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

Authors: HAO, ZISU - North Carolina State University; MALYALA, DIVYA - North Carolina State University; Dean, Lisa; DUCOSTE, JOEL - North Carolina State University

Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2017
Publication Date: 4/1/2017
Citation: Hao, Z., Malyala, D., Dean, L.L., Ducoste, J. 2017. 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. Talanta. 165:526-532. https://doi:10.1016/j.talanta.2017.01.006.
DOI: https://doi.org/10.1016/j.talanta.2017.01.006

Interpretive Summary: Sanitary sewers carry untreated sewage from the point of production to the wastewater treatment plants. They are subject to the build up of solid materials from fat, oil and grease (FOG) that block the flow of the waste material and cause the sanitary sewers to overflow spreading potential pollutants and bacteria on to surface streets and other areas. The major compounds contributing to these blockages are long chain free fatty acids from cooking oils and food waste. This publication reports on the use of Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) to determine the composition of the solid blockages. This method requires less sample preparation than conventional methods such as gas chromatography. It can be used for rapid analysis to determine the source of blockages and aid in compliance of potential discharge sites with wastewater regulations.

Technical Abstract: 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 (1710 cm-1) and triglyceride bond (1745 cm-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 10 wt%, 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.