Basic Wastewater Operator Practice Exam

What action can be taken to speed up a slow-moving trickling filter arm?

1. Add more orifices on the distribution arms

2. Close orifices on the distribution arms

3. Decrease recirculation

4. Increase recirculation

The correct answer is: Increase recirculation

To address the issue of a slow-moving trickling filter arm, one effective action is to increase recirculation. Recirculation is critical in trickling filter operations as it helps maintain proper flow rates, ensures even distribution of wastewater over the filter media, and enhances the contact between the wastewater and the microbial biofilm present on the media. When recirculation is increased, it helps to create a higher flow rate, which can prevent the distribution arms from becoming stagnant. This action is particularly beneficial because it can help to eliminate any areas where the flow may be too low, leading to better overall performance of the trickling filter. Increasing the recirculation can help to optimize the treatment process and ensure that the biofilm is adequately nourished with the incoming wastewater. The other options would not effectively address the slow-moving condition of the arms. For instance, adding more orifices on the distribution arms could lead to uneven flow and possibly exacerbate the distribution problem. Closing orifices would restrict flow even further, worsening the situation. Conversely, decreasing recirculation would also reduce flow rates, which is counterproductive for resolving sluggish movement of the trickling filter arms and could lead to ineffective treatment.