The use of nanofiltration for the removal of pesticides from groundwater: an evaluation

2001 ◽  
Vol 1 (2) ◽  
pp. 99-106 ◽  
Author(s):  
B. Van der Bruggen ◽  
K. Everaert ◽  
D. Wilms ◽  
C. Vandecasteele
Keyword(s):  
Dipole Moment ◽  
Membrane Fouling ◽  
Solid Phase ◽  
Membrane Surface ◽  
Water Flux ◽  
Molecular Size ◽  
Effective Diameter ◽  
Molecular Configuration ◽  
Groundwater Flux ◽  
Flux Decline

This study explores the combined removal of four pesticides (atrazine, simazine, diuron, isoproturon) and hardness from groundwater with nanofiltration (NF). Four NF membranes were used: NF45 and NF70 (Dow/FilmTec), and UTC-20 and UTC-60 (Toray Ind. Inc.). Each pesticide was added to groundwater samples in a concentration of 1 μg/l, representative for contaminated sources. For the determination of pesticides in such low concentrations, an analytical method using solid-phase extraction and high performance liquid chromatography was elaborated. The retentions with NF were compared and explained by means of molecular size and dipole moment. Molecular size, expressed as an effective diameter representing the projection of the molecule on the membrane surface, was calculated by determining the energetically most favourable molecular configuration. The largest molecules had the highest retentions, when all other properties are comparable. A high dipole moment decreases retentions because of charge interactions with the membrane. The hardness retentions were high. For drinking water production, it might be necessary to add hardness after filtration. The groundwater flux was approximately 5% lower compared to the distilled water flux. This relatively small flux decline indicates pore blocking due to adsorption in the membrane pores. The flux decline was proved reversible; no membrane fouling occurred.

scholarly journals ZnO Microfiltration Membranes for Desalination by a Vacuum Flow-Through Evaporation Method

Membranes ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 156 ◽  
Author(s):  
Shailesh Dangwal ◽  
Ruochen Liu ◽  
Lyndon D. Bastatas ◽  
Elena Echeverria ◽  
Chengqian Huang ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Water Flux ◽  
Atomic Layer ◽  
Rejection Rate ◽  
Contact Angles ◽  
Transfer Resistance ◽  
Membrane Pore ◽  
Evaporation Method ◽  
Flow Through

ZnO was deposited on macroporous α-alumina membranes via atomic layer deposition (ALD) to improve water flux by increasing their hydrophilicity and reducing mass transfer resistance through membrane pore channels. The deposition of ZnO was systemically performed for 4–128 cycles of ALD at 170 °C. Analysis of membrane surface by contact angles (CA) measurements revealed that the hydrophilicity of the ZnO ALD membrane was enhanced with increasing the number of ALD cycles. It was observed that a vacuum-assisted ‘flow-through’ evaporation method had significantly higher efficacy in comparison to conventional desalination methods. By using the vacuum-assisted ‘flow-through’ technique, the water flux of the ZnO ALD membrane (~170 L m−2 h−1) was obtained, which is higher than uncoated pristine membranes (92 L m−2 h−1). It was also found that ZnO ALD membranes substantially improved water flux while keeping excellent salt rejection rate (>99.9%). Ultrasonic membrane cleaning had considerable effect on reducing the membrane fouling.

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.

Investigation of membrane fouling by synthetic and natural particles

2004 ◽  
Vol 50 (12) ◽  
pp. 279-285 ◽  
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Research Articles ◽  
Clay Material ◽  
Dramatic Effect ◽  
Flux Decline ◽  
Scanning Electron

The biggest impediment for applying membrane processes is fouling that comes from mass flux (such as particle and organic matter) to the membrane surface and its pores. Numerous research articles have indicated that either particles or natural organic matter (NOM) has been the most detrimental foulant. Therefore, the role of particles in membrane fouling was investigated with two synthetic waters (having either particles alone or particles with simple organic matter) and a natural water. Membrane fouling was evaluated with flux decline behavior and direct images from scanning electron microscopy. The results showed that the combined fouling by kaolin and dextran (a simple organic compound selected as a surrogate for NOM) showed no difference from the fouling with only the organic matter. The similarity might stem from the fact that dextran (i.e., polysaccharide) has no ability to be adsorbed on the clay material, so that the polysaccharide behaves the same with respect to the membrane with or without clay material being present. In contrast to kaolin, the natural particles showed a dramatic effect on membrane fouling.

Investigation of membrane fouling in ultrafiltration using model organic compounds

2005 ◽  
Vol 51 (6-7) ◽  
pp. 101-106 ◽  
Author(s):  
J.H. Kweon ◽  
D.F. Lawler
Keyword(s):  
Organic Compounds ◽  
Membrane Fouling ◽  
Alginic Acid ◽  
Membrane Surface ◽  
Sem Images ◽  
Membrane Processes ◽  
Xps Spectra ◽  
Relative Composition ◽  
Flux Decline ◽  
The City

Natural organic matter (NOM) is known to be the worst foulant in the membrane processes, but the complexities of NOM make it difficult to determine its effects on membrane fouling. Therefore, simple organic compounds (surrogates for NOM) were used in this research to investigate the fouling mechanisms in ultrafiltration. Previous research on NOM components in membrane processes indicated that polysaccharides formed an important part of the fouling cake. Three polysaccharides (dextran, alginic acid, and polygalacturonic acid) and a smaller carbohydrate (tannic acid) were evaluated for their removal in softening (the treatment process in the City of Austin). Two polysaccharides (dextran and alginic acid) were selected and further investigated for their effects on membrane fouling. The two raw organic waters (4 mg/L C) showed quite different patterns of flux decline indicating different fouling mechanisms. Softening pretreatment was effective to reduce flux decline of both waters. The SEM images of the fouled membrane clearly showed the shapes of deposited foulants. The high resolution results of the XPS spectra showed substantially different spectra of carbon, C(1s), in the membrane fouled by two raw organic waters. The XPS was beneficial in determining the relative composition of each fouling material on the membrane surface.

scholarly journals Effect of Initial Water Flux on the Performance of Anaerobic Membrane Bioreactor: Constant Flux Mode versus Varying Flux Mode

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 203
Author(s):  
Xiawen Yi ◽  
Meng Zhang ◽  
Weilong Song ◽  
Xinhua Wang
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Water Flux ◽  
Operating Time ◽  
Operating Mode ◽  
Initial Water ◽  
Constant Flux ◽  
Membrane Performance ◽  
Fouling Mitigation ◽  
Flux Mode

Anaerobic membrane bioreactors (AnMBRs) have aroused growing interest in wastewater treatment and energy recovery. However, serious membrane fouling remains a critical hindrance to AnMBRs. Here, a novel membrane fouling mitigation via optimizing initial water flux is proposed, and its feasibility was evaluated by comparing the membrane performance in AnMBRs between constant flux and varying flux modes. Results indicated that, compared with the constant flux mode, varying flux mode significantly prolonged the membrane operating time by mitigating membrane fouling. Through the analyses of fouled membranes under two operating modes, the mechanism of membrane fouling mitigation was revealed as follows: A low water flux was applied in stage 1 which slowed down the interaction between foulants and membrane surface, especially reduced the deposition of proteins on the membrane surface and formed a thin and loose fouling layer. Correspondingly, the interaction between foulants was weakened in the following stage 2 with a high water flux and, subsequently, the foulants absorbed on the membrane surface was further reduced. In addition, flux operating mode had no impact on the contaminant removal in an AnMBR. This study provides a new way of improving membrane performance in AnMBRs via a varying flux operating mode.

scholarly journals Effect of the Zwitterion, p(MAO-DMPA), on the Internal Structure, Fouling Characteristics, and Dye Rejection Mechanism of PVDF Membranes

Membranes ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 323
Author(s):  
Nelisa Ncumisa Gaxela ◽  
Philiswa Nosizo Nomngongo ◽  
Richard Motlhaletsi Moutloali
Keyword(s):  
Internal Structure ◽  
Membrane Fouling ◽  
Vinylidene Fluoride ◽  
Membrane Surface ◽  
Pure Water ◽  
Water Flux ◽  
Proton Nuclear Magnetic Resonance ◽  
Pvdf Membrane ◽  
Membrane Performance ◽  
Dye Rejection

The zwitterion poly-(maleic anhydride-alt-1-octadecene-3-(dimethylamino)-1-propylamine) (p(MAO-DMPA)) synthesized using a ring-opening reaction was used as a poly(vinylidene fluoride) (PVDF) membrane modifier/additive during phase inversion process. The zwitterion was characterized using proton nuclear magnetic resonance (1HNMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Atomic force microscopy (AFM), field emission scanning electron microscope (SEM), FTIR, and contact angle measurements were taken for the membranes. The effect of the zwitterionization content on membrane performance indicators such as pure water flux, membrane fouling, and dye rejection was investigated. The morphology of the membranes showed that the increase in the zwitterion amount led to a general decrease in pore size with a concomitant increase in the number of membrane surface pores. The surface roughness was not particularly affected by the amount of the additive; however, the internal structure was greatly influenced, leading to varying rejection mechanisms for the larger dye molecule. On the other hand, the wettability of the membranes initially decreased with increasing content to a certain point and then increased as the membrane homogeneity changed at higher zwitterion percentages. Flux and fouling properties were enhanced through the addition of zwitterion compared to the pristine PVDF membrane. The high (>90%) rejection of anionic dye, Congo red, indicated that these membranes behaved as ultrafiltration (UF). In comparison, the cationic dye, rhodamine 6G, was only rejected to <70%, with rejection being predominantly electrostatic-based. This work shows that zwitterion addition imparted good membrane performance to PVDF membranes up to an optimum content whereby membrane homogeneity was compromised, leading to poor performance at its higher loading.

Experimental test to evaluate performance of an anaerobic reactor provided with an external membrane unit

1998 ◽  
Vol 38 (8-9) ◽  
pp. 385-392 ◽  
Author(s):  
S. Elmaleh ◽  
L. Abdelmoumni
Keyword(s):  
Membrane Fouling ◽  
Industrial Development ◽  
Particle Deposition ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Unit ◽  
Anaerobic Reactor ◽  
Flux Decline ◽  
Aerobic Reactor ◽  
Sludge Production

The coupling of a wastewater treatment anaerobic reactor with a microfiltration or ultrafiltration membrane is particularly attractive: lower sludge production than in an aerobic reactor, methane production and dissociation of the mean residence times of the different phases. However, the industrial development of such a process is hampered by membrane fouling which can be a result of many causes and require a comprehensive study especially fouling by anaerobic suspensions. In order to simplify the study, the different phases of anaerobic oxidation were separated and this work is focused on the filtration of an anaerobic suspension fed with acetic acid as the sole carbon source at 2 g/l TOC. The effluent quality was excellent without sludge production in spite of large variation of the liquid phase space time. The tested filtration elements were tubular Carbosep membranes. The M14 membrane showed the greatest flux of 120 l/m2 h at 0.5 bar and 25 Pa shear stress and the flux increased to 180 l/m2 h when a baffle was introduced. The main fouling mechanism appears to be the particle deposition on the membrane surface as no flux decline was observed at higher cross-flow velocity.

scholarly journals Studies of polypropylene membrane fouling during microfiltration of broth with Citrobacter freundii bacteria

2015 ◽  
Vol 17 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Marek Gryta ◽  
Marta Waszak ◽  
Maria Tomaszewska
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Transmembrane Pressure ◽  
Citrobacter Freundii ◽  
Permeate Flux ◽  
Process Duration ◽  
Polypropylene Membrane ◽  
Flux Decline ◽  
Cake Layer ◽  
Scanning Electron

Abstract In this work a fouling study of polypropylene membranes used for microfiltration of glycerol solutions fermented by Citrobacter freundii bacteria was presented. The permeate free of C. freundii bacteria and having a turbidity in the range of 0.72–1.46 NTU was obtained. However, the initial permeate flux (100–110 L/m2h at 30 kPa of transmembrane pressure) was decreased 3–5 fold during 2–3 h of process duration. The performed scanning electron microscope observations confirmed that the filtered bacteria and suspensions present in the broth formed a cake layer on the membrane surface. A method of periodical module rinsing was used for restriction of the fouling influence on a flux decline. Rinsing with water removed most of the bacteria from the membrane surface, but did not permit to restore the initial permeate flux. It was confirmed that the irreversible fouling was dominated during broth filtration. The formed deposit was removed using a 1 wt% solution of sodium hydroxide as a rinsing solution.

scholarly journals Membrane Fouling and Performance of Flat Ceramic Membranes in the Application of Drinking Water Purification

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2606 ◽  
Author(s):  
Shujuan Meng ◽  
Minmin Zhang ◽  
Meng Yao ◽  
Zhuguo Qiu ◽  
Yubin Hong ◽  
...  
Keyword(s):  
Drinking Water ◽  
Surface Water ◽  
Water Purification ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Water Flux ◽  
Ceramic Membranes ◽  
Surface Water Treatment ◽  
Drinking Water Purification

Membrane technologies have been widely applied in surface water treatment for drinking water purification. The main obstacles to the large scale application of membranes include membrane fouling, energy consumption and high investment. This study systematically investigated the performance of a hybrid system including in-situ coagulation and membrane module. The key parameters of a membrane system, including initial flux, operation mode (intermediate or continuous, time intervals, backwashing and aeration) was comprehensively investigated. In addition, the treatment performance in terms of turbidity, organic matter removal, membrane fouling and cleaning, and the effect of coagulants, were also studied. It was found that flat ceramic membranes with in-situ coagulation for surface water treatment performed much better without aeration and frequent backwashing, which gave interesting and important implications for future applications of a flat ceramic membrane, especially in drinking water purification. The hybrid system can achieve a high-water flux of 150 L/m2·h (LMH) for 8 h operation without aeration and backwash. The removal of turbidity, UV254 and COD can achieve 99%, 85% and 81%, respectively. The cake layer on the membrane surface formed from the coagulation flocs turned out to prevent the membrane to be exposed to organic pollutant immediately which minimized the fouling problem. In addition, the fouling layer on the membrane surface can be easily cleaned by air scouring and backwash at the end of experiments, with a water flux recovery of higher than 90%. These results in this study provided an alternative strategy for membrane fouling control and energy conservation.

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