Wastewater Treatment Operator Certification Practice Test

How can the efficiency of a trickling filter be improved?

1. Raise the distributor arm

2. Reduce the size of the ventilation ports

3. Decrease the amount of the filter media

4. Add recirculation

The correct answer is: Add recirculation

Adding recirculation can significantly improve the efficiency of a trickling filter by enhancing the contact time between the wastewater and the filter media. In a trickling filter, wastewater is distributed over media that supports the growth of microorganisms responsible for treating the wastewater through biological processes. By recirculating a part of the treated effluent back to the influent, it increases the flow rate of water through the filter and provides additional nutrients and microorganisms to the new incoming wastewater. This practice helps in maintaining optimal moisture levels and promotes a more robust biological film on the filter media, ultimately leading to improved treatment performance and higher removal rates of organic matter and pollutants. In contrast, raising the distributor arm can lead to uneven distribution of wastewater over the media, which might reduce the efficiency. Reducing the size of the ventilation ports could restrict airflow, affecting the aerobic conditions necessary for effective treatment. Decreasing the amount of filter media would limit the surface area available for the microorganisms to grow, resulting in less biological treatment capacity. Thus, implementing recirculation is a strategic approach to optimize the trickling filter's performance.