Assessment of internal and external grease interceptor performance for removal of food-based fats, oil, and grease from food service establishments

A research study was performed to determine the fats, oil, and grease (FOG) removal efficiency of internal flow-based grease interceptors (FGI). A passive-flow and a mechanical-flow FGI unit were tested and their performance was compared to an external retention-based grease interceptor (RGI). Experiments involved multiple parameters including three oil/water emulsion strengths, two influent liquid temperatures, and two flow rates. Overall, the RGI achieved approximately 80% FOG removal and the FGIs removed less than 50% under the tested conditions. One exception occurred during the passive FGI testing during which removal reached approximately 80%. This increased efficiency was likely due to the relatively weak emulsion exhibiting significantly large FOG globules. The FOG removal efficiency decreased with increased temperature because of increased breakage of FOG globules at the elevated temperature. These results suggest that emulsion strength significantly affects FOG removal efficiency of FGIs and should be considered in future manufacturer testing protocol.