جستجوی مقالات مرتبط با کلیدواژه « fouling » در نشریات گروه « پزشکی »

The Beni Saf Water Company (BWC) desalination plant in Ain Témouchent (Algeria) uses reverse osmosis technique. This process, which is based on dense membranes operating at high pressure, produces a permeate with characteristics that exceeds the necessary requirements. However, the Reverse Osmosis (RO) technique suffers from the following limitations: high energy consumption, low water recovery and excessive fouling of membranes. We conducted this work to contribute to the study of seawater desalination by introducing another system such as Nanofiltration (NF) to reduce energy consumption and retard the fouling of RO membranes. This research study is focused on the installation of Nanofiltration membranes to desalinate seawater with a salinity of about 35mg/L, in order to protect RO membranes and reduce their fouling. NF was found to be effective for partial and selective desalination of the studied seawater in single or two stages, with lower energy consumption than RO. The ESNA1-LF-LD Nanofiltration membrane is more suitable and competitive compared to SWC4-LD for seawater desalination with a 99% removal rate of multivalent ions. It allows for partial desalination and also allows for the preparation of water for industrial use (cooling....) at twice the pressure and at higher conversion rates (90%). These characteristics provide system designers with new options to reduce the capital cost of the system as well as the operating costs.

In this study, polysulfone (PSf) nanocomposite membranes embedded with functionalized nanodiamond (ND) were prepared via Non-Solvent Induced Phase Separation (NIPS) method. ND nanoparticles were silanized by using the esterification reaction of hydrolyzed vinyltrimethoxysilane (VTS) in alcoholic solution in order to enhance the compatibility between ND and PSf. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that ND nanoparticles were successfully functionalized by silane groups. Nanocomposite membranes were then prepared with different percentages of silanized NDs (SNDs). The membranes were characterized using a set of analyses and the results showed that the addition of SNDs up to 1.0 wt.% resulted in an increase in hydrophilicity, water content, porosity and water flux of membranes. Moreover, Scanning Electron Microscopy (SEM) images indicated that the membrane with 1.0 wt. % nanoparticles had more pores on the membrane surface with smaller average pore size in comparison to other membranes. Antifouling properties of the membrane was also investigated in filtration of humic acid solution and the results showed that reversible fouling and flux recovery of membranes increased at the presence of SNDs.

Various suspended organic and inorganic contaminants including biological deposits, different types of algae and barnacles and causative factors of water turbidity result in irreparable damages to pretreatment systems and membranes in reverse osmosis systems. In this study, the effect of injection of disinfectant materials such as calcium hypochlorite on the reduction of silt density index (SDI) value at the inlet of reverse osmosis system has been investigated. In this research, correlations between fundamental parameters in pretreatment system such as turbidity, chlorine injection, residual chlorine content and SDI values were thoroughly analyzed and evaluated at one of the desalination plants located in Persian Gulf. The results indicated that there is a close link between the amount of chlorine injection and SDI inlet value. By adjusting the nephelometric turbidity unit values in specific ranges of 35 - 55, 55 - 80 and 80 - 150 and oxidation reduction potential in the ranges of 280 - 680, 315 - 680 and 420 - 680 mV, favorable SDI value of inlet water was obtained. SDI control via chlorine injection increased the lifetime of cartridge filters at reverse osmosis input units and reduced the operation costs significantly.

Membrane ultrafiltration (UF) is widely used in dairy industries like milk concentration and dehydration processes. The limiting factor of UF systems is fouling which is defined as the precipitation of solutes in the form of a cake layer on the surface of the membrane. In this study, the combined cake filtration-complete blocking model was compared to cake filtration mechanism for flux data through ultrafiltration of skim milk at constant flow rate. The resistance data also was modeled using cake filtration model and standard blocking model. The effect of different trans-membrane pressures and temperatures on flux decline was then investigated. Based on the results obtained here, the combined complete blocking-cake formation model was in excellent agreement with experimental data. The cake filtration model also provided good data fits and can be applied to solutions whose solutes tend to accumulate on the surface of the membrane in the form of a cake layer. With increasing pressure, the differences between the model and experimental data increased.

Beer is the most consumed beverage after tea, carbonates, milk and coffee in the world and it continues to be a popular drink. One of the important reason for its popularity is that beer is a drink with a pleasant flavor, an attractive color and also because of its clarity. So, Membrane separation technology has become widely used in the food processing industryto attain these characteristics.As advantages of membrane filtration are included maintainingdissolved macromolecules that give the beer its flavor and functional properties while causes removal of yeast cells and turbidity colloids and also, reducing the components that cause turbidity of the bottled beer.Because of the potential of cross-flow microfiltration as a separation method for brewery, it has been investigated in the many of recent studies. Clarification of rough beer (RB) and pasteurization of clarified beer (CB) are as an application of cross-flow microfiltration (CFMF) in brewery. An important limitation in the performance of membrane processes is the fouling mechanism and the general effect of these phenomena, known as concentration polarization have described briefly in this review article. Moreover, the influence of important parameters in the filtration process such as temperature, pressure,type of membrane, pore size and the use of stamped membrane have been discussed.

Antibiotics such as amoxicillin and cephalexin are a group of pharmaceutical compounds in human medicine practice that have been entered in water bodies. Presence of these compounds in the environment has raised concerns regarding the toxicity to aquatic organisms and the emergence of strains of antibiotic-resistant bacteria. Removal of these substances before entering the aquatic environment as well as water reuse plant is very important. The objective of this investigation was to evaluate the impact of hydrophilic and hydrophobic fractions of Natural Organic Matter (NOM) on the removal efficiency of cephalexin and amoxicillin, by using two different commercially available composite NF membranes (TFC-SR2 and TFC-SR3). In addition, the effect of NOM fractions on retention mechanism and permeates flux behavior was studied. Amoxicillin and cephalexin were used as models of antibiotics; alginate and humic acid were used as models of hydrophilic and hydrophobic fractions of NOM, respectively. It was observed that the rejection and permeate flux of amoxicillin and cephalexin were influenced by the membrane characteristics and properties of NOM. The results showed that as the alginate proportion was increased, the rejection improved. The permeate flux decreased with increasing alginate ratio. It was observed that the rejections of amoxicillin and cephalexin in TFC-SR2 were >97.3% and >95.8% in all experiments, respectively. In TFC-SR3, the rejection percentage were (95.9%-100%) and (86.1%-96.3%), respectively. Alginate and humic acid had synergistic effect on flux decline. In other words, increasing alginate concentration increased the rate and extent of flux reduction.