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  • The Delicious Tales of Natural Filter Media

    Posted on June 27, 2013 by Sterlitech Corporation

    Sterlitech Corporation prides itself in manufacturing and marketing some of the most advanced filtration products around.  Our filters use materials like PTFEPVDF, and PES, and others with inconveniently long chemical names that also make their synthetic nature really obvious.  But they're not going to be the focus of this story.  Instead, we will be shining a spotlight on three natural materials that, in addition to being quite tasty, make excellent filters: papayas, oysters, and coconut.


    Originally native to Mexico and Central America, the papaya is now grown in tropical regions around the world.  The papaya is usually eaten raw when it's ripe and used in cooking when it's unripe.  The seeds are edible as well, although they're surprisingly spicy.

    The seeds of the papaya are also the reason why papaya make such good filters.  A recent study published by a group of German and Nigerian Scientists used a combination of crushed papaya seeds and kaolinite clay to create an inexpensive filtration media that excelled at adsorbing heavy metal ions out of water.  The combination of inexpensiveness and effectiveness make the hybrid clay-papaya filter a promising way to give millions of people access to clean water.

    The original study can be found here.


    Like papayas, oysters can be eaten raw or cooked.  Unlike papayas, the flavor of an individual oyster is strongly influenced by the quality of its surroundings.  This is because oysters are filter feeders, straining nutrients, algae, and particles from the water to sustain itself.

    A single oyster can pass 40 gallons of water through its filters and a bed of them can improve the quality and clarity of the water immediately surrounding them.  Oysters make such effective water treatment, West Palm Beach, Florida decided to use them as part of their "living dock," a waterfront development that doubles as a water filtration system.

    You can learn more about West Palm Beach's oyster filtration system here.


    Coconuts are a very versatile food; a coconut can be eaten raw, processed into oil, and its milk can be drunk straight or used in cooking.  But to get at the edible portion of the coconut you have peel off its husk and break into its tough shell.

    The shell is the part of the coconut that is made into filters.  The shells are burned to produce activated carbon, which is then built into filters for water.  Coconut-based activated carbon works better than traditional coal-based activated carbon because the coconut carbon is more porous, with more surface area available to adsorb impurities out of the water.

    An article detailing GE's use of coconut carbon filters can be found here.

    This post was posted in Did you know, water treatment, Biotechnology

  • Lockheed Martin Patents an Energy-saving Reverse Osmosis Membrane

    Posted on April 29, 2013 by Sterlitech Corporation

    The name Lockheed Martin invokes images of high tech aircraft, secret weapons, and other technologies that seem a whole lot more exciting than a reverse osmosis (RO) membrane.  However, Perforene™, Lockheed Martin’s latest innovation, promises to be an exciting new development for RO desalination. It’s made from graphene, an allotrope of carbon where the atoms arranged in hexagonal cells to make a sheet that is only one atom thick.  The next thinnest RO membrane is about 500 times thicker than Perforene™.  It is the almost impossible thinness of the membrane that makes it so exciting for RO; it takes about 100 times less energy to push water through the membrane when compared to the average RO membrane available commercially today.

    The Perforene™ membrane was developed by placing holes that are one nanometer or less in diameter into the membrane.  These holes are small enough to trap the ions while dramatically improving the flow-through of water molecules, reducing clogging and pressure on the membrane.  Although it is only one atom thick, graphene is both stronger and more durable than almost any other material could be at this scale.

    The combination of strength, high permeability, and excellent selectivity could make Perforene™ the key to cheaper desalination costs in plants across the globe.  And cheaper desalination can mean better access to fresh water in arid places such as North Africa, the Middle East or the Western United States. As the world’s population continues to grow, the demand for fresh water for drinking, agriculture, and industry will grow along with it. Perforene™ can make meeting those demands easier.

    Perforene was developed and tested with the help of Sterlitech’s CF042 crossflow cell, a lab scale cross flow filtration unit designed to provide fast and accurate performance data with minimal amounts of product, expense, and time.  It enables researchers to study membrane performance in the small scale before committing resources to larger process scale systems.  Sterlitech offers the CF042 in different materials to meet different needs, in addition to the larger Sepa CF crossflow cells and the smaller HP4750 stirred cell.  Recently, we also began offering the Sepa and CF042 in Forward Osmosis (FO) configurations to further enable research into new water technologies.  Further details can be obtained by contacting us.


    This post was posted in bench scale, water treatment, reverse osmosis, Customer Highlight

  • A Winter of Discontent at the Arizona Snowbowl

    Posted on March 6, 2013 by Sterlitech Corporation

    After nearly ten years of legal wrangling, the Arizona Snowbowl Ski Resort was given the green light to use reclaimed wastewater to make artificial snow for the first time this winter. It is also the first ski resort in the world to do so, taking its water from treatment facilities in nearby Flagstaff, AZ. It’s definitely a novel use for wastewater and, if it proves successful, it may help combat the stigma against the use of reclaimed wastewater in other applications where human contact may occur.

    Unfortunately, the first run of snow sprayed onto the slopes was yellow.

    Face-planting into a pile of yellow snow made from reclaimed wastewater is an icky proposition. Joking aside, the discolored snow raises serious questions about the potential health and environmental impact of spraying wastewater effluent onto the slopes. Some studies have shown that the effluent contains traces of pharmaceuticals, hormones and other chemicals which are not regulated by current water quality laws. The controversy is also complicated by the fact that the resort sits on a mountain that is considered sacred by 13 Native American tribes.

    The managers of the Arizona Snowbowl assert that their artificial snow does not pose a risk to skiers’ health. They claim that the discoloration snow was a result of rusty residue from the actual snow-making equipment. The snow guns have since been cleaned to prevent further discoloration of the snow.

    Ski resorts have been making artificial snow for decades. In the face of a changing climate and increasing demand for fresh water, using reclaimed wastewater to powder the slopes may just become a standard practice at resorts around the world. Let’s hope they keep it white.

    Contributing Sources:

    Chappell, Bill. "Ski Resort Makes Snow With Treated Wastewater, After A Long Dispute." NPR. NPR, n.d. Web. 28 Feb. 2013.

    MacMillan, Leslie. "Discolored Slopes Mar Debut of Snow-Making Effort." The New York Times. N.p., 11 Jan. 2013. Web. 28 Feb. 2013.

    Macmillan, Leslie. "Resort's Snow Won't Be Pure This Year; It'll Be Sewage." The New York Times. The New York Times, 27 Sept. 2012. Web. 28 Feb. 2013.


    This post was posted in Water Sterilization, waste and wastewater treatment, pollution, water treatment

  • Sterlitech Customer Highlight: Aquaporin

    Posted on July 31, 2012 by Sterlitech Corporation

    Aquaporin A/S of Denmark, one of Sterlitech Corporation’s customers, has recently tested their Aquaporin Inside™ technology at the NASA Ames facility at Palo Alto, CA. Aquaporin and their new technology take their names from a type of protein found in the cell membranes of every living thing on the planet: aquaporins. Aquaporin (the company) hopes to use the selectivity of aquaporins (the protein) to create cost-effective and ecologically sustainable new membrane filters to revolutionize water purification and desalination.

    Aquaporin Demonstrator Module

    Aquaporin Demonstrator Module

    The secret to the promise of Aquaporin Inside™ technology is the selectivity of the aquaporins themselves. Embedded throughout any cell membrane, aquaporins are a gateway through which water can pass into and out of a cell but ions and solutes cannot. Aquaporins will even exclude naturally occurring hydronium and hydroxide ions in water.  If successful, Aquaporin’s new technology could set new standards in water purity.

    As our planet’s population booms, the demand for safe, clean water will boom along with it. Aquaporin and their Aquaporin Inside™ technology has the potential to go a long way towards meeting that demand.

    Contributing Sources:

    “Membrane Product News.” Membrane Quarterly. January 2012: pg. 9
    Jensen, Peter Holme, and Danielle Keller. "Membrane for Filtering of Water." US Patent & Trademark Office. Web. 18 July 2012.
    "A Miracle that can Change the World." Aquaporin - Aquaporins. Web. 18 July 2012.

    This post was posted in Filtration, Did you know, Water Sterilization, Membrane Filtration, News, water treatment, Nanofiltration, Biotechnology, Forward Osmosis, Customer Highlight

  • The Future of Water

    Posted on March 19, 2012 by Sterlitech Corporation

    Click to enlarge

    Here’s a cool infographic on water challenges in the 21st century, courtesy of the Waterblog by Suez Environment and the World Water Forum. Fair warning: There are some alarming projections here about clean water shortages. That sort of thing might make you a little sad on this lovely Monday, so here’s a link to some adorable animal videos that you can clear your mind with afterward.

    Among the many interesting statistics (It takes 11,000 liters of water to make 1 pair of jeans!) is the note that 2% of fresh water is expected to be produced by desalination by 2015. It seems like every other day we’re hearing about a big new desalination facility opening up somewhere in the world, or an advancement that improves the desalination process.

    One such advancement whose popularity is growing is forward osmosis (FO) for desalination. In short, forward osmosis utilizes natural osmotic pressure to aid in water treatment, therefore requiring less energy and hydraulic pressure. Forward osmosis can also be used as pretreatment for a reverse osmosis system to create a continuous flow process with even greater efficiency. For more research on FO, Yale University’s Elimelech Lab is an excellent resource for forward osmosis desalination. You can also take a look at our new collection of forward osmosis cells and pumps for this application.

    Visit Waterblog here



    This post was posted in Uncategorized, water treatment, Forward Osmosis

  • Galvanic Wastewater Treatment with UF Membranes

    Posted on January 11, 2012 by Sterlitech Corporation

    A recently completed test in Poland found that enhancing ultrafiltration (UF) flat sheet membranes with an anionic polymer increased the membrane’s ability to purify samples of galvanized wastewater. For this experiment, the researchers tested multiple concentrations of wastewater infused with zinc, nickel, and copper ions against EW and MW designation flat sheet membranes that were infused with a polyelectrolyte, in this case polysodium 4-styrenesulfonate (PSSS) with cation-exchange properties. The result was a more-efficient metal binding agent, enabling 97-99% retention of the target metals.

    The EW membrane is made with Polysulfone while the MW is a modified Polyacrylonitrile known as Ultrafilic. Both designations ably treated the galvanized wastewater, but the MW membrane did have 2-3 times higher permeate flux values due to the membrane’s higher permeability.

    In addition to membrane separation, common treatment options for galvanized wastewater include chemical processing and the ion exchange method. Unlike these other methods however, an effective membrane separation methodology has the potential to remove higher concentrations of effluent in a continuous process so these findings could impact how galvanic wastewater is processed in the future.

    You can read the published paper here.

    This post was posted in water and wastewater treatment, water treatment, ultrafiltration

  • EPA to Create Standards for Natural Gas Wastewater

    Posted on October 24, 2011 by Sterlitech Corporation

    The Environmental Protection Agency announced last week that they are planning to develop standards for wastewater discharges produced by natural gas extraction from underground coalbed and shale formations (a process commonly referred to as “Fracking”). This method of extraction involves fracturing rock formations by injecting them with a pressurized fluid consisting mostly of water, a little bit of sand, and some chemical additives as well. The debate over the possible environmental consequences of fracking is a hot button issue right now, and since its popularity has grown to the point where it now accounts for about 15% of all natural gas production in the US, it is understandable that the EPA wants to look into setting some uniform regulations.

    Any potential EPA standards in this area can be broken down into two areas: shale gas standards and coalbed methane standards. In shale gas extraction, wastewater is prohibited from being discharged into waterways. Instead, it is either recycled back into use or sent to a treatment plant. Unfortunately, many of these treatment plants are not properly equipped to handle shale gas wastewater so the EPA will look into standards that could be implemented on wastewater before it reaches the treatment plant.

    Creating a coalbed methane standard for wastewater treatment is a little bit trickier, since there aren’t any national standards for it yet. Currently it is up to individual states to regulate where the wastewater is discharged and what pre-treatment standards to follow. The EPA is hoping to address the matter by creating a uniform standard for the whole nation.

    Based on the current EPA schedule, a proposed rule should come in 2013 for coalbed methane and 2014 for shale gas. This is to allow the EPA time to consult with stakeholders and allow for public comment.

    You can read the full announcement from the EPA here.

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

  • Water Treatment by Sunlight

    Posted on September 29, 2011 by Sterlitech Corporation

    Today’s Laboratory Equipment newsletter features an interesting article on how Purdue researchers have created a water-disinfection system that uses ultraviolet radiation from the sun to remove pathogens. With 800 million people unable to access clean drinking water, the potential for water-cleaning system that can be powered by natural resources is tremendous. According to and the United Nations Human Development Report, every 20 seconds a child dies from a water-related disease.

    This water treatment device uses a parabolic reflector to capture sunlight and focus it onto a UV-transparent pipe through which the water flows. In a brilliant development, the reflector is made out of a type of wood, paulownia, which is inexpensive and easy to find in regions around the equator where these systems are most needed. Since these people do not have significant funds or materials, for any solution to be effective it would have to be inexpensive and practical to construct.

    In tests the UV treatment system has shown that it can incapacitate E. coli bacteria, but it has yet to show that it can neutralize other pathogens like those that cause cholera, typhoid and diarrhea. The engineers are looking into different reflective materials, such as metalized plastic, that could improve the effectiveness of the UV treatment method. The Purdue team has also been experimenting with a sand and gravel filtration system, which could possibly be used in conjunction with the sunlight treatment as a means of providing cheap drinking water. We’ve discussed sand filtration before, and the basic operation of this kind of filter is similar to filtration by other materials. Water flows slowly through layers of sand and gravel, allowing a bacterial film to build up on the surface of the filter which removes contaminants.

    While industrial water treatment is obviously much faster and more effective on a larger scale, this filter made of natural materials could create enough drinking water for a family to live on. Aqua Clara International, a non-profit firm in Michigan, has been working with Purdue and Moi University in Kenya and so for they have installed almost 2,000 of these sand filtration systems in Kenya!

    Read the announcement from the Purdue Newsroom

    This post was posted in News, water treatment

  • Wastewater Mistreatment

    Posted on August 17, 2011 by Sterlitech Corporation

    Western Biodiesel Inc. was fined $160,000 (Canadian dollars) yesterday by the Provincial Court of Alberta for releasing wastewater that contained methanol into the environment and for providing false or misleading statements to investigators. The fine is the outcome of an incident in October 2008 in which Western Biodiesel dumped around 16,000 liters of methanol-laced water onto its property.

    Problems arose for Western Biodiesel the day after this release occurred when an unsuspecting welder accidentally ignited the wastewater with his torch, causing a fire that luckily yielded no injuries. In what had to be an incredibly gutsy and foolish move, the (now former) plant manager denied the release occurred when investigators showed up. He was later sentenced to four months house arrest.

    So besides dumping it in a river and hoping nobody lights a match, what are the actual proper methods of methanol disposal? Methods for extracting methanol from biodiesel include: Vacuum stripping, flash evaporation, distillation, and water washing. Methanol and especially glycerol are high-value byproducts of biodiesel production, so facilities try to reclaim as much as possible for resale. Membrane separation is also used as an effective biodiesel purification method, particularly for removing glycerol particles.

    Methanol is routinely used in biodiesel production during the transesterification reaction to turn plant or animal fats into fatty acids and glycerol. (Fun fact: Methanol is also a byproduct in liquor distillation and can cause blindness if ingested in large enough quantities!). European Standard 14214 specifies that biodiesel should contain no more than 0.2% methanol.

    For more information you can check out the official statement from the Government of Alberta and this publication on biodiesel production from the University of Idaho.

    This post was posted in waste and wastewater treatment, News, water treatment

  • Silt Density Index - The RO Gatekeeper

    Posted on July 20, 2011 by Sterlitech Corporation

    The Silt Density Index is most frequently used to determine fouling potential prior to RO filtration. You can think of SDI as a bouncer, keeping the riff-raff out of the RO feed water. The higher the number, the greater the likelihood of fouling. The maximum SDI number allowed depends on the type of RO membrane being used; most manufacturers recommend a maximum SDI of 4 or 5.

    SDI is found by calculating the rate at which a membrane filter is plugged. ASTM standard D4189-07 defines that the nominal filter for this application is a white hydrophilic MCE membrane filter, with 0.45 μm pore size and a 47 mm diameter. The reason this particular membrane is used is that it is more susceptible to plugging from colloidal material than from hard particles such as sand, therefore giving a better indication of the factors that might plug an RO membrane down the line.

    Other measures that can be derived from the SDI include the plugging factor and the Modified Fouling Index (MFI). The plugging factor expresses the level of suspended solids as a percentage of the measured SDI value to the maximum SDI value, so a 100% plugging factor would indicate that your membrane is completely plugged. The MFI incorporates cake filtration theory into its calculation of fouling potential. Since this formula is more complex than SDI, it is not as frequently used in the field.

    SDI can be determined manually or automatically with a measurement kit. Got any tips or experiences measuring SDI? Let us know in the comments!

    This post was posted in water treatment, reverse osmosis, RO

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