Department of Civil, Construction and Environmental Engineering, North Carolina State University, Raleigh, NC 27695, USA.
Water Res. 2013 Sep 1;47(13):4451-9. doi: 10.1016/j.watres.2013.05.002. Epub 2013 May 15.
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.
污水系统中的 FOG 沉积物最近已被证明是脂肪酸的金属盐。然而，FOG 沉积物反应物成分的命运和迁移以及 FOG 沉积物形成过程中的复杂相互作用在很大程度上仍不清楚。在这项研究中，进行了批量测试以阐明导致卫生污水溢出（SSO）的 FOG 沉积物形成的机制。我们报告了在实验室条件下首次在混凝土表面上形成 FOG 沉积物，该条件模拟了污水系统中沉积物的形成。结果表明，在低 pH 条件下，FOG 沉积物中占主导地位的金属钙可以从混凝土表面释放出来，并有助于形成过程。向油脂截留器废水添加少量额外的油会极大地促进游离脂肪酸和钙之间的空气/水或管道表面/水界面反应，从而在表面上产生 FOG 沉积物。对不同脂肪酸的测试表明，在存在不饱和 FFAs 时，混凝土表面上形成了更多粘性的 FOG 沉积物固体，并且混凝土腐蚀加速。基于所有数据，提出了一个全面的模型来解释污水系统中 FOG 沉积物形成的机制。
