Florida Wastewater Practice Test

What is a primary reason for chlorinating a RAS line?

1. Enhance oxygen levels

2. Control filamentous bacteria

3. Reduce odor

4. Improve nutrient uptake

The correct answer is: Control filamentous bacteria

Chlorinating the Return Activated Sludge (RAS) line primarily serves to control filamentous bacteria. In wastewater treatment systems, filamentous bacteria can proliferate excessively, leading to issues such as poor settling characteristics in the clarification process. This can result in sludge bulking, where the sludge does not settle effectively, causing operational challenges and reduced treatment efficiency. By chlorinating the RAS, the chlorination process selectively targets and reduces the population of these filamentous species, helping to restore balanced microbial communities and improve the settling properties of the sludge. This practice is crucial in maintaining the overall health of the biological treatment process, ensuring efficient removal of organic material and effective solid-liquid separation in downstream processes. While other methods may address different aspects of wastewater treatment, chlorination specifically targets the issue of filamentous growth, making it an important management tool in RAS line maintenance.