Texas Wastewater Class B Practice Exam

What could indicate that the sludge is being wasted excessively in an activated sludge process?

1. High levels of dissolved oxygen

2. Decrease in effluent quality

3. Thick foam in the aeration tank

4. Decrease in temperature of the tank

The correct answer is: Decrease in effluent quality

A decrease in effluent quality is a key indicator that excessive sludge wasting is occurring in an activated sludge process. When sludge is wasted in excess, there is typically not enough biomass remaining in the system to effectively metabolize pollutants in the incoming wastewater. This can lead to insufficient treatment and consequently results in a decline in the quality of the effluent. Indicators of poor effluent quality may include elevated levels of biochemical oxygen demand (BOD), total suspended solids (TSS), or other contaminants that have not been adequately removed. In contrast, high levels of dissolved oxygen are usually a sign that the aeration process is working effectively, as the microorganisms require oxygen to break down organic matter. Thick foam in the aeration tank can suggest other issues, such as filamentous bacteria growth, rather than excessive sludge wasting. A decrease in temperature might indicate environmental changes but does not directly correlate with sludge wasting.