RO Applications Research Articles

Crosslinked Spin-Assisted Layer-by-Layer Polyelectrolyte Nanofiltration Membrane: From Literature Review to Experiment

Layer-by-Layer (LbL) assembly is considered as the most versatile and robust method in thin-film fabrication. However, its use in the preparation of desalination membrane is still in its infancy. Spin-assisted layer-by-layer assembly (SA-LbL), one of the LbL variants, was selected for the fabrication of a nanofiltration membrane due to its versatility to produce an ultra-thin film with highly controlled film properties within an incredibly short time. Branched-polyethyleneimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS) were employed and alternately deposited on the top of the ultrafiltration polyethersulfone (PES) substrate. PEI/PSS film was then crosslinked using Gluteraldehyd (GA). The resulting membrane was tested at a feed concentration of 2000 ppm NaCl, a pressure of 10 bar, and a temperature of 25°C. Crosslinking time and many layers were varied to investigate the extent of crosslinking and its impact on membrane performance. The permeation test of (PEI/PSS)10 crosslinked for 6 hours showed rejection of 94.2 % and water flux of 4.2 L/h·m2 meanwhile uncrosslinked (PEI/PSS)35 showed rejection of 75.66% only. The result showed that crosslinking improved the rejection of NaCl with a smaller number of layers. This result also displayed SA-LbL method is promising and can be used to produce membrane suitable for NF or RO application.

Improving permeability and anti-fouling performance in reverse osmosis application of polyamide thin film nanocomposite membrane modified with functionalized carbon nanospheres

• –COOH and Ag-functionalized carbon nanospheres are successfully synthesized. • TFN membranes containing functionalized CNs are prepared for RO application. • Carboxyl groups in nanofillers significantly influence the membrane structure. • TFN-Cs-COOH membrane shows high water flux of 63 LMH and NaCl rejection over 96.8%. • The TFN–Cs–COOH/Ag membrane possesses remarkable anti-bacterial property. In this study, carboxyl group-functionalized carbon nanospheres (CNs–COOH) and silver-coated products (CNs–COOH/Ag) were successfully realized and used as nanofillers to fabricate thin-film nanocomposite (TFN) membranes via the interfacial polymerization of m -phenylenediamine (MPD) and trimesoyl chloride (TMC) solutions. The structure of the functionalized CNs modified TFN membranes (TFN–Cs–COOH, TFN–Cs–COOH/Ag) was significantly different from that of the CNs modified TFN (TFN–Cs) and TFC membranes, as the carboxyl groups in the nanofillers strongly influence the process of interfacial polymerization. The permeability and anti-fouling performances of the TFN membranes were significantly enhanced owing to the changes in the membrane structure. The water fluxes of the TFN–Cs–COOH and TFN–Cs–COOH/Ag membranes were respectively 91.9% and 73.2% higher than that of the TFC membrane, with the NaCl rejection exceeding 96%. The nanofillers of CNs–COOH/Ag with monodispersed silver nanoparticles (NPs) resulted in outstanding anti-bacterial performance in the TFN–Cs–COOH/Ag membrane. Overall, this work demonstrates that, when functionalized carbon NPs are used as nanofillers, the practical performance of TFN membranes can be improved for reverse osmosis.

2D nanosheet enabled thin film nanocomposite membranes for freshwater production – a review

This review presents state-of-the-art progress in 2D-enabled TFN membranes for RO and NF applications in water treatment with emphasis on impact of 2D nanosheet on membrane properties, performance, and its associated challenges.

Fouling behavior of calcium phosphate in direct contact membrane distillation

Abstract Membrane distillation is a potential technology to recover more water from the RO brine concentrate for the purpose of high water recovery and zero liquid discharge. However, since calcium phosphate scaling has been widely reported in RO applications, it could also hinder high feed water recovery in the reclamation of wastewater by membrane distillation. In this study, the calcium phosphate saturated feed was used to mimic the RO concentrate, and the fouling mechanism of calcium phosphate on the membranes in direct contact membrane distillation (DCMD) was investigated. Membrane fouling was quantified by permeate flux decline and membrane wetting monitored by variation of the permeate conductivity. Influence of concentration, stream velocity, temperature and pH on the fouling behavior of the calcium phosphate suspension were presented. It was found that both the elevating temperature and turbulence could enhance the calcium phosphate fouling under the testing conditions, due to the crystallization incurred fouling in combination with the boundary effects. Low pH would suppress membrane as expected, and adjusting the suspension’s pH to as low as 4 could effectively inhibit the membrane fouling in the studied water recovery range. It was found that the calcium phosphate fouling will result flux decline and membrane wetting due to the lowering the membrane hydrophobicity (contact angle). Furthermore, the fouling incurred by the crystallization/precipitation of calcium phosphate has more influence on permeate flux than that incurred by the settlement of the suspended calcium phosphate.

Thin film nanocomposite membranes filled with MCM-41 and SBA-15 nanoparticles for brackish water desalination via reverse osmosis

This work aimed to investigate the impact of filling MCM-41 and SBA-15 nanoparticles (NPs) on the performance of thin film nanocomposite membranes that applied in reverse osmosis, where SBA-15 is firstly reported here for this purpose. The membranes were prepared via the interfacial polymerization reaction between m -phenylenediamine (MPD) aqueous solution and trimesoyl chloride (TMC)-isooctane solution on a support sheet of polyethersulfone. The reaction time in the presence of NPs was investigated by fixing MPD contact time at 75 s; it was found that 30 s is the optimum TMC contact time. Different loading ratios in the range of 0-0.15 wt% were applied to fill the NPs inside the membranes. Scanning electron microscope (SEM), X-ray Diffractometer (XRD), Fourier-transform infrared spectroscopy (FTIR), and N 2 adsorption/desorption tests were used to study the NPs characterizations. While SEM, contact angle, mechanical strain and strength, and membrane performance tests were conducted to study the membranes properties. Results showed that in both nanoparticles (i.e. MCM-41 and SBA-15) cases, 0.1 wt% was the optimum filling percentage. When SBA-15 was loaded, water flux increased from 40 to 74.17 L.m −2 .h −1 (LMH), and NaCl rejection increased from 95.1 to 98.5% comparing with the plain membrane. While when the optimum MCM-41 ratio was loaded, water flux and NaCl rejection raised to 60 LMH and 96.9%, respectively. The performance test conditions were 15 bar, 25 °C, and 2500 NaCl feed concentration. • MCM-41 and SBA-15 NPs were filled in TFN membranes. • Both additives improved the membranes performance. • SBA-15 is firstly reported as a filler for RO application. • SBA-15 effect was higher on the membranes water flux and salt rejection.

Characterization of colloidal fouling in forward osmosis via ultrasonic time- (UTDR) and frequency-domain reflectometry (UFDR)

Ultrasonic time- (UTDR) and frequency-domain reflectometry (UFDR) were applied to characterize internal and external fouling in the forward osmosis (FO) process. Unlike RO applications, in which the transducer was placed above the membrane to detect external fouling on the top surface of membrane, the transducer was placed below the membrane to enable detection of internal and external fouling in an FO application. The amplitude changes and arrival-time shifts in UTDR were more sensitive than the flux decline as an indicator of FO fouling. In the active-layer facing the feed solution (AL-FS) mode, the cake-layer thickness obtained via the differential UTDR signal agreed well with the mass-balance data. The Short-Time-Fourier-Transform (STFT) analysis permitted decomposing the non-overlapping peaks that revealed a significant decrease in the amplitudes of the high-frequency components due to the grain-scattering effect in the active-layer facing the draw solution (AL-DS) mode. In contrast, the frequency distribution remained unchanged in the AL-FS mode. The total reflected power (TRP) calculations for the arrival-times and principal peaks in the frequency-domain correlated well with the overall fouling and internal fouling, respectively.

The Impact of Power Distance and Uncertainty Avoidance on Real Options Exercise: Potential for Suboptimal Time Delays and Value Destruction

ABSTRACTReal options (RO) valuation has been promoted as a way to evaluate investment opportunities and make investment decisions that takes into account the value of managerial flexibility in the face of uncertainty. Although RO enjoys a substantial body of literature considering its application and suitability in different situations, the impact of national culture on the application of RO has received little attention. Values embedded in national culture affect the behavior of managers. In particular, these values play a role in how managers frame information, communicate, and make decisions, directly and indirectly affecting behavior through cultural layers such as organizational culture. National culture, therefore, can systematically affect the application of RO, potentially leading to suboptimal outcomes. In this article, we hypothesize how 2 particularly relevant dimensions of culture, power distance and uncertainty avoidance, affect RO exercise, and estimate the magnitude suboptimality of these effects using a model we develop for the case of a put option. Our estimates suggest RO may not always be a superior valuation approach to net present value for national cultures with certain characteristics.

Electrochemical oxidation of reverse osmosis concentrate using a novel electrode: Parameter optimization and kinetics study

Pharmaceutical wastewater is difficult to be treated efficiently by the conventional biological wastewater treatment plant and reverse osmosis is a solution for this kind of wastewater pollution control. One limitation for RO application in pharmaceutical wastewater treatment is the treatment of RO concentrate. This work prepared a Co doped PbO2 anode and assessed the treatment of reverse osmosis concentrates with electrochemical oxidation process using this Co doped PbO2 anode. The operational parameters which have an influence on the electrochemical oxidation of quinoline, including the current density, the initial concentration of quinoline and the initial value of pH, were studied. The results revealed that the electrochemical degradation of quinoline followed the pseudo-first-order kinetics and the optimal removals of quinoline and COD were 100% and 59.35% after 120min. The EE/O was calculated among all the experiments which showed that the Co doped electrode would greatly reduce the EE/O value. The degradation mechanism and kinetics were analyzed and the intermediates including kinds of organic acids generated during the process of electrolysis were analyzed. This paper can provide a technique reference for the reverse osmosis concentrate pollution control.

RO applications in China: History, current status, and driving forces

RO membrane technology has been broadly applied in China in the past two decades and its applications increased quickly, as China is faced with a combination of rapid growth of heavy industries, large population, and water stress. The literature often underestimated the scale of RO applications in China as it was traditionally derived from surveys of RO membrane plants. Chinese RO market is highly monopolized, which provides an alternative to examine RO applications. This study collected manufacturing and sales data of RO membrane modules from limited RO membrane manufacturers, and analyzed the history and driving forces. For 2014, 1.8 million 8-inch RO membrane modules were used by membrane plants in China and the output capacity was about 27 million m3/d. RO plants are mainly applied for heavy industries, such as power, petrochemical, and coal industries. The power industry has highest number and output capacity of RO applications. RO plants are clustered in three regions, i.e. coastal provinces; northern China; and other provinces with advanced electronic, pharmaceutical and landfill leachate treatment industries. The RO applications in China were primarily driven by decreasing cost, rapid development of domestic membrane manufacturers, fast development of industries, and increasing water stress.

Turbocharged cost savings in RO systems

Turbochargers provide low life cycle costs energy recovery in seawater and brackish water RO systems. Recent improvements in hydraulic design and reliability have brought higher efficiencies. This article will focus on turbocharger ERDs in RO applications and provide a comparison between these two technologies.

An elementary approach to asymptotic behavior in the Ces\`{a}ro sense and applications to the Laplace and Stieltjes transforms

We present an elementary approach to asymptotic behavior of generalized functions in the Cesaro sense. Our approach is based on Yosida's subspace of Mikusinski operators. Applications to Laplace and Stieltjes transforms are given.

Fouling potential evaluation by cake fouling index: Theoretical development, measurements, and its implications for fouling mechanisms

Current fouling indices typically employed in RO practices, such as silt density index (SDI) and modified fouling index (MFI), have suffered greatly from their inability to predict actual fouling potential primarily due to the erroneous interpretation of fouling mechanisms. Our findings clearly demonstrated that the effect of pore blocking should be excluded during fouling index measurements to simulate real RO applications. Thus, new concept of cake fouling index (CFI) was developed in order to accurately evaluate true fouling cake layer resistance. Specifically, the CFI was determined through consecutive filtration tests by subtracting the flux decline of the secondary filtration from that of the first one to eliminate the effect of pore blocking. The results proved that CFI better predicts the degree of fouling rate in RO experiments than MFI. It was also revealed that it could be utilized as a useful tool for identifying and evaluating the fouling mechanisms. Through a comparison of MFI and CFI, it was shown that pore blocking was enhanced as much as cake formation when pH decreased, while divalent cations (Ca2+) increased only cake formation on the membrane surface. This newly developed index refining existing MFI method is expected to provide more precise information about RO membrane fouling, especially for the design of effective pretreatment processes.

Rosiglitazone ameliorates senescence-like phenotypes in a cellular photoaging model

BackgroundRosiglitazone (RO), a second-generation thiazolidinedione used mainly in the treatment of non-insulin-dependent diabetes mellitus, has been discovered to be a high-affinity ligand for peroxisome proliferator-activated receptor-γ (PPAR-γ). Several studies have revealed that PPAR-γ is also involved in the regulation of oxidative stress and chronic inflammation associated with aging process in vivo as well as with cellular senescence in vitro. We sought to investigate whether RO pretreatment will counteract the photoaging process using a well-established cellular photoaging model. MethodsMurine dermal fibroblasts (MDFs) were cultured in the absence or presence of RO for 48h, followed by exposure to repeated UVB irradiation. The senescent phenotypes were evaluated including cell viability, senescence-associated β-galactosidase (SA-β-gal) expression, cell morphology, ROS generation, cell cycle, production and degradation of extracellular matrix (ECM), and the potential mechanisms were discussed. ResultsPretreatment with RO (40μM) significantly decreased the staining intensity and the percentage of SA-β-gal-positive cells and reserved the elongated cell shape compared with UVB group. The cells pretreated with RO also showed decreased UVB-induced degradation of type I collagen by decreasing MMPs expressions. In addition, we observed counteraction of cell-cycle arrest and repression of UVB-induced p53 and p21 in the presence of RO. We further confirmed a significant decrease in ROS accumulation accompanied by an increase in catalase in RO group. ConclusionsRO, a potent PPAR-γ activator, counteracts senescence-like phenotypes, including long-term growth arrest, flattened morphology, degradation of ECM and SA-β-gal-positive staining in MDFs by inhibiting the expression of MMPs and increasing the synthesis of catalase when administered to repeated UVB irradiation. The novel application of RO may lead to innovative and effective anti-photoaging therapies.

Application of different activating solutions to in vitro fertilization of crucian carp, Carassius carassius (L.), eggs

Within the study, the in vitro fertilization (ivF) in crucian carp, Carassius carassius (L.), with the use of three activating solutions (AS) [reverse osmosis water (RO), Woynarovich (WS) and Billard (BS) solutions] as well as the period of the capacity of eggs to be fertilized (up to 180 s post-egg-activation) in those solutions. Moreover, CASA analysis of sperm motility was conducted with each AS. In control groups (0 s), the highest (P < 0.05) fertilization rate (93.2 %) was observed with WS. The application of RO and BS affected lower (P < 0.05) embryo survival (63.5 and <5 %, respectively). High fertilization rate (over 90 %) was recorded up to 30 (RO) and 90 s (WS) post-egg-activation. Progressive sperm motility (pMOT) was high (over 48 %) in all treatment groups up to 30 s. In RO and WS groups, pMOT significantly decreased (P < 0.05) after 45 s post activation. BS affected pMOT over 10 % up to the 165 s. No differences (P > 0.05) between the groups were found considering the curvilinear velocity (VCL) 15 s post-sperm-activation. Between 30 and 135 s, the lowest (P < 0.05) VCL after application of RO was noted. The highest VCL (P < 0.05) up to 135 s was noted after application of BS and WS. All AS activated crucian carp sperm. The lowest fertilization rate was noted when BS was used, despite the high pMOT and VCL. It suggest that the AS which activates the sperm properly may not activate the eggs probably due to high osmolality of BS (262 mOsm kg−1). Because eggs retained the longest period of activity in WS, this AS is suggested for ivF in crucian carp.

CHEMICAL CLEANING OF REVERSE OSMOSIS MEMBRANE FOULED BY APPLE JUICE

ABSTRACTThe effects of several chemical agents on cleaning of RO BW30 membrane fouled by apple juice were investigated. Resistance removal (RR) and flux recovery (FR) were calculated for all the seven chemical cleaning agents (HCl, HNO3, NH3, NaOH, ethylenediaminetetraacetic acid [EDTA], cetyl three methyl ammonium bromide and sodium dodecyl sulfate[SDS]) which were used at 1% (w/v) concentration. For high cleaning efficiency agents, the effect of chemical factors (pH and concentration) and physical factors (velocity, temperature and time) were studied. SDS showed the highest (about 90%) cleaning efficiency. EDTA and NH3 were also quite effective in reacting with organic foulants. The treatment of fouled membrane by distilled water as cleaning agent showed high cleaning efficiency. Investigations of the chemical and physical factors on membrane cleaning indicate that the cleaning efficiency is dependent on these parameters. Increasing the pH of 1.5% SDS solution up to 11.8 showed the highest cleaning efficiency, i.e., approximately 100%.PRACTICAL APPLICATIONSReverse osmosis (RO) is a very useful technology in fruit juice concentration due to maintaining the taste and fresh juice flavors. In contrast, the conventional processes applied for this concentration, e.g., evaporation, have the disadvantage of adding a cooking taste to the product and lowering itsquality, in addition to the high energy consumption. However, fouling by carbohydrate components is the most important problem associated with the RO application. Finding high efficiency cleaning agents for regeneration of membranes is one of the industrial interests, which is proceeded in this work.

The art of surface modification of synthetic polymeric membranes

AbstractThe development in the area of surface modification of polymeric synthetic membranes since 2000 is reviewed. Many patents, articles, and reviews have been written on the development in the area of surface modification of polymeric synthetic membranes subjected to RO, UF, NF, gas separation (GS), and biomedical applications, mainly since 2000, but recently more attention has been given to the modification of their surfaces to obtain desirable results. In particular, most emphasis has been given to plasma treatment, grafting of polymers on the surface, and modifying the surfaces by adding SMMs (surface‐modifying molecules). New additives are synthesized to make the polymeric membrane surfaces either to be more hydrophilic or hydrophobic, aimed at improvement in selectivity and permeability of the membranes for GS, NF, and RO. Improvement in antifouling by surface modification is also a popular topic in the membrane industries. In the last 8 years, tremendous research efforts have been made on the development of antifouling membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Selective activation of 5-HT 2C receptors stimulates GABA-ergic function in the rat substantia nigra pars reticulata: A combined in vivo electrophysiological and neurochemical study

In vivo electrophysiology and microdialysis were used to investigate the physiological role of 5-HT 2C receptors in the control of substantia nigra pars reticulata (SNr) function. Extracellular single-unit recordings were performed from putative GABA-containing neurons in the SNr of anesthetized rats, and local GABA release was studied by in vivo microdialysis in the SNr of awake freely-moving rats. Systemic administration of the selective 5-HT 2C receptor agonist ( S)-2-(chloro-5-fluoro-indol-1-yl)-1-methylethylamine 1:1 C 4H 4O 4 (RO 60-0175) caused a dose-dependent excitation of about 30% of the SNr neurons recorded. However, the remaining neurons were either inhibited or unaffected by systemic RO 60-0175, in similar proportion. Local application of RO 60-0175 by microiontophoresis caused excitation in the majority of SNr neurons tested (48%), whereas a group of neurons was inhibited (16%) or unaffected (36%). Both the excitatory and the inhibitory effects of systemic and microiontophoretic RO 60-0175 were completely prevented by pretreatment with SB 243213 [5-methyl-1-({2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl}carbamoyl)-6-trifluoromethylindoline], a selective and potent 5-HT 2C receptor antagonist. Consistent with these electrophysiological data, both systemic and intranigral administration of RO 60-0175 and m-chlorophenylpiperazine (mCPP), a non-selective 5-HT 2C agonist, markedly increased extracellular GABA levels in the SNr. The stimulatory effect of systemic and local RO 60-0175 on GABA release was completely prevented by systemic administration of SB 243213, whereas local application of SB 243213 into the SNr only partially blocked RO 60-0175-induced GABA release. It is concluded that selective activation of 5-HT 2C receptors stimulates GABA-ergic function in the SNr, and the clinical relevance of these data is discussed.

A pilot study for wastewater reclamation and reuse with MBR/RO and MF/RO systems

A pilot study was conducted to evaluate the quality of the effluent of an enhanced tertiary treatment process consisting of MBR/RO or MF/RO units and explore the feasibility of reclamation of treated effluent for potable and non-potable reuse applications. The performance of both the MBR/RO and MF/RO pilot plants was excellent. The MBR or MF alone was able to bring down the concentrations of most of the pollutants under acceptable limits for non-potable reuse applications. The application of RO further improved the treated water quality, especially the aesthetical and microbial qualities. Different strategies were employed to control membrane fouling in RO, and hypochlorite dosing showed the best results. The RO permeate quality in terms of conductivity, turbidity, organic content, ammonia, nitrate, hardness, E. coli and virus could meet the water quality requirements for many potable and non-potable reuse applications. In removal of total estrogens, the MBR/RO combination performed better than that of MF with RO, indicating the importance of the role of biomass. The rejection of virus in MBR and MF was greatly affected by the chemical membrane cleaning. It took more than 24 h for the recovery, implying that the presence of membrane biofilm plays a key role in rejection of virus.

Monitoring of Distribution Water Qualities Under Various Source Water Blending

The main goal of this large-scale pilot distribution study was to systematically investigate the impacts of blending different source waters on distribution water qualities. The principal source waters investigated were conventionally treated ground water (G1), surface water processed by enhanced treatment (S1), and desalted seawater by reverse osmosis membranes (RO). Due to the nature of raw water quality and associated treatment processes, G1 water had high alkalinity, while S1 and RO sources were characterized as high sulfate and high chloride waters, respectively. One year of pilot pipe study demonstrated that water quality was significantly deteriorated by increased color when source water blends with characteristics different from historic groundwater were introduced to pipe distribution systems. Elevated color was associated with release of iron corrosion products, mainly from aged unlined cast iron pipes. Iron release increased significantly when exposed to RO and S1 waters: that is, the greater iron release was experienced with alkalinity reduced below the background of G1 water. Lead and copper release to water, on the other hand, enhanced with the application of RO and G1 waters, respectively.

VIP receptors control excitability of suprachiasmatic nuclei neurones

The role of vasoactive intestinal polypeptide (VIP) receptors on excitable properties of neurones in slices acutely prepared from the suprachiasmatic nuclei (SCN) of wild-type (WT) and VPAC(2)-receptor-deficient (Vipr2 ( -/- )) mice was studied under voltage clamp with the use of patch-clamp recording in the whole-cell configuration. The resting membrane potential in Vipr2 ( -/- ) neurones was significantly hyperpolarised as compared to WT cells (-60+/-7 vs -72+/-6 mV, p<0.01). Bath application of 100 nM VIP or the VPAC(2) receptor agonist RO 25-1553 triggered a slow inward current in a subpopulation of WT SCN neurones; the VIP-induced current was not affected by slice incubation with 25 microM of bicuculline but disappeared completely when the cells were dialysed with CsCl-containing/K(+)-free solution. Application of VIP or RO 25-1553 to neurones from Vipr2 ( -/- ) mice did not induce currents in all cells tested. Incubation of WT slices with 100 nM VIP or RO 25-1553 resulted in inhibition of fast tetrodotoxin-sensitive sodium currents and delayed rectifier K(+) currents in most of the cells tested. This effect was completely absent in cells from Vipr2 ( -/- ) mice. We postulate that VIP receptors control excitability of SCN neurones at the postsynaptic level by direct modulation of membrane potential via inhibition of K(+) channels and by tonic inhibition of sodium and potassium voltage-gated currents.