Wastewater Treatment Operator Certification Practice Test

What should be mostly found in healthy activated sludge?

1. Tiny flagellates

2. Amoeboids

3. Short Filaments

4. Free swimmers and stalked ciliates

The correct answer is: Free swimmers and stalked ciliates

Healthy activated sludge is characterized by a diverse and balanced microbial community that plays a crucial role in the wastewater treatment process. When evaluating the components of activated sludge, the presence of free swimmers and stalked ciliates is particularly significant. Free swimmers, such as certain types of ciliates, indicate a healthy and well-functioning biological treatment process. They move freely within the mixed liquor, consuming bacteria and organic matter, which helps in maintaining clarity in the treated effluent. Stalked ciliates, on the other hand, attach to surfaces and provide stability to the microbial community. Their presence signifies a balanced ecosystem where microbial growth is supported, allowing for effective aggregation and floc formation. Together, these organisms contribute to the overall efficiency of the activated sludge process by enhancing the breakdown of organic material and facilitating the settling of sludge during the clarification phase. This balance helps prevent issues that may arise from an overabundance of other microorganisms such as filaments or flagellates, which can lead to operational problems like bulking or foaming. Thus, the presence of free swimmers and stalked ciliates is an indicator of a robust and effective activated sludge system.