Ponds used in series after a trickling filter are sometimes referred to as what?

Ponds used in series after a trickling filter are referred to as polishing ponds because they serve the purpose of improving water quality by further treating the effluent coming from the trickling filter. This secondary treatment step is essential in removing remaining solids, nutrients, and pathogens, thereby enhancing the overall clarity and quality of the water before it is released into the environment or subjected to additional treatment processes.

Polishing ponds allow for additional biological processes and sedimentation to occur, which helps to remove impurities from the wastewater. The time spent in these ponds enables natural processes to take place, such as the action of sunlight and microbial activity, which can degrade organic matter and help disinfect the effluent.

In contrast, retention ponds are primarily designed for stormwater management, settling ponds are focused on separating solids from liquids through sedimentation, and infiltration ponds allow water to percolate into the ground but are not specifically designed for polishing wastewater treatment.