Salts brine rejection

Acid addition is commonly used to convert bicarbonates into the more soluble sulfate salts to reduce the alkalinity of the RO RW, which in turn modifies the brine reject water LSI. Sometimes it is required to maintain the pH level within membrane limits. Additionally, it may be used in conjunction with a reduced dosage of antiscalent chemical to reduce the overall chemical treatment costs. 

Water is probably the most important and the most intensely studied substance on Earth. It is the solvent of life and it is also of vital importance in many aspects of our existence, ranging from cloud microphysics to its key role as a solvent in many chemical reactions. The familiar process of water freezing is encountered in many natural and technologically relevant processes. In this contribution, we discuss the applicability of the methods of computational chemistry for the theoretical study of two important phenomena. Namely, we apply the molecular dynamics (MD) simulations to the study of brine rejection from freezing salt solutions and the study of homogeneous nucleation of supercooled water. 

These simulations can be easily extended to systems containing solutes, namely simple salts. However, most of the reported simulation studies concerned only the behavior of the solute at the stable ice/water interface.Only recently results of successful simulations of the brine rejection process involving a moving ice/solution boundary have been reported. 

We applied the MD technique to the simulation of brine rejection from freezing salt solutions employing the rigid 3-site simple point charge (SPC/E) water model to obtain the microscopic picture of this very important natural process. Further, we used a recently... 

We investigated freezing of water and salt solutions by means of molecular dynamics simulations. We first established a robust simulation protocol for water freezing and than applied this approach to the study of the brine rejection process. Brine rejection was observed for a series of systems with varying salt concentration. We showed the anti-freeze... 

Electrodialysis. Electro dialysis processes transfer ions of dissolved salts across membranes, leaving purified water behind. Ion movement is induced by direct current electrical fields. A negative electrode (cathode) attracts cations, and a positive electrode (anode) attracts anions. Systems are compartmentalized in stacks by alternating cation and anion transfer membranes. Alternating compartments carry concentrated brine and purified permeate. Typically, 40—60% of dissolved ions are removed or rejected. Further improvement in water quaUty is obtained by staging (operation of stacks in series). ED processes do not remove particulate contaminants or weakly ionized contaminants, such as siUca. 

In trials at different feedwater concentrations, the FT-30 membrane showed single-pass seawater desalting capabilities at up to 6.0 percent synthetic seawater. Basically, any combination of pressure and brine concentration at room temperature that gave a membrane flux of 15 gfd also resulted in a 99 percent level of salt rejection. 

In summary, the FT-30 membrane is a significant improvement in the art of thin-film-composite membranes, offering major improvements in flux, pH resistance, and chlorine resistance. Salt rejections consistent with single-pass production of potable water from seawater can be obtained and held under a wide variety of operating conditions (ph, temperature, pressure, and brine concentration). This membrane comes close to being the ideal membrane for seawater desalination in terms of productivity, chemical stability, and nonbiodegradability. 

Biological fouling was monitored using the customary indicators of RO performance, including flux (productivity), salt passage, and bundle pressure drops (AP). In addition, the total bacteria count (TBC) of the RO feed water and the reject brine stream were also obtained using the membrane filtration method (Ref. 6). The increase in TBC between the feed and reject portions of the system had been found in the preliminary stages of... 

Ahmed M., Arakel A., Hoey D., Thumarukudy M.R., Goosen M.F.A., Al-Haddabi M., and Al-Belushi A., Feasibility of salt production from inland RO desalination plant reject brine A case study. Desalination 158 2003 109-117. 

RO is used to treat 1.31 m3/s of seawater at 293 K containing 3.5 wt% dissolved solids to produce 0.44 m3/s of potable water with 500 ppm of dissolved solids. The feed-side pressure is 138 bar, while the permeate pressure is 3.4 bar. A single stage of spiral-wound membrane is used that approximates crossflow. If the total membrane area is 0.10 km2, estimate the permeance for water and the salt rejection. Assume that the densities of the seawater and of the brine are approximately equal to the density of pure water. 

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