scholarly journals Effect of heat treatment on fouling resistance and the rejection of small and neutral solutes by reverse osmosis membranes

2014 ◽  
Vol 15 (3) ◽  
pp. 510-516 ◽  
Author(s):  
Takahiro Fujioka ◽  
Nagayasu Oshima ◽  
Ryoichi Suzuki ◽  
Michael Higgins ◽  
William E. Price ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Reverse Osmosis ◽  
Free Volume ◽  
Membrane Fouling ◽  
Volume Fraction ◽  
Membrane Surface ◽  
Feed Solution ◽  
Membrane Properties ◽  
Permeate Flux ◽  
Fouling Resistance

The effects of heat treatment on membrane fouling resistance and the rejection of small and neutral solutes by reverse osmosis (RO) membranes were elucidated. RO membrane modification by heat treatment reduced fouling and improved boron rejection. However, heat treatment also caused a decrease in the water permeability of RO membranes. Significant improvement on fouling resistance by heat treatment was observed when RO concentrate was used to simulate a feed solution with high fouling propensity. The improved fouling resistance is likely to be due to changes in the hydrophobic interaction between the membrane surface and foulants. Boron rejection by the ESPA2 membrane was enhanced by heat treatment from 26 to 68% (when evaluated at the permeate flux of 20 L/m2 h). Positron annihilation lifetime spectroscopy revealed that heat treatment did not significantly influence the free-volume hole-radius of the membrane active skin layer. The results reported in this study suggested that changes in the other membrane properties such as free-volume fraction and thickness may be the main cause improving boron rejection.

scholarly journals Oil Deposition on Polymer Brush-Coated NF Membranes

Membranes ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 168 ◽  
Author(s):  
Anh Vu ◽  
Naama Segev Mark ◽  
Guy Z. Ramon ◽  
Xianghong Qian ◽  
Arijit Sengupta ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Polymer Brush ◽  
Operating Mode ◽  
Feed Solution ◽  
Polymer Chains ◽  
Membrane Properties ◽  
Solution Temperature ◽  
Oil Droplets ◽  
Grafted Polymer

Membrane-based processes are attractive for treating oily wastewaters. However, membrane fouling due to the deposition of oil droplets on the membrane surface compromises performance. Here, real-time observation of the deposition of oil droplets by direct confocal microscopy was conducted. Experiments were conducted in dead-end and crossflow modes. Base NF 270 nanofiltration membranes as well as membranes modified by grafting poly(N-isopropylacrylamide) chains from the membrane surface using atom transfer radical polymerization were investigated. By using feed streams containing low and high NaCl concentrations, the grafted polymer chains could be induced to switch conformation from a hydrated to a dehydrated state, as the lower critical solution temperature for the grafted polymer chains moved above and below the room temperature, respectively. For the modified membrane, it was shown that switching conformation of the grafted polymer chains led to the partial release of adsorbed oil. The results also indicate that, unlike particles such as polystyrene beads, adsorption of oil droplets can lead to coalescence of the adsorbed oil droplets on the membrane surface. The results provide further evidence of the importance of membrane properties, feed solution characteristics, and operating mode and conditions on membrane fouling.

scholarly journals Performance of integrated sequencing batch reactor (SBR) and reverse osmosis (RO) process for leachate treatment: effect of pH

2022 ◽  
Author(s):  
Izabela Anna Tałałaj
Keyword(s):  
Organic Matter ◽  
Reverse Osmosis ◽  
Membrane Fouling ◽  
Removal Rate ◽  
Membrane Surface ◽  
Ammonia Nitrogen ◽  
Electrostatic Repulsion ◽  
Permeate Flux ◽  
Leachate Treatment ◽  
Good Efficiency

Abstract Purpose In this paper the performance and effectiveness of the reverse osmosis (RO) process for the biologically pretreated leachate was investigated. The RO process was carried out separately for two different pH: 8.0 and 9.3. Methods A general pollution parameters as well as organic and inorganic indicators were determined in raw, biologically pretreated and RO treated leachate. The performance characteristics of the reverse osmosis system were made on the basis of permeate flux, electroconductivity removal rate, concentration factor and efficiency in removal of analyzed parameters. Results The use of SBR pretreatment had very good efficiency in BOD (97.3%) and ammonia nitrogen (95.4%) removal. The lowest effectivity was observed for chloride (11.6%), boron (3.9%) and TDS (1.2%). Pretreated leachate was subjected to RO system. The normalized average flux was 0.53 (42.3 L/m2·h) for pH = 8.0 and 0.68 (33.5 L/m2·h) for pH = 9.3. The lower membrane fouling at higher pH can be explained by electrostatic repulsion between the negatively charged membrane surface and organic substances. Independently of the process pH, a two-step membrane fouling was observed. The greatest differences in removal rates were observed for boron, which had a higher retention rate at higher pH, and ammonia nitrogen, whose removal rate decreased at higher pH. The obtained permeate pH after RO process was lower than the feed pH in two analyzed value of pH. Conclusions The higher flux value at pH = 9.3 is result of high content of organic matter in leachate, which is better rejected at higher pH because of higher electrostatic repulsion between organic matter and membrane surface. This indicates that the organic matter content should be taken into account when determining the operating parameters (pH values) of the RO system.

scholarly journals Modification of a polyamide reverse osmosis membrane by heat treatment for enhanced fouling resistance

2013 ◽  
Vol 13 (6) ◽  
pp. 1553-1559 ◽  
Author(s):  
Takahiro Fujioka ◽  
Long D. Nghiem
Keyword(s):  
Heat Treatment ◽  
Reverse Osmosis ◽  
Membrane Surface ◽  
Pure Water ◽  
Surface Characteristics ◽  
Skin Layer ◽  
Secondary Effluent ◽  
Fouling Resistance ◽  
Flux Decline ◽  
Ro Membrane

The use of heat treatment to improve solute rejection and fouling resistance of a polyamide reverse osmosis (RO) membrane was investigated in this study. Heat treatment was carried out by immersing the membrane samples in Milli-Q water at 70 °C for a specific duration. Heat treatment (24 h) reduced the pure water permeability from 4.1 to 2.8 L/m2hbar but improved conductivity rejection from 95.5 to 97.0%. As a result, a correlation was observed between changes in the two parameters. Marginal changes in the membrane surface characteristics (i.e. zeta potential, hydrophobicity, chemistry and roughness) were observed as a result of heat treatment. Heat treatment significantly improved the fouling resistance property of the RO membrane. When the secondary effluent was filtrated at an elevated permeated flux, the virgin RO membrane exhibited 30% flux decline while the heat-treated membrane showed only 12% flux decline. This is possibly because heat treatment resulted in a denser cross-linked active skin layer, thus reducing the blockage caused by small organic foulants.

scholarly journals Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 493
Author(s):  
Amine Charfi ◽  
Fida Tibi ◽  
Jeonghwan Kim ◽  
Jin Hur ◽  
Jinwoo Cho
Keyword(s):  
Particle Size ◽  
Membrane Fouling ◽  
Direct Contact ◽  
Feed Solution ◽  
Membrane Distillation ◽  
Mixed Solution ◽  
Permeate Flux ◽  
Direct Contact Membrane Distillation ◽  
Organic Fouling ◽  
Specific Cake Resistance

This study aims to investigate the effect of operational conditions on organic fouling occurring in a direct contact membrane distillation (DCMD) system used to treat wastewater. A mixed solution of sodium alginate (SA) and bovine serum albumin (BSA) was used as a feed solution to simulate polysaccharides and proteins, respectively, assumed as the main organic foulants. The permeate flux was observed at two feed temperatures 35 and 50 °C, as well as three feed solution pH 4, 6, and 8. Higher permeate flux was observed for higher feed temperature, which allows higher vapor pressure. At higher pH, a smaller particle size was detected with lower permeate flux. A mathematical model based on mass balance was developed to simulate permeate flux with time by assuming (i) the cake formation controlled by attachment and detachment of foulant materials and (ii) the increase in specific cake resistance, the function of the cake porosity, as the main mechanisms controlling membrane fouling to investigate the fouling mechanism responsible of permeate flux decline. The model fitted well with the experimental data with R2 superior to 0.9. High specific cake resistance fostered by small particle size would be responsible for the low permeate flux observed at pH 8.

scholarly journals Application of forward osmosis in reusing the brackish concentrate produced in reverse osmosis plants with secondary treated wastewater as feed solution: a case study

2016 ◽  
Vol 6 (4) ◽  
pp. 533-543 ◽  
Author(s):  
W. D. Wang ◽  
M. Esparra ◽  
H. Liu ◽  
Y. F. Xie
Keyword(s):  
Reverse Osmosis ◽  
Membrane Fouling ◽  
Water Flux ◽  
Forward Osmosis ◽  
Pump Energy ◽  
Feed Solution ◽  
Disinfection Byproducts ◽  
Treated Wastewater ◽  
Membrane Flux ◽  
Flux Decline

This study evaluated the feasibility of forward osmosis (FO) in diluting and reusing the concentrate produced in a reverse osmosis (RO) plant in James City County, VA. Secondary treated wastewater (STW) was used as the feed solution. Findings indicated that pH had slight effects on the water flux of the FO membrane. As the concentration of total dissolved solids (TDS) in the concentrate was diluted from 12.5 to 1.0 g/L or the temperature in the STW decreased from 23 to 10 °C, the membrane flux decreased from 2.2 to 0.59 and 0.81 L/(m2 h), respectively. The FO membrane showed a good performance in the rejection of organic pollutants, with only a small part of the protein-like substances and disinfection byproducts permeating to the diluted concentrate. During an 89-hour continuous operation, water flux decline due to membrane fouling was not observed. Controlling the TDS in the second-stage FO effluent at 1.5 g/L, approximately 8.3% of the pump energy input could be saved. The consumption of groundwater was reduced from 22.7 × 103 to 10.6 × 103 m3/d. FO was proved to be an effective method in both diluting the discharged concentrate and reducing the energy consumption of RO.

Electroflocculation as potential pretreatment in colloid ultrafiltration

2006 ◽  
Vol 6 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Harif ◽  
M. Hai ◽  
A. Adin
Keyword(s):  
Membrane Fouling ◽  
Colloidal Suspension ◽  
Membrane Surface ◽  
Constant Current ◽  
Permeate Flux ◽  
Batch Mode ◽  
Membrane Behavior ◽  
Flux Decline ◽  
Stainless Steel Cathode ◽  
Marginal Improvement

Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06–0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

Topology Optimization of Spacers for Maximizing Permeate Flux on Membrane Surface in Reverse Osmosis Channel

2011 ◽  
Author(s):  
Seungjae Oh ◽  
Semyung Wang ◽  
Minkyu Park ◽  
Joonha Kim
Keyword(s):  
Topology Optimization ◽  
Pressure Drop ◽  
Reverse Osmosis ◽  
Membrane Surface ◽  
Design Development ◽  
Permeate Flux ◽  
Membrane Channel ◽  
Initial Attempt ◽  
Membrane Surfaces ◽  
Ro Membrane

The objective of this study is to design spacers using fluid topology optimization in 2D crossflow Reverse Osmosis (RO) membrane channel to improve the performance of RO processes. This study is an initial attempt to apply topology optimization to designing spacers in RO membrane channel. The performance was evaluated by the quantity of permeate flux penetrating both upper and lower membrane surfaces. A coupled Navier-Stokes and Convection-Diffusion model was employed to calculate the permeate flux. To get reliable solutions, stabilization methods were employed with standard finite element method. The nine reference models which consist of the combination of circle, rectangular, triangle shape and zigzag, cavity, submerge configuration of spacers were simulated. Such models were compared with new model designed by topology optimization. The permeate flux at both membrane surfaces was determined as an objective function. In addition, permissible pressure drop along the channel and spacer volume were used as constraints. As a result of topology optimization as the permissible pressure drop changes in channel, characteristics of spacer design development was founded. Spacer design based on topology optimization was reconstructed to a simple one considering manufactuability and characteristics of development spacer design. When a simplified design was compared with previous 9 models, new design has a better performance in terms of permeate flux and wall concentration at membrane surface.

A Wall Film Model for Membrane Fouling

2018 ◽  
Author(s):  
Sina Jahangiri Mamouri ◽  
Volodymyr V. Tarabara ◽  
André Bénard
Keyword(s):  
Multiphase Flow ◽  
Membrane Fouling ◽  
Oil And Gas ◽  
Membrane Separation ◽  
Film Formation ◽  
Membrane Surface ◽  
Permeate Flux ◽  
Water Separation ◽  
Wall Film ◽  
Oil Water

Deoiling of produced or impaired waters associated with oil and gas production represents a significant challenge for many companies. Centrifugation, air flotation, and hydrocyclone separation are the current methods of oil removal from produced water [1], however the efficiency of these methods decreases dramatically for droplets smaller than approximately 15–20 μm. More effective separation of oil-water mixtures into water and oil phases has the potential to both decrease the environmental footprint of the oil and gas industry and improve human well-being in regions such as the Gulf of Mexico. New membrane separation processes and design of systems with advanced flow management offer tremendous potential for improving oil-water separation efficacy. However, fouling is a major challenge in membrane separation [2]. In this study, the behavior of oil droplets and their interaction with crossflow filtration (CFF) membranes (including membrane fouling) is studied using computational fluid dynamics (CFD) simulations. A model for film formation on a membrane surface is proposed for the first time to simulate film formation on membrane surfaces. The bulk multiphase flow is modeled using an Eulerian-Eulerian multiphase flow model. A wall film is developed from mass and momentum balances [3] and implemented to model droplet deposition and membrane surface blockage. The model is used to predict film formation and subsequent membrane fouling, and allow to estimate the actual permeate flux. The results are validated using available experimental data.

scholarly journals Effect of pH on membrane fouling during alcohol dehydrogenase immobilization in PES membrane

2020 ◽  
Vol 3 (2) ◽  
pp. 30
Author(s):  
Nurshahira Hazwani Hamran ◽  
Fauziah Marpani ◽  
Nur Hidayati Othman ◽  
Nik Raikhan Nik Him ◽  
Nur Hashimah Alias ◽  
...  
Keyword(s):  
Alcohol Dehydrogenase ◽  
Enzyme Immobilization ◽  
Membrane Fouling ◽  
Feed Solution ◽  
Permeate Flux ◽  
Enzyme Loading ◽  
Solution Ph ◽  
Observed Rejection ◽  
Pes Membrane ◽  
Blocking Mechanism

Fouling-induced enzyme immobilization is a technique to immobilize enzyme by positively manipulating the knowledge of membrane fouling. In this study, Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was immobilized in the support layer of ultrafiltration PES membrane at different solution pH (acid, neutral and alkaline). ADH catalyses formaldehyde (CHOH) to methanol (CH3OH) and simultaneously oxidised nicotinamide adenine dinucleotide (NADH) to NAD+. The initial feed amount of enzyme is 3.0 mg. The objective of the study aims at the effect of different pH of feed solution during enzyme immobilization, in terms of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that, pH 5 holds the highest enzyme loading which is 65% while pH 7 holds the lowest at 52% out of 3.0 mg as the initial enzyme feed. The permeate flux for each pH decreased with increasing cumulative permeate volume. The observed rejection is inversely correlated with the pH where increase in pH will cause a lower observed rejection. The fouling model predicted that irreversible fouling occurs during enzyme immobilization at pH 7 with standard blocking mechanism while reversible fouling occurs at pH 5 and 9 with intermediate and complete blocking, respectively.

Surface modification of reverse osmosis membranes with zwitterionic polymer to reduce biofouling

2015 ◽  
Vol 15 (5) ◽  
pp. 999-1010 ◽  
Author(s):  
Ahmed E. Abdelhamid ◽  
Mahmoud M. Elawady ◽  
Mahmoud Ahmed Abd El-Ghaffar ◽  
Abdelgawad M. Rabie ◽  
Poul Larsen ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Tap Water ◽  
Membrane Surface ◽  
Salt Content ◽  
Cross Flow ◽  
Membrane Properties ◽  
Cleaning Efficiency ◽  
Bacteria Growth ◽  
Cross Flow Filtration

The zwitterionic homopolymer poly[2-(methacryloyloxy)ethyl-dimethyl-(3-sulfopropyl) ammonium hydroxide was coated onto the surface of commercial polyamide reverse osmosis (RO) membranes. Aqueous solutions of the polymer at different concentrations were applied to modify the polyamide membranes through an in situ surface coating procedure. After membrane modification, cross-flow filtration testing was used to test the antifouling potential of the modified membranes. The obtained data were compared with experimental data for unmodified membranes. Each test was done by cross-flow filtering tap water for 60 hours. Yeast extract was added as a nutrient source for the naturally occurring bacteria in tap water, to accelerate bacteria growth. Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, atomic force microscopy, and permeation tests were employed to characterize membrane properties. The results confirmed that modifying the membranes enhanced their antifouling properties and cleaning efficiency, the fouling resistance to bacteria improving due to the increased hydrophilicity of the membrane surface after coating. In addition, the water permeability and salt rejection improved. This in situ surface treatment approach for RO membranes could be very important for modifying membranes in their original module assemblies as it increases water production and reduces the salt content.

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