Tennessee Wastewater Operator Practice Exam

To prevent the growth of the filament Sphaerotilus Nathan's, what should be done regarding SRT?

1. Keep it below about 5 days

2. Keep it below about 7 days

3. Keep it below about 9 days

4. No limit required

The correct answer is: Keep it below about 9 days

To effectively manage and prevent the growth of the filamentous organism Sphaerotilus, it is crucial to maintain the sludge retention time (SRT) at a specific threshold. Research and practical experience indicate that keeping the SRT below approximately 9 days helps to control the proliferation of Sphaerotilus. This limitation on SRT ensures that the conditions in the treatment system are less favorable for the growth of filamentous organisms while promoting the dominance of floc-forming bacteria, which are beneficial in wastewater treatment processes. When SRT is too long, it can favor the growth of filamentous bacteria, including Sphaerotilus, leading to issues like poor settling characteristics, resulting in effluent quality problems and operational challenges. Therefore, effectively managing and limiting the SRT to below this threshold is critical for maintaining a healthy microbial population that supports proper wastewater treatment.