Page 11 - Filtration Resources

Last month we examined filter selection strategies for maximizing service life in continuous use applications. In this 3rd installment, we will examine the use of prefilters to extend service life.

In the area of a former military building complex in the Chaoyang District of Beijing is a unique and thriving artistic community. In the middle of this art district, is a strange 7-meter tall tower shaped like an avant-garde metallic pineapple. Designed by Dutch artist Daan Roosegaarde, it is both an artistic creation and a functional tool meant to test a possible solution for Beijing’s worsening air pollution. The tower is a giant silver-colored ionizer and particulate trap designed to pull in and hold tiny pollutants, known collectively as PM 2.5’s. The tower works by releasing charged ions into the air nearby, causing the PM 2.5 particles to become trapped on the metallic fins as they are pulled from the air.

Last month, we described the considerations associated with predicting filter service life and how total throughput can be estimated through experimentation. In this second installment, we will examine four filter selection strategies for maximizing service life in continuous-use applications. These aspects consider chemical compatibility, temperature, binding characteristics, and pore size.

For consumers using disk, syringe, and capsule filters it is a common FAQ: How long will my filter last? Or, to put it another way: How much fluid can I expect to pass through my filter before it clogs? This seems to be a simple and reasonable question for a filter consumer: Would any of us purchase a product without an understanding of its service life? However, this apparently simple question is deceivingly complex as a multitude of factors influence filter service life. Service life can be defined as the total volume of fluid that is passed through a normal flow filter until it becomes clogged; this is commonly referred to as total throughput. It is nearly impossible to predict total throughput, even with a good understanding of the application. So, as a filter manufacturer, how would we suggest approaching this challenge?

In order to provide a safe work environment, better control of vapor wastes needs to be implemented. EZ waste technology has become readily available to improve the containment of volatile liquids and prevent vapors from escaping into laboratory air. Learn about how to prevent the dangers of hazardous waste and the technology behind the closed waste system with an activated carbon filter, such as the EZ waste system. Download EZwaste whitepaper for more detail and additional instruction.

Sterlitech Corporation is proud to announce the launch of gold-sputtered polycarbonate membrane filters. “Why gold? What is sputtered?” you may ask. Well, some particles are just too small to see with an ordinary light microscope, for these things we need get down to details not seen by traditional microscopy.

A large part of extracting commercially important compounds from various materials involves passing a type of solvent over the substance, then filtering out any unwanted debris and by-products. This filtration step can be difficult to optimize if too many undesirable compounds are also extracted; so how can you streamline the process?

Numerous industries have a necessity to keep things clean and sanitary. Filters are an efficient and cost effective way to keep dirt, dust, bacteria, viruses and other small particulates out. The variety of applications are endless, and hundreds of product manufacturers employ filtration to keep things clean: from medication, to automobiles, to even your home.

Within the life sciences, it is often critical for researchers to keep the growth environments of key cells sterile for production of significant compounds. Contamination could mean the loss of hundreds of thousands of dollars’ worth of product. At university labs, cell biologists and clinical researchers alike utilize small vent filters and devices to keep their cell growth devices and growth media free of any bacteria or molds that could damage their cell lines in their ongoing research. Sterlitech offers standard syringe-filter type vents, custom syringe filter vents, and custom adhesive-backed vent discs in a variety of sizes

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

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