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brakish water

  • Dow BW30FR Membranes Discontinued

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    The BW30FR line of reverse osmosis membranes from Dow is being discontinued. At this time, these membranes do not have any direct replacements, although we still carry other Dow membranes which may be suitable for your application.  To aid comparison and help you select a possible replacement, the table below includes the technical specifications of the Dow membranes we offer:

    DOW FILMTEC™ Reverse Osmosis Membranes


    Series SW30HR SW30XLE BW30 BW30LE BW30FR XLE
    Feed Seawater Seawater Brackish Water Brackish Water Brackish Water Brackish Water
    Type High Rejection Extra-Low Energy Standard Low Energy Fouling Resistant Extra-Low Energy
    pH Range (25°C) 2-11 2-11 2-11 2-11 2-11 2-11
    Flux (gfd)/psi 17-24/800 23-29/800 26/255 37-46/225 26/255 33-41/125
    NaCl Rejection 99.6% 99.5% 99.5% 99.0% 99.5% 98.7%
    MWCO (Daltons) ~100 ~100 ~100 ~100 ~100 ~100
    Polymer Polyamide Polyamide Polyamide Polyamide Polyamide Polyamide

    If you need assistance finding a suitable replacement product, please contact us.  You can also click here to browse the other reverse osmosis membranes that Sterlitech carries.

    This post was posted in Flat sheet membrane, brakish water, reverse osmosis, Membrane/Process Development

  • Young Scientist Wins Big in California Science Fairs

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    We’d like to extend our congratulations to a young scientist, Alec Isaacman, who’s been making waves at California’s science fairs with his experiments with osmotic power.  Alec’s experiment, which was conducted in a fish tank his friend was no longer using, examined the effect salinity had on the production of osmotic power to determine the best locations in the world to place an osmotic power plant.

    The tank was divided into two chambers separated by a ACM5 RO membrane and were filled with equal amounts of water. One side was filled with fresh water and the other side was filled with salt water. Alec then determined the absorption rate of the salt water as it pulled fresh water through the membrane.

    The salt water was mixed to represent the three most common salinity levels found in the ocean: Polyhaline (18-29 parts per thousand), Mixoeuhaline (30-39 parts per thousand), and Metahaline (40-49 parts per thousand).   Alec predicted that the metahaline water would absorb the most fresh water, and would have the most potential to produce osmotic power.

    The fresh water side of the tank was pressurized to 50 PSI with a bicycle pump and, after 20 minutes, the water levels on both sides of the tank were measured to determine how much fresh water was drawn through the membrane.  The tank would then be emptied and cleaned for the next test.  Five tests were run for each salinity level.

    Alec's results ultimately proved his hypothesis.  He found, on average, the polyhaline water absorbed 32.1 cubic inches of fresh water, the mixoeuhaline water absorbed 34.4 cubic inches of fresh water and the metahaline water absorbed 37.4 cubic inches of fresh water during the 20 minute intervals.

    For determining that steeper salinity gradients have more potential energy, Alec won 1st prize at the Irvine District Science Fair, 2nd place at the Orange County Science Fair and was nominated for the Broadcom MASTERS program.  In addition, he won $200 dollars from the Irvine Ranch Water District.  Congratulations from Sterlitech, Alec!

    This post was posted in News, Flat sheet membrane, brakish water, renewable energy, Customer Highlight

  • Rising Salinity Cause for Concern at North Carolina Desalination Plant

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    An increase in salinity levels at the North Reverse Osmosis Water Plant in Kill Devil Hills (yes, that’s the town name) that had been creating stress for some local officials has been explained in a recent study. Researchers from nearby Duke University found that the rising salinity levels at this coastal aquifer are the result of fossil seawater and not seawater intrusion, as had been feared. Since the well’s installation in the late 1980’s salinity has more than doubled from about 1,000 mg/L to about 2,500 mg/L. There was much cause for relief however, when researchers were able to attribute the rise to fossilized seawater and not to seawater leaking in from the coast.

    According to the director of the study, Duke Professor Avner Vengosh, knowing the source of the salinity increase is important because fossil seawater raises salinity, “At a relatively slow and steady rate that is more manageable and sustainable than the rapid increase we’d see if there was modern-day seawater intrusion.” As a result of this study the community will be able to rely on this aquifer for decades to come without having to resort to more expensive seawater desalination techniques which require more energy and advanced filtration methods.

    Current treatment for groundwater desalination includes the use of reverse osmosis (RO) membranes to separate dissolved salts from potable water. Even with the rising salinity level these membranes remove around 96 to 99 percent of the dissolved salts. RO membranes also remove between 16 and 42 percent of the boron and 54 to 75 percent of the arsenic from the groundwater. Additional treatment following reverse osmosis desalination continues to remove arsenic until it is within safe drinking levels (10 parts per billion, according to the EPA).

    Because seawater consistently has more salt than groundwater it requires more energy to treat, and therefore the cost is higher. Per this report on desalination from the Pacific Institute, “Energy is the single largest variable cost for a desalination plant, varying from one-third to more than one-half the cost of produced water.” The report also states, “At these percentages, a 25% increase in energy cost would increase the cost of produced water by 11% (for RO plants).” In looking at these percentages, it’s easy to see why the plant was concerned about seawater intrusion. Thanks to this research, the local citizens can drink easier knowing they have a supply of healthy, affordable water for a long time to come.

    Click here to learn more about this case.

    This post was posted in waste and wastewater treatment, environmental lab, EPA, brakish water, water treatment, reverse osmosis

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