Spacer-filled Channels Research Articles

Automated image processing algorithm for 3D OCT images of fouling in spacer-filled membrane filtration channels

OCT imaging is an important technique to study fouling in spacer-filled channels of reverse osmosis systems for seawater desalination. However, OCT imaging of membrane filtration channels with feed spacers is challenging because the spacer material can be (partly) transparent, making it difficult to detect and possibly mistaken for fouling, and the longer optical pathway through the spacer material distorts the image below the spacer. This study presents an automated 3D OCT image processing method in MATLAB for visualization and quantification of biofouling in spacer-filled channels. First, a spacer template of arbitrary size and rotation was generated from a CT scan of the feed spacer. Second, background noise and file size were reduced by representing the OCT image with a list of discrete reflectors. Finally, the spacer template was overlayed with the feed spacer in the 3D OCT image, enabling automated visualization of the feed spacer and correction of the distortions. Moreover, the method allows the selection of datasets with the same location relative to the position of the spacer, enabling systematic comparison between datasets and quantitative analysis.•A spacer template of arbitrary size and rotation was generated from a CT scan.•The background noise was removed, and the file size was reduced by representing the OCT dataset with a list of discrete reflectors.•The spacer template was overlayed with the feed spacer in the 3D OCT image.

Performance evaluation of regeneration of high-concentration liquid desiccant using direct contact membrane distillation

Membrane-based absorptive dehumidification is an attractive technique for humidity control that reduces energy consumption. The process involves a dehumidifier that absorbs moisture with a liquid desiccant, and a regenerator that concentrates the desiccant solution to complete the process cycle. In this study, a regeneration module employing a membrane distillation (MD) mechanism was developed, and its performance was evaluated theoretically and experimentally. Detailed theoretical investigations demonstrated the impact of the spacer on the convective thermal and material transport at the membrane surface at a high desiccant concentration. The module employs a hydrophobic and microporous composite membrane consisting of a polypropylene support layer and an active layer composed of polytetrafluoroethylene. For all the experiments, the desiccant solution used was an aqueous solution containing 25 wt% of lithium chloride. The transmembrane flux of the regeneration module was evaluated at different feed and permeate flow rates from 0.6 to 1.4 L/min at solution temperatures of 45 to 80 ℃ and a permeate temperature of 25 ℃. The permeate flux of the regeneration module with the spacer-filled channel increased by more than 50 % compared with that of the empty channel. The regeneration module using spacers achieved a permeate flux ranging from 1.9 to 4.3 kg/m2h during desiccant regeneration at a solution temperature of 50 ℃.

Review and Analysis of Heat Transfer in Spacer-Filled Channels of Membrane Distillation Systems.

Membrane distillation (MD) is an attractive process for the concentration of seawater brines. Modelling and simulation of membrane distillation processes requires a better knowledge of the heat transfer coefficients in spacer-filled channels which are usually determined by applying empirical correlations for the Nusselt number. In this study, first, a comprehensive literature review on heat transfer correlations was conducted. It was found that the empirical correlations often used for MD simulation result in strongly varying Nusselt numbers that differ by up to an order of magnitude at low Reynolds numbers. Then, heat transfer in spacer-filled channels was investigated experimentally in a membrane distillation system using an aluminum plate instead of a flat-sheet membrane. Numerous tests were carried out with sodium chloride solutions in a wide range of salinities, between 1 g/kg and 95 g/kg, and temperatures, between 30 °C and 80 °C, yielding high heat transfer coefficients in a range of 1500 to 8300 W/(m2K) at relatively low Reynolds numbers, between 100 and 1500, clearly showing the influence of the spacers on heat transfer. A new empirical Nusselt correlation (Nu=0.158Re0.652Pr0.277) was derived which represents the experimental data with a deviation of 10% and is valid for 100<Re<1500 and 2<Pr<7. Computational fluid dynamics simulations were performed to analyze the variations of the fluid properties across the boundary layer due to temperature differences. The simulations showed only minor deviations of the heat transfer coefficients in the hot and cold fluid channels for small driving temperature differences.

Performance characteristics on up-scaling vacuum membrane distillation modules

Large-scale CFD studies are currently lacking in membrane distillation due to high computational overhead. This study utilizes a validated CFD model for vacuum membrane distillation and reduces the order of the model to enable prototype scale simulations. Different module designs were considered: a baseline flat sheet membrane module, a spacer-filled channel, a wavy channel, and a wavy channel with embedded stiffeners. Different lengths (330 mm, 660 mm, and 990 mm) were studied to simulate lab to prototype upscaling. Large Eddy Simulations were run in the laminar (Re 900) and turbulent (Re 3600) flow regimes. For Re 900, cases with geometric alterations (wavy membrane, spacer-filled channel) locally outperformed the baseline case within the first 330 mm before axial temperature polarization equilibrated the performance between the baseline and altered channels. The improvement in local performance was seen over the whole 990 mm length at Re 3600, culminating in a 35–40 % flux improvement versus the baseline at Re 3600 versus a 0–35 % difference at Re 900. Axial temperature polarization was mitigated using heat injection, showing a 5 % flux drop as length tripled compared to a 20–27 % decline. Higher operational Reynolds numbers should be considered cautiously for increasing pressure drop and violating the liquid entry pressure limit for wetting.

Analyzing the pressure drop in spacer stacks for electrodialytic processes considering the effect of mechanical compression: Experimental vs. free and porous flow model prediction

There is a growing interest in using electromembrane processes in sustainable applications. However, it involves designing efficient cells with low pressure drops, which is particularly important in processes requiring high energy efficiency. In order to analyze the fluid dynamics in spacer-filled channels, manifolds and stacks used primarily in acid base flow batteries a free and porous flow model was developed. The predictive model composed by Navier-Stokes equations and Brinkman Forchheimer extended Darcy model closely follows the experimental pressure drop in a single spacer-filled channel. According to the model results, the entrance and exit zones of the spacer produce the highest pressure drop per axial longitude, highlighting the strong effect of the design of spacer in these zones. In the case of stacks the mechanical compression among spacers as revealed by measurement with compression film suggests some spacer deformation on entrance and exit zones that intensified the inlet and outlet effects.

Evaluation of spacer-induced hydrodynamic mixing using particle image velocimetry: Impact on membrane distillation performance

Net-type spacers are used to promote hydrodynamic mixing in the feed channel of crossflow membrane filtration. The induced fluid flow mitigates concentration and temperature polarization effects on the membrane surface, leading to the enhancement of heat/mass transfer across the membrane. The objective of this research is to study the effect of spacer geometry on fluid flow and heat/mass transfer in the feed channel. The particle image velocimetry (PIV) technique was used to measure flow velocity in the feed channel with net-type spacers. Flow characteristics at a wide range of Reynolds numbers were described in terms of time-averaged mean velocity and turbulence kinetic energy (TKE). The PIV result revealed distinct profiles of mean velocity and TKE at different channel heights with bi-planar spacers. The spacer with the largest hydrodynamic angle of 120° (Net120) was found to be the most efficient in promoting flow unsteadiness because it led to the largest channel-averaged TKE among the selected spacers. The unsteady flow regime on Net120 was accompanied by the greatest pressure drop over the feed channel. Moreover, the effect of spacer-induced mixing on heat/mass transfer across the membrane was further evaluated via the flux measurement with vacuum membrane distillation experiments. In comparison with other spacers, Net120 resulted in a relatively higher flux because of the improved hydrodynamic mixing. These findings reveal the validity of the experimental approach in identifying the impact of key spacer design parameters on hydrodynamic mixing. Nusselt number was calculated to relate the hydrodynamic flow and thermal flow in the feed channel of membrane distillation, and a modified Nusselt number correlation was proposed to better predict convective heat transfer in the spacer-filled channel in VMD.

Electrodialysis desalination: The impact of solution flowrate (or Reynolds number) on fluid dynamics throughout membrane spacers

The incorporation of a spacer among membranes has a major influence on fluid dynamics and performance metrics. Spacers create feed channels and operate as turbulence promoters to increase mixing and reduce concentration/temperature polarization effects. However, spacer geometry remains unoptimized, and studies continue to investigate a wide range of commercial and custom-made spacer designs. The in-depth discussion of the present systematic review seeks to discover the influence of Reynolds number or solution flowrate on flow hydrodynamics throughout a spacer-filled channel. A fast-flowing solution sweeping one membrane's surface first, then the neighboring membrane's surface produces good mixing action, which does not happen commonly at laminar solution flowrates. A sufficient flowrate can suppress the polarization layer, which may normally require the utilization of a simple feed channel rather than complex spacer configurations. When a recirculation eddy occurs, it disrupts the continuous flow and effectively curves the linear fluid courses. The higher the flowrate, the better the membrane performance, the higher the critical flux (or recovery rate), and the lower the inherent limitations of spacer design, spacer shadow effect, poor channel hydrodynamics, and high concentration polarization. In fact, critical flow achieves an acceptable balance between improving flow dynamics and reducing the related trade-offs, such as pressure losses and the occurrence of concentration polarization throughout the cell. If the necessary technical flowrate is not used, the real concentration potential for transport is relatively limited at low velocities than would be predicted based on bulk concentrations. Electrodialysis stack therefore may suffer from the dissociation of water molecules. Next studies should consider that applying a higher flowrate results in greater process efficiency, increased mass transfer potential at the membrane interface, and reduced stack thermal and electrical resistance, where pressure drop should always be indicated as a consequence of the spacer and circumstances used, rather than a problem.

Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers.

The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height H ≈ 1 cm, ΔT ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels.

Investigations on the effect of spacer in direct contact and air gap membrane distillation using computational fluid dynamics

Direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) have emerged as potential technologies for water and wastewater treatment. This investigation developed a comprehensive two-dimensional computational fluid dynamics model to describe and simulate heat transfer, mass transfer, and fluid flow in DCMD and AGMD processes. The effect of Reynolds number, inlet feed temperature, and distance between two successive spacer filaments on the performance parameters such as mass flux, temperature polarisation, concentration polarisation, and thermal efficiency was investigated in this work. The feed and permeate side heat transfer coefficient increased with Re in the DCMD and AGMD models. The thickness of the velocity boundary layers reduced upon introducing spacers in the feed and permeate channels. The mass flux on the introduction of spacers increased in DCMD and AGMD models because the boundary layer resistance was reduced. The models with spacer showed a lower oncentration polarisation. DCMD model demonstrated a loweroncentration polarisation than the AGMD model as the former has higher mass flux than the latter leading to a higher solute concentration on the membrane surface. The thermal boundary layer was smaller in the spacer-filled channel because of the fluid mixing. In the AGMD model, the permeate side thermal boundary layer was unaffected because of the poor conductivity of air than water.

Experimental investigation of two-side heat transfer in spacer-filled channels representative of membrane distillation

Heat transfer in spacer-filled plane channels was investigated by using thermochromic liquid crystals and digital image processing. A novel test section allowed the establishment of two-side cooling, closely representative of the conditions existing in real plane or spiral-wound membrane distillation (MD) modules. Several spacer configurations were investigated, differing in design (overlapped or woven filaments), pitch-to-height ratio and orientation with respect to the main flow direction. The Reynolds number Re ranged from 160 to 2500, as is typical in MD. At all flow rates investigated, symmetric two-side cooling provided significantly higher (25–35%) local and mean heat transfer coefficients hh than one-side cooling. The mean heat transfer coefficient increased when the pitch-to-height ratio increased from 2 to 4, and was much higher for woven than for overlapped spacers. Overlapped spacers with a flow attack angle ϕ of 0°-90° with respect to the two layers of spacer filaments exhibited significantly different distributions and mean values of hh on the two sides, the larger values occurring where the flow was orthogonal to the filaments. In all cases, the dependence of hh on Re could not be described by a simple power law.

Solution of an inverse heat conduction problem with third-type boundary conditions

An algorithm is presented for the solution of an inverse heat conduction problem: reconstruct the steady-state distribution of the convection heat transfer coefficient on one wall of a slab from the temperature distribution on a plane embedded in the slab, assuming that the thermal boundary conditions on the other walls are known. The algorithm is based on the finite volume discretization of the slab and on the construction and subsequent inversion of square matrices linking the distributions of wall temperature and wall heat flux to that of temperature at the internal plane. The algorithm is first applied to a simulated temperature distribution, for which it is assessed for accuracy and compared with a simpler method based on the assumption of one-dimensional heat conduction. It is then applied to real experimental temperature distributions obtained by digitally processing thermochromic liquid crystals images in spacer-filled channels simulating membrane distillation modules. Tolerance to noise is demonstrated in both cases provided an adequate amount of filtering is applied to the primitive, high-resolution temperature distribution.

Pressure drop across membrane spacer-filled channels using porous media characteristics and computational fluid dynamics simulation

Pressure drop across membrane spacer-filled channels using porous media characteristics and computational fluid dynamics simulation

Modelling of flow distribution within spacer-filled channels fed by dividing manifolds as found in stacks for membrane-based technologies

Manifolds are critical to the performance of different membrane-based technologies. These stack components distribute the inlet and outlet flow with the aim of providing a homogenous flow pattern inside the spacer-filled channels. This work analyzes the role of manifolds on the flow pattern within the channels of membrane stacks used primarily for electrodialysis and acid-base flow batteries. First, residence time distribution (RTD) curves are predicted for a spacer-filled channel by means of three strategies: (a) computational fluid dynamics (CFD) simulation using a periodic unit cell model, (b) parametric models: axial dispersion model (ADM) and the plug dispersion exchange (PED) model using Danckwerts-type boundary conditions, and (c) the ADM and PED model using the segregate flow laminar model (SFLM) as flow pattern at the left-hand side (z=0-) in the Danckwerts-type inlet boundary condition. In contrast to previous studies, it is shown that the dividing manifold generates experimental RTD curves with several peaks characteristic of uneven distribution and long-tailing phenomena with small fluctuations related to the woven spacer and the combining manifold, respectively. The periodic unit cell CFD model, the ADM and PED model with convectional Danckwerts-type boundary conditions do not predict the RTD experimental curves because they do not consider the effect of RTD curves for the manifolds. On the other hand, the SFLM described these RTD curves adequately, as obtained by CFD simulations; this model used the left-hand side of Danckwerts inlet boundary condition for the PDE model, which had a good agreement to the global RTD experimental curves and their peaks. This study demonstrates that the global RTD curve of electrolytes in rectangular, spacer-filled channels must consider the effect of dividing and combining manifolds as inlet/outlet distributors. The strategy developed here can be used to design and scale-up membrane stacks for industrial and energy conversion applications.

Correlations for Concentration Polarization and Pressure Drop in Spacer-Filled RO Membrane Modules Based on CFD Simulations.

Empirical correlations for mass transfer coefficient and friction factor are often used in process models for reverse osmosis (RO) membrane systems. These usually involve four dimensionless groups, namely Reynolds number (Re), Sherwood number (Sh), friction factor (f), and Schmidt number (Sc), with the associated coefficients and exponents being obtained by fitting to experimental data. However, the range of geometric and operating conditions covered by the experiments is often limited. In this study, new dimensionless correlations for concentration polarization (CP) modulus and friction factor are presented, which are obtained by dimensional analysis and using simulation data from computational fluid dynamics (CFD). Two-dimensional CFD simulations are performed on three configurations of spacer-filled channels with 76 combinations of operating and geometric conditions for each configuration, covering a broad range of conditions encountered in RO membrane systems. Results obtained with the new correlations are compared with those from existing correlations in the literature. There is good consistency in the predicted CP with mean discrepancies less than 6%, but larger discrepancies for pressure gradient are found among the various friction factor correlations. Furthermore, the new correlations are implemented in a process model with six spiral wound modules in series and the predicted recovery, pressure drop, and specific energy consumption are compared with a reference case obtained by ROSA (Reverse Osmosis System Analysis, The Dow Chemical Company). Differences in predicted recovery and pressure drop are up to 5% and 83%, respectively, highlighting the need for careful selection of correlations when using predictive models in process design. Compared to existing mass transfer correlations, a distinct advantage of our correlations for CP modulus is that they can be directly used to estimate the impact of permeate flux on CP at a membrane surface without having to resort to the film theory.

CFD prediction of flow, heat and mass transfer in woven spacer-filled channels for membrane processes

Flow and heat or mass transfer in channels provided with woven spacers made up of mutually orthogonal filaments were studied by Computational Fluid Dynamics. The problem addressed was the combined effect of the parameters that characterize the process: pitch to height ratio P/H (2, 3 and 4), flow attack angle θ (0, 7, 15, 20, 30, 40 and 45°) and Reynolds number Re (from ~1 to ~4000). The Prandtl number was 4.33, representative of water at ~40°C, while the Schmidt number was 600, representative of NaCl solutions. Simulations were performed by the finite volume code Ansys CFX™ 18.1 using very fine grids of ~6 to ~14 million volumes. For Re > ~400, the SST turbulence model was used to predict flow and heat transfer; no simulations of mass transfer were performed in the turbulent regime because the resolution of the diffusive sublayer would have required a prohibitive number of grid points. Results were validated against experimental data, including results obtained by Liquid Crystal Thermography and Digital Image Processing. The flow attack angle θ = 45° was the most effective for mixing (higher Nusselt number, Nu, and Sherwood number, Sh) and caused lower values of friction coefficient (f). In the range investigated, increasing the pitch to height ratio P/H caused Nu, Sh and f all to decrease. Therefore, the highest values of Sh and Nu were provided by the configuration P/H = 2, θ = 45°. Compared with non-woven spacers, woven spacers provided a better mixing, especially at intermediate values of Re, but at the expenses of higher pressure drops.

Investigate of Hydrodynamic and Mass Transfer in the Spacer-Filled Channel of Reverse Osmosis Module

The feed channel spacers cause the membrane plates to be separated. These mesh spacers increase the pressure drop in the channel and, in contrast, improve the mass transfer process. In this study, investigate hydrodynamics and mass transfer in the spacer-filled channel in the reverse osmosis module by using the simulation of computational fluid dynamics coupled with the response surface method. Input parameters include the average inlet velocity, the attack angle, the mesh angle, and the output parameters include the pressure drop over the computational domain and the water flux across the membrane walls. The Latin hypercube sampling design method was used to sample the input parameters and the Kriging model has been used for the response surface model. Also, genetic algorithms and screening were used to determine the optimal output parameters. The sensitivity analysis of the input parameters on the output parameters indicates that the average inlet velocity and the attack angle are the most and the least influential parameters, respectively. The optimum configuration geometry taking the values of both output parameters (pressure drop and water flux) into account was stood up at the attack angle of 72.74 degrees, the mesh angle of 85.19 degrees, and the inlet velocity of 0.13 m/s.

Polyzwitterionic hydrogel coating for reverse osmosis membranes by concentration polarization-enhanced in situ “click” reaction that is applicable in modules

The methodology for a polyzwitterionic anti-fouling hydrogel coating for reverse osmosis polyamide (PA) thin-film composite (TFC) membranes by concentration polarization-enhanced in situ thiol-ene “click” reaction has been developed. A copolymer with zwitterionic sulfobetain and reactive methacrylate side groups as well as a bis-thiol crosslinker in water were used as reactive system. By means of rheology, best suited solution composition parameters for efficient cross-linking at ambient temperature toward stable hydrogels were established first. Thereafter, factors that influence hydrogel coating of PA TFC membranes were investigated in dead-end filtrations, such as copolymer concentration, flux and stirring speed. It was found that hydrogel formation will occur within the first few minutes if the critical reactant concentration required for cross-linking is reached at the membrane surface and further filtration/reaction time will increase hydrogel layer thickness. Specific parameters, selected based on results of dead-end filtration experiments yielding thick hydrogel coatings (1–2 μm, in dry state), lead to only very thin hydrogel layers under cross-flow conditions in a spacer-filled channel. However, such thin hydrogel-coated membranes had also very good antifouling properties compared to the unmodified membrane. The extent of coating can be adjusted toward thicker hydrogels by increasing flux also under cross-flow conditions in a spacer-filled channel. Finally, the feasibility of the hydrogel coating of PA TFC membranes in industrial spiral-wound modules and the use of such modules for treatment of cooling water in a steel manufacturing plant were demonstrated. Overall, suited materials and methods as well as partial fundamental understanding of the influence of parameters that can be used for a scalable antifouling hydrogel coating of membranes in spiral-would modules have been established in this work.

Three-dimensional numerical investigation of the displacement of shear-thinning milk protein concentrates in spacer-filled channel

Rinsing is an important part of the cleaning procedure applied to the spiral-wound membrane (SWM) modules in the dairy industry. In this work, we numerically investigated the displacement of non-Newtonian reconstituted milk protein concentrates in a feed spacer channel using OpenFOAM and compared the results with experimental data obtained in an SWM pilot plant. The model consists of the classical mass and momentum balance equations for an incompressible viscous mixture coupled with an advection-diffusion equation for the milk concentration. The power-law model was utilized to describe the shear-thinning viscosity of the milk protein concentrates. The shear-thinning behavior was further assumed to depend on the milk protein content. The calculations confirmed significantly shorter rinsing times and lower mixed-phase volumes for lower milk protein concentrations. The rinsing time can further be lowered by increasing the volumetric flow rate. Through the numerical simulations, we identified nearly inaccessible zones behind the filament crossings that prolong the rinsing process.

Impact of non-Newtonian fluid behavior on hydrodynamics and mass transfer in spacer-filled channels

Spiral wound membrane modules operate as filtration modules in the food, beverage, and pharmaceutical industries. As many fluids are non-Newtonian or become non-Newtonian during concentration, it is essential to gain an understanding of the effect of a shear-rate dependent viscosity. This computational work examines the impact of the fluid rheology and the Reynolds number on the hydrodynamics and the mass transfer in zigzag and cavity spacer-filled channels under laminar flow conditions. To describe the rheology of the working fluid, we utilized the well-known power-law model. The power-law index values corresponded to 0.7, 1, and 1.3, representing shear-thinning, Newtonian, and shear-thickening behavior, respectively. The Reynolds number was varied up to 160 whereas the Schmidt number was kept constant at 500. A standard convection–diffusion equation with a constant wall concentration was employed to describe the mass transfer. In agreement with previous works on Newtonian fluids, the zigzag spacer was found to be the most promising spacer type, because of the enhanced mass transfer in the reattachment regions. Whereas the mass transfer was only slightly affected by the rheology, the shear thinning fluid produced the smallest pressure drop. As a direct consequence of the positive effect on the pressure drop, the spacer efficiency was highest in all configurations. The results of this first numerical investigation in the context of non-Newtonian fluid flow through spacer-filled channels emphasize the importance of taking into account a varying fluid viscosity in the design and operation of the filtration process.

Incipient membrane scaling in the presence of polysaccharides during reverse osmosis desalination in spacer-filled channels

This study aims to shed light into the complicated phenomena occurring during the early stages of RO-membrane scaling when organic-foulants are present. Experiments were performed, using spacer-filled channel in once-through flow-mode, closely simulating conditions prevailing at tail elements of pressure-vessels. The effect was studied of a typical foulant (polysaccharide, sodium-alginate, SA), at small concentrations (~2 mg/L and ~10 mg/L), on incipient crystallization/deposition of calcium sulfate (CaSO4·2H2O, gypsum) during RO-desalination of synthetic brackish-water at small super-saturation ratio S (1.0 to 1.5). Scanning Electron Microscopy and membrane-scale/foulants dissolution techniques were employed. At small SA concentration (~2 mg/L) incipient-scaling inhibition is observed (likely due to crystallite-growth retardation by adsorbed organic molecules); however, at higher SA concentration (~10 mg/L), significant enhancement of incipient scaling occurs, attributed to formation of coherent organic-gel fouling-layer, favoring concentration increase of inorganic-scalants at the membrane-surface and consequent increase of supersaturation. Under such conditions, although the fouling-layer thickness remains roughly constant (due to constant deposited organic-matter), the specific fouling resistance α tends to significantly increase with increasing supersaturation, likely due to physico-chemical structural changes within the alginate gel-layer. The techniques employed allow determination and correlation of key fouling/scaling parameter-values (i.e. scale-mass deposition-rate and resistance α), that are necessary for developing reliable process modeling/simulation tools.