Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC 27695, United States.
Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, NC 27695, United States.
Water Res. 2014 Feb 1;49:92-102. doi: 10.1016/j.watres.2013.11.012. Epub 2013 Nov 21.
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.
了解下水道系统中脂肪、油和油脂（FOG）沉积物的形成对于下水道收集系统的可持续性至关重要，因为它们被认为是导致下水道堵塞的原因，进而导致卫生下水道溢流（SSO）。最近，由于皂化反应，下水道系统中的 FOG 沉积物与基于钙的脂肪酸盐表现出很强的相似性。本研究的目的是量化可能影响 FOG 沉积物形成及其化学和流变性质的因素。这些因素包括 FSE 中使用的脂肪类型、环境条件（即 pH 值和温度）以及下水道系统中钙的来源。研究结果表明，钙基盐中的钙含量似乎取决于钙源的溶解度极限，并受 pH 值和温度条件的影响。在碱性驱动水解下产生的钙基脂肪酸盐的脂肪酸谱与脂肪源的谱相同，与现场 FOG 沉积物的谱不匹配，现场 FOG 沉积物显示出高比例的长链饱和脂肪酸棕榈酸。据推测，脂肪的选择性微生物代谢和/或生物诱导的加氢可能导致下水道系统中 FOG 沉积物的组成。因此，在将 FSE 废物排放到下水道收集系统之前，可能需要在预处理过程中选择性地去除棕榈酸。
