scholarly journals Removal and transport mechanisms of arsenics in UF and NF membrane processes

2006 ◽  
Vol 4 (2) ◽  
pp. 215-223 ◽  
Author(s):  
Do Hee Kim ◽  
Kyoung Woong Kim ◽  
Jaeweon Cho
Keyword(s):  
Membrane Surface ◽  
Cross Flow ◽  
Operating Conditions ◽  
Reflection Coefficients ◽  
Transport Mechanisms ◽  
Flat Sheet ◽  
Charged Membrane ◽  
Cross Flow Velocity ◽  
Diffusion And Convection ◽  
Uf Membranes

In this study, the removal and transport mechanisms of ionized and non-ionized arsenics through NF and UF membranes were systemically investigated. The charge repulsion between the membrane surface and arsenic ions was an important mechanism for the rejection of ions by a charged membrane. In addition, the effect of J0/k ratio was dependent on the membrane and ion charge, but the cross-flow velocity was not significantly affected. Both diffusion and convection are proved to affect the transport of arsenic ions. The reflection coefficients (σ) of both UF and NF membranes increased with increasing pH; the reflection coefficients of arsenate were higher than those of arsenite under the same operating conditions. The spiral-wound module exhibited slightly higher arsenate removal than the flat-sheet module under the same operating conditions.

scholarly journals Behaviour of Aquaporin Forward Osmosis Flat Sheet Membranes during the Concentration of Calcium-Containing Liquids

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 108
Author(s):  
Alibek Omir ◽  
Aliya Satayeva ◽  
Aigerim Chinakulova ◽  
Arailym Kamal ◽  
Jong Kim ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Saturation Index ◽  
Membrane Surface ◽  
Water Flux ◽  
Forward Osmosis ◽  
Cross Flow ◽  
Calcium Sulphate ◽  
Attenuated Total Reflection ◽  
Flat Sheet ◽  
Cross Flow Velocity

This study aims to examine the scaling and performance of flat sheet aquaporin FO membranes in the presence of calcium salts. Experiments showed that the application of calcium sulphate (CaSO4) resulted in an 8–78% decline in the water flux. An increase in the cross-flow velocity from 3 to 12 cm/s reduced the decline in the flux by 16%. The deposition of salt crystals on the membrane surface led to the alteration in the membrane’s intrinsic properties. Microscopy, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-Ray fluorescence (XRF) analyses confirmed measurements of the zeta potential and contact angle. The use of a three-salt mixture yielded severe scaling as compared with the application of calcium sulphate dehydrate (CaSO4 × 2H2O), i.e., a result of two different crystallisation mechanisms. We found that the amount of sodium chloride (NaCl), saturation index, cross-flow velocity, and flow regime all play an important role in the scaling of aquaporin FO flat sheet membranes.

scholarly journals Air Backwash Efficiency on Organic Fouling of UF Membranes Applied to Shellfish Hatchery Effluents

Membranes ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 48 ◽  
Author(s):  
Clémence Cordier ◽  
Christophe Stavrakakis ◽  
Patrick Sauvade ◽  
Franz Coelho ◽  
Philippe Moulin
Keyword(s):  
Membrane Surface ◽  
Operating Conditions ◽  
Particle Removal ◽  
Two Phase ◽  
Significant Information ◽  
Dead End ◽  
Biodiversity Preservation ◽  
Organic Fouling ◽  
Uf Membranes ◽  
The Impact

Among all the techniques studied to overcome fouling generated in dead-end filtration, the injection of air during backwashes proved to be the most effective. Indeed, shear stress engendered by the two-phase flow enhanced particle removal on membrane surface. This work aims to study the injection of air to drain the membranes before backwash. Firstly, the efficiency of this backwash procedure was evaluated during the ultrafiltration of seawater on a semi industrial pilot plant using different operating conditions. Then, the treatment of seawater, doped with oyster gametes to simulate the filtration of shellfish hatchery effluents, was performed to confirm the hydraulic performance of the air backwash. Indeed, the release of gametes, expulsed by exotic bivalves in the natural environment, could be a risk for the biodiversity preservation. The impact of air backwash on the integrity of oocytes and spermatozoa was identified using flow cytometry and microscopic analyses. When oyster gametes were added, their retention by ultrafiltration was validated. The impact of air backwash on these species viability was a significant information point for the implementation of this process on shellfish production farms.

scholarly journals DETERMINATION OF FOULING MECHANISM IN ULTRAFILTRATION OF ELECTROPLATING WASTEWATER

2018 ◽  
Vol 80 (3-2) ◽  
Author(s):  
Danu Ariono ◽  
Anita Kusuma Wardani ◽  
Putu Teta Prihartini Aryanti ◽  
Ahmad Nurul Hakim ◽  
I Gede Wenten
Keyword(s):  
Flow Velocity ◽  
Membrane Fouling ◽  
Membrane Surface ◽  
Cross Flow ◽  
Permeate Flux ◽  
High Concentration ◽  
Filtration Time ◽  
Electroplating Wastewater ◽  
Fouling Mechanism ◽  
Cross Flow Velocity

Wastewater from electroplating industries is usually contaminated with high concentration of hazardous materials, such as nickel, copper, and chromium. Therefore, the electroplating wastewater is one of the environmental problems that require a novel solution to reduce risks for human and environment. Ultrafiltration is a promising technology to overcome this problem due to its ability to reject all suspended solids. However, membrane fouling still becomes a major obstacle in ultrafiltration processes. Fouling reduces the permeate flux and increases membrane operational costs due to membrane cleaning. In this work, fouling mechanism that occurred in polyacrylonitrile based ultrafiltration for electroplating wastewater treatment was investigated. The effects of trans-membrane pressure (TMP) and cross flow velocity on fouling mechanism were also studied. The results showed that in the first 20 minutes, intermediate blocking was occurred on the membrane surface, while cake formation was happened for the rest of filtration time. These results were applied for all TMP and cross flow velocity.

Removal of Humic Substances by UF and NF Membrane Systems

1999 ◽  
Vol 40 (9) ◽  
pp. 121-129 ◽  
Author(s):  
Rulin Bian ◽  
Yoshimasa Watanabe ◽  
Norihito Tambo ◽  
Genzo Ozawa
Keyword(s):  
Humic Substances ◽  
Removal Efficiency ◽  
Membrane Surface ◽  
Cross Flow ◽  
Molecular Size ◽  
Bulk Water ◽  
Flow Mode ◽  
Permeate Flux ◽  
Strong Shear ◽  
Uf Membranes

This paper deals with the removal efficiency and mechanisms of humic substances contained in a river water by ultrafiltration (UF) and nanofiltration (NF) membranes. UF membranes with molecular weight cut-off (MWCO) of 50 kDa to 200 kDa can remove only large molecular size humic substances (LMSHS). Even in the UF membranes operated under the cross-flow mode, the LMSHS were accumulated on the membrane surface, because the back transport velocity of LMSHS is always smaller than that of the permeate flux. Precoagulation enhanced the removal of humic substances effectively. The optimum coagulation conditions for removing the humic substances in the UF membranes was the same as that in the conventional coagulation/flocculation/sedimentation process. The vibration action increased the removal efficiency of humic substances in the NF membrane process. Strong shear produced by the vibration diffused away the humic substances from the membrane surface to the bulk water, therefore the accumulation of humic substances on/near the membrane surface, i.e. formation of cake and concentration polarization boundary layers, is prohibited.

scholarly journals Influence of twisted tape turbulence promoter on fouling reduction in microfiltration of milk proteins

2011 ◽  
Vol 65 (3) ◽  
pp. 233-239 ◽  
Author(s):  
Svetlana Popovic ◽  
Dragica Jovicevic ◽  
Mirjana Djuric ◽  
Spasenija Milanovic ◽  
Miodrag Tekic
Keyword(s):  
Aspect Ratio ◽  
Membrane Surface ◽  
Cross Flow ◽  
Milk Proteins ◽  
Operating Conditions ◽  
Twisted Tape ◽  
Membrane Processes ◽  
Twisted Tapes ◽  
Fouling Reduction ◽  
Pressure Driven

Membrane filtration has become one of the major technologies in the food industry. It is widely applied in the dairy industry, and it is mostly used for the concentration and fractionation of milk proteins and for the whey processing. Of all pressure driven membrane processes, ultrafiltration is the most widely used. The major disadvantage of pressure driven membrane processes is severe fouling of membrane during filtration particularly when the fluids containing proteins are processed. Fouling with proteins is complex phenomenon because it occurs at the membrane surface as well as in the pores of membrane, and depends on the operating conditions and on the interactions of proteins and membrane material. In order to reduce fouling of the membrane different techniques have been developed, and one of them relies on the changing of the hydrodynamic conditions in the membrane or module. In this study, influence of twisted tape turbulence promoters on the fouling reduction in cross-flow microfiltration of skim milk was investigated. Twisted tapes with tree characteristic ratios of helix element length to the tape diameter (aspect ratio) were studied. It was shown that twisted tapes with different aspect ratios reduce fouling of membrane by a factor of three or more. The presence of twisted tape induces changes in the flow patterns from straight to helicoidally thus producing turbulence flow at the lower cross-flow rates. Turbulence intensification prevents accumulation of proteins at membrane surface enabling reduction in reversible fouling what results in the reduction of overall membrane fouling. The best performance was achieved using a twisted tape with the lowest aspect ratio of 1.0. This promoter reduces fouling seven times at low transmembrane pressure and low cross-flow velocity. The twisted tape with aspect ratio 1.0 induces the most intensive turbulence, the longest helicoidal flow path, and appearance of vortices near the membrane surfaces, so the scouring of proteins from the membrane surface is the most intensive in that case.

scholarly journals The concentrating of alizarin using a reverse osmosis process

2005 ◽  
Vol 70 (1) ◽  
pp. 107-114 ◽  
Author(s):  
S.S. Madaeni ◽  
H. Daneshvar
Keyword(s):  
Flow Velocity ◽  
Reverse Osmosis ◽  
Cross Flow ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Transmembrane Pressure ◽  
Reverse Osmosis Membrane ◽  
Cross Flow Velocity ◽  
Membrane Technologies ◽  
Madder Root

Membrane technologies in general and reverse osmosis in particular have been employed for the concentrating of solutions. In this study, the concentrating of a heat sensitive alizarin extracted from madder root was realized using an FT30 reverse osmosis membrane. The effects of cross flow velocity, transmembrane pressure and pH on the flux and rejection were studied. Increasing the transmembrane pressure increased the flux while the rejection was constant. At pH 7-8, the highest flux was achieved. This study showed that reverse osmosis is the process of choice for the concentrating of alizarin solutions. The optimum operating conditions were 1.0 m/s cross flow velocity, 16 bars transmembrane pressure and pH 7. The system was tested for 12 h without severe fouling problems.

scholarly journals Experimental investigation of the cooling characteristics of a monobloc cast iron brake disc with fingered hub

2019 ◽  
Vol 234 (1) ◽  
pp. 85-97
Author(s):  
Marko Tirovic ◽  
Stergios Topouris ◽  
Glenn Sherwood
Keyword(s):  
Heat Dissipation ◽  
Cross Flow ◽  
Operating Conditions ◽  
Brake Disc ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Single Piece ◽  
Brake Discs ◽  
Cross Flow Velocity

The paper compares heat dissipation characteristics of two interchangeable ventilated brake discs, a standard solid hub and a newly developed fingered hub version, both single piece cast designs. The tests were conducted on a specially developed Thermal Flow Rig, which enables disc induction heating to 450°C and cooling for a range of rotational and air speeds, in parallel and angular cross flow. The Rig facilitated very accurate and repeatable experiments to be conducted for numerous combinations of operating conditions. From the recorded cooling curves, average heat transfer coefficients for convection and radiation were extracted and the results also presented in a generic form, using Nusselt numbers. The fingered design demonstrated superior convective heat dissipation, with the improvements varying depending on the rotational speed, air cross flow velocity and angle, as well as disc temperature. The gains were ranging from 3.5% to over 20%. The fingered design is 8.5% lighter and being a single piece cast disc, it remains inexpensive to mass produce.

Performances and fouling control of a flat sheet membrane in a MBR pilot-plant

2010 ◽  
Vol 61 (9) ◽  
pp. 2185-2192 ◽  
Author(s):  
A. Grélot ◽  
P. Grelier ◽  
A. Tazi-Pain ◽  
B. Lesjean ◽  
U. Brüss ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Membrane Surface ◽  
Membrane Technology ◽  
Operating Conditions ◽  
Mixed Liquor ◽  
Fouling Control ◽  
Biological Stress ◽  
Flat Sheet ◽  
Flat Sheet Membrane ◽  
Sheet Membrane

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) = 10 g/l; sludge retention time (SRT) = 28 days; food to microorganism ratio (F/M)= 0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h−1 m−2, 20°C at a low specific aeration demand per membrane surface (SADm = 0.2 Nm3 h−1 m−2) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8 Nm3 air/m3 permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.

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