Ultra-low Pressure Reverse Osmosis Membranes Research Articles

Ultralow-pressure RO membrane element enhances neutral molecule rejection

Japan’s Toray Industries Inc continues to add products to its portfolio of reverse osmosis (RO) membrane elements. It has developed, and has recently started marketing, an ultralow-pressure RO membrane element that is designed for enhanced neutral molecule rejection. Here we look at the product and briefly explain how it is used in the electronics industry as an aid to manufacturing complex semiconductors.

Enhanced modelling and experimental validation of ultra-low pressure reverse osmosis membrane system for treatment of synthetic brackish water.

Water purification from brackish water sources has been acknowledged as one of the most promising ways to produce drinkable water in water-scarce areas. In this study, an ultra-low pressure reverse osmosis (ULPRO) membrane was numerically and experimentally investigated to produce drinking water by the removal of sodium chloride salt which provides further validation of the model from a practical perspective. An enhanced predictive model based on the Donnan-Steric Pore Model with dielectric exclusion (DSPM-DE) incorporating the osmotic effects was formulated in process simulation. The feed pressure and concentration were optimized as input variables and interaction between them was observed, while salt rejection and water recovery rate were taken as response attributes. The results obtained on the ULPRO membrane showed that the performance depends on the charge, steric, and dielectric effects. Furthermore, the enhanced model was validated with the experimental data attained from a laboratory-scale filtration system with good accuracy in the salt rejection and water recovery results. Comparing the enhanced DSPM-DE with the existing solution diffusion model reveals that the enhanced model predicts the membrane performance better and thereby qualifies itself as a reliable model for desalination of brackish water using ULPRO membrane.

A New Method for a Polyethersulfone-Based Dopamine-Graphene (xGnP-DA/PES) Nanocomposite Membrane in Low/Ultra-Low Pressure Reverse Osmosis (L/ULPRO) Desalination.

Herein we present a two-stage phase inversion method for the preparation of nanocomposite membranes for application in ultra-low-pressure reverse osmosis (ULPRO). The membranes containing DA-stabilized xGnP (xGnP-DA-) were then prepared via dry phase inversion at room temperature, varying the drying time, followed by quenching in water. The membranes were characterized for chemical changes utilizing attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated the presence of new chemical species and thus, the inclusion of xGnP-DA in the polyethersulfone (PES) membrane matrix. Atomic force microscopy (AFM) showed increasing surface roughness (Ra) with increased drying time. Scanning electron microscopy (SEM) revealed the cross-sectional morphology of the membranes. Water uptake, porosity and pore size were observed to decrease due to this new synthetic approach. Salt rejection using simulated seawater (containing Na, K, Ca, and Mg salts) was found to be up to stable at <99.99% between 1–8 bars operating pressure. After ten fouling and cleaning cycles, flux recoveries of <99.5% were recorded, while the salt rejection was <99.95%. As such, ULPRO membranes can be successfully prepared through altered phase inversion and used for successful desalination of seawater.

4-Dimethylaminopyridine Promoted Interfacial Polymerization between Hyperbranched Polyesteramide and Trimesoyl Chloride for Preparing Ultralow-Pressure Reverse Osmosis Composite Membrane

We have presented a concept of ultralow-pressure reverse osmosis membrane based on hyperbranched polyesteramide through interfacial reaction promoted by pyridine derivate. In this strategy, a key catalyst of 4-dimethylaminopyridine, which can both eliminate the steric hindrance of acyl transfer reaction and facilitate the phase transfer in interfacial polymerization, is adopted to drive the formation of a thin film composite membrane from the hyperbranched polyesteramide and trimesoyl chloride. The results of the characterization demonstrate that a dense, rough, and hydrophilic active layer with a thickness of about 100 nm is formed when the 4-dimethylaminopyridine catalyst is used. The salt rejections for Na2SO4, NaCl, and MgSO4 of the as-prepared composite membrane are higher than 92%, especially for Na2SO4 with 98% rejection. The water fluxes reach about 30-40 L·m(-2)·h(-1) even at an operation pressure of 0.6 MPa. The membrane exhibits good chlorine-resistance ability but poor resistance abilities to acidic and alkaline solutions in the physical-chemical stability experiment. It is also found that the resultant membrane possesses excellent separation performance for PEG-200, showing a promising way to separate small organic molecules from water.

Modeling the impacts of feed spacer geometry on reverse osmosis and nanofiltration processes

Maximizing mass transfer and minimizing hydraulic losses in spiral wound elements is critical for designing effective and efficient reverse osmosis (RO) and nanofiltration (NF) processes. Herein we describe a multi-scale modeling approach, which links microscopic and macroscopic transport phenomena in spiral wound elements. Model simulations elucidate the impacts of feed spacer geometry on full-scale RO/NF system performance considering four representative water treatment scenarios: (1) RO membranes used to desalt ocean water, (2) low-pressure RO membranes used to desalt brackish water, (3) ultra-low pressure RO membranes used to purify wastewater, and (4) NF membranes used to soften a hard, fresh water. According to model simulations, feed spacer geometry had little impact on mass transfer; hence, engineering spacers to improve concentration polarization, trans-membrane osmotic pressure, or product water quality may prove difficult and yield limited benefits. In contrast, thinner filaments spread further apart significantly reduced hydraulic losses with negligible impacts to mass transfer. In addition, a few non-circular filament shapes produced even lower hydraulic losses, which might prove beneficial for RO/NF treatment of low salinity waters where hydraulic losses through spiral wound elements contribute significantly to the total process energy consumption. In high salinity waters, improved spacer designs may not significantly reduce energy consumption because hydraulic losses through spiral wound elements are relatively small.

Comparing nanofiltration and reverse osmosis for drinking water augmentation

This study investigated the use of ultra‐low‐pressure reverse osmosis (ULPRO) and nanofiltration (NF) membranes for water reuse applications where lower operating pressures and a high permeate quality are desired. A laboratory‐scale investigation was performed to compare the rejection and operational performance of RO, ULPRO, and NF membranes and to select two membranes for testing at a California water facility. A ULPRO membrane and an NF membrane were then tested at pilot and full scale at a water recycling plant and monitored for operational performance and rejection of total organic carbon, total nitrogen, and regulated and unregulated organic micropollutants. Pilot‐ and full‐scale testing of the best‐performing membranes demonstrated that both ULPRO and NF membranes could be used to meet potable water quality requirements. The presumed advantage of using ULPRO and NF membranes diminished as fouling occurred, resulting in operating pressures only slightly lower than or similar to those found for traditional RO membranes.

Beneficial use of co-produced water through membrane treatment: technical-economic assessment

Large amounts of co-produced water are generated during natural gas production. This study investigated the viability and cost effectiveness of ultra-low pressure reverse osmosis (ULPRO) and nanofiltration (NF) membranes as potential techniques for beneficial use of produced water by meeting potable and irrigation water quality standards and concentrating iodide in the brine. A 2-stage laboratory-scale membrane testing unit was employed to examine rejection of various constituents of concern at a low and high recovery using produced water generated from sandstone aquifers. The performance of two ULPRO membranes TFC-ULP (Koch) and TMG10 (Toray America) and one NF membrane NF-90 (Dow/Filmtec) was compared to a conventional RO membrane (TFC-HR, Koch). These membranes were pre-selected during previous bench-scale experiments with regard to specific flux, fouling propensity, salts and organics rejection, and iodide recovery efficiency. Of the membranes tested, the NF-90 achieved the highest specific flux. The salt rejection and iodide recovery by the NF-90, however, were much lower than the RO and ULPRO membranes tested. The permeate quality of the NF-90 met USEPA National Primary Drinking Water Standards, but exceeded the Secondary Standards regarding chloride and total dissolved salts. The two ULPRO membranes TMG10 and TFC-ULP, exhibited a higher specific flux as compared to the TFC-HR while displaying a similar rejection, notably the TMG10 which showed a very stable rejection at low and high recoveries. Cost analysis showed that the ULPRO membrane system provided marginally lower overall O&M costs than RO for meeting drinking water standards. The ULPRO membrane operation resulted in even lower treatment cost than RO and NF for meeting irrigation water standards, especially at high energy cost. Findings from these studies indicated that ULPRO membranes can provide a viable and cost-effective solution to beneficial use of produced water from sandstone aquifers.

Viability of nanofiltration and ultra-low pressure reverse osmosis membranes for multi-beneficial use of methane produced water

Produced water management has become one of the key factors to sustainable development of natural gas/oil resources. The substantial quantities of saline water present intractable environmental threats and also increase oil/gas production costs through produced water disposal such as deep well reinjection. Developing high-efficient and flexible treatment systems that can be operated at low costs is of high interests for producers and state regulators. Beneficial use of produced water could represent a new water resource especially for areas with inadequate existing supplies. Furthermore, some produced waters generated are also characterized by elevated concentrations of recoverable constituents, for example iodide. Recovering iodide from brine could offer additional benefits besides providing methane gas, reusing produced water, or reducing brine disposal volume. The advent of ultra-low pressure reverse osmosis (ULPRO) membranes and nanofiltration (NF) membranes with high desalting degree might offer a viable option for produced water treatment because these membranes can be as effective as reverse osmosis (RO) in removing certain solutes from water while requiring considerably less feed pressure resulting in lower operating costs. The objectives of this research were to investigate the viability of ULPRO and NF membranes as potential techniques to treat produced water by meeting water quality standards and concentrating iodide in the brine. The produced water extracted from sandstone aquifer in Eastern Montana was characterized as brackish groundwater of sodium chloride type with total dissolved solids (TDS) concentration of 5300 mg/L, absence of hydrocarbons, and average iodide concentrations of 55 mg/L. The produced water exhibited a very high potential to membrane fouling indicated by silt density index (SDI) measurements due to the presence of small particles and inorganic constituents. The studied candidate membranes included one RO membrane (TFC-HR, Koch Membrane Systems), three ULPRO membranes XLE (Dow/Filmtec), TFC-ULP (Koch) and TMG-10 (Toray America), and three NF membranes NF-90 (Dow/Filmtec), TFC-S (Koch), and ESNA (Hydranautics). Bench-scale cross-flow flat sheet test units were employed to assess the candidate membranes using the produced water with focus on fouling potential, iodide recovery, and general salt rejection. The degree of flux decline was found to be dependent upon the combination of permeate drag force and physico-chemical properties of the membranes. The membranes with higher permeability generally displayed faster initial flux decline. In addition, hydrophobic and rough membranes exhibited a higher flux decline and lower chemical cleaning efficiency than smooth and/or hydrophilic membranes. Flux decline experiments, in situ microscopic techniques, analysis of elemental composition and functional groups revealed that the pretreatment including microfiltration, pH adjustment and addition of antiscalants could alleviate membrane fouling significantly. Chemical cleaning using caustic and anionic surfactant solutions restored membrane permeability more efficiently than hydraulic cleaning or using acids and metal chelating agents. This study showed that TFC-ULP, TMG-10, and NF-90 membranes exhibited competitive efficiency regarding salt rejection, iodide recovery and adjusted specific flux as compared to a conventional RO membrane.

Effect of membrane fouling on transport of organic contaminants in NF/RO membrane applications

Commercial polyamide nanofiltration (NF), reverse osmosis (RO), and ultra-low pressure RO (ULPRO) membranes (NF-90, NF-200, TFC-HR, and XLE) as well as a cellulose triacetate RO membrane (CTA) were employed to investigate the effect of fouling on transport of organic micropollutants. Due to foulant precipitation and cake-layer formation, membrane surface characteristics changed considerably in terms of contact angle (an index of hydrophobicity), zeta-potential, functionality, and surface morphology, which potentially affected transport of contaminants as compared to unfouled (virgin) membranes. The transport of ionic organic micropollutants was hindered as a result of improved Donnan exclusion (electrostatic repulsion) likely due to a more negative surface charge as quantified by zeta-potential measurements. Membrane fouling also resulted in an increased adsorption capacity and reduced mass transport through partitioning and diffusion of solutes across the membrane. These effects led to an increase in rejection of hydrophobic non-ionic solutes (e.g., disinfection byproducts and chlorinated solvents) by fouled membranes. However, the increasing surface charge has the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling, which can lead to lower rejection for hydrophilic non-ionic solutes, especially where nanofiltration membranes with a larger molecular weight cut-off are employed. Membrane fouling facilitated the transport of hydrophobic and hydrophilic organic contaminants through CTA membranes resulting in elevated concentrations of target solutes in the permeate. Findings of the study indicate that membrane fouling significantly affects the rejection of organic solute by CTA, NF, and ULPRO membranes while it is less important for thin film composite RO membranes.

CAN NANOFILTRATION AND ULTRA-LOW PRESSURE REVERSE OSMOSIS MEMBRANES REPLACE RO FOR THE REMOVAL OF ORGANIC MICROPOLLUTANTS, NUTRIENTS AND BULK ORGANIC CARBON? – A PILOT-SCALE INVESTIGATION

The scope of this project was to determine if low pressure membranes such as nanofiltration (NF) and ultra-low pressure reverse osmosis (ULPRO) membranes can meet water quality requirements necessary for indirect potable reuse while meeting acceptable operational parameters such as feed pressure, permeate flux, and flux decline. A total of 12 NF and ULPRO membranes were screened in this study and one ULPRO and one NF membrane were selected for a pilot-scale assessment (19 gpm) at a water reuse facility. Results of this study suggest that ULPRO and NF membranes can achieve similar removal efficiencies for the selected trace organics, nitrogen and bulk parameters tested as commonly employed RO membranes. While providing a similar water quality, these membranes can be operated at significantly lower feed pressures. These results suggest that ULPRO and NF membranes are viable for water reuse projects where a high permeate quality is required.

REJECTION OF EMERGING ORGANIC MICROPOLLUTANTS IN NANOFILTRATION/REVERSE OSMOSIS MEMBRANE APPLICATIONS

REJECTION OF EMERGING ORGANIC MICROPOLLUTANTS IN NANOFILTRATION/REVERSE OSMOSIS MEMBRANE APPLICATIONSThis study aimed to investigate factors affecting the rejection of emerging trace organics by a variety of commercial reverse osmosis (RO), nanofiltration (NF), and ultra-low pressure RO membranes during laboratory-scale experiments. Findings of this study indicated that rejection of negatively charged organics was driven by a combination of steric and electrostatic exclusion, which was...Author(s)Jörg E. DrewesPei XuChristopher BellonaGary AmyTae-Uk KimMark AdamThomas HebererSourceProceedings of the Water Environment FederationSubjectSession 1: AEESP Lecture and Fate, Transport and Treatment of Emerging Micro-PollutantsDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2004ISSN1938-6478SICI1938-6478(20040101)2004:16L.77;1-DOI10.2175/193864704784147548Volume / Issue2004 / 16Content sourceWEFTECFirst / last page(s)77 - 96Copyright2004Word count160

Performance of an ultra-low-pressure reverse osmosis membrane (ULPROM) for separating heavy metal: effects of interference parameters

An experimental investigation was conducted to study the performance of an aromatic polyamide (ES 20) ultra-low-pressure reverse osmosis membrane (ULPROM) for separating divalent (Cu 2+, Ni 2+) and hexavalent (Cr 6+) heavy metals from bulk solution. The influence of operating pressure, feed concentration, pH, and effect of other ions (Ca 2+ and Mg 2+) on the ULPROM performance was studied. The investigation was conducted for synthetic wastewater and wastewater from the heavy metal industry. Experimental results show that the rejection increases with increasing feed pressure, it is dependent on feed pH and is higher at higher pH. Increasing concentration of other ions slightly decreased the rejection of heavy metals. Generally, rejection of heavy metal is found to be greater than 95% for the ULPROM tested, which suggests the suitability of such membranes for industrial application for recovery of heavy metal and reclaiming wastewater.

Rejection of organic compounds by ultra-low pressure reverse osmosis membrane

The introduction of ultra-low pressure reverse osmosis (ULPRO) membrane has widened the horizon of reverse osmosis (RO) in purification of surface water and wastewater as well as desalination of brackish water. The ULPRO membrane chemistry can provide a high water flux at low operating pressure, while maintaining a very good salt and organics rejection. This paper deals with the investigation on the rejection of low molecular weight organic compounds by ULPRO membrane. Laboratory scale experiments were carried out at a pressure of 3 kg/cm 2 with a feed flow rate of 1.20 l/min. The rejection of undissociated organic compounds did not show a close relationship with the feed pH. The percentage removal of undissociated organic compounds increased linearly with the molecular weight as well as with the molecular width. The removal efficiency can be predicted by these relationships. But neither molecular weight nor molecular width can be considered as an absolute factor for rejection. The feed pH also influenced the removal efficiency of dissociated organic compounds. The efficiency decreased linearly with the increase in the dissociation constant.

Application of ultra low pressure reverse osmosis (ULPRO) membrane to water and wastewater

There is a worldwide grave concern about water pollution control. To mitigate the water scarcity, in arid zones and in the areas with no other sources but brackish water, reverse osmosis technology has played an important role. In an effort to reduce the cost of energy requirement for RO operation, nanofiltration has been developed. Until recently the nanofiltration has been used in water softening and removal of disinfection byproduct (DBO). Use of nanofiltration to desalinate brackish water has been ruled out due to low rejection of salts. The introduction of ultra-low pressure reverse osmosis membrane, categorically a nanofiltration, has widened the horizon of using the nanofiltration in desalinating brackish water as well as surfacewater and wastewater. This development ensures the increase in flux due to improvement in active surface layer formation with the application of very small pressure. The surface charge and hydrophilicity on the surface material of the membrane have shown better flux stability in the high fouling conditions. With the addition of higher flux and higher rejection based on the same chemistry, ULPRO has made another step forward. This introduction will certainly reduce the operation cost and, more importantly, improve the overall reliability of the RO system. Application of nanofiltration is broadened to surface water treatment, wastewaters for nutrient removal and heavy metal rejection from wastewater.

Innovative system designs to optimize performance of ultra-low pressure reverse osmosis membranes

The reverse osmosis (RO) water treatment industry has been revolutionized in the past several years by the introduction of a new generation of ultra-low pressure RO membrane elements. These new membranes have helped the technology become much more affordable and cost effective by reducing the energy consumption required to operate the RO system. The energy required to pressurize the RO feedwater has always been the largest component of the operating cost of a RO plant. The operating and capital cost savings provided by the new membranes combine to bring the expense for RO water treatment plants in line with the costs for conventional water treatment plants. Although several technical papers have been written over the past few years evaluating the performance of the specific ultra-low pressure membranes, very little information has been shared throughout the industry on observations of the operation of these membrane in conventional RO system design. Although the ultra-low pressure membranes have salinity rejection characteristics comparable to conventional RO membranes, their hydraulic characteristics can be significantly different. Information indicates that the ultra-low pressure membranes have an almost 30% higher design permeate productivity than conventional membranes. This significantly affects the hydraulic behavior of the full-scale membrane water treatment system. Additionally, in multi-stage systems, the lower required feed pressure translates into even lower second pass feed pressure (and third pass, if used). These two factors combine to cause potential hydraulic balance problems in conventionally designed membrane water treatment systems. Modifications to conventional membrane system design practices must be considered to optimize the use of ultra-low pressure membranes. This paper will focus on the behavior of the ultra-low pressure RO membranes in the full-scale system. Several design options will be evaluated for their effectiveness in improving system designs incorporating ultra-low pressure membranes. The design modifications will be evaluated for function, effectiveness and cost impacts. Finally, recommendations will be presented on how to assess which design might be the most applicable for a particular application.

Removal of pesticides and other micropollutants with cellulose-acetate, polyamide and ultra-low pressure reverse osmosis membranes

In 1995 several membrane manufacturers started to sell ultra low-pressure reverse osmosis membranes. The specifications of these membranes indicated that they have rejections for dissolved salts comparable to “conventional” composite (polyamide) membranes, while the required feed pressure to realize a specific production capacity is 30–40% less. This article describes the results of a preliminary study on the performance of these new membranes. The results showed that the rejections and productivity as specified by the manufacturers could be reproduced. Also the results of the spiking experiments with organic micropollutants showed that the ultra low pressure membranes have excellent properties to remove these compounds from water. NV PWN Water Supply Company of North Holland selected these membranes for their new water treatment plant Heemskerk when previously it was determined that cellulose acetate membranes were not suitable for the removal of organic micropollutants.

Ultra-low pressure RO membranes: an analysis of performance and cost

A new generation of reverse osmosis (RO) membrane has recently been introduced, which is receiving a great deal of interest. This is especially true among application of RO for large-scale municipal desalination systems. This new group of RO membranes operates at very low applied pressure, often in the range of 7–10 bar (100–150 psi). This paper presents information and data on the characteristics and performance of these membranes relative to the traditional brackish RO membranes. Performance and cost comparisons are provided. Also, an existing large-scale facility is reviewed.

膜による食品技術のイノベーション 最先端の超低圧ＲＯ膜とモジュールの現状

It goes back for 25 years in 1972, low pressure reverse osmosis (RO) membrane was developed in USA. Since that time, this low pressure RO membrane has been made rapid progress in producing of semiconductor-grade water in Japan. On the other hand, in USA and Europe, the low pressure RO membrane has been greatly developed for desalination of brackish water and refinement or condensation in food processing.Later we will explain the latest information of the low pressure composite RO membranes, especially in respect of the forefront of the ultra low pressure RO membrane which was developed for saving the energy and in respect of the module for food processing or vessel structure.