Overview of current research on the formation mechanism of sewer deposits created from a reaction of free fatty acids and calcium.

1. “Let’s Clear the FOG”
Michael Keleman
Manager, Environmental Engineering
InSinkErator
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2. Background
• Limited Research on Formation Mechanism
• Much in Last Five Years
• Limited Number of Principal Investigators
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3. Overview
• Background on Research of Deposit Mechanism
• Triglycerides 101
• Contemporary Research Conclusions
• Sources of Free Fatty Acids
• Properties of Free Fatty Acids
• Hypothesis of Deposit Mechanism
• Discussion
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4. • Fats
- Lard, Shortening
- Solid at Room Temperature
- Liquid With Some Heat Added
• Oils
- Vegetable (Corn, Soybean)
- Liquid at Room Temperature
• Grease
- Fryers
- Liquid at Room Temperature
- Able to Withstand High Temperatures
Triglycerides 101
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5. FOG or Something Else?
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6. Keener, Kevin M., Joel J. Ducoste and Leon M. Holt.
2008. “Properties Influencing Fat, Oil, and
Grease Deposit Formation.” Water Environment
Research. 80:12, pp.2241-2246.
• Characterized the Chemical and Physical Makeup of 27
Samples of FOG Deposits from Different Collection
Systems.
• Deposits Contain High Amounts of Saturated Fats and
Calcium - Higher Than Background Levels.
• Determined that FOG deposits are formed primarily by
saponification and are metal soaps.
• Part of Water Environment Research Foundation’s “Fats,
Roots, Oils and Grease in Centralized and Decentralized
Systems.” (FROG Study)
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7. He, Xia, Mahbuba Iasmin, Lisa o. Dean, Simon E. Lappi,
Joel J. Ducoste and Francis L. de los Reyes III.
2011. “Evidence for Fat, Oil, and Grease (FOG)
Deposit Formation Mechanisms in Sewer Lines.”
Environmental Science &Technology. 45 (10), pp.
4385–4391.
• FOG Deposits Can Be Formed in Laboratory Using CaCl2
and Grease Interceptor Effluent.
• Without Free Fatty Acids (FFAs), Calcium Salts Do Not
Form.
• Both Lab and Field Deposits Similar to Calcium Soap
Based on Fourier Transform Infrared Spectroscopy (FTIR)
Analysis.
• Field Deposits Contain Un-reacted FFAs.
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8. Williams, J.B., C. Clarkson, C. Mant, A. Drinkwater and
E. May. “Fat, Oil and Grease Deposits in Sewers:
Characterisation of Deposits and Formation
Mechanisms.” Water Research. 46(2012), pp.
6319- 6328.
Two Mechanisms May Affect the Physical Properties
of FOG Deposits.
1. Biodegradation with Transformation of Fatty Acids from
Unsaturated to Saturated Forms.
No Double Bonded Carbon Atoms
2. Biocalcification Where Higher Levels of Water Hardness
Lead to Harder Deposits with Higher Melting Points.
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9. Dominic, Christopher Cyril Sandeep, Megan Szakasits,
and Joel J. Ducoste. 2012. “Understanding the
Spatial Formation and Accumulation of Fats, Oils
and Grease Deposits in the Sewer Collection
System.” WEFTEC 2012.
• FOG Deposits Can be Formed in a Lab Pipe Loop Reactor.
• Deposit Formations More Likely to Occur at Pipe Fitting
Ridges, Roots and Sags.
- not in straight sections of pipe
• Higher pH Leads to Greater Solids Buildup.
• CaOH2 Released at the Surface of Concrete May Lead to
Alkali Hydrolysis of FOG.
• Calcium Based Fatty Acid Salts Confirmed with FTIR-ATR,
Attenuated Total Reflectance.
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10. Reyes, Francis de los and Joel J. Ducoste. 2012.
“Factors Affecting the Formation of Fats, Oils,
and Grease Deposits in Sewer Systems.” Water
Resources Research Institute of the University of
North Carolina.
• FFAs Produced from Cooking Processes & Discharged with
Kitchen Wastewater to Sewer.
• FFAs Partition in FOG & Flow on Wastewater Surface.
• FFAs React with Calcium from Concrete or Wastewater to
Form FOG Deposits.
• Sticky Solid Formed after Saponification Will Congregate
and Adsorb FFAs, Calcium and Debris to Increase FOG
Deposit.
• Surfactants Appear to Inhibit FOG Deposit Formation.
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11. 11
Fatty Acid Profiles of Common Vegetable Oils and Animal Fats
Lipid Type
Saturated Fat
(%)
Primary
Saturated
Fat
Unsaturated
Fat (%)
Primary
Unsaturated
Fat
Polyunsaturated
Fat (%)
Primary
Polyunsaturated
Fat
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 Linoleic
Palm 49.4 Palmitic 39.5 Oleic 11.1 Linoleic
Peanut 19.4 Palmitic 48.5 Oleic 32 Linoleic
Soybean 15.4 Palmitic 23.3 Oleic 61.3 Linoleic
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
Animal Fats
Vegetable Oils

12. Free Fatty Acids
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13. So What Do We Know?
• Sewer FOG Deposits
Insoluble Calcium Soaps
• Precursor Sources
▫ Calcium
 Concrete
 Water Hardness
 Urine
 Dairy Products
• Free Fatty Acids
▫ Hydrolyzed FOG
 Vegetable Oils
 Animal Fats
▫ Personal Care Products
▫ Feces
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14. Michael Keleman
michael.keleman@emerson.com
262-598-5219
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