Tag: Membrane
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Boron nitride nanotube membranes outstrip carbon copies
One approach to improve the desalination process would be to design a more efficient membrane. Embedding nanotubes in the membrane is one area of research. Investigation of water transport through nanotubes in the past has primarily focused on carbon nanotubes, where the water has been found to flow extraordinarily fast in addition to rejecting salt…
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Low-Biofouling Polypropylene Feedspacers for Reverse Osmosis Applications
Polypropylene (PP) is a commercial polymer that is ubiquitous in membrane filtration as feedspacer due to its high chemical stability, low cost and versatile properties. The goal of this project was to develop low-biofouling polypropylene reverse-osmosis (RO) feed spacers, which can be used for desalination, through the functionalization of PP with copper ions since copper…
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Experience of ten years running the Okinawa desalination plant
At its inception, in February 1995, the Okinawa seawater reverse-osmosis (SWRO) desalination plant in southern Japan was the most advanced of its type. In March 1997, the plant’s full capacity of 40,000 m /d was completed and began full operation. Now, the desalination plant is an essential water-supply facility for Okinawa. For this reason, looking…
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Desalination using forward osmosis with nanofiltration membranes
Forward osmosis (FO) is an emerging membrane technology, often used for desalination. Like reverse osmosis (RO), FO uses a semi-permeable membrane to separate water from dissolved solutes. The semi-permeable membrane acts as a barrier that allows water to pass through while blocking salts. Generally, any dense, non-porous, selectively permeable material can be used as a…
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ADC baselines SWRO desalination system performance
The Affordable Desalination Collaboration (ADC) has completed a major milestone in its test program that profiles the state-of-the-art performance for seawater reverse-osmosis (SWRO) technology. This testing ran over two years and involved operating seven sets of standard 8-in diameter membranes in seven-element pressure-vessels. The ADC demonstration plant was designed to produce between 48,100 to 75,600…
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Advantages of Polyethersulfone (PESU) membranes for pretreatment for SWRO applications
Membrane pretreatment for large-scale seawater desalination has grown rapidly in the last few years. Existing examples seem to show that the additional cost can be more than recouped in reduced chemical costs alone, but there are also environmental advantages. This article is the first of two discussing the advantages of polyethersulfone (PESU) membranes for filtration…
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Leveraging nanotechnology for next generation seawater desalination
NanoH2O advanced membranes for reverse osmosis (RO) desalination represent a new material that enhances current polymer-based membranes with the benefits of nanotechnology. These nanocomposite RO membranes represent a step-change in productivity through improved permeability while maintaining requisite salt and contaminant rejection. Since the original publication of this concept, further development and optimization of this membrane…
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Bureau pilot tests show MBR reclamation potential
Membrane bioreactor (MBR) is a proven technology for wastewater reclamation that combines biological treatment with membrane filtration to achieve high quality effluent. Montgomery Watson Harza (MWH) and the city of San Diego have been conducting research on the MBR process since 1997 through various research projects. This article is derived from the report entitled Evaluation…
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The coming of membrane distillation technology
Membrane distillation (MD) is a unit operation that uses hydrophobic membranes as a barrier for contaminated water from which mass transport of vapor is driven by differences in vapor pressure. MD does not require a mechanical pressure pump, and temperature levels are such that low-grade heat sources may be used to supply the required energy…
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Antiscalant removes need for acid in wastewater RO
Field trials of a new scale-inhibiting chemical for use with reverse-osmosis membranes in wastewater reuse plants show that, at a low dose rate, it can increase the solubility of calcium phosphate by over one hundred times, obviating the need for using dangerous and costly acid. Current design practices for large effluent reuse projects are focused…