Florida Wastewater Practice Test

Which type of pond is commonly used after a trickling filter or RBC plant?

1. Settling pond

2. Facultative pond

3. Polishing pond

4. Aerobic lagoon

The correct answer is: Polishing pond

A polishing pond is typically used after a trickling filter or a rotating biological contactor (RBC) plant to further enhance the quality of effluent before it is discharged, particularly by removing any residual suspended solids and nutrients. The function of a polishing pond is to provide additional treatment for the wastewater, allowing for further biological activity to occur, particularly through the action of algae and other aquatic plants. This assists in reducing remaining contaminants and can help improve the clarity and quality of the effluent. These ponds are designed to be relatively shallow and have sufficient light penetration to support photosynthesis, which plays a crucial role in the treatment process. In contrast, settling ponds primarily focus on the sedimentation of solids and are not necessarily equipped to handle the additional biological treatment that polishing ponds provide. Facultative ponds may serve dual purposes but are generally designed for both aerobic and anaerobic treatment, which may not be as effective specifically for final polishing. Aerobic lagoons can also treat wastewater, yet they emphasize aeration and are often used for primary treatment rather than supplementary treatment after mechanical processes like trickling filters or RBC plants.