Skip to main content
ARS Home » Southeast Area » Raleigh, North Carolina » Market Quality and Handling Research » Research » Publications at this Location » Publication #285047
Title: Mechanisms of Fat, Oil and Grease (FOG) Deposit Formation in Sewer Lines

Author
item HE, XIA - North Carolina State University
item DE LOS REYES, FRANCIS - North Carolina State University
item LEMING, MICHAEL - North Carolina State University
item Dean, Lisa
item LAPPI, SIMON - North Carolina State University
item DUCOSTE, JOEL - North Carolina State University

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2013
Publication Date: 9/1/2013
Citation: He, X., De Los Reyes, F.L., Leming, M.P., Dean, L.L., Lappi, S.E., Ducoste, J.J. 2013. Mechanisms of Fat, Oil and Grease (FOG) Deposit Formation in Sewer Lines. Water Research. 47:4451-4459.

Interpretive Summary: Fat, oil and grease (FOG) in wastewater discharged from food service establishments and private homes may lead to FOG blockages in sanitary sewer pipes and consequently sanitary sewer overflows in many wastewater collection systems. These overflows can potentially release high amounts of dangerous bacteria, nutrients and solids that put public health and the environment at risk. This work is a study of the production of these blockages under laboratory conditions in order to establish the ways in which these blockages are formed in the sewer systems to develop ways to prevent their formation.

Technical Abstract: FOG deposits in sewer systems recently have 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. Batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). Tests showed that calcium, the dominant metal in FOG deposits, was released from concrete under low pH conditions. We report the first formation of FOG deposits on a concrete under low pH conditions. We show that small amounts of oil to grease interceptor effluent play the role of carrier of free fatty acids (FFAs) and facilitate surface reactions between FFAs and calcium to produce surface FOG deposits. Test 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, we propose a comprehensive model of the mechanisms of FOG deposit formation in sewer systems.