Understanding The PeriFilter Technology
There is a newly-developed technology, the so-called PeriFilter® that will hit the market within the next few weeks. This offers many heretofore technological and economic advantages in the separation of solid phases from liquid phases with concomitant transformation of the solid phases into processable forms for further usage and/or products. It may be used in the separation of solids from liquids in water purification and in wastewater treatment applications as well.
There are several filter types and sub-types employed in separation of solid phases from liquid phases. They run the gamut from bed filters to barrier filters, from membrane filters to ultrafilters, but they all have one thing in common – they are all dependent on pressure to drive the fluid phase through the filter. The filter itself remains stationary. And, all of them have capacities associated with them before they clog up and have to be cleaned.
In the new PeriFilte® technology, the design process was used to change the rules to result in a filter that was itself an active component. The PeriFilter® demonstrates peristaltic-like characteristics that do not originate from modifications of peristaltic changes in the fluid stream emanating from peristaltic pumps but rather from the filters themselves, the hydraulic loading of the to-be-separated components and/or phases, and from outside manipulations from components (principally roller-like devices) that are designed to implement a wave-like (peristaltic) motion to the contents of the filter tube assembly.
This PeriFilter® is, in fact, a filter that is part of a tubular arrangement wherein the to-be-separated stream is confined to the lumen of the PeriFilter®. As this stream is confined within the lumen, there is no spill-over nor leakage into the mechanism (or environment), and ideally the contents will exhibit mostly laminar flow characteristics as the solid/liquid phase stream moves down and out of the lumen to its terminus. As the biphasic system passes through the PeriFilter® part of the system, the liquid phase is removed to a great extent by a tangential flow across the PeriFilter®. This flow may be increased, depending on the particular application, by utilizing filters that have been modified by biased weaving. Any fluid phase not passing through the filter will remain to hydraulically “push” the solid phase on through as well as providing a constant cleaning motion that prevents fouling of the PeriFilter®. The resultant situation is one of a self-cleaning filter.
The solid phase itself is modified by the addition of various flocculants which are introduced into the to-be-treated stream. These flocculants may be synthetic, for example, various acrylamide polymers with different behaviors (anionic, cationic, or mixed resins), or they may be naturally occurring, for example, Zeolites, Bentonites, Kaolins, Montmorrilonite Clays, or other silicate based entities that may be further modified chemically by treatment to effect a specific behavior. This results in a solid phase that can be made to act as a sequestering agent for various ions and compounds, to act as an ion-exchange medium, or to otherwise change the flow characteristics to enable a more efficient separation process of the two phases (solid vs. liquid).
The solid phase is “dewatered” or “deliquified” depending on the fluid phase as the solid phase moves down the tubular assembly and exits as a (more or less) stackable, manageable solid cake.
This solid cake can now be processed into other products including food supplements for animal use, used as a fertilizer for crops to enhance nitrate and phosphate content, or even as a feedstock for metallic extraction of sequestered minerals and ions within the solid matrix. It should be understood that a certain amount of the liquid phase remains in this solid cake (as a general rule this cake retains a solids concentration of approximately 30%, which results in it being stackable). This PeriFilter® solid cake may be dried more easily than many other solid cakes with lower water content because the residual liquid is so loosely bound.
The understanding of the general principles of this technology allows one to consider various applications for specific uses. As the stream to be treated enters into the system, a flocculant is added to ensure that a well-defined solid phase with desirable characteristics is formed. By manipulating the chemical characteristics of these flocculants, one can control the chemical reactions and the varying separations possible by the application of the technology to a multitude of separations, processes, and sequestrations. Such an application in the food processing industry would use non-toxic, food grade, naturally occurring flocculating agents.
In addition to the manipulations of the flocculants employed, one can also modify the filter itself in several ways as mentioned earlier. These filters can be bias-sized with variable pore sizes dependent on longitudinal tensioning to effect particular solid phases and their dewatering characteristics, but they can also be increased in both diameter and length dependent on the flow-through desired for the system application. A higher or lower percentage of dry solids can be achieved by means of an appropriate change of dwell time in the lumen.
In fact, the PeriFilter® is scalable by adding multiple filters for particular applications in which a greater capacity, that is, a through put is required.
The control systems for this technology employ a variety of sophisticated feedback features including those that define flocculation characteristics of the solid phase by means of a Total Suspended Solids sensor; similarly, pneumatic control systems are used for tensioners which include those that are related to the peristaltic control (pore size of the filter) and roller mechanisms; plus other types of sensors and effectors that may be employed as chemical controllers should the need arise in a specific application.
Because of the versatility of this technology in addressing so many previously recalcitrant problems and because of the complexity of many of these encounters, the PeriFilter® organization employs dedicated scientists/engineers to introduce the system into new situations.
Advantages of the PeriFilter® system are numerous and in addition to those mentioned are its small foot print, low energy usage, minimal maintenance, scalability, application versatility and low cost, compared to typical dewatering systems. These units are also available as self-contained mobile units.
There are many ways that the PeriFilter® organization can assist customers in saving significant amounts in their processes both by the siting and operation of these units. We can only “scratch the surface” in this brief introduction.