Why is grease removal from wastewater more difficult when the pH is below seven?

The difficulty of grease removal from wastewater at a pH below seven is largely due to the properties of grease and fats in relation to the acidity of the solution. At lower pH levels, fatty acids that emerge from grease tend to remain in a soluble state rather than breaking down or separating from the wastewater.

When pH is neutral or alkaline, grease and fats can hydrolyze and break down into smaller, less soluble molecules, which allows for easier removal. However, under acidic conditions (pH < 7), these fatty acids may not convert into the solid forms that can settle out effectively, leading to higher levels of grease remaining suspended in the water. This decreased ability to separate from water makes it challenging to remove grease using physical means, such as flotation or sedimentation.

Understanding the chemical behavior of various substances in relation to pH is crucial for effective wastewater treatment, highlighting why managing pH levels is essential in processes involving grease removal.