Department of Civil & Environmental Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA E-mail:
Water Sci Technol. 2013;68(8):1830-6. doi: 10.2166/wst.2013.428.
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.
污水下水道溢流水是由不溶性脂肪酸钙盐引起的，这些钙盐是由废水中的脂肪、油和油脂（FOG）与钙反应形成的。不同的下水道结构配置（例如，检查井、管道、湿井），在空间上有所不同，还有其他障碍物（根系入侵）和管道变形（管道下垂），可能会影响 FOG 沉积物的不利积聚。本研究的目的是量化中试规模下水道收集系统中 FOG 沉积物形成和积累的空间变化。该试验系统包含直管、检查井、根系入侵和管道下垂。将钙和油注入系统，并在碱性（pH = 10）和中性（pH = 7）条件下运行。结果表明，中性 pH 下固体的积累略高。对固体样品的傅里叶变换红外（FTIR）分析证实，固体确实是基于钙的脂肪酸盐。然而，固体的脂肪酸谱与下水道系统中 FOG 沉积物中发现的脂肪酸谱不同，主要是饱和脂肪酸。这些结果证实了先前研究人员所做的工作，并提出了不饱和脂肪酸的替代归宿，不会导致它们完全纳入大规模下水道系统中的 FOG 沉积物中。
