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Technology Seeing Through The FOG (Fats, Oils, And Grease) A review of different methods and devices for FOG removal, with emphasis on cost control, lowered power profiles, and efficacy By Douglas D. Sunday and Dr. J.H.Wakefield F of these compounds and the particulate characteristics OG deposits are the bane of the wastewater also attribute mightily to the chemical activity. For industry, affecting both the collection and example, it is well-known that saturated fats are much treatment functions. Over the years, there have harder to degrade microbially than unsaturated or been many attempts to "get a handle" on this polyunsaturated fats. Why this is the case resides in problem, and there have been many different ways both the chemical sites of attack by different microbial proposed in these efforts. Let us examine one of the enzymes involved, as well as how these enzymes are latest that is proving to be successful. able to operate on these differing sites. To begin with, we should understand both the It is analogous to comparing the surface of a lamellar chemical and physical identity of what actually structure (such as graphite comprises FOG deposits. or a composite material) to They are an unholy "gemisch" a piece of steel wool. The of various lipids of widely graphite surface presents few different chemical and physical active sites for an enzyme to behaviors. They vary from oils attach to, whereas a tortuous (which are in liquid form) to surface, such as steel wool, greases (which may be solid provides many such attachment or semisolid, depending on sites for an enzyme to take their chemical identities), to advantage of. In a similar (or fats (which are usually solids, analogous) manner, saturated though they too may exhibit fats present a very limited liquid or semisolid form), opportunity for enzymatic as well as waxes (which are degradation, as opposed to almost always solids). They A look into FOG: fats, oils, and grease accumulation that found in both unsaturated also can contain compounds and polyunsaturated fats. that are lipid-soluble, such as steroids, various pharmaceutical agents, and even An Alternative Solution organic solvents. A new class of digesters has been designed to modify the Currently, the most successful removal method substrates (e.g. FOG deposits) by converting them into involves the breaking down of these FOG deposits into microparticulate surfaces in which the microbial enzymes microparticulates. These engendered microparticulates find ready access to these hard-to-breakdown compounds may be emulsoids (usually oils in a liquid suspension), or molecules. At the same time, these digester devices are or they may be solids, which exhibit very small sizes. providing extreme turbulence (to facilitate collisions and As a consequence of these small sizes, the surface subsequent attachment) for the benefit of these degrading area is increased dramatically, and chemical reactions, microorganisms to "work their magic" and feeding them a which are slow to nonexistent with larger particles, most digestible diet of nutrient-rich particulates delivered can be of great importance in the degradation of these in an oxygen-rich environment. Although it is well to really small particles. This is particularly evident in the remain mindful of general principles, in the real world of microbiological degradation of these FOG compounds. waste treatment, success or failure depends on how well We all know that increased surface area, per se, the system is engineered to deliver these considerations virtually always results in increased reactivity. What we in a practical manner. tend to dismiss is that the actual physical configuration 40 wateronline.com ■ Water Online The Magazine