Tennessee Wastewater Operator Practice Exam

What effect does returning sludge to the beginning of the activated sludge process have?

1. Reduces nutrient concentration

2. Increases concentration of microorganisms in the process

3. Decreases overall system efficiency

4. Increases the retention time of wastewater

The correct answer is: Increases concentration of microorganisms in the process

Returning sludge to the beginning of the activated sludge process serves to increase the concentration of microorganisms, which is fundamental for efficient wastewater treatment. In an activated sludge system, microorganisms play a crucial role in breaking down organic matter in wastewater. By recycling the sludge, which is rich in these active microorganisms, the system can maintain a higher biomass concentration in the treatment basin. This enhanced concentration allows for more effective treatment, as there are more microorganisms available to metabolize the organic pollutants present in the incoming wastewater. Higher concentrations of microorganisms contribute to improved biological processes, resulting in better overall treatment performance, including higher removal rates of biochemical oxygen demand (BOD) and total suspended solids (TSS). This practice is essential to ensure that the activated sludge system operates effectively and meets environmental discharge standards.