge after EPS extraction was higher than that before EPS extraction, and it became even larger with re-addition of EPS, indicating that re-added EPS were favorable for DM formation. In the following sections, comparisons of AS1, AS2 and AS3 will be analyzed in detail to investigate the role of EPS in DM formation.


Dynamic Membrane Formation in Anaerobic Dynamic Membrane Bioreactors: Role of Extracellular Polymeric Substances.

Yu H, Wang Z, Wu Z, Zhu C - PLoS ONE (2015)

Fouling resistance with time at different TMPs.(A) 10 kPa, (B) 20 kPa, (C) 30 kPa. Error bars represent standard deviations of triplicate tests.
© Copyright Policy
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4593540&req=5

pone.0139703.g001: Fouling resistance with time at different TMPs.(A) 10 kPa, (B) 20 kPa, (C) 30 kPa. Error bars represent standard deviations of triplicate tests.
Mentions: DM forming behaviors were investigated in short-term filtration tests, and fouling resistances of sludge samples at various TMPs are shown in Fig 1. The evolution of fouling resistance was well fitted by Eq (6) (Table 1). All the R2 values in the fitting results of cake filtration model were higher than 0.90, and regression analysis was significant at 0.05 level, demonstrating that all the DM formation behaviors in our study can be simulated by cake filtration model on the mesh surface. At each TMP, fouling resistances of sludge samples increased with time (Fig 1), indicating that cake layers kept growing during the filtration. Hwang et al. [31] observed that particle fouling behaviours in dead-end filtration using MF membrane changed with filtration time. In their case, particle fouling was caused by pore blocking at the first stage and cake formation at the second stage. The DM formation mechanisms in our study were different from microfiltration membrane fouling mechanisms. Based on one-way ANOVA, fouling resistances of AS0 (raw sludge) and AS1 exhibited no notable differences at each TMP (p = 0.832, 0.215 and 0.807 at 10, 20 and 30 kPa, respectively), indicating sludge after supernatant decantation had no obvious distinctions in DM formation. However, for the rest sludge samples, fouling resistances under the same TMP and filtration time, followed the order of AS3 > AS2 > AS1, suggesting that sludge after bound EPS extraction had a higher fouling rate. After EPS re-addition, the fouling rate appeared even higher. Meanwhile, similar results were observed in terms of resistance coefficient (k) values (Table 1). The differences of k values between AS0 and AS1 are also not significant according to t-test (p = 0.736), and k values of different sludge samples (Table 1) follow the order of AS3 > AS2 > AS1. In DM formation, higher fouling rate and resistance coefficient led to higher DM formation efficiency. Fouling potential of sludge after EPS extraction was higher than that before EPS extraction, and it became even larger with re-addition of EPS, indicating that re-added EPS were favorable for DM formation. In the following sections, comparisons of AS1, AS2 and AS3 will be analyzed in detail to investigate the role of EPS in DM formation.

Bottom Line: Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis.Further investigations by confocal laser scanning microscopy (CLSM) analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM.The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.

ABSTRACT
Dynamic membrane (DM) formation in dynamic membrane bioreactors plays an important role in achieving efficient solid-liquid separation. In order to study the contribution of extracellular polymeric substances (EPS) to DM formation in anaerobic dynamic membrane bioreactor (AnDMBR) processes, EPS extraction from and re-addition to bulk sludge were carried out in short-term filtration tests. DM formation behaviors could be well simulated by cake filtration model, and sludge with EPS re-addition showed the highest resistance coefficient, followed by sludge after EPS extraction. The DM layers exhibited a higher resistance and a lower porosity for the sludge sample after EPS extraction and for the sludge with EPS re-addition. Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis. Further investigations by confocal laser scanning microscopy (CLSM) analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM. The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

No MeSH data available.


Related in: MedlinePlus