scholarly journals Organic Foulants Characteristics in Membrane Bioreactor

2017 ◽  
Vol 5 (1) ◽  
Author(s):  
R. K. Aryal ◽  
S. Vigneswaran ◽  
J. Lebegue ◽  
H. K. Shon ◽  
J. Kandasamy ◽  
...  
Keyword(s):  
Membrane Bioreactor ◽  
Membrane Surface ◽  
Aeration Rate ◽  
Size Exclusion ◽  
Spectroscopic Techniques ◽  
Exclusion Chromatography ◽  
Naoh Solution ◽  
Bioreactor System ◽  
Microbial Products ◽  
Flat Sheet Membrane

A laboratory scale side stream membrane bioreactor system with flat sheet membrane was operated for 5–days run at three different aeration rates (100, 200 and 300 L/h). The organic foulants deposited on the membrane surface was studied after extraction with 5% NaOH solution using three spectroscopic techniques. The IR spectra showed no distinct similarity in peaks among the three. The fluorescence spectra showed increase of soluble microbial products in foulant with decrease of aeration rate. This was supported by the size exclusion chromatography in which biopolymers concentration in fouling decreased with increasing aeration rate.

scholarly journals Biomass Characteristics and Their Effect on Membrane Bioreactor Fouling

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2867 ◽  
Author(s):  
Petros K. Gkotsis ◽  
Anastasios I. Zouboulis
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Membrane Resistance ◽  
Soluble Microbial Products ◽  
Gelling Properties ◽  
Microbial Products ◽  
Soluble Part

Biomass characteristics are regarded as particularly influential for fouling in Membrane Bio-Reactors (MBRs). They primarily include the Mixed Liquor Suspended Solids (MLSS), the colloids and the Extracellular Polymeric Substances (EPS). Among them, the soluble part of EPS, which is also known as Soluble Microbial Products (SMP), is the most significant foulant, i.e., it is principally responsible for membrane fouling and affects all fundamental fouling indices, such as the Trans-Membrane Pressure (TMP) and the membrane resistance and permeability. Recent research in the field of MBRs, tends to consider the carbohydrate fraction of SMP (SMPc) the most important characteristic for fouling, mainly due to the hydrophilic and gelling properties, which are exhibited by polysaccharides and allow them to be easily attached on the membrane surface. Other wastewater and biomass characteristics, which affect indirectly membrane fouling, include temperature, viscosity, dissolved oxygen (DO), foaming, hydrophobicity and surface charge. The main methods employed for the characterization and assessment of biomass quality, in terms of filterability and fouling potential, can be divided into direct (such as FDT, SFI, TTF100, MFI, DFCM) or indirect (such as CST, TOC, PSA, RH) methods, and they are shortly presented in this review.

Impact of chemical cleaning and air-sparging on the critical and sustainable flux in a flat sheet membrane bioreactor for municipal wastewater treatment

2008 ◽  
Vol 57 (12) ◽  
pp. 1873-1879 ◽  
Author(s):  
G. Guglielmi ◽  
D. Chiarani ◽  
D. P. Saroj ◽  
G. Andreottola
Keyword(s):  
Membrane Bioreactor ◽  
Municipal Wastewater ◽  
Membrane Surface ◽  
Municipal Wastewater Treatment ◽  
Chemical Cleaning ◽  
Critical Flux ◽  
Submerged Membrane Bioreactor ◽  
Flat Sheet ◽  
Exponential Trend ◽  
Flat Sheet Membrane

The paper discusses the experimental optimisation of both chemical and mechanical cleaning procedures for a flat-sheet submerged membrane bioreactor fed with municipal wastewater. Fouling was evaluated by means of the critical flux concept, which was experimentally measured by short-term flux-stepping tests. By keeping constant most important parameters of the biological process (MLSS, sludge age), two different chemical cleaning protocols (2,000 mg L−1 NaOCl and 200 mg L−1 NaOCl) were applied with different frequency and, after approximately 9 months of operation, the criticality threshold was determined under different values of SADm (specific aeration demand per unit of membrane surface area). The weaker and more frequent chemical cleaning regime (200 mg L−1, monthly) proved much more effective than the stronger and less frequent strategy (2,000 mg L−1, once every three months). The improvement of performances was quantified by two TMP-based parameters, the fouling rate and the ΔTMP (difference between TMP values during the increasing and decreasing phase of hysteresis). The best performing configuration was then checked over a longer period by running four long-term trials showing an exponential trend of the sub-critical fouling rate with the imposed flux.

Modification of ASM No.1 for a submerged membrane bioreactor system: including the effects of soluble microbial products on membrane fouling

2003 ◽  
Vol 47 (12) ◽  
pp. 177-181 ◽  
Author(s):  
J. Cho ◽  
K.-H. Ahn ◽  
Y. Seo ◽  
Y. Lee
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Membrane Resistance ◽  
Soluble Microbial Products ◽  
Submerged Membrane Bioreactor ◽  
Operation Conditions ◽  
In Series ◽  
Bioreactor System ◽  
Microbial Products ◽  
Major Factors

In this study, a mathematical model for the submerged membrane bioreactor (SMBR) was developed by combining the activated sludge model (ASM) with a membrane resistance-in-series model. Some modifications were introduced to make ASM to be suitable for describing the characteristics of SMBR. A set of the 1st-order differential equations was established for 13 dependent variables relevant to particles and soluble matters. Performing model simulations for various conditions, the time when a membrane would be fouled could be predicted as well as the effluent quality. From simulation results, F/M ratio and SRT can be considered as major factors of the soluble microbial products (SMP) concentration in a reactor and it is clear that SMP can play an important role in membrane fouling and water quality simultaneously. The model would be very helpful in optimizing operation conditions as well as in designing an optimal SMBR system.

scholarly journals Polymalic Acid Tritryptophan Copolymer Interacts with Lipid Membrane Resulting in Membrane Solubilization

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hui Ding ◽  
Irving Fox ◽  
Rameshwar Patil ◽  
Anna Galstyan ◽  
Keith L. Black ◽  
...  
Keyword(s):  
Lipid Membrane ◽  
Membrane Surface ◽  
Size Exclusion ◽  
Stable Configuration ◽  
Side Chains ◽  
Anionic Polymers ◽  
Polymalic Acid ◽  
Tryptophan Residues ◽  
Exclusion Chromatography ◽  
Abnormal Cells

Anionic polymers with membrane permeation functionalities are highly desirable for secure cytoplasmic drug delivery. We have developed tritryptophan containing copolymer (P/WWW) of polymalic acid (PMLA) that permeates membranes by a mechanism different from previously described PMLA copolymers of trileucine (P/LLL) and leucine ethyl ester (P/LOEt) that use the “barrel stave” and “carpet” mechanism, respectively. The novel mechanism leads to solubilization of membranes by forming copolymer “belts” around planar membrane “packages.” The formation of such packages is supported by results obtained from studies including size-exclusion chromatography, confocal microscopy, and fluorescence energy transfer. According to this “belt” mechanism, it is hypothesized that P/WWW first attaches to the membrane surface. Subsequently the hydrophobic tryptophan side chains translocate into the periphery and insert into the lipid bilayer thereby cutting the membrane into packages. The reaction is driven by the high affinity between the tryptophan residues and lipid side chains resulting in a stable configuration. The formation of the membrane packages requires physical agitation suggesting that the success of the translocation depends on the fluidity of the membrane. It is emphasized that the “belt” mechanism could specifically function in the recognition of abnormal cells with high membrane fluidity and in response to hyperthermia.

scholarly journals Xylan accessibility of bleached eucalypt pulp in alkaline solutions

Holzforschung ◽  
2020 ◽  
Vol 74 (2) ◽  
pp. 141-148 ◽  
Author(s):  
Teresa M.P. Gomes ◽  
António P. Mendes de Sousa ◽  
Yuri I. Belenkiy ◽  
Dmitry V. Evtuguin
Keyword(s):  
Molecular Weight ◽  
Structural Features ◽  
Size Exclusion ◽  
Alkaline Solutions ◽  
One Dimensional ◽  
Maximum Extraction ◽  
Exclusion Chromatography ◽  
Naoh Solution ◽  
Acid Methanolysis ◽  
Kinetics Of

AbstractThe accessibility of glucuronoxylan from a refined, bleached Eucalyptus globulus industrial kraft pulp in 0–18% aqueous NaOH solution at room temperature (25°C) was studied. The extraction profile revealed a maximum extraction of xylan in the pulp at about 10–12% NaOH concentration and was explained by the maximum swelling of the pulp according to the Gibbs-Donnan equilibrium. The kinetics of xylan removal and the monitoring of its structural features were performed at 5 and 10% NaOH concentrations. The maximum yields of xylans with 10% and 5% NaOH were as high as 90% and 60% for 2 h extraction, respectively. The structural features of xylan were assessed by acid methanolysis and one-dimensional (1D)/two-dimensional (2D) nuclear magnetic resonance (NMR), and the molecular weight by size exclusion chromatography (SEC). The xylan extracted with 10% NaOH had a slightly higher molecular weight and a lower branching with uronic moieties than the xylan extracted with 5% NaOH. The former was less pure (contained more β-cellulose) than the latter. Structural studies by NMR resulted in the conclusion that there are at least two types of xylans removed from the pulp: one xylan with relatively high 4-O-methyl-α-D-glucuronosyl [MeGlcA-(1→] and [→2)-MeGlcA-(1→] substituents and another xylan with a much lower substitution with uronic residues.

scholarly journals A pH-dependent bolt involving cytosine bases located in the lateral loops of antiparallel G-quadruplex structures within the SMARCA4 gene promotor

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sanae Benabou ◽  
Stefania Mazzini ◽  
Anna Aviñó ◽  
Ramon Eritja ◽  
Raimundo Gargallo
Keyword(s):  
Base Pair ◽  
Thermodynamic Description ◽  
Size Exclusion ◽  
Spectroscopic Techniques ◽  
G Quadruplex ◽  
Exclusion Chromatography ◽  
Additional Stability ◽  
Gene Promotor ◽  
Ph Dependent ◽  
Melting Experiments

Abstract Some lung and ovarian tumors are connected to the loss of expression of SMARCA4 gene. In its promoter region, a 44-nucleotides long guanine sequence prone to form G-quadruplex structures has been studied by means of spectroscopic techniques (circular dichroism, molecular absorption and nuclear magnetic resonance), size exclusion chromatography and multivariate analysis. The results have shown that the central 21-nucleotides long sequence comprising four guanine tracts of disparate length is able to fold into a pH-dependent ensemble of G-quadruplex structures. Based on acid-base titrations and melting experiments of wild and mutated sequences, the formation of a C·C+ base pair between cytosine bases present at the two lateral loops is shown to promote a reduction in conformational heterogeneity, as well as an increase in thermal stability. The formation of this base pair is characterized by a pKa value of 7.1 ± 0.2 at 20 °C and 150 mM KCl. This value, higher than those usually found in i-motif structures, is related to the additional stability provided by guanine tetrads in the G-quadruplex. To our knowledge, this is the first thermodynamic description of this base pair in loops of antiparallel G-quadruplex structures.

scholarly journals Metallo-celluloses, 1 Synthesis and solution properties of 4-ferrocenylbutylsubstituted cellulose derivatives

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Bettina Laube ◽  
Wolfgang Radke ◽  
Matthias Rehahn ◽  
Winfried Wunderlich
Keyword(s):  
Light Scattering ◽  
Ir Spectroscopy ◽  
Cellulose Triacetate ◽  
Size Exclusion ◽  
Hydroxyl Groups ◽  
Cellulose Derivatives ◽  
Solution Properties ◽  
Cellulose Sample ◽  
Exclusion Chromatography ◽  
Naoh Solution

Abstract An efficient method is described for the simultaneous introduction of 4-ferrocenylbutyl and n-hexyl side groups into cellulose. For this purpose, cellulose triacetate is treated in dimethyl sulfoxide/NaOH solution with mixtures of 4-bromobutylferrocene and n-hexyl bromide. An almost quantitative conversion of the cellulose hydroxyl groups was reached when less than one ferrocene substituent was attached to the cellulose repeating units on average. At higher degrees of ferrocene substitution, some of the cellulose hydroxyl groups seem to remain unsubstituted. This conclusion has been drawn on the basis of size exclusion chromatography (SEC) with online light-scattering detector where coil contraction was observed with increasing ferrocene content in the cellulose sample. This finding was further supported by IR spectroscopy, viscometry, and conventional SEC investigations. We assume that steric hindrance of the bulky side groups is responsible for incomplete conversion.

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