Sterlitech Blog

Your source for new information on filtration equipment applications and processes.

  1. Gasket Placement Dos and Don’ts

    Gasket Placement Dos and Don’ts

    If the goal of your vacuum filtration is purification using a membrane with an absolute pore size, Sterlitech recommends utilizing glass filter holder assemblies. Compared to Buchner funnels, these systems create a tight seal to prevent liquid bypass around the membrane. Without this seal, the benefit of a highly retentive membrane disappears.

    It is typical to experience some leaking in many vacuum filtration applications, but minimizing this will significantly improve yield. There are a few ways to ensure optimal sealing, including proper set-up of the apparatus and running under the manufacturer’s recommended conditions.

    To illustrate this, we ran trial liquid filtration on our 150 mm assembly with improper gasket placement (below support) and compared it to filtration with proper gasket placement (on top of support). Membrane filters should be placed on top of the gasket to achieve vacuum seal. Please view the video below to see the difference gasket placement can make in vacuum assembly performance. 

    Please feel free to reach out with any questions or concerns on best practices for vacuum filtration. 

  2. eDNA Studies Enabled by Disposable Funnels

    eDNA Studies Enabled by Disposable Funnels

    In a recent article, we described how environmental DNA (eDNA) has been used to detect the presence of aquatic species in lakes and rivers.  eDNA studies have demonstrated great potential for surveillance of rare, endangered, and invasive species by simply collecting and analyzing water samples from target habitats.  Dr. Caren Goldberg, of Washington State University, is one researcher using a unique combination of Sterlitech filters in her investigations of Yangtze giant softshell turtles in southeast Asia, tiger salamanders in California and Arizona, and fairy shrimp in southern California.

    Many of our eDNA end-user researchers utilize disposable filter funnels for this application. These are convenient, presterilized single-use vacuum holders that contain 0.45µm rated mixed cellulose esters (MCE) membrane filters. This membrane material is great for retaining very small particles potentially holding eDNA; however, the small pore size posed a problem for Dr. Goldberg, as her lake and wetland samples often had sediment that would cause the filters to clog prematurely.  Fortunately, these disposable funnels are designed with a removable filter.  Normally the filters are removed after use for subsequent analysis, but this design feature also allows users to replace the filter before use to optimize the funnels for their applications.  For example, Dr. Goldberg and her colleagues determined that 5.0µm rated Polyethersulfone (PES) membrane filters worked well for their water samples, allowing them to process larger volumes while still retaining target particles.

    A fascinating aspect of eDNA studies is the wide diversity of the filters being used, as shown by Dr. Goldberg and others.  Instead of the filters converging into one or two standard types, the filters being used are almost as diverse as the studies themselves; researchers have the freedom to select filters that are optimal for their studies.

  3. Total Drain Simplified by Hold-up Volume Recovery Kit

    Total Drain Simplified by Hold-up Volume Recovery Kit

    Sterlitech’s Hold-up Volume Recovery Kit is designed to enable users to recover residual solution from a cross flow filtration system or a skid mounted system to achieve a total drain. Available in both 110V and 220V, this is essential for applications involving high value or hazardous/corrosive feed solutions when complete recovery of the feed is desired. Each kit includes:

    • Vacuum pump

    • 2 Liter polypropylene collection container

    • Low pressure Tygon tubing

    • Stainless Steel Hose Connector

    Kits will be attached to a filtration system or a skid through a 3/8” NPT fitting to recover any residual solution.

  4. Sterlitech achieves ISO 9001:2015 certification

    Sterlitech achieves ISO 9001:2015 certification

    We are pleased to announce our ISO 9001:2015 quality certification for the design, development, and manufacture of filtration products. This award by Perry Johnson Registrars indicates that the quality management system at Sterlitech is designed to increase productivity, streamline processes, and ensure product quality.

    ISO 9001:2015 registration certifies a process-oriented approach to quality management. Both customers and business partners can recognize this certification as a symbol of commitment to developing and maintaining quality policies. ISO is the world’s largest developer and publisher of international standards, and ISO 9001:2015 defines the requirements for Quality Management Systems. The management standards of the ISO 9001:2015 certification are observed by more than one million companies in more than 170 countries worldwide.

    Sterlitech would like to recognize the effort of our entire team to make this accomplishment possible. Our registration with ISO 9001:2015 is a milestone in our continuing goal to keep our customers at the forefront of their research.

  5. Tech tips: Membrane Preconditioning

    Tech tips: Membrane Preconditioning

    What is membrane preconditioning and why is it recommended to precondition new flat sheet or spiral wound membranes prior to use?

    Membrane preconditioning is a filtration step using deionized water as feed solution and is typically performed at a pressure equal to or higher than the anticipated testing pressure. During this process membrane pores are wetted and the membrane structure may go through compaction or swelling, affecting both the permeate flux and the rejection values. Preconditioning will help ensure that the membrane performs according to the specs provided by the manufacturer.

    Are FO membranes preconditioned the same way?

    Aquaporin Inside™  flat sheet FO membranes should be soaked in DI water for a minimum of 30 min. Once wet, the membrane should not be allowed to dry.

    How about preconditioning Hollow Fiber FO modules?

    Aquaporin's Hollow Fiber FO module is delivered wet and no pre-conditioning is required. However, pre-filtration of the feed solution being filtered on the lumen side is required. Un-removed particles may damage the fibers and result in a decrease in performance.

  6. Happy holidays from Sterlitech!

    Happy holidays from Sterlitech!

    In the spirit of giving, we want to give thanks to all our customers and partners who have made 2017 a wonderful and memorable year. We look forward to continuing to foster these relationships in the years to come.

    Sterlitech will be closed on the following dates in celebration of Thanksgiving, Christmas, and New Year’s Day holidays:

    November 23-24, 2017
    December 25-26, 2017
    January 1, 2018

    Wishing you a merry holiday season!

  7. Oysters act as a natural seawater filtration system

    Oysters act as a natural seawater filtration system

    Environmental educators in Pensacola are acquainting kids with water filtration in a new, hands-on way. Instead of a class turtle, these students are raising baby oysters. This program is sponsored by the Pensacola Bay Oyster Company and supports a local nonprofit, the Bream Fisherman Association, in its efforts to educate a new generation on marine wildlife preservation. Students contribute to the efforts to expand oyster populations in Pensacola Bay by purchasing and raising baby oysters (spat). It is a challenging and rewarding task, as baby oysters are not easily cared for. They are sensitive to salinity and other environmental changes, and must be maintained in the proper environment 2 feet below the water’s surface. The juvenile oyster cages must be periodically monitored and cleaned. Only after nine months of attention are the oysters mature enough to be placed in reefs or farms.

    Oysters are an integral part of marine ecosystems, serving as an ecosystem engineer and enhancing biodiversity by improving water quality. While filter feeding, adult oysters can each process one to two gallons of water per hour, during which they remove algae, plankton, and other particles that impact water clarity. Oysters may also potentially mitigate the effects of nutrient pollution in coastal waters by fixing nitrogen and phosphorous in their shells, tissues and excrement.

    Scientists continue to investigate oysters as natural water filters.  In a recent 2015 study, waste oyster shells were shown to be better than gravel at purifying domestic water supplies from nitrogen and aerobic organisms. In another study, a restored oyster reef in a Maryland river was found to remove 20 times more nitrogen from water than a neighboring oyster-free site. And an EPA-funded study carried out by Virginia Commonwealth University researchers estimated that large-scale oyster farms can bio-assimilate almost 300 lbs of nitrogen and over 40 lbs of phosphorous in the Chesapeake Bay per harvest of 1,000,000 oysters.

    Oysters alone cannot save polluted marine habitats, but they certainly have a part to play as tiny powerful water filters. See the video below for a time-lapse of oysters in action. 

  8. Discontinued Cytoclear Glass Slides

    Discontinued Cytoclear Glass Slides

    Cytoclear Glass Slides have been discontinued by the manufacturer due to lack of commercial interest, and are no longer available for purchase. These slides were previously used to enhance microscopic visualization with PCTE and PETE membrane filters, using a special light diffusing coating that significantly reduces the appearance of the pore edges by minimizing pore edge shadows.

    If you are looking for alternative solutions to enable improved microscopic work, Sterlitech recommends wetting the membrane with a liquid that has the correct refractive index and illuminating the membrane with polarized light. For example, the PCTE membrane is birefringent and has two refractive indices, 1.584 and 1.625. To minimize the appearance of pore edges, this membrane should be wetted with a fluid that has a refractive index of 1.584 and illuminated with properly-oriented polarized light.

    Please contact us if you have any questions. To view our other membrane accessories, please visit

  9. Introducing: Hydrophobic Polyester Track-Etch (PETE) Membrane Vent Filters

    Introducing: Hydrophobic Polyester Track-Etch (PETE) Membrane Vent Filters

    Sterlitech has a new option to consider for your vent filter applications: hydrophobic polyester track-etch (PETE) membrane vent filters. The PETE membrane has been modified using a proprietary process to be rendered permanently hydrophobic. These filters may be considered for vent applications where PTFE or polyolefin membrane filters have been traditionally used. The PETE membrane filters have superior dimensional stability compared to unsupported PTFE membrane filters and have better thermal resistance than polyolefin membrane filters. Additionally, the PETE membrane filters typically have greater water entry pressures than similar pore size rated PTFE and polyolefin membrane filters while maintaining reasonable air flow rates. Finally, the inherently uniform pore structure resulting from the track-etch manufacturing process ensures that PETE membrane filters have exceptional lot to lot consistency.

    The hydrophobic PETE membrane vent filters are suitable for a wide variety of applications including vents on electrical enclosures, allowing for passage of air and other gases (such as water vapor) while preventing passage of liquid water, particles and microorganisms. The PETE membrane vent filters are also oleophobic to AATCC118 grade 5 and, consequently, can repel oils and solvents with surface tension >25dynes/cm.

    Available in a variety of pore size ratings: 0.2, 0.4, 1.0, and 1.2µm, and backed with a nonwoven polyester support layer, hydrophobic PETE membrane vent filters are easy to handle and can be supplied in custom shapes with pressure activated adhesive. Interested to learn more about this product and its use in your application? Contact Us to connect with an applications specialist.

  10. Sterlitech to Provide Larger Scale Membrane Skids for Research and Industry Customers

    Sterlitech to Provide Larger Scale Membrane Skids for Research and Industry Customers

    These pilot skid systems are specifically designed for pilot testing of spiral wound membrane filters or small scale filtration processes. They offer more than 200 times the filtration surface available in standard bench-top filtration systems, allowing users to increase throughput and obtain results that translate for scale-up. Digital skids enable hands-free monitoring of process parameters and eliminate the need to manually record data.

    Built in benefits include:
    · Pre-assembled and plug-in ready
    · Digital or analog options
    · Customizable for chemical compatibility and application requirements

    Pilot Skid systems are developed for the next level of testing, once investigators have established the proof of concept their bench-top filtration systems. Testing with the Pilot Skid allows the investigators to use full size spiral wound membranes for evaluating new processes or products and gather operational parameters and tests results that are representative of those expected in the full size membrane filtration systems.

    Pilot Skids can be used in various applications, from new process and product development to quality assurance and materials research. They offer the opportunity to increase throughput in batch processing of water and wastewater, chemicals, pharmaceuticals, and other solutions. Mounted skid systems increase productivity and establish consistency in experimental control. Whether it is reverse osmosis, nanofiltration, ultrafiltration, or microfiltration applications, the Pilot Skid is a ready-to-use system for expanding a bench-top process.

    Technical support at every step of purchasing and implementing ensures users receive optimized design and an easy introduction of their new pilot system. Sterlitech also provides an operational training webinar within one week of delivery; each webinar is interactive and tailored to the skid design and the needs and skill level of its users. Our goal is to enable customers to seamlessly move their processes to pilot scale and promote continued innovation.