Tennessee Wastewater Operator Practice Exam

What occurs when the return sludge rate is too low in an activated sludge process?

1. Insufficient organisms to meet waste load entering the aerator

2. Excessive growth of microorganisms

3. Higher than optimal sludge age

4. Increased effluent color

The correct answer is: Insufficient organisms to meet waste load entering the aerator

In an activated sludge process, the return sludge rate plays a crucial role in maintaining the balance of microorganisms necessary for effective wastewater treatment. When the return sludge rate is too low, not enough microorganisms are returned to the aeration tanks. This leads to insufficient organisms available to meet the waste load entering the aerator. As a result, the treatment process becomes less effective since there aren’t enough active microorganisms to break down the organic material in the wastewater. This situation can result in insufficient biological treatment, elevated levels of pollutants in the effluent, and can lead to operational issues such as the potential for settling problems in the secondary clarifier. The microorganisms, which are essential for the degradation of waste, must be in adequate quantities to ensure that the system can handle the incoming load efficiently. Thus, maintaining an appropriate return sludge rate is critical for optimal operation in an activated sludge system.