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wateronline.com ■ Water Online The Magazine to as rugose, which means heavily wrinkled. Their decomposition depends on the microorganisms present and the enzymes that they provide. Upon microscopic examination of these particulates, one can readily observe the rugose surface areas of the solid microparticulates, which results in their increased rate of degradation by the microbial enzymes. Physical And Chemical Catalysts The production of these microparticulates is accomplished by devices that provide a shearing environment and also deliver a charge of oxygen that can be assimilated into the various wastestreams and deposits encountered. Some devices are designed to engender an extreme shear on FOG deposits and transform them into reactive microparticulates. By actually increasing the availability of oxygen to resident microorganisms, as well as to enzymatic action on the FOG particulates as they are pulverized, a radical result on the deposits is achieved. Note that shear and turbulence are the critical factors. The provision of oxygenation is, of course, a desirable feature, but some decomposition regimens occur under anaerobic conditions. No matter how the metabolic degradation of the wastestream is affected, these smaller particulates (with radically increased surface area) will be more efficiently degraded by the appropriate microorganisms and their enzymatic "packages." This is a consequence of surface area and collision probabilities from the turbulence. A small amount of ozone or other "charge carrier" molecule may also be injected to establish a charge on the formed particulates. This stabilizes the particulates in the liquid stream so that they don't settle out in the collection lines as they are pumped into the wastewater treatment plant (WWTP). Depending on the size of the particulates engendered, ozone charging may not be necessary, as sufficiently small particulates will carry sufficient charge (colloidal particles) to remain in suspension. Of course, all this time, enzymatic action will be "working" on them from the plethora of microorganisms that are inherent in most collection systems and wastestreams. There are several principles that enable FOG deposits to be degraded. We have seen that shear, turbulence, and enzymatic action are the "ball game" in this regard. Shear and turbulence are physical in nature, while enzymatic action is chemical. Three entirely different methods may be used to resolve FOG at the WWTP. FOG Removal Systems: Choose Wisely In some devices, the principle is to use a Venturi draw (by means of air lift bubbles or otherwise) to impact the wastestream solids against a sharp edge or other immovable object to generate microparticulates. As a circulation is developed, the wastestream becomes less viscous, thereby increasing the velocity at which the particulates are slammed into the immovable (and sharp) edge. The particulates are constantly reduced in size by this action, and it is relatively easy to provide oxygenation from the airlift bubbles used to engender the Venturi draw, as well as smaller diameter bubbles specifically tailored to create this outcome. In other devices, the principle is to use a propeller- type mixing blade to reduce the size of the particulates. By judiciously choosing the type of mixing blade used, one can also entrain oxygen into the process from either a pure oxygen source or an atmospheric one. In yet other devices, the wastestream is pressurized and then injected into a lower pressure zone, resulting in the destruction of the solid particulates into even smaller ones. These devices are more effective where the suspended solid levels are very low and are usually dedicated to these applications. However, ordinary wastestream systems rarely, if ever, deploy this method. As is the case so many times, the method chosen is the one that is the simplest to set up, install, and is economical with respect to power usage. In short, cheap is not only good, but essential. We have come a very long way in a relatively short time in addressing the FOG issue, and we can now control the situation expeditiously and economically. Milk fat deposits wash ashore at a dairy plant treatment lagoon. Dr. J.H. Wakefield is a consulting scientist/engineer with more than 30 years of experience in water/wastewater treatment. He holds advanced degrees in microbiology and physical/ analytical chemistry and has been a practicing chemical and environmental engineer for many years. White Paper 35