Tennessee Wastewater Operator Practice Exam

What is the result of sludge bulking in an activated sludge process?

1. Improved settling abilities

2. Increased effluent turbidity

3. Enhanced anaerobic digestion

4. Reduced BOD removal efficiency

The correct answer is: Increased effluent turbidity

Sludge bulking in an activated sludge process primarily leads to increased effluent turbidity. This occurs because bulking refers to the aggregation of microorganisms that do not settle properly, leading to a larger portion of suspended solids being carried over into the treated effluent. In a healthy activated sludge system, microorganisms, or floc, should settle effectively during the sedimentation process; when bulking happens, these solids tend to stay in suspension, which results in cloudiness or turbidity in the output water. While sludge bulking can occasionally lead to changes such as enhanced anaerobic digestion or even affect aspects like BOD removal efficiency, the direct and most noticeable consequence remains the increased turbidity in the effluent. Other processes, such as anaerobic digestion, can be affected but are not an immediate result of the bulking issue itself. Similarly, while bulking can impact overall treatment effectiveness, the most visible consequence when monitoring effluent quality is indeed the increased turbidity.