Lisa O. Dean

Evidence for Fat, Oil, and Grease (FOG) Deposit Formation Mechanisms in Sewer Lines

The presence of hardened and insoluble fats, oil, and grease (FOG) deposits in sewer lines is a major cause of line blockages leading to sanitary sewer overflows (SSOs). Despite the central role that FOG deposits play in SSOs, little is known about the mechanisms of FOG deposit formation in sanitary sewers. In this study, FOG deposits were formed under laboratory conditions from the reaction between free fatty acids and calcium chloride. The calcium and fatty acid profile analysis showed that the laboratory-produced FOG deposit displayed similar characteristics to FOG deposits collected from sanitary sewer lines. Results of FTIR analysis showed that the FOG deposits are metallic salts of fatty acid as revealed by comparisons with FOG deposits collected from sewer lines and pure calcium soaps. Based on the data, we propose that the formation of FOG deposits occurs from the aggregation of excess calcium compressing the double layer of free fatty acid micelles and a saponification reaction between aggregated calcium and free fatty acids.

Mechanisms of Fat, Oil and Grease (FOG) deposit formation in sewer lines

FOG deposits in sewer systems have recently been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. In this study, batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). We report the first formation of FOG deposits on a concrete surface under laboratory conditions that mimic the formation of deposits in sewer systems. Results showed that calcium, the dominant metal in FOG deposits, can be released from concrete surfaces under low pH conditions and contribute to the formation process. Small amounts of additional oil to grease interceptor effluent substantially facilitated the air/water or pipe surface/water interfacial reaction between free fatty acids and calcium to produce surface FOG deposits. Tests of different fatty acids revealed that more viscous FOG deposit solids were formed on concrete surfaces, and concrete corrosion was accelerated, in the presence of unsaturated FFAs versus saturated FFAs. Based on all the data, a comprehensive model was proposed for the mechanisms of FOG deposit formation in sewer systems.

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

Understanding the formation of Fat, Oil, and Grease (FOG) deposits in sewer systems is critical to the sustainability of sewer collection systems since they have been implicated in causing sewerage blockages that leads to sanitary sewer overflows (SSOs). Recently, FOG deposits in sewer systems displayed strong similarities with calcium-based fatty acid salts as a result of a saponification reaction. The objective of this study was to quantify the factors that may affect the formation of FOG deposits and their chemical and rheological properties. These factors included the types of fats used in FSEs, environmental conditions (i.e. pH and temperature), and the source of calcium in sewer systems. The results of this study showed that calcium content in the calcium based salts seemed to depend on the solubility limit of the calcium source and influenced by pH and temperature conditions. The fatty acid profile of the calcium-based fatty acid salts produced under alkali driven hydrolysis were identical to the profile of the fat source and did not match the profile of field FOG deposits, which displayed a high fraction of palmitic, a long chain saturated fatty acid. It is hypothesized that selective microbial metabolism of fats and/or biologically induced hydrogenation may contribute to the FOG deposit makeup in sewer system. Therefore, selective removal of palmitic in pretreatment processes may be necessary prior to the discharge of FSE wastes into the sewer collection system.

Understanding the spatial formation and accumulation of fats, oils and grease deposits in the sewer collection system.

Sanitary sewer overflows are caused by the accumulation of insoluble calcium salts of fatty acids, which are formed by the reaction between fats, oils and grease (FOG) and calcium found in wastewaters. Different sewer structural configurations (i.e., manholes, pipes, wet wells), which vary spatially, along with other obstructions (roots intrusion) and pipe deformations (pipe sags), may influence the detrimental buildup of FOG deposits. The purpose of this study was to quantify the spatial variation in FOG deposit formation and accumulation in a pilot-scale sewer collection system. The pilot system contained straight pipes, manholes, roots intrusion, and a pipe sag. Calcium and oil were injected into the system and operated at alkaline (pH = 10) and neutral (pH = 7) pH conditions. Results showed that solid accumulations were slightly higher at neutral pH. Fourier transform infrared (FTIR) analysis on the solids samples confirmed that the solids were indeed calcium-based fatty acid salts. However, the fatty acid profiles of the solids deviated from the profile found from FOG deposits in sewer systems, which were primarily saturated fatty acids. These results confirm the work done previously by researchers and suggest an alternative fate of unsaturated fatty acids that does not lead to their incorporation in FOG deposits in full-scale sewer systems.

Effect of Feeding by a Burrower Bug, Pangaeus bilineatus (Say) (Heteroptera: Cydnidae), on Peanut Flavor and Oil Quality

A burrower bug, Pangaeus bilineatus (Say) (Heteroptera: Cydnidae), is known to feed extensively on peanut, Arachis hypogaea L., pods; particularly under certain reduced tillage production conditions. These bugs produce a strong odor when infested peanuts are uprooted, and previous anecdotal evidence indicated that burrower bug feeding is detrimental to peanut flavor. Various levels of burrower bug kernel feeding (0, 5, 10, 25, and 50% of seed by weight) were evaluated for effects on peanut flavor and oil quality. Burrower bug feeding had no detrimental effect on flavor as determined by trained panelists using descriptive sensory analysis. There was a slight, but measurable effect on oil quality as determined by a decrease in oxidative stability and an increase in peroxide values with increased levels of feeding. There was no measurable effect on free fatty acid content or fatty acid profile at the feeding levels tested. The data indicate that incidental feeding (<20% of seed) by this pest is unlikely to be detrimental to peanut flavor. At higher feeding incidence levels, the potential risks of direct yield loss, grade reductions, and aflatoxin contamination are of greater significance than concern for relatively minor reductions in oil quality.

Intensities of Sensory Attributes in High- and Normal-Oleic Cultivars in the Uniform Peanut Performance Test

ABSTRACT In order to ascertain whether or not flavor differed between high- and normal-oleic peanuts (Arachis hypogaea L.), data from the quality assessment phase of the Uniform Peanut Performance ...

Attenuated Total Reflectance Fourier transform infrared spectroscopy for determination of Long Chain Free Fatty Acid concentration in oily wastewater using the double wavenumber extrapolation technique

Long Chain Free Fatty Acids (LCFFAs) from the hydrolysis of fat, oil and grease (FOG) are major components in the formation of insoluble saponified solids known as FOG deposits that accumulate in sewer pipes and lead to sanitary sewer overflows (SSOs). A Double Wavenumber Extrapolative Technique (DWET) was developed to simultaneously measure LCFFAs and FOG concentrations in oily wastewater suspensions. This method is based on the analysis of the Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectrum, in which the absorbance of carboxyl bond (1710cm-1) and triglyceride bond (1745cm-1) were selected as the characteristic wavenumbers for total LCFFAs and FOG, respectively. A series of experiments using pure organic samples (Oleic acid/Palmitic acid in Canola oil) were performed that showed a linear relationship between the absorption at these two wavenumbers and the total LCFFA. In addition, the DWET method was validated using GC analyses, which displayed a high degree of agreement between the two methods for simulated oily wastewater suspensions (1-35% Oleic acid in Canola oil/Peanut oil). The average determination error of the DWET approach was ~5% when the LCFFA fraction was above 10wt%, indicating that the DWET could be applied as an experimental method for the determination of both LCFFAs and FOG concentrations in oily wastewater suspensions. Potential applications of this DWET approach includes: (1) monitoring the LCFFAs and FOG concentrations in grease interceptor (GI) effluents for regulatory compliance; (2) evaluating alternative LCFFAs/FOG removal technologies; and (3) quantifying potential FOG deposit high accumulation zones in the sewer collection system.

The effects of different dry roast parameters on peanut quality using an industrial belt-type roaster simulator

Peanuts roasted to equivalent surface colors at different temperature/time combinations can vary substantially in chemical and physical properties related to product quality. This study used a pilot plant scale roaster that simulates the configurations of one of the most common industrial roaster, a multi-zone belt roaster. Jumbo-size runner-type peanuts were systematically roasted at 5 temperatures (149-204°C) to three Hunter l-values of 53, 48.5, and 43, corresponding to light, medium, and dark roasts. Moisture and tocopherol contents were more closely correlated with roast color rather than temperature, with exceptions at 149°C. Moisture decreased with darker roast color, while the total tocopherols were greatest in peanut oils with darker colors. Yield stress of peanut pastes increased as the color darkened, indicating spreadability correspondingly decreased with darker roast colors. The overall flavor of roasted peanuts was found to be optimized at 177°C/15min with the medium roast color.

Chemical Composition of the Essential Oils from Leaves of Edible (Arachis hypogaea L.) and Perennial (Arachis glabrata Benth.) Peanut Plants

Abstract: Peanut or groundnut (Arachis hypogaea L.) is a valuable oilseed crop, but other than the seed, the rest of the plant is of minimal value. Plant material including the leaves is used as soil conditioner or as animal feed. Perennial peanut (Arachis glabrata Benth and Arachis pintoi Krapov & W.C. Greg) known as forage or rhizoma peanut produces few seeds, but is grown specifically as a forage, turf or ornamental plant. The leaves from the peanut plants of the cultivated variety, Bailey and the perennial varieties, Arblick, Arbrook, and Amarillo were freeze dried, essential oils were extracted by distillation and the chemical compositions were determined using gas chromatography and gas chromatography-mass spectrometry. Oil yield from the A. hypogaea leaves was 0.0063 % (w/w). The major components were 1-octen-3-ol (12.4 %), heneicosane (11.7 %), nonanal (10.9 %), 4-vinylguaiacol (6.4 %) and phytol (7.4 %). The yield from A. glabrata and A. pintoi leaves ranged from 0.0044 % to 0.0061 % (w/w) with the major components in common among the three varieties tested 1-octen-3-ol (40.5-44.9 %), β-linalool (5.0-8.9 %) and 4-vinylguaiacol (1.4-8.6 %).