IWA Publishing

Profile: Factors that influence properties of FOG deposits and their formation in sewer collection systems


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The quantification of the factors that may affect the formation of the fat, oil, and grease (FOG) deposits and their chemical and rheological properties were predominantly covered in the paper. The factors included the types of fats used in food service establishments (FSEs) and the types of calcium sources and environmental conditions (i.e. pH and temperature) in sewer systems. These factors are particularly relevant as they influence the fundamental chemistry of the FOG deposit formation. The chemistry involves a reaction known as saponification where calcium-based fatty acid salts (i.e., FOG deposits) are formed under alkali-driven conditions when FOG from kitchen establishments comes in contact with calcium ions from the wastewater. The study is quite relevant  to current research efforts to reduce nationwide sanitary sewer overflows (SSOs) that are related to FOG deposit formations inside sewer collection systems. The paper addresses these points by preparing laboratory based calcium-fatty acid salts in with several fats (Canola and Beef Tallow) and calcium sources (calcium chloride and calcium sulfate) under mild (neutral pH and room temperature) to moderately high (pH 10±0.5 and ≈14 and 45°C) environmental conditions. The chemical structures of the fatty acid salts were studied using a finger printing technique called Fourier Transform Infrared Spectra – Attenuated Total Reflection (FTIR-ATR) analysis. The chemical (fatty acid and calcium contents) and rheological (storage and loss moduli) properties of the fatty acid salts were analyzed following the standard methods (AOCS Ce 2-66, EPA 200.7) and a REOLOGICA instrument, respectively. Field samples of FOG deposits were also collected and analyzed under the same methods. The results were then compared and the possible influence of the source and environmental factors in producing FOG deposits were discussed.

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