Hydrolysis of Lipids in Wastewater

Colloidal and supracolloidal lipid materials (grease) constitute an abundant, high-energy food source in biological wastewater treatment processes. Biochemical oxidation of these materials is preceded by enzymatic hydrolysis. The effect of the rate of hydrolysis on the rate of removal of lipids is subject to questions, and the removal mechanisms of these materials in secondary sewage treatment processes are not well understood. This study was made to determine the role of hydrolysis in the removal of lipids in domestic wastewater. Hydrolysis was observed not to be a rate-limiting reaction in the removal of lipids for microorganisms present in primary clarifier effluent from a sewage treatment plant. When these organisms were subjected to periodic substrate limiting growth situations in a batch fill-and-draw unit, they were temporarily unable to remove approximately 35% to 40% of the unhydrolyzed lipid initially added. This remaining percentage is believed to have been a β-monoglyceride.