MLSS concentration: Still a poorly understood parameter in MBR filterability

Lousada-Ferreira, Maria; Geilvoet, S.; Moreau, Adrien; Atasoy, Elif; Krzemiński, Paweł; Nieuwenhuijzen, A. van; Graaf, Jhjm van der

doi:10.1016/j.desal.2009.09.036

Cited by 53 publications

(26 citation statements)

References 14 publications

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“…MLSS>10.5 g/L, provides samples with worse filterability. The obtained results are in agreement with our previous work (Lousada-Ferreira et al, 2010) and support the initial hypothesis. The MLSS concentration has a direct impact on sludge viscosity, i.e.…”

Section: Filterability and Cake Layer Parameterssupporting

confidence: 83%

“…One filtration measurement was performed with the original non-diluted sample and the other two with diluted samples. The diluted samples were prepared according to the methodology described in Lousada-Ferreira et al (2010). The experiments were performed with the following goals: (i) set 1 to 22 to characterize the MBR activated sludge; (ii) set 23 to 28 to compare sludge from membrane and aeration tanks, within one full-scale MBR installation; (iii) set 29 to 32 to compare sludge from different MBRs.…”

Section: Methodsmentioning

confidence: 99%

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Impact of suspended solids concentration on sludge filterability in full-scale membrane bioreactors

Lousada-Ferreira

Lier

Graaf³

2015

Journal of Membrane Science

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The relation between activated sludge filterability and mixed liquor suspended solids (MLSS) concentration in membrane bioreactors (MBRs) is framed in a single hypothesis, explaining results seemingly contradictory. A total of 44 activated sludge samples were collected and analyzed on a variety of parameters, i.e. filterability, MLSS concentration, soluble microbial products (SMP) concentrations and particle size distribution in the range of 2-100 μm and of 0.4-5.0 μm. The sludge filterability was assessed by using the Delft Filtration Characterization method (DFCm). In order to investigate the impact of MLSS concentration, identical samples were diluted with permeate. Results showed that dilution of the samples led to an increased activated sludge filterability, but only when the starting MLSS concentration was below the apparent critical value of 10.5 g/L. As opposed, the filterability of sludge with MLSS concentrations above 10.5 g/L, and which was characterized by a moderate to good filtration quality, i.e. R 20 <1 [x10 12 m -1 ], worsened when diluted. The specific resistance times the particle concentration of a cake layer obtained when filtrating sludge of moderate to good filterability and MLSS concentration above the apparent critical value, was 5.5 times smaller compared to the cake layer of sludge with MLSS concentration below the critical value. Results from SMP assessment and particle counting in the range 2-100 µm showed that reduction in sludge mass and de-flocculation occurred, upon dilution of all samples. However, when diluting sludge samples with MLSS concentrations exceeding 10.5 g/L and which were characterized by a moderate to good filtration characteristics, there was also release of particles below 0.4 µm, opposite to dilutions of samples with MLSS concentrations below 10.5 g/L. We postulate that sludge, which is characterized by a moderate to good filterability, having an MLSS concentration above the apparent critical value of 10.5 g/L, is likely to retain particles smaller than 0.4 μm in its mass, as opposed to sludge with MLSS concentration below the apparent critical value. Our work indicates that there are optimal MLSS concentration ranges in MBR technology, to promote good filterable sludge quality in order to avoid fouling.

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Section: Filterability and Cake Layer Parameterssupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Impact of suspended solids concentration on sludge filterability in full-scale membrane bioreactors

Lousada-Ferreira

Lier

Graaf³

2015

Journal of Membrane Science

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“…In the review paper of Le-Clech et al [5], it is noticed that some authors report an increasing biomass concentration as a positive impact on membrane fouling, whereas others report a negative correlation whilst yet another group finds the influence of MLSS insignificant. More recently, also the existence of an optimal MLSS concentration range is suggested [6]. The lack of a clear correlation between MLSS concentration, which is basically the simplest parameter to measure, and any other foulant characteristics indicates that the MLSS concentration (alone) is a poor indicator for biomass fouling propensity [5].…”

Section: Biomass Concentration or Mixed Liquor Suspended Solids (Mlss)mentioning

confidence: 99%

“…Ten different MBRs in Belgium and the Netherlands, treating both municipal (4) and industrial (6) wastewaters, were sampled in both winter and summer. The Delft Filtration Characterization method (DFCm) was chosen to determine activated sludge filterability [14], instead of calculating sludge properties from process permeability, i.e., flux and TMP, in each installation.…”

Section: Extracellular Polymeric Substances (Eps)mentioning

confidence: 99%

Activated sludge characteristics affecting sludge filterability in municipal and industrial MBRs: Unraveling correlations using multi-component regression analysis

Broeck

Krzemiński

Dierdonck

et al. 2011

Journal of Membrane Science

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a b s t r a c tIn the field of membrane bioreactors (MBRs) many membrane fouling related questions still remain unanswered. The goal of this research is to unveil some of the black-box features of activated sludge filterability by correlating the results from activated sludge filterability measurements following the Delft Filtration Characterization method (DFCm) with a large set of activated sludge characteristics. Ten different MBRs in Belgium and the Netherlands were sampled in both winter and summer. All samples were subjected to the DFCm, automated image analysis and an extensive set of standardized measurements. No clear correlation could be found between a single sludge parameter and activated sludge filterability. However, a combination of sludge morphology and relative hydrophobicity (RH) allows for a clear classification of activated sludge into two classes, i.e., bad and poor to good, implying that deflocculation and a low RH have a negative impact on activated sludge filterability. Furthermore, for sludge samples having poor to good filterability, accurate estimations of sludge filterability can be made when including more parameters. The main conclusion is that filterability can be predicted by analyzing the bioflocculation state of the activated sludge.

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“…This can change the particulate structure or release polymers. Samples originally above 10 g/L showed worse filterability when diluted because many small particles (<10-20 m) were formed by deflocculation [106].…”

Section: 123mentioning

confidence: 99%

Membrane fouling in membrane bioreactors—Characterisation, contradictions, cause and cures

Drews

2010

Journal of Membrane Science

799

329

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MLSS concentration: Still a poorly understood parameter in MBR filterability

Cited by 53 publications

References 14 publications

Impact of suspended solids concentration on sludge filterability in full-scale membrane bioreactors

Impact of suspended solids concentration on sludge filterability in full-scale membrane bioreactors

Activated sludge characteristics affecting sludge filterability in municipal and industrial MBRs: Unraveling correlations using multi-component regression analysis

Membrane fouling in membrane bioreactors—Characterisation, contradictions, cause and cures

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