California Wastewater Treatment Operator Practice Exam

A pond with a detention time of less than three days will perform similar to?

1. trickling filter

2. activated sludge process

3. sedimentation tank

4. sludge drying bed

The correct answer is: sedimentation tank

The correct answer is that a pond with a detention time of less than three days will perform similar to a sedimentation tank. This is because both systems rely on gravity to allow solids to settle out of the water. In a sedimentation tank, wastewater is held for a short duration, allowing heavier particles to drop to the bottom, forming sludge, while the treated water rises to the surface. Similarly, a pond with short detention time typically will not allow enough time for adequate biological treatment to occur, and thus primarily facilitates sedimentation of suspended solids. In contrast, other options such as trickling filters and activated sludge processes are designed for biological treatment and require longer detention times to effectively promote the breakdown of organic materials by microorganisms. Sludge drying beds also serve a different purpose, focusing on dewatering and drying of sludge rather than treating incoming wastewater directly. Therefore, when considering the operational dynamics, the sediments and settling characteristics align more closely with those of a sedimentation tank under the given conditions.