Tennessee Wastewater Operator Practice Exam

Decanting can effectively increase the TS concentration in a digester to about _______ without chemical addition?

1. 1.0%

2. 1.5%

3. 2.0%

4. 2.5%

The correct answer is: 2.0%

Decanting is a process used in wastewater treatment, particularly in anaerobic digestion, where the liquid portion of the digester is removed to concentrate the solids. This technique allows operators to manage the total solids (TS) concentration within the digester more effectively. When decanting is performed, the goal is to minimize the volume of liquid and maximize the concentration of solids remaining in the digester. It is known that decanting can increase the TS concentration up to approximately 2.0% without the need for chemical additives. This concentration level is significant because it ensures that the microorganisms in the digester have enough solids to effectively break down organic matter, while avoiding the complications that can arise from having too high or too low of a concentration. Beyond this concentration, the digesting environment may start to shift, potentially creating inefficiencies in the anaerobic digestion process. Therefore, the knowledge that decanting can raise TS concentrations effectively to about 2.0% is crucial for operators managing digester performance.