The energy released from the mixing of freshwater with saltwater is a source of renewable energy that can be harvested using pressure retarded osmosis (PRO). In PRO, water from a low salinity ...solution permeates through a membrane into a pressurized, high salinity solution; power is obtained by depressurizing the permeate through a hydroturbine. The combination of increased interest in renewable and sustainable sources of power production and recent progress in membrane science has led to a spike in PRO interest in the last decade. This interest culminated in the first prototype installation of PRO which opened in Norway in late 2009. Although many investigators would suggest there is still lack of theoretical and experimental investigations to ensure the success of scaled-up PRO, the Norway installation has evoked several specialized and main-stream press news articles. Whether the installation and the press it has received will also boost competitive commercialization of membranes and modules for PRO applications remains to be seen. This state-of-the-art review paper tells the unusual journey of PRO, from the pioneering days in the middle of the 20th century to the first experimental installation.
▶ A protocol for the selection of optimal draw solutions for forward osmosis (FO) applications was developed. ▶ Experimental data and model results showed that a small group of seven draw solutions ...appeared to be the most suitable. ▶ It was proven that internal concentration polarization is strongly dependent on the diffusion coefficient of the draw solution ▶ The large draw solution matrix, in terms of both constituents and concentrations, made it possible to quantitatively compare the effect of internal concentration polarization on water flux and reverse salt diffusion. ▶ The protocol developed can be used for draw solution selection as new FO membranes and draw solutions are developed and applied to new FO applications.
In this investigation, a protocol for the selection of optimal draw solutions for forward osmosis (FO) applications was developed and the protocol was used to determine the most appropriate draw solutions for specific FO applications using a currently available FO membrane. The protocol includes a desktop screening process and laboratory and modeling analyses. The desktop screening process resulted in 14 draw solutions suitable for FO applications. The 14 draw solutions were then tested in the laboratory to evaluate water flux and reverse salt diffusion through the FO membrane. Internal concentration polarization was found to lower both water flux and reverse salt diffusion by reducing the draw solution concentration at the interface between the support and dense layers of the membrane. Draw solution reconcentration was evaluated using reverse osmosis (RO) system design software. Analysis of experimental data and model results, combined with consideration of the costs associated with the FO and RO processes showed that a small group of seven draw solutions appeared to be the most suitable. The different characteristics of these draw solutions highlighted the importance of considering the specific FO application and membrane types being used prior to selecting the most appropriate draw solution.
Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent ...advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes and process components in the treatment of wastewater to potable water quality and to highlight recent advancements and needs in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials, and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.
A novel osmotic membrane bioreactor (OsMBR) is presented. The system utilizes a submerged forward osmosis (FO) membrane module inside a bioreactor. Through osmosis, water is transported from the ...mixed liquor across a semi-permeable membrane, and into a draw solution (DS) with a higher osmotic pressure. To produce potable water, the diluted DS is treated in a reverse osmosis (RO) unit; the by-product is a reconcentrated DS for reuse in the FO process. Preliminary results from experiments conducted with a flat-sheet cellulose triacetate FO membrane demonstrated high sustainable flux and relatively low reverse transport of solutes from the DS into the mixed liquor. Membrane fouling was controlled with osmotic backwashing. The FO membrane was found to reject 98% of organic carbon and 90% of ammonium-nitrogen; the OsMBR process (bioreactor and FO membrane) was found to remove greater than 99% of organic carbon and 98% of ammonium-nitrogen, respectively; suggesting a better compatibility of the OsMBR with downstream RO systems than conventional membrane bioreactors.
Wearable technologies represent the new frontier of vital sign monitoring in different applications, from fitness to health. With the progressive miniaturization of the electronic components, ...enabling the implementation of portable and hand‐held acquisition and recording devices, the research focus has shifted toward the development of effective and unobtrusive textile electrodes. These electrodes can represent an alternative to the Ag/AgCl disposable gelled electrodes usually adopted in clinical practice. This survey presents the main requirements for these electrodes, with a particular emphasis on those conceived for electrocardiographic signals, and the main challenges to be faced. An overview of the main materials and fabrication technologies presented so far in the scientific literature for this purpose is also given. The pieces of evidence resulting from the test of these electrodes clearly reveal the virtues and vices of current technologies, prospectively opening to their use in smart garments for real application scenarios.
The principal materials and fabrication technologies used to functionalize textile substrates to obtain electrocardiographic (ECG) electrodes that can represent an alternative to gelled Ag/AgCl electrodes are described herein. The main requirements and testing parameters for their assessment are discussed, revealing the virtues and vices of current technologies. Examples of smart clothes obtained embedding ECG textile electrodes in the garment are also illustrated.
Osmotically driven membrane processes (ODMPs) such as forward osmosis (FO) and pressure retarded osmosis (PRO) are extensively investigated for utilization in a broad range of applications. In ODMPs, ...the operating conditions and membrane properties play more critical roles in mass transport and process performance than in pressure-driven membrane processes. Search of the literature reveals that ODMP membranes, especially newly developed ones, are tested under different temperatures, draw solution compositions and concentrations, flow rates, and pressures. In order to compare different membranes, it is important to develop standard protocols for testing of membranes for ODMPs. In this article we present a standard methodology for testing of ODMP membranes based on experience gained and operating conditions used in FO and PRO studies in recent years. A round-robin testing of two commercial membranes in seven independent laboratories revealed that water flux and membrane permeability coefficients were similar when participants performed the experiments and calculations using the same protocols. The thin film composite polyamide membrane exhibited higher water and salt permeability than the asymmetric cellulose-based membrane, but results with the high permeability thin-film composite membrane were more scattered. While salt rejection results in RO mode were relatively similar, salt permeability coefficients for both membranes in FO mode were more varied. Results suggest that high permeability ODMP membranes should be tested at lower hydraulic pressure in RO mode and that RO testing be conducted with the same membrane sample used for testing in FO mode.
► In forward osmosis and PRO, membrane testing conditions and protocols are commonly inconsistent. ► It is difficult to compare the performance of old and new generation forward osmosis membranes. ► A standard method for characterizing forward osmosis membranes is proposed. ► Results from a round-robin test of the method by seven independent laboratories are presented. ► Testing results of two commercial membranes were consistent between laboratories when using the methodology.
The osmotic membrane bioreactor (OMBR) is a hybrid biological-physical treatment process that has been gaining interest for wastewater treatment and water reuse. The OMBR couples semi-permeable ...forward osmosis (FO) membranes for physiochemical separation with biological activated sludge process for organic matter and nutrient removal. The driving force for water production in OMBR is the osmotic pressure difference across the FO membrane between the activated sludge and a concentrated draw solution, which is made with inorganic or organic salts that have a high osmotic pressure at relatively low concentrations. The draw solution becomes diluted during OMBR treatment and may be reconcentrated using reverse osmosis, membrane distillation, or thermal distillation processes. The combination of processes in the OMBR presents unique opportunities but also challenges that must be addressed in order to achieve successful commercialization. These challenges include membrane fouling, elevated bioreactor salinity that hinders process performance, degradation of the draw solution by chemicals that diffuse through the FO membrane, and the potential for simultaneous water, mineral, and nutrient recovery. In this article, results from past and most recent OMBR studies are summarized and critically reviewed. Information about similar and more established technologies (
e.g.
, traditional porous membrane bioreactors and FO) is included to help compare and contrast state-of-the-art technologies and the novel OMBR approach, and to elucidate practical configurations that should be considered in future OMBR research and development.
The osmotic membrane bioreactor (OMBR) is a hybrid biological-physical treatment process for wastewater treatment and water reuse.
This research investigated the effectiveness of bipolar membrane electrodialysis coupled with fluidized bed crystallization and coagulation/flocculation with FeCl3 for removing potential membrane ...foulants from reverse osmosis (RO) concentrate solutions produced during reclamation of municipally treated wastewater. The goal of the treatment process was to produce water with low concentrations of potential foulants that could be subjected to a high recovery secondary RO process. Effluent from the secondary clarifier at a municipal wastewater treatment plant was treated by ultrafiltration and RO at a recovery of 60–65 %. The RO concentrate solution was then fed into a fluidized bed crystallization reactor operating at a pH value of 11.5. Calcium, magnesium, silica and dissolved organic matter were removed from the RO concentrate via precipitation of mineral solids on 60 mesh garnet sand. The acid and base utilized in the fluidized bed crystallization reactor was produced using bipolar membrane electrodialysis from the treated RO concentrate solution after polishing with coagulation/flocculation with FeCl3. The treatment system was able to remove 84 % of Ca2+, 93 % of Ba2+, >99 % of Mg2+, 80 % of total organic carbon (TOC), and 68 % of dissolved silica from the RO concentrate solutions. The product water produced by the system contained mostly Na+, Cl− and SO42- ions, with ≤ 10 mg/L Ca2+ and SiO2, ≤ 2 mg/L TOC, and ≤ 1 mg/L Mg2+. The electrical energy for operating the bipolar membrane electrodialysis cell amounted to 110 kW h per kmol of acid and base produced, which translates to 3.5 kW h/m3 of treated RO concentrate.
Osmotically driven membrane processes such as forward osmosis and pressure retarded osmosis may hold key advantages when integrated with seawater reverse osmosis to form hybrid FO-RO and RO-PRO ...systems. In this work, module-scale modeling of these two processes was improved by accurately representing the features of a spiral-wound membrane. The model captures important characteristics such as the cross-flow stream orientation, membrane baffling, and channel dimensions unique to spiral-wound membranes. The new module-scale model was then scaled to the system-level to compare various system designs for FO-RO and RO-PRO systems, most notably, a multi-stage recharge design was defined. Results indicate that the multi-stage recharge design leads to an increase in wastewater utilization, as high as 90%, when compared to the single-stage designs. Additionally, the multi-stage recharge configuration can increase the specific energy recovery of pressure retarded osmosis by over 75%. The multi-stage recharge design is found to be not only advantageous but may be also necessary to the integration of osmotically driven membrane processes with seawater reverse osmosis.
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•The module-scale model includes geometric and operational features unique to spiral-wound configuration.•The proposed model was scaled-up to evaluate FO and PRO at the system-scale.•Multi-stage designs featuring intermittent recharge of process streams were evaluated.•The multi-stage design increases the ability of FO to achieve high feed utilization.•The multi-stage design is necessary to maximize the specific energy recovery of PRO.
This paper summarises the results of an experimental campaign carried out at SIET on the ELSMOR facility built in 2022 to validate a decay heat removal system for the E-SMR. Based on the passive ...mechanisms of natural circulation, the system aims to dissipate the reactor decay heat to a water pool, using two heat exchangers: a plate-type one coupling the primary side to the secondary side, and a vertical tube one coupling the secondary side to the water pool. Such a system is considered to be the most effective passive system, capable of safely managing the SMR accident and accidental situations, and achieving long-term decay heat removal without the need for electricity or external inputs. A description of the primary and secondary loops of the plant is given, together with the installed instrumentation and data acquisition system. In addition, the paper summarises the tests performed in terms of test procedures, test type and associated objectives, test matrix, test results, achievements, and open issues.
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