Hybrid desalination processes for beneficial use of reverse osmosis brine: Current status and future prospects

© 2018 Elsevier B.V. As water shortage has increasingly become a serious global problem, desalination using seawater reverse osmosis (SWRO) is considered as a sustainable source of potable water sources. However, a major issue on the SWRO desalination plant is the generation of brine that has potential adverse impact due to its high salt concentration. Accordingly, it is necessary to develop technologies that allow environmentally friendly and economically viable management of SWRO brines. This paper gives an overview of recent research works and technologies to treat SWRO brines for its beneficial use. The treatment processes have been classified into two different groups according to their final purpose: 1) technologies for producing fresh water and 2) technologies for recovering energy. Topics in this paper includes membrane distillation (MD), forward osmosis (FO), pressure-retarded osmosis (PRO), reverse electrodialysis (RED) as emerging tools for beneficial use of SWRO brine. In addition, a new approach to simultaneously recover water and energy from SWRO brine is introduced as a case study to provide insight into improving the sustainability of seawater desalination

Assessing the removal of organic micro-pollutants from anaerobic membrane bioreactor effluent by fertilizer-drawn forward osmosis

© 2017 Elsevier B.V. In this study, the behavior of organic micro-pollutants (OMPs) transport including membrane fouling was assessed in fertilizer-drawn forward osmosis (FDFO) during treatment of the anaerobic membrane bioreactor (AnMBR) effluent. The flux decline was negligible when the FO membrane was oriented with active layer facing feed solution (AL-FS) while severe flux decline was observed with active layer facing draw solution (AL-DS) with di-ammonium phosphate (DAP) fertilizer as DS due to struvite scaling inside the membrane support layer. DAP DS however exhibited the lowest OMPs forward flux or higher OMPs rejection rate compared to other two fertilizers (i.e., mono-ammonium phosphate (MAP) and KCl). MAP and KCl fertilizer DS had higher water fluxes that induced higher external concentration polarization (ECP) and enhanced OMPs flux through the FO membrane. Under the AL-DS mode of membrane orientation, OMPs transport was further increased with MAP and KCl as DS due to enhanced concentrative internal concentration polarization while with DAP the internal scaling enhanced mass transfer resistance thereby lowering OMPs flux. Physical or hydraulic cleaning could successfully recover water flux for FO membranes operated under the AL-FS mode but only partial flux recovery was observed for membranes operated under AL-DS mode because of internal scaling and fouling in the support layer. Osmotic backwashing could however significantly improve the cleaning efficiency

Striation mechanism and triggered striation in dielectric microdischarge plasma

The striation mechanism of dielectric microdischarges, as in many plasma devices, is extensively explored by collisional kinetic and fluid simulations. Striation in a typical dielectric microdischarge device predominantly occurs near the anode region and is basically governed by the ionization-dominated ??-processes, wherein surface and space charges collectively dictate the phenomenon in a complex manner. A novel type of striation has been investigated by us near the cathode region, which is dominated by ??-processes and is driven by the secondary-electron emission mechanism.close101

Antioxidant, antibacterial, cytotoxic, and apoptotic activity of stem bark extracts of Cephalotaxus griffithii Hook. f

<p>Abstract</p> <p>Background</p> <p><it>Cephalotaxus </it>spp. are known to possess various therapeutic potentials. <it>Cephalotaxus griffithii</it>, however, has not been evaluated for its biological potential. The reason may be the remoteness and inaccessibility of the habitat where it is distributed. The main aim of this study was to: (1) evaluate multiple biological potentials of stem bark of <it>C. griffithii</it>, and (2) identify solvent extract of stem bark of <it>C. griffithii </it>to find the one with the highest specific biological activity.</p> <p>Methods</p> <p>Dried powder of stem bark of <it>C. griffithii </it>was exhaustively extracted serially by soaking in petroleum ether, acetone and methanol to fractionate the chemical constituents into individual fractions or extracts. The extracts were tested for total phenolic and flavonoid content, antioxidant (DPPH radical scavenging, superoxide radical scavenging, and reducing power models), antibacterial (disc diffusion assay on six bacterial strains), cytotoxic (MTT assay on HeLa cells), and apoptotic activity (fluorescence microscopy, DNA fragmentation assay, and flow cytometry on HeLa cells).</p> <p>Results</p> <p>Among the three extracts of stem bark of <it>C. griffithii</it>, the acetone extract contained the highest amount of total phenolics and flavonoids and showed maximum antioxidant, antibacterial, cytotoxic (IC₅₀of 35.5 ± 0.6 μg/ml; P < 0.05), and apoptotic (46.3 ± 3.6% sub-G0/G1 population; P < 0.05) activity, followed by the methanol and petroleum ether extracts. However, there was no significant difference observed in IC₅₀values (DPPH scavenging assay) of the acetone and methanol extracts and the positive control (ascorbic acid). In contrast, superoxide radical scavenging assay-based antioxidant activity (IC₅₀) of the acetone and methanol extracts was significantly lower than the positive control (P < 0.05). Correlation analysis suggested that phenolic and flavonoid content present in stem bark of <it>C. griffithii </it>extracts was responsible for the high antioxidant, cytotoxic, and apoptotic activity (P < 0.05).</p> <p>Conclusions</p> <p>Stem bark of <it>C. griffithii </it>has multiple biological effects. These results call for further chemical characterization of acetone extract of stem bark of <it>C. griffithii </it>for specific bioactivity.</p

Modeling of magnetron sputtering plasmas

Partially ionized, low-temperature plasmas have been used extensively in many areas of technology. These applications of plasma include surface processing and lighting devices. There are three major categories in surface processing: sputtering, etching and surface modification. The examples of lighting device application are light bulbs, lasers and plasma display devices. In this discussion, simulation study of magnetron sputtering system are reviewed and future issues of these systems are discussed. A two-dimensional three-velocity particle-in-cell (PIC) code is used to simulate kinetic plasma properties in a planar magnetron system with realistic magnetic fields in two and three dimensions. Various plasma characteristics and erosion profiles of a target material are obtained with these magnetic fields. Scaling formulas are used in order to estimate the steady-state properties of plasma and reduce computation time. Variations in the geometry and the magnetic field optimize these erosion profiles and plasma characteristics. For the plasma characteristics, we also calculate the plasma temperature and the velocity distribution function. The velocity distribution function of electrons is nearly Maxwellian, while that of ions is non-Maxwellian. The electron temperature in the bulk coincides well with the experimentally measured values. The majority of ions are in the energy range below half of the applied voltage. (C) 2002 Published by Elsevier Science B.V.X1158sciescopu

Striation phenomenon in the plasma display panel

A detailed analysis, based on kinetic and fluid simulations, of striation phenomenon in the plasma display panel cell has been presented. Numerical studies indicate that the phenomenon of striation occurs primarily due to the accumulation of space charge near the anode electrode. These space charges locally create multiple-layer potential distribution near the anode region. The ion density in the vicinity of this region groups up due to ionization processes, which are caused by electron species. However, the electrons are further attracted by the anode. Well-like deformations occur in the anode potential distribution, which confine electrons and produce density humps. On the contrary, cathode plasma density depends on the secondary-electron emission by ions that are attracted to the anode dielectric surface. (C) 2001 American Institute of Physics.open1139sciescopu

Method to increase the simulation speed of particle-in-cell (PIC) code

An algorithm for time reduction is implemented to an existing particle-in-cell (PIC) code to simulate plasma systems. The algorithm not only guarantees higher simulation speed than the original one but also conserves position, charge density, and energy of the system. Position and charge density are conserved by grouping particles in one cell and energy is conserved by dividing velocity space to several groups. Particle number is reduced by grouping particles that have similar magnitudes and directions of velocity to conserve the total system energy. The speed is improved from two to five times by reducing the simulation particle-numbers in the system. As the particle number is reduced, the stability of code is also improved. (C) 2001 Elsevier Science B.V. All rights reserved.X1110sciescopu