Page 43 - Blog

Researchers from the European Monitoring Center for Drugs and Drug Addiction are zeroing in on public toilets in Europe to identify drug use patterns across the continent. Over the past decade, sewage plant wastewater has been a top source for monitoring drug consumption. However, due to the rising number of new psychoactive substances on the market, scientists have had to come up with new ways to identify suspicious chemicals more effectively. In a recent publishing entitled “Assessing illicit drugs in wastewater”, the EMCDDA expounds on new methodologies for scanning through sewage water to identify drug use trends in different cities. Part of the report includes references to studies that sourced and analyzed wastewater directly from public toilets where drug use was thought to be common. According to the paper, this technique allows researchers to carry out more geographically detailed analyses as well as identify drugs whose uses are still unknown. Through the traditional method, water

When particles of a known and defined size are removed via filtration, it is fairly easy to choose the right filter by simply selecting a pore size smaller than the particle. But what happens when you need to filter a very dirty solution that contains an innumerable amount of particle sizes? If a pore size too small is chosen, a cake layer of debris will form on the membrane surface and foul it completely. If too big of a pore size is selected, then a large portion of the solids will pass right through the filter. Because it could be easily overdone, it’s usually not a good idea to stack multiple filters in the same filter holder and process it all at once. So what is an effective solution to this problem?

Enter the world of pressure drop! Back in 1856, French hydrogeologist Henry Darcy figured out the physics behind fluid flow in a filter medium while he was working in Dijon, France (yes, also the little town that gave us great mustard). Henry figured out that in order to push a liquid

In 2015, the US Food and Drug Administration (FDA) signed off on new legislation to finalize the Food Safety Modernization Act (FSMA), which requires food and beverage manufacturers to be more proactive to minimizing food-borne contamination from microorganisms. The FDA now places more effort on the individual companies to test food products according to the new guidelines in various parts of the production process. These processes can be ideal places to draw fluid samples for bacterial capture and subsequent analysis. The use of membrane filters to evaluate bioburden in these types of liquids is the standard means of recovering and quantifying potentially harmful microorganisms. Does this sound like it makes for more work for the food processors in our communities? It might, but Sterlitech Corporation can help!

According to the new regulations, high-risk food producers will be inspected more frequently, will have to maintain more detailed records, and establish clear food safety plans.

What is silt density index (SDI)?
Silt density index (SDI) estimates the quantity of suspended solids and colloids inside of water. SDI is measured following the ASTM D19.08 Standard Test Method for Silt Density Index (SDI) of Water, using a 0.45 micron membrane. SDI provides information about the fouling potential of water treatment equipment, including membrane filtration systems, and therefore is commonly used in their design and choice.

Is SDI a reliable fouling propensity parameter? How is it used?
SDI is a simple and helpful tool extensively used in pilot or large-scale treatment plants as a standard test to verify the fouling potential of RO and NF membranes. However, using SDI to estimate the fouling intensity of water treatment equipment has some limitations. Even though SDI is measured using a dead-end filtration unit, hydrodynamic conditions in dead-end filtration units are not representative of the hydrodynamic conditions of NF/RO membranes. Hydrodynamic conditions in membranes

 Q: What is Cross Flow Velocity?  

A: Cross flow velocity (CFV) is the linear velocity of the flow tangential to the membrane surface and is reported in [m/sec] or [ft/sec]. CFV affects the hydrodynamic conditions in the cell, and as a result affects the fouling rate and formation of concentration polarization at membrane surface and is calculated by dividing the volumetric flow rate [lpm or gpm] in the flow channel by the cross sectional area [m² or ft²] of the flow channel.  

Q: How is CFV calculated in Sterlitech’s bench-scale test cells?  

A: Example: Calculate CFV in the CF042 cell  

• Flow channel cross sectional area: Channel depth x Channel width* = 0.23 x 3.92 cm
• Flow rate: 1 l/min = 1/60000 m³/s
• CVF = (1/60000 m³/s) / (0.0023 x 0.0392 m)= 0.18 m/s

*Contact us for more information about channel width in CF016 and Sepa cell

Q: How is CFV calculated when shims or feed spacers are inserted in the flow channel?  

A: Adding shims to the flow channel reduces the depth of

Sterlitech teamed up with Senior Engineering Students at California State Polytechnic University, Pomona (Cal Poly Pomona) to evaluate the design of a tangential flow Air Gap Membrane Distillation (AGMD) test cell. Membrane Distillation (MD) is a thermally driven membrane separation technique used for desalination. In this process, the driving force is the difference in the vapor pressure on both sides of the membrane, where permeate travels through a hydrophobic membrane in a vapor phase. Advantages of MD process over conventional distillation or pressure driven separation processes are:

• Low Operating Pressures
• Low Operating Temperatures
• Less Susceptibility to Fouling

These all translate to lower energy requirements that make MD an energy efficient separation process. Scope of the Project: A bench-scale tangential flow test cell is configured in this project where feed solution is circulated tangentially to the membrane in the feed channel on one side and the coolant solution is circulated

Water, oils, and solvents sometimes need to be filtered. But when you see filters labeled as hydrophilic, hydrophobic, and now oleophobic; what does all this mean?  Sterlitech currently offers membrane disc and sheet filters in 10 different polymer types and 4 inorganic filters. 2 of the polymer types are subdivided into 4 subgroups based on surface chemistry alone.

Filters listed as hydrophilic, which has its origins in the Greek language and means water (hydro) loving (philos), love to get wet! Hydrophilic filters will easily pass water or water-based solutions such as dairy, river water, seawater, cell culture solutions, buffers, beverages, and many more. The filters best suited to handle these solutions are silver, ceramic, glass fiber, cellulose acetate, mixed cellulose ester (nitrocellulose), nylon, polyester, polycarbonate (PVP-treated), polyacrylonitrile (PAN), and PVDF. They can be used for almost any application that needs particle removal, clarification, cell

North American Membrane Society (NAMS) annual meeting was held in Bellevue, WA, during the last week of May. Due to the great collective interest shown by the membrane research community, only 40% of the abstracts submitted to the meeting could be accepted for podium presentation, which made up to about 140 talks! In addition, about 140 posters were presented in 5 parallel poster sessions. As a comparison, there were about 144 talks and 160 posters in NAMS 2015 meeting at Boston. Conference attendees were primarily researchers from industry and academia.   Research was focused on the following topics:

• Membrane Distillation (MD)
• Biomimetic membranes
• Desalination and potable water production
• Gas separation
• Design and processing of polymeric and inorganic membranes
• Designs and processing of composite and hybrid membranes
• Novel membrane materials

Other topics of interest included:

• Pervaporation
• Membrane transport: theory and characterization tools
• Water treatment, reclamation, and reuse
• Energy

Sterlitech’s polycarbonate and polyester track-etch membrane filters are a unique product that find use in numerous applications. They possess clean cylindrical pores that transverse the membrane surface from one side to the other. As a result of this unique feature, the pore density must be much lower compared to almost all other standard thin-film membranes such as Nylon, PTFE, PVDF, and more. Particulates either pass through the pores in track-etch filters, or remain on the surface. Almost never do they become embedded within the pore’s interior. But what happens when these filters are needed for your project and the particles being filtered occlude the opening of the pores? This effect is called pore blinding; and you may ask “But what can be done?”

Fear not brave scientist! In most applications, the track-etch filters will work fine on their own. But if a difficult particulate is clogging up your filter too soon, consider use of our Polyester Drain Discs. These discs act as a pre-filter

They’re back! Last year, Sterlitech discontinued offering the economical Rocker vacuum pump series due to supply issues. We’re happy to report the issues are worked out and they’re now back to our product lineup! These pumps complement a family of durable and economical lab products designed to help your filtration needs.

The Rocker pumps include the models 300, 400, and 600 in both 110V/60Hz and 220V/50Hz units. These pumps are outstanding economical resources for wide ranging lab applications based on simple aqueous solutions. In addition to the Rocker pumps, we also offer the Rocker repair kits, when needed, to rebuild the pumps after they go past the extra mile.

The Rocker pumps are now online at Sterlitech.com and Amazon.com, but you can always contact us directly for a quote or tech support if needed prior to ordering. If your requirements are for more chemically harsh or demanding environments, consider our heavier duty TLD or Gast vacuum pumps; available here.