Characterization of Fat, Oil, and Grease Deposits By Kevin M. Keener, Ph.D., P.E. Purdue University Department of Food Science WEFTEC 2008: Workshop #W115 WERF: The Latest on Collection System Research October 18, 2008
SSO Causes National Average 7 11 12 27 43
Impact of Sanitary Sewer Overflows SSOs are a threat to health, safety, welfare of the public SSOs cause endangerment to the environment SSO cleanups cost the municipalities thousands of dollars per event
Sanitary Sewer Overflows Their impacts 138,000 SSO s resulting from FOG per year 3,700 gallon average release per event Unpermitted release of over 500 million gallons of raw sewage per year $1 billion dollars per year remediation costs
Fats, Oils, Greases DO cause sewer main blockages Hardened grease deposits from cooking activity caused blockage and large raw sewage overflow into homeowner s yard and nearby stream
Fats, Oils, and Grease Blockages What are they? Compound fatty acids + glycerol Large grease and oil molecules: >150 microns when free floating Comes from many food sources; animal and plant origin Hydrophobic: insoluble in water, can accumulate into hardened mass that adheres to sewer pipes and equipment
Photomicrograph of FOG deposit Bands of debris deposited onto layers of FOG over time 3 cm 3 cm sliver of FOG deposit taken from interior of a cross section cut of a 14 oz chunk of hardened mass recovered downstream, in the sanitary sewer main, of a Mexican fare restaurant Image is viewed at 10 X magnification. Throughout the larger body were clearly evident dark lines and striations that presented a swirling appearance.
Methods and Materials 1. A cylindrical sample (1 cm dia. x 1 cm height) of FOG deposit was cored from a larger chunk. 2. Weight, water content, compressive strength, density, and porosity were measured based on methods of soil analysis. 3. Water content was measured according to Method 7-2.2 Gravimetry with Oven Drying (ASA, 1986). 4. Maximum compressive strength was measured using Method 34-6 Unconfined Compression (ASA, 1986). 5. Porosity was measured using the Air Space Pycnometer Method (ASA, 1986).
Methods and Materials (Cont.) 6. Mineral and Metal Analysis of FOG Deposits was performed based on AOAC (1995a) Method 990.08 Metals in Solid Waste. In brief, a 2 gram sample of FOG deposit was acidified using concentrated nitric acid. The sample was digested at 95 o C for approximately 75 minutes. The sample was then be delivered into an inductively coupled plasma (ICP) emission spectrometer. The minerals and metal analyzed included Al, Ca, Mg, Na, Cu, Zn, Fe, K, P, and other less common metals. 7. Fatty acid profiling of FOG deposits was performed based on AOAC (1995b) Method 983.23 Fat in Foods. In brief, A 5 gram sample of FOG deposit was blended along with an enzyme solution. This sample was agitated gently and held at 50 o C for one hour. Then a mixture of chloroform and methanol was added and centrifuged. The bottom layer (chloroform) was extracted. This layer contains the soluble fats. A nitrogen evaporator was then used to evaporate the chloroform. This sample was then injected into a GC-FID for analysis. This analysis determines concentration and saturation levels of C4-C20 fatty acids.
Sample Physical Properties of FOG Gas-Filled Porosity (%) Moisture Content (% w.b) Bulk Density (g/cm 3 ) Yield Strength (kpa) 1 11.26 ± 0.21 10.12 ± 0.38 0.88 ± 0.09 841 ± 24 2 14.42 ± 0.30 60.74 ± 8.43 0.89 ± 0.04 809 ± 14 3 16.54 ± 0.27 42.51 ± 6.69 0.93 ± 0.09 813 ± 9.1 4 7.11 ± 0.21 49.98 ± 6.39 0.97 ± 0.05 330 ± 78 5 23.50 ± 0.29 32.32 ± 12.78 0.86 ± 0.06 124 ± 38 Ivory 16.84 ± 0.04 23.68 ± 0.01 0.87 ± 0.11 353 ± 35 Irish Spring 9.40 ± 0.03 9.77 ± 0.01 1.00 ± 0.13 491 ± 81 Dial 4.39 ± 0.05 9.71 ± 0.01 1.00 ± 0.11 792 ± 41 Coast 6.01 ± 0.03 12.89 ± 0.02 0.97 ± 0.27 523 ± 120
Chemical Make up of FOG Deposits: Any Answers There? Common composition? Fatty acid profile
Fatty acid profiles of common cooking oils and animal fats Lipid Type Saturated Fat (%) Primary Saturated Fat Unsaturated Fat (%) Primary Unsaturated Fat (%) Polyunsaturated Fat (%) Cooking Oils Canola 7.3 Palmitic 62.9 Oleic 30.5 Linoleic Corn 13.6 Palmitic 25.6 Oleic 60.8 Linoleic Olive 12.1 Palmitic 80.9 Oleic 7.0 Linoleic Palm 49.4 Palmitic 39.5 Oleic 11.1 Linoleic Peanut 19.4 Palmitic 48.5 Oleic 32.0 Linoleic Soybean 15.4 Palmitic 23.3 Oleic 61.3 Linoleic Animal Fats Chicken Fat 33 Palmitic 45.2 Oleic 21.4 Linoleic Lard (pig) 41.8 Palmitic 47.9 Oleic 9.9 Linoleic Tallow (beef) 47.9 Palmitic 47.4 Oleic 3.3 Linoleic Primary Polyunsaturated Fat (%)
Conclusions The moisture content of FOG samples ranged from 6 to 86%, suggesting that moisture content is not a primary factor in FOG deposits. 84% of FOG deposit samples contained greater than 50% lipid content, with the primary lipid being palmitic acid (16:0). 85% of FOG deposit samples contained calcium with average concentrations of 4255 mg/l (4255 ppm). There was no correlation found between calcium concentration in FOG deposit samples and water hardness. FOG deposits preferentially accumulate saturated fats and calcium, well above background levels, suggesting that a chemical process is responsible for their formation.
THANK YOU QUESTIONS??? Kevin M. Keener, Ph.D., P.E. Food Process Engineer Extension Specialist Associate Professor of Food Science Purdue University, Room 3215 745 Agriculture Mall Drive West Lafayette, IN 47907-2009 Phone: (765) 494-6648 Fax: (765) 494-7953 kkeener@purdue.edu www.foodsci.purdue.edu