Membrane technology has become a fundamental unit operation in the industry and society of nowadays and fouling is, probably, the most important concern related with this technology. Fouling is a complex process that can limit the performances of facilities using membranes. Many research efforts have been done in order to reduce fouling tendency. Ceramic membranes can play a major role in fouling mitigation due to its high hydrophilic nature. This paper describes the characterization of a new ceramic nanofiltration (NF) prototype membrane with increased surface and modified in its active surface, which makes it more resistant to fouling. The main goal of this paper was to characterize, under different operating conditions, the membrane performance. Authors have used two model foulants: peptone (meat extract) and humic acids as mimicking fouling substances usually present in natural waters and wastewaters. Tests consisted of using different concentrations of these model foulants; varying the pH (6.0-9.0) and using different cross flow velocities (CVF) from 0.5 to 1.5 m/s. Influence of calcium on foulant deposition onto membrane has also been studied. Results show that this new membrane showed resistance to fouling while conserved a high permeability and rejection.

The purpose of this research was to visualize the fouling process of a flat-sheet polymeric membrane into a flow cell, using particles to study their deposition onto the membrane surface. This set of experiments was analyzed from an imagistic point of view, designing for this purpose a measuring installation where hydrodynamic surface evaluation was carried out with an image processing concerning to the reverse osmosis operation. To ensure the measurements accuracy, calculations, logical approximation, and comparisons were made with existing and verified models, revealing that the differences were insignificant.

Cross flow filtration is the typical way that water is filtered in membrane technology; that means that feed solution passes tangencially over the membrane and rejected components are washed away of the membrane by the rejected stream. In such a way, that minimal solids building up and at constant low flow resistance are achieved. In this paper, a calulation method regarding to the value of cross-section active area for a polymeric spiral wound reverse osmosis (RO) membrane is presented, in order to obtain the value of the cross-flow velocity of the system. This velocity is needed to improve the knowledge fouling mechanisms and it is not easy to know without obtaining the cross section area. To determine cross-section area of a RO polymeric spiral wound membrane a series of calculations were performed to obtain the initial values of some parameters. The mathematical calculation was also achieved with the Roll Length program. Based on the results obtained, it was concluded that only 65.36% of the total cross-section of the membrane is useful to cross flow and it was possible to determine the active cross-section of filtration with a value of 1,915.4 mm2, for the membrane studied. This methodology allows the calculation for any RO spiral membrane.

A mathematical model regarding water filtration with a nanofiltration (NF) titanium dioxide ceramic membrane is presented. The experiments aimed to use the excitation-emission matrix (EEM) spectroscopy method to highlight the existence of humic acid (HA) in water, before and after the NF process. Following the established operating conditions, experiments were performed for each quantity of AH separately, leaving the installation to work at the appropriate parameters for 15 minutes. for each quantity of AH. The analyzes for EEM fluorescence were performed using the FP-8300 spectrofluorimeter. The collected samples were analyzed with Spectra Manager II software on fluorescence intensity (au - arbitrary units), with an emission wavelength (nm) between 460 and 640 nm and with an excitation wavelength (nm) between 350 and 600 nm. Following the experiments carried out, mathematical correlations were established between the parameters that influence the filtering process and the studied parameters. It is worth mentioning that as a result of the experiments carried out, a number of 20,450 values were obtained, which were used for the elaboration of mathematical models. These models, for sets of values of the order of tens of thousands, verified both from the point of view of the real values and from the point of view of the regression coefficients (coefficients close to the value 1), demonstrate the quantity and the very good quality of the experimental data, respectively of the measured and calculated sizes. In order to validate the generated equations, they were subjected to checks, the difference being obtained between the value obtained by experimental means and the value obtained within the mathematical model. And the value of the resulting relative error, gives information on the accuracy (truth) of the mathematical model, so that it can be extended to other experiences. It turns out that this method cannot quantitatively determine the value of a parameter, but it can highlight the presence and differences between two samples.

This paper presents a mathematical modeling for a series of experiments in which humic acid (AH) and calcium chloride (CaCl2) were used, in order to visualize the amount of contaminant before and after the nanofiltration (NF) process, using Excitation Emission Matrix Spectroscopy (EEMS). It allows to a better understanding of membrane fouling. The membrane used for these experiments was a NF ceramic membrane made of titanium dioxide (TiO2). For the experimental determinations, a constant amount of 10 mg/L HA and different amounts of CaCl2, respectively 1, 2, 3 and 4 mmol/L were used, considering the working methodology presented in this article. The presence of the amount of contaminant in water was determined using the EEMS method using the FP-8300 Spectrophotometer, after which a spectral analysis was performed. TableCurve 3D software was used to make the mathematical models in order to ensure that the equations obtained had the same shape. The values of the correlation coefficients, corresponding to the generated equations, have values ranging from 0.91 to 0.93. In order to verify the mathematical models thus obtained, graphs of the difference between the surface obtained with the help of the mathematical models and the surface obtained by means of real data were drawn. In conclusion, it turns out that, the largest difference was obtained in the case of samples taken from the feed, with a maximum difference of 31 fluorescence intensity arbitrary units (a.u.), and for the samples taken from the permeate the deference is 14 fluorescence intensity a.u.

A high importance is given to the studies concerning the most reliable mixing process with a minimum of energy consumption, because the mixing process is an often used operation in various industries. The main purpose of this paper is to determine and to identify the behavior of the dispersed phase, in this case, the solid particle, during the mixing process. Through the experiment, the mixing process was recorded using a High-Speed camera, which enables following the behavior of the solid particle. The resulting data were used for different types of charts.