Showing papers on "Reverse osmosis published in 2018"

Membrane distillation at the water-energy nexus: limits, opportunities, and challenges

Abstract: Energy-efficient desalination and water treatment technologies play a critical role in augmenting freshwater resources without placing an excessive strain on limited energy supplies. By desalinating high-salinity waters using low-grade or waste heat, membrane distillation (MD) has the potential to increase sustainable water production, a key facet of the water-energy nexus. However, despite advances in membrane technology and the development of novel process configurations, the viability of MD as an energy-efficient desalination process remains uncertain. In this review, we examine the key challenges facing MD and explore the opportunities for improving MD membranes and system design. We begin by exploring how the energy efficiency of MD is limited by the thermal separation of water and dissolved solutes. We then assess the performance of MD relative to other desalination processes, including reverse osmosis and multi-effect distillation, comparing various metrics including energy efficiency, energy quality, and susceptibility to fouling. By analyzing the impact of membrane properties on the energy efficiency of an MD desalination system, we demonstrate the importance of maximizing porosity and optimizing thickness to minimize energy consumption. We also show how ineffective heat recovery and temperature polarization can limit the energetic performance of MD and how novel process variants seek to reduce these inefficiencies. Fouling, scaling, and wetting can have a significant detrimental impact on MD performance. We outline how novel membrane designs with special surface wettability and process-based fouling control strategies may bolster membrane and process robustness. Finally, we explore applications where MD may be able to outperform established desalination technologies, increasing water production without consuming large amounts of electrical or high-grade thermal energy. We conclude by discussing the outlook for MD desalination, highlighting challenges and key areas for future research and development.

Potable Water Reuse through Advanced Membrane Technology.

Abstract: Recycling water from municipal wastewater offers a reliable and sustainable solution to cities and regions facing shortage of water supply. Places including California and Singapore have developed advanced water reuse programs as an integral part of their water management strategy. Membrane technology, particularly reverse osmosis, has been playing a key role in producing high quality recycled water. This feature paper highlights the current status and future perspectives of advanced membrane processes to meet potable water reuse. Recent advances in membrane materials and process configurations are presented and opportunities and challenges are identified in the context of water reuse.

Membrane technology in renewable-energy-driven desalination

Abstract: Growing requirements of freshwater and unsustainable nature of fossil fuels are driving the interest in using renewable energy for desalination applications. Due to their less energy-intensive nature and small footprint, membrane-based desalination operations are gaining significant interest in this regard. Substantial efforts have been observed in integrating traditional renewable and relatively green sources of energy (wind, solar, geothermal, tidal and nuclear) with membrane-based desalination operations, mainly reverse osmosis (RO) and electrodialysis (ED). Due to recent developments and progresses in membrane technology, interesting membrane operations including membrane distillation (MD), pressure retarded osmosis (PRO) and reverse electrodialysis (RED) have emerged. These operations are capable of generating clean and sustainable electricity from various waste streams including brine and impaired water which otherwise are considered environmental liabilities. PRO and RED require mixing of a high salinity solution (such as seawater or brine and wastewater, respectively) with a low salinity solution to generate electricity. MD has shown the potential to generate freshwater and electricity as standalone process. Integration of MD with PRO or RED enhances the performance of these processes and provides a clean and sustainable route to produce freshwater and energy. The current study reviews the recent progresses and developments in applying renewable energy sources in membrane-based desalination with special attention on emerging membrane operations with proven capability to generate energy from wastewater streams.

Nanofoaming of Polyamide Desalination Membranes To Tune Permeability and Selectivity

Abstract: Recent studies have documented the existence of discrete voids in the thin polyamide selective layer of composite reverse osmosis membranes. Here we present compelling evidence that these nanovoids are formed by nanosized gas bubbles generated during the interfacial polymerization process. Different strategies were used to enhance or eliminate these nanobubbles in the thin polyamide film layer to tune its morphology and separation properties. Nanobubbles can endow the membrane with a foamed structure within the polyamide rejection layer that is approximately 100 nm in thickness. Simple nanofoaming methods, such as bicarbonate addition and ultrasound application, can result in a remarkable improvement in both membrane water permeability and salt rejection, thus overcoming the long-standing permeability–selectivity trade-off of desalination membranes.

High-Pressure Reverse Osmosis for Energy-Efficient Hypersaline Brine Desalination: Current Status, Design Considerations, and Research Needs

Abstract: Water scarcity, expected to become more widespread in the coming years, demands renewed attention to freshwater protection and management. Critical to this effort are the minimization of freshwater withdrawals and elimination of wastewater discharge, both of which can be achieved via zero liquid discharge (ZLD), an aggressive wastewater management approach. Because of the high energetic cost of thermal desalination, ZLD is particularly challenging for high-salinity wastewaters. In this review, we discuss the potential of high-pressure reverse osmosis (HPRO) (i.e., reverse osmosis operated at a hydraulic pressure greater than ∼100 bar) to efficiently desalinate hypersaline brines. We first discuss the inherent energy efficiency of membrane processes compared to that of conventional thermal processes for brine desalination. We then highlight the opportunity of HPRO to reduce energy requirements for desalination of key high-salinity industrial wastewaters. The current state of membrane materials and processe...

Membrane filtration of wastewater from gas and oil production

Abstract: More than 88 billion barrels of wastewater are produced yearly in the world from gas and oil production. Given the rising demand for drinkable water, there is a need for advanced purification processes. Here we review membrane filtration processes used in the gas and oil production for wastewater treatment, with focus on microfiltration, nanofiltration, ultrafiltration, reverse osmosis, forward osmosis, membrane distillation, and electrodialysis.

A critical review on membrane separation processes applied to remove pharmaceutically active compounds from water and wastewater

Abstract: Pharmaceutically active compounds are a real threat all around the world. Conventional water and wastewater treatment are not efficient in removing this kind of organic micropollutants of emerging concern. Advanced treatment processes seem to be a good alternative for PhACs removal either in drinking water or wastewater. Membrane separation processes were proved to be a good treatment option since they are able to produce a high quality permeate without increasing its toxicity. Microfiltration, ultrafiltration and membrane bioreactor can be applied to the treatment of wastewater due to the high concentration of organic matter. Nanofiltration and reverse osmosis are mainly applied for water treatment. Their rejection mechanisms and the interactions between PhACs and NOM or inorganic salts are well understood. It is consensual that tighter NF membranes are more efficient than looser membranes, reaching >99% of removal. Membrane distillation is a relatively new technology especially because of its robustness in dealing with a broad spectrum of pollutants, however only a few studied are focused on the application of MD in removing PhACs from water and wastewater and few are known about the rejection mechanisms and the interaction between PhACs, NOM, inorganic salts and membrane. MSP, specially MD, is a very promising technology to be applied in order to prevent public health and environmental problems caused by the release of PhACs in the environment.

Assessing potential of nanofiltration and reverse osmosis for removal of toxic pharmaceuticals from water

Abstract: Concern about organic micropollutants, which are present in the environment at trace concentrations (ng L−1–μg L−1) is related to the adverse effects to organisms exposed to these substances. Pharmaceutically Active Compounds (PhCAs) may be present in natural waters and usually cannot be removed or degraded by conventional water treatment processes. For this reason, treatment techniques, such as Nanofiltration (NF) and Reverse Osmosis (RO) are recommended to improve their removal. In this context, the present study aims to evaluate the removal of five Non-steroidal anti-inflammatory drugs (NSAIDs), analgesics and anti-pyretic: acetaminophen, ibuprofen, dipyrone, diclofenac, and caffeine by NF and RO process. NF90 and BW30 membranes were characterized by scanning electron microscopic (SEM), contact angle and zeta potential. Retention of PhACs was evaluated considering pH feed solution and operating pressure. Results indicated that NF90 membrane was efficient to reach over 88% rejection for some selected PhACs. Best results were obtained at 20 bar and pH 5 with more than 90% of rejection. For nonionic compounds acetaminophen and caffeine, exclusion by size is the main mechanism for rejection by NF90 membrane, whereas for anionic compounds ibuprofen, dipyrone, and diclofenac, electrical exclusion predominated at pH 5 and 7. Rejection results with NF90 membrane show that hydrophobicity has an important role due to the adsorption on the membrane surface. Conversely, lower rejections for hydrophilic compounds were observed due to the adsorption/diffusion mechanisms, both in NF90 and RO at pH 5.

Unlocking High-Salinity Desalination with Cascading Osmotically Mediated Reverse Osmosis: Energy and Operating Pressure Analysis.

Abstract: Current practice of using thermally driven methods to treat hypersaline brines is highly energy-intensive and costly. While conventional reverse osmosis (RO) is the most efficient desalination technique, it is confined to purifying seawater and lower salinity sources. Hydraulic pressure restrictions and elevated energy demand render RO unsuitable for high-salinity streams. Here, we propose an innovative cascading osmotically mediated reverse osmosis (COMRO) technology to overcome the limitations of conventional RO. The innovation utilizes the novel design of bilateral countercurrent reverse osmosis stages to depress the hydraulic pressure needed by lessening the osmotic pressure difference across the membrane, and simultaneously achieve energy savings. Instead of the 137 bar required by conventional RO to desalinate 70 000 ppm TDS hypersaline feed, the highest operating pressure in COMRO is only 68.3 bar (−50%). Furthermore, up to ≈17% energy saving is attained by COMRO (3.16 kWh/m3, compared to 3.79 kWh/...

Electrochemical Desalination of Seawater and Hypersaline Brines with Coupled Electricity Storage

Abstract: We present a zinc|ferricyanide hybrid flow battery that achieves extensive first-pass desalination while simultaneously supplying electrical energy (10 Wh/L). We demonstrate 85% salt removal from simulated seawater (35 g/L NaCl) and 86% from hypersaline brine (100 g/L NaCl), together with reversible battery operation over 100 h with high round-trip efficiency (84.8%). The system has a high operating voltage (E0 = +1.25 V), low specific energy consumption (2.11 Wh/L for 85% salt removal), and a desalination flux (4.7 mol/m2·h) on par with that of reverse osmosis membranes. Salt removal was similarly effective at higher feed salinities, for which reverse osmosis becomes physically impossible because of the pressure required. The results have positive implications for regions that rely on desalination for their freshwater needs, especially where sea salinity is high. Alternatively, the battery may also be useful in minimal liquid discharge wastewater treatment if operated as a brine concentrator.