Texas Wastewater Class B Practice Exam

What is the recommended depth of sludge drawn to a drying bed?

1. Approximately 5 inches

2. Approximately 12 inches

3. Approximately 9 inches

4. Approximately 15 inches

The correct answer is: Approximately 9 inches

The recommended depth for sludge drawn to a drying bed is approximately 12 inches. This depth is optimal because it allows for effective dewatering of the sludge while also ensuring adequate airflow to promote evaporation of moisture. Sludge at this depth provides a balance, allowing for efficient drainage and minimizing the risk of anaerobic conditions that can occur if the sludge is piled too deep. In drying beds, the moisture content of the sludge is reduced through solar heating and evaporation, and thicker layers can inhibit this process, leading to prolonged drying times and potentially unsatisfactory results. A depth of 12 inches strikes a good balance between drying efficiency and operational practicality, which is why it is recommended.