Texas Wastewater Class B Practice Exam

Which types of trickling filters are the most common?

1. Standard rate and High Rate

2. Low Rate and Standard Rate

3. High Rate and Rapid Rate

4. Slow Rate and Moderate Rate

The correct answer is: Standard rate and High Rate

The most common types of trickling filters are indeed standard rate and high rate. These classifications are primarily based on the hydraulic loading rates and the design specifications that determine their operational efficiency in treating wastewater. Standard rate trickling filters are typically designed to handle a moderate flow of wastewater and are characterized by their thick biofilm formation on the filter media. This setup facilitates effective biological treatment as microorganisms break down organic matter. They often operate at a loading rate of 0.1 to 0.5 gpd/ft². High rate trickling filters, on the other hand, are engineered to accommodate higher flow rates while maintaining efficient biological treatment. These filters have a smaller media spacing and a more aggressive design, allowing them to achieve higher treatment efficiencies per square foot of surface area. They can handle loading rates exceeding 0.5 gpd/ft². The other types mentioned—such as low rate, rapid rate, slow rate, and moderate rate—are less commonly referenced or utilized in modern design and operation of trickling filters. These designations may refer to variations that do not fit the widely accepted classifications of standard and high rate, which are more prevalent in treatment plants today.