Fat, oil and grease deposits in sewers: Characterisation of deposits and formation mechanisms

Efficient Fractionation and Analysis of Fatty Acids and their Salts in Fat, Oil and Grease (FOG) Deposits

“…The relative absence of triglycerides in each FOG deposit studied herein is in contrast with results provided in a recent study of FOG deposits 6 , where FOG deposits were extracted with an 80:20 mixture of hexane/tert.-butyl ether according to APHA 5520B. It is hypothesized that the extracted oil as reported in the study may have contained mainly fatty acids rather than triglycerides.…”

“…These data unambiguously indicate that fatty acids are the major components while fatty acid salts are the minor components in the FOG deposits studies. A recent study provides a correlation between hard water content and increased calcium content in FOG deposits 6 and potentially suggests that correlations should also exist between hard water content and the percentages of FOG deposit fatty acid calcium salts. DCM-soluble fractions that are predominantly comprised of fatty acids are waxy and cohesive solids whereas the DCM-insoluble fractions that are predominantly comprised of fatty acid salts are powdery and non-cohesive solids.…”

Problems, Control, and Treatment of Fat, Oil, and Grease (FOG): A Review

“…It is reported that an increase in the water hardness is associated with higher Ca levels in FOG samples 5 . Another study reported calcium leaching from concrete pipes to be the main source of increased concentrations of Ca in the FOG deposit samples 23 .…”

“…However, based on the evaluations of vitrified clay pipes VCP , which are used in some countries such as Malaysia, it was found that FOG deposition is not due primarily to the presence of calcium, but can be related to other minerals such as sodium and potassium. Moreover, the presence of high amounts of calcium and sodium in FOG deposits indicates that the deposit not only consist of FOG but also of metallic soaps formed during the hydrolysis reaction 5,23,24 . The aforementioned studies focused on the effect of calcium CaCO 3 on the formation of FOG deposits in sewer pipelines.…”

“…For example, the American Environmental Agency EPA estimated that at least 10,350-36,000 sanitary sewer overflows SSOs occur per year in the USA, approximately 47 of which is related to FOG 4 . Similarly, in the UK over 25,000 flooding inci-dents per year are due to sewer blockages, of which, 50 is due to FOG 5 . Moreover, up to 70 of the SSOs that occur in Malaysia are due to FOG.…”