Quantifying fat, oil, and grease deposit formation kinetics.

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Wastewater Treatment

Background:

• Fat, oil, and grease (FOG) deposits in sanitary sewers form calcium-based saponified solids.
• These FOG deposits are a primary cause of sanitary sewer overflows (SSOs) nationwide.
• Understanding FOG deposit kinetics is crucial for preventing SSOs.

Purpose of the Study:

• To determine the kinetics of lab-based saponified solids formation.
• To investigate the influence of fat type, calcium source, pH, and temperature on FOG deposit formation.
• To compare the predictive capabilities of empirical and mechanistic models for saponification.

Main Methods:

• Investigated saponification kinetics using Canola and Beef Tallow fats with calcium chloride and calcium sulfate.
• Conducted experiments under varying pH (7, 10, ≈14) and temperature (22°C, 45°C) conditions.
• Compared experimental data with Cotte saponification, Foubert crystallization, and a mass-action based mechanistic model.

Main Results:

• Fat reactions with calcium ions rapidly formed saponified solids.
• Palmitic fatty acid content, pH, and temperature significantly influenced FOG deposit formation and saponification rates.
• The mass-action based mechanistic model accurately predicted saponified solid formation rates, outperforming empirical models.
• Beef Tallow hydrolysis was slower than Canola fat, yielding less saponified solids.

Conclusions:

• A mass-action based mechanistic model provides a superior framework for understanding and predicting FOG deposit formation in sewers.
• This model's ability to track chemical precursors can inform municipal sewer collection modeling software.
• Accurate prediction of FOG deposit formation can help mitigate sanitary sewer overflows.