Modeling fats, oil and grease deposit formation and accumulation in sewer collection systems

Abstract

Fats, oil and grease (FOG) deposits in sewer systems are responsible for approximately 25% of all annual line blockages in the United States and lead to the release of 3–10 million gallons of untreated wastewater to the surrounding environment. Considerable effort has been made to maintain the conveyance of wastewater by cleaning pipes that have a significant FOG deposit accumulation. Changes in the urban landscape from the addition or deletion of food service establishments (FSEs), however, may pose challenges in determining the location of these high accumulation zones. This research focuses on the development of a sewer collection system model that predicts high FOG deposit accumulation zones. Two collection systems were simulated to test the prediction capabilities of the tool and to assess how changes in the urban landscape affect the location of these accumulation zones. The numerical tool incorporates a mechanistic-based FOG deposit formation kinetic model. Results showed that the model predicts about 65% of the reported high FOG deposit accumulating zones. Simulations also showed significant changes in the location of these high FOG deposit accumulating zones from changes in the number and locations of FSEs and from FSE discharge and background wastewater flow variations.